**2.2.3 Humoral adaptative immunity**

The importance of humoral immunity in controlling *T. cruzi* acute infection has been clearly established. Mice lacking B lymphocytes rapidly succumb to infection (Kumar & Tarleton, 1998). But the fact that attracted most attention is the production of autoantibodies.

Pathogenesis and Pathology of Chagas' Chronic Myocarditis 127

Fig. 2B. The immune pathogenesis of Chagas disease in CCC patients. Cells evolve towards

a proinflammatory profile, with development of autoimmunity.

Fig. 2A. The immune pathogenesis of Chagas disease in indeterminate patients. The presence on numerous down regulating mechanisms shift the response towards an antiinflammatory profile.

Fig. 2A. The immune pathogenesis of Chagas disease in indeterminate patients. The presence on numerous down regulating mechanisms shift the response towards an anti-

inflammatory profile.

Fig. 2B. The immune pathogenesis of Chagas disease in CCC patients. Cells evolve towards a proinflammatory profile, with development of autoimmunity.

Pathogenesis and Pathology of Chagas' Chronic Myocarditis 129

Anti-Gal Apparently protective (Gazzinelli, 1991)

Microtubules Unknown (Kerner, et al., 1991) Anti-Ribosome Unknown (Levitus, et al., 1991,

Anti- UsnRNPs Unkwnown (Bach-Elias, et al.,

Anti-Galectin-1 Increased in CCC patients (Giordanengo L., et al.,

Anti-Cha R3 Specific of CCC (Girones, et al., 2001a) Anti-Desmoglein-1 Related to Penphigus foliaceum (Diaz, et al., 2004) Anticardiolipin Unknown (Pereira De Godoy, et

Anti-MBP Related to gastrointestinal form (Oliveira E. C., et al.,

Antibodies against AV node and sinus auricular node tissues have been studied as markers of CCC. When compared in chronic chagasic cardiopathy patients, non-chagasic cardiopathy patients, indeterminate chagasic subjects and healthy blood donors as controls, they more frequently found in chronic chagasic cardiopathy, but not enough to be good markers for chagasic cardiopathy group. Besides, no clear association with complex rhythm

Many other autoantibodies have been described (table 2) but are not so widely studied and

Human leukocyte antigens (HLA) have shown some relation to the development of CCC. HLA-B40 and Cw3 combination was protective for CCC (Llop, et al., 1991), as resulted DRB1\*14, DQB1\*0303 (Fernandez-Mestre, et al., 1998), HLA-DQB1\*06 (Deghaide, et al., 1998) and HLA-A68 (Cruz-Robles, et al., 2004). On the other hand, HLA-C\*03 (Layrisse, et al., 2000), DRB1\*1503 (Garcia Borras, et al., 2009), DRB1\*01, DRB1\*08, DQB1\*0501 (Fernandez-Mestre, et al., 1998) and HLA-DR16 alelles (Cruz-Robles, et al., 2004) were

A number of other genes related to immune system have been studied in order to determine their relation to a predisposition to develop CCC. In table 3 we list those positively related

Prevents apoptosis of neurons and helps

symptoms (Avila & Rojas, 1990)

arrhythmias (Garcia, et al., 1998)

cellular invasion (Lu, et al., 2010)

Skeiky, et al., 1992)

1998)

2001)

al., 2005)

2009)

**Autoantibody Hypothetic pathogenic role Reference** 

Anti-Cerebroside Probably related to neurologial

Anti-Sulfatides May cause myocarditis and induce

Table 2. Less studied autoantibodies in Chagas' disease.

or conduction alterations was found (Arce-Fonseca, et al., 2005).

their role in pathogenesis of chagasic myocarditis is not clear.

positively related to the development of CCC.

to the appearance of CCC (Cunha-Neto E., et al., 2009).

Anti-Brain

Anti- TrkA, TrkB and TrkC

**2.2.4 Genetic factors** 

The first autoantibody to be described was one that reacted to endocardium, blood vessels and interstitium of skeletal muscle (EVI) (Cossio, et al., 1974), but was the same group of investigators who recognized the heterophil nature of the antibody and realized that had no pathogenic role (Khoury, et al., 1983).

