Effects of an Arkansas Strain of Infectious Bronchitis Vaccine on the Head-Associated Lymphoid Tissue (HALT)

Abstract

Chicks were vaccinated with an Arkansas strain of infectious bronchitis virus (IBV) vaccine when they were 1 day (Trial 1) or 4 weeks old (Trial 2). Starting at 4 weeks 3 days of age, chicks in both trials were subjected to an assay that measures the immunofunctional response of the gland of Harder (GH), one of the components of the head-associated lymphoid tissue (HALT). The assay involved multiple ocular exposures to killed Brucella abortus antigen, after which tears were collected and titered for antibodies to B. abortus. Following this, select tissues from vaccinated and unvaccinated chicks were collected and examined microscopically for specific lesions. Both functional and structural alterations were detected in the HALT of IBV-vaccinated chicks. Antibody titers to B. abortus in vaccinated chicks were significantly lower (P less than 0.05) than in unvaccinated controls. Structurally, there were elevations (P less than 0.01) in the number of lymphoid cells and follicles found in the mucosal lining of the nasal cavity. This occurred in the vaccinated chicks of both trials. Otherwise, histologic changes were confined to the chicks vaccinated at 4 weeks of age (Trial 2). In that trial, there were elevations in lymphoid-cell and follicle numbers in the eyelid (P less than 0.01) and lacrimal gland (P less than 0.05).

Head-associated lymphoid tissue [HALT] of the chicken: characterization of lymphocytes

“…Sheep red blood cells given intraocularly resulted in plaque forming cells from the Harderian gland but no plaque forming cells were formed from the spleen four days post inoculation (19). Similar results have been found with other antigens such as bovine serum albumin (21 days post inoculation) (4), Newcastle disease virus (NDV) (7 days post inoculation) (20), infectious bronchitis virus (7 to 28 days post inoculation) (8,18,20), and Mycoplasma gallisepticum (7 days post inoculation) (20).…”

“…The immunological role of the Harderian gland has been reported to act primarily at the local level (4,8,(18)(19)(20). Sheep red blood cells given intravenously resulted in no plaque forming cells from the Harderian gland, whereas plaque forming cells developed in the spleen four days post inoculation (19).…”

“…In the same study (Montgomery et al, 1991), chickens with their HG left intact were inoculated with both infectious bronchitis virus and B. abortus. The dacryoantibody titer produced from this group of birds was significantly lower than positive control hatch-mates (HG intact and B. abortus inoculated).…”

“…The immunological role of the HG has been considered to be primarily at the local humoral level Montgomery et al, 1991;Mueller et al, 1971;Powell et al, 1979). Although, cell-mediated immune functions have been investigated, Sundick et al (1973) found that lymphocytes harvested from the HG failed to have a graft vs. host response on recipient chorioallantoic membranes.…”

“…Cell mediated immunity, moreover, may provide better protection against certain disease agents Bhogal, 1989) than systemic humoral response (Alexander, 1989) or local humoral response Montgomery and Maslin, 1992;Montgomery et al, 1991;Parry and Aitken, 1977;Powell et al, 1979). McLelland, 1991).…”