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J Virol, July 1998, p. 5399-5407, Vol. 72, No. 7
New England Regional Primate Research Center,
Harvard Medical School, Southborough, Massachusetts 01772-9102
Received 22 October 1997/Accepted 21 March 1998
Carbohydrates comprise about 50% of the mass of gp120, the
external envelope glycoprotein of simian immunodeficiency virus (SIV)
and human immunodeficiency virus. We identified 11 replication-competent derivatives of SIVmac239 lacking two, three,
four, or five potential sites for N-linked glycosylation. These sites
were located within and around variable regions 1 and 2 of the surface
envelope protein of the virus. Asn (AAT) of the canonical N-linked
glycosylation recognition sequence (Asn X Ser/Thr) was changed in each
case to the structurally similar Gln (CAG or CAA) such that two
nucleotide changes in the codon would be required for reversion.
Replication of one triple mutant (g456), however, was severely
impaired. A revertant of the g456 mutant was recovered from CEMx174
cells with a Met-to-Val compensatory substitution at position 144, 2 amino acids upstream of attachment site 5. Thus, a debilitating loss of
sites for N-linked glycosylation can be compensated for by amino acid
changes not involving the Asn-X-Ser/Thr consensus motif. These results
provide a framework to begin testing the hypothesis that carbohydrates
form a barrier that can limit the humoral immune responses to the
virus.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Identification of Replication-Competent Strains of
Simian Immunodeficiency Virus Lacking Multiple Attachment Sites for
N-Linked Carbohydrates in Variable Regions 1 and 2 of the
Surface Envelope Protein
*
Corresponding author. Mailing address: New England
Regional Primate Research Center, Harvard Medical School, One Pine Hill Dr., Box 9102, Southborough, MA 01772-9102. Phone: (508) 624-8042. Fax:
(508) 624-8190. E-mail:
rdesrosi{at}warren.med.harvard.edu.
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