Inhibition of virus attachment to CPK cells by monoclonal antibody to transmissible gastroenteritis virus.

Five MAbs, which recognized E2 glycoprotein of TGE virus TO-163 and showed neutralizing activity, were examined to see if they inhibit virus attachment to the susceptible cells (CPK cells). Only one (160/4) MAb blocked the virus attachment to the cells, indicating that the inhibition of virus attachment is one of important mechanisms of neutralizing by antibody.     

Anamnestic immune response of pigs to pseudorabies virus: latent virus reactivation versus direct oronasal and parenteral exposure to virus.

The humoral antibody response of pseudorabies-immune pigs to reactivation of latent pseudorabies virus (PRV) was compared with the response following direct exposure to virulent PRV. Nine pigs that had been vaccinated for pseudorabies and later exposed to virulent virus to establish latent infection were given dexamethasone to reactivate latent virus (3 pigs), were exposed oronasally and parenterally to virulent virus (3 pigs), or were kept as nontreated controls (3 pigs). Sera collected from all 9 pigs just before and 3 weeks after treatment were tested by virus neutralization and radioimmunoprecipitation. The 3 pigs exposed directly to virulent virus and 2 of the 3 pigs given dexamethasone had a 4-fold or greater increase in neutralizing antibody titer. All 6 of these pigs had an increase in precipitating antibody activity. Precipitation patterns changed both quantitatively and qualitatively, especially for virus-coded proteins of relatively low molecular weight (less than 46 K). There were some differences in the precipitation patterns associated with sera of individual pigs. However, there was no clear indication of any difference between the 2 treatment groups and therefore no evidence that reactivation of latent virus is associated with any unique immunologic response that could be detected by radioimmunoprecipitation and used diagnostically. Clinical signs were limited to the 3 pigs that were exposed oronasally and parenterally to virulent virus even though the dexamethasone-treated pigs shed more virus for much longer than did those exposed directly to virus.     

Pathologic changes in ferrets exposed to pseudorabies virus.

Ferrets experimentally infected by various routes with pseudorabies virus were examined for gross and microscopic lesions. Nonsuppurative meningoencephalomyelitis, as well as visceral lesions, occurred. The incubation period seemed related to the viral dose and to the distance between the inoculation site and the central nervous system. The distribution of the lesions in the central nervous system appeared to be closely related to the peripheral nerve pathways from the inoculation sites. Other findings indicated that the lymphohematogenous route could have a role in the dissemination of the virus in infected ferrets.     

Monoclonal antibodies to bovine viral diarrhea virus: cross-reactivities to field isolates and hog cholera virus strains.

Monoclonal antibodies to bovine viral diarrhea virus (BVDV) were examined for binding with a large number of North American BVDV isolates and eight strains of the serologically related pestivirus, hog cholera virus (HCV). No single BVDV monoclonal antibody reacted with all BVDV isolates. The most cross-reactive monoclonal antibody was an anti-p80/p125 antibody which showed a positive reaction with 173 of 180 (96%) North American isolates. From a fewer number of isolates tested, one anti-gp53 monoclonal antibody also showed a high cross-reactivity (94%). All BVDV isolates showed a positive reaction with at least one of the seven monoclonal antibodies in the panel. Thus, the results indicated that a pool of these monoclonal antibodies may be used in place of polyclonal antisera for the detection of BVDV contamination of cell lines or for virus isolation. For HCV, all three anti-p80/p125 monoclonal antibodies reacted positively with all eight virus strains. In contrast, none of the anti-gp53 monoclonal antibodies were reactive to HCV strains. Thus, the anti-gp53 monoclonal antibodies may be useful for distinguishing between usually innocuous BVDV infections and the highly significant HCV infections in swine for foreign animal disease surveillance.     

Immune response in skunks to a vaccinia virus recombinant expressing the rabies virus glycoprotein.

Striped skunks (Mephitis mephitis) were vaccinated with a vaccinia virus recombinant expressing the rabies virus glycoprotein. Virus neutralizing antibodies to rabies virus were present at 14 days postvaccination by the following routes: scarification (6/6), intramuscular (4/4) and intestinal (5/8). Six out of seven skunks that ate vaccine filled baits had virus neutralizing antibodies at 28 days. When challenged intramuscularly with street virus, the survival rates were 5/7 for the bait-fed group, 4/8 for the intestinal group, 3/4 for the intramuscular group, 5/6 for the animals that were scarified, and 0/8 for controls. This is the first report of a high rate of immunization of skunks with a rabies vaccine administered orally.     

A syncytium regression test to detect antibodies to bovine syncytial virus.

A test to detect antibodies to bovine syncytial virus was developed from the observation that syncytia in monolayer cell cultures infected with bovine syncytial virus regress and disappear in the presence of bovine syncytial virus antibodies. The test is useful in monitoring the presence of bovine syncytial virus and bovine syncytial virus antibodies in cattle used in studies on bovine leukosis.     

Production of cattle immunotolerant to bovine viral diarrhea virus.

Inoculation of bovine virus diarrhea virus into 58 to 125 day old fetuses of bovine virus diarrhea virus seropositive pregnant cows, or inoculation of bovine virus diarrhea virus into seronegative cows 42 to 114 days pregnant, may produce clinically normal calves which are persistently infected with the specific isolate of bovine virus diarrhea virus yet seronegative to the homologous and heterologous isolates. Reinoculation of these persistently infected cattle with their homologous isolate produced no neutralizing antibody response to bovine virus diarrhea virus. These persistently infected cattle were immunocompetent as they developed neutralizing serotiters to infectious bovine rhinotracheitis, parainfluenza-3 viruses and agglutinating serotiters to Pasteurella hemolytica .     

Prevalence of feline leukemia virus and antibodies to feline immunodeficiency virus in cats in Norway.

Serum samples from 224 Norwegian cats were analyzed for the presence of feline leukemia virus (FeLV) p27 common core antigen, and for antibodies to feline immunodeficiency virus (FIV). Ninety specimens originated from the serum bank at the central referral clinic at the Norwegian College of Veterinary Medicine, which had been collected during the years 1983-1989; 67 sera were submitted from veterinarian practitioners; while 67 sera originated from cats presented for euthanasia. The cats were classified into one "healthy" and one "sick" group. Only 2.2% of sick cats and 1.2% of healthy cats showed FeLV antigenemia, a finding which is lower than which has been reported from many other countries. The prevalence of FIV antibodies was 10.1% in sick cats and 5.9% in healthy cats. Antibodies to FIV was most prevalent in male cats (14.7%) than in female cats (2.1%), and more prevalent among domestic cats (12.0%) compared to pedigree cats (2.4%). Antibodies to FIV in the cats demonstrated increasing prevalence with increasing age. It may be concluded that FeLV causes minor problems in Norwegian cats, while FIV is present in a similar prevalence to what is reported from other countries.     

Attempts to establish congenital bluetongue virus infections in calves.

Three bovine fetuses were inoculated in utero with approximately 10(3) plaque forming units of type 11 bluetongue virus. The gestational ages of the fetuses at the time of inoculation were 106, 113 and 122 days. They were spontaneously aborted 104, 65 and 109 days later, respectively, and the first and third of these fetuses were recovered. There was no grossly normal cerebral tissue, the meninges formed fluid filled sacs, and the cerebellums were reduced in size. Bluetongue virus was not isolated from the fetuses but the older one had neutralizing antibody. The three dams developed neutralizing antibody to bluetongue virus. The present work supports the observation by others that early fetal infections with bluetongue virus normally result in severe central nervous system damage and not in clinically normal, persistently infected calves.