Adaptive mutations in a human immunodeficiency virus type 1 envelope protein with a truncated V3 loop restore function by improving interactions with CD4

Journal of Virology

Volumn 83, Issue 21, 2009, Pages 11005-11015

  Agrawal Gamse, Caroline ^a   Lee, Fang Hua ^a   Haggarty, Beth ^a   Jordan, Andrea P O ^a   Yanjie, Yi ^a   Lee, Benhur ^b   Collman, Ronald G ^a   Hoxie, James A ^a   Doms, Robert W ^a   Laakso, Meg M ^a  

^a UNIVERSITY OF PENNSYLVANIA   (United States)

^b UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

CD4 ANTIBODY; CHEMOKINE RECEPTOR CCR5 ANTAGONIST; ENVELOPE PROTEIN; MONOCLONAL ANTIBODY; UNCLASSIFIED DRUG; VIRUS ENVELOPE PROTEIN; VIRUS PROTEIN; VIRUS PROTEIN TA1;

ANIMAL CELL; ANTIBODY RESPONSE; ARTICLE; BINDING AFFINITY; BINDING SITE; CONTROLLED STUDY; GLYCOSYLATION; HUMAN; HUMAN CELL; HUMAN IMMUNODEFICIENCY VIRUS 1; MUTATIONAL ANALYSIS; NONHUMAN; PRIORITY JOURNAL; PROTEIN EXPRESSION; PROTEIN FUNCTION; PROTEIN INTERACTION; RECEPTOR BINDING; SENSITIVITY ANALYSIS;

ADAPTATION, BIOLOGICAL; ANIMALS; ANTI-HIV AGENTS; ANTIBODIES, MONOCLONAL; ANTIGENS, CD4; CELL LINE; CYCLOHEXANES; HIV ENVELOPE PROTEIN GP120; HIV-1; HUMANS; MUTATION; RECEPTORS, CCR5; RECOMBINANT PROTEINS; TRIAZOLES;

HUMAN IMMUNODEFICIENCY VIRUS 1;

EID: 70350330590     PISSN: 0022538X     EISSN: None     Source Type: Journal    
DOI: 10.1128/JVI.01238-09     Document Type: Article

References (71)

