Three-week-old weaned and colostrum-deprived neonatal (< 1 day old) pigs were inoculated to determine the pathogenicity of 2 enterotoxigenic Escherichia coli isolates that do not express K88, K99, F41, or 987P adhesins (strains 2134 and 2171). Strains 2134 and 2171 were isolated from pigs that had diarrhea after weaning attributable to enterotoxigenic E coli infection. We found that both strains of E coli adhered in the ileum and caused diarrhea in pigs of both age groups. In control experiments, adherent bacteria were not seen in the ileum of pigs < 1 day old or 3 weeks old that were noninoculated or inoculated with a nonpathogenic strain of E coli. These control pigs did not develop diarrhea. Antisera raised against strains 2134 and 2171 and absorbed with the autologous strain, grown at 18 C, were used for bacterial-agglutination and colony-immunoblot assays. Both absorbed antisera reacted with strains 2134 and 2171, but not with strains that express K99, F41, or 987P adhesins. A cross-reaction was observed with 2 wild-type K88 strains, but not with a K12 strain that expresses K88 pili. Indirect immunofluorescence with these absorbed antisera revealed adherent bacteria in frozen sections of ileum from pigs infected with either strain. We concluded that these strains are pathogenic and express a common surface antigen that may be a novel adhesin in E coli strains that cause diarrhea in weaned pigs.

Systemic and pulmonary antibody responses of calves to Pasteurella haemolytica were evaluated by measuring immunoglobulin production in blood for 9 days and in pulmonary lavage fluid for 7 days after intrapulmonary inoculation. Clinical signs, pulmonary lesions, pulmonary and systemic inflammatory response, and amount of antigen in lavage fluid were used to evaluate the response of calves to challenge with P haemolytica. The pulmonary response consisted of production of IgG, IgE, and IgM antibodies to P haemolytica antigens and a 17- to 68-fold increase of cells in lavage fluid 8 hours after inoculation, with a gradual decrease toward normal. Antibodies of the IgM isotype to P haemolytica were demonstrated as early as 8 hours through 7 days after inoculation in 3 of 3 calves. Of the anti-P haemolytica isotypes, IgM was found in the highest concentration. In all of the inoculated calves, IgE was found 1 to 2 days after inoculation, and IgG was found in 2 of 3 inoculated calves from day 1 through 7 after inoculation. Detection of IgG correlated with smaller pulmonary lesions. Immunoglobulin A was not detected in lavage fluid. Serum was evaluated for IgG and IgM antibody response to P haemolytica. Specific IgM was detectable 5 days after inoculation, and IgG was detectable 7 days after inoculation. Pasteurella haemolytica antigens were not detected in serum or plasma. A transient increase in neutrophil count was found 8 hours after inoculation, with return to baseline values by 24 hours after inoculation. Antigen was detected in lavage fluid by use of monoclonal antibodies against selected P haemolytica capsular antigen, outer membrane antigens, and leukotoxin in all inoculated calves 8 hours after inoculation. The monoclonal antibody specific for P haemolytica capsule provided the best detection of antigen. The other monoclonal antibodies detected antigen, but were less consistent.

The relation between average duodenal mast cell count, duodenal mucosal mast cell numbers, duodenal connective tissue mast cell numbers, circulating basophil numbers, heterophil-to-lymphocyte ratio, and lesion score were studied to gain an understanding of the events that may lead to intestinal lesion formation associated with hemorrhagic enteritis virus (HEV) infection. Changes in vascular permeability in the duodenum in birds inoculated with HEV were examined, using colloidal carbon and ferritin as vascular markers. Turkeys inoculated with HEV had significantly (P < 0.05) higher duodenal mast cell counts than did noninfected controls. Birds inoculated with HEV had significantly (P < 0.05) more mucosal mast cells than did phosphate-buffered saline solution-inoculated birds. Connective tissue mast cell and basophil numbers were unaffected by viral inoculation. Thermal stress did not have significant effect on lesion severity, but did increase number of birds that developed the characteristic intestinal lesions. The heterophil-to-lymphocyte ratio was significantly (P < 0.05) higher in HEV-inoculated birds, compared with phosphate-buffered saline solution-inoculated controls. Increase in vascular permeability was only detected in HEV-inoculated birds with intestinal lesions. Results indicate that mast cells, and the vasoactive mediators contained within mast cells, may be important in the early manifestation of HEV infection. They also provide a possible mechanism through which biochemical and physiologic changes characteristic of HEV infection can occur.