Another autoantibody, studied by our group, was anti-laminin antibody (Sanchez, Milei et al. 1993, (Milei, et al., 1993). These antibodies were shown to react against *T. cruzi* amastigotes and trypomastigotes and human laminin (Szarfman, et al., 1982) and deposition of this antibody in marked thickened basement membranes of myocytes, endothelial cells, and vascular smooth muscle cells was shown by us with light microscopy, electron microscopy and immunohistochemical techniques in endomyocardial biopsies of chagasic patients (Sanchez, et al., 1993) but then we found that only 50% of patients had the antibody on their sera and no correlation with disease severity could be established (Milei, et al., 1993).

Anti-myosin antibodies were postulated by some authors to be generated through molecular mimicry with two *T. cruzi* antigens: B13 protein (Gruber & Zingales, 1993) and cruzipain (Giordanengo Laura, et al., 2000a, Giordanengo Laura, et al., 2000b). Although cruzipain antibodies mainly react to skeletal muscle myosin, they can cause conduction disturbances when transferred to uninfected mice and, when transferred to pregnant animals, they caused conduction disturbances in pups (Giordanengo Laura, et al., 2000b). On the other hand, immunossuppresed mice did not mount any humoral response when immunized with myosin but still develop myocarditis (Neu, et al., 1990). This fact made some authors doubt on the molecular mimicry hypothesis and rather consider antibodies to myosin a consequence of myocyte damage (Kierszenbaum, 2003).

Antibodies that react with muscarinic receptors were intensely studied. In early 1990's IgG from chagasic patients was observed to bind to muscarinic M2 receptors and activate them (Sterin-Borda L, et al., 1991). These anti-muscarinic antibodies were found to increase intracellular cGMP and decrease cAMP (Goin J., et al., 1997) and were positively related to the presence of dysautonomia (Goin J. C., et al., 1994). These antibodies also caused accumulation of inositol phosphate and nitric oxide synthase stimulation, with a negative inotropic effect on myocardium (Sterin-Borda Leonor, et al., 1997). As mentioned before, anti-muscarinic autoantibodies are positively related to the presence of dysautonomia (Goin J. C., et al., 1994), the presence of achalasia in chagasic patients (Goin J. C., et al., 1999), sinus node dysfunction (Altschuller, et al., 2007), but are not related with the degree of myocardial dysfunction (Altschuller, et al., 2007, Talvani Andre, et al., 2006), nor with the presence of brain lesions (Py, et al., 2009). In fact, patients with cardiomyopathy and left ventricular dysfunction but without autonomic dysfunction show low levels of anti-muscarinic antibodies (Sterin-Borda Leonor & Borda, 2000).

Antibodies against 1-adrenergic receptors were also deeply studied. Described in early 1980's (Borda E., et al., 1984) these antibodies increased cAMP in mouse atrial fibers, increasing the release of PGE2 and TXB2 causing diminished contractility (Gorelik, et al., 1990). Increased cAMP activates PKA and then increases the intracellular calcium concentration. This causes in turn inhibition of the Na+/K+-ATPase and stimulates Ca2+- ATPase activity leading to intracellular depletion of K+ and further increase in Ca2+. These alteration alter contractility and electric impulse generation and conduction (Borda E. S. & Sterin-Borda, 1996). Antiadrenergic autoantibodies titers could not be related to the severity of left ventricular dysfunction (Talvani Andre, et al., 2006) and patients with overt cardiomyopathy but without autonomic dysfunction show low levels of these antibodies (Sterin-Borda Leonor & Borda, 2000). Antibodies against 2-adrenergic receptors have also been described but are mainly related to megacolon (Wallukat, et al., 2010).

