Immunoprotection against T. cruzi infection elicited by an oral multicomponent DNA vaccine delivered by attenuated Salmonella.

CAZORLA SI, MATOS M, CERNY N, SANCHEZ ALBERTI A, BIVONA A, MORALES C, GUZMÁN CA, MALCHIODI EL

Simposio; Immunological Mechanisms of Vaccination (S3). Keystone Symposium; 2012

We recently reported the efficacy of attenuated Salmonella enterica (S) carrying plasmid encoding the cystein protease of T. cruzi cruzipain (SCz) to protect against T. cruzi  infection [Cazorla et al. Infect Immun 2008]. Here, we evaluated whether immunoprotection could be improved by the co-administration of three Salmonella carrying each one of the plasmids encoding Cz, Tc52 (a thiol-transferase) and Tc24 (a 24 kDa flagellar calcium binding protein). Groups of mice were orally administrated with single SCz, STc52 or STc24, and another group with the three Salmonella at once (SCz+STc52+STc24). Surprisingly, mice immunized with SCz+STc52+STc24 presented an increased antibody response against each recombinant antigen, compared with the other groups. Trypomastigotes lyses mediated by antibodies in the presence of complement as well as cell invasion inhibition were higher in mice immunized with the SCz+STc52+STc24 and in single SCz and STc52, but STc24 was not different than the control group. Surprisingly, STc24 showed the highest DTH test compared with SCz, STc52, and even with SCz+STc52+STc24. Animals were challenged with 1000 RA trypomastigotes by intraperitoneal route and parasitemia was evaluated. SCz+STc52+STc24, SCz and STc52 rendered lower parasitemia but STc24 could not be distinguished from control group. Mice weight lost after infection (-20 to -30%) was detected in all except in SCz+STc52+STc24 group. We also observed that the activity of the cardiomyopathy-associated enzymes was significant lower in SCz+STc24+STc52 immunized mice compared with controls (*p<0.05, **p<0.01 and ***p<0.01 for CK, LDH and AST, respectively). The activity of these enzymes was also low in SCz and STc52 infected mice, in contrast with STc24 that presented levels similar to controls mice. We were not able to identify any anormality in heart of SCz+STc24+STc52 immunized and infected mice by microscopic examination of hearts. By contrast, controls mice presented small inflammatory foci, necrosis and severe amastigotes nests. We conclude that despite no strict additive effect could be observed; the multicomponent vaccine improved all the parameter tested in comparison with single component vaccine.