Baculovirus Replication: Uptake of Trichoplusia ni Nuclear Polyhedrosis Virus Particles by Insect Cells

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Abstract
The uptake of 2 forms of T. ni multiple nucleocapsid nuclear polyhedrosis virus by Spodoptera frugiperda cells in culture was evaluated. Subtle differences in the Mg2+ and Ca2+ requirements for the uptake of cell-released virus (CRV) and polyhedron-derived virus (PDV) exist; otherwise, both forms of the virus appeared similar in their mode of uptake. Entry occurs by fusion of the plasma membrane of the cell with the envelope surrounding the virus nucleocapsid at neutral pH. The receptor turnover for the virus probably occurs rapidly since saturation of receptor sites for the virus was not achieved. The binding and penetration of the virus, and the uncoating and transport of the viral genome to the nucleus is rapid. Uncoating occurs predominantly in the cytoplasm. The lower infectivity of PDV, compared with CRV, for cells in culture may happen because this form of the virus accumulates in cell vacuoles and is unable to proceed with infection.