Cellular and humoral anti-tumor immune responsiveness in chickens bearing tumors induced by avian sarcoma virus

Nutritional modulation of immune function in broilers

Collaborative research efforts across disciplines typically result in more insight toward the hypothesis being tested due to the omnibus nature of the projects. For example, nutritional experiments evaluating a nutrient response will benefit greatly by incorporating biochemical, physiological, and immunological endpoints for measurement. Clearly, commercial poultry producers do not have the luxury of focusing on specific disciplines when field problems occur. Hence, in practice interplay exists among nutrition, genetics, management, and diseases. Dietary composition impacts immune function of the chicken. As research in the area of nutritional immunology has increased, it is becoming apparent that nutrient needs for immunity do not coincide with those for growth or skeletal tissue accretion. This review is not a comprehensive assessment of nutrient needs for immunity in the chicken. Rather, this review is concerned with nutritional modulation of immunity in broilers that offers insight for nutritionists and researchers to implement nutritional regimens to reduce the severity of disease and to test or validate nutritional regimens that heighten immunity. Nutritional modulation of the hen diet and in ovo nutrient modulation to improve chick immunity and disease resistance are discussed.

v-src induces clonal sarcomas and rapid metastasis following transduction with a replication-defective retrovirus

v-src is an effective carcinogen when expressed from Rous sarcoma virus (RSV) in vivo. Whereas RSV tumors require sustained oncogene expression, their growth is largely a balance between viral recruitment of tissues and host immune destruction of infected cells. We have therefore examined the tumorigenic potential of v-src in the absence of viral recruitment and viral antigen expression. v-src was introduced with high efficiency into chicken wing web tissues using replication-defective (rd) retroviral vectors. Clonal sarcomas were induced rapidly, and, furthermore, v-src potentiated metastatic progression in approximately 0.1%-1% of tumor clones with unexpectedly short latency. rd vectors proved effective not only in transducing v-src into tissues but also as insertional markers of tumor clonality. The rd vector present in most primary and metastatic tumors was a highly truncated form of RSV derived by viral transmission of spliced v-src mRNA; this vector should thus avoid viral recruitment and host anti-viral immune reaction through its complete lack of viral structural genes. Under such conditions v-src maintains strong carcinogenicity in vivo when restricted to clonal tumor growth and can confer rapid metastatic potential on a discrete subset of tumor clones.

Altered pp60src kinase activity in regressing tumors induced by Rous sarcoma virus

Tumors which are induced in chickens by Rous sarcoma virus (RSV) usually grow progressively for several weeks and then regress. pp60src kinase activity was found to be reduced in cultured tumor cells which derived from regressing sarcomas by 60-75% as compared to progressively growing neoplasms. We further found that a cellular pp89 which co-precipitated with pp60src was largely diminished in tumor cells derived from regressing as compared with progressively growing sarcomas. In contrast, immunoprecipitation analyses from membrane or cytosol fractions did not reveal any significant differences between these 2 types of tumor cells in distribution of pp60src. Moreover, partial proteolysis or isoelectric focussing of labelled immunoprecipitated pp60src did not reveal major differences between the 2 tumor cell types. These data indicate that the lack of pp89 cell binding to pp60src in regressing sarcoma cells correlates well with the diminution of the pp60src kinase activity in these cells, but does not affect the transport of pp60src to the plasma membrane.

The nature of immunity to Snyder-Theilen fibrosarcoma virus induced tumors in cats

