Antibody responses to preS components after immunization of children with low doses of BioHepB

BioHepB is a recombinant, hepatitis B vaccine derived from a mammalian cell line and containing HBs as well as preS1 and preS2 antigens, in their glycosylated and non-glycosylated forms. The vaccine was administered intramuscularly to 18 children aged 5 months to 11 years at 0, 1 and 6 months. One hundred percent seroconversion and seroprotection rates were achieved after primary and secondary immunization with the 2.5 microg doses of BioHepB. Ten out of the 18 children (56%) responded with the appearance of anti-preS1 and/or anti-preS2 antibodies in circulation, when analyzed 1, 2, 6, 7 and 12 months after the initiation of vaccination. In comparison with the emergence of the anti-HBs response, early (month 2, after two injections) or late (month 7, after three injections) peak responses were noted for the kinetics of anti-preS1 and anti-preS2 production during the course of immunization, demonstrating that the anti-preS1 and anti-preS2 responses are differently regulated, compared with the anti-HBs response. At month 6, just prior to the final injection, BioHepB caused significantly higher anti-HBs responses (GMT) in preS1-reactive children than in children without preS1 antibodies (P<0.005). Moreover, a significantly higher, anti-HBs response in GMT was also noted for anti-preS2-reactive children compared with anti-preS2-negative children (P<0.05). These findings demonstrated that recognition of the preS epitopes contained in the experimental preS1/preS2/S vaccine is accompanied by a more rapid onset and pronounced antibody response to the S-gene-derived protein in healthy children.