[Immune protective effectiveness of seasonal influenza spilt vaccine against homologous and heterogonous subtypes of influenza virus in mice].

To investigate the seasonal influenza split vaccine's immune protective effectiveness against the homologous and heterogonous subtypes of influenza A virus challenge and the relationship between the protective effectiveness and hemagglutination inhibition (HI) antibody titer in mice. Two components of H1N1 and H3N2 in Chinese 2008-2009 seasonal influenza spilt vaccine, were derived from vaccine strain A/Brisbane/59/2007 (H1N1)-like virus and A/Brisbane/10/2007 (H3N2)-like virus respectively, and were used to immune BALB/c mice. Firstly, different doses of the vaccines were used to immunize mice and the HA immunization dosage that can induce the HI antibody titer of 40 in mice was identified; Secondly, H1N1 vaccine immunized mice were challenged with different doses of influenza virus mouse adaptation strains of A/Brisbane/59/2007 (H1N1)-like virus (MA) (referred to as A1 virus, well matched-strain in the homologous subtype) and A/Purto Rico/8/34 (H1N1) (referred to as PR8 virus, poor matched-strain in the homologous subtype) respectively, and H3N2 vaccine immunized mice were challenged with H1N1 influenza virus of A1 strain (Heterogonous subtype), body weight changes and survival rates were observed to explore the immune protective effectiveness of influenza split vaccine against the homologous and heterogonous subtypes of influenza A virus in mice. Results indicated that HI antibody titers were elevated as the HA protein immunization dosages increased from 0.15 microg, 0.5 microg, 1.5 microg, 5 microg to 15 microg in mice, and 1.5 microg HA of the seasonal influenza split vaccine could induced HI antibody titer of 40 in mice; 3LD50, 10LD50, 30LD50, 100LD50, 300LD50,1000LD50 and 3000LD50 of influenza virus strain A1 were used to challenge the H1N1 immunization mice, 1.5 microg HA of H1N1 vaccine could 100% protect mice against challenge with 1000LD50 of matched and homologous subtype of influenza virus strains A1, mice immunized with 15 microg HA of H1N1 vaccine even could 100% protect mice against challenge with 3000LD50 of influenza virus strains A1; but mice immunized with both the 1.5 microg and 15 microg HA of H1N1 vaccine were all sacrificed when challenged with 3LD50 of the mismatched and homologous subtype of influenza virus strain PR8, and mice immunized with the high dosage of 15 microg HA of H3N2 vaccine also were all sacrificed when challenged with 3LD50 of the heterogonous subtype of influenza virus strain A1. These results suggest that 1.5 microg HA of seasonal influenza split vaccine could induced HI antibody titer of 40 after one dose in mice, this dosage of HA can effectively protect mice against matched homologous subtype of influenza virus strain, but hardly to protect mice against mismatched homologous or heterogonous subtype of influenza virus strain. These results provide materials for the establishment of influenza vaccine evaluation system based on seasonal influenza vaccine.