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Biomedical subjects

P W Wells

Publications and source records attributed to P W Wells.

At least 19 recordsLinked to original sources
PubMed1985

Protection of lambs against enteric colibacillosis by vaccination of ewes.

Pregnant ewes were vaccinated twice, seven weeks and three weeks before lambing, with a multivalent formalin-killed Escherichia coli vaccine containing an added K99, F41 antigen preparation. Lambs born to vaccinated and unvaccinated ewes were exposed to oral infection with E coli B44 (09:K30, K99, F41). All 10 lambs from vaccinated ewes were protected whereas all 10 control lambs developed severe diarrhoea and five died or were killed in extremis. In the following year, previously immunised ewes were given a single dose of the vaccine two weeks before lambing. Eleven of their 12 lambs were protected against a similar challenge, which caused the death of six of eight control lambs and severe diarrhoea in the two survivors. Higher levels of antibody to the K99, F41 preparation were detected by enzyme-linked immunosorbent assay in the serum and colostrum from vaccinated ewes and in the serum of their lambs when compared with similar samples from control ewes and lambs.

Animals↗
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.

Animals↗
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↗
PubMed1979

A serological comparison of Pasteurella haemolytica vaccines containing different adjuvants.

Five adjuvants were compared for their ability to enhance the serological response of sheep to capsule extract of Pasteurella haemolytica biotype A serotype 6. Vaccines of this antigen were inoculated with incomplete Freund's adjuvant, complete Freund's adjuvant, incomplete Freund's adjuvant containing a water soluble extract of Mycobacterium tuberculosis, aluminium hydroxide gel or a combination of aluminium hydroxide gel and incomplete Freund's adjuvant. This latter vaccine induced significantly higher titres of antibody as measured by an indirect haemagglutination test than did any of the other vaccines. The aluminium hydroxide gel alone was shown to be the poorest adjuvant. The local reactions at the sites of inoculations produced by the aluminium hydroxide gel in incomplete Freund's adjuvant vaccine were not severe and were not detectable beyond one month after vaccination in the majority of the sheep.

Adjuvants, Immunologic↗
PubMed1978

Antibody titres to lamb rotavirus in colostrum and milk of vaccinated ewes.

Ewes were vaccinated two to three weeks prior to mating with a formalin-treated preparation of lamb rotavirus. The colostrum and milk produced by vaccinated ewes after the subsequent pregnancy were shown to contain significantly higher titres of antibody to the virus than did mammary secretions from non-vaccinates. The virus neutralising antibody activity was associated with IgG in both colostrum and milk. However, IgG concentrations in the mammary secretions of vaccinates and non-vaccinates did not differ. It is suggested that vaccination of the dam may be of value in protecting the suckled neonatal lamb against rotavirus infection.

Animals↗
PubMed1978

The immunoprophylaxis of of rotavirus infections in lambs.

The effect of colostrum or serum feeding on subsequent rotavirus infections was investigated in neonatal gnotobiotic lambs. Immunity after feeding colostrum did not depend on absorption of passively acquired antibody into the circulation. Protection against clinical disease depended on the volume of colostrum ingested. The protection afforded by feeding serum was specific, since serum free of rotavirus antibody failed to confer protection. Immune serum fed at a rate of 2.5 ml per kg twice daily protected against rotavirus infection. Also, it was shown by intraperitoneal inoculation of immune serum that protection could occur in the absence of ingested antibody, presumably by transfer of antibody into the gut. The implications of these findings for immunoprophylaxis of rotavirus diarrhoea in lambs and calves are discussed.

Animals↗
PubMed1978

The effect of vaccination on titres of antibody to rotavirus in colostrum and milk.

The continued presence of antibody to rotavirus in the gut of the neonatal ruminant has been shown to be important in protecting against clinical disease associated with rotavirus infections. This effect is dependant upon the amount of antibody included in the diet. Titres of antibody to rotavirus may be relatively high in ruminant mammary secretions immediately after parturition but decline rapidly over the course of the first day. The influence of vaccination on the titres of antibody, the concentrations of immunoglobulin and their respective of decline in the mammary secretion following parturition has been studied. Ewes vaccinated two to three weeks prior to mating with an inactivated preparation of lamb rotavirus produced colostrum and milk after the subsequent pregnancy which contained significantly higher titres of antibody to the virus than did the mammary secretions from non-vaccinates. The antibody activity appears to be associated with IgG and it is suggested that vaccination may be of value in the alleviation of neonatal diarrhoea associated with rotavirus infection in cattle and sheep.

Animals↗
PubMed1978

Reactivity of ovine lymphocytes to phytohaemagglutinin and pokeweed mitogen during pregnancy and in the immediate post-parturient period.

Lymphocytes from sheep in late pregnancy and at parturition showed markedly impaired proliferative responses to phytohaemagglutinin (PHA) in vitro when cultures were supplemented with foetal bovine serum (FBS), as compared to the responses of lymphocytes from non-pregnant sheep, sheep at 40 days of gestation and sheep at 80 days of gestation. Similar responses to PHA were observed when the medium was supplemented with autologous plasma (AP), although the responses were of a lower order. In both cases elevated responses to PHA were apparent at 10 days post-parturition. The response with FBS was more marked than with AP. Progressive reduction of lymphocyte responses to pokeweed mitogen (PWM) in the presence of FBS and AP were less obvious, although it was still apparent that responses to PWM were depressed at 120 days of gestation and at parturition, when compared with lymphocyte responses during early pregnancy (at 40 days and 80 days of gestation). The difference was much more apparent with AP than with FBS and responses during early pregnancy were markedly higher than those with FBS. An increase in lymphocyte responsiveness to PWM 10 days post-parturition was evident whether FBS or AP was incorporated in the cultures. The response with FBS was again more marked than with AP.

Animals↗
PubMed1977

Human rotavirus in lambs: infection and passive protection.

A human stool filtrate containing rotavirus which was administered orally to gnotobiotic lambs caused diarrhea, virus excretion, development of antibodies to rotavirus, and pathological changes in the villi of the small intestine. Thus, lambs may serve as experimental animals for the study of human rotavirus infections. This model system was used to study passive protection. Human immunoglobulin G (IgG) containing antibody to rotavirus was fed to lambs 24 to 78 h after birth, and the lambs were infected with lamb-passaged human rotavirus when 30 h old. The lambs treated with IgG did not develop diarrhea, and virus excretion was delayed in onset and shortened in duration. It may be possible to make similar use of IgG to protect children at risk in a rotavirus outbreak. The treatment did not prevent the lambs developing antibody to rotavirus.

Administration, Oral↗
PubMed1977

The transfer of circulating 131I IgG1 and 125I IgG2 to the nasal secretions of sheep.

Ovine IgG1 and IgG2 labelled with 131I and 125I respectively were injected intravenously into four sheep. Serum and nasal secretion samples were collected and fractionated by gel filtration on columns of Sephadex G100. Results showed that in serum more than 95 per cent of the radioactivity was associated with intact IgG molecules whereas in nasal secretion samples the percentage varied from five to 47. It was found that the concentrations of IgG1 and IgG2 in the nasal secretions were similar and were approximately 2 per cent of the serum concentrations. This finding indicates a lack of selective transfer of either IgG1 or IgG2 from blood to nasal secretions in sheep.

Animals↗
PubMed1977

Reduced mitogenic responses in cultures of lymphocytes from newly calved cows.

The proliferative responses to stimulation with phytohaemagglutinin (PHA) in cultures of lymphocytes from newly calved and non-pregnant cattle were compared. Lymphocyte cultures from newly calved cows were seen to respond less to PHA than cultures from the non-pregnant cows. It is suggested that this depression in responsiveness of lymphocytes in the immediate post-parturient period may be involved in the etiology of disease in cattle during the immediate post-parturient period.

Animals↗