99 Jurnal Veteriner September 2008 Vol. 9 No. 3 : 99-106 ISSN : 1411 - 8327 Filogenetik dan Struktur Antigenik Virus Avian Influenza Subtipe H5N1 Isolat Unggas Air (PHYLOGENETIC AND ANTIGENIC STRUCTURE OF AVIAN INFLUENZA VIRUS OF H5N1 SUBTYPE ISOLATED FROM WATERFOWLS) R Susanti 1 , Retno Damajanti Soejoedono 2 , I Gusti Ngurah Kade Mahardika 3 , I Wayan Teguh Wibawan 2 , Maggy Thenawidjaja Suhartono 4 1 Jurusan Biologi FMIPA Universitas Negeri Semarang (UNNES) Gedung D6 Lt 1. Kampus Sekaran Jl. Raya Sekaran, Gunungpati, Semarang. Telepon: (024) 8508033; E-mail: rsant_ti@yahoo.com 2 Departemen Ilmu Penyakit Hewan dan Kesmavet FKH IPB, Jl. Agatis Kampus IPB Dramaga , Bogor 3 Laboratorium Virologi; Laboratorium Biomedik dan Biologi Molekuler Hewan FKH Universitas Udayana, Jl.Raya Sesetan Gang Markisa No. 6 Denpasar, Bali 4 Fakultas Tekonologi Pertanian IPB, Jl. Kamper Kampus IPB Dramaga, Bogor ABSTRACT A study was carried (1) to analyze the phylogenetic relationship of fragment hemaglutinin (HA) gene of avian influenza viruses (AIV) subtype H5N1 isolated from apparently healthy backyard waterfowls in West Java with representative of animal and human isolates from Indonesia and some countries in Asia; (2) to find out cross-reactivity of those viruses with a standard Indonesian strain. Nucleotide sequences of HA gene of AIV H5N1 from backyard waterfowls along with other H5N1 isolates of Indonesian and Asian origin were aligned using with ClustalW of MEGA 3.1 program. Estimation of genetic distance and the construction phylogenetic tree were conducted by Neighbor Joining method and calculation of distance matrix using Kimura 2-parameter. Antigenic analysis was conducted using hemagglutination inhibition (HI) test. Result of phylogenetic analysis indicated that all viruses from backyard waterfowls form three distinct sublineages. One lineage was located in Indonesia cluster and two lineages in Asia cluster. In the phylogenetic analysis, it was concluded that multiple introductions of AIV H5N1 to Indonesia have occurred. Six AI H5N1 viruses from backyard waterfowls (IPB1-RS to IPB6-RS) appeared to be different ancestors those isolated previously in Indonesia. Cross-antigenic analysis showed that nine viruses isolates used in this study were antigenically different to Legok 2003 chicken strain of AIV H5N1. The HI titer of anti- Legok 2003 antibody with all newly isolated viruses is up to 6 log lower then the HI titer using homolog strain. Key word: phylogenetic, antigenic, avian influenza viruses H5N1, waterfowls PENDAHULUAN Virus Avian Influenza (VAI) subtipe H5N1 dari berbagai negara, secara filogenetik terpisah menjadi 2 clade. Clade 1 adalah virus yang diisolasi pada unggas dan manusia di Kamboja, Thailand, Vietnam, Laos, Korea Selatan, dan Jepang tahun 2003-2004. Clade 2 terbagi menjadi 3 subclade. Subclade 1 adalah virus dari Indonesia tahun 2004-2006 dan isolat Hongkong tahun 2003. Subclade 2 adalah isolat virus dari Rusia, Turki, dan Timur Tengah tahun 2005-2006. Subclade 3 adalah isolat dari Laos, Thailand, Kamboja, dan Vietnam tahun 2005-2006 (WHO, 2005; Webster dan Govorkova, 2006). Virus-virus dalam clade dan subclade terpisah mempunyai perbedaan struktur antigenik, sehingga setiap clade atau subclade memerlukan vaksin yang berbeda. Studi pada feret menunjukkan bahwa vaksin terhadap satu clade tidak protektif terhadap clade lainnya. Sejalan dengan temuan itu, virus Indonesia juga dilaporkan tidak bereaksi dengan antibodi terhadap virus Vietnam dan sebaliknya virus Vietnam tidak bereaksi dengan antibodi terhadap virus Indonesia (Smith et al., 2006a). Di samping struktur antigenik, antar clade dan