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Journal of Virology, December 2000, p. 11181-11190, Vol. 74, No. 23
Department of Microbiology and Molecular
Genetics, New England Regional Primate Research Center, Harvard
Medical School, Southborough, Massachusetts 01772-9102
Received 22 May 2000/Accepted 1 September 2000
Stocks of simian immunodeficiency virus (SIV) from the supernatants
of infected cell cultures were used to examine the sensitivity of
envelope glycoprotein gp120 to enzymatic deglycosylation
and the effects of enzyme treatment on infectivity. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis and Western blot analysis revealed little or no change in the mobility of
virion-associated gp120 after digestion with high concentrations
of N-glycosidase F, endoglycosidase F, endoglycosidase H,
and endo-
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Resistance of Native, Oligomeric Envelope on Simian
Immunodeficiency Virus to Digestion by Glycosidases
-galactosidase. Soluble gp120, which was not pelletable
after the enzymatic reaction, was sensitive to digestion by the same
enzymes within the same reaction mix and was only slightly less
sensitive than gp120 that had been completely denatured by boiling
in the presence of SDS and
-mercaptoethanol. Digestion by three of
the seven glycosidases tested significantly changed the infectivity
titer compared to that of mock-treated virus. Digestion by
endo-
-galactosidase increased infectivity titers by about 2.5-fold,
and neuraminidase from Newcastle disease virus typically increased
infectivity titers by 8-fold. Most or all of the increase in
infectivity titer resulting from treatment with neuraminidase could be
accounted for by effects on the virus, not the cells; SIV produced in
the presence of the sialic acid analog
2,3-dehydro-2-deoxy-N-acetylneuraminic acid also exhibited
increased infectivity, and the effects could not be duplicated by
neuraminidase treatment of cells. Digestion with mannosidase reduced
infectivity by fivefold. Our results indicate that carbohydrates on
native oligomeric gp120 as it exists on the surface of virus particles
are largely occluded and are refractory to digestion by glycosidases.
Furthermore, the sialic acid residues at the ends of carbohydrate side
chains significantly reduce the inherent infectivity of SIV.
*
Corresponding author. Mailing address: Department of
Microbiology and Molecular Genetics, New England Regional Primate
Research Center, Harvard Medical School, 1 Pine Hill Dr., Southborough, MA 01772-9102. Phone: (508) 624-8042. Fax: (508) 624-8190. E-mail: ronald_desrosiers{at}hms.harvard.edu.
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