CD4(+) cytotoxic T-lymphocyte activity against macrophages pulsed with bovine herpesvirus 1 polypeptides

The Cell-Mediated Immune Response against Bovine alphaherpesvirus 1 (BoHV-1) Infection and Vaccination

Bovine Alphaherpesvirus 1 (BoHV-1) is one of the major respiratory pathogens in cattle worldwide. Infection often leads to a compromised host immune response that contributes to the development of the polymicrobial disease known as “bovine respiratory disease”. After an initial transient phase of immunosuppression, cattle recover from the disease. This is due to the development of both innate and adaptive immune responses. With respect to adaptive immunity, both humoral and cell-mediated immunity are required to control infection. Thus, several BoHV-1 vaccines are designed to trigger both branches of the adaptive immune system. In this review, we summarize the current knowledge on cell-mediated immune responses directed against BoHV-1 infection and vaccination.

Immunity to bovine herpesvirus 1: II. Adaptive immunity and vaccinology

Bovine herpesvirus 1 (BHV-1) infection is widespread and causes a variety of diseases. Although similar in many respects to the human immune response to human herpesvirus 1, the differences in the bovine virus proteins, immune system components and strategies, physiology, and lifestyle mean the bovine immune response to BHV-1 is unique. The innate immune system initially responds to infection, and primes a balanced adaptive immune response. Cell-mediated immunity, including cytotoxic T lymphocyte killing of infected cells, is critical to recovery from infection. Humoral immunity, including neutralizing antibody and antibody-dependent cell-mediated cytotoxicity, is important to prevention or control of (re-)infection. BHV-1 immune evasion strategies include suppression of major histocompatibility complex presentation of viral antigen, helper T-cell killing, and latency. Immune suppression caused by the virus potentiates secondary infections and contributes to the costly bovine respiratory disease complex. Vaccination against BHV-1 is widely practiced. The many vaccines reported include replicating and non-replicating, conventional and genetically engineered, as well as marker and non-marker preparations. Current development focuses on delivery of major BHV-1 glycoproteins to elicit a balanced, protective immune response, while excluding serologic markers and virulence or other undesirable factors. In North America, vaccines are used to prevent or reduce clinical signs, whereas in some European Union countries marker vaccines have been employed in the eradication of BHV-1 disease.

Comparison of gene expression by co-cultured WC1+ gammadelta and CD4+ alphabeta T cells exhibiting a recall response to bacterial antigen

Immunization of cattle with a Leptospira borgpetersenii serovar hardjo-bovis vaccine results in the development of a recall response by WC1(+) gammadelta T cells and CD4(+) alphabeta T cells characterized by proliferation and interferon-gamma production. It was hypothesized that these two T cell subpopulations had largely redundant effector functions, principally differing in their requirements for activation. To test this, gene expression in cells proliferating to antigen were compared utilizing RT-PCR and bovine microarrays. Both T cell populations had similar transcript profiles for effector molecules, including IFN-gamma, FasL and granzyme B. In contrast, transcripts for costimulatory receptors and ligands were notably different following activation, as WC1(+) T cells expressed no or lower levels of transcripts for CD28 and CD40L, while CD4(+) T cells expressed substantial levels of both. However, both cell types had high levels of CTLA-4 transcript suggesting the cells may be regulated similarly following activation but differ in their need for and ability to provide costimulation. Microarray analyses to extend the number of genes examined revealed that while both subpopulations upregulated anti-apoptotic genes as well as those involved in cell activation and protein biosynthesis, overall there were limited differences between the two antigen-activated cell populations. Those genes that did differ were involved in cell signaling, protein production and intracellular protein trafficking. These results strengthen the hypothesis that these particular activated WC1(+) and CD4(+) T cells have overlapping effector functions and therefore may differ principally with regard to how they are recruited into immune responses.

BHV-1-Specific CD4+, CD8+, and gammadelta T cells in calves vaccinated with one dose of a modified live BHV-1 vaccine

Expression of the high-affinity interleukin 2 receptor alpha chain (CD25) was used to monitor antigen-specific activation of T lymphocyte subsets (CD4+, CD8+, and gammadelta T cells) from cattle immunized with modified live bovine herpesvirus-1 (BHV-1). Calves seronegative for BHV-1 were either vaccinated with one dose of modified live vaccine containing BHV-1 or not vaccinated to serve as negative controls. Two animals vaccinated 7 and 5 weeks before the start of the experiment with two doses of modified live vaccine containing BHV-1 served as positive controls. Blood samples were taken from the nonvaccinate group, the positive control group, and the vaccinate group at 0, 21, 35, 60, and 90 days postinoculation (PI). Isolated peripheral blood mononuclear cells from immunized and control animals were incubated for 5 days with and without live BHV-1 ISU99. Compared to the nonvaccinates, a significant (p < 0.05) increase in expression of CD25 by CD4+, CD8+, and gammadelta T lymphocytes from the vaccinate group was detected following in vitro exposure to live BHV-1 after vaccination. This is apparently the first report using live BHV-1 to stimulate lymphocytes in vitro and showing CD8+ T cell activation. Peripheral blood from the positive control animals was depleted of CD4+, CD8+, or gammadelta T lymphocytes prior to incubation with BHV-1 to assess bystander activation in the CD25 expression assay. When incubated with live BHV-1, depletion of CD4+ T cells depressed the expression of CD25 by CD8+ T cells, but not gammadelta T cells. Depleting CD8+ or gammadelta T cells prior to in vitro culture with BHV-1 did not affect the expression of CD25 by the remaining T lymphocyte subsets. Vaccinates were protected from challenge with virulent BHV-1 at 110 days postvaccination compared to nonvaccinates. Expression of CD25 appears to be a useful marker for evaluating induction of antigen-specific T lymphocyte subset responses following vaccination.

