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Journal of Virology, April 2001, p. 3568-3580, Vol. 75, No. 8
0022-538X/01/$04.00+0   DOI: 10.1128/JVI.75.8.3568-3580.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Differential CD4/CCR5 Utilization, gp120 Conformation, and Neutralization Sensitivity between Envelopes from a Microglia-Adapted Human Immunodeficiency Virus Type 1 and Its Parental Isolate

Julio Martín,1 Celia C. LaBranche,2 and Francisco González-Scarano1,3,*

Departments of Neurology1 and Microbiology,3 University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, and Department of Surgery, Duke University Medical Center, Durham, North Carolina 277102

Received 25 October 2000/Accepted 10 January 2001

Human immunodeficiency virus type 1 (HIV-1) infects and induces syncytium formation in microglial cells from the central nervous system (CNS). A primary isolate (HIV-1BORI) was sequentially passaged in cultured microglia, and the isolate recovered (HIV-1BORI-15) showed high levels of fusion and replicated more efficiently in microglia (J. M. Strizki, A. V. Albright, H. Sheng, M. O'Connor, L. Perrin, and F. González-Scarano, J. Virol. 70:7654-7662, 1996). The parent and adapted viruses used CCR5 as coreceptor. Recombinant viruses demonstrated that the syncytium-inducing phenotype was associated with four amino acid differences in the V1/V2 region of the viral gp120 (J. T. C. Shieh, J. Martin, G. Baltuch, M. H. Malim, and F. González-Scarano, J. Virol. 74:693-701, 2000). We produced luciferase-reporter, env-pseudotyped viruses using plasmids containing env sequences from HIV-1BORI, HIV-1BORI-15, and the V1/V2 region of HIV-1BORI-15 in the context of HIV-1BORI env (named rBORI, rB15, and rV1V2, respectively). The pseudotypes were used to infect cells expressing various amounts of CD4 and CCR5 on the surface. In contrast to the parent recombinant, the rB15 and rV1V2 pseudotypes retained their infectability in cells expressing low levels of CD4 independent of the levels of CCR5, and they infected cells expressing CD4 with a chimeric coreceptor containing the third extracellular loop of CCR2b in the context of CCR5 or a CCR5 Delta 4 amino-terminal deletion mutant. The VH-rB15 and VH-rV1V2 recombinant viruses were more sensitive to neutralization by a panel of HIV-positive sera than was VH-rBORI. Interestingly, the CD4-induced 17b epitope on gp120 was more accessible in the rB15 and rV1V2 pseudotypes than in rBORI, even before CD4 binding, and concomitantly, the rB15 and rV1V2 pseudotypes were more sensitive to neutralization with the human 17b monoclonal antibody. Adaptation to growth in microglia---cells that have reduced expression of CD4 in comparison with other cell types---appears to be associated with changes in gp120 that modify its ability to utilize CD4 and CCR5. Changes in the availability of the 17b epitope indicate that these affect conformation. These results imply that the process of adaptation to certain tissue types such as the CNS directly affects the interaction of HIV-1 envelope glycoproteins with cell surface components and with humoral immune responses.

* Corresponding author. Mailing address: Department of Neurology, University of Pennsylvania, Clinical Research Building 255, 415 Curie Blvd., Philadelphia, PA 19104-6146. Phone: (215) 662-3360. Fax: (215) 662-3362. E-mail: scarano{at}mail.med.upenn.edu.

Journal of Virology, April 2001, p. 3568-3580, Vol. 75, No. 8
0022-538X/01/$04.00+0   DOI: 10.1128/JVI.75.8.3568-3580.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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