Immune Complex Vaccine Research Articles

Field Studies on Equine Influenza Vaccination Regimes in Thoroughbred Foals and Yearlings

SUMMARYThe purpose of these studies was to examine the response of Thoroughbred foals and yearlings to different influenza vaccines and vaccination regimes. The horses’ antibody levels against haemagglutinin, an established correlate of protection were measured by haemagglutination inhibition. The first study investigated the extent to which maternal antibodies interfered with the humoral response to a subunit vaccine. The findings suggest that repeat vaccination in the face of maternal antibodies may induce tolerance as defined by serological testing. The second study compared the immune response elicited by a subunit immune stimulating complex (ISCOM) vaccine, an inactivated whole virus vaccine and the same product containing equine herpesviruses and equine reoviruses in addition to equine influenza virus. The monovalent vaccine induced a significantly better response than the ISCOM or the multivalent vaccine. The final study demonstrated that the inclusion of an additional booster vaccination, between the second and third vaccination recommended by the vaccine manufacturers and required under the rules of racing in certain countries, is of benefit to young horses. Since these studies were performed, several of the vaccines have been updated with more recent virus strains in line with WHO/OIE recommendations. However, the general principles investigated in the studies remain relevant to these vaccines.

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

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.

Efficacy of a Novel Infectious Bursal Disease Virus Immune Complex Vaccine in Broiler Chickens

Two experiments were conducted to test the efficacy of a novel infectious bursal disease virus (IBDV) vaccine in broiler chickens with maternal IBDV immunity. The IBDV vaccine was formulated by mixing IBDV strain 2512 with bursal disease antibodies (BDA) to produce the IBDV-BDA complex vaccine. In Expt. I, 1-day-old Cobb x Cobb broiler chickens were vaccinated subcutaneously with either IBDV-BDA or commercial live intermediate IBDV vaccine (vaccine A) or were left unvaccinated. In Expt. 2, the vaccine A group was not included; instead, IBDV strain 2512 was included. Chickens were maintained in isolation houses. On day 28 (Expt. 1) and day 32 (Expt. 2) of age, chickens from each group were challenged with a standard USDA IBDV (STC strain) challenge. Challenged and unchallenged chickens were evaluated for their bursa/body weight ratios and antibody titers 3 days post-challenge. Bursae collected from Expt. 2 were examined histologically to evaluate bursal lesions and confirm gross examination. None of the unvaccinated chickens was protected against the challenge virus as evidenced by the presence of acute bursal lesions (edema/hemorrhage). All chickens receiving the IBDV-BDA complex or the IBDV strain 2512 (Expt. 2) were protected from the challenge virus as evidenced by no acute bursal lesions. Additionally, chickens receiving the IBDV-BDA complex vaccine or the IBDV strain 2512 had antibody titers to IBDV, indication the presence of an active immune response. In Expt. 1, chickens vaccinated with vaccine A and challenged had bursal lesions similar to those observed in the unvaccinated, challenged chickens. These chickens also showed no indication of active immunity against the virus. These results suggest that the 1-day-of-age-administered IBDV-BDA complex vaccine can induce active immunity and protection against a standard IBDV challenge in the face of variable levels of maternal IBDV immunity.

A method for increasing the sensitivity of the hemagglutination-inhibition test with equine influenza virus

SUMMARYThe purpose of these studies was to examine the response of Thoroughbred foals and yearlings to different influenza vaccines and vaccination regimes. The horses’ antibody levels against haemagglutinin, an established correlate of protection were measured by haemagglutination inhibition. The first study investigated the extent to which maternal antibodies interfered with the humoral response to a subunit vaccine. The findings suggest that repeat vaccination in the face of maternal antibodies may induce tolerance as defined by serological testing. The second study compared the immune response elicited by a subunit immune stimulating complex (ISCOM) vaccine, an inactivated whole virus vaccine and the same product containing equine herpesviruses and equine reoviruses in addition to equine influenza virus. The monovalent vaccine induced a significantly better response than the ISCOM or the multivalent vaccine. The final study demonstrated that the inclusion of an additional booster vaccination, between the second and third vaccination recommended by the vaccine manufacturers and required under the rules of racing in certain countries, is of benefit to young horses. Since these studies were performed, several of the vaccines have been updated with more recent virus strains in line with WHO/OIE recommendations. However, the general principles investigated in the studies remain relevant to these vaccines.