Immunogenicity of a Moraxella bovis bacterin containing attachment and cornea-degrading enzyme antigens.

An adjuvanted Moraxella bovis bacterin containing attachment antigens and cornea-degrading enzyme antigens protected cattle from infectious bovine keratoconjunctivitis (IBK) when experimentally challenged with homologous and heterologous challenge cultures of M. bovis. This bacterin also protected cattle against field exposure to M. bovis. Transmission electron microscopy and fluorescein labeled anti-M. bovis pili antiserum showed pili on the M. bovis bacterin strain. Scanning electron microscopy demonstrated a fibrillar glycocalyx. The bacterin strain of M. bovis, but not all strains of M. bovis, destroyed bovine corneal cell monolayers in vitro. Bovine corneal cells began to separate from each other within 5 min after M. bovis organisms were added and adhered to the cell monolayers. Moraxella bovis organisms remained attached to the disintegrating cells as the cell membrane separated and was digested. Vaccination stimulated bacterial agglutination antibodies. However, protection against experimental challenge was more closely related to the cornea-degrading enzyme content of the experimental bacterins. Twenty-two of 29 cattle (76%) vaccinated with bacterins containing a relative enzyme activity (REA) greater than 0.4 were protected in a rigorous challenge of immunity test. Only 1 of 21 non-vaccinated calves (5%) was free of IBK. Ninety-two percent (24/26) of calves vaccinated with a bacterin containing a REA greater than 0.29 remained free of IBK following field exposure, whereas 47% (8/17) non-vaccinated calves developed IBK. Only 8 of 12 calves (67%) vaccinated with a bacterin containing a REA of 0.09 remained free of IBK. In a larger field efficacy test consisting of 32 herds in six states, the incidence of IBK in individual herds ranged from 0% to 55%. The overall rate of infection was 11.2%. Vaccination of calves with an M. bovis bacterin that contained a REA of 0.63 reduced the incidence of IBK from 11.2% (217/1931) in the non-vaccinated controls to 4.3% (66/1520) in cattle vaccinated once and to 3.1% (48/1536) in cattle vaccinated twice.

Cell-mediated immune response to rabies virus in dogs following vaccination and challenge.

Peripheral blood lymphocytes (PBL) from non-vaccinated dogs and from dogs either vaccinated intramuscularly (IM) or subcutaneously (SC) with an inactivated rabies virus vaccine (Rabguard-TC, Norden Laboratories, Lincoln, NE) or intramuscularly with an attenuated rabies virus vaccine (Endurall-R, Norden Laboratories, Lincoln, NE) were exposed in vitro to rabies virus. Blastogenesis of PBL was measured by incorporation of 3H-thymidine into the DNA of proliferating cells in the presence of a suboptimal concentration of phytohemagglutinin (PHA). Following the first vaccination, there was no difference in the blastogenic response of lymphocytes from dogs vaccinated IM with either the inactivated or attenuated rabies virus vaccines. The inactivated rabies vaccine stimulated as great or greater blastogenic response when it was given SC. The PBL from non-vaccinated control dogs were not stimulated by rabies virus. Dogs vaccinated with the inactivated vaccine developed a lymphocyte blastogenic response to rabies virus following challenge with virulent street rabies virus. Nonvaccinated control dogs did not develop a lymphocyte blastogenic response to rabies virus following challenge with virulent street rabies virus.

Serologic evidence of coronavirus infection in New York and New England dairy cattle with winter dysentery.

Acute and convalescent sera were collected from 8 dairy herds with classic clinical features of winter dysentery. An enzyme-linked immunosorbent assay was used to measure coronavirus antibody titers, employing calf diarrhea coronavirus as antigen. Twenty-two of the 35 animals tested (63%) showed a greater than or equal to 4-fold seroconversion. Adult cattle in all 8 herds seroconverted. These findings complement previously reported immunoperoxidase and electron microscopic evidence, suggesting an etiologic role for an enteric coronavirus in this disease.

Characterization of a calf diarrheal coronavirus.

