Biomedical subjects
Publications and source records attributed to L A Babiuk.
Hep-2 cells infected with measles virus (MV) for as short as 6 h became refractory to superinfection with canine distemper virus (CDV) but not to vesicular stomatitis virus (VSV). The exact mechanism of such interference is unknown but probably occurs after virus attachment and penetration. These results verify the suggestion that virus interference may be a mechanism of heterotypic protection against canine distemper.
Sudden death of pups in the 4- to 6-week age range has recently been occurring in western Canada as a result of severe, primary, nonsuppurative myocarditis. At necropsy, the prominent macroscopic lesion was pulmonary edema, and microscopically, characteristic intranuclear inclusion bodies were found within cardiac myofibers in association with myocarditis. Ultrastructurally, numerous small particles resembling parvoviruses were found within the intranuclear inclusion bodies, which were positive by direct fluorescent antibody test for canine parvovirus. Of three pups inoculated with homogenate from affected myocardium, one developed lesions resembling canine parvoviral enteritis.
A crude extract from Ascaris suum was infused into the teat canal of heifers to serve as an irritant or an antigens. The cells present in the mammary gland following such stimulation were assessed over a period of 2 weeks. Prior to stimulation there were few cells, predominantly macrophages, however, by 12 h post-stimulation a larger number of eosinophils and neutrophils were present. The eosinophils, which represented approximately 50% of the total population, could be purified by Ficoll-Hypaque flotation and nylon or glass wool column filtration to yield a population consisting of over 90% eosinophils. Surface marker studies on the purified eosinophils revealed that they contained both Fc and complement receptors.
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Pregnant cattle were either vaccinated subcutaneously with (i) a suspension of purified Escherichia coli K99 pili, (ii) a Formalin-killed whole cell bacterin containing enterotoxigenic E. coli strain B44 (O9:K30;K99:H-), or (iii) a bacterin containing six different strains of bovine enterotoxigenic E. coli (multiple-strain bacterin), or were left as nonvaccinated controls. After birth, calves were allowed to nurse their dams and, at 12 to 14 h of age, were challenged orally with 10(11) cells of enterotoxigenic E. coli strain B44. Colostral antibody titers were determined against K99, K30, and O9 antigens of B44. In the nonvaccinated control group, 9 of 10 calves developed diarrhea and died within 24 to 72 h. Similarly, all six calves in the multiple-strain bacterin group developed diarrhea and four died. In contrast to calves in the two groups mentioned above, calves nursing cows vaccinated with either purified K99 or the homologous whole cell bacterin were protected against fatal diarrhea. There was a highly significant correlation (P less than 0.0005) between protection against fatal diarrhea and K99, but not K30 or O9 colostral antibody titers. Vaccination of cows with either purified pili or whole cell preparations containing sufficient K99 antigen may provide a means of preventing enterotoxigenic colibacillosis in calves.
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A Vero cell adapted Green strain of canine distemper virus (CDV) was tested for its plaque-forming capacity in different cell lines. Plaque formation was observed in HEp-2, BS-C-1, and HeLa cells but not in Vero or dog kidney cells even though replication and cytopathology were observed in the latter cell types. In the cells in which the virus was capable of producing plaques, the plaques were observed within 24 h post infection and continued to increase in size with subsequent cellular destruction such that by 72 h postinfection the size of the plaques approached 0.5 mm. With the use of the plaquing technique, it was possible to demonstrate the thermal lability of the virus as well as the kinetics of adsorption. Thus, it was shown that the half-life of the virus was 125 min at 25 degrees C, 75 min at 35 degrees C, and 65 min at 37 degrees C. The rate of adsorption of CDV to HEp-2 cells was 17.2% in 30 min at 37 degrees C and continued slowly for 4 h before completion. Application of this rapid plaque-forming assay to plaque-reduction tests for CDV antibody and for CDV-infected cells by the infectious center assay are described.
Various cultural conditions were assessed for their ability to maintain canine peripheral blood monocytes in vitro. Approximately ten days after incubation of peripheral blood leukocytes in Earle's minimum essential medium supplemented with homologous red cell lysates and normal horse serum, virtually a pure macrophage culture was obtained which could then be maintained for about two months. This culture was judged to be pure by surface marker analysis and their phagocytic activity. The number of monocytes could be increased by injecting the dogs with a chloroform extract from Listeria monocytogenes prior to collection of the blood.
