Presence of viral antigens and antibody in the trachea of chickens infected with avian infectious bronchitis virus

Abstract

SUMMARYFollowing infection of chickens with infectious bronchitis virus (strain M41) viral antigens were detected by immunofluorescence in the basal layer of the trachéal mucosal epithelium for 44 days.The enzyme-linked immunosorbent assay (ELISA) first detected virusspecific antibody in tracheal washes 7 days after infection and at 10 days these antibodies reached a level that was maintained for at least 44 days, although there was considerable variation between chickens. In contrast a neutralisation test did not detect antibody until day 20 ; titres were in the range 2.2 to 3.2 log2 reaching a maximum at day 27. ELISA detected anti-viral IgA in tracheal washes only on day 7, whereas IgG was detected in all samples containing anti-viral antibody.Serum anti-viral antibodies were detected by ELISA at 7 days and reached peak titres at 10 days, which were maintained. In contrast, serum neutralising antibodies were first detected at 10 days and increased to peak titres on day 24.The implications of the differences between the results of ELISA and neutralisation tests are discussed. INTRODUCTIONThe mechanisms of immunity in chickens infected with avian infectious bronchitis virus (IBV) remain poorly understood (Darbyshire, 1981). Humoral antibodies develop and persist for lengthy periods but their titres often correlate poorly with protection against reinfection (Raggi and Lee, 1965). Similarly, cross-challenge experiments in vivo between different strains of the virus often indicate a greater degree of protection than would be expected from the relationships of such strains determined by neutralisation tests in vitro (Raggi and Lee, 1957;Winterfield and Hitchner, 1962).

Detection of infectious bronchitis virus

“…Although the sensitivity of the IFA is usually lower than that of VI, especially in the later stages of the infection, there are several reasons why IFA, in some situations, might show a higher sensitivit y than VI (Hawkes et al, 1983;Yagyu & Ohta, 1990;De Wit et al, 1995). Examples are IBV strains with a poor ability to multiply in vitro, or absence of infectious virus needed for VI but not for IFA, for which only viral proteins need be present (Hawkes et al, 1983;Yagyu & Ohta, 1990).…”

“…Reports of indirect ELISAs show them to be group specific (Garcia & Bankowski, 1981;Marquardt et al, 1981;Zellen & Thorsen, 1987;Perrotta et al, 1988;Karaca et al, 1990;De Wit et al, 1997). Antibodies can first be detected by ELISA within 1 week after vaccination or infection (Marquardt et al, 1981;Mockett & Darbyshire, 1981;Hawkes et al, 1983;Monreal et al, 1985;De Wit et al, 1997, 1998a. This early detection does not automatically lead to a high sensitivit y.…”

“…Examples are IBV strains with a poor ability to multiply in vitro, or absence of infectious virus needed for VI but not for IFA, for which only viral proteins need be present (Hawkes et al, 1983;Yagyu & Ohta, 1990). Also, when two viruses are present at the same time, a large difference in amount or rate of replication of the two viruses could result in impaired replication of one of them.…”

“…Many papers have been published on the duration of IBV infections in the chicken (Hofstad & Yoder, 1966;Doherty, 1967;Colwell & Lukert, 1969;Cook, 1971;Crinion et al, 1971;Jones & Jordan, 1972;Hawkes et al, 1983;Smith et al, 1985;ElHouadfi et al, 1986;Jones & Ambali, 1987;Bumstead et al, 1989;Ambali & Jones, 1990;Otsuki et al, 1990;Nakamura et al, 1991;Owen et al, 1991;Bhattacharjee et al, 1995;Dhinakar Raj & Jones, 1997a;De Wit et al, 1998b). These studies involve a large variety of sampled organs, different virus strains, different doses, etc., and can therefore be expected to present partly conflicting data about the intervals in which the virus can be detected in the various organs.…”

“…Due to the many variations in experimental conditions, test performance and type of antibodies that are detected by the different tests, many different results are reported. However, generally, antibodies can first be detected by ELISA, followed by AGPT and HI test, and last by VNT (Marquardt et al, 1981;Mockett & Darbyshire, 1981;Hawkes et al, 1983;Monreal et al, 1985;De Wit et al, 1997, 1998a.…”