A coronavirus-like agent isolated from feces of a calf with diarrhea and attenuated by consecutive passage in a fetal bovine kidney cell line was characterized as a coronavirus. Negatively stained virions were approximately circular, had a mean diameter of 120 nm, and were covered with wide-spaced, petal-shaped projections about 20 nm long. Virions in ultrathin sections of infected cell monolayers had a mean diameter of 80 nm, lacked surface projections, and were found within cytoplasmic vesicles. Viral antigen was demonstrated by immunofluorescence microscopy to occur only in cytoplasm. Growth of the virus was not inhibited by 5-iodo-2'- deoxyuridine and actinomycin D. The virus was sensitive to ether, chloroform, deoxycholate, and heat treatment. However, thermosensitivity was stabilized in the presence of 1 M MgCl2; at pH 3, the virus was stable. Hemadsorption and hemagglutination were observed with erythrocytes of hamsters, mice, and rats but not with erythrocytes of cats, dogs, goats, sheep, cattle, horses, turkeys, chickens, guinea pigs, rabbits, geese, pigs, and man (type O). However, hemadsorption and hemagglutination were shown to be virus specific, since this could be inhibited by specific antiserum. Both infectivity and hemagglutinating activity were maximal at a particle density of 1.18 g/ml by sucrose density gradient centrifugation, indicating that hemagglutinin was part of the virion.

Chromic-acid formaldehyde fixation of nucleic acids of bacteriophage phi6 and infectious bovine rhinotracheitis virus.

Bacteriophage phi6 nucleic acid was present as a torus after chromic acid-formaldehyde-OSO4 fixation and acetone and propylene oxide dehydration. A herpes virus, infectious bovine rhinotracheitis virus, had its DNA mostly as a torus, collapsed in the centre, or as a network, after glutaraldehyde-OSO4 fixation, but in an uncollapsed torus or network formation after chromic acid-formaldehyde-OSO4. This fixative stabilized nucleic acids, allowing acetone dehydration and plastic embedding without collapse of nucleic acid to the centre of the virion.

Feline leukaemia vaccine protection against viral latency.

Seventeen cats, which were previously vaccinated with a subunit, feline leukaemia vaccine (Leukocell) and subsequently challenged with virulent feline leukaemia virus (FeLV), were tested at 2 to 4 years postchallenge for reactivation of latent FeLV infections. Administration of weekly doses of methylprednisolone induced significant decreases in lymphocyte numbers, but did not reactivate virus in bone marrow cultures from 15 cats in vivo or in vitro. These cats were observed to be neither persistently or latently viraemic prior to corticosteroid administration. The results of this study indicate that the vaccine is effective in affording significant protection against latent FeLV infections, even after severe immunosuppression. This finding, coupled with previously published results indicating protection against persistent viraemia and tumour formation, makes this vaccine highly effective in protecting against FeLV infections and associated disease.

Diarrhea in gnotobiotic calves caused by the reovirus-like agent of human infantile gastroenteritis.

Gnotobiotic newborn calves were found to be susceptible to infection with the reovirus-like agent of human infantile gastroenteritis (HRVL). Infection was based on (i) seroresponse using immunofluorescence and (ii) fecal shedding of virus particles using electron microscopy. Virus was detected in fecal samples for at least 2 to as long as 7 days after inoculation, although peak virus concentrations were observed on days 1 to 4. Diarrheal illness was observed in seven calves on second to fourth serial passage of HRVL in calves but in none of four animals studied on first passage. Diarrhea began 15 to 30.5 h (mean = 22.3 h) post-inoculation and lasted less than 24 h; three of the seven animals that developed diarrhea were also depressed or anorectic.

Protection against feline infectious peritonitis by intranasal inoculation of a temperature-sensitive FIPV vaccine.

Cats vaccinated intranasally (i.n.) with a temperature sensitive feline infectious peritonitis virus (ts-FIPV) vaccine were protected against an FIP-inducing challenge. Seventeen of 20 vaccinated cats (85%) survived a rigorous virulent FIPV challenge that caused FIP in 12 of 12 non-vaccinated cats (100%), 10 (83%) of which died. Intranasal vaccination stimulated serum IgG and serum and salivary IgA antibody responses (measured by ELISA), FIPV-neutralizing antibody (VN), and a cell-mediated immune (CMI) response as measured by lymphocyte proliferation. The serum antibody response to vaccination was not associated with protection. In fact, the IgG, IgA and VN titres were much higher in control cats than in vaccinated cats following challenge suggesting an immune-mediated pathogenesis. In contrast, stimulation of a mucosal IgA response to vaccination was related to protection. The in vitro proliferation of peripheral blood lymphocytes in response to virulent FIPV was observed in vaccinated cats, in vaccinated and challenged cats but not in non-vaccinated challenged cats.