Appearance of a Single Amino Acid Insertion at Position 33 in HIV Type 1 Protease Under a Lopinavir-Containing Regimen, Associated with Reduced Protease Inhibitor Susceptibility

ABSTRACT Many studies have demonstrated that the third variable region (V3) of the human immunodeficiency virus type 1 (HIV-1) envelope protein (Env) is a major determinant of coreceptor tropism. Other regions in the surface gp120 subunit of Env can modulate coreceptor tropism in a manner that is not fully understood. In this study, we evaluated the effect of env determinants outside of V3 on coreceptor usage through the analysis of (i) patient-derived env clones that differ in coreceptor tropism, (ii) chimeric env sequences, and (iii) site-directed mutants. The introduction of distinct V3 sequences from CXCR4-using clones into an R5-tropic env backbone conferred the inefficient use of CXCR4 in some but not all cases. Conversely, in many cases, X4- and dual-tropic env backbones containing the V3 sequences of R5-tropic clones retained the ability to use CXCR4, suggesting that sequences outside of the V3 regions of these CXCR4-using clones were responsible for CXCR4 use. The determinants of CXCR4 use in a set of dual-tropic env sequences with V3 sequences identical to those of R5-tropic clones mapped to the gp41 transmembrane (TM) subunit. In one case, a single-amino-acid substitution in the fusion peptide of TM was able to confer CXCR4 use; however, TM substitutions associated with CXCR4 use varied among different env sequences. These results demonstrate that sequences in TM can modulate coreceptor specificity and that env sequences other than that of V3 may facilitate efficient CXCR4-mediated entry. We hypothesize that the latter plays an important role in the transition from CCR5 to CXCR4 coreceptor use.

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Suppression of oncogenic Ras by mutant neurofibromatosis type 1 genes with single amino acid substitutions.

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.90.14.6706 ◽

1993 ◽

Vol 90 (14) ◽

pp. 6706-6710 ◽

Cited By ~ 11

Author(s):

M. Nakafuku ◽

M. Nagamine ◽

A. Ohtoshi ◽

K. Tanaka ◽

A. Toh-e ◽

...

Keyword(s):

Amino Acid ◽

Neurofibromatosis Type 1 ◽

Neurofibromatosis Type ◽

Single Amino Acid ◽

Amino Acid Substitutions ◽

Oncogenic Ras

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A Single Amino Acid Substitution in a Segment of the CA Protein within Gag That Has Similarity to Human Immunodeficiency