Edecio Cunha-Neto, Jorge Kalil
A u to im m u n ity in C h a g a s' h e a rt d ise a se
I m m unol ogy Labor at or y of Tr ans pl ant at i on, H e ar t I ns i t ut e , H os pi t al das C l f ni c as ,Fac ul dade de M e di c i na da U ni v e r s i dade de S i l o P aul o - S i l o P aul o, B r az i l
T h e tim e sca le d isso cia tio n b e tw e e n h ig h p a ra site m ia a n d tissu e p a th o lo g y, a llie d to th e a b se n ce o f p a ra site s in th e h e a rt le sio n s o f ch ro n ic C h a g a s' d ise a se ca rd io p a th y, ca ste d d o u b t o n th e d ire ct p a rticip a tio n o f Trypanosoma cruziin tissu e le sio n s. M o re o ve r,
th e h e a rt tissu e le sio n s in ch ro n ic C h a g a s' d ise a se ca rd io p a th y a re a sso cia te d to a n in fla m m a to ry m o n o n u cle a r ce ll in filtra te , p re su m a b ly th e u ltim a te e ffe cto rs o f tissu e d a m a g e . It h a s b e e n h yp o th e size d th a t th e in fla m m a to ry ce ll in filtra te co u ld m e d ia te a
d e la ye d h yp e rse n sitivity p ro ce ss d ire cte d to th e h e a rt tissu e co m p o n e n ts, a n a u to im m u n e re sp o n se trig g e re d b y im m u n o lo g ica l cro ss-re a ctivity in th e co u rse o f a p ro te ctive im m u n e re sp o n se a g a in st so m e Tcruzi a n tig e n h o m o lo g o u s to h e a rt p ro te in s. H o w e ve r, little is kn o w n a b o u t th e e fe cto r ro le o f th e T ce lls in th e in filtra te , o r a b o u t th e n a tu re o f th e a n tig e n th a t le a d to th e ir a ccu m u la tio n in tissu e . In th is p a p e r, w e w ill re vie w th e p u b lish e d e vid e n ce o n a u to im m u n ity a n d im m u n o lo g ica l cro ss-re a ctivity b e tw e e n T cruzia n d th e m a m m a lia n h o st, a lo n g w ith d a ta g e n e ra te d in o u r la b o ra to ry. T h e d e fin itio n o f th e p re cise ro le p la ye d b y a u to im m u n ity in th e p a th o g e n e sis o f C h a g a s' d ise a se ca rd io p a th y m a y h a ve im p o rta n t co n se q u e n ce s b o th fo r im m u n o p ro p h yla xis
a n d fo r th e th e ra p e u tic a p p ro a ch o f ch ro n ic C h a g a s' d ise a se .
U N IT E R M S : C h a g a s' d ise a se . A u to im m u n ity.
IN T R O D U C T IO N
A
lth o u g ha u to im m u n em a n y p h e n o m e n as tu d ie s s u g g e s tin c h ro n icth e e x is te n c eC h a g a s 'o f d is e a s e c a rd io m y o p a th y (C C C ), th e a c tu a lp a th o g e n e tic ro le p la y e d b y a u to im m u n ity is s till la rg e ly
Address for correspondence:
Laborat6rio de Imunologia de Transplantes
Instituto do Cora9ao, Hospital das Clfnicas da Faculdade
de Medicina da Universidade de Sao Paulo
Av. Dr. Eneas de Carvalho Aguiar, 500 39. andar Sao Paulo - SP - Brasil - CEP 05403-000
u n k n o w n . T h e h e a rt le s io n s th a t a re h a llm a rk o f c h ro n ic
C h a g a s ' d is e a s e o c c u r d e c a d e s a fte r th e in itia l in fe c tio n
e p is o d e , in a s u b s e t (c a . 3 0 % ) o f in fe c te d in d iv id u a ls . T h e
le s io n s a re a s s o c ia te d to a d iffu s e ly m p h o c y tic in filtra te ,
p re s u m a b ly th e u ltim a te m e d ia to r o f tis s u e d a m a g e . T h e
s c a rc ity o f p a ra s ite s in d a m a g e d a re a s - a fin d in g
in c o m p a tib le w ith th e n o tio n th a t h e a rt le s io n s re s u lt fro m
h y p e rs e n s itiv ity to p a ra s ite a n tig e n s - p ro m p te d e a rly
in v e s tig a to rs to s u g g e s t th a t th e in fla m m a to ry h e a rt le s io n
c o u ld b e o f " a u to -a lle rg ic " , o r a u to im m u n e , n a tu re .
A c c o rd in g to s u c h a n a u to im m u n ity /a n tig e n ic m im ic ry
h y p o th e s is , ly m p h o c y te s in th e h e a rt s h o u ld re c o g n iz e a n d
m o u n t d e la y e d -ty p e h y p e rs e n s itiv ity re s p o n s e s to w a rd s a
tis s u e -s p e c ific h e a rt c o m p o n e n t b e a rin g s tru c tu ra l
s im ila ritie s to a g iv e n T . c r uz i a n tig e n . H o w e v e r, little is
k n o w n a b o u t th e e ffe c to r ro le o f tis s u e -in filtra tin g T c e lls ,
o r a b o u t th e a n tig e n trig g e rin g th e ir a c c u m u la tio n in h e a rt.
tissu e . In th is p a p e r, w e w ill re v ie w th e lite ra tu re o n
a u to im m u n ity a n d a n tig e n ic m im ic ry /im m m u n o lo g ic
c ro ss-re a c tio n s b e tw e e n
Trypanosoma
cruzi
a n d h o st tissu e in C h a g a s' d ise a se , a p a rt fro m d isc u ssin g d a ta o b ta in e d ino u r o w n la b o ra to ry . T h e d e fin itio n o f th e p a th o g e n e tic ro le
o f a u to im m u n ity m a y h a v e im p o rta n t im p lic a tio n s in
im m u n o p ro p h y la tic a n d im m u n o m o d u la to ry th e ra p e u tic a l
a p p ro a c h e s in C C C .
C U R R E N T C O N C E P T S I N A U T O I M M U N I T Y
H u m o ra l o r c e llu la r im m u n e re sp o n se s to a g iv e n
p ro te in a n tig e n in m o st c a se s d e p e n d o n th e in itia l
re c o g n itio n o f th e a n tig e n in q u e stio n b y C D 4 + T
ly m p h o c y te s. T c e lls o n ly re c o g n iz e a n tig e n w h e n it is
p h y sic a lly a sso c ia te d to th e m e m b ra n e o f a m a c ro p h a g e
o r a B c e ll. T h e se c e lls b re a k o r " p ro c e ss" th e a n tig e n
m o le c u le in to sm a lle r fra g m e n ts o r p e p tid e s, w h ic h a re
p la c e d in sid e a " g ro o v e " a t th e o u te r p a rt o f a n H L A c la ss
II m o le c u le (e .g . H L A -D R , -D Q , -D P ). T h e a n tig e n ic
p e p tid e -H L A m o le c u le c o m p le x is e x p o rte d to th e c e ll
m e m b ra n e , w h e re it c a n in te ra c t w ith th e a n tig e n re c e p to r
o f a n a n tig e n -sp e c ific T c e ll. E a c h T c e ll is c a p a b le o f
re c o g n iz in g o n ly a sin g le a n tig e n ic fra g m e n t, o r e p ito p e ,
fro m a sin g le p ro te in , v ia its u n iq u e a n tig e n re c e p to r. T h is
re c e p to r b in d s to th e H L A -e p ito p e c o m p le x v ia its v a ria b le
re g io n , v e ry m u c h lik e im m u n o g lo b u lin s in te ra c t w ith
a n tig e n s. T h e re c o g n itio n o f its sp e c ific e p ito p e le a d s th e
C D 4 + T c e ll in to a c tiv a tio n , w ith p ro d u c tio n a n d se c re tio n
o f m u ltip le ly m p h o k in e s a n d in te rle u k in s - im m u n o lo g ic a l
m e d ia to rs a b le to m o b iliz e a n d c o n tro l o th e r ty p e s o f c e lls
in v o lv e d in th e im m u n e re sp o n se . D e p e n d in g u p o n th e
ly m p h o k in e s p ro d u c e d , th e su b se q u e n t im m u n e re sp o n se
m a y sp e c ia liz e in to th e h u m o ra l o r c e llu la r a rm s.
