Pathogenicity Studies of an Arkansas Variant Infectious Bursal Disease Virus

Abstract

A variant infectious bursal disease virus (IBDV), IBDV-s977, was blind passaged in cell culture, plaque purified, and attenuated by serial passage at a high multiplicity of infection (MOI) in chick embryo fibroblasts (CEF). Cell culture passages of virus caused less bursal atrophy and splenomegaly than did the original isolate and retained immunogenicity; however, virus tended to persist for a longer time in the bursa and spleen of birds infected with the highest CEF passages. Antibody to both low MOI and high MOI passages of IBDV-s977 poorly neutralized virus that was isolated from bursal tissue 28 days postinfection (PI). The spleens of chickens infected with the eighteenth CEF passage were negative for virus at 3 and 7 days PI but had high titers of virus at 14 and 28 days PI. There was also more virus in the bursa of birds infected with the fifteenth and eighteenth CEF passages at 28 days PI than at 7 or 14 days PI. Defective interference (DI) was demonstrated when cell cultures were coinfected with a constant amount of low MOI virus and serial dilutions of high MOI virus. There was an increase in interference score with increased passage number in CEF, and there was more interference in virus passaged at a high MOI. There was an inverse relationship between interference score and bursal lesion score and splenomegaly at 7 days PI, indicating that DI particles may be involved in virus attenuation. There was a positive relationship between interference and viral persistence in the bursa and spleen at 28 days PI. Antiserum to s977 was shown to enhance the nonlytic replication of s977 in CEF, presumably within macrophages, providing a possible mechanism for the pathotypic variation seen in emerging strains of IBDV.

Characterization of the antigenic, immunogenic, and pathogenic variation of infectious bursal disease virus due to propagation in different host systems (bursa, embryo, and cell culture). III. Pathogenicity

“…Results obtained in the present study were similar to those shown by other researchers who reported a decrease in the pathogenicity of IBDV strains propagated in embryos and cell cultures (Müller et al, 1986;Becht & Müller, 1991;Ismail & Saif, 1991;Tsai & Saif, 1992;Tanimura et al, 1995;Bayyari et al, 1996;Hassan & Saif, 1996;Hassan et al, 1996a,b;Takase et al, 1996;Yamaguchi et al, 1996;Chen et al, 1998). However, antigenic and/or immunogenic changes were not recognized in these studies.…”

“…Differences in the relative pathogenicity of IBDV that are apparently related to the host system utilized have been previously reported (Müller et al, 1986;Becht & Müller, 1991;Ismail & Saif, 1991;Tsai & Saif, 1992;Tanimura et al, 1995;Bayyari et al, 1996;Hassan et al, 1996a,b;Hassan & Saif, 1996;Takase et al, 1996;Yamaguchi et al, 1996;Chen et al, 1998;Fussell, 1998). However, these authors did not correlate changes in relative pathogenicity with either antigenic or immunogenic differences.…”

Characterization of the antigenic, immunogenic, and pathogenic variation of infectious bursal disease virus due to propagation in different host systems (bursa, embryo, and cell culture). I. Antigenicity and immunogenicity

“…Pathogenic, antigenic, or immunogenic variation induced by propagation in different host systems has been addressed in other studies (Ismail & Saif, 1991;Tsai & Saif, 1992;Bayyari et al, 1996a; IBDV antigenicity and immunogenicity 467 Hassan & Saif, 1996;Hassan et al, 1996a,b;Yamaguchi et al, 1996). Although these studies documented that changes in the pathogenicity of IBDV occurred following propagation in different host systems, antigenic and/or immunogenic changes were not described.…”

“…The effect of host systems on the antigenicity and/or immunogenicity of IBDV is less clear. Tsai & Saif (1992), Bayyari et al (1996a), Hassan et al (1996a,b), Hassan & Saif (1996), and Yamaguchi et al (1996) have indicated that propagation of IBDV in cell culture does not alter its antigenic configuration .…”

“…The role that different propagation methods have in modifying the pathogenicity of infectious bursal disease virus (IBDV) is widely recognized Becht & Müller, 1991;Ismail & Saif, 1991;Tsai & Saif, 1992;Tanimura et al, 1995;Bayyari et al, 1996a;Hassan & Saif, 1996;Hassan et al, 1996a,b;Takase et al, 1996;Yamaguchi et al, 1996;Chen et al, 1998;Fussell, 1998;Van den Berg et al, 2000;Abdel-Alim & Saif, 2001a,b;Nagarajan et al, 2001;Smiley & Jackwood, 2001). Viruses passaged in birds maintain their pathogenicit y, whereas viruses propagated in embryos may maintain or lose their pathogenicity.…”