THERAPEUTIC EFFECT OF PRES2-CONTAINING VACCINE IN AN INFANT INFECTED WITH A VACCINE-ESCAPE VARIANT (THR(127)) OF HEPATITIS-B VIRUS

A male baby born to HBV-infected mother received HBIG and vaccine (S-g ene recombinant) according to the conventional protocol for prevention of vertical HBV transmission, but did not show active production of a nti-HBs. Additional two shots of S-gene recombinant vaccines at months 9 and 12 also failed to induce antibody despite increased doses. Then , at months 14, 15, and 19, a preS2-containing vaccine was injected, f ollowed by a prompt seroconversion to anti-HBs. Retrospective analyses of the baby's sera revealed that HBV DNA was repeatedly positive in t his baby's sera throughout the period of time when anti-HBs antibody r emained negative (months 6-15). Genetic analyses of HBV DNA from the m other and her baby showed that: (i) mother's HBV DNA was a mixture of adw and adr subtypes, whereas baby's HBV DNA consisted solely of adr s ubtype; and (ii) baby's HBV was a S-gene variant with its 127th codon coding for threonine instead of proline that is typical to wild type H BV/adr (Thr(127)). Thus, it seems in this case that the Thr(127) mutan t did escape conventional vaccines but could not escape preS2-induced immune response, and that eventually the preS2-containing vaccine work ed as a therapeutic vaccine. (C) 1997 Elsevier Science Ireland Ltd.