Serologic comparison of four isolates of rabbit hemorrhagic disease virus.

An acute, fatal disease of rabbits, termed Rabbit Hemorrhagic Disease (RHD), has occurred in Asia, Europe, and North America since 1984. The clinical signs, pathologic lesions, and epidemiologic features seen in the various outbreaks were very similar. Although RHD virus (RHDV) was initially characterized as a picornavirus or a parvovirus, it is now proven to be a calicivirus. This study compared the immune responses generated following the vaccination and challenge inoculation of rabbits with isolates of RHDV obtained from Italy, Korea, Mexico, and Spain. The cross-reactivity of antisera was demonstrated using the hemagglutination inhibition (HI) test. There were minimal differences between the homologous and heterologous responses. Statistical analysis of the HI results showed no difference between the isolates within the Italian, Korean, and Spanish vaccinate groups. The difference obtained between the Mexican and Korean antigens within the Mexican vaccinate group is likely due to individual animal variation. The similarity of the isolates was also demonstrated using a monoclonal antibody directed against RHDV.

Laboratory diagnosis of African horse sickness: comparison of serological techniques and evaluation of storage methods of samples for virus isolation.

Five serological methods of diagnosing African horse sickness were evaluated, using a battery of serum samples from experimental horses vaccinated and challenged with each serotype of African horse sickness virus (AHSV1 through AHSV9): agar gel immunodiffusion (AGID), indirect fluorescent antibody (IFA), complement fixation (CF), virus neutralization (VN), and enzyme-linked immunosorbent assay (ELISA). The 5 tests were also compared using a panel of field samples, convalescent equine sera with antibodies to domestic equine viral diseases, and sera from horses awaiting export. The ELISA described in this paper was group specific. It did not require calibration with a standard positive serum but did yield elevated values with negative sera that were repeatedly frozen and thawed or heat inactivated. The IFA test was sensitive but could not be used on some field sera as the control cells exhibited fluorescence, possibly due to the animal being recently vaccinated with cell culture material. Sixty-two experimental sera were compared by VN, CF, AGID, and ELISA. Forty sera, 10 positive and 30 negative, were correctly classified by the 5 serologic assays. The 22 remaining sera gave mixed reactions. The AGID had no false positive results but had false negative results for up to 20% of the samples, depending upon the comparison. The VN, CF, and ELISA were similar in their variability. The length of time that virus could be recovered from a viremic blood sample was compared in an evaluation of storage methods for virus isolation samples. Washed erythrocytes were held at 4 C, washed erythrocytes plus stabilizer were held at -70 C, and blood that was drawn into a preservative (oxalate/phenol/glycerol) was held at 4 C.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of gamma irradiation on reactivity of rinderpest virus antigen with bovine immune serum in enzyme-linked immunosorbent assays and virus neutralization and indirect fluorescent-antibody tests.

Gamma irradiation effectively inactivated gradient-purified rinderpest virus. Irradiated antigen and sera remained functional in enzyme-linked immunosorbent assays, virus neutralization tests, and indirect fluorescent-antibody tests. Irradiation, however, led to a dose-dependent decrease in reactivity, particularly significant (P < 0.05) when both reagents were irradiated. To avoid false-positive reactions, only one reagent (serum or antigen) may be irradiated.