The in vitro biologic effects of T-2 mycotoxin on the immune response of mice was undertaken. Twenty nanograms of toxin abrogated the immune response to the T-dependent antigen sheep RBC, whereas a partial response was observed when 2 ng was used. Analysis of cell culture viabilities indicated that cell death occurred with toxin doses that conincided with the diminished immune responses. A similar decreased response was observed against the T-independent antigen, TNP-lipopolysaccharide, indicating toxic effects on both B and T lymphocyte populations. Delay of toxin administration as much as 116 hours of the 120-hour incubation period still resulted in a substantially diminished immune response, indicating the toxin acts on both the afferent and efferent immune systems. Equal effects were observed for mice of the b, d, and k haplotype, indicating no apparent strain variability in sensitivity to T-2 mycotoxin effects. These results indicated that T-2 mycotoxin can modulate the immune response, and that this modulation is attributable to direct toxic effects on the cells of the immune system.

Serologic virus neutralization tests, indirect immunofluorescence tests, and ELISA, using tissue culture-adapted feline infectious peritonitis virus (FIPV) or feline enteric coronavirus (FECV) were compared for their ability to distinguish specific virus exposure in cats. Sera of specific-pathogen-free cats inoculated with virulent or modified FIPV or FECV were used to compare the sensitivity and specificity of the homologous assays to a heterologous assay that measures antibody reactivity with transmissible gastroenteritis virus of swine. The geometric means of the serologic titers in FIPV and FECV assays were higher for FIPV- or FECV-infected specific-pathogen-free cats than the geometric means of the transmissible gastroente ritis virus assays for most groups. None of the assays was specific enough to discern the virus to which a cat had been exposed. However, the FIPV virus neutralization test appeared to be more sensitive for detection of an early response to FIPV infection than did the FIPV immunofluorescence test or FIPV-ELISA.

Various techniques were used to look for protective, non-cross-reactive antibodies in the sera of cats exposed to virulent feline infectious peritonitis virus (FIPV). Antibodies reactive with feline enteric coronavirus (FECV) from FIPV-exposed cats were adsorbed by several passages over an FECV-Sepharose column. In an ELISA against FECV and FIPV, the activity against both viruses was removed at the same rate; thus, no FIPV-specific antibodies could be identified. By gel electrophoresis-derived ELISA, the responses of cats surviving FIPV exposure were compared with those of cats succumbing to FIPV exposure to determine whether survival could be correlated with an antibody response against a particular virus protein. Results indicated that both groups responded in the same way to the matrix envelope protein and nucleocapsid proteins. Even though the response to peplomer in each group was weak, the survivor group responded better to this protein. Furthermore, the response of this group to the peplomer protein had the highest correlation with virus neutralization titer.