Induction of adult-like antibody, Th1, and CTL responses to measles hemagglutinin by early life murine immunization with an attenuated vaccinia-derived NYVAC(K1L) viral vector

Although initially developed in adult animals, novel viral vectors expressi ng recombinant measles antigens must eventually prove their success in the early life setting, where the efficacy of the currently used live-attenuate d measles virus vaccine is limited. The immunological requirements for vacc ine candidates include the generation of protective antibody responses as w ell as the induction of Th1 and cytotoxic T lymphocytes (CTL) responses, wh ich is challenging in the neonatal setting. Here, we report that young BALB /c mice immunized with a single dose of a vaccinia-based NYVAC(K1L) vector generate adult-like antihemagglutinin (HA) antibody responses as well as ad ult-like Th1 and CTL responses. Despite this strong immunogenicity in early life, antibody responses (but not T-cell responses) to a single dose of NY VAC(K1L)-HA remained susceptible to inhibition by preexisting measles antib odies, calling for use of prime-boost strategies. NYVAC(K1L)-HA is the firs t attenuated live viral vector demonstrated as capable of inducing adult-li ke antibody, Th1, and CTL responses against measles in an early life murine immunization model, a capacity previously only reported for measles DNA va ccines. (C) 2001 Academic Press.