Biomedical subjects

H B Evans

Publications and source records attributed to H B Evans.

22 records · Page 2Linked to original sources

PubMed1979

Inability of passively acquired antibody to protect lambs against experimental pasteurellosis.

An experimental model of pneumonic pasteurellosis in sheep was used to investigate the role of serum antibody in resistance to this disease. Lambs which had been vaccinated with a sodium salicylate extract of Pasteurella haemolytica type A1 were protected against challenge with PI3 virus followed by P. haemolytica type A1 7 days later. The majority of untreated lambs and lambs which had received either 200 ml of antiserum to P. haemolytica or 200 ml of control serum intraperitoneally 18 h before infection with P. haemolytica type A1 succumbed to the challenge. Lymphocytes from vaccinated lambs showed a specific proliferative response when exposed to P. haemolytica type A1 sodium salicylate extract, and this response increased after exposure of these animals to P. haemolytica type A1 in aerosol. The results indicate that the humoral immune response alone is incapable of affording protection against experimental pasteurellosis and that cell-mediated immunity may play an important part in resistance to this disease.

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PubMed1979

Non-specific resistance of mice to Pasteurella haemolytica.

A technique for challenge infection of mice with Pasteurella haemolytica is described. Mice were challenged intraperitoneally with P haemolytica in gastric mucin, and viable counts were performed 6 h later on liver suspensions. Viable counts of P haemolytica in the livers of unvaccinated control mice had increased 6 h after infection. Mice were injected subcutaneously with a commercial pasteurella vaccine at various time intervals before challenge. In those given vaccine two weeks, one week, 48 h and 1 h before challenge, viable counts of P haemolytica in the liver increased as for control mice. However, if the time interval between administration of vaccine and challenge was 12 or 24h, viable counts of P haemolytica in the liver decreased after challenge. Subcutaneous inoculation with the nonbacterial components of the vaccine 24 h before challenge did not cause such an effect. Inobulation with the vaccine 24h before challenge with Escherichia coli resulted in an increase in the LD50 for that organism, indicating that the effect is probably non-specific.

Animals↗

PubMed1979

A mouse model of Pasteurella haemolytica infection and its use in assessment of the efficacy of P haemolytica vaccines.

A method for infecting mice with Pasteurella haemolytica is described. Mice were inoculated intraperitoneally with P haemolytica incorporated in gastric mucin, killed at various time intervals thereafter and viable counts of bacteria were performed on liver suspensions. P haemolytica grew at an exponential rate in the livers of normal mice. Mice vaccinated against P haemolytica A1 were protected against homologous challenge and viable counts decreased rapidly in their livers. Mice given trivalent P haemolytica vaccine (types A1, A2 and A6) were protected against challenge with P haemolytica types A1 and A6, but were not protected against challenge with types A2 and A9. These results correlate with findings in sheep.

Animals↗

PubMedDate not supplied

Enhancement (by native type II collagen) of the humoral immune response to native type I collagen in the rat.

Both native type II collagen and rabbit IgG were good immunogens in the rat when emulsified in incomplete Freund's adjuvant but native type I collagen and denatured type II collagen were not. Both native type II collagen and rabbit IgG had an enhancing effect upon the production of antibodies to native type I collagen when rats were immunised with a mixture of native type I collagen and either of these immunogens but denatured type II collagen did not have this effect. These immunogens, however, did not enhance the production of antibodies to ovalbumin when emulsified with it. Although both native type II collagen and rabbit IgG showed this enhancing effect with native type I collagen, only rats immunised with native type II collagen or mixtures containing native type II collagen developed arthritis. Thus, a specific immune response to collagen rather than this enhancing effect appears to be necessary for the induction of arthritis.

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