E a c h in d iv id u a l re c o g n iz e s d istin c t re g io n s (e p ito p e s)
o f a g iv e n a n tig e n m o le c u le . T h is is so b e c a u se H L A
m o le c u le s, w h ic h b in d th e a n tig e n ic p e p tid e s, v a ry a m o n g
in d iv id u a ls - a n d p re c ise ly in th e re g io n s lin in g th e
a n tig e n ic p e p tid e -b in d in g " g ro o v e " , re su ltin g in th e
p re se n ta tio n o f d istin c t H L A -re la te d re p e rto ire s o f d isc re te
e p ito p e s to th e im m u n e sy ste m . T h u s, d iffe re n t in d iv id u a ls
m a y o r m a y n o t re c o g n iz e a g iv e n e p ito p e , a n d th is.
d iffe re n c e is o fte n g e n e tic a lly d e te rm in e d b y th e H L A .
A s th e re a re u p to 1 0 0 d iffe re n t a lle le s fo r so m e H L A
lo c i, th is im p lie s a w id e d iv e rsity o f re c o g n itio n re p e rto ire s
in th e p o p u la tio n .
T h e sp e c ific ity o f th e im m u n e re sp o n se m a y a llo w
a n a tta c k to in fe c tio u s a g e n ts, fo r in sta n c e , w ith o u t
d a m a g in g th e h o st's o w n tissu e - th e so -c a lle d se lf-n o n se lf
d isc rim in a tio n w h e re u p o n th e im m u n e sy ste m is " to le ra n t"
to th e c o m p o n e n ts o f th e o rg a n ism it b e lo n g s to (se lf
c o m p o n e n ts). T h e re a re situ a tio n s, h o w e v e r, w h e n th e
to le ra n c e sta tu s to w a rd s a g iv e n se lf c o m p o n e n t is b ro k e n ;
it fo llo w s th a t th e im m u n e sy ste m re c o g n iz e s a n d m a y
d e stro y se lf tissu e s c o n ta in in g th a t c o m p o n e n t. In th e
o rg a n -sp e c ific a u to im m u n e d ise a se s, th e ta rg e t se lf-a n tig e n
o r ta rg e t e p ito p e o n ly o c c u rs in a sin g le o rg a n , le a d in g to
a n o rg a n -sp e c ific le sio n . E x a m p le s o f su c h a situ a tio n a re
th e a u to im m u n e th y ro id d ise a se s (G ra v e s' /H a sh im o to ),
m u ltip le sc le ro sis a n d in su lin -d e p e n d e n t d ia b e te s m e llitu s,
a m o n g o th e rs. T h e trig g e rin g m e c h a n ism s o f a u to im m u n e
d ise a se s a re still la rg e ly u n k n o w n , b u t a lw a y s in v o lv e th e
lo ss o f c o n tro l o f se lf-re c o g n iz in g , p o te n tia lly
a u to a g g re ssiv e B o r T c e lls, w h ic h is m a n y tim e s se c o n d a ry
to p o ly c lo n a l a c tiv a tio n o r a n tig e n ic m im ic ry (stru c tu ra l
sim ila rity b e tw e e n fo re ig n a n d se lf a n tig e n s).
E n v iro n m e n ta l (e .g . in fe c tio n s) a s w e ll a s g e n e tic (fa m ilia l
o c c u rre n c e , H L A a sso c ia tio n ) fa c to rs a re k n o w n to
in te rp la y .
F a c in g th e b io lo g ic a l ro le p la y e d b y H L A m o le c u le s
in th e g e n e tic c o n tro l o f im m u n e re sp o n se s to d e fin e d
a n tig e n s, th e a sso c ia tio n o f m o st a u to im m u n e d ise a se s w ith
a lle le s o f th e H L A sy ste m su g g e st th a t so m e H L A a lle le s
fa v o r th e re c o g n itio n o f se lf-e p ito p e s. T h e p re se n ta tio n o f
a se lf e p ito p e b y a g iv e n H L A m o le c u le a llo w s th e
re c o g n itio n b y e p ito p e -sp e c ific T c e lls, th e n e c e ssa ry
c o n d itio n s fo r a n a u to im m u n e re sp o n se . T h e p re c ise
id e n tific a tio n o f ta rg e t e p ito p e s in a n a u to im m u n e d ise a se
is o f fo re m o st im p o rta n c e fo r th e u n d e rsta n d in g o f
p a th o g e n e sis, a n d m a y a llo w fo r sp e c ific im m u n e
in te rv e n tio n a im in g a t c o n tro llin g tissu e d a m a g e .
E V I D E N C E F O R A U T O I M M U N I T Y I N C H A G A S ' D I S E A S E
E v e r sin c e 1 9 3 0 , T o rre s o b se rv e d a n in te n se
in fla m m a to ry in filtra te c o n sistin g o f ly m p h o c y te s,
m o n o n u c le a r c e lls, p la sm a c e lls, h istio c y te s a n d
g ra n u lo m a ta in h e a rt tissu e , in th e a b se n c e o f p a ra site n e sts,
in n e c ro p sy stu d ie s o f p a tie n ts w h o d ie d o f C C C (3 5 ). In
th e first e x p e rim e n ta l re p o rt su g g e stin g th e in v o lv e m e n t
o f im m u n o lo g ic a l fa c to rs in th e p a th o g e n e sis o f C C C ,
M u n iz & A z e v e d o in d u c e d in fla m m a to ry le sio n s in th e
m y o c a rd iu m o f
rhesus
m o n k e y s a fte r in o c u la tio n w ithT.
