Antigens of subcellular fractions of Trypanosoma cruzi. III. Humoral immune response and histopathology of immunized mice.

The relation of humoral antibody response to protection was evaluated in mice immunized with whole homogenates of Trypanosoma cruzi or with its flagellar fraction by direct agglutination and indirect fluorescent antibody test as well as by lytic and neutralizing activity against blood trypomastigotes. The results indicated that lytic antibodies were not implicated directly in protection against these trypanosomes. It was evident from histopathologic examination that the higher the degree of protection achieved, the lower the tissue damage observed in the challenged mice. Serum-neutralizing activity was highest in the groups protected most effectively.

[Study of yeast phase Histoplasma capsulatum antigens used for skin tests]. / Estudio de dos antigenos de la fase levaduriforme del Histoplasma capsulatum para pruebas cutaneas.

The results of skin tests with two antigens of the yeast phase of Histoplasma capsulatum are presented. Both antigens were able to fix complement and form precipitating bands in the presence of sera from patients with active histoplasmosis. Their sensitivity was lower than the metabolic antigen usually employed in serology. Results of skin tests obtained with both yeast phase antigens and a standard histoplasmin coincided in animals infected with H. capsulatum. Only one cross reaction was observed in animals inoculated with Paracoccidioides brasiliensis. Skin tests in humans were conducted on patients with and without mycotic disease. The percentages of positive reactions in patients with histoplasmosis were not significantly different between control histoplasmin and whole cell extracts. In the patients with non mycotic diseases the frequency of positive tests varied between 28.8% and 32%, which agrees with previous statistical data for the general population of the area. Equally the positive percentage of 55% and 68% in patients with paracoccidioidomycosis coincided with the results of previous studies. The histological patterns of these skin tests showed that they were produced by cell mediated hypersensitivity. The sensitivity of a whole yeast cell extract was similar to histoplasmin L48, but its preparation was quicker and easier to perform and it had no foreign substances from the culture medium, so we think that it would be easier to standardize it chemically.