Novel Protective Antigens Expressed by Trypanosoma cruzi Amastigotes Provide Immunity to Mice Highly Susceptible to Chagas' Disease

Abstract

Earlier studies have demonstrated in A/Sn mice highly susceptible to Chagas' disease protective immunity against lethal Trypanosoma cruzi infection elicited by vaccination with an open reading frame (ORF) expressed by amastigotes. In our experiments, we used this mouse model to search for other amastigote-expressed ORFs with a similar property. Fourteen ORFs previously determined to be expressed in this developmental stage were individually inserted into a eukaryotic expression vector containing a nucleotide sequence that encoded a mammalian secretory signal peptide. Immunization with 13 of the 14 ORFs induced specific antibodies which recognized the amastigotes. Three of those immune sera also reacted with trypomastigotes and epimastigotes. After a lethal challenge with Y strain trypomastigotes, the vast majority of plasmid-injected mice succumbed to infection. In some cases, a significant delay in mortality was observed. Only two of these ORFs provided protective immunity against the otherwise lethal infection caused by trypomastigotes of the Y or Colombia strain. These ORFs encode members of the trans-sialidase family of surface antigens related to the previously described protective antigen amastigote surface protein 2 (ASP-2). Nevertheless, at the level of antibody recognition, no cross-reactivity was observed between the ORFs and the previously described ASP-2 from the Y strain. In immunofluorescence analyses, we observed the presence of epitopes related to both proteins expressed by amastigotes of seven different strains. In conclusion, our approach allowed us to successfully identify two novel protective ORFs which we consider interesting for future studies on the immune response to Chagas' disease.

Recombinant Enolase of Trypanosoma cruzi as a Novel Vaccine Candidate against Chagas Disease in a Mouse Model of Acute Infection

“…In most immunization cases, a Th1-type immune response was observed. These genes and proteins were tested for vaccine trials in experimental models of infection, including cruzipain [ 13 , 14 ], trans -sialidase [ 15 , 16 ], amastigote surface protein-2 [ 17 ], LYT-1 [ 18 ], and paraflagellar rod protein [ 19 ] among others.…”

Perforin and Gamma Interferon Expression Are Required for CD4+and CD8+T-Cell-Dependent Protective Immunity against a Human Parasite,Trypanosoma cruzi, Elicited by Heterologous Plasmid DNA Prime-Recombinant Adenovirus 5 Boost Vaccination

“…In our previous studies, we showed that multiple immunizations of highly susceptible A/Sn mice with a gene or a recombinant protein based on the amastigote surface protein 2 (ASP-2) of T. cruzi generated protective immunity against a lethal challenge with this parasite (6,17,19,55,60). In both cases, vaccinated animals depleted of CD8 ϩ T cells prior to challenge became highly susceptible to infection (6,60).…”

A Novel Vaccine Approach for Chagas Disease Using Rare Adenovirus Serotype 48 Vectors

“…We reasoned that a vaccine vector including gp83 neutralizing epitope, amastigote surface protein-2 (ASP-2), or an epitope of the carboxyl region of amastigote surface protein-2 (ASP-C), respectively, would be beneficial for a T. cruzi vaccine vector. ASP-2 is a protein of yet unknown function in the biology of the parasite [ 50 , 51 , 52 ]; however, it has been important for pre-clinical T. cruzi vaccine efforts [ 53 , 54 ].…”