The 43 monoclonal antibody raised against feline T cells was found to react with a single-chain glycoprotein of Mr 72,000 that is present on most thymocytes, 60% of lymph node cells, 20% of splenocytes, and 45% of blood mononuclear cells. All CD4+ and CD8+ T cells were found to express the 43-reactive determinant, as did a small subpopulation of CD4-/CD8-/IgM- lymphocytes in the periphery. The 43-reactive determinant was not detected on B cells, macrophages, or other types of blood cells. The 43 antigen was phosphorylated in resting and activated T cells. Its expression was upregulated by stimulation with phorbol myristate acetate and with phytohemagglutinin. When added to concanavalin A-stimulated T-cell cultures in low concentrations, the 43 antibody was found to augment mitogenesis. The data indicate that this antibody may identify a CD5 homologue on feline T cells.

A panel of monoclonal antibodies (MAb) developed against Mycoplasma gallisepticum strain PG31 was used to probe the antigenic profiles of 5 recognized strains (PG31, R, S6, F, A5969) and 6 field isolates of M gallisepticum. Monoclonal antibody G9 predominantly recognized antigens at apparent molecular mass positions of 90 to 98 kDA. The MAb reacted with all strains and isolates, but the molecular mass position of the antigens varied among some mycoplasmas. Monoclonal antibody G12 reacted with all strains and isolates of M gallisepticum and had an identical banding pattern. However, MAb G10 and G11 reacted selectively only with a limited number of strains and/or isolates. Surface distribution of the MAb-recognized antigens was revealed by immunoelectron microscopy. Partial physicochemical characterization of MAb G9-recognized antigens identified glycopeptide characteristics. Monoclonal antibody G9 reacted with surface antigens and, hence, participated in agglutination of M gallisepticum. However, the degree of agglutination varied among the various strains and isolates, indicating a quantitative or conformational limitation or an alteration in the anomeric expression of the epitopes. Antigenic variation in M gallisepticum may be mediated by immunologic selective pressures, or a proclivity for habit niche in the host.

Polypeptides from whole cell preparations of Pasteurella multocida serotypes A:12 and A:3 were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transferred to nitrocellulose paper. Antigens were detected by immunoblot analysis, using sera from 3 groups of rabbits. Sera were obtained from rabbits inoculated intranasally with P multocida serotype A:12 or A:3, from rabbits maintained in a rabbitry with enzootic P multocida A:12 infection, and from rabbits maintained in a rabbitry with enzootic P multocida A:3 infection. Immunoblot analyses of pre- and postinoculation sera from experimentally infected rabbits, using serotype A:12 antigen, revealed 3 polypeptides with approximate molecular mass of 28, 30, and 37 kDa that consistently detected antibodies after P multocida-induced infection. Sera from rabbits naturally infected with either serotype, tested against serotype A:12 and A:3 antigens, detected the same polypeptides in both serotypes. Thus, immunologic reactivity to these polypeptides may be useful for serologic detection of P multocida infection.

Determination of antibodies to specific nuclear antigens, termed extractable nuclear antigen (ENA), was investigated in healthy dogs and in dogs with autoimmune, inflammatory, and neoplastic diseases. Using a counter-immunoelectrophoresis method, the dogs' sera were tested for antibodies against the nuclear antigens single-stranded DNA, Sm, Ro, La, ribonucleoprotein, Scl, and proliferating cell nuclear antigen. Antibodies to the Ro antigen were found in 1 dog with discoid lupus erythematosus, in 1 dog with pemphigus erythematosus, and in 1 dog with facial pyoderma and chronic superficial keratitis. In 15 dogs, antibodies were detected to ENA, but the precipitin lines were too weak to identify the specific ENA. These antibodies were found in some dogs with systemic lupus erythematosus, discoid lupus erythematosus, pemphigus erythematosus, dermatomyositis, vitiligo, lymphoma; in the dog with facial pyoderma and chronic superficial keratitis; and in 1 healthy dog. The highest percentage of dogs with antibodies to ENA in a large series (> 8) of this study was in dogs with systemic lupus erythematosus (4 of 13; 31%).