1. Alexander, W. A., B. Moss, and T. R. Fuerst. 1992. Regulated expression of foreign genes in vaccinia virus under the control of bacteriophage T7 RNA polymerase and the Escherichia coli lac repressor. J. Virol. 66:2934-2942.
2. Berger, E. A., P. M. Murphy, and J. M. Farber. 1999. Chemokine receptors as HIV-1 coreceptors: roles in viral entry, tropism, and disease. Annu. Rev. Immunol. 17:657-700.
3. Biscone, M. J., J. L. Miamidian, J. M. Muchiri, S. S. Baik, F. H. Lee, R. W. Doms, and J. D. Reeves. 2006. Functional impact of HIV coreceptor-binding site mutations. Virology 351:226-236.
4. Chen, B. K., K. Saksela, R. Andino, and D. Baltimore. 1994. Distinct modes of human immunodeficiency virus type 1 proviral latency revealed by super-infection of nonproductively infected cell lines with recombinant luciferase-encoding viruses. J. Virol. 68:654-660.
5. Chiou, S. H., E. O. Freed, A. T. Panganiban, and W. R. Kenealy. 1992. Studies on the role of the V3 loop in human immunodeficiency virus type 1 envelope glycoprotein function. AIDS Res. Hum. Retrovir. 8:1611-1618.
6. Choe, H., M. Farzan, Y. Sun, N. Sullivan, B. Rollins, P. D. Ponath, L. Wu, C. R. Mackay, G. LaRosa, W. Newman, N. Gerard, C. Gerard, and J. Sodroski. 1996. The beta-chemokine receptors CCR3 and CCR5 facilitate infection by primary HIV-1 isolates. Cell 85:1135-1148. (Pubitemid 26231178)
7. Cocchi, F., A. L. DeVico, A. Garzino-Demo, A. Cara, R. C. Gallo, and P. Lusso. 1996. The V3 domain of the HIV-1 gp120 envelope glycoprotein is critical for chemokine-mediated blockade of infection. Nat. Med. 2:1244-1247.
8. Connor, R. I., B. K. Chen, S. Choe, and N. R. Landau. 1995. Vpr is required for efficient replication of human immunodeficiency virus type-1 in mononuclear phagocytes. Virology 206:935-944.
9. Cormier, E. G., and T. Dragic. 2002. The crown and stem of the V3 loop play distinct roles in human immunodeficiency virus type 1 envelope glycoprotein interactions with the CCR5 coreceptor. J. Virol. 76:8953-8957.
10. Cormier, E. G., D. N. Tran, L. Yukhayeva, W. C. Olson, and T. Dragic. 2001. Mapping the determinants of the CCR5 amino-terminal sulfopeptide interaction with soluble human immunodeficiency virus type 1 gp120-CD4 complexes. J. Virol. 75:5541-5549.
11. De Wolf, F., E. Hogervorst, J. Goudsmit, E. M. Fenyo, H. Rubsamen-Waigmann, H. Holmes, B. Galvao-Castro, E. Karita, C. Wasi, S. D. Sempala, et al. 1994. Syncytium-inducing and non-syncytium-inducing capacity of human immunodeficiency virus type 1 subtypes other than B: phenotypic and genotypic characteristics. AIDS Res. Hum. Retrovir. 10:1387-1400.
12. Doms, R. W., and J. P. Moore. 2000. HIV-1 membrane fusion: targets of opportunity. J. Cell Biol. 151:F9-F14.
13. Doranz, B. J., Z. H. Lu, J. Rucker, T. Y. Zhang, M. Sharron, Y. H. Cen, Z. X. Wang, H. H. Guo, J. G. Du, M. A. Accavitti, R. W. Doms, and S. C. Peiper. 1997. Two distinct CCR5 domains can mediate coreceptor usage by human immunodeficiency virus type 1. J. Virol. 71:6305-6314.
14. Dragic, T. 2001. An overview of the determinants of CCR5 and CXCR4 coreceptor function. J. Gen. Virol. 82:1807-1814.
15. Dragic, T., A. Trkola, D. A. Thompson, E. G. Cormier, F. A. Kajumo, E. Maxwell, S. W. Lin, W. Ying, S. O. Smith, T. P. Sakmar, and J. P. Moore. 2000. A binding pocket for a small molecule inhibitor of HIV-1 entry within the transmembrane helices of CCR5. Proc. Natl. Acad. Sci. USA 97:5639-5644.
16. Edwards, T. G., T. L. Hoffman, F. Baribaud, S. Wyss, C. C. LaBranche, J. Romano, J. Adkinson, M. Sharron, J. A. Hoxie, and R. W. Doms. 2001. Relationships between CD4 independence, neutralization sensitivity, and exposure of a CD4-induced epitope in a human immunodeficiency virus type 1 envelope protein. J. Virol. 75:5230-5239.