The first autoantibody to be described was one that reacted to endocardium, blood vessels and interstitium of skeletal muscle (EVI) (Cossio, et al., 1974), but was the same group of investigators who recognized the heterophil nature of the antibody and realized that had no

Another autoantibody, studied by our group, was anti-laminin antibody (Sanchez, Milei et al. 1993, (Milei, et al., 1993). These antibodies were shown to react against *T. cruzi* amastigotes and trypomastigotes and human laminin (Szarfman, et al., 1982) and deposition of this antibody in marked thickened basement membranes of myocytes, endothelial cells, and vascular smooth muscle cells was shown by us with light microscopy, electron microscopy and immunohistochemical techniques in endomyocardial biopsies of chagasic patients (Sanchez, et al., 1993) but then we found that only 50% of patients had the antibody on their sera and no

Anti-myosin antibodies were postulated by some authors to be generated through molecular mimicry with two *T. cruzi* antigens: B13 protein (Gruber & Zingales, 1993) and cruzipain (Giordanengo Laura, et al., 2000a, Giordanengo Laura, et al., 2000b). Although cruzipain antibodies mainly react to skeletal muscle myosin, they can cause conduction disturbances when transferred to uninfected mice and, when transferred to pregnant animals, they caused conduction disturbances in pups (Giordanengo Laura, et al., 2000b). On the other hand, immunossuppresed mice did not mount any humoral response when immunized with myosin but still develop myocarditis (Neu, et al., 1990). This fact made some authors doubt on the molecular mimicry hypothesis and rather consider antibodies to

Antibodies that react with muscarinic receptors were intensely studied. In early 1990's IgG from chagasic patients was observed to bind to muscarinic M2 receptors and activate them (Sterin-Borda L, et al., 1991). These anti-muscarinic antibodies were found to increase intracellular cGMP and decrease cAMP (Goin J., et al., 1997) and were positively related to the presence of dysautonomia (Goin J. C., et al., 1994). These antibodies also caused accumulation of inositol phosphate and nitric oxide synthase stimulation, with a negative inotropic effect on myocardium (Sterin-Borda Leonor, et al., 1997). As mentioned before, anti-muscarinic autoantibodies are positively related to the presence of dysautonomia (Goin J. C., et al., 1994), the presence of achalasia in chagasic patients (Goin J. C., et al., 1999), sinus node dysfunction (Altschuller, et al., 2007), but are not related with the degree of myocardial dysfunction (Altschuller, et al., 2007, Talvani Andre, et al., 2006), nor with the presence of brain lesions (Py, et al., 2009). In fact, patients with cardiomyopathy and left ventricular dysfunction but without autonomic dysfunction show low levels of anti-muscarinic

Antibodies against 1-adrenergic receptors were also deeply studied. Described in early 1980's (Borda E., et al., 1984) these antibodies increased cAMP in mouse atrial fibers, increasing the release of PGE2 and TXB2 causing diminished contractility (Gorelik, et al., 1990). Increased cAMP activates PKA and then increases the intracellular calcium concentration. This causes in turn inhibition of the Na+/K+-ATPase and stimulates Ca2+- ATPase activity leading to intracellular depletion of K+ and further increase in Ca2+. These alteration alter contractility and electric impulse generation and conduction (Borda E. S. & Sterin-Borda, 1996). Antiadrenergic autoantibodies titers could not be related to the severity of left ventricular dysfunction (Talvani Andre, et al., 2006) and patients with overt cardiomyopathy but without autonomic dysfunction show low levels of these antibodies (Sterin-Borda Leonor & Borda, 2000). Antibodies against 2-adrenergic receptors have also

been described but are mainly related to megacolon (Wallukat, et al., 2010).

correlation with disease severity could be established (Milei, et al., 1993).

myosin a consequence of myocyte damage (Kierszenbaum, 2003).

antibodies (Sterin-Borda Leonor & Borda, 2000).

pathogenic role (Khoury, et al., 1983).


Table 2. Less studied autoantibodies in Chagas' disease.

Antibodies against AV node and sinus auricular node tissues have been studied as markers of CCC. When compared in chronic chagasic cardiopathy patients, non-chagasic cardiopathy patients, indeterminate chagasic subjects and healthy blood donors as controls, they more frequently found in chronic chagasic cardiopathy, but not enough to be good markers for chagasic cardiopathy group. Besides, no clear association with complex rhythm or conduction alterations was found (Arce-Fonseca, et al., 2005).

Many other autoantibodies have been described (table 2) but are not so widely studied and their role in pathogenesis of chagasic myocarditis is not clear.
