The efficacy of an intranasal haemorrhagic septicaemia vaccine containing live gdhA derivative Pasteurella multocida B:2 was tested in buffaloes in Sabah. Sixty buffaloes, kept grazing in the field with minimal human intervention were devided into three groups of 20 buffaloes per group. Buffaloes of group 1 were exposed intranasal to 5 ml vaccine containing 10(6) CFU/ml of live gdhA derivative P multocida B:2. Buffaloes of group 2 were not exposed to the vaccine but exposed to PBS and were allowed to commingle and graze in the same field as the buffaloes of group 1 while buffaloes of group 3 were similarly exposed to PBS and were grazing separately. Booster was on group 1, two weeks later. Twelve months after the first vaccination, three buffaloes from each group were brought into the experimental house and challenged subcutaneously with 10(9) CFU/ml of live wild-type P multocida B:2. All challenged buffaloes of groups 1 and 2 survived with only mild, transient signs while all control unvaccinated buffaloes developed severe signs of haemorrhagic septicaemia and were euthanased between 28 hours and 38 hours postchallenge with signs and lesions typical of haemorrhagic septicaemia. These data showed that the gdhA mutant strain, given intranasally as two doses two weeks apart, successfully induced systemic immunity in exposed buffaloes and also led to spread of vaccine strain to the in-contact animals, where it acted as an effective live vaccine to protect both exposed buffaloes and in-contact buffaloes against challenge with the virulent parent strain.
Formalin-fixed, paraffin wax-embedded tissues of three Malaysian farm pigs naturally infected with Nipah virus were used to investigate the value of anti-Nipah virus mouse monoclonal antibodies (Mabs) and rabbit polyclonal antibody for immunohistochemical diagnosis. Mabs 11F6 and 12A5 gave intense immunolabelling in lung tissue that had been fixed in 10% neutral buffered formalin for about 4 years, whereas the reactivity of Mabs 13A5 and 18C4 and polyclonal antibody was reduced significantly by long-term formalin fixation. Immunohistochemical examination of Malaysian farm pig samples with Mab 11F6 confirmed the affinity of Nipah virus for respiratory epithelium, renal glomerular and tubular epithelium, meningeal arachnoidal cells, and systemic vascular endothelium and smooth muscle. In addition, Nipah virus antigens were identified in laryngeal epithelial cells, Schwann cells of peripheral nerve fascicles in the spleen, and endothelial cells in the atrioventricular valve. The study demonstrated the value of Mabs 11F6 and 12A5 for the immunohistochemical diagnosis of Nipah virus infection in pigs.