17. Endres, M. J., P. R. Clapham, M. Marsh, M. Ahuja, J. D. Turner, A. McKnight, J. F. Thomas, B. Stoebenau-Haggarty, S. Choe, P. J. Vance, T. N. Wells, C. A. Power, S. S. Sutterwala, R. W. Doms, N. R. Landau, and J. A. Hoxie. 1996. CD4-independent infection by HIV-2 is mediated by fusin/CXCR4. Cell 87:745-756.
18. Farzan, M., N. Vasilieva, C. E. Schnitzler, S. Chung, J. Robinson, N. P. Gerard, C. Gerard, H. Choe, and J. Sodroski. 2000. A tyrosine-sulfated peptide based on the N terminus of CCR5 interacts with a CD4-enhanced epitope of the HIV-1 gp120 envelope glycoprotein and inhibits HIV-1 entry. J. Biol. Chem. 275:33516-33521.
19. Grimaila, R. J., B. A. Fuller, P. D. Rennert, M. B. Nelson, M. L. Hammarskjold, B. Potts, M. Murray, S. D. Putney, and G. Gray. 1992. Mutations in the principal neutralization determinant of human immunodeficiency virus type 1 affect syncytium formation, virus infectivity, growth kinetics, and neutralization. J. Virol. 66:1875-1883.
20. Hartley, O., P. J. Klasse, Q. J. Sattentau, and J. P. Moore. 2005. V3: HIV's switch-hitter. AIDS Res. Hum. Retrovir. 21:171-189.
21. Hu, Q., K. B. Napier, J. O. Trent, Z. Wang, S. Taylor, G. E. Griffin, S. C. Peiper, and R. J. Shattock. 2005. Restricted variable residues in the C-terminal segment of HIV-1 V3 loop regulate the molecular anatomy of CCR5 utilization. J. Mol. Biol. 350:699-712.
22. Hu, S. L., and L. Stamatatos. 2007. Prospects of HIV Env modification as an approach to HIV vaccine design. Curr. HIV Res. 5:507-513.
23. Huang, C. C., S. N. Lam, P. Acharya, M. Tang, S. H. Xiang, S. S. Hussan, R. L. Stanfield, J. Robinson, J. Sodroski, I. A. Wilson, R. Wyatt, C. A. Bewley, and P. D. Kwong. 2007. Structures of the CCR5 N terminus and of a tyrosine-sulfated antibody with HIV-1 gp120 and CD4. Science 317:1930-1934.
24. Huang, C. C., M. Tang, M. Y. Zhang, S. Majeed, E. Montabana, R. L. Stanfield, D. S. Dimitrov, B. Korber, J. Sodroski, I. A. Wilson, R. Wyatt, and P. D. Kwong. 2005. Structure of a V3-containing HIV-1 gp120 core. Science 310:1025-1028.
25. Javaherian, K., A. J. Langlois, G. J. LaRosa, A. T. Profy, D. P. Bolognesi, W. C. Herlihy, S. D. Putney, and T. J. Matthews. 1990. Broadly neutralizing antibodies elicited by the hypervariable neutralizing determinant of HIV-1. Science 250:1590-1593. (Pubitemid 120034375)
26. Javaherian, K., A. J. Langlois, C. McDanal, K. L. Ross, L. I. Eckler, C. L. Jellis, A. T. Profy, J. R. Rusche, D. P. Bolognesi, S. D. Putney, et al. 1989. Principal neutralizing domain of the human immunodeficiency virus type 1 envelope protein. Proc. Natl. Acad. Sci. USA 86:6768-6772.
27. Jeffs, S. A., J. McKeating, S. Lewis, H. Craft, D. Biram, P. E. Stephens, and R. L. Brady. 1996. Antigenicity of truncated forms of the human immunodeficiency virus type 1 envelope glycoprotein. J. Gen. Virol. 77(Pt. 7):1403-1410.
28. Johnston, S. H., M. A. Lobritz, S. Nguyen, K. Lassen, S. Delair, F. Posta, Y. J. Bryson, E. J. Arts, T. Chou, and B. Lee. 2009. A quantitative affinity-profiling system that reveals distinct CD4/CCR5 usage patterns among human immunodeficiency virus type 1 and simian immunodeficiency virus strains. J. Virol. 83:11016-11026.
29. Kajumo, F., D. A. Thompson, Y. Guo, and T. Dragic. 2000. Entry of R5X4 and X4 human immunodeficiency virus type 1 strains is mediated by negatively charged and tyrosine residues in the amino-terminal domain and the second extracellular loop of CXCR4. Virology 271:240-247. (Pubitemid 30461301)
30. Kuhmann, S. E., E. J. Platt, S. L. Kozak, and D. Kabat. 2000. Cooperation of multiple CCR5 coreceptors is required for infections by human immunodeficiency virus type 1. J. Virol. 74:7005-7015.
