Evans, H. B.

English

Immunity to Pasteurella haemolytica was studied
using models of P. haemolytica infection in both lambs and
mice.

Immunisation of specific pathogen-free lambs with a
. vaccine containing a sodium salicylate extract of
P. haemolytica type A1 protected against challenge with
P. haemolytica type A1, superimposed upon infection with
parainfluenza type 3 virus. Lymphocyte transformation
responses of peripheral blood leucocytes from vaccinated
lambs increased markedly after challenge. The passive
transfer of hyperimmune serum, produced by repeated
vaccination of lambs with the same vaccine, did not protect
recipients from challenge. Serum from vaccinated lambs
had a bacteriostatic effect upon P. haemolytica in vitro,
although this serum failed to facilitate phagocytosis of
P. haemolytica by alveolar macrophages in vitro.

Two models of P. haemolytica infection in mice were
investigated. Intranasal infection of mice with P. haemollytica
caused lesions in the lung 3 days later. Bacteria
were cleared from the'lung by 48 hours after infection, and
because similar lesions were produced by the introduction of
heat-killed P. haemolytica, this model was not investigated
further.

P. haemolytica introduced to mice intraperitoneally in
gastric mucin multiplied in the liver and spleen. The
effect of vaccination with various extracts of P. haemolytica 
upon growth in the liver was investigated. Vaccines
containing sodium salicylate extracts of P. haemolytica
types Al, A6, A8, A11 and T10 protected against challenge
with homologous strains, and little cross-protection between
the various strains was observed.

The model of intraperitoneal challenge of mice was used
to investigate the commercial Pasteurella vaccine, Carovax.
When given 12 or 24 hours before challenge, the vaccine
protected against challenge with P. haemolytica type A1,
and also Escherichia coli, indicating that protection was
non-specific. When the vaccine was given 1 hour, 48 hours,
7 days or 14 days before challenge with. P. haemolytica
type A1, no such protection was observed.

An enzyme-linked immunosorbent assay was developed for
detection of antibodies to P. haemolytica in the sera of
vaccinated mice. There was considerable cross-reaction
between sera from mice immunised with sodium salicylate
extracts of the different types of P. haemolytica

A Study of the Mechanisms of Immunity to Pasteurella Haemolytica Infection

Abstract

Similar works

Full text

Available Versions

Edinburgh Research Archive