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An enzyme-linked immunosorbent assay (ELISA) was developed for the quantitation of leptospiral antigen in bacterins containing Leptospira interrogans serovar pomona type kennewicki. A monoclonal antibody (MAb), 2D7, which is directed against a surface antigen on whole cells of L. interrogans serovar pomona type kennewicki, was used in the assay. The capture of antigen in bacterins by a polyclonal antiserum was followed by the addition of the 2D7 ascites fluid, an anti-mouse conjugate and substrate. Biologicals evaluated with this system included preparations containing type kennewicki antigen (homologous) and those not containing type kennewicki antigen (heterologous). Heterologous bacterins gave optical density (OD) values comparable to those of blank wells. Homologous bacterins yielded OD values equal to or greater than those of the National Veterinary Services Laboratories (NVSL) reference pomona bacterin. The relative potencies (RP) of 84 licensed commercial Leptospira pomona bacterin serials were evaluated against the NVSL reference pomona bacterin using the NVSL Relative Potency computer program. Random samples of 1, 2, 3 and 5 ml dose products were selected for evaluation with this system. All products tested passed the hamster potency assay required for leptospiral bacterins. This ELISA system enables detection of antigen in bacterins containing L. interrogans serovar pomona type kennewicki and demonstrates the potential for in vitro testing of leptospiral bacterins.

Resistance to clinical and renal leptospirosis in dogs injected with antiserum to Leptospira interrogans serotype canicola and Leptospira interrogans serotype icterohaemorrhagiae was demonstrated. The relationship between resistance induced in serum-injected hamsters was also demonstrated, using criteria of leptospiremia, renal infection, leptospiruria, and clinical signs of disease in dogs and death in hamsters.

Resistance to clinical and renal leptospirosis in dogs vaccinated with a bacterin containing Leptospira interrogans serotype canicola and Leptospira interrogans serotype icterohaemorrhagiae was demonstrated. The relationship between resistance induced in vaccinated dogs and that induced in vaccinated hamsters was also demonstrated, using criteria of leptospiremia, renal infection, leptospiruria, and clinical signs of disease in dogs and death in hamsters.

The immunogenic potency of bacterins containing Clostridium septicum was evaluated in mice, hamsters, guinea pigs, rabbits and sheep to establish potency requirements for these bacterins. Two subcutaneous injections of Cl. septicum bacterins were shown to provide resistance against intramuscular spore challenge. Protection in mice, hamsters and guinea pigs was generally at low levels, in the range of 1 to 5 LD50. Efficacy estimates, at these levels of challenge, indicated that a degree of relationship existed between the response of rabbits and the response of sheep. This relationship was confirmed at higher levels of spore challenge, at greater than 5 to 500 LD50. Undiluted bacterins were classed as good or poor based on percent survival responses in sheep. Bacterins providing 90 to 100% survival were classed as good; those providing 30 to 57% survival were classed as poor. In rabbits, this classification was less evident with the undiluted bacterins. Dilution of bacterins to 1:32 provided a discriminatory level with 7 of 8 bacterins examined and represented correlation of the sheep and rabbits responses. A similar relationship was demonstrated between protection in sheep against spore challenge and the antitoxin response in rabbits to undiluted bacterins. Antitoxin responses, when obtained, were generally higher in rabbits than those obtained in sheep. Further evaluation of a good and a poor bacterin in rabbits indicated that no direct relationship existed between antitoxin titer in rabbits and resistance to spore challenge, when compared at the same dilutions of bacterins. Evaluation of serum agglutination responses to types I and II somatic antigens indicated a poor relationship between agglutination response and resistance to spore challenge in both sheep and rabbits. Cl. septicum toxoids were shown to provide resistance to spore challenge in rabbits.

Leptospira interrogans serotype szwajizak was characterized by (1) its growth in polysorbate 80-bovine albumin medium, (2) its virulence and course of infection in laboratory animals, and (3) its immunogenicity. Growth of this organism was continuous and vigorous at 29 C and 37 C in liquid medium for 10 serial subcultures. Some specific lots of agar were superior to other agars if tested for the ability to support the growth of small inoculums. Individual colonies resulted from growth of small inoculums on solid polysorbate medium. Virulence of the organisms did not appear to be altered by 10 serial subcultures in liquid medium incubated at 29 C. The estimated median lethal dose of szwajizak for hamsters by the intraperitoneal route was 2 cells. Virulence, infectivity, and pathogenicity of szwajizak were shown in the hamster and the guinea pig. Protection results indicate the heat-inactivated szwajizak bacterin was a substantially better immunizing agent than the chemically inactivated bacterin. Serotype hardjo bacterins provided hamsters some protection against death if challenge exposed with szwajizak, but afforded no protection against infection.

Immunity to renal leptospirosis was demonstrated in cattle vaccinated with Leptospira interrogans serotype pomona. Vaccinated cattle, challenge inoculated with virulent L interrogans serotype pomona organisms 12 months after vaccination, were resistant to renal infection; similarly inoculated, but nonvaccinated, cattle were susceptible to renal infection. Relationship was demonstrated between immunity induced in vaccinated cattle and that induced in hamsters vaccinated with a dilution of the same bacterin and later inoculated with virulent L interrogans serotype pomona organisms.

Vaccination-challenge experiments were conducted in colostrum-deprived calves to evaluate the efficacy of Pasteurella bacterins and vaccines against experimental pneumonic pasteurellosis. Calves were vaccinated with formalin-killed bacterins and live vaccines, then challenge exposed intratracheally with P. haemolytica or P. multocida. Infectious bovine rhinotracheitis virus was inoculated intranasally three to four days prior to P. haemolytica challenge-exposure. All calves were examined for macroscopic and microscopic lesions after being found dead or following euthanasia four to seven days after challenge exposure with the bacterial pathogen. Clinical, hematological, and pathological responses to challenge exposure in aluminum hydroxide absorbed P. haemolytica and P. multocida bacterin-treated calves were consistent with the pneumonic lesions of pulmonary pasteurellosis in the control calves. An oil-adjuvanted P. haemolytica bacterin limited clinical and pathological responses in the affected calves whereas a P. multocida oil-adjuvanted bacterin did not. Both clinical and pathological responses to challenge exposure in calves vaccinated with live Pasteurella vaccines were less severe than those of the control calves. Vaccine effectiveness appeared to be dose dependent.

Three groups of ewes were vaccinated with formalin inactivated, whole cell, aluminum hydroxide adjuvanted bacterins prepared from capsulated enteropathogenic Escherichia coli (EEC). Lambs born to and suckling these ewes, compared with lambs of nonvaccinated control ewes, were highly resistant to homologous EEC challenge exposure. Lambs of ewes vaccinated with products prepared from K99 antigen-positive, noncapsulated E coli were highly resistant to heterologous EEC challenge exposure. In both cases, lambs of vaccinated ewes had significantly (P less than 0.005) less morbidity and mortality, fewer challenge inoculum-type E coli per rectal swab evaluation, and had superior weight gains over a 4-day period. Immunoglobulin assay of 122 lamb sera (collected 12 hours after birth) failed to reveal any correlation between serum immunoglobulin values and morbidity or mortality. When tested by plate agglutination technique, using whole cell antigens, or by reverse radial immunodiffusion, using purified capsular antigens, colostral whey samples of vaccinated ewes did not have increased capsular antibody titers. The K99 serum antibody values of K99 antigen-vaccinated ewes were markedly higher than were those of ewes vaccinated with other bacterins or of control ewes.