Analisis Dinamika Genetik Receptor Binding Site Hemaglutinin Virus Avian Influenza H5N1 Isolat Bali

R.Aj. SRI WULANDARI,dr, Prof. drh. Widya Asmara, SU, PhD

2011 | Tesis | S2 Ilmu Kedokteran Tropis

Batasan hospes virus influenza sebagian ditentukan oleh spesifitas pengikatan reseptor dari protein hemaglutinin. Hemaglutinin virus avian influenza H5N1 berevolusi pesat lewat antigenic shift dan antigenic drift. Strain dengan mutasi pada hemaglutinin dapat muncul dengan potensi perubahan kecenderungan pengikatan reseptor dari tipe avian ke manusia dan menimbulkan pandemi. Virus avian influenza H5N1 telah menyebar luas di Bali. Transmisi virus lewat perdagangan unggas dari Pulau Jawa diduga ikut berperan. Dekatnya interaksi antara manusia, ayam, bebek, dan babi di Bali dapat menyebabkan seleksi virus HPAI H5N1 yang mampu beradaptasi pada berbagai hospes dan mengurangi batasan transmisi dari virus ini. Tujuan penelitian ini adalah untuk menganalisis dinamika evolusi dari receptor binding site hemaglutinin dari 2 isolat virus avian influenza H5N1 asal ayam kampung dari Klungkung, Bali dan memprediksi risiko potensialnya bagi manusia. Jalan penelitian ini terdiri dari isolasi RNA, amplifikasi sekuen receptor binding site dengan Reverse Trancriptase Polymerase Chain Reaction (RT-PCR), elektroforesis, dan sequencing. Sekuen receptor binding site virus avian influenza H5N1 isolat Klungkung, Bali dianalisa menggunakan perbandingan lewat multiple alignment dengan isolat Indonesia lainnya dari berbagai hospes dan pembuatan pohon filogenetik. Dua isolat virus avian influenza H5N1 asal Klungkung, Bali masih menunjukkan kecenderungan untuk mengenal reseptor avian. Namun, dua substitusi S137A dan K193R diprediksi dapat meningkatkan pengenalan terhadap reseptor α-2,6. Pada akhirnya, dari hasil ini kami menyimpulkan adanya langkah adaptasi virus avian terhadap manusia.

Influenza virus host range restriction is partly determined by the receptorbinding specificity of the HA protein. Hemagglutinin of the avian influenza virus H5N1 evolves rapidly through antigenic shift and antigenic drift. Strains with mutated hemagglutinin may emerge, potentially changing the receptor binding preference from avian to human-type and causing pandemic. Avian influenza virus H5N1 was widely spread in Bali. Virus transmissions via poultry movement from Java Island were considered to play role. Close interaction between human, chickens, ducks and pigs in Bali could select HPAI H5N1 viruses that well adapted to multiple host and reduced interspecies transmission barrier of those viruses. The aim of this study is to analyze hemagglutinin receptor binding site dynamic evolution of two avian influenza viruses H5N1 from Klungkung, Bali isolated in 2009 and predict their potential risks to human. Chronological steps of this study consist of RNA isolation, amplification of receptor binding site sequence by Reverse Transcriptase Polymerase Chain Reaction (RT-PCR), electrophoresis, and sequencing. Receptor binding site sequence of avian influenza virus H5N1 isolates from Klungkung, Bali were analyzed using multiple alignment comparison with another Indonesian isolates from various hosts and phylogenetic tree construction. Two avian influenza virus H5N1 isolates from Klungkung, Bali showed recognition to avian receptor. However, two substitution sites, S137A and K193R were predicted to enhance α-2,6-linked receptor recognition. Finally, we conclude this finding could represent adaptation step from avian viruses to human.

Kata Kunci : Receptor binding site, virus avian influenza, subtipe H5N1, Bali