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Antimicrobial Agents and Chemotherapy, March 2001, p. 664-672, Vol. 45, No. 3
Laboratory of Natural Products, Division of
Basic Sciences, National Cancer Institute-Frederick, Cancer
Research and Development Center, Frederick, Maryland 21702
Received 26 April 2000/Returned for modification 28 July
2000/Accepted 7 November 2000
Cyanovirin-N (CV-N), an 11-kDa protein originally isolated from the
cyanobacterium Nostoc ellipsosporum, potently inactivates diverse strains of human immunodeficiency virus type 1 (HIV-1), HIV-2,
simian immunodeficiency virus, and feline immunodeficiency virus. It
has been well established that the HIV surface envelope glycoprotein
gp120 is a molecular target of CV-N. We recently reported that CV-N
impaired the binding of virion-associated gp120 to cell-associated CD4
and that CV-N preferentially inhibited binding of the
glycosylation-dependent neutralizing monoclonal antibody 2G12 to gp120.
However, CV-N did not interfere with the interactions of soluble CD4
(sCD4) with either soluble gp120 (sgp120) or virion-associated gp120.
In the present study, we have evaluated the effects of CV-N on the
binding of sgp120 to cell-associated CD4 to clarify the experimental
basis of the previous binding results, and we further address the
detailed mechanism of action of CV-N. Here we present evidence that (i)
CV-N impairs both CD4-dependent and CD4-independent binding of sgp120
to the target cells, (ii) CV-N blocks the sCD4-induced binding of
sgp120 with cell-associated coreceptor CXCR4, and (iii) CV-N
dissociates bound sgp120 from target cells. The results illustrate that
the measured effects of CV-N on gp120-CD4 binding interactions depend
upon the type of CD4 (soluble or cell associated), but not upon the
type of gp120 (soluble or virion associated), employed in the
experimental protocol. In addition, this study reinforces that CV-N
acts uniquely to prevent essential interactions between the envelope
glycoprotein and target cell receptors and further supports the
potential broad utility of CV-N as a microbicide to prevent the
transmission of HIV and AIDS.
0066-4804/01/$04.00+0 DOI: 10.1128/AAC.45.3.664-672.2001
Cyanovirin-N, a Potent Human Immunodeficiency Virus-Inactivating
Protein, Blocks both CD4-Dependent and CD4-Independent Binding of
Soluble gp120 (sgp120) to Target Cells, Inhibits sCD4-Induced
Binding of sgp120 to Cell-Associated CXCR4, and Dissociates Bound
sgp120 from Target Cells
*
Corresponding author. Mailing address: Laboratory of
Natural Products, Division of Basic Sciences, National Cancer
Institute-Frederick, Cancer Research and Development Center, Bldg.
1052, Rm. 121, Frederick, MD 21702-1201. Phone: (301) 846 5391. Fax:
(301) 846 6177. E-mail: boyd{at}dtpax2.ncifcrf.gov.
Paper 67 in the NCI Laboratory of Drug Discovery Research and
Development series "HIV-Inhibitory Natural Products."
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