Genus-, subspecies-, and serotype 1-specific antigens of Chlamydia psittaci were characterized by immunoblot analysis, using monoclonal antibodies that recognize 2 C psittaci strains: AB7 isolated from an ewe that had aborted, and iB1 isolated from feces of a healthy ewe. Genus-specific epitopes were detected on lipopolysaccharide, on a 47-kd protein, and on a 27- to 30-kd doublet. Subspecies-specific epitopes were located on a 30-kd protein, and a 80- to 90-kd protein region was identified, which bore subspecies- and serotype 1-specific epitopes. These 80- to 90-kd proteins were highly reactive with serum from ewes that had aborted and could be a useful antigen for diagnosis of chlamydial induced abortion of ruminants.

Poly(methacrylic acid) hydrogels were tested for oral delivery of a vaccine against Pasteurella haemolytica infection in cattle. Culture supernatants of P haemolytica, the most common bacterium associated with pneumonia in cattle, were used as the antigens in the vaccine. Hydrogels containing culture supernatants were administered orally to calves. Calves were then challenge-exposed with virulent P haemolytica. Calves were euthanatized 3 days after challenge exposure. The lungs of each calf were scored for severity and size of pneumonic lesions. Results indicated that vaccinated calves had smaller, less severe pneumonic lesions and lived longer than nonvaccinated calves. These results indicated that hydrogels can be used to deliver vaccines orally to calves to enhance resistance to pneumonia caused by P haemolytica.

An ELISA was developed to detect antibodies to the 41-kd flagellin (P41) of Borrelia burgdorferi in serum obtained from cattle. Absorption studies, immunoblot analysis, immunoelectron microscopy, and correlation of results of the P41-ELISA and the P39-ELISA as well as measurement of the antibody to P41 in calves challenge-exposed with Borrelia theileri were used to assess the specificity of the P41-ELISA. Antigens derived from Escherichia coli, Leptospira interrogans serovar hardjo, and B burgdorferi were used for absorption studies and immunoblot analysis. Antibodies to P41 of B burgdorferi cross-reacted with antigens of E coli, but were not cross-reactive with L hardjo. A value 3 SD higher than the mean of the negative-control population of cattle was defined as the minimum value cutoff value) for a positive result by the P41-ELISA. Use of this value for classification of test results reduced the predicted rate of false-positive results attributable to E coli cross-reactivity to 1%. Immunoblot analysis revealed that test-positive serum from cattle reacted mainly with 41-, 39-, 34-, and 31-kd proteins of B burgdorferi, as well as several smaller proteins. Immunoelectron microscopy revealed that serum from cattle that was test-positive by the P41-ELISA bound to the flagellin and outer membrane of B burgdorferi. Results of absorption studies, immunoblot analysis, and immunoelectron microscopy were correlated and indicated that serum from cattle that was test-positive by P41-ELISA had stronger reactivity to B burgdorferi antigens than to antigens of E coli or L hardjo. The concentrations of antibodies measured by P41-ELISA and P39-ELISA testing were highly correlated [R(2)=0.78]. Calves challenge-exposed with B theileri also had test-positive results by the P-41-ELISA as early as 2 weeks after exposure, but serum antibody concentrations decreased to prechallenge-exposure concentrations by 9 weeks after exposure. We concluded that the P41-ELISA was useful as a screening method to detect B burgdorferi infections in cattle.