cruzi
h o m o g e n a te s, th u s p o stu la tin g th e p a rtic ip a tio n o fd e la y e d -ty p e h y p e rse n sitiv ity to
T. cruzi
c o m p o n e n ts in th ep a th o g e n e sis o f C C C (2 0 ). In a h isto p a th o lo g ic a l m a p p in g
stu d y o f th e w h o le h e a rt w ith se ria l se c tio n s,
T. cruzi
w a sid e n tifie d in o n ly ,2 0 % o f th e h e a rts stu d ie d (1 6 ), a n
e v id e n c e w h ic h w a s in lin e w ith th e p io n e e rin g o b se rv a tio n
o f T o rre s th a t th e h e a rt le sio n a n d in fla m m a to ry in filtra te
h a d n o c o rre la tio n w ith th e p re se n c e o f th e p a ra site . T h e
h isto p a th o lo g ic a l p ic tu re , a llie d to th e a v a ila b le
e x p e rim e n ta l e v id e n c e , le d se v e ra l a u th o rs to p o stu la te th a t
h e a rt tissu e d a m a g e in C C C c o u ld b e d u e to " a u to -a lle rg ic
m e c h a n ism s o f d e la y e d h y p e rse n sitiv ity to w a rd s
m y o c a rd ia l c o m p o n e n ts" (2 ), n o w k n o w n a s a u to im m u n e
m e c h a n ism s. It w a s th e n h y p o th e siz e d th a t th e b re a k d o w n
o f im m u n o lo g ic a l to le ra n c e w ith h e a rt tissu e d a m a g e c o u ld
b e se c o n d a ry to a n o rig in a lly p ro te c tiv e re sp o n se d ire c te d
to a g iv e n
T. cruzi
a n tig e n b e a rin g stru c tu ra l sim ila ritie sto a a tissu e -sp e c ific h e a rt c o m p o n e n t. A lo n g th e fo llo w in g
y e a rs, th e a u to im m u n ity /a n tig e n ic m im ic ry h y p o th e sis w a s
e x p e rim e n ta lly a p p ro a c h e d b y m a n y in v e stig a to rs.
A s a c o ro lla ry o f th e th e o ry o f a u to im m u n e
p a th o g e n e sis o f C C C , se v e ra l stu d ie s c o m p a re d th e le sio n s
o f C C C w ith " e x p e rim e n ta l a lle rg ic m y o c a rd itis" in d u c e d
b y im m u n iz a tio n w ith c a rd ia c tissu e h o m o g e n a te . T h is w a s
re p e a te d b y K o z m a e t a I., in rh e su s m o n k e y s (1 7 ), a n d b y
C o ssio e t a I. in m ic e (7 ). T h e y b o th o b se rv e d h e a rt le sio n s
in im m u n iz e d a n im a ls sim ila r to e x p e rim e n ta l
T. crud
in fe c tio n . C h a m b o e t a I. id e n tifie d a n ti-T .
cruzi
a n tib o d ie sin m ic e w ith e x p e rim e n ta l a u to im m u n e m y o c a rd itis
in d u c e d b y im m u n iz a tio n w ith h e a rt h o m o g e n a te (5 ).
S tu d ie s o n th e se n sitiz a tio n o f p e rip h e ra l b lo o d
m o n o n u c le a r c e lls (P B M C ) fro m C C C p a tie n ts to c a rd ia c
a n tig e n s m e t c o n tra d ic to ry re su lts. C a rd ia c a n tig e n s in d u c e d
Iy m p h o k in e (M IF ) p ro d u c tio n , a n d n o n -in fe c te d
c a rd io m y o c y te s w e re ta rg e ts o f c y to to x ic ity b y C C C P B M C
(1 1 ,3 2 ). H o w e v e r, c a rd ia c h o m o g e n a te d id n o t e lic it
p ro life ra tiv e re sp o n se s a m o n g C C C p e rip h e ra l b lo o d T c e lls
(3 4 ). T h e a b se n c e o f p ro life ra tiv e re sp o n se s o f T c e lls to
c a rd ia c tissu e a n tig e n s p u t th e th e o ry o f a u to im m u n e
p a th o g e n e sis o f C C C u n d e r se v e re c ritic ism (1 5 ).
A lo n g th e 7 0 's a n d 8 0 's, th e re h a v e b e e n se v e ra l
re p o rts o f im m u n o lo g ic a l c ro ss-re a c tiv ity /a n tig e n ic
m im ic ry b e tw e e n m o re o r le ss d e fin e d
T.
cruzi
a n d h o st a n tig e n s. C o ssio e t a I. d e sc rib e d a n tib o d ie s p re se n t in th ese ru m o f C C C p a tie n ts, c a p a b le o f b in d in g to v a sc u la r
e n d o th e liu m a n d in te rstitiu m in m ic e , th e so -c a lle d E V !
a n tib o d ie s (8 ). L a te r, th e se a n tib o d ie s w e re d e m o n stra te d
n o t to re c o g n iz e o u m a n c a rd ia c tissu e , a n d th e in itia l
fin d in g s o f c o rre la tio n w ith c a rd ia c sy m p to m s w e re n o t
re p ro d u c ib le (1 4 ).
S a n to s-B u c h e t a I. d e sc rib e d a n ti-sa rc o le m m a
a n tib o d ie s c ro ss-re a c tin g w ith
T. cruzi
m e m b ra n e s in se rafro m p a tie n ts w ith se v e re C C C (2 8 ). H o w e v e r, p a tie n ts
w ith D re ssle r's sy n d ro m e o r D u c h e n n e 's m u sc u la r
d y stro p h y - d ise a se s w h e re th e re is n o n sp e c ific d e stru c tio n
o f h e a rt tissu e - a lso p re se n te d su c h a n tib o d ie s, su g g e stin g
th e y w e re se c o n d a ry to h e a rt d e stru c tio n a n d p ro b a b ly
p la y e d little ro le in p a th o g e n e sis. T h e im m u n iz a tio n o f
m ic e w ith sa rc o le m m a l a n tig e n s in d u c e d m y o c a rd itis, b u t
m e th o d o lo g ic a l p ro b le m s c o n fu se d th e in te rp re ta tio n o f
su c h a fin d in g (1 ).
L e v in e t a I. re p o rte d th a t se ra fro m C C C p a tie n ts
p o sse sse d a n tib o d ie s a g a in st a n e p ito p e o f
T. cruzi
rib o so m a l P p ro te in w h ic h is v e ry sim ila r to th e
c o rre sp o n d in g re g io n o f m a m m a lia n rib o so m a l P p ro te in
(1 8 ). H o w e v e r, a s rib o so m a l p ro te in s a re p re se n t in a ll
c e ll ty p e s, th e y a re u n lik e ly ta rg e ts fo r a h e a rt-sp e c ific
a u to im m u n e a tta c k . L a te r it w a s fo u n d th a t a n tib o d ie s
a g a in st
T. cruzi
rib o so m a l p ro te in d o n o t c ro ssre a c t w ithth e c o rre sp o n d in g h u m a n p ro te in . B o n fa e t a I. d e sc rib e d
a n tig e n ic m im ic ry b e tw e e n a 2 3 k D a rib o so m a l p ro te in
a n d a c o rre sp o n d in g m a m m a lia n p ro te in in c a . 3 0 % o f
c h ro n ic C h a g a s'd ise a se p a tie n ts in d e p e n d e n t o f c lin ic a l
p re se n ta tio n (4 ).
