Enhancing immune responses to inactivated porcine parvovirus oil emulsion vaccine by co-inoculating porcine transfer factor in mice

Inactivated porcine parvovirus (PPV) vaccines are available commercially and widely used in the breeding herds. However, inactivated PPV vaccines have deficiencies in induction of specific cellular immune response. Transfer factor (TF) is a material that obtained from the leukocytes, and is a novel immune-stimulatory reagent that as a modulator of the immune system. In this study, the immunogenicity of PPV oil emulsion vaccine and the immuno-regulatory activities of TF were investigated. The inactivated PPV oil emulsion vaccines with or without TF were inoculated into BALB/c mice by subcutaneous injection. Then humoral and cellular immune responses were evaluated by indirect enzyme-linked immunosorbent assays (ELISA), fluorescence-activated cell sorter analyses (FACS). The results showed that the PPV specific immune responses could be evoked in mice by inoculating with PPV oil emulsion vaccine alone or by co-inoculation with TF. The cellular immune response levels in the co-inoculation groups were higher than those groups receiving the PPV oil emulsion vaccine alone, with the phenomena of higher level of IFN-γ, a little IL-6 and a trace of IL-4 in serum, and a vigorous T-cell response. However, there was no significant difference in antibody titers between TF synergy inactivated vaccine and the inactivated vaccine group (P > 0.05). In conclusion, these results suggest that TF possess better cellular immune-enhancing capability and would be exploited into an effective immune-adjuvant for inactivated vaccines.

► Transfer factor (TF) could be used as adjuvant of PPV oil emulsion vaccine.
► Co-inoculating TF with PPV oil vaccine could increase IL-4, IL-6 and IFN-γ secretion.
► Vaccination with TF could increase the number of T-lymphocytes subpopulations.
► The cellular immunities could be enhanced by co-inoculating TF in mice.
► TF has little influence on the specific humoral immune responses.