ANTIBODY-RESPONSES IN VOLUNTEERS INDUCED BY NASAL INFLUENZA VACCINE COMBINED WITH ESCHERICHIA-COLI HEAT-LABILE ENTEROTOXIN-B SUBUNIT CONTAINING A TRACE AMOUNT OF THE HOLOTOXIN

Evaluation of the efficacy of nasal influenza vaccine combined with Es cherichia coli heat-labile enterotoxin B subunit (LTB) containing a tr ace amount of the holotoxin (LT) in inducing antibody responses among volunteers, which was conducted during the winter season of 1993-1994, is reported. A trivalent inactivated vaccine, composed of A/Yamagata/ 32/89 (H1N1), A/Kitakyusyu/159/93 (H3N2) and B/Bangkok/163/90 influenz a virus strains, was used alone or together with the adjuvant, recombi nant LTB supplemented with 0.5% recombinant LT (LTB). The volunteers were divided into two groups: 73 volunteers (mean age 35.0 +/- 12.0 ye ars) inoculated intranasally (in.) with LTB-combined vaccine and 49 v olunteers (37.9 +/- 11.3) inoculated in. with the vaccine alone, Vacci nation was done twice 4 weeks apart. Salivary secretory IgA and serum hemagglutination-inhibiting (HI) antibodies were measured before and 8 weeks after the primary vaccination. For the sake of convenience, mor e than a 1.4-fold rise in IgA antibody response (units of specific IgA antibody per mu g of total IgA) and a fourfold or enter rise in HI an tibody titer after vaccination were regarded as a positive antibody re sponse. Thirty-seven (50.3%) and 36 (49.3%) of the 73 vaccinees, respe ctively, given the nasal LTB-combined vaccine showed positive IgA and HI antibody responses to one or move of the three vaccine strains. In comparison, positive antibody responses in the group given vaccine al one were 32.7% for IgA and 30.6% for HI antibody. There was a signific ant difference between these two groups. These results suggest that th e nasal LTB-combined vaccine could enhance the production of higher l evels not only of serum HI antibody but IgA antibodies in the respirat ory tract than do the nasal vaccine alone.