T-cell receptor-mediated anergy of a human immunodeficiency virus (HIV) gp120-specific CD4(+) cytotoxic T-cell clone, induced by a natural HIV type 1 variant peptide

Human immunodeficiency virus type 1 (HIV-1) infection triggers a cytotoxic T-lymphocyte (CTL) response mediated by CD8(+) and perhaps CD4(+) CTLs. The mechanisms by which HIV-1 escapes from this CTL response are only beginning to be understood. However, it is already clear that the extreme genetic variability of the virus is a major contributing factor. Because of the well-known ability of altered peptide ligands (APL) to induce a T-cell receptor (TCR)-mediated anergic state in CD4(+) helper T cells, we investigated the effects of HIV-1 sequence variations on the proliferation and cytotoxic activation of a human CD4(+) CTL clone (Een217) specific for an epitope composed of amino acids 410 to 429 of HIV-1 gp120. We report that a natural variant of this epitope induced a functional anergic state rendering the T cells unable to respond to their antigenic ligand and preventing the proliferation and cytotoxic activation normally induced by the original antigenic peptide. Furthermore, the stimulation of Een217 cells with this APL generated altered TCR-proximal signaling events that have been associated with the induction of T-cell anergy in CD4(+) T cells. Importantly, the APL-induced anergic state of the Een217 T cells could be prevented by the addition of interleukin 2, which restored their ability to respond to their nominal antigen. Our data therefore suggest that HIV-1 variants can induce a state of anergy in HIV-specific CD4(+) CTLs. Such a mechanism may allow a viral variant to not only escape the CTL response but also facilitate the persistence of other viral strains that may otherwise be recognized and eliminated by HIV-specific CTLs.

Susceptibility of bovine antigen-presenting cells to infection by bovine herpesvirus 1 and in vitro presentation to T cells: two independent events

The aim of the present study was to develop an in vitro system for presentation of bovine herpesvirus 1 (BHV-1) antigens to bovine T lymphocytes and to characterize the antigen-presenting cells (APC) which efficiently activate CD4(+) T cells. Two approaches were used to monitor the infection of APC by BHV-1 as follows: (i) detection of viral glycoproteins at the cell surface by immunofluorescence staining and (ii) detection of UL26 transcripts by reverse transcription-PCR. The monocytes were infected, while dendritic cells (DC) did not demonstrate any detectable viral expression. These data suggest that monocytes are one site of replication, while DC are not. The capacities of monocytes and DC to present BHV-1 viral antigens in vitro were compared. T lymphocytes (CD2(+) or CD4(+)) from BHV-1 immune cattle were stimulated in the presence of APC previously incubated with live or inactivated wild-type BHV-1. DC stimulated strong proliferation of Ag-specific T cells, while monocytes were poor stimulators of T-cell proliferation. When viral attachment to the surface of the APC was inhibited by virus pretreatment with soluble heparin, T-cell proliferation was dramatically decreased. Unexpectedly, incubation of DC and monocytes with the deletion mutant BHV-1 gD-/-, which displays impaired fusion capacity, resulted in strong activation of T lymphocytes by both APC types. Collectively, these results indicate that presentation of BHV-1 antigens to immune T cells is effective in the absence of productive infection and suggest that BHV-1 gD-/- mutant virus could be used to induce virus-specific immune responses in cattle.

BHV-1: new molecular approaches to control a common and widespread infection

BACKGROUND

Herpesviruses are widespread viruses, causing severe infections in both humans and animals. Eradication of herpesviruses is extremely difficult because of their ability to establish latent and life-long infections. However, latency is only one tool that has evolved in herpesviruses to successfully infect their hosts; such viruses display a wide (and still incompletely known) panoply of genes and proteins that are able to counteract immune responses of their hosts. Envelope glycoproteins and cytokine inhibitors are two examples of such weapons. All of these factors make it difficult to develop diagnostics and vaccines, unless they are based on molecular techniques.

MATERIALS AND METHODS

Animal herpesviruses, because of their striking similarity to human ones, are suitable models to study the molecular biology of herpesviruses and develop strategies aimed at designing neurotropic live vectors for gene therapy as well as engineered attenuated vaccines.

RESULTS

BHV-1 is a neurotropic herpesvirus causing infectious rhinotracheitis (IBR) in cattle. It is a major plague in zootechnics and commercial trade, because of its ability to spread through asymptomatic carrier animals, frozen semen, and embryos. Such portals of infections are also important for human herpesviruses, which mainly cause systemic, eye, and genital tract infections, leading even to the development of cancer.

CONCLUSIONS

This review covers both the genetics and molecular biology of BHV-1 and its related herpesviruses. Epidemiology and diagnostic approaches to herpesvirus infections are presented. The role of herpesviruses in gene therapy and a broad introduction to classic and engineered vaccines against herpesviruses are also provided. http://link.springer-ny. com/link/service/journals/00020/bibs/5n5p261.html