31. Kwong, P. D., R. Wyatt, J. Robinson, R. W. Sweet, J. Sodroski, and W. A. Hendrickson. 1998. Structure of an HIV gp120 envelope glycoprotein in complex with the CD4 receptor and a neutralizing human antibody. Nature 393:648-659.
32. Laakso, M. M., F. H. Lee, B. Haggarty, C. Agrawal, K. M. Nolan, M. Biscone, J. Romano, A. P. Jordan, G. J. Leslie, E. G. Meissner, L. Su, J. A. Hoxie, and R. W. Doms. 2007. V3 loop truncations in HIV-1 envelope impart resistance to coreceptor inhibitors and enhanced sensitivity to neutralizing antibodies. PLoS Pathog. 3:e117.
33. LaBranche, C. C., M. M. Sauter, B. S. Haggarty, P. J. Vance, J. Romano, T. K. Hart, P. J. Bugelski, and J. A. Hoxie. 1994. Biological, molecular, and structural analysis of a cytopathic variant from a molecularly cloned simian immunodeficiency virus. J. Virol. 68:5509-5522.
34. Labrijn, A. F., P. Poignard, A. Raja, M. B. Zwick, K. Delgado, M. Franti, J. Binley, V. Vivona, C. Grundner, C. C. Huang, M. Venturi, C. J. Petropoulos, T. Wrin, D. S. Dimitrov, J. Robinson, P. D. Kwong, R. T. Wyatt, J. Sodroski, and D. R. Burton. 2003. Access of antibody molecules to the conserved coreceptor binding site on glycoprotein gp120 is sterically restricted on primary human immunodeficiency virus type 1. J. Virol. 77:10557-10565.
35. Lassen, K. G., M. A. Lobritz, J. R. Bailey, S. Johnston, S. Nguyen, B. Lee, T. Chou, R. F. Siliciano, M. Markowitz, and E. J. Arts. 2009. Elite suppressor-derived HIV-1 envelope glycoproteins exhibit reduced entry efficiency and kinetics. PLoS Pathog. 5:e1000377.
36. Lee, B., M. Sharron, C. Blanpain, B. J. Doranz, J. Vakili, P. Setoh, E. Berg, G. Liu, H. R. Guy, S. R. Durell, M. Parmentier, C. N. Chang, K. Price, M. Tsang, and R. W. Doms. 1999. Epitope mapping of CCR5 reveals multiple conformational states and distinct but overlapping structures involved in chemokine and coreceptor function. J. Biol. Chem. 274:9617-9626.
37. Lee, B., M. Sharron, L. J. Montaner, D. Weissman, and R. W. Doms. 1999. Quantification of CD4, CCR5, and CXCR4 levels on lymphocyte subsets, dendritic cells, and differentially conditioned monocyte-derived macrophages. Proc. Natl. Acad. Sci. USA 96:5215-5220.
38. Lin, G., A. Bertolotti-Ciarlet, B. Haggarty, J. Romano, K. M. Nolan, G. J. Leslie, A. P. Jordan, C. C. Huang, P. D. Kwong, R. W. Doms, and J. A. Hoxie. 2007. Replication-competent variants of human immunodeficiency virus type 2 lacking the V3 loop exhibit resistance to chemokine receptor antagonists. J. Virol. 81:9956-9966. (Pubitemid 350067699)
39. Lin, G., B. Lee, B. S. Haggarty, R. W. Doms, and J. A. Hoxie. 2001. CD4-independent use of Rhesus CCR5 by human immunodeficiency virus type 2 implicates an electrostatic interaction between the CCR5 N terminus and the gp120 C4 domain. J. Virol. 75:10766-10778. (Pubitemid 33031546)
40. Maeda, K., D. Das, H. Ogata-Aoki, H. Nakata, T. Miyakawa, Y. Tojo, R. Norman, Y. Takaoka, J. Ding, G. F. Arnold, E. Arnold, and H. Mitsuya. 2006. Structural and molecular interactions of CCR5 inhibitors with CCR5. J. Biol. Chem. 281:12688-12698.
41. Magnus, C., P. Rusert, S. Bonhoeffer, A. Trkola, and R. R. Regoes. 2009. Estimating the stoichiometry of human immunodeficiency virus entry. J. Virol. 83:1523-1531.
42. Meissner, E. G., V. M. Coffield, and L. Su. 2005. Thymic pathogenicity of an HIV-1 envelope is associated with increased CXCR4 binding efficiency and V5-gp41-dependent activity, but not V1/V2-associated CD4 binding efficiency and viral entry. Virology 336:184-197.
