PROTECTION OF MICE AGAINST LETHAL VIRAL-INFECTION BY SYNTHETIC PEPTIDES CORRESPONDING TO B-CELL AND T-CELL RECOGNITION SITES OF INFLUENZA-AHEMAGGLUTININ

Previously, we reported 12 synthetic T- and B-cell recognition regions representing surface areas of the hemagglutinin (HAJ of X31 influenza virus. In the present study, four of these peptides were examined in Balb/c mice for their ability to produce protective immunity against l ethal infection with a dose equivalent to 10 LD(50) of influenza virus . These peptides corresponded to the following sequences. 23-36 (HA1-1 ); 138-152 (HA1-3); 183-199 (HA1-6) and 1-11 (HA2-10). Each of the sel ected peptides, in their free form, evoked anti-peptide antibodies tha t cross-react with intact X31 virus. Two of the peptides, HA1-1 and HA 1-3, also elicited virus-specific delayed type hypersensitivity (DTH) responses. These two peptides, when injected into mice, not only faile d to protect the immunized mice against challenge with influenza virus , but in fact caused greater susceptibility to viral infection as comp ared to control animals that had been injected with saline. In contras t, peptides HA1-6 and HA2-10, which were unable to induce adequate vir us-specific DTH responses, conferred 42-46% and 54-73% protection, res pectively, compared to the control group that received only saline (P< 0.03 to P<0.01).