Snyder-Theilen fibrosarcoma virus (ST-FeSV) induced tumors evoked a vigorous immune response in adolescent cats. The response was characterized histologically by a lymphoid and histiocytic cell infiltrate beginning around the 9th day post inoculation. Hyperemia edema, hemorrhage, and necrosis of the tumors occurred shortly thereafter. Gross regression of the tumors commenced around the 15th day. Viable fibrosarcoma cells could be recovered as almost pure cultures from tumors biopsied on the 9th day. Biopsies taken between days 9 and 15 contained progressively fewer tumor cells and increasing numbers of lymphoid cells, histiocytes, giant cells, and normal fibroblasts. Tumor cells in such mixed cultures did not replicate as fast as normal and died out within 7 to 14 days. Viable tumor cells were not recovered from biopsies taken after day 15. Fibrosarcoma regression was associated with the appearance of tumor cell specific cytotoxic lymphocytes and antibodies in the blood. Cell mediated immunity, as determined by a chromium release assay, consisted of both antibody dependent and independent mechanisms. Fluorescent and complement dependent cytolytic antibodies were detected in the blood at the same time as cytotoxic lymphocytes, but persisted after regression. In a preliminary experiment, serum from tumor regressor cats was injected into susceptible kittens, and the kittens were then challenged with ST-FeSV transformed fibroblasts or whole FeSV. Immune serum did not prevent the appearance of initial growth of tumors, but did slow their subsequent growth and increased the rate of regression. Immune serum had a much more dramatic inhibitory effect on the accompanying retrovirus infection.

Preferential lymphocyte-mediated cytotoxicity of syngeneic target cells in chickens bearing tumors induced by avian sarcoma virus

Splenic lymphocytes from chickens bearing tumors induced by avian sarcoma virus are able to cause the specific killing of cultured avian sarcoma cells. This cytotoxicity appears to follow classical patterns of syngeneic restriction. Little or no specific killing of tumor targets occurred when spleen cells from one inbred line of chickens were tested against allogeneic targets, although syngeneic killing proceeded relatively efficiently. Other patterns of immune reactivity did not appear to be syngeneically restricted. Namely, sera from tumor-bearing hosts were equally reactive in indirect immunofluorescence assays with syngeneic and allogeneic target cells. And, peripheral blood lymphocytes from sensitized hosts could be stimulated equally well by tumor cell culture fluids of allogeneic or syngeneic origin.

Immunological responsiveness against tumors induced by avian sarcoma virus: reduced expression of pp60src kinase activity in regressing tumors

Tumors which are induced in chickens by avian sarcoma virus frequently grow progressively for several weeks and then regress. We showed that tumor cells which are derived from the progressively growing phase of tumor growth produce large quantities of progeny-transforming virus, are reactive with antiviral antibody, and are susceptible to lysis in cell-mediated cytotoxicity assays by splenic lymphocytes of sensitized hosts. In contrast, tumor cells derived from regressing sarcomas are poor producers of progeny virus and are relatively unreactive with both antiviral antibody and sensitized lymphocytes. We further found that pp60src kinase activity was reduced by about 75% in regressing compared with progressively growing tumor cells. The half-lives of directly precipitable pp60src in tumor cells derived from progressively growing and regressing neoplasms were 6 and 1.5 h, respectively. Studies on each of three other cellular enzymes did not reveal any regression-associated decreases in enzyme activity. These data support the notion that expression of adequate levels of long-lived pp60src kinase activity is essential to progressive tumor growth.

Neutralization of pseudotypes of vesicular stomatitis virus by sera from avian retrovirus-infected hosts

We investigated the capacity of lymphocytes and sera from chickens bearing tumors induced by avian sarcoma viruses (ASV) to interact with phenotypically mixed particles of vesicular stomatitis virus (VSV) and ASV. Immune chicken sera were able to specifically neutralize such VSV pseudotypes. This ability could be absorbed out, however, on purified preparations of avian retroviruses, suggesting that reactivity was primarily against avian retrovirus enveloped components. Supernatant fluids containing phenotypically mixed particles were unable to stimulate division of lymphocytes of tumor-bearing hosts, an ability possessed by culture fluids containing native ASV particles. Polyacrylamide gel analysis was unable to resolve any distinct pseudotype protein, which was not present in either of the parental virus types. Treatment with crude preparations of ultraviolet (UV)-irradiated VSV pseudotype material did not afford immunity against subsequent challenge with live ASV.