H2N2 cold-adapted (ca) vaccine: H2N2 viruses caused the 1957 influenza pandemic and circulated in humans until 1968 when they were replaced by H3N2 viruses. Although H2 viruses have not circulated in humans since 1968, this subtype is maintained in avian reservoirs worldwide. An H2 vaccine is a high priority in preparing for a pandemic because H2 viruses have a proven capability for causing disease in humans and persons born after 1968 lack H2-specific immunity. Because the currently licensed live attenuated influenza vaccine utilized in the United States bears the internal protein genes of the influenza A/AnnArbor/6/60 (H2N2) ca virus, the A/AnnArbor/6/60 (H2N2) ca virus was a logical first choice for evaluation as an H2 vaccine candidate. However, this virus with the H2 HA and N2 NA had not been evaluated in seronegative people. An IND was submitted for a Phase I study to evaluate safety, level of replication, infectivity and immunogenicity of A/Ann Arbor/6/60 ca (H2N2) virus. Twenty-one subjects received the first dose and 18 received two doses of the vaccine. The vaccine was well-tolerated and the analysis of the data is in progress. H6N1 cold-adapted (ca) vaccine: Based on promising preclinical data in mice and ferrets, an IND was submitted for a Phase I study to evaluate safety, level of replication, infectivity and immunogenicity of an H6N1 ca vaccine based on A/teal/Hong Kong/W312/1997 (H6N1). Twenty-two participants received the first dose of the vaccine, and 18 received the second dose of vaccine 4 weeks later. The vaccine had a safety profile similar to that of other investigational LAIVs bearing avian hemagglutinin (HA) and neuraminidase (NA) genes. The vaccine was highly restricted in replication: two participants had virus detectable by rRT-PCR beyond day 1 after each dose. Antibody responses to the vaccine were also restricted: 43% of participants developed a serum antibody response as measured by any assay: 5% by hemagglutination-inhibition assay, 5% by microneutralization assay, 29% by ELISA for H6 HA-specific IgG and 24% by ELISA for H6 HA specific IgA after either 1 or 2 doses. Following the second dose, vaccine specific IgG and IgA secreting cells as measured by ELISPOT increased from a mean of 0.6 to 9.2/106 PBMCs and from 0.2 to 2.2/106 PBMCs, respectively. In conclusion, the H6N1 LAIV had a safety profile similar to that of LAIV bearing other HA and NA genes, but was highly restricted in replication in healthy seronegative adults. The H6N1 LAIV was also not as immunogenic as the seasonal LAIV. H2N3 cold-adapted (ca) vaccine: Based on promising preclinical data in mice and ferrets, an IND was submitted for a Phase I study to evaluate safety, level of replication, infectivity and immunogenicity of an H2N3 ca vaccine based on A/swine/MO/2006 (H2N3). Nineteen subjects received the first dose and 15 received two doses of the vaccine. The vaccine was well-tolerated and the analysis of the data is in progress. H7N7 cold-adapted (ca) vaccine: Based on promising preclinical data in mice and ferrets, an IND was submitted for a Phase I study to evaluate safety, level of replication, infectivity and immunogenicity of an H7N7 ca vaccine based on A/Netherlands/219/2003 (H7N7). Fifteen subjects received the first dose and 13 received two doses of the vaccine. The vaccine was well-tolerated and the analysis of the data is in progress. H7N3 cold-adapted (ca) vaccine: We had previously evaluated the safety, infectivity, and immunogenicity of two doses of the vaccine administered by nasal spray 5 weeks apart to normal healthy seronegative adult volunteers in an inpatient isolation unit. The subjects were followed for 2 months after 1 dose of vaccine or for 4 weeks after the second dose. The live attenuated H7N3 vaccine was well-tolerated but was highly restricted in replication in healthy seronegative adults. Despite the restricted replication, the vaccine was immunogenic, with serum IgA being the most sensitive measure of immunogenicity. A study to evaluate the safety, level of replication, infectivity and immunogenicity of a single dose of the H7N3 ca vaccine was undertaken. Twenty subjects received a single dose of the vaccine. The vaccine was well-tolerated and the analysis of the data is in progress.
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