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Antibodies against the trans-sialidase activity from Trypanosoma cruzi restrict pathogenesis during the infection
PITCOVSKY TAMARA; RISSO MARIKENA; MOCETTI ESTEBAN; CAMPETELLA OSCAR; LEGUIZAMÓN M SUSANA
Congreso; 12th International Congress of Immunology; 2004
Federation of Clinical Immunology Societies
Trypanosoma cruzi, the agent of Chagas´ disease, is unable to perform synthesis of sialic acids de novo. To overcome this failure, the parasite acquires the sugar directly from the glycoconjugates of the host through an enzyme known as the trans-sialidase. This enzyme is shed and find in the blood of infected animals and patients during the acute phase of the infection, acting as a virulence factor by inducing apoptosis on cell from the immune system. Humoral response able to neutralize the activity is finally induced although its characterization at the molecular and biological level was hampered due to the absence of monoclonal antibodies. After deleting several spurious epitopes present in the molecule that seems to distract the immune system, we were able to construct a recombinant enzyme useful as an immunogen to improve the humoral neutralizing response. From responder mice, a neutralizing monoclonal antibody from the IgG2a subclass was finally obtained. The KD was 7.18-10M as determined by BIAcore. This antibody was tested in protection assays both in vivo and in vitro against the virulent RA strain of T. cruzi. It was able to partially protect HeLa cell monolayers from infection and to strong reduce the parasite invasion of muscle in vivo. The immune system of infected animals was protected from the trans-sialidase-induced apoptosis as evaluated in thymus, spleen and peripheral ganglia from infected animals that were passively transferred with the neutralizing monoclonal antibody. This antibody constitutes the first defined inhibitory molecule of the trans-sialidase and confirms its relevance as a virulence factor from the parasite.