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Journal of Virology, February 2001, p. 2010-2013, Vol. 75, No. 4
Department of Molecular and Structural
Biochemistry, North Carolina State University, Raleigh, North
Carolina 27695
Received 20 July 2000/Accepted 10 November 2000
It is widely held that the penetration of cells by alphaviruses is
dependent on exposure to the acid environment of an endosome. The
alphavirus Sindbis virus replicates in both vertebrate and invertebrate
cell cultures. We have found that exposure to an acid environment may
not be required for infection of cells of the insect host. In this
work, we investigated the effects of two agents (NH4Cl and
chloroquine), which raise the pH of intracellular compartments
(lysosomotropic weak bases) on the infection and replication of Sindbis
virus in cells of the insect host Aedes albopictus. The
results show that both of these agents increase the pH of endosomes, as
indicated by protection against diphtheria toxin intoxication.
NH4Cl blocked the production of infectious virus and
blocked virus RNA synthesis when added prior to infection. Chloroquine,
in contrast to its effect on vertebrate cells, had no inhibitory effect
on infectious virus production in mosquito cells even when added prior
to infection. Treatment with NH4Cl did not prevent the
penetration of virus RNA into the cell cytoplasm or translation of the
RNA to produce a precursor to virus nonstructural proteins. These data
suggest that while these two drugs raise the pH of endosomes, they do
not block insect cell penetration. These data support previous results
published by our laboratory suggesting that exposure to an acid
environment within the cell may not be an obligatory step in the
process of infection of cells by alphaviruses.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.4.2010-2013.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Exposure to Low pH Is Not Required for Penetration
of Mosquito Cells by Sindbis Virus
and
*
Corresponding author. Mailing address: Department of
Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695-7622. Phone: (919) 515-5765. Fax: (919) 515-2047. E-mail: Dennis_brown{at}ncsu.edu.
Present address: Genetic Therapy, Inc., Gaithersburg, MD 20878.
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