43. Meissner, E. G., K. M. Duus, F. Gao, X. F. Yu, and L. Su. 2004. Characterization of a thymus-tropic HIV-1 isolate from a rapid progressor: role of the envelope. Virology 328:74-88.
44. Mkrtchyan, S. R., R. M. Markosyan, M. T. Eadon, J. P. Moore, G. B. Melikyan, and F. S. Cohen. 2005. Ternary complex formation of human immunodeficiency virus type 1 Env, CD4, and chemokine receptor captured as an intermediate of membrane fusion. J. Virol. 79:11161-11169.
45. Nara, P., L. Smit, N. Dunlop, W. Hatch, M. Merges, D. Waters, J. Kelliher, W. Krone, and J. Goudsmit. 1990. Evidence for rapid selection and deletion of HIV-1 subpopulations in vivo by V3-specific neutralizing antibody: a model of humoral-associated selection. Dev. Biol. Stand. 72:315-341.
46. Nolan, K. M., A. P. Jordan, and J. A. Hoxie. 2008. Effects of partial deletions within the human immunodeficiency virus type 1 V3 loop on coreceptor tropism and sensitivity to entry inhibitors. J. Virol. 82:664-673.
47. O'Doherty, U., W. J. Swiggard, and M. H. Malim. 2000. Human immunodeficiency virus type 1 spinoculation enhances infection through virus binding. J. Virol. 74:10074-10080. (Pubitemid 30780816)
48. Palker, T. J., M. E. Clark, A. J. Langlois, T. J. Matthews, K. J. Weinhold, R. R. Randall, D. P. Bolognesi, and B. F. Haynes. 1988. Type-specific neutralization of the human immunodeficiency virus with antibodies to envencoded synthetic peptides. Proc. Natl. Acad. Sci. USA 85:1932-1936.
49. Platt, E. J., J. P. Durnin, U. Shinde, and D. Kabat. 2007. An allosteric rheostat in HIV-1 gp120 reduces CCR5 stoichiometry required for membrane fusion and overcomes diverse entry limitations. J. Mol. Biol. 374:64-79.
50. Pugach, P., N. Ray, P. J. Klasse, T. J. Ketas, E. Michael, R. W. Doms, B. Lee, and J. P. Moore. 2009. Inefficient entry of vicriviroc-resistant HIV-1 via the inhibitor-CCR5 complex at low cell surface CCR5 densities. Virology 387:296-302.
51. Reeves, J. D., S. A. Gallo, N. Ahmad, J. L. Miamidian, P. E. Harvey, M. Sharron, S. Pohlmann, J. N. Sfakianos, C. A. Derdeyn, R. Blumenthal, E. Hunter, and R. W. Doms. 2002. Sensitivity of HIV-1 to entry inhibitors correlates with envelope/coreceptor affinity, receptor density, and fusion kinetics. Proc. Natl. Acad. Sci. USA 99:16249-16254.
52. Rizzuto, C., and J. Sodroski. 2000. Fine definition of a conserved CCR5-binding region on the human immunodeficiency virus type 1 glycoprotein 120. AIDS Res. Hum. Retrovir. 16:741-749.
53. Rucker, J., B. J. Doranz, A. L. Edinger, D. Long, J. F. Berson, and R. W. Doms. 1997. Cell-cell fusion assay to study role of chemokine receptors in human immunodeficiency virus type 1 entry. Methods Enzymol. 288:118-133. (Pubitemid 27443764)
54. Sattentau, Q. J., A. G. Dalgleish, R. A. Weiss, and P. C. Beverley. 1986. Epitopes of the CD4 antigen and HIV infection. Science 234:1120-1123.
55. Saunders, C. J., R. A. McCaffrey, I. Zharkikh, Z. Kraft, S. E. Malenbaum, B. Burke, C. Cheng-Mayer, and L. Stamatatos. 2005. The V1, V2, and V3 regions of the human immunodeficiency virus type 1 envelope differentially affect the viral phenotype in an isolate-dependent manner. J. Virol. 79:9069-9080.
56. Seibert, C., W. Ying, S. Gavrilov, F. Tsamis, S. E. Kuhmann, A. Palani, J. R. Tagat, J. W. Clader, S. W. McCombie, B. M. Baroudy, S. O. Smith, T. Dragic, J. P. Moore, and T. P. Sakmar. 2006. Interaction of small molecule inhibitors of HIV-1 entry with CCR5. Virology 349:41-54.
57. Selvarajah, S., B. Puffer, R. Pantophlet, M. Law, R. W. Doms, and D. R. Burton. 2005. Comparing antigenicity and immunogenicity of engineered gp120. J. Virol. 79:12148-12163. (Pubitemid 41346077)
