Deisy Perdomo

85-kDa protein of Trypanosoma cruzi purified by affinity chromatography used in the multiple antigen binding assay (MABA) for the diagnosis of T. cruzi infection in a Venezuelan rural community.

No ideal test exists for Chagas’ disease, and better diagnostic strategies are needed. We determined the diagnostic utility of an 85-kDa Trypanosoma cruzi protein in a multiple antigen binding assay (MABA). A standardized MABA test based on concentrated trypomastigote excretory–secretory antigen (TESA) and an 85-kDa purified protein showed 100% sensitivity and specificity. In field conditions, 6/66 individuals tested in a region not thought to be endemic (Rio Brito) were identified as seropositive for T. cruzi infection with our MABA test. In parallel, an enzyme-linked immunosorbent assay based on fixed epimastigotes detected 7/66 positives, which were independently confirmed. These data suggest that the 85-kDa and TESA proteins could be used in the MABA format as a complementary tool for the diagnosis of latent Chagas’ disease. High anti-T. cruzi antibody detection rates, poor knowledge of Chagas’ disease and its vector, and the demonstration of infected vectors in the study community all suggest a significant risk of reemergence of T. cruzi infection in this region of Venezuela.

A variant of arrestin-1 binds rod outer segment membranes in a light-independent manner

A 50-kDa-polypeptide band peripherally bound to retinal rod outer segment (ROS) membranes was purified by anion-exchange chromatography. When the 50-kDa protein was compared with purified arrestin-1, it was observed that: (1) both proteins comigrated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and were recognized by either anti-50-kDa protein polyclonal antibodies or anti-arrestin-1 monoclonal antibodies; (2) protein fragments and peptide fingerprint maps obtained following limited and complete proteolysis with specific proteases were very similar for both molecules; and (3) several chromatographically-purified tryptic peptides from the 50-kDa protein possessed the same amino acid composition as tryptic peptides deduced from the reported arrestin-1 primary structure. Consequently, arrestin-1 and the purified 50-kDa protein must correspond to variants of the same molecule. However, in contrast to arrestin-1 that associated to the ROS membranes only in the presence of light and ATP, the 50-kDa protein interacted with the ROS membranes in a light-independent manner, either in the presence or absence of ATP. These results clearly established that phosphorylated and illuminated rhodopsin is not the membrane anchor for this variant of arrestin-1.