Protective effect of inactivated bovine herpesvirus-1 in calves experimentally infected with bovine herpesvirus-1 and Pasteurella haemolytica.
The protective effect of an inactivated whole-virion bovine herpesvirus-1 (BHV-1) immunising inoculum, without adjuvant, against viral-bacterial respiratory disease was studied in three experimental treatment groups of five calves each. One group was boosted 14 days after the first vaccination and at this time the second group received their initial inoculation. Seven days later, calves were challenged with BHV-1 in aerosol and four days after this challenge all calves were exposed to Pasteurella haemolytica A1 in aerosol. Among the three groups, differences in rectal temperature responses four days after viral challenge (P less than 0.01) did not relate to protection. However the main response variable, viral-bacterial pneumonia, was reduced in boosted calves (P less than 0.05).
Bovine herpesvirus-1 vaccination against experimental bovine herpesvirus-1 and Pasteurella haemolytica respiratory tract infection: onset of protection.
The onset of protection offered by intranasal vaccination with attenuated bovine herpesvirus-1 (BHV-1) was studied in 18 calves given a virulent BHV-1 aerosol challenge inoculum and an aerosol challenge exposure to Pasteurella haemolytica. Calves challenge exposed with virus 3, 7, 11, 15, or 19 days after vaccination and challenge exposed 4 days later with Pasteurella haemolytica did not develop viral-bacterial pneumonia, whereas 2 of 3 control calves died of fibrinous bronchopneumonia 40 and 60 hours after the bacterial aerosol and the 3rd control calf had similar lesions. All vaccinated and control calves had detectable amounts of interferon at the time of viral challenge exposure. Protection was observed before detection of neutralizing antibodies to BHV-1 in nasal secretions or in serum. Protection was therefore present from day 3 through day 19 after vaccination, but the mechanism could not be explained completely by neutralizing antibody or interferon.
Pharmacology of bovine pulmonary vein anaphylaxis in vitro
1 The bovine pulmonary vein contracts in response to acetylcholine, histamine, 5‐hydroxytryptamine and bradykinin. The tissue is particularly sensitive to 5‐hydroxytryptamine (>0·1 ng/ml). Specific Schultz‐Dale reactions were elicited in the pulmonary vein in response to horse plasma. 2 The Schultz‐Dale reaction is inhibited both by antihistaminics and by the anti‐5‐hydroxytryptamine agent methysergide, but not by atropine. 3 Sodium meclofenamate inhibited anaphylactic contraction but showed a strong tendency to antagonize many agonists indiscriminately. 4 Disodium cromoglycate (DSCG: 100 μg/ml) which inhibits some immunological reactions of mast cells, and diethylcarbamazine citrate (DECC: 50 μg/ml) which inhibits slow‐reacting substance of anaphylaxis (SRS—A) elaboration, each inhibited anaphylaxis incompletely (50% or less). However, a combination of DSCG and DECC virtually abolished the Schultz‐Dale reaction in this preparation. It is tentatively suggested that the component of the anaphylactic contraction which is resistant to cromoglycate but sensitive to diethylcarbamazine could be due to SRS—A. 5 The bovine pulmonary Schultz‐Dale reaction appears to be a complex interaction of histamine, 5‐hydroxytryptamine, SRS—A and possible other agents including kinins.