58. Speck, R. F., K. Wehrly, E. J. Platt, R. E. Atchison, I. F. Charo, D. Kabat, B. Chesebro, and M. A. Goldsmith. 1997. Selective employment of chemokine receptors as human immunodeficiency virus type 1 coreceptors determined by individual amino acids within the envelope V3 loop. J. Virol. 71:7136-7139.
59. Sullivan, N., Y. Sun, J. Binley, J. Lee, C. F. Barbas III, P. W. Parren, D. R. Burton, and J. Sodroski. 1998. Determinants of human immunodeficiency virus type 1 envelope glycoprotein activation by soluble CD4 and monoclonal antibodies. J. Virol. 72:6332-6338. (Pubitemid 28323943)
60. Thali, M., J. P. Moore, C. Furman, M. Charles, D. D. Ho, J. Robinson, and J. Sodroski. 1993. Characterization of conserved human immunodeficiency virus type 1 gp120 neutralization epitopes exposed upon gp120-CD4 binding. J. Virol. 67:3978-3988. (Pubitemid 23180722)
61. Thompson, D. A., E. G. Cormier, and T. Dragic. 2002. CCR5 and CXCR4 usage by non-clade B human immunodeficiency virus type 1 primary isolates. J. Virol. 76:3059-3064.
62. Tsamis, F., S. Gavrilov, F. Kajumo, C. Seibert, S. Kuhmann, T. Ketas, A. Trkola, A. Palani, J. W. Clader, J. R. Tagat, S. McCombie, B. Baroudy, J. P. Moore, T. P. Sakmar, and T. Dragic. 2003. Analysis of the mechanism by which the small-molecule CCR5 antagonists SCH-351125 and SCH-350581 inhibit human immunodeficiency virus type 1 entry. J. Virol. 77:5201-5208. (Pubitemid 36460934)
63. Watson, C., S. Jenkinson, W. Kazmierski, and T. Kenakin. 2005. The CCR5 receptor-based mechanism of action of 873140, a potent allosteric noncompetitive HIV entry inhibitor. Mol. Pharmacol. 67:1268-1282.
64. Westby, M., C. Smith-Burchnell, J. Mori, M. Lewis, M. Mosley, M. Stockdale, P. Dorr, G. Ciaramella, and M. Perros. 2007. Reduced maximal inhibition in phenotypic susceptibility assays indicates that viral strains resistant to the CCR5 antagonist maraviroc utilize inhibitor-bound receptor for entry. J. Virol. 81:2359-2371. (Pubitemid 46303353)
65. Wu, L., G. LaRosa, N. Kassam, C. J. Gordon, H. Heath, N. Ruffing, H. Chen, J. Humblias, M. Samson, M. Parmentier, J. P. Moore, and C. R. Mackay. 1997. Interaction of chemokine receptor CCR5 with its ligands: multiple domains for HIV-1 gp120 binding and a single domain for chemokine binding. J. Exp. Med. 186:1373-1381.
66. Wyatt, R., J. Moore, M. Accola, E. Desjardin, J. Robinson, and J. Sodroski. 1995. Involvement of the V1/V2 variable loop structure in the exposure of human immunodeficiency virus type 1 gp120 epitopes induced by receptor binding. J. Virol. 69:5723-5733.
67. Wyatt, R., and J. Sodroski. 1998. The HIV-1 envelope glycoproteins: fusogens, antigens, and immunogens. Science 280:1884-1888. (Pubitemid 28299385)
68. Wyatt, R., N. Sullivan, M. Thali, H. Repke, D. Ho, J. Robinson, M. Posner, and J. Sodroski. 1993. Functional and immunologic characterization of human immunodeficiency virus type 1 envelope glycoproteins containing deletions of the major variable regions. J. Virol. 67:4557-4565. (Pubitemid 23215934)
69. Yang, X., S. Kurteva, S. Lee, and J. Sodroski. 2005. Stoichiometry of antibody neutralization of human immunodeficiency virus type 1. J. Virol. 79:3500-3508. (Pubitemid 40327938)
70. Yang, Z. Y., B. K. Chakrabarti, L. Xu, B. Welcher, W. P. Kong, K. Leung, A. Panet, J. R. Mascola, and G. J. Nabel. 2004. Selective modification of variable loops alters tropism and enhances immunogenicity of human immunodeficiency virus type 1 envelope. J. Virol. 78:4029-4036.
71. Zhong, P., M. Peeters, W. Janssens, K. Fransen, L. Heyndrickx, G. Vanham, B. Willems, P. Piot, and G. van der Groen. 1995. Correlation between genetic and biological properties of biologically cloned HIV type 1 viruses representing subtypes A, B, and D. AIDS Res. Hum. Retrovir. 11:239-248.