The importance of surveillance of avian and swine influenza

Transcription

1 FA/IE International Scientific Conference on Avian Influenza and Wild Birds May 30-31, 2006, Rome The importance of surveillance of avian and swine influenza HIRSHI KIDA and YSHIHIR SAKDA Hokkaido University Graduate School of Veterinary Medicine Research Center for Zoonosis Control Sapporo, Japan Points of Discussion 1. Ecology and evolution of influenza viruses -- Mechanism of antigenic variation of IV -2. Mechanism of the emergence of pandemic strains in humans and HPAIV in chickens 3. Do the H5N1 HPAIV strains perpetuate in the lakes where migratory birds nest? 4. Is the H5N1 HPAIV alone as a candidate of pandemic strain? 5. What is the best measure for the control of bird flu? Host animals and HA and NA subtypes of influenza A virus 1

2 Duck influenza Each of the known subtypes (H1-15, N1-9) of influenza A virus has been isolated from ducks. In ducks, viruses replicate in the colon, being shed with feces. Water-borne fecal-oral transmission Inapparent infection, apathogenic strains Carry and provide viruses during migration and overwintering. Migratory duck is the natural host of influenza A viruses. Amino acid substitutions on the HAs of viruses isolated from humans are confind to 5 antigenic sites, indicating that viruses are circulating in the presence of antibody selection pressure. Extensive antigenic variation H3 HAs Amino acid substitutions on the HAs of 7 viruses isolated from ducks are scattered throughout the HA molecule and not confined to the antigenic sites, indicating that viruses are circulating in the absence of antibody selection pressure. Evolutionally stasis Why are viral genomes highly conserved in ducks? HAs of H3N2 viruses isolated from pigs in southern China Viruses replicating in intestine are not under the antibody selection pressure. 40 to 50 % of population of migratory ducks are juvenile birds that hatched in summer. Preserved in frozen lake water in winter. Closely related with those of A/Hong Kong/68 (H3N2) and H3 viruses isolated from migratory ducks Amino acid sequences at the receptor-binding site on the HA indicate either specificity to human or avian viruses 2

3 Amino acid sequences at the receptor-binding site of the H3 HA of swine viruses compared to those of human and avian strains Virus HA Receptor NeuAc Gal GlcNAc Amino Acid sequence Virus Aichi/68 and Human Viruses Leu - Ser - Ser Avian Viruses Gln - Ser - Gly Sw/Taiwan/82 Gln - Ser - Gly Sw/China/78 Leu - Ser - Ser AcHN Leu Ser - Ser AcHN Gln Ser - Gly H H CH 2 H H H H CH 2 H CCH α α2, 6 CCH H H CHH CH 2 H H CH 2 H H CH 2 H H NHAc H H α2, 2, 3 Amino acid residues 226 and 228 of the HA1 subunit of H3 HA determine the receptor specificity. NHAc Influenza viruses isolated from domestic ducks in southern China HAs of influenza viruses isolated from domestic ducks in southern China antigenically and genetically closely related with those of viruses isolated from pigs in southern China, from migratory ducks, and A/Hong Kong/68. Each of the viruses was isolated on the Pacific flyway of migratory ducks. Migratory duck domestic duck pig humans Ito et al, (1998) J Virol 3

4 Siberia Migratory duck The role of pigs in the emergence of pandemic strains A/duck/xx (H3 H3N? N?) Domestic duck Pig Pigs are susceptible to avian influenza viruses of each of the HA subtypes. Southern China Genetic Virus shedding reassortment A/Asian/67 (H2 H2N2 N2) A/Hong Kong/68 (H3N2 H3N2) Hong Kong Genetic reassortants were generated in the cells lining upper respiratory tract of pig upon concurrent infection with mammalian and avian strains. Preparing for pandemic influenza H1 to H16 and N1 to N9 subtypes of influenza A viruses perpetuate in lakes where ducks nest in nature H2N2 and 1968 H3N2 viruses are reassortants between AIV and the preceding human strains. Pigs are susceptible to AIVs and mammalian IVs, generating reassortants. Avian viruses of any subtype can contribute genes for reassortants : None of the 16 HA and 9 NA subtypes can be ruled out as potential candidates for future pandemics. Global surveillance of swine flu as well as avian flu 4

