Acquired Immunity against Trypanosoma cruzi Infection and Vaccine Development

The obligatory intracellular protozoan Trypanosoma cruzi is an extremely successful parasite infecting a vast number of distinct mammalian hosts across the Americas. T. cruzi relies heavily on the innate and adaptive immunological mechanisms to maintain the host alive during the acute phase and to establish a chronic infection, when the transmission to the invertebrate host occurs. This long term persistence is considered a major force behind the chronic symptoms of the disease observed in humans. Mechanisms that keep host alive during the acute phase have been dissected using genetically deficient mice and they include Toll-like receptors, cytokines (Interferon-gamma, TNF-α, MIF and IL-12), lymphocytes (B, CD4, CD8 and NKT) and NK cells. Target antigens for specific lymphocytes are members of the trans-sialidase, mucin-like, cysteine protease families, etc. Vaccination studies are being performed using different delivery systems such as recombinant proteins, plasmid DNA and microorganisms. Non-antibody mediated cellular immune responses (CD4+ Th1 and CD8+ Tc1) to specific parasite antigens/genes can indeed be used for the purpose of vaccination against acute phase mortality and, in some cases, chronic phase pathology. These results obtained in the mouse model indicate a possible path for a veterinary or human vaccine development