S e a rc h in g fo r stru c tu ra l su b tra te s fo r th e h y p o th e sis
th a t th e d e n e rv a tio n se e n in C h a g a s' d ise a se h a s
im m u n o lo g ic a l c a u se s, se v e ra l g ro u p s p ro d u c e d
m o n o c lo n a l a n tib o d ie s d isp la y in g c ro ssre a c tiv ity b e tw e e n
T. cruzi
a n d m a m m a lia n n e rv o u s tissu e . S e v e ra l su c ha n tib o d ie s c a u se d in sta n t p a ra ly sis a n d le th a l re sp ira to ry
d e p re ssio n w h e n in je c te d in to m ic e - a c lin ic a l p ic tu re th a t
c e rta in ly d o e s n o t m a tc h c h ro n ic C h a g a s' d ise a se (2 3 ).
V a n V o o rh is
&
E ise n d e fin e d a c ro ssre a c tiv e e p ito p e b e tw e e n a T .cruzi
fla g e lla r p ro te in a n d a n e u ro n a l 4 7 k D ap ro te in (3 6 ). H o w e v e r, th e p re se n c e o f c ro ssre a c tiv e
a n tib o d ie s in p a tie n ts' se ra d id n o t c o rre la te w ith a n y
c lin ic a l fo rm o f C h a g a s' d ise a se .
T h e in v o lv e m e n t o f p o ly c lo n a l T a n d B c e ll a c tiv a tio n
w a s c a re fu lly d isse c te d in th e m u rin e m o d e l o f a c u te
in fe c tio n b y
T. cruzi
(1 9 ). E v e n th o u g h th e se re su lts w e ren o t re p ro d u c e d d ire c tly in h u m a n s, th e " ly m p h o id "
c h a ra c te r o f a c u te
T. cruzi
in fe c tio n in h u m a n s, w ith th ea tte n d in g sp le e n a n d ly m p h n o d e e n la rg e m e n t a n d
p ro d u c tio n o f h e te ro p h ile a n tib o d ie s is ty p ic a l o f d ise a se
situ a tio n s w ith d e m o n stra te d p o ly c lo n a l ly m p h o c y te
a c tiv a tio n , lik e in fe c tio u s m o n o n u c le o sis. T h e p o ly c lo n a l
a c tiv a tio n o f th e a c u te p h a se o f C h a g a s' d ise a se c o u ld
e v e n tu a lly le a d to a u to im m u n ity b y b re a k in g d o w n
im m u n o lo g ic a l to le ra n c e to a g iv e n h e a rt a n tig e n . It is
d iffic u lt, h o w e v e r, to e x tra p o la te c o n c lu sio n s fro m th e
m u rin e m o d e l to th e c h ro n ic p h a se o f h u m a n C h a g a s'
d ise a se , a s it is k n o w n th a t th e p a ra site lo a d s in m u rin e
in fe c tio n s a re la rg e r a n d m o re p ro lo n g e d th a n in h u m a n
in fe c tio n s.
C A R D IA C
M Y O S IN : R E L E V A N T S E L F
A N T IG E N
IN T H E P A T H O G E N E S IS
O F
E X P E R IM E N T A L
C C C ?
A n u m b er o f th e ab o v e m en tio n ed p ap ers raised
refu tab le an d /o r in co n clu si v e ev id en ce fo r th e au to im m u n e
th eo ry o f C C C p ath o g en esis, in m an y cases ju st rep o rtin g
an tig en ic m im icry p h en o m en a b etw een
T. cruzi
an d h o sttissu e, w ith o u t clin ico -b io lo g ical co rrelatio n w ith C C C o r
d ig estiv e sy stem d en erv atio n ("m eg a sy n d ro m e").
K ierszem b au m stated th at, fo r C C C to b e co n sid ered as
an o rg an -sp ecific au to im m u n e d isease (lik e th y ro id itis,
in su lin -d ep en d en t d iab etes m ellitu s, etc.), tw o co n d itio n s
sh o u ld b e m et: i) th e id en tificatio n o f an o rg an -sp ecific
an tig en , a targ et to im m u n o lo g ically m ed iated h eart
d am ag e, an d ii) th e ab ility o f T cells o r an tib o d ies d eriv ed
fro m a
T. cruzi
in fected an im al an d sp ecific fo r th atself-an tig en , to p erfo rm p assi v e tran sfer o f h eart lesio n s to a
n o rm al an im al (1 5 ). A critical an aly sis o f th e literatu re u p
to th e m id -8 0 's sh o w s th at, alth o u g h th e h isto p ath o lo g ical
fin d in g s an d ex p erim en tal ev id en ce stro n g ly su g g est th e
ro le o f cellu lar im m u n ity to h eart tissu e co m p o n en ts in
C C C , th ere h as b een o n ly o n e stu d y fo cu sin g o n th e T cell
reco g n itio n o f a p artially d efin ed m u scle an tig en (1 ).
R ecen tly , tw o in d ep en d en t rep o rts p o in ted to w ard s
an im p o rtan t ro le fo r h eart-reactiv e C D 4 + T ly m p h o cy tes
in th e p ath o g en esis o f th e m u rin e m o d el o f C C C . R izzo ,
C u n h a-N eto & T eix eira (2 5 ) d em o n strated th e p resen ce
o f m y o sin -sp ecific C D 4 + T cells in m ice ch ro n ically
in fected b y
T. cruzi.
R ib eiro -d o s-S an to s, M en g u el et al.(2 4 ) rep o rted th at C D 4 + T cells reactiv e to h eart tissu e
o b tain ed fro m ch ro n ically
T. cruzi-infected
m ice, co u ldm ed iate h eart lesio n s w h en p assiv ely tran sferred (in jected )
in to sy n g en ic n o n -in fected m ice. It h as b een recen tly
d escrib ed th at th e g en eratio n o f an tib o d y ag ain st card iac
m y o sin H C is co rrelated to th e d ev elo p m en t o f ch ro n ic
in flam m ato ry card io p ath y am o n g ch ro n ically
T. cruzi
in fected m ice (3 3 ). M y o sin m ay b e a p rim e can d id ate targ et
au to an tig en in C C C . M y o sin h eav y ch ain (m y o sin H C ) is
th e m o st ab u n d an t h eart p ro tein - 5 0 % o f to tal p ro tein b y
w eig h t (1 2 ); m o reo v er, th e card iac iso fo rm o f m y o sin is
stru ctu rally d istin ct fro m o th er m y o sin iso fo rm s, lik e th o se
o f sk eletal o r sm o o tq m u scle (3 8 ). M y o sin is reco g n ized
in m an y situ atio n s o f h eart-sp ecific au to im m u n ity , su ch
as rh eu m atic h eart d isease (1 0 ) an d m u rin e p o st-C o x sack ie
v iru s B 3 au to im m u n e card io m y o p ath y (2 1 ). Im m u n izatio n
w ith card iac m y o sin H C in ad ju v an t in d u ces an ag g ressiv e
m y o card itis (2 2 ,3 0 ). T ak en to g eth er, th ese rep o rts p o in t
to a reaso n ab le co n sen su s ab o u t th e p o ssib le p articip atio n
o f card iac m y o sin -reactiv e T ly m p h o cy tes in m u rin e
m o d els o f C C C . T h e m u rin e m o d els cited ab o v e fu lfill
th e criteria d efin ed b y W iteb sk y et al. (3 7 ) fo r au to im m u n e
d iseases: th e id en tificatio n o f an o rg an -sp ecific self-an tig en
w h ich in d u ces tissu e lesio n s w h en in jected in to a n o rm al
an im al, an d th e rep ro d u ctio n o f th e lesio n w ith th e p assiv e
tran sfer o f ly m p h o cy tes.