Specific antibody was shown to be highly effective in neutralizing extracellular canine distemper virus (CDV) as well as preventing the intercellular spread of this virus. Thus, relatively low levels of antibody neutralized 1 x 10(5) TCID50 of extracellular CDV and the development of plaques or CPE in Hep-2 and Vero cells respectively could be prevented even when up to 5% of the cells were infected. This inhibition of CPE and virus spread was most pronounced when antibody was added early but could still limit the degree of CPE if added as late as 48 h post-infection. This anti-viral activity was observed in different cell types including canine macrophages, cells normally infected with CDV in vivo. Prolonged exposure of infected target cells to high concentrations of antibody led to redistribution of surface viral antigens and their subsequent disappearance. The possible role of antibody in the defence against, and/or recovery from CDV and the mechanism(s) by which antibody may aid in recovery are discussed.
The serological results from this study clearly show that both equine influenza and equine rhinopneumonitis viruses were present during spring and autumn epidemics of respiratory disease on Western Canadian racetracks. Approximately 11% of the horses showed significant convalescent titres to influenza while 9% showed significant convalescent titres for equine viral pneumonitis. It was noted in our study a positive vaccination history corresponded with a reduction in the severity of the respiratory infection.
Canine peripheral blood lymphocytes, polymorphonuclear leucocytes (PMN) and monocytes (macrophages) were obtained by various cell separation techniques and were tested for their cytotoxic capacity against antibody-sensitized canine distemper virus (CDV) infected Vero cells by an in vitro chromium release assay. Canine lymphocytes were found to destroy CDV infected target cells effectively, while neither PMN nor monocytes (macrophages) could do so. The active lymphocyte was characterized by various rosetting techniques to be a non-T and a non-B lymphocyte. These cells bear no surface immunoglobulin (SIg-) but possessed both Fc receptors (Fc+) and complement receptors (EAC+) suggesting that these cells are neither classical T nor B cells. The possible roles of this K cell in the resistance against canine distemper are discussed.
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T. theileri has been isolated from primary cultures of bovine retina and subcultered successfully for 2 passages in sub-confluent cultures. When cultures reached confluency no trypomastigotes or epimastigotes could be detected and attempts to recover trypanosomes from these cultures were unsuccessful. The presence of intracellular forms could not formally be excluded.
The paper presents evidence that polymorphonuclear neutrophils upon stimulation with herpesvirus-induced antigens release a material inhibitory to virus infection. The material does not appear to be identical to type I or II interferon.
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Experiments were undertaken to establish whether the cytotoxic activity of canine immune effector cells against viral antigens was affected by the genotype of the target cell (genetic restriction). Puppies from three different breeds were infected with vaccinia virus, and the peripheral blood leukocytes were collected at various times for measurement of their cytotoxicity against autologous and heterologous vaccinia virus-infected and uninfected skin fibroblasts. In all cases cytotoxicity only occurred against virus-infected targets, and there was no consistent evidence of preferential killing of autologous targets. Several indirect approaches were used to demonstrate that direct, presumably T cell, cytotoxicity was being measured rather than antibody-dependent cell cytotoxicity. On the basis of the evidence from cross mixed-lymphocyte assays and cell-mediated lympholysis assays, the dogs were shown not be be identical with respect to their histocompatibility antigens. The significance of our findings to the phenomenon of genetic restriction as observed for mouse-derived immune effector cells is briefly discussed.
Human peripheral blood polymorphonuclear neutrophils (PMN) were tested for their ability to act as effector cells in antibody-dependent cell cytotoxicity (ADCC) against Herpes simplex virus (HSV) infected target cells sensitized with anti-HSV serum. The PMN from all 29 individuals tested could mediate ADCC in the presence of a standard human anit-HSV serum. Since PMN are prominent cells early in herpes lesions, it was hypothesized that because ADCC could represent an in vitro model for antiviral recovery, perhaps the efficacy of PMN at mediating ADCC might be impaired in those subjects to frequent recrudescent herpes. However, evidence for the hypothesis was not obtained since the PMN from individuals with frequent, infrequent, or unrecorded herpes labialis all showed approximately the same activity at mediating ADCC. Alternative ways in which PMN could be involved in antiviral recovery were discussed.