Because hepatocyte-stimulating factor/interleukin 6 (IL-6) the principal inducer of acute-phase protein synthesis in the liver, quantification of its activity in blood provides an early and sensitive assessment of the acute-phase response. Circulating IL-6 activity was monitored in 4 adult horses for 72 hours after IV administration of endotoxin. In 4 experiments performed at weekly intervals and in randomized order, each horse was given endotoxin-1,000, 30, 1, and 0 ng/kg of body weight. Plasma IL-6 activity was quantified as the ability to promote growth of the IL-6-dependent B-cell hybridoma, B13.29 clone B9. Interleukin-6 activity (171 +/- 10.2 U/ml) was found in all pretreatment plasma samples and was significantly (P < 0.05) increased above baseline from 2 to 12 hours after 1,000 ng of endotoxin/kg was given and at 3 hours after 30 ng of endotoxin/kg was given. After 1,000- or 30-ng/kg dosage of endotoxin, peak plasma IL-6 activity (10,128 +/- 4,096 and 1,555 +/- 1,326 U/ml, respectively) was observed for 3 hours. The IL-6 response of endotoxin-treated horses began about 1 hour after tumor necrosis factor appeared in the circulation, and its course closely approximated the endotoxin-induced febrile reaction. Significant increase in plasma IL-6 activity was not detected in horses given 1 ng of endotoxin/kg or control buffer.

Immunogenicity of the lipid A component of Haemophilus somnus lipooligosaccharide in cattle and mice was examined after purification, detoxification, and covalent conjugation to a protein carrier. After 2 inoculations, a substantial antibody response was induced in most cattle to lipid A and the protein carrier. To determine whether antibodies to lipid A would be protective, 5 X 10(7) colony-forming units of H somnus strain 649 were administered IV to endotoxin-responsive (C3H/HEN) mice. In one study, 8 of 13 C3H/HEN mice aborted when inoculated. In contrast, abortion did not result when mice were inoculated with the same dose of an isolate of H somnus normally found in the prepuce or with the rough mutant Escherichia coli J5. In addition, endotoxin-nonresponsive (C3H/HeJ) mice were significantly (P = 0.03) more resistant to abortion by strain 649 than were C3H/HeN mice, but inoculated C3H/HeN mice were only slightly more resistant to H somnus abortion, compared with control mice. Although a large antibody response to lipid A was detected, there was no significant difference in the immunized group between mice that aborted and mice that delivered normally. Thus, lipooligosaccharide and other properties of virulent H somnus strains may contribute to abortion in mice.

The sensitivity of an indirect enzyme-linked immunosorbent assay (ELISA) for bovine IgG serum antibody to Pasteurella haemolytica was compared with that of an indirect hemagglutination (IHA) test. Pasteurella haemolytica serotypes were grown in a chemically defined cell culture medium, and soluble antigens released into the growth medium were used in the ELISA and IHA test. An ELISA with serotype-1 antigen consistently detected antibody in sera that were positive by IHA test (correlation, 99%). Sera reacting with serotype-1 ELISA antigens also reacted with ELISA antigens prepared from other serotypes. Although ELISA titers determined by the 2 methods were approximately linear. Titer increases detected in paired serum samples by either test were similar. The ELISA was more sensitive than was the IHA in detecting colostral IgG antibody in serum of newborn calves. The ELISA uses a simple, stable antigen preparation and detects antibody to P haemolytica serotypes that commonly infect cattle.

Vaccina virus (VV) infection induces specific antibodies and cytotoxic T cells in various animal species. Therefore, helper T cells also should be induced that stimulate the humoral and cellular immune responses. We determined such helper T-cell activity in 2 species after VV infection. Rabbits and rhesus macaques were infected with the Copenhagen strain of VV or with recombinant VV expressing retroviral proteins. Animals of both species developed antibodies and specific proliferative T-cell response. This reactivity could be enhanced by booster infection with VV. The proliferating macaque cells were CD4+ and major histocompatability complex class II-restricted. These data confirm the broad immunogenicity of VV. Expression of additional polypeptides expressed from a recombinant VV does not lead to altered immune response to VV antigens. However, strength of the helper T-cell response, as well as clinical reactions, differed between macaques and rabbits. Infection with recombinant VV as delivery vectors offers the opportunity for combined vaccination against recombinant proteins and does not diminish cellular and humoral immune responses to VV itself.