A N T IG E N IC IT Y
O F C A R D IA C
M Y O S IN
IN
H U M A N C C C
E v en th o u g h th ere is reaso n ab le in fo rm atio n o n th e
p articip atio n o f h eart-reactiv e T cells in m u rin e m o d els o f
C C C , little is k n o w n in h u m an d isease. T h e estab lish m en t
o f h u m an C C C as an o rg an -sp ecific au to im m u n e d isease
d ep en d s o n th e co n firm atio n o f th e relev an ce o f th e o rg an
-sp ecific h eart an tig en reco g n ized in m u rin e m o d els (i.e.
m y o sin ) am o n g C C C p atien ts. In o rd er to v alid ate m y o sin
as a relev an t h eart an tig en in th e p ath o g en esis o f h u m an
C C C , w e p ro p o sed th e fo llo w in g w o rk in g h y p o th eses,
w h ich w ere th e co n cep tu al fram ew o rk fo r th e in v estig atio n
carried o u t in o u r lab o rato ry :
1 ) T h e ev o lu tio n to card io m y o p ath y , o r th e
p erm an en ce in th e asy m p to m atic fo rm , w o u ld b e a
co n seq u en ce o f d ifferen tial ab ility o f each in d iv id u al to
reco g n ize - o r n o t - a h eart-sp ecific m y o sin ep ito p e, after
u n ifo rm ex p o su re to an en v iro n m en tal facto r
(T. cruzi
in fectio n ).
2 ) T h e m ech an ism o f to leran ce b reak d o w n to card iac
m y o sin sh o u ld b e an tig en ic m im icry (stru ctu ral sim ilarity )
w ith cro ssreactiv e reco g n itio n b etw een m y o sin an d a
h ig h ly an tig en ic
T. cruzi
p ro tein - animmunodominanl
an tig en . T h e stro n g im m u n e resp o n se d irected to th e
p arasite an tig en sh o u ld raise an im m u n e resp o n se to th e
sh ared ep ito p e in card iac m y o sin , b u t o n ly in th o se
in d iv id u als cap ab le o f reco g n izin g it, as d escrib ed in th e
p rev io u s item .
3 ) T cells reactiv e ag ain st th e relev an t ep ito p e in
card iac m y o sin sh o u ld b e p resen t in th e in flam m ato ry
in filtrate o n h eart lesio n s o f C C C p atien ts, w h ich w o u ld
b e stro n g ly su g g estiv e o f th e in v o lv em en t o f su ch T cells
in th e im m u n e/in flam m ato ry resp o n se lead in g to
p ro g ressio n o f h eart tissu e d am ag e.
Antibody crossreactivity
between cardiac myosin and
T.c r u z i
antigen MXT: clinical and biological
relevance
W e p ro b ed sev eral reco m b in an t
T. cruzi
p ro tein s w ithsp ecific an ti-m y o sin Ig G an tib o d ies p u rified fro m sera
;;;~=~=~=1:~~=====$t."'='-'"$==~S;~W =="gS;'"*,~1==",,,Z ,"l
fro m
C C C
p a tie n ts.
O n e
o f th e
p ro te in s
te ste d
w a s
c ro ssre a c tiv e ly
re c o g n iz e d ,
in a sp e c ific
m a n n e r, b y a n
ti-m y o sin
a n tib o d ie s
- a n d th u s w a s c a lle d
M X T
p ro te in
(M y o sin
X
T. cruzi)
(fig u re
1 ). In o rd e r to c o n firm
th e
fin d in g ,
w e te ste d
th e re c o g n itio n
o f th e
T. cruzi
M X T
p ro te in
b y a n ti-m y o sin
a n tib o d ie s
p u rifie d
in d iv id u a lly
fro m
se ra
o f
2 8
C h a g a sic
p a tie n ts
(1 4
C C C ,
1 4
a sy m p to m a tic ).
A lth o u g h
th e te st w a s p e rfo rm e d
in a
lim ite d
n u m b e r
o f se ra ,
th e c o m p a rtm e n ta liz a tio n
o f
m y o sin -M X T
c ro ssre a c tiv e
a n tib o d ie s
a m o n g
C C C
p a tie n ts'
se ra
- 1 0 0 %
v s.
1 4 %
a m o n g
a sy m p to m a tic
c h a g a sic
se ra - w a s h ig h ly
sig n ific a n t
(p = 2 .3 x 1 0 -6 ,
F ish e r's
e x a c t te st), a s c a n b e se e n in F ig u re
2 . In o th e r
a u to im m u n e
d ise a se s,
lik e
in su lin -d e p e n d e n t
d ia b e te s
m e llitu s,
th e a sso c ia tio n
o f im m u n o lo g ic a l
re a c tiv ity
to
c e rta in
o rg a n -sp e c ific
se lf-a n tig e n s
(e .g G A D
e n z y m e )
w ith th e d ise a se
is ta k e n a s e v id e n c e
fo r th e in v o lv e m e n t
o f its im m u n e re c o g n itio n
in th e p a th o g e n e sis
o f th e d ise a se
(3 ).
In
o rd e r
to
in v e stig a te
w h e th e r
m y o sin -M X T
c ro ssre a c tiv e
a n tib o d ie s
m ig h t b e se c o n d a ry to h e a rt tissu e
d e stru c tio n
w ith e x tru sio n
o f in tra c e llu la r
p ro te in s
lik e
m y o sin ,
w e
lo o k e d
fo r
m y o sin -M X T
c ro ssre a c tiv e
a n tib o d ie s
in se ra fro m D u c h e n n e 's
m u sc u la r
d y stro p h y
p a tie n ts
p re se n tin g
d e g e te ra tiv e
c a rd io m y o p a th y
w ith o u t
in fla m m a to ry
e tio lo g y .
T h e
n e g a tiv e
re su lts
o b ta in e d
su g g e st
th a t
th e
m e re
e x p o su re
o f c a rd io m y o c y te
in tra c e llu la r
p ro te in s
m a y
n o t b e e n o u g h
to ra ise
th e
p ro d u c tio n
o f m y o sin -M X T
c ro ssre a c tiv e
a n tib o d ie s.
T h e a n tib o d y c ro ssre a c tiv ity
b e tw e e n c a rd ia c m y o sin
a n d
T. cruzi
M X T
a n tig e n
im p ly
th e sh a rin g
o f sim ila r
a m in o
a c id
se q u e n c e s
b e tw e e n
th e
tw o
p ro te in s,
a
stru c tu ra l sim ila rity u n d e rly in g " a n tig e n ic m im ic ry " . W h e n
th e a m in o a c id se q u e n c e s
o f h u m a n (3 8 ) b c a rd ia c m y o sin
h e a v y c h a in a n d
T.
cruzi
M X T p ro te in (A . G ru b e r a n d B .
Z in g a le s,
p e rso n a l
c o m m u n ic a tio n )
w e re c o m p a re d ,
w e
fo u n d
a 6 a m in o
a c id s-lo n g
se q u e n c e
th a t w a s v irtu a lly
id e n tic a l
in b o th p ro te in s,
w ith a sin g le
g ly c in e -le u c in e
su b sti tu ti o n .
