Biomedical subjects
Publications and source records attributed to U Kihm.
The transmission of IBR/IPV virus in imported semen is reported. Some of the inseminated animals showed seroconversion and, in accordance with Swiss law, had to be eliminated. To avoid such cases in international sperm exchange, methods of detecting IBR/IPV virus need to be improved. In the longer term, AI centres must be established in which all bovine stock is seronegative for IBR/IPV.
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Optimum information about potency of a vaccine is achieved by a protection test on the target animal species. However, application of this procedure to routine batch control requires a great number of target animals. In order to reduce the number of such animals, laboratory animal tests or in vitro tests have to be established. These tests must be correlated to target animal protection tests allowing the estimation of the vaccine potency with the same accuracy. With respect to testing the potency of rabies vaccines, alternatives are discussed, i.e. the mouse protection test, induction of antibodies in mice and in vitro tests.
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Eleven dogs were experimentally infected with canine distemper virus and studied for periods of up to 63 days post-inoculation. The responsiveness of lymphocytes in vitro toward phytohemagglutinin, myelin basic protein and galactocerebroside was tested at regular intervals during the course of infection by means of [3H]thymidine incorporation and flow cytometry. All dogs developed a marked decrease of lymphocyte responsiveness toward phytohemagglutinin. Four dogs recovered rapidly from the immunosuppression and did not develop demyelination or had only mild lesions, while two others failed to recover at all and developed severe non-inflammatory demyelinating lesions. The remaining dogs exhibited a slow or partial immune recovery and had various degrees of inflammatory demyelination. Lymphocytes from 2 dogs with demyelination and 2 dogs without myelin lesions responded to myelin antigens. The findings indicate that the degree of immunosuppression in canine distemper virus infection may determine the type of demyelination and autoimmune reactions that occur during the inflammatory stage of demyelination may be epiphenomena.
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Nine dogs with canine distemper encephalitis (CDE) were examined with immunological techniques including demonstration of antibodies against canine distemper virus (CDV) in the serum and against myelin basic protein (MBP) in serum and in CSF. Mitogen stimulation tests of lymphocytes were also done. The brains were examined pathologically and immunoglobulin and C3 were demonstrated in lesions by means of immunohistological techniques. Six dogs with acute CDE had none or low antibody levels against CDV or MBP, and there was no immunoglobulin in demyelinating lesions. Some of these dogs had depressed lymphocyte mitogen responses. Two dogs with chronic CDE showed recovery of lymphocyte mitogen responses. One of these had a significant antibody response against CDV and MBP in the serum. Both dogs with chronic CDE had very high antibody titers against MBP in the CSF and demyelinating lesions contained immunoglobulin. These results suggest that acute demyelination in CDE is probably due to some direct viral activity and that the progression of demyelination in chronic CDE is associated with a local immune response.
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The persistence of immunity induced by a modified live virus rabies vaccine (SAD strain) and an inactivated rabies vaccine combined with panleukopenia vaccine in cats was studied serologically and by virulent rabies virus challenge. The source of challenge virus was a suspension of a dog salivary gland. All 16 cats vaccinated with the inactivated vaccine developed high antibody titres and 15 were protected against the virus challenge. All 8 cats vaccinated with the MLV vaccine produced a serological immune response but 5 cats were not protected against the virus challenge. Some reasons for this phenomenon are discussed.
The high variability that exists in the NIH potency test for inactivated rabies vaccines is well known. To control this variability, the use of a reference preparation of rabies vaccine in parallel with the test vaccines is recommended. However, our data indicate, that the NIH test is more variable when calculating antigenic values using the reference vaccine CRV1 than when calculating only PD50 values. We immunized the mice with a single dose of different vaccine dilutions. As our results suggest, the antibody assay in immunized mice used for the NIH test, seems to be the best possible manner to determine the potency of inactivated rabies vaccines. The antigenic value of the NIH test does not correlate with the antibody status in immunized cats and dogs, but a correlation between antibody titres in mice and dogs appears to exist.
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Staphylococcal protein-A (SpA) is known to interact with the crystallizable fragment (Fc) of IgG molecules from several species. In the present study, SpA coupled to either fluorescein isothiocyanate (FITC) or peroxidase was used in place of antisera to IgG for the fluorescent antibody (FA) techniques and the enzyme linked immunoassay (ELISA). The SpA conjugates produced low background staining when applied in these techniques, and provide a rapid, highly specific and sensitive means for the identification of viral isolates and the detection of serum antibodies. Moreover, SpA is a single reagent that replaces various preparations of anti-gamma globulin against many species. SpA-FITC conjugate was successfully applied for the identification of pseudorabies virus, hog cholera virus, swine vesicular disease virus, transmissible gastroenteritis virus, porcine parvovirus and porcine enteroviruses. Antibody titers against the mentioned viruses could be determined semi-quantitatively in the indirect FA test with SpA-FITC. In our laboratory the ELISA became a routinely practicable serological test for the detection of antibodies only after we introduced SpA-peroxidase as a marker for the IgG.
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