Localization of the Trypanosoma cruzi-specific Mr 25,000 antigen by immune electron microscopy using monoclonal antibodies

PCR and sero-diagnosis of chronic Chagas' disease. Biotechnological advances

In the acute phase of Chagas' disease, when the parasitemia is high, diagnosis can be easily made using conventional parasitological methods. During the chronic phase, due to the low parasitemia, diagnosis is performed mainly by immunological methods. Conventional serological techniques are limited by cross-reactivity with other parasitic diseases, non-standardization of reagents, and the diversity of technical procedures. Methods are being developed to improve the sensitivity and specificity of diagnosis using molecular approaches. PCR-based detection systems and the use of recombinant antigens in ELISA are the most promising.

[The protective effects of monoclonal antibodies in mice from Naegleria fowleri infection]

Protective effects of monoclonal antibodies against N. fowleri were comparatively studied. BALB/c mice were treated with two types of monoclonal antibodies, Nf 2 and Nf 154, before and after the infection with N. fowleri. The mortality and mean survival times were then compared. Also, direct effect of the monoclonal antibodies on the N. fowleri trophozoites in vitro were observed. In vitro protective effects of the monoclonal antibodies were also studied in cells infected with N. fowleri. The observed results are summarized as follows: 1. Among mice pretreated twice before the infection with monoclonal antibody Nf 2(McAb Nf 2), only 15.8% were killed, and the mean survival time was 17.7 days. This was not much different from the mice pretreated once, as the mortality and mean survival time were 16.7% and 17 days. Those effects were compatible with monoclonal antibody Nf 154(McAb Nf 154). The above findings contrast with the mortality and mean survival time of the control mice, which were 22.7% and 14.6 days respectively. 2. Mice which received twice the McAb Nf 2 following N. fowleri infection incurred a 19.4% mortality rate with 13.6 days survival time; 17.9% and 15.8 days with on time administration, in contrast to the 25% and 14.6 days in the control group. 3. Marked agglutination effect of McAb Nf 2 or McAb Nf 154 were observed on N. fowleri trophozoites. 4. When N. fowleri trophozoites were treated with McAb Nf 2 or McAb Nf 154 combined with comments, the proliferation rate was more significantly suppressed than in that the control. 5. N. fowleri trophozoites treated with McAb Nf 2 or McAb Nf 154 showed an increased number of swollen mitochondria, disfigured cisternae, lipid droplets, and osmiophilic granules in the cytoplasm. 6. A remarkable protective effect of monoclonal antibodies was noticed in CHO cells infected with N. fowleri. More than 90.6% of the infected CHO cells survived, contrasted with 27% of untreated cells. The overall results in this study suggest that N. fowleri treated with monoclonal antibodies against N. fowleri reduce the mortality and prolong the survival time of the mice when the antibodies are administered before the infection. The protective effect of the monoclonal antibodies is surmised being caused by agglutination of the trophozoites.

Serodiagnosis of Chagas' disease using monoclonal antibody against Trypanosoma cruzi-specific Mr 25,000 antigen

A mouse monoclonal antibody TCF87, prepared previously, was reactive with Trypanosoma cruzi-specific Mr 25,000 antigen regardless of strain. The Mr 25,000 antigen was recognized by all sera from chagasic patients living in different areas of South America, when examined by Western immunoblotting analysis. Although many antigens of T. cruzi epimastigotes were also recognized by sera from patients with leishmaniasis, the Mr 25,000 antigen of T. cruzi did not react with leishmaniasic sera. These results indicate that Mr 25,000 antigen recognized by TCF87 is valuable as a diagnostic antigen for Chagas' disease. When a competition enzyme-linked immunosorbent assay using TCF87 was carried out, all sera from Chagas' disease patients showed positive inhibition. By contrast, all patients with leishmaniasis or other parasitic diseases were scored as seronegative. The present study suggests that competition enzyme-linked immunosorbent assay using monoclonal antibody against the Mr 25,000 antigen of T. cruzi will be useful for serodiagnosis of Chagas' disease in areas where leishmaniasis is co-endemic.