Molecular epidemiology and pathogenesis of ruminant herpesviruses including bovine, buffalo and caprine herpesviruses 1 and bovine encephalitis herpesvirus

Restriction endonuclease DNA fingerprints of herpesviruses isolated from 3 unrelated epidemics of bovine encephalitis are similar to each other and totally different from bovine herpesvirus 1 (BHV1). Herpesviruses, antigenically related to BHV1, isolated from goats and buffalo have distinct DNA fingerprints. We propose that bovine encephalitis herpesvirus is prototypic of a new bovine herpesvirus type and that alpha herpes viruses from individual ruminant species are species specific.     

Biology of bovine herpesviruses

Cattle are the natural host of herpesviruses. Since now four different bovine viruses have been described as members of the family Herpesviridae. The prototype of the bovine herpesviruses, Bovine Herpesvirus type 1 (BHV-1), is the causative agent of infectious bovine rhinotracheitis (IBR), infectious pustular vulvovaginitis (IPV) and infectious balanoposthitis (IBP). The related BHV-5 is an exotic neurovirulent agent and like BHV-1 a member of the genus Varicellovirus, within the subfamily Alphaherpesvirinae. BHV-2, also an alphaherpesvirus but grouped into the genus Simplexvirus is the causative agent of bovine herpes mammilitis and pseudolumpy skin disease. In contrast, BHV-4, a member of the subfamily Gammaherpesvirinae, is not known to cause any disease. Beside bovine herpesviruses there are few other herpesviruses which can infect cattle. Infections of cattle with these herpesviruses have either clinical or diagnostic importance, based on a close antigenic relationship to BHV-1 of some ruminant herpesviruses. This article deals with the molecular virology of bovine herpesviruses and the pathogenesis of bovine herpesvirus infections and provides an overview over herpesviruses that can infect cattle.     

Serologic and virologic studies of selected cattle with antibodies to bovine herpesviruses

In order to investigate the specificity of low titer antibodies to BHV 1, twelve cattle were subjected to stress and dexamethasone treatment. They were monitored virologically by inoculating cell cultures with naso-pharyngeal-, ocular- and vaginal- or preputial swabs and serologically by assessing the prevalence and incidence of antibodies to bovine, caprine-, porcine-, and equine herpesviruses and to bovine leukemia virus. Antibodies were classified as specific for BHV 1 if the animals excreted IBR virus, or if the antibodies neutralized BHV 1 and reacted with BHV 1 antigens, or if they reacted additionally with CapHV antigens. Animals whose sera recognized BHV 1 and BHV 2 but not other herpesviruses, were judged to have experienced both infections. Nine of the twelve animals had specific BHV 1 antibodies. With three animals the question for specificity of their antibodies remains open. Two animals experienced several herpesvirus infections. Therefore, the induction of crossreacting antibodies, directed against epitopes common to herpesviruses, could not be ruled out. The sera of one animal reacted with BHV 1 and BHV 4 antigens in ELISA tests. They did, however, not neutralize BHV 1.     

Cross-reactions of bovine herpesvirus 1 antigens with those of other cattle herpesviruses

Bovine embryonic kidney cells were infected with bovine herpesviruses (BHV1, 2, or 3), suid herpesvirus 1 (SHV1), or were sham-inoculated. When cytopathic effect was apparent, the cells were solubilized using Triton X-100 detergent. Resulting antigen preparations were tested by 2-dimensional immunoelectrophoresis using bovine fetal serum and antisera directed against BHV1, BHV2, BHV3, SHV1 or a restricted spectrum of BHV1 antigens. Interaction of BHV1 antiserum with BHV1 antigen preparations resulted in 11 precipitation arcs. The same antiserum produced 3 arcs with BHV2, none with BHV3, and 5 with SHV1. The interaction of BHV1 antigen preparations with BHV2, BHV3, or SHV1 antisera failed to produce demonstrable arcs. However, when heterologous antigen or antibody preparations were added to BHV1 homologous 2-dimensional immunoelectrophoresis tests, all 11 BVH1 arcs were modified by BHV1, 2 by BHV2, 4 by BHV3 and 4 by SHV1 preparations. Two antigens were common to the 4 herpesviruses. Antigen preparations were tested for their ability to inhibit virus neutralization by BHV1 antiserum; only the BHV1 preparation was active. Sera were tested for BHV1 neutralizing activity; only BHV1 antiserum and a serum specific for a restricted spectrum of BHV1 antigens were active. A glycoprotein antigen associated with BHV1 neutralization was identified which may be important in the protection of animals against disease.     

