Trypanosoma cruzi Carrying a Monoallelic Deletion of the Calreticulin (TcCRT) gene are Susceptible to Complement Mediated Killing and Defective in their Metacyclogenesis

FERNANDO SÁNCHEZ VALDEZ; CECILIA PÉREZ BRANDAN; PAOLA ZAGO; CARLOS LABRIOLA; ARTURO FERREIRA; MIGUEL ANGEL BASOMBRIO

MOLECULAR IMMUNOLOGY

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2012

0161-5890

Trypanosoma cruzi Calreticulin (TcCRT) can hijack C1, mannan-binding lectin and ficolins from serum thus inhibiting the classical and lectin complement pathway activation respectively. To understand the in vivo biological functions of TcCRT in T. cruzi we generated a clonal cell line lacking one TcCRT allele (TcCRT+/-) and another clone overexpressing it (TcCRT+). Both clones were derived from the TCC T. cruzi strain. As expected, TcCRT+/- epimastigotes showed impairment on TcCRT synthesis, whereas TcCRT+ ones showed increased protein levels. In correlation to this, monoallelic mutant parasites were significantly susceptible to killing by the complement machinery. On the contrary, TcCRT+ parasites showed higher levels of resistance to killing mediate by the classical and lectin but not the alternative pathway. The involvement of surface TcCRT in depleting C1 was demonstrated through restoration of serum killing activity by addition of exogenous C1. In axenic cultures, a reduced propagation rate of TcCRT+/- parasites was observed. Moreover, TcCRT+/- parasites presented a reduced rate of differentiation in in vitro assays. As shown by down- or upregulation of TcCRT expression this gene seems to play a major role in providing T. cruzi with the ability to resist complement system.