A commercially available Salmonella bacterin was administered to Holstein calves starting at 1 to 19 weeks of age. Serum samples were obtained before administering bacterin and at 2-week intervals thereafter. An ELISA with Salmonella dublin lipopolysaccharide (LPS) or S dublin whole cells as antigen, was used to measure specific IgG and IgM responses. Antibody responses to LPS were not detected from calves < 12 weeks old inoculated with killed bacterin. Immunoglobulin responses to whole-cell antigen were detected from all age groups of calves inoculated with the same killed Salmonella bacterin. Calves < 11 weeks old are able to produce immunoglobulins to some whole-cell antigens, but are unable to produce anti-LPS immunoglobulins when inoculated with killed Salmonella bacterin. This age-related response to killed Salmonella antigens may account, in part, for increased susceptibility to salmonellosis in calves < 12 weeks old. In comparison to the response for killed antigen, 8 calves given modified-live aromatic-dependent S dublin bacterin at 1 to 3 weeks of age had detectable anti-LPS immunoglobulin after immunization, although the response was not as rapid and was of a lesser magnitude than that of older calves given killed Salmonella bacterin.

Anecdotal descriptions of atypical FeLV infections, wherein standard clinical ELISA or immunofluorescence testing fails to detect active infections, suggest that an unknown proportion of FeLV-infected cats may go undetected. In this study, 127 viremic and nonviremic cats experimentally inoculated with FeLV were evaluated at necropsy for atypical expression of FeLV antigen. Results from viremic cats were in accordance with results of earlier studies on the pathogenesis of FeLV infection in cats, wherein antigen was found in lymphoid and epithelial tissues. Differences in time course or tissue distribution of viral antigen in some cats appeared to be attributable to the challenge virus preparations, consisting of cell-free tumor homogenate or infectious plasma. It was discovered that 5 of 19 of the FeLV challenge-exposed cats that were nonviremic had FeLV-specific antigens in select tissues (bone marrow, spleen, lymph node, and small intestine) 6 to 75 weeks after inoculation. These results indicated an additional category of possible outcomes for cats exposed to FeLV. Localized FeLV infection, as described here, may explain the discordance between clinical disease and laboratory testing for FeLV.

Three-week-old weaned and colostrum-deprived neonatal (< 1 day old) pigs were inoculated to determine the pathogenicity of 2 enterotoxigenic Escherichia coli isolates that do not express K88, K99, F41, or 987P adhesins (strains 2134 and 2171). Strains 2134 and 2171 were isolated from pigs that had diarrhea after weaning attributable to enterotoxigenic E coli infection. We found that both strains of E coli adhered in the ileum and caused diarrhea in pigs of both age groups. In control experiments, adherent bacteria were not seen in the ileum of pigs < 1 day old or 3 weeks old that were noninoculated or inoculated with a nonpathogenic strain of E coli. These control pigs did not develop diarrhea. Antisera raised against strains 2134 and 2171 and absorbed with the autologous strain, grown at 18 C, were used for bacterial-agglutination and colony-immunoblot assays. Both absorbed antisera reacted with strains 2134 and 2171, but not with strains that express K99, F41, or 987P adhesins. A cross-reaction was observed with 2 wild-type K88 strains, but not with a K12 strain that expresses K88 pili. Indirect immunofluorescence with these absorbed antisera revealed adherent bacteria in frozen sections of ileum from pigs infected with either strain. We concluded that these strains are pathogenic and express a common surface antigen that may be a novel adhesin in E coli strains that cause diarrhea in weaned pigs.