Formulation with CpG oligodeoxynucleotides prevents induction of pulmonary immunopathology following priming with formalin-inactivated or commercial killed bovine respiratory syncytial virus vaccine

Commercial killed bovine respiratory syncytial virus (K-BRSV) and formalin-inactivated BRSV (FI-BRSV) tend to induce Th2-type immune responses, which may not be protective and may even be detrimental during subsequent exposure to the virus. In this study we assessed the ability of CpG oligodeoxynucleotides (ODNs) to aid in the generation of effective and protective BRSV-specific immune responses. Mice were immunized subcutaneously with FI-BRSV formulated with CpG ODN, Emulsigen (Em), CpG ODN and Em, or non-CpG ODN and Em. Two additional groups were immunized with K-BRSV or K-BRSV and CpG ODN. After two vaccinations, the mice were challenged with BRSV. FI-BRSV induced Th2-biased immune responses characterized by production of serum immunoglobulin G1 (IgG1) and IgE, as well as interleukin-4 (IL-4), by in vitro-restimulated splenocytes. Formulation of FI-BRSV with CpG ODN, but not with non-CpG ODN, enhanced serum IgG2a and IFN-gamma production by splenocytes, whereas serum IgE was reduced. Although the immune response induced by K-BRSV was not as strongly Th2 biased, the addition of CpG ODN to this commercial vaccine also resulted in a more Th1-type response. Furthermore, the addition of CpG ODN to the BRSV vaccine formulations resulted in enhanced neutralizing antibody responses. Significant production of IL-5, eotaxin, and eosinophilia was observed in the lungs of FI-BRSV- and K-BRSV-immunized mice. However, IL-5 and eotaxin levels, as well as the number of eosinophils, were decreased in the mice vaccinated with the CpG ODN-formulated vaccines. Finally, when formulated with CpG ODN, both FI-BRSV and K-BRSV significantly reduced virus production after challenge with BRSV.