In vivo effects of chicken myelomonocytic growth factor: delivery via a viral vector

We have constructed a recombinant fowlpox virus (FPV) that expresses chicken myelomonocytic growth factor (cMGF). Administration of this construct (fp/cMGF) to 1-day-old chicks resulted in a marked and sustained increase in the number of circulating blood monocytes compared with chicks infected with the parental FPV strain (fp/M3). Blood monocyte numbers were elevated within 4 days of fp/cMGF infection, reached maximal levels at day 9, and returned to normal levels by day 16. During the peak response, approximately 35% of blood leukocytes were monocytes, compared with 4 to 7% in uninfected control birds. Infection with fp/M3 also resulted in a detectable increase in monocyte numbers; however, the effect was less dramatic. Compared with fp/M3, fp/cMGF consistently induced two- to threefold higher monocyte numbers, and the period of monocytosis was longer (10 vs 5 days). No other specific changes in white blood cell populations were observed. Associated with the increase in the number of monocytes was an increase in their state of activation, as measured by the ability to produce nitric oxide (NO) and to phagocytose latex beads. Blood monocytes from birds infected with fp/cMGF produced about 6 times as much NO per cell compared with monocytes from fp/M3-infected birds. Monocytes from normal birds failed to produce detectable levels of NO. Furthermore, cMGF treatment specifically induced enhanced phagocytic activity in blood monocytes. Overall, these results indicate that viral vectors are suitable for the delivery of biologically active cytokines and that they allow an assessment of cytokine activities in vivo.

In vivo effects of chicken myelomonocytic growth factor: delivery via a viral vector

We have constructed a recombinant fowlpox virus (FPV) that expresses chicken myelomonocytic growth factor (cMGF). Administration of this construct (fp/cMGF) to 1-day-old chicks resulted in a marked and sustained increase in the number of circulating blood monocytes compared with chicks infected with the parental FPV strain (fp/M3). Blood monocyte numbers were elevated within 4 days of fp/cMGF infection, reached maximal levels at day 9, and returned to normal levels by day 16. During the peak response, approximately 35% of blood leukocytes were monocytes, compared with 4 to 7% in uninfected control birds. Infection with fp/M3 also resulted in a detectable increase in monocyte numbers; however, the effect was less dramatic. Compared with fp/M3, fp/cMGF consistently induced two- to threefold higher monocyte numbers, and the period of monocytosis was longer (10 vs 5 days). No other specific changes in white blood cell populations were observed. Associated with the increase in the number of monocytes was an increase in their state of activation, as measured by the ability to produce nitric oxide (NO) and to phagocytose latex beads. Blood monocytes from birds infected with fp/cMGF produced about 6 times as much NO per cell compared with monocytes from fp/M3-infected birds. Monocytes from normal birds failed to produce detectable levels of NO. Furthermore, cMGF treatment specifically induced enhanced phagocytic activity in blood monocytes. Overall, these results indicate that viral vectors are suitable for the delivery of biologically active cytokines and that they allow an assessment of cytokine activities in vivo.

In vitro characterization of a novel avian haemopoietic growth factor derived from stromal cells

To better define the role of the chicken haemopoietic microenvironment in supporting haemopoiesis, a continuous cell line was generated by RSV transformation of avian spleen stromal cells (SSL-1). Supernatants from this line were found to contain haemopoietic growth factor activity as measured by the ability to induce proliferation and differentiation of precursor cells present in embryonic and post-hatched haemopoietic tissues. Comparison of cultures grown in the presence of cMGF and SSL-1 conditioned media (CM) revealed that both cytokine sources induced similar types of cell populations. Both sources supported the proliferation of predominantly macrophage-like cells based on colony morphology, differential staining, non-specific esterase staining, and phagocytosis activity. Interestingly, SSL-1 does not express any message for cMGF, nor does it secrete any IL-2 or interferon activities suggesting that the growth factor activities seen in SSL-1 are novel.