Clinical, serologic, and cross-challenge response and virus isolation in cattle infected with three bovine dermatotropic herpesviruses.

The relationship of 3 dermatotropic bovine herpes-viruses (bovine mamillitis herpesvirus, dermatotropic bovine herpesvirus, and Allerton virus) was investigated; special emphasis was on the clinical response and the development of complement-fixation and precipitating antibodies in cattle. The immune respnse in steers was determined throughout the disease and after challenge exposure of the steers with 1 of the other 2 herpesviruses. Blood samples and sections of skin were collected intermittently from infected animals and examined for presence of virus.     

Identification and characterization of monoclonal antibodies reactive with bovine, caprine and ovine T-lymphocyte determinants by flow microfluorimetry.

Comparative flow microfluorimetric (FMF) analysis was used to identify and characterize 27 monoclonal antibodies (MoAbs) reactive with bovine T-lymphocytes. Determinants present on all circulating T-lymphocytes were recognized by 11 MoAbs, 8 of which blocked E rosette formation. Determinants present on only the BoCD4+ T-lymphocyte subset were detected by 9 MoAbs, while determinants restricted to the BoCD8+ T-lymphocyte subset were recognized by 7 MoAbs. Competitive labeling experiments demonstrated that determinants recognized by subset-specific MoAbs were present on BoCD4 or BoCD8 molecules. Comparative studies revealed that some determinants, both pan-T specific and subset-specific, were conserved on homologous (orthologous) molecules expressed on leukocytes from other species of ruminants. Polymorphism was evident with several determinants.     

Studies on bovine herpesviruses. Part 1. Isolation and characterization of viruses isolated from the genital tract of cattle

Herpesviruses, previously isolated from cattle (Theodoridis, 1978), were further studied and provisionally placed in the bovid herpesvirus 4 (BHV-4) group. Major differences were found between IBR-IPV (BHV-1) and BHV-4 virus strains. In MDBK cells, all BHV-4 strains started growing at the edges of the culture, the process progressing slowly until destruction of the cells was complete by the 10th day. BHV-4 strains failed to induce neutralizing antibodies in cattle, goats and rabbits. Only the addition of mineral oil adjuvant induced neutralizing and complement fixing antibodies in goats. BHV-1 strains, in contrast, produced very potent antisera in all these systems. Cross-neutralization tests indicated the existence of 2 distinct serological groups representing BHV-1 and BHV-4. The BHV-4 strains appear to be interrelated and they could not be grouped. A BHV-1 strain showed fixation of complement with the antisera of 6 BHV-4 strains. Electron micrographs showed an accumulation of nucleocapsids in the cytoplasm and an early release of virus particles due to cell destruction. Variation in incubation temperature had a significant effect on the particle formation. At lower temperatures, the number of enveloped particles in the cytoplasm increased. On the basis of the characteristics uncovered in this study, it is possible that all the BHV-4 strains represent one and the same virus which has undergone certain biological changes, thus illustrating a phenomenon which appears to be a characteristic of the herpesviruses.     

The glycoproteins of the human herpesviruses.

The herpesvirus family contains several important human pathogens. Human herpesviruses include herpes simplex virus type 1 and 2, varicella-zoster virus, human cytomegalovirus, Epstein-Barr virus and human T-cell lymphotropic virus. The general property of herpesviruses is their ability to establish latency and to be periodically reactivated. All human herpesviruses contain a subset of genes encoding viral glycoproteins that are clearly homologous, and their similarity is significantly greater among members of the same subfamily. Membrane glycoproteins specified by human herpesviruses are important determinants of viral pathogenicity. They are exposed on the viral envelope and on the surface of infected cells. They mediate entry of the virus into cells and cell-to-cell spread of infection and also influence tissue tropism and host range. Viral membrane glycoproteins are also the most important elicitors of protective immune response and are therefore the best candidates for subunit vaccines.     