C o m p e ti ti v e
i n h i b i tio n
a ssa y s
fo r
c ro ssre a c tiv e
a n tib o d ie s
e sta b lish e d
th a t th e h o m o lo g o u s
re g io n
w a s
in d e e d
th e
c ro ss-re a c tiv e
e p ito p e .
T h e
c ro ssre a c tiv e
e p ito p e is lo c a te d in th e 5 2 re g io n o f m y o sin ,
c lo se r
to its c a rb o x y -te rm in a l
e n d .
C o m p a riso n
o f th e
a m in o a c id se q u e n c e o f c a rd ia c m y o sin in th is stre tc h w ith
th o se
o f o th e r
tissu e -sp e c ific
iso fo rm s
o f m y o sin ,
lik e
sk e le ta l o r sm o o th m u sc le m y o sin , a s w e ll a s c y to p la sm ic
m y o sin ,
sh o w e d
th a t th e c ro ssre a c tiv e
e p ito p e
is
o n ly
e x p re sse d
in th e c a rd ia c m y o sin iso fo rm , th u s b e in g h e a rt
m u sc le -sp e c ific .
T o g e th e r, th e se re su lts su g g e st th a t a h e a rt
m u sc le -sp e c ific
e p ito p e
in c a rd ia c
m y o sin c ro ssre a c tiv e
w ith
T. crllzi
M X T p ro te in (b io lo g ic a l
re le v a n c e ),
m a y b e
re c o g n iz e d se le c tiv e ly
b y
T. crllzi-infected
in d iv id u a ls
w h o
d e v e lo p
h e a rt
d ise a se
(c lin ic a l
re le v a n c e ),
fu Ifi IIi n g
h y p o th e sis
n u m b e r (i).
Immunodominance
of
T . cruziantigen MXT.
A lth o u g h
m y o sin -M X T
c ro ssre a c tiv e
a n tib o d ie s
w e re p re se n t a lm o st e x c lu siv e ly
in se ra fro m C C C p a tie n ts,
M X T
p ro te in
itse lf c o u ld
b e re c o g n iz e d ,
p a ra d o x ic a lly ,
b y n o n -fra c tio n a te d
se ra fro m
1 0 0 % o f C h a g a sic
p a tie n ts
te ste d ,
n o m a tte r
w h e th e r
C C C
o r a sy m p to m a tic .
W e
in te rp re te d
th is fin d in g
in th e fo llo w in g
w a y : th e re
m a y
b e tw o d istin c t e p ito p e s in M X T p ro te in , o n ly o n e o f th e m
in a n tig e n ic m im ic ry w ith m y o sin , a n d th e o th e r o n e b e in g
sp e c ific
to M X T p ro te in . W e te ste d
th is h y p o th e sis
w ith
sy n th e tic
p e p tid e s
re p re se n tin g
e a c h e p ito p e .
O u r re su lts
su g g e st th a t C C C p a tie n ts'
se ra p o sse ss a n tib o d ie s
a g a in st
b o th
e p ito p e s,
w h ile
a sy m p to m a tic
p a tie n ts
ty p ic a lly
p o sse ss a n tib o d ie s
to th e M X T -sp e c ific
e p ito p e
(T a b le I).
B e sid e s, a n tib o d ie s
a g a in st
T. crllzi
M X T p ro te in
m a y b e
v e ry a b u n d a n t
in C h a g a sic
se ra , re a c h in g
h ig h tite rs a n d
a d d in g
u p
to
a s
m u c h
a sl
%o r
to ta l
se ru m
im m u n o g lo b u lin .
T h e se d a ta in d ic a te
th a t
T. cruzi
M X T
p ro te in , w h ic h p re se n ts im m u n o lo g ic a l
c ro ssre a c tiv ity
w ith
c a rd ia c
m y o sin ,
is
h ig h ly
im m u n o g e n ic
o r
Table 1
Recognition of im m unodom inant
and m yosin-cross-reactive
epitopes in T.
cruzi
M CT protein by sera from
Chagas'cardiopathy
(CCC) and asym ptom atic seropositive (ASY) individuals.
MXT epitopes
e e e
sera
ASY sera
Peptide 1
Peptide 2
Peptide 3
Peptide 4
immuno-dominant
+
+
Peptide 5
myosin-homologous
+
0000
A s y m p to m a tic S e ro p o s itiv e[ I
P o s itiv eE J
N e g a tiv eC h a g a s ' C a rd io p a th y
4 0 %
1 0 % 0 %
2 0 % 3 0 % 6 0 %
5 0 %
7 0 %
B O %
9 0 %
1 0 0 %
a n tig e n b M X T a n tig e n b e ta -g a la c to s id a d e
1 2 ,5n g
2 5 5 0
C O N C E N T R A T IO N
1 0 0
0000
F ig u re 1 . A n ti-c a rd ia c m y o s in a n tib o d ie s fro m C C C p a tie n ts
d is p la y c ro s s -re a c tiv ity w ith
T. cruzi
M X T p ro te in .F ig u re 2 . P re v a le n c e o f c a rd ia c m y o s in -M X T c ro s s re a c tiv e
a n tib o d ie s in s e ra fro m
T. cruzi-infected
C C C a n d A S Y in d iv id u a ls .im m u n o d o m in a n t, fu lfillin g p o s tu la te (ii) fro m th e w o rk in g
h y p o th e s e s .
Identification
of
Tcell clones derived from endomyocardial
biopsies from CCC patients, simultaneously
recognizing
cardiac myosin and
T . c ru z iprotein MXT.
T h e p a rtic ip a tio n o f th e c ro s s re a c tiv e a n tib o d y in th e
p a th o g e n e s is o f C C C is u n lik e ly . T h e in a b ility to fin d
im m u n o g lo b u lin d e p o s its o n to h e a rt fib e rs (1 4 ), to g e th e r
w ith th e T ly m p h o c y te -ric h in fla m m a to ry in filtra te , b o th
s u g g e s t s tro n g ly th e p a rtic ip a tio n o f T c e lls , a n d n o t
a n tib o d ie s , in C C C p a th o g e n e s is . In th is c o n te x t, w e c a n
in te rp re t th e id e n tific a tio n o f m y o s in -M X T c ro s s re a c tiv e
a n tib o d ie s in s e ra fro m 1 0 0 % o f C C C p a tie n ts a s a m a rk e r
fo r th e e x is te n c e o f C D 4 + T c e lls w ith s im ila r s p e c ific ity ,
a s is th e c a s e w ith m o s t T -c e ll d e p e n d e n t a n tib o d y
re s p o n s e s (s e e
current concepts in autoimmunity
s e c tio n ). S u c h c a rd ia c m y o s in -M X T c ro s s re a c tiv e a n tib o d ie s c a nc o n c e iv a b ly h a v e a n im p o rta n t ro le in C C C p a th o g e n e s is .
