concanavalin-a and Birnaviridae-Infections

Infectious bursal disease (IBD) continues to pose potential threat to poultry industry all over the world. The disease can spell disaster not only through its infection but also by break of immunity in chickens vaccinated for other diseases. l-Arginine, a ubiquitous, semi-essential amino acid has emerged as an imunostimulant from variety of human and animal studies. In the present study, we demonstrate the stimulatory effects of l-arginine on intestinal intraepithelial lymphocyte (iIELs) functions as well as on systemic immune response in chickens orally vaccinated with live intermediate plus (IP) strain of IBD vaccine. Challenge studies with virulent IBDV revealed complete (100%) protection in IP+l-arginine group compared with 80% protection recorded in IP strain vaccinated chickens. Functional activities of iIELs evaluated by cytotoxicity assay demonstrated significantly high percentage cytotoxicity in IP+l-arginine groups compared with IP group (P<0.05). Proliferative response of iIELs against IBDV antigen and Con-A was also significantly higher in IP+l-arginine group. Similar results were obtained with peripheral blood mononuclear cell blastogenic response to IBDV and Con-A analyzed as an indicator of systemic cell-mediated immune response. Orally administered IP strain vaccine elicited good antibody titres in both the groups, IP and IP+l-arginine, however, the antibody titres were significantly higher in IP+l-arginine group compared with IP vaccinated group (P<0.05). These results clearly demonstrate that l-arginine stimulates intestinal and systemic immune response against IBDV.

Topics: Administration, Oral; Animals; Antibodies, Viral; Antigens, Viral; Arginine; Birnaviridae Infections; Cell Proliferation; Chickens; Concanavalin A; Infectious bursal disease virus; Intestinal Mucosa; Leukocytes, Mononuclear; Lymphocytes; Time Factors; Viral Vaccines

The role of cell-mediated immunity (CMI) in pathogenesis of infectious bursal disease virus (IBDV) was investigated. One-day-old specific pathogen-free chickens were treated with 3mg of cyclophosphamide (Cy) per chicken for 4 consecutive days and, 3 weeks later, infected with the IBDV-IM strain. Chickens were examined for: (a) mitogenic response of splenocytes to ConA, as an indicator of T-cell functions in vitro, (b) antibody against IBDV by ELISA, (c) IBDV genome in various tissues by RT-PCR and (d) immunological memory. At the time of IBDV infection, Cy-treated chickens had depleted bursal tissue (an avian primary B-cell lymphoid organ), severely compromised antibody-producing ability, but normal T-cell response to ConA. In primary infection, no detectable antibody against IBDV antigen in Cy-treated, IBDV-infected chickens was observed up to 28 days post-infection (PI), while IBDV genome was detected by RT-PCR in spleen, thymus, liver and blood until 10 days PI. Like intact control chickens infected with IBDV, Cy-treated, IBDV-infected chickens suppressed splenocytes responses to ConA from 5 to 10 days PI, suggesting that intact control as well as Cy-treated chickens responded similarly to IBDV infection in the early phase. Following re-infection with IBDV, no detectable secondary antibody response to IBDV as well as IBDV genome in tissues were observed in Cy-treated chickens, while intact control chickens developed vigorous secondary antibody response. Similar to intact control chickens infected with IBDV, Cy-treated chickens after second infection with IBDV did not suppress splenocyte response to ConA. These results suggested that in the absence of detectable anti-IBDV antibodies, protection of Cy-treated chickens from IBDV infection may occur via immunological memory mediated by CMI. We concluded that under normal conditions, IBDV induces a protective antibody response, however, in the absence of antibody, CMI alone is adequate in protecting birds against virulent IBDV.

Topics: Animals; Antibodies, Viral; Antibody Specificity; B-Lymphocytes; Birnaviridae Infections; Chickens; Concanavalin A; Cyclophosphamide; Enzyme-Linked Immunosorbent Assay; Immunosuppressive Agents; Infectious bursal disease virus; Poultry Diseases; Reverse Transcriptase Polymerase Chain Reaction; Specific Pathogen-Free Organisms; Spleen; T-Lymphocytes; Time Factors

We examined the suppressive activity of bursal T cells induced by infectious bursal disease virus (IBDV) in inbred (15x7) and outbred commercial specific-pathogen-free (SPF) chickens. The suppressive activity was measured by the ability of bursal and splenic T cells from IBDV-infected chickens to inhibit mitogenic responses of normal splenocytes. The bursacytes but not the splenocytes of IBDV-infected chickens inhibited the mitogenic responses of normal splenocytes. The mitogenic inhibition by the bursacytes of IBDV-infected chickens was dose-dependent. The suppression was observed both in inbred and non-inbred chickens, and thus, was non MHC-restricted. Cell-sorting experiments revealed that both CD4(+) and CD8(+) cells from the bursa of IBDV-infected chickens, as well as cell-culture supernatants conditioned by these cells, mediated suppression. Suppressor T (Ts) cells may therefore be involved in the immunosuppression induced by IBDV.

Topics: Animals; Birnaviridae Infections; Bursa of Fabricius; CD4-Positive T-Lymphocytes; CD8-Positive T-Lymphocytes; Chick Embryo; Chickens; Concanavalin A; Flow Cytometry; Infectious bursal disease virus; Lymphocyte Activation; Poultry Diseases; Random Allocation; Scintillation Counting; Specific Pathogen-Free Organisms; Spleen

We examined the effects of infectious bursal disease virus (IBDV) on splenic T cells and macrophages. In acute IBDV infection, splenocytes responded poorly to Con A stimulation. However, when T cells were isolated from whole spleen cells, purified T cells responded normally to Con A. This result indicated that functional T cells were present in the spleen but mitogen-induced proliferation of T cells was being suppressed by other cells. Previous studies indicated that soluble factors from suppressor cells may mediate this inhibition of T cell mitogenesis. We thus examined the effects of IBDV on spleen adherent cells. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to quantitate the expression of several cytokine genes in splenic macrophages. In acute IBDV infection, splenic macrophages exhibited enhanced gene expression of type I interferon (IFN), chicken myelomonocytic growth factor (cMGF), an avian homolog of mammalian IL-6, and 9E3/CEF4, an avian homolog of mammalian IL-8. Mitogen-stimulated spleen cell cultures also produced elevated levels of nitric oxide. The elevation of cytokine gene expression by macrophages occurred transiently during the acute phase of viral infection and coincided with in vitro inhibition of T cell mitogenic response of spleen cells.

Topics: Acute Disease; Animals; Avian Proteins; Base Sequence; Birnaviridae Infections; Chickens; Concanavalin A; Cytokines; DNA Primers; Gene Expression; Growth Substances; In Vitro Techniques; Infectious bursal disease virus; Intercellular Signaling Peptides and Proteins; Interferon Type I; Lymphocyte Activation; Macrophages; Nitric Oxide; Polymerase Chain Reaction; Poultry Diseases; Spleen; T-Lymphocytes