CHALLENGE OF BALB C MICE WITH RESPIRATORY SYNCYTIAL VIRUS DOES NOT ENHANCE THE TH2 PATHWAY INDUCED AFTER IMMUNIZATION WITH A RECOMBINANT-G FUSION PROTEIN, BBG2NA, IN ALUMINUM HYDROXIDE/

The polypeptide of aa 130-230 of the G protein (G2Na) of respiratory s yncytial virus (RSV) was fused to BB, the albumin-binding region of st reptococcal G protein, producing BBG2Na, which induced protective immu ne responses in rodent models. Evaluation of the immune response in mi ce immunized with BBG2Na in the adjuvant alhydrogel revealed high amou nts of interleukin (IL)-5 and some IL-4 in splenocytes restimulated in vitro. This is compatible with a Th2 response. The activation of the Th2 pathway in such mice was further supported by the detection of IL- 5 and GaNa-specific IgE in vivo. Of interest, in contrast to immunizat ion with formalin-inactivated RSV, immunization of mice with BBG2Na fo llowed by intranasal RSV challenge did not lead to increased productio n of IL-5- or G2Na-specific IgE. However, IgG1- and IgG2a-specific ant ibodies were boosted. These results demonstrate that the Th2 pathway i s not enhanced by RSV challenge in BBG2Na-immunized mice.