OBJECTIVESTo evaluate if the humoral immune response of hepatitis B DNA vaccine pVAX1-S2S could be enhanced by Talpha1 and/or IFNa expression plasmid co-inoculated.

METHODSThe following mammalian expression recombinant plasmids were constructed: the plasmid pVAX1-S2S expressing hepatitis B surface antigen S2S, the plasmid pVAX1-T/I co-expressing thymosin a and IFNalpha, the plasmid pVAX1-I/S2S co-expressing IFNalpha and S2S. These plasmids were inoculated intramuscularly into several BALB/c mice groups in different combinations. In the co-immunization group 1 (pVAX1-I/S2S), each mouse was inoculated with 100 microg of pVAX1-I/S2S; in the co-immunization group 2 (pVAX1-S2S) each mouse was co-inoculated with pVAX1-S2S and 50 microg of pVAX1-TI; in the control group each mouse was inoculated with 100 microg of pVAX1-S2S. All the immunizations were boosted at 2 and 4 week intervals; then the serum samples were collected to detect the anti-HBs and anti-preS2 strengths.

RESULTS3, 5 and 8 weeks after the first inoculation, the positive rates of anti-HBs were 12.5%, 12.5%, 62.5% respectively in the co-immunization group 1 and 25%, 50%, 50% in the co-immunization group 2, while those in the control group were 0, 25%, 37.5%. The titers of anti-preS2 in co-immunization group 2 was 5 times higher than those in the other two groups.

CONCLUSIONThe data shows that Talpha1 and/or IFNalpha expression plasmid co-inoculated with pVAX1-S2S might act as an adjuvant to enhance the humoral immune response induced by pVAX1-S2S.