The working mechanism of an immune complex vaccine that protects chickens against infectious bursal disease

Abstract

The role of immune complexes (Icx) in B-cell memory formation and affinity maturation allow for their potential use as vaccines. Recently, a new immune complex vaccine has been developed that is currently under field trials conducted in commercial poultry. This immune complex vaccine is developed by mixing live intermediate plus infectious bursal disease virus (IBDV) with hyperimmune IBDV chicken serum (IBDV-Icx vaccine). Here we have investigated the infectivity of this vaccine as well as the native IBDV (uncomplexed) vaccine in terms of differences in target organs, in target cells and speed of virus replication. At various days after inoculation on day 18 of incubation (in ovo) with either one dose of virus alone or the IBDV-Icx vaccine, the replication of IBDV and the frequency of B cells and other leucocyte populations were examined in the bursa of Fabricius, spleen, and thymus using immunocytochemistry. With both vaccines, IBDV was detected associated with B cells, macrophages and follicular dendritic cells (FDC) in bursa and spleen, although complexing IBDV with specific antibodies caused a delay in virus detection of about 5 days. Most remarkable was the low level of depletion of bursal and splenic B cells in IBDV-Icx vaccinated chickens. Furthermore, in ovo inoculation with the IBDV-Icx vaccine induced more germinal centres in the spleen and larger amounts of IBDV were localized on both splenic and bursal FDC. From these results we hypothesize that the working mechanism of the IBDV-Icx vaccine is related to its specific cellular interaction with FDC in spleen and bursa.

Infectious Bursal Disease: Pathogenicity and Immunogenicity of Vaccines

“…The immune-complex vaccine, on the other hand, is innovative compared with conventional live vaccines because the vaccine virus is coated with anti-IBD antibodies, and when administered to one-day-old chicks, its pathological effects are delayed up to one week, during which the level of maternal antibodies is greatly reduced (Haddad et al, 1997;Jeurissen et al, 1998).…”

“…Despite the BF lesions caused by immune-complex vaccines, some researchers stated that the vaccine antibodies may reduce the pathogenicity of the virus, resulting in less severe depletion of B lymphocytes when compared with live vaccines with the same virus strain (Haddad et al, 1997;Jeurissen et al, 1998). On the other hand, Moraes et al (2004) recommends caution when using live vaccines that may cause BF lesions, as the recovery of bursal follicles may be only partial.…”

Comparison ofin ovoand post‐hatch vaccination with particular reference to infectious bursal disease. A review

“…The amount of antibody in the vaccine formula does not neutralize the virus but is sufficient to delay its onset of replication, as compared to the same virus used without antiserum (41).…”

Chicken recombinant antibodies against infectious bursal disease virus are able to form antibody–virus immune complex

“…Initially, the VN capacity of rAb was assayed in ovo since it is an easier and cheaper method in comparison with in vivo assays. An embryo-adapted IBDV strain Bv was used as this virus has already been used in the formulation of Icx (Jeurissen et al ., 1998). The majority of rAb with VN capacity in CEF also had VN ability in ovo and completely neutralized Bv, preventing both virus replication and embryo death.…”

“…Demonstration of VN capacity of rAb in 18-day old embryonated eggs. Four groups, each of 40 SPF eggs at 18 days of incubation, were inoculated with 0.2 ml inoculum as previously described (Jeurissen et al ., 1998). In brief, eggs were swabbed with a solution of iodine, and 0.2 ml inoculum was administered through a hole in the middle of the blunt end of the eggs using a 23-gauge needle inserted two-thirds of its length into the egg.…”