Potentiation of FMD vaccines with polycationic-nucleic acid complexes

Comparative efficacy of virus like particle (VLP) vaccine of foot-and-mouth-disease virus (FMDV) type O adjuvanted with poly I:C or CpG in guinea pigs

Foot-and-mouth disease (FMD) is one of the most contagious and economically important diseases of cloven-hoofed livestock. Currently used inactivated FMD vaccines have short lived immunity besides risk of handling live virus. We studied recombinant FMD virus like particles (VLPs) encoded by FMDV type O/IND/R2/75 polyprotein genes expressed in Sf9 cells and adjuvanted with CpG or Poly I:C in inducing protective immune response in guinea pigs. Guinea pigs immunized with VLP + CpG vaccine had shown markedly higher cell mediated immunity (CMI) in comparison to the conventional vaccine group as evident from higher levels of IgG2 than IgG1. Although the humoral response was less in VLP + CpG compared to conventional vaccine, the lymphocyte stimulation index was more in VLP + CpG compared to conventional and VLP + Poly I:C vaccine groups. Finally the challenge experiments on 28 and 56 dpv had shown 75% protection in VLP + CpG immunized guinea pigs primary and boosted animals, while 50% and 62% protection in VLP + Poly I:C in primary and boosted animals, respectively. In conclusion, CpG adjuvant was found to be superior followed by ISA206 and Poly I:C in eliciting protection in VLP based FMD vaccines in guinea pigs.

Improved neutralising antibody response against foot-and-mouth-disease virus in mice inoculated with a multi-epitope peptide vaccine using polyinosinic and poly-cytidylic acid as an adjuvant

A peptide-based vaccine for foot-and-mouth disease (FMD) was designed. The peptide immunogen had a G-H loop domain optimised for immunogenicity and broad-spectrum antigenicity to different lineages of serotype-O FMD viruses (FMDVs). Polyinosinic and poly-cytidylic acid [poly (I:C)] was used as the adjuvant to overcome the low humoral antibody levels often observed in association with peptide-based vaccines. The multi-epitope peptide alone induced the secretion of a certain level of neutralising antibodies in mice. In contrast, co-administration of the multi-epitope peptide with poly (I:C) induced the secretion of a significantly higher level of neutralising antibodies (P<0.005). Indeed, the resultant level was slightly higher even than that induced by the inactivated vaccine (P>0.05). These initial results indicate that poly (I:C) is highly effective as an adjuvant for use with the FMDV multi-epitope peptide vaccine. This combination could yield a promising vaccine for the prevention and control of FMD. Further study is needed to evaluate the efficiency of this combination on animals susceptible naturally to FMDV.

Adjuvants for porcine reproductive and respiratory syndrome virus vaccines

This review deals with present and past efforts in utilization of vaccine adjuvants for porcine reproductive and respiratory syndrome virus (PRRSV) vaccines. PRRSV vaccines elicit delayed and weak cell-mediated immune (CMI) and antibody responses after vaccination. Several kinds of vaccine adjuvants have been utilized to accelerate and magnify immune responses to PRRSV vaccines. These adjuvants include cytokines, chemical reagents, and bacterial products. Of 11 vaccine adjuvants tested, five (i.e. interleukin-2 (IL-2), IL-12, interferon alpha (IFNalpha), polyinosinic and polycytidylic acid, and cytidine-phosphate-guanosine oligodeoxynucleotides (CpG ODN)) significantly enhance CMI response to PRRSV vaccines. The response is characterized by proliferation, cytotoxicity, and IFNgamma secretion of peripheral blood mononuclear cells or T cells in response to recall PRRSV antigens in vitro. Two (i.e. CpG ODN and cholera toxin) significantly enhance PRRSV-specific antibody response after vaccination. Two (i.e. IL-2 and CpG ODN) significantly enhance protective efficacy of PRRSV vaccines in challenge models. Improvement of immune responses to PRRSV vaccines should focus in future studies on assessing more vaccine adjuvants for their efficiency in enhancing both CMI and antibody responses and on identifying PRRSV components and strategies that down-modulate pig immune responses in order to devise vaccine adjuvants that can regulate such strategies of the virus.

Susceptibility of various FMDV strains to urea

Resistance to urea in vitro at 37 degrees C varied for each FMDV strain analysed. The urea marker did not correlate with other markers such as resistance to acid, resistance to acidity or size of plaques under agar on BHK21/13 cells. The resistance to urea of subtypes A24 Cruzeiro, O1 Caseros and C3 Resende varied in accordance with their antigenic potency when administered to swine as a trivalent water-in-oil emulsion type vaccine.