As natural reservoirs of avian influenza viruses, waterfowl play an important role in the generation, spread and enzootic transmission of avian influenza, report Haihong Kang and colleagues at Nanjing Agricultural University in the journal, Poultry Science.

To prevent avian influenza in waterfowl through a simple, non-invasive and needle-free route, they immunised ducks orally with an inactivated avian influenza virus (H9N2; IAIV) combined with CpG DNA and high-dose glucose. They then investigated the local and systemic immune responses of the ducks. In addition, immune protection was assayed after viral challenge.

After the oral administration of IAIV combined with CpG DNA and glucose, the expression levels of interleukin-2 and interleukin-6 in the small intestine tissues increased significantly in the early period after booster immunisation relative to the levels after immunisation with IAIV and a single adjuvant.

Significant increases were also observed in the IgA and IgG antibody levels in the local intestinal tract tissues and serum at weeks 3, 5 and 7 after the first immunisation.

Furthermore, enhanced haemagglutination inhibition titres were also detected in serum samples taken between the third and seventh weeks after immunisation with IAIV and both adjuvants.

In the viral challenge and transmission study, the prior administration of IAIV combined with both CpG DNA and glucose reduced the viral titres observed for the cloaca swabs and colon tissues of challenged ducks and prevented virus transmission between ducks.

Kang and conlleagues conclude that the combination of CpG DNA and high-dose glucose can improve immunisation with inactivated H9N2 virus by enhancing the local and systemic immune responses and reducing viral shedding.

Reference

^{Kang H., H. Wang, Q. Yu and Q. Yang. 2013. A novel combined adjuvant strongly enhances mucosal and systemic immunity to low pathogenic avian influenza after oral immunization in ducks. Poult. Sci. 92(6):1543-1551. doi: 10.3382/ps.2012-03000}