T h e id e n tific a tio n o f C D 4 + T c e lls in C C C h e a rt le s io n s ,
c ro s s re a c tiv e ly re c o g n iz in g th e h e a rt-s p e c ific e p ito p e o f
c a rd ia c m y o s in a n d M X T p ro te in (F ig u re 3 ) s ta n d s a s
e v id e n c e fo r a p o s s ib le p a rtic ip a tio n o f c a rd ia c m y o s in
-M X T c ro s s re a c ti v e re c o g n itio n b y T c e lls in th e
p a th o g e n e s is o f C C C , a n d fu lfills w o rk in g h y p o th e s is
n u m b e r (iii). T h e is o la tio n o f T c e lls re a c tiv e a g a in s t th e
re le v a n t s e lf-a n tig e n is a n im p o rta n t c rite rio n in th e
e s ta b lis h m e n t o f a u to im u n e e tio lo g y fo r a n y d is e a s e ,
a c c o rd in g to th e n e w c rite ria p o s tu la te d b y R o s e & B o n a (2 7 ).
H o w e v e r, h o w c o u ld a n in tra c e llu la r p ro te in lik e
c a rd ia c m y o s in b e c o m e a n tig e n ic ? R e c e n tly , S m ith & A lle n d e m o n s tra te d th a t in te rs titia l m a c ro p h a g e s fro m
n o rm a l h e a rt c a n p re s e n t c a rd ia c m y o s in a n tig e n ic p e p tid e s
c o u p le d to M H C c la s s II m o le c u le s , a n d a re c a p a b le to
s tim u la te m y o s in -s p e c ific C D 4 + T c e lls (2 9 ). T h e
e n d o c y to s is b y m a c ro p h a g e s o f m y o s in fro m h e a rt fib e rs
- w h ic h a llo w s p re s e n ta tio n o f its a n tig e n ic p e p tid e s - m ig h t
b e lin k e d to th e " s c a v e n g e r" fu n c tio n s o f m a c h o p h a g e s
u p o n s e n e s c e n t h e a rt c e lls . T h is w a y , th e a u th o rs c o u ld
e x p la in h o w m y o s in -s p e c ific C D 4 + T c e lls , s e n s itiz e d in
th e p e rip h e ry a fte r in je c tio n o f c a rd ia c m y o s in in th e
fo o tp a d s o f m ic e , c o u ld e v e n tu a lly re c o g n iz e th e ir ta rg e t
a n tig e n in th e n o rm a l h e a rt, a n d th u s s ta rt a p ro c e s s o f
d e la y e d -ty p e h y p e rs e n s itiv ity w ith h e a rt le s io n , in m y o s in
-in d u c e d e x p e rim e n ta l a u to im m u n e m y o c a rd itis .
C o u ld th e m y o s in -M X T c ro s s re a c tiv e T c e ll c lo n e s
fo u n d in h e a rt le s io n s b e th e m e d ia to rs o f C C C ? A n
a n a lo g y c a n b e d ra w n w ith e x p e rim e n ta l a u to im m u n e
m y o c a rd itis : a fte r s e n s itiz a tio n in th e p e rip h e ry b y
m a c ro p h a g e s e x p re s s in g th e M X T e p ito p e in th e ir H L A
c la ss II m o le c u le s a s a c o n se q u e n c e o f e n d o c y to sis o f
T.
cruzi,
m y o sin -M X T c ro ssre a c tiv e C D 4 + T c e lls th u se lic ite d c o u ld re c o g n iz e th e M X T -c ro ssre a c tiv e e p ito p e
o f c a rd ia c m y o sin p re se n te d b y H L A c la ss II m o le c u le s o f
h e a rt in te rstitia l m a c ro p h a g e s, w h e n re c irc u la tin g th ro u g h
th e h e a rt. O n th e o th e r h a n d , th is h y p o th e sis is a lso
c o n siste n t w ith th e e x iste n c e o f " h e lp e r" T c e lls re a c tiv e
to th e c a rd ia c m y o sin -M X T , n e c e ssa ry fo r th e p ro d u c tio n
o f c ro ssre a c tiv e a n tib o d ie s. T h is h y p o th e sis is d isp la y e d
sc h e m a tic a lly in F ig u re 4 . In o rd e r to c o n firm th e ro le
p la y e d b y th e se T c e ll c lo n e s in th e p a th o g e n e sis o f C C C ,
it w o u ld b e n e c e ssa ry to e sta b lish w h e th e r th e y a re c a p a b le
o f p ro d u c in g p ro -in fla m m a to ry ly m p h o k in e s in v o lv e d in
a d e la y e d -ty p e h y p e rse n sitiv ity re a c tio n .
Absence of detectable responses from
Teel/lines and
clones obtained from endomyocardial
biopsies of CCC
patients to
T . c ru z iantigens.
W h e n w e a ssa y e d th e a n tig e n re c o g n itio n o f T c e lls
d e riv e d fro m e n d o m y o c a rd ia l b io p sie s fro m C C C p a tie n ts,
w e w e re u n a b le to d e te c t a n y T c e ll lin e o r c lo n e p rim a rily
re a c tiv e to a n y
T. cruzi
a n tig e n te ste d in o u r p a n e l-fo u rim m u n o d o m in a n t p u rifie d
T. cruzi
a n tig e n s a n d a w h o letry p o m a stig o te ly sa te . T h is m e a n t te stin g o f 2 2 T c e ll
c lo n e s a n d 2 p o ly c lo n a l T c e ll lin e s d e riv e d fro m th re e
C C C p a tie n ts. T h e se n e g a tiv e re su lts a re in trig u in g , a s in
th is issu e H ig u c h i e t a l. d e m o n stra te d th a t
T. cruzi
fo rm s,a lb e it still u n fre q u e n t, c a n b e d e te c te d in C C C h e a rt tissu e
a re a s in v o lv e d in in fla m m a to ry le sio n s w ith th e a id o f
se n sitiv e im m u n o c h e m ic a l te c h n iq u e s (1 3 ). It c a n n o t b e
fo rm a lly e x c lu d e d th a t a n a rtifa c t o f th e T c e ll a ssa y
p ro to c o l, o r e v e n th e im m u n o lo g ic a l im b a la n c e k n o w n to
e x ist in
T. cruzi
in fe c tio n (1 9 ) c o u ld b e re sp o n sib le fo r th ea p p a re n t a b se n c e o f p ro life ra tiv e re sp o n se to
T. cruzi
a n tig e n s. O n th e o th e r h a n d , it is p o ssib le th a t o u r n e g a tiv e
fin d in g w a s c a u se d b y th e sc a rc e a n d d isp e rse d istrib u tio n
o f p a ra site s in C C C h e a rt tissu e - w h ic h b y th e w a y is
c o m m o n in o th e r o rg a n s a s w e ll, a s is a tte ste d b y th e
tra n sm issio n o f
T. cruzi
in fe c tio n b y a k id n e y tra n sp la n tfro m a n in fe c te d d o n o r (6 ). S p e c ific a lly , n o n e o f th e C C C
p a tie n ts fro m w h o m w e o b ta in e d h e a rt-d e riv e d T c e lls
p re se n te d p a ra site s in th e e n d o m y o c a rd ia l b io p sy
fra g m e n ts o b ta in e d . T h is se e m s to su g g e st th a t, a t le a st in
th e a re a s o f h e a rt tissu e fre e fro m th e p a ra site , th e d ire c t
a n tig e n ic stim u lu s o f
T. cruzi
d o e s n o t se e m to b e th ed e te rm in in g e v e n t fo r th e ly m p h o c y tic in filtra te . T h is d o e s
n o t im p ly , h o w e v e r, th a t th e T c e ll in filtra te in h e a rt tissu e
a re a s su rro u n d in g ru p tu re d p se u d o c y sts o r fre e in ste rsitia l
p a ra site s m a y n o t b e d ire c tly stim u la te d b y
T. cruzi
a n tig e n s. O n th e o th e r h a n d , th e fa c t th a t tre a tm e n t o f
e x p e rim e n ta lly
T. cruzi
in fe c te d ra b b its w ith a n ti-T .cruzi
d ru g s d u rin g a c u te p h a se o f in fe c tio n d o e s n o t p re v e n t
p ro g re ssio n to c h ro n ic c a rd io p a th y su g g e sts th a t th e
p h y sic a l p re se n c e o f
T. cruzi
h a s little d ire c t p a rtic ip a tio nin th e p a th o g e n e sis o f C C C (3 1 ). F u rth e rm o re , a s m o st
h e a rt tissu e in C C C p a tie n ts is a ffe c te d b y a d e stru c tiv e
m y o c a rd itis w ith a ly m p h o c y tic in filtra te in th e a b se n c e
o f d e te c ta b le
T. cruzi
fo rm s, it se e m s re a so n a b le to su g g e stth a t a g o o d d e a l o f th e h e a rt tissu e le sio n se e n in C C C is
8
7
6
5
4
3
2
o
p< 0 .0 1
0 < 0 .0 1 5
4
0 > 0 .0 5
I
~
f - . 1 1 ,4 I
-1
N e g a tiv e C o n tro l
C a rd ia c M y o s in
S k e le ta l M y o s in
M X T p ro te in
F ig u re 3 . P ro life ra tiv e re s p o n s e o f G D 4 + T c e ll c lo n e E 2 0 5 , d e riv e d fro m e n d o m y o c a rd ia l b io p s y fro m G G G p a tie n t.