Genetically altered stable nonreverting aromatic-dependent (aro-) Salmonella dublin, strain SL5631, was administered orally to healthy colostrum-fed calves as vaccine. Twenty-six calves were allotted to 4 groups. There were 2 experiments, each with a vaccinated and nonvaccinated control group. Skin testing with 0.1 ml of sonicated S. dublin was performed 3 days prior to challenge exposure. The IgG and IgM titers to S. dublin lipopolysaccharide (LPS) antigen were determined by ELISA on sera before initial vaccination and at 1.5 to 2 weeks after each vaccination. In experiment 1, six calves received a dose of 1.7 X 10(10) colony-forming units (CFU) of aro(-) S. dublin SL5631 orally at 2 and 4 weeks of age. After the first vaccination, 2 of 6 calves developed fever, but all 6 calves continued to have normal appetite and mental attitude. Adverse changes were not observed after the second vaccination. At the time of challenge exposure at 6 weeks of age, all 12 calves were seronegative for IgG and IgM LPS-specific antibodies, and the difference in percentage increase in skin test reaction at 48 hours was not significant. At 6 weeks of age, the 6 vaccinates and 6 controls were orally challenge-exposed with 1.5 X 10(11) CFU of virulent S. dublin T2340. Protection from challenge was not evident, as 3 of 6 controls and 5 of 6 vaccinates died after challenge exposure. In experiment 2, eight calves received a dose of 5 X 10(11) CFU of aro(-)S dublin SL5631 orally at 2, 3.5, and 5 weeks of age. The vaccine dose and volume (300 ml) were 30 times that of experiment 1. After each vaccination, some calves (7, 6, and 2 calves for first, second, and third doses, respectively) developed fever, but all calves continued to have normal appetite and attitude. At 7 weeks of age, the 8 vaccinates and 6 controls were orally challenge-exposed with 1.5 X 10(11) CFU of virulent S. dublin T2340 (same dose as experiment 1).

Systemic and pulmonary antibody responses of calves to Pasteurella haemolytica were evaluated by measuring immunoglobulin production in blood for 9 days and in pulmonary lavage fluid for 7 days after intrapulmonary inoculation. Clinical signs, pulmonary lesions, pulmonary and systemic inflammatory response, and amount of antigen in lavage fluid were used to evaluate the response of calves to challenge with P haemolytica. The pulmonary response consisted of production of IgG, IgE, and IgM antibodies to P haemolytica antigens and a 17- to 68-fold increase of cells in lavage fluid 8 hours after inoculation, with a gradual decrease toward normal. Antibodies of the IgM isotype to P haemolytica were demonstrated as early as 8 hours through 7 days after inoculation in 3 of 3 calves. Of the anti-P haemolytica isotypes, IgM was found in the highest concentration. In all of the inoculated calves, IgE was found 1 to 2 days after inoculation, and IgG was found in 2 of 3 inoculated calves from day 1 through 7 after inoculation. Detection of IgG correlated with smaller pulmonary lesions. Immunoglobulin A was not detected in lavage fluid. Serum was evaluated for IgG and IgM antibody response to P haemolytica. Specific IgM was detectable 5 days after inoculation, and IgG was detectable 7 days after inoculation. Pasteurella haemolytica antigens were not detected in serum or plasma. A transient increase in neutrophil count was found 8 hours after inoculation, with return to baseline values by 24 hours after inoculation. Antigen was detected in lavage fluid by use of monoclonal antibodies against selected P haemolytica capsular antigen, outer membrane antigens, and leukotoxin in all inoculated calves 8 hours after inoculation. The monoclonal antibody specific for P haemolytica capsule provided the best detection of antigen. The other monoclonal antibodies detected antigen, but were less consistent.

Cows naturally infected with Brucella abortus developed antibody (Ab) responses to a nonlipopolysaccharide antigen (NLA) purified from B abortus strain 1119-3. Sera from strain 19-vaccinated cows did not have detectable amounts of Ab. Weak lymphoproliferative responses to NLA were observed in blood mononuclear cell suspensions obtained from infected cows. There was no evidence of NLA-specific lymphoproliferation in cell suspensions from healthy cows. Nonlipopolysaccharide antigen binding to bovine blood mononuclear cells was observed by antigen-consumption assays and direct binding of radiolabeled antigen. Cells from infected cows bound less NLA than did cells from healthy cows when assays were conducted with intact blood mononuclear cell preparations (monocytes plus lymphocytes). Monocytes obtained from any group did not bind NLA. Purified B lymphocytes from infected and healthy vaccinated cows bound about 3 times more NLA than did T lymphocytes, but there were no apparent differences between the 2 groups in extent of binding. Results of the study indicate that bovine lymphocytes have binding sites for a NLA purified from B abortus strain 1119-3.