Semliki Forest virus multiplication in clones of Aedes albopictus cells

Abstract

Clones of A. albopictus cells (115) were examined for their response to infection with semliki Forest virus. Virus yield and cytopathology showed a bimodal distribution. More than 68% of the clones gave low yields of virus (8 .times. 106-2 .times. 108 PFU[plaque-forming units]/ml) with no discernable cytopathology and 30% gave high yields of virus (1-8 .times. 109 PFU/ml) and showed moderate to severe cytopathology. To determine the level at which restriction in virus growth occurs in the low-virus-producing clones, the nature and extent of several virus-directed events in selected low-virus-producing clones were compared with the same events in high-virus-producing clones. Specifically, virus-specified polypeptide synthesis, positive- and negative-strand RNA synthesis, adsorption, uncoating and transfection with virion 42S RNA was compared. Whereas events before negative-strand RNA synthesis occurred to the same extent in all clones examined, negative-strand RNA synthesis and all subsequent virus-specified events were markedly reduced in the low-virus-producing lines, compared with the high-virus-producing lines. Thus, the restriction in virus growth in the low-virus-producing line occurs at the level of synthesis of negative-strand RNA. The consequence of this restriction in an early step in the virus multiplication cycle is discussed in terms of the survival of invertebrate cells after alphavirus infection.