Development of T cell immune responsiveness in the chicken

Chickens are highly susceptible to infection by opportunistic pathogens during the first few days after hatching. This observation has generally been attributed to an immaturity of the immune system; however, the mechanisms responsible are not known. This study investigated the ability of T cells from chickens of various ages to respond to immune stimulation. Splenic T cells were cultured in vitro and stimulated with various mitogens including Con A, PHA and monoclonal anti-CD3 antibody. T cells obtained from adult chickens proliferated extensively and produced high levels of IL-2, haemopoietic growth factors and IFN following stimulation. In contrast, it was found that T cells from 1 day old chickens failed to proliferate and secrete cytokines when similarly cultured. Reactivity to mitogens gradually developed between days 2 and 4, and by 1 week of age the level of responsiveness was equivalent to that observed with T cells obtained from adult chickens. Whereas T cells from 1 day old chicks were found to be phenotypically mature and capable of binding mitogens as effectively as T cells from adult birds, they were functionally immature as assessed by their inability to proliferate or produce cytokines following immune stimulation. In addition, cells present in the spleen of 1 day old chicks constitutively produced a soluble inhibitor that prevented the proliferation of stimulated adult T cells. The production of inhibitor decreased dramatically by the second day post-hatching which coincided with an enhanced ability of T cells to respond to immune stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoclonal antibodies to three structural proteins of avian infectious bronchitis virus: characterization of epitopes and antigenic differentiation of Australian strains

Ten monoclonal antibodies (MAbs) directed against three structural proteins of infectious bronchitis viruses (IBV), the peplomer (S), membrane (M) and nucleocapsid (N) proteins, were characterized and used to determine the antigenic relationship between Australian IBV strains. One MAb (MAb 5) was directed against an epitope on the S1 subunit of the peplomer, another (MAb 2) against an epitope on the M glycoprotein and eight MAbs (MAbs 1, 7, 9, 16, 24, 26, 27 and 51) were directed against seven non-overlapping epitopes on the N protein. None of the MAbs neutralized infectivity or inhibited haemagglutination of the virus. Conservation of the nine epitopes detected by these MAbs was determined in 13 serotypes of Australian IBV strains. Only epitope 5 on the S1 subunit of the peplomer was conserved in all strains. Epitope 2 on the M protein showed a high degree of conservation although this epitope was absent from four strains. None of the eight epitopes on the N proteins was conserved in all IBV strains but four epitopes (1, 16, 24 and 27) showed a high degree of conservation. Epitope 9 on the N protein was present only in IBV strains of one serotype whereas epitope 7 on the N protein distinguished vaccine viruses of serotype B from other IBV strains. The presence or absence of nine epitopes on three structural proteins differentiated IBV strains into five antigenic groups.

Production and characterization of monoclonal antibodies specific for bovine gamma-interferon

Nine stable hybridoma cell lines were established which secreted specific monoclonal antibodies (MAbs) to bovine gamma-interferon (BoIFN-gamma). Specific binding of each of the MAbs to recombinant BoIFN-gamma (rBoIFN-gamma) was demonstrated in an indirect ELISA, whilst none of the MAbs bound to rBoIFN-alpha or rBoIFN-beta. In a Western blot the MAbs reacted with the 16 kDa and 32 kDa polypeptides present in rBoIFN-gamma preparations. Competitive ELISA's showed that four MAbs bound to one epitope on rBoIFN-gamma, and the other five MAbs bound to a separate epitope. Two MAbs, each recognising different epitopes, were shown to neutralise the anti-viral activity of natural BoIFN-gamma.

Quantitation by ELISA of pili and sheep antibodies to the pili of Bacteroides nodosus

ELISA systems have been developed to quantitate the isotypic antibody response of sheep naturally infected with B. nodosus isolate 198 or injected with pili from isolate 198 in oil emulsion vaccines. The predominant humoral antibody detected following vaccination was IgG1, with substantially lower amounts of IgG2 and IgM. The antibody response was relatively specific for the pilus antigen from isolate 198. Although weak cross reactivities were detected with antiserums to some other isolates, ELISA IgG antibody titres in excess of 200 offer a tentative identification of the isolates of B. nodosus involved in natural outbreaks of footrot. A related ELISA was also developed to quantitate the amount of pili in cell suspensions and crude preparations of pili used in vaccines.