Immunoadjuvant activities of E. coli- and plasmid-expressed recombinant chicken IFN-alpha/beta, IFN-gamma and IL-1beta in 1-day- and 3-week-old chickens.

In the present study we assessed the capacity of recombinant E. coli- or plasmid-expressed chicken interferons (IFN) and chicken IL-1beta, to exert immunostimulatory activities for humoral immune responses, in day-old and adult chickens. We observed that both recombinant E. coli-expressed chicken IFN-alpha/beta and IFN-gamma facilitated the induction of a primary and also a secondary antibody response, using tetanus toxoid (TT) as a bacterial model antigen, in immunologically mature 3-week-old chickens. In contrast, no improvement of antibody either type of chicken IFN was co-injected with inactivated Infectious Bursal Disease Virus (IBDV) antigen. TT-specific antibody formation was marginally increased by co-injection of recombinant E. coli-expressed chicken IL-1beta. Combined administration of IFN-alpha/beta plus IFN-gamma or IL-beta increased responses to TT in an additive, but not synergistic fashion. Remarkably, no augmentation of antibody responses specific for TT, nor IBDV, was noted in day-old birds, receiving IFN-alpha/beta or IFN-gamma as adjuvant. Also, intramuscular immunization of 3-week-old birds, using plasmids encoding IFN-alpha/beta together with TT protein antigen, significantly increased the speed and magnitude of TT-specific antibody responses. Plasmids encoding chicken IL-beta or IFN-gamma had a minimal or inhibitory effect, respectively. These data indicate a potential for chicken cytokines as immunoadjuvant for particular types of chicken vaccine antigens.

IFN-gamma receptor-deficient mice generate antiviral Th1-characteristic cytokine profiles but altered antibody responses.

The lymphokine IFN-gamma is a pleiotropic immunomodulator and possesses intrinsic antiviral activity. We studied its significance in the development of antiviral immune responses by using IFN-gamma receptor-deficient (IFN-gamma R-/-) mice. After inoculation with live attenuated pseudorabies virus (PRV), the mutant mice showed no infectivity titers in various tissues, and transient viral Ag expression only in the spleen, similar as in wild-type mice. However, the absence of the IFN-gamma R resulted in increased proliferative splenocyte responses. The PRV-immune animals showed a normal IFN-gamma and IL-2 production, without detectable IL-4, and with decreased IL-10 secretion in response to viral Ag or Con A. Immunohistochemically, an increased ratio of IFN-gamma:IL-4-producing spleen cells was found. After immunization with either live attenuated or inactivated PRV, IFN-gamma R-/- mice produced significantly less antiviral Ab, and more succumbed to challenge infection than the intact control animals. The reduction in Ab titers in the mutant mice correlated with lower protection by their sera in transfer experiments. Our data demonstrate that ablation of the IFN-gamma receptor surprisingly does not inhibit the generation of antiviral Th1-type and increase Th2-type cytokine responses. However, it profoundly impairs the generation of protective antiviral Ab.

Detection of mucosal immune responses in chickens after immunization or infection.

In order to measure mucosal antibody responses in the chicken intestine an ELISA-based assay was developed that was able to detect antigen-specific antibodies in an isotype-specific way. Locally produced antibodies could be detected after overnight culture at 37 degrees C. In particular the production of IgA, more than IgM and IgG, was significantly increased by immunization of the animals with K99 pilus antigen or by infection with Eimeria tenella parasites. Data presented here indicate that the assay can be used to estimate the magnitude of the mucosal antibody response in experimental conditions where antibody levels in bile or intestinal contents were not significantly changed.

Vaccination of piglets against post-weaning "E. coli" enterotoxicosis.

E. coli enterotoxicosis is one of the main causes of neonatal diarrhea in piglets. For their protection against this disease a vaccine has been prepared based on K88 and LT. Pregnant sows were vaccinated, thereby transferring passive immunity to their offspring through colostrum and milk. Protection was obtained in terms of decrease in mortality, occurrence of diarrhea and excretion of enteropathogenic bacteria. Piglets from non-immune sows could be immunized shortly after birth. However, piglets from immune sows vaccinated once after birth failed to show an active antibody response; only by two vaccinations, 4 weeks apart, was an antibody formation induced. From the results presented it is concluded that a proper vaccination schedule makes it possible to immunize piglets from both immune and non-immune sows and induce protection against post-weaning diarrhea.

Thymus-derived inhibitor of lymphocyte proliferation. II. Tissue specificity in vitro and in vivo.

A thymus crude factor (TCF) isolated from bovine thymus tissue has been tested for its effects on the proliferation of various murine cells. Specific inhibition in vitro has been found for DNA synthesis in murine T and B lymphocytes which appears not to be based on cytotoxicity. Moreover, TCF, when administered to mice, also interferes with the DNA synthesis in lymphoid tissue in vivo. Our data are suggestive for the presence in TCF of an endogenous 'chalone-like' inhibitor of lymphoid cell proliferation in vitro and in vivo.

Thymus derived inhibitor of lymphocyte proliferation. I. Isolation and assessment of tissue specificity.

Preparations from bovine thymus tissue were analyzed for their inhibitory effects during in vitro lymphocyte proliferation. The results indicate that these preparations strongly inhibit DNA synthesis in stimulated human peripheral lymphocytes, bone marrow cells, thymocytes and lymphoblastoid cells. This inhibition was dose-dependent and not due to cytotoxicity of the preparations. No inhibition was found of the spontaneous proliferation of HeLa cells and human fibroblasts indicating that the inhibitory effect was specific for proliferating lymphocytes. Control preparations from bovine liver or kidney did not show any suppression in the test systems used.