Abstract
Influenza types A virus are envelope viruses, belonging to the Orthomyxoviridae family. The viral envelopes consist mainly four structure proteins (HA, NA, M1, and M2) and the plasma membrane-derived lipid biolayers. HA is the major spike protein on the viral surface and is involved in host cell binding, fusion and host cell tropism, and is the primary target antigen to elicit protective immune responses. In this study, recombinant HA proteins of the influenza A/WSN/33(H1N1) and A/Tailand/1(KAN-1)/2004(H5N1) strains were cloned and produced using baculovirus-insect cell expression system. Baculovirus-expressed H1HA and H5HA proteins were N-linked glycosylated, typrsin-sensitive for protease cleavage, and functionally agglutinated the red blood cells. Full-length and ectodomain H1HA and H5HA were effectively expressed in insect cells but not led to predominant secretion to culture medium. Finally, using immobilized metal ion affinity chromatography (IMAC) column to purify the recombinant HA ectodomain. Recombinant virus-like particles were obtained by baculovirus expression of M1 alone, as explained by sucrose gradient and transmission electron microscopy. Fluorescent virus-like particles were further constructed by co-expression of M1 and the M2 fused with EGFP at N-terminus.