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.

Addition of alanine and taurine blocked killing of lymphocytes caused by culture at 45 C. The optimal concentration for thermoprotection was achieved at 12.5 mM for L-alanine and 5 mM for taurine. Both D and L forms of alanine provided thermoprotection. The effect of these agents was not simply to increase osmolarity of the culture medium, because NaCl did not provide thermoprotection at comparable concentrations. Alanine and taurine were each tested at concentration of 50 mM for ability to block heat shock-induced killing and developmental retardation of 8- to 16-cell mouse embryos. Both agents enhanced embryo development after exposure to high temperature, though development remained less than that for embryos not exposed to high temperature. In one experiment, for example, 81% of embryos cultured at 38 C advanced in development during culture vs 0% at 42 C, 15% at 42 C with alanine, and 32% at 42 C with taurine. The beneficial effect of alanine at high temperature may have been partly attributable to effects independent of thermoprotection, because development of embryos cultured at 38 C was also improved by alanine.