Interference activity of bovine herpes virus 1 strains against Aujeszky's disease virus in cell cultures.

The interference-inducing activity of different low- and high-virulence strains of bovine herpes virus 1 (BHV-1) against Aujeszky's disease virus was studied by a parallel titration on permissive and non-permissive cell culture. The low-virulence BHV-1 strains possessed better interference-inducing activity than the high-virulence strains. An interference blocking test (IBT) was developed for the detection of BHV-1 antibodies in bovine sera. Comparative results of IBT and the virus neutralisation reaction did not show statistically reliable differences.

Skin virulence of attenuated pseudorabies virus (PRV) strains.

After intradermal inoculation of the attenuated pseudorabies virus (PRV) strains, Bartha, MK35 (gI+) and MK35-T-2 (gI-) to rabbits, they caused local inflammatory nodules with oedema reddiness and necrosis. The specifity of these reactions was confirmed by their inhibition with anti-PRV serum. The minimal dose that caused visible skin reaction was about 10(2) TCID50/ml for Bartha and MK35-T-2 (gI-) strains and over 10(4) TCID50/ml for the MK35 (gI+) strain. It is assumed that the established residual skin virulence can serve as an additional distinction marker for attenuated PRV strains.

The immunological response of calves after submucosal application of a live vaccine against parainfluenza-3- and adenovirus. (Brief report).

Using submucosal application of live attenuated vaccine against parainfluenza-3-virus and cattle adenovirus within the nasal opening, calves reacted with the formation of secretory (local) and serum antibodies of significantly higher titers than are received using subcutaneous application. The same vaccine induces interferon activity in the serum and nasal secretion after submucosal vaccination. Adenovirus antigen is a stronger interferon inducer than para-influenza-3-virus.

Immunization against mucosal disease--bovine viral Diarrhea (MD-BVD) in calves applying lapinized vaccine against swine fever and a modified live virus of MD-BVD.

Calves vaccinated with the modified strain C24V react by creating neutralizing antibodies in high titres and are resistent to infection while non-immunized calves manifest the clinical symptoms of MD-BVD. Calves, vaccinated with the lapinized strain "K" of the SF virus react by creating neutralizing antibodies in low titres against the vius of MD-BVD and manifest no apparent clinical symptoms after challenge with the virulent strain MD-BVD.

[Immunological correlations between 2 strains of mucosal disease virus diarrhea (short report]. / Uber die immunologischen Beziehungen zwischen zwei Virusstämmen der Mucosal-Disease-Virus-Diarrhoe (Kurze Mitteilung)

Cross-neutralization tests of the C24V strain and the "Kotschmar" strain provided evidence that the two strains are serological variants. Independenthy of quantitative serological differences, these strains had a better immunizing action in calves against a virulent strain of MD/VD virus. This virulent strain evidently formed a third serological variant, because when calves were infected with it, there was a decrease in the serological differences between antibodies. A practical conclusion is that diagnostic serological testing using only one strain is unlikely to detect all the infected animals, particularly those with low titres of antibody. In the presence of complement the neutralizing capacity of immune serum increased and, in the case of low antibody titres, serological differences between strains decreased. Therefore the complement-dependent neutralization test with at least two strains of virus is recommended for use in diagnostics.

Kinetics of neutralization of two strains of Myxovirus Parainfluenza 3 in the presence of complement and anti-gammaglobulin-serum.

Using the kinetics of neutralization, it was established that two strains of Myxovirus Parainfluenza 3 of cattle and sheep origin which are immunologicaly identical have a different sensitivity to early neutralizing antibodies of reconvalescent calf sera. Complement-dependent neutralizing antibodies, supplied by adding 5% guinea pig serum to the calf serum, appear earlier than the usual neutralizing antibodies. Goat anti-cattle gammaglobulin serum decreases the neutralizing activity of early reconvalescent serum and release some of the neutralizing virus from the virus-antibody complex. It is believed that the lability of the virus-antibody complex depends not only on the activity of the antibody, but also on some properties of the strains. The addition of complement stabilizes this complex. The previous addition of adenovirus antigen to bivalent cattle serum against Myxovirus Parainfluenza 3 and cattle adenovirus, decreases the complement-dependent neutralizing antibody of the serum against Myxovirus Parainfluenza 3. It is suggested that this is the possible mechanism for the mutual activation of mixed virus infections.