Cross-reactive antibodies to BLV and HTLV in bovine and human hosts with retrovirus infection

Sera of 22 cattle naturally infected with bovine leukemia virus (BLV), of 2 calves vaccinated with BLV, and of 22 patients with human T cell leukemia virus type I (HTLV-I) infection were tested to BLV and HTLV-I by enzyme-linked immunosorbent assay (ELISA) and Western blotting (WB). Sera of 22 healthy cattle and from 22 healthy persons, and mouse monoclonal antibody to BLV-gp51, to HTLV-I-p24, or to HTLV-I-p19 were also tested. Sera of virus-infected hosts gave significantly higher ELISA values than sera of healthy donors to both BLV and HTLV-I. The correlation between ELISA values of bovine sera to BLV and those to HTLV-I was r = 0.76, whereas that of human sera was r = 0.35. By WB and competitive WB assays, bovine sera that were ELISA-positive to BLV reacted with one or more of p12, p15, and p24 of BLV, and with only p24 of HTLV-I. Human sera that were ELISA-positive to HTLV-I reacted with p12 and p24 of BLV, and with one or more of p12, p15, p19, and p24 of HTLV-I. These results demonstrate that BLV and HTLV-I are capable of evoking cross-reactive immune response in at least some hosts under natural infection as well as by virus vaccination.     

An epidemiological study of natural in utero infection with bovine leukemia virus.

The purpose of this study was to examine rates of natural in utero infection with bovine leukemia virus for association with breed, sex, dam age, dam parity and time of maternal seroconversion. Analyses conducted for breed and sex, dam age and parity and time of maternal seroconversion were the FUNCAT procedure for categorical data, Wilcoxon Rank Sums test and Fisher's exact test, respectively. A total of 223 calves born between July 1979, and September 1980, to cows infected with bovine leukemia virus in the University of Florida Dairy Research Unit herd were tested for detectable bovine leukemia virus antibodies prior to the consumption of colostrum. Sera were tested for antibodies by agar-gel immunodiffusion and radioimmunoprecipitation using the glycoprotein-51 antigen. In a group of 125 calves in which in utero infection could be confirmed through serological follow-up (group A), eight calves (6.4%) had precolostral bovine leukemia virus antibodies. For all 223 calves (group B), 18 (8.1%) had detectable bovine leukemia virus antibodies. For calves in group A, no associations were detected between precolostral bovine leukemia virus antibodies and breed (p = 0.66), dam age (p = 0.86), dam parity (p = 0.83), or time of maternal seroconversion to bovine leukemia virus (p = 0.50). However, precolostral bovine leukemia virus antibodies were found in 17.4% of the males and 3.6% of the females in group A (p = 0.11) and in 12.4% of the males and 3.6% of the females in group B (p = 0.04).     

Hematology of natural bovine trypanosomosis in the Brazilian Pantanal and Bolivian wetlands.

We report hematological changes observed in natural cases of bovine trypanosomosis due to Trypanosoma vivax in beef and dairy cattle from Bolivian wetlands and Pantanal, Brazil. The main hematologic changes produced by T. vivax infections were anemia and severe leucopenia. The cattle presented macrocytic hypochromic anemia. The leukocyte changes were characterized by relative lymphocytosis and monocytosis and decrease in the neutrophil counts. The clinical signs were lachrymation, progressive weakness, marked weight loss, inappetence, diarrhea and abortions during the third trimester of pregnancy.     

Interactions of bovine oocytes with follicular elements with respect to lipid metabolism

Among many factors, lipid metabolism within the follicular environment emerges as an important indicator of oocyte quality. In the literature a crucial significance is described concerning follicular fluid (FF) composition as well as messenger RNA (mRNA) expression in follicular cells. The aim of this study was to describe the relationship between oocyte, FF and follicular cells with regard to lipid metabolism. The set of data originating from individual follicles comprised: lipid droplets (LD) number in oocytes (BODIPY staining), mRNA expression of seven genes in cumulus and granulosa cells (SCD, FADS2, ELOVL2, ELOVL5, GLUT1, GLUT3, GLUT8; real time polymerase chain reaction) and fatty acid (FA) composition in FF (gas chromatography). Obtained results demonstrate significant correlation between oocyte lipid droplets number and FA composition in FF. However, gene expression studies show significant correlation between LD number and GLUT1 gene only. Moreover, the present experiment revealed correlations between FA content in FF and expression of several genes (SCD, FADS2, ELOVL5, GLUT8) in granulosa cells, whereas only the SCD gene in cumulus cells. We suggest that the results of our experiment indicate the importance of glucose : lipid metabolism balance, which contributes to better understanding of energy metabolism conversion between oocytes and the maternal environment.