P F : R I P I I E R A L M A C R O I 'I I A G F . I \ I X TC A R D I A C M Y O S I N
I 'E R I P I l F . R Y : S E N S I T I Z A T I O N A G A I N S T T. cnd
T : C A R D I A C M Y O S I N - M X T C R O S S . R E A C T I V E C D 4 + T L Y M P I I O C Y T E S I I : C A R D I A C M Y O S I N . M X T C R O S S - R E A C T I V E B L Y M P H O C Y T E S
I \ I X T . M Y O : C A R D I A C M Y O S I N - H O M O L O G O U S E P I T O P EI NT.ClU:;M X TP R O T E I N
Figure 4.
P a r t ic ip a t io n o f c a r d ia c m y o s in - M X T c r o s s - r e a c t iv ee D 4 +
T c e ll c lo n e s in t h e p a t h o g e n e s is o f h e a r t le s io n s ine e e .
m e d i a t e d b y c a r d i a c m y o s i n - r e a c t i v e T c e l l s , s e n s i t i z e d
b y a n t i g e n i c m i m i c r y w i t h t h e i m m u n o d o m i n a n t
T. cruZl
a n t i g e n M X T . I n o u r m o d e l , a m o n g
T. cruZl-infected
i n d i v i d u a l s , o n l y i n d i v i d u a l s c a p a b l e o f r e c o g n i z i n g t h e
c r o s s r e a c t i v e e p i t o p e a t t h e h u m o r a l a n d T c e l l l e v e l w o u l d
p o s s e s s c a r d i a c m y o s i n - M X T c r o s s r e a c t i v e T c e l l s a b l e
t o i n i t i a t e i n f l a m m a t o r y d a m a g e t o h e a r t c e l l s , t h u s b e i n g
s u s c e p t i b l e t o d e v e l o p i n g C C C .
PERSPECTIVES
W e m o l e c u l a r l y i d e n t i f i e d a c r o s s r e a c t i v e e p i t o p e
b e t w e e n h u m a n c a r d i a c m y o s i n a n d
T. cruZl
p r o t e i n M X T ,d o w n t o t h e a m i n o a c i d s e q u e n c e l e v e l . W e e s t a b l i s h e d
t h a t t h e c r o s s r e a c t i v e e p i t o p e i n c a r d i a c m y o s i n i s a h e a r t
-s p e c i f i c a m i n o a c i d s e q u e n c e . W e d e m o n s t r a t e d t h a t t h i s
c r o s s r e a c t i v e e p i t o p e s e e m s t o b e a l m o s t e x c l u s i v e l y
r e c o g n i z e d b y C C C r a t h e r t h a n a s y m p t o m a t i c p a t i e n t s , t h u s
d e f i n i n g t h e c l i n i c a l r e l e v a n c e o f i t s r e c o g n i t i o n . F i n a l l y ,
w e i d e n t i f i e d T c e l l c l o n e s d e r i v e d f r o m t h e h e a r t l e s i o n
s i t e s o f C C C p a t i e n t s t h a t s i m u l t a n e o u s l y r e c o g n i z e
c a r d i a c - b u t n o t s k e l e t a l - m y o s i n a n d M X T p r o t e i n .
T a k e n t o g e t h e r , o u r d a t a s e e m t o s u g g e s t a m a j o r
r o l e f o r a u t o i m m u n i t y i n t h e p a t h o g e n e s i s o f C C C .
T o g e t h e r w i t h t h e e v i d e n c e i n m u r i n e m o d e l s , t h e d e s c r i b e d
d a t a m a y e s t a b l i s h h u m a n C C C a s a t r u e o r g a n - s p e c i f i c
a u t o i m m u n e d i s e a s e , a s t h e e v i d e n c e f o r i t i s c o m p a r a b l e
t o t h a t s u p p o r t i n g t h e a u t o i m m u n e e t i o l o g y o f " c l a s s i c a l "
a u t o i m m u n e d i s e a s e s l i k e i n s u l i n - d e p e n d e n t d i a b e t e s
m e l l i t u s . T h e d e f i n i t i o n o f t h e h e a r t a n t i g e n r e l e v a n t f o r
t h e p a t h o g e n e s i s o f a n a u t o i m m u n e d i s e a s e i s t h e f i r s t s t e p
f o r c o n c e i v i n g a n t i g e n - s p e c i f i c i m m u n o m o d u l a t i o n
a p p r o a c h e s i n t h e r a p y , a s a m e a n s t o a b o l i s h t h e d e l e t e r i o u s
a u t o i m m u n e r e s p o n s e w h i l e l e a v i n g t h e p r o t e c t i v e a n t i
-p a r a s i t e r e s p o n s e i n t a c t . T h e f i r s t t h e r a p e u t i c t r i a l s o f
a n t i g e n - s p e c i f i c i m m u n o m o d u l a t i o n i n m u r i n e a n d h u m a n
a u t o i m m u n e d i s e a s e s l i k e m u l t i p l e s c l e r o s i s , r h e u m a t o i d
a r t h r i t i s , a n d u v e i t i s h a v e b e e n r e c e n t l y p u b l i s h e d ( 2 6 , 3 9 ) .
O n t h e o t h e r h a n d , o u r f i n d i n g s m a y f i n a l l y a l l o w t h e
s e a r c h f o r e f f e c t i v e s u b u n i t v a c c i n e s d e v o i d o f c o m p o n e n t s
o f
T. cruZl
t h a t b e a r t h e p a t h o g e n i c h e a r t - c r o s s r e a c t i v ed e t e r m i n a n t s .
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