5 Isolation ofinfluenza viruses from w ater sam ples oflakes in Alaska in Location Lake H ood/spenard Lake C heney Potter M arsh W estchester Lagoon Lake Hanger Fairbanks B ig M into Lake M allard Lake H eart Lake C anvasback Lake C orville Delta Total N o.of sam ples w ith virus/ totalno.of sam ples tested sum m er sum m er sum m er autum n 1/4 0/2 0/3 0/3 0/4 0/1 0/4 0/5 0/10 7/13 3/21 1/2 0/5 0/17 0/5 0/3 0/1 2/23 0/28 7/30 3/21 Kobyaysky(820) 40 Ilands(1321) H4N6 H4N9 Kenkeme(32) H11N1 H11N6 Magadan(295) H11N9 Kharyyalah(146) Buotama(51) White Lake(1136) Yakutsk(232) H3N8 Irkutsk(290) H3N8 Ptropavlovsk- Elavga(66) H13N6 Kamchatsky(58) Khabarovsk(23) Lake Kanicheva(95) Malyshevo(90) Wakkanai (958) H1N1 H3N8 H5N H5N H6N H6N7 Taiwan 1999 H8N1 H1N1 H8N3 H4N5 H9N2 H4N6 H11N9 H7N7 Acquisition of pathogenicity of avian influenza virus in chicken APAIV LPAIV 6~9 Months HPAIV (H5 or H7) 5

6 Amino acid sequences at the cleavage sites of influenza A virus HAs Subtype Amino acid sequences H1 H2 H3 H4 H5 H5 H6 H7 H7 H8 H9 H10 H11 H12 H13 H14 H15 Strains Dk/Alberta/35/76(H1N1) b Mal/MT/Y61(H2N2) b Dk/Menphis/928/74(H3N8) b Dk/Czechoslovakia/56(H4N6) b Ck/Scotland/59(H5N1) b Ty/MN/3/92(H5N2) a Shw/Australia/1/72(H6N5) b FPV/Rostock/34(H7N1) b Mal/Alberta/195/89(H7N3) a Ty/ntario/6118/68(H8N4) b Ty/Wisconsin/66(H9N2) b Ck/Germany/N/49(H10N7) b Dk/England/56(H11N6) b Dk/Alberta/60/76(H12N5) b Gl/Maryland/704/77(H13N6) b Mal/Gurjev/263/82(H14N5) b Shw/Australia/2576/79(H15N9) b Senne et al, 1996 a, Kovacova et al, 2002 b IQSR GLF IESR GLF KQTR GLF KASR GLF RKKR GLF RETR GLF IETR GLF KKRKKR GLF KKTR GLF VEPR GLF RSSR GLF VQGR GLF IASR GLF VQDR GLF ISNR GLF KQAK GLF IRTR GLF Pathogenicity of influenza virus for chicken Cleavability of the HA protein into HA1 and HA2 is crucial and consecutive alignment of basic amino acids (R and K) at the cleavage site is related to the pathogenicity for chicken. Cleavage activation of the HA by ubiquitous protease penetration by fusion into host cell extensive replication systemic infection HPAI outbreaks in Japan, 2004 Pathogenicity of A/ck/Yamaguchi/7/04 (H5N1) for birds and mammals Yamaguchi Kyoto 1. Ck/Yamaguchi/7/04 (H5N1) is highly pathogenic for birds. hita 2. Ck/Yamaguchi/7/04 (H5N1) is not highly pathogenic for mice with low mortality and does not infect pigs Yamaguchi Pref. ita Pref. Kyoto Pref. Kyoto Pref. 1/12/04 2/17/04 2/28/04 3/ 5/04 34,000 layers 13 pet chickens 225,325 layers 15,000 broilers H5N1 H5N1 H5N1 H5N1 HPAI HPAI HPAI HPAI 6

7 HPAI viruses in feral water birds, 2005 China: Whooper swans, Bar-headed geese, etc Hong Kong: Peregrine falcon, Grey heron, etc Croatia: Mute swans Mongolia: Whooper swans, Bar-headed geese Romania: Swan, Heron Kazakhustan: : Geese, ducks Phylogenetic tree of HA genes of HPAI viruses isolated from water birds Dk/China/E319.2/03 Ph/ST/44/04 Dk/HN/5806/03 Dk/HN/114/05 Ck/ST/810/05 Ck/Indonesia/BL/03 Dk/Indonesia/MS/04 Ck/HK/YU324/03 Dk/YN/6255/03 Ck/YN/493/05 Egret/HK/757.3/03 HK/212/03 BHG/HK/12.1/03 GH/HK/861.1/03 Dk/HK/821/02 Ck/HK/FY157/03 Ck/Thailand/1/04 Thailand/1(Kan-1)/04 Dk/Viet Nam/11/04 Viet Nam/1194/04 Gs/ST/1621/05 Pf/HK/D0028L/04 Ck/ST/4231/03 Ck/Yamaguchi/7/04 Whooper Swan/Mongolia/3/05 Whooper Swan/Mongolia/4/05 Whooper Swan/Mongolia/6/05 BH gull/qh/3/05 Bar-headed Gs/QH/12/05 Bar-headed Gs/QH/5/05 GBH gull/qh/2/05 Bar-headed Gs/Mongolia/1/05 Env/HK/437.10/99 Gs/GD/1/96 HK/156/97 Ck/HK/YU562/01 Chicken Fatality 100% (8weeks) IVPI index = 2.95 Duck Fatality 30% (4weeks) Neurological signs Duck Fatality 100% (3days) Neurological signs Mouse 50% (4weeks) Fatality Pig Infected without showing (4weeks) clinical signs 7

8 Nucleotide sequence identity (%) between the HA genes of H5 influenza viruses isolated from birds and humans in different areas in the world Ck/Nigeria/641/06 (H5N1) Mute swan/croatia/1/05 (H5N1) Ck/Nigeria/641/06 (H5N1) Mute swan/croatia/1/05 (H5N1) goose turkey Whooper swan/mongolia/3/05 (H5N1) Bar-headed Gs/QH/5/05 (H5N1) Ck/Guangdong/174/04 (H5N1) Ck/Yamaguchi/7/04 (H5N1) Thailand/2(SP-33)/04 (H5N1) Viet Nam/1194/04 (H5N1) Dk/Yokohama/aq-10/03 (H5N1) HK/156/97 (H5N1) duck 6-9Months quail Low Pathogenic chickens AIV HPAIV HK/483/97 (H5N1) Dk/Hok/69/00 (H5N3) Dk/Hok/101/04 (H5N3) Swan/Hok/67/96 (H5N3) pig Human virus Dk/HK/698/79 (H5N3) Dk/Miyagi/54/76 (H5N3) Tern/S.A/61 (H5N3) Ck/Ibaraki/1/05 (H5N2) Dk/Hok/84/02 (H5N3) Ck/Gtml/ /00 (H5N2) Ck/Mexico/232/94 (H5N2) Dk/Penn/10218/84 (H5N2) Ty/ntario/7732/66 (H5N9) HVAIV Isolated in our lab Apathogenic AIV X Pandemic Genetic virus Reassortant virus HPAI virus and human pandemic virus strains Present status of the library of vaccine strain candidates Influenza viruses of 49 combinations of the HA and NA subtypes have been isolated from fecal samples of ducks in Alaska, Siberia, Mongolia, Taiwan, China, and Japan (black black). So far, 76 other combinations have been generated by genetic reassortment procedure in the laboratory (red red).. Thus, avian influenza viruses of 123 combinations of HA and NA subtypes have been stocked as vaccine strain candidates. Their pathogenicity, antigenicity, genetic information and yield in chicken embryo have been analyzed, and being databased. Points of Discussion 1. Ecology and evolution of influenza viruses -- Mechanism of antigenic variation of IV Mechanism of the emergence of pandemic strains in humans and HPAIV in chickens 3. Do the H5N1 HPAIV strains perpetuate in the lakes where migratory birds nest? 4. Is the H5N1 HPAIV alone as a candidate of pandemic strain? 5. What is the best measure for the control of bird flu? 8