Humoral immunity in the ewe. 1. The influence of adjuvancy and immunogenic substitution on immune reactivity following immunisation with protein antigens

A long-term study on the health status and performance of sows on different feed allowances during late pregnancy. III. Escherichia coli and other bacteria, total cell content, polymorphonuclear leucocytes and pH in colostrum and milk during the first 3 weeks of lactation

The objectives of this study were to (1) estimate the clinical status of the mammary glands and (2) compare it with the bacteriological findings, the total cell content (TCC) and its percentage of polymorphonuclear leucocytes (PMNLs) and pH in colostrum and milk secretion of sows on 2 different feeding regimes, high versus low, during late pregnancy. The milk samples were collected from both agalactia post partum (APP) sows and clinically healthy sows. Sows with a rectal temperature exceeding 39.5 degrees C within 48 h after parturition were considered to be diseased in APP and treated medically. The sows were sampled on days 1, 3, 8 and 22 of lactation during 6 consecutive lactations. Irrespective of feeding regimes, 49 out of 77 lactations among the APP sows and 15 out of 96 lactations among the clinically healthy sows revealed E. coli in pure cultures with a concomitant TCC exceeding 10 x 10(6) cell/ml already on the first day of lactation. The healthy sows with E. coli infection were denominated as being subclinically infected sows. The intensity in growth of E. coli successively declined, and the bacteria were finally eliminated between days 3 and 8 of lactation. The TCC were 82 x 10(6) cells/ml and 157 x 10(6) cells/ml in the clinically and subclinically E. coli infected glands, respectively, on the first day of sampling. The TCC declined gradually in both groups of sows, but was still higher than in bacteriologically negative milk on day 22 of lactation. The percentages of PMNLs were 66% and 79% in clinically and subclinically infected glands, respectively, on day 1 of lactation, thereafter decreasing to approximately 50% on day 22 of lactation in both groups of sows. In APP sows, swelling, reddening and/or soreness were registered in 38 out of 87 mammary glands with E. coli mastitis on the first sampling occasion. The TCC in bacteriologically negative colostrum and milk collected from APP sows on day 1 of lactation was significantly higher, 2.27 x 10(6) cells/ml, when compared with the TCC in bacteriologically negative milk secretion from the clinically healthy or subclinically infected sows, 1.38 x 10(6) cells/ml versus 1.51 x 10(6) cells/ml, respectively. The PMNLs were higher on day 1 in clinically healthy sows, 59.6%, than in subclinically infected and APP sows (43.5% and 48.3% respectively). The pH in secretion from clinically or subclinically E. coli infected glands (6.57 versus 6.46) were higher than in bacteriologically negative colostrum samples (6.29) from clinically diseased sows on the first day of sampling. On day 22 of lactation, pH-values had stabilized on a level of approximately 7.00 in all milk samples from earlier bacteriologically positive or negative mammary glands. The 2 feeding regimes, low versus high, were not found to influence TCC, PMNLs or pH except for TCC in bacteriologically negative samples of APP sows (2.69 versus 3.62). The lactation number influenced the PMNLs in both groups of sows with E. coli infected mammary glands, and both the TCC and PMNLs in bacteriologically negative colostrum and milk.

The response of cattle vaccinated with hypodermin A to a natural infestation of Hypoderma bovis and Hypoderma lineatum

In this study, we have determined whether immunization with hypodermin A (HA), associated with various adjuvants, could provide protective immunity for calves when challenged with a natural hypoderma infestation. Groups of naive calves were vaccinated with HA antigen alone or with adjuvants [Freund's incomplete adjuvant (FIA) or alumina phosphate (AP)]. Subcutaneous injection with HA antigen with or without adjuvant did not significantly protect calves against a natural hypodermosis infestation. The humoral response during the infestation period was evaluated by ELISA. A significant earlier and greater response was induced in groups vaccinated with HA alone and HA combined with FIA. These results indicate that HA, in this vaccination protocol, induces a very incomplete protection in calves exposed to a natural infestation.

Humoral immunity in the ewe. 2. The effect of pregnancy on the primary and secondary antibody response to protein antigen

This study examines the effect of pregnancy on the quantity and isotype of antibody in ewes immunised with a novel primary antigen. The primary and secondary antibody levels to bovine serum albumin (BSA) in alum adjuvant, were compared between non-pregnant ewes and ewes immunised at different stages of pregnancy. Anti-BSA isotype specific responses were measured using an indirect ELISA. Results show the levels of immunoglobulin M (IgM) increased and persisted in response to BSA during pregnancy (P less than 0.05). Secondary immunoglobulin G1 (IgG1) titres were significantly impaired in late pregnancy and during lactation (P less than 0.05). The lower levels of immunoglobulin G2 (IgG2) were unaffected by pregnancy under these experimental conditions. Ewes were also immunised with BSA in alum adjuvant for their primary inoculum and BSA in different adjuvants for the secondary inoculation. Primary IgM persisted at higher levels during pregnancy compared with the response in non-pregnant ewes (P less than 0.05). Following the secondary injection, lower levels of anti-BSA specific IgM, IgG1 and IgG2 antibodies were produced in late pregnancy and during lactation compared with the levels in non-pregnant control ewes (P less than 0.05). Alterations in regulatory T-cell function or effector B-cell activity would most readily explain the qualitative changes in antibody titre observed following primary injection during pregnancy. The results also suggest an associated impairment of immunological memory following primary immunisation during pregnancy.

Humoral immunity in the ewe. 3. The influence of adjuvants and immunisation regimes on immune reactivity in the breeding ewe and her progeny

Breeding ewes were immunised with clostridial vaccine using different inoculation schedules. Results, showing differences in the class of antibody produced, were heavily dependent on the vaccination regime used. Immunoglobulin M (IgM) levels were significantly lower in ewes given double doses of vaccine compared to ewes given a single inoculation or no treatment at all (P less than 0.01). Neonatal lambs showed significant de novo IgM production with interference in this antibody production in the lambs of ewes vaccinated with the clostridial vaccine (P less than 0.05). Immunoglobulin G1 (IgG1) levels were significantly increased in all lambs which had mothers vaccinated with the clostridial vaccine prior to or during pregnancy (P less than 0.025). The greatest quantity of IgG1 was transferred to lambs when their mothers were given a double injection with primary inoculation prior to conception and booster prepartum (P less than 0.025). No antigen specific immunoglobulin G2 (IgG2) was detected in the lambs. Ewes were also immunised with BSA and their isotype specific serum antibody response was compared with their respective lambs. There was no detectable anti-BSA IgM in the lambs of all groups of ewes though specific IgG1 antibodies could be readily detected in the lambs of hyperimmunised ewes. The efficiency of transfer was related directly to the ability of the adjuvant to maximise IgG1 production in the ewe. Although immunised ewes produced high levels of IgG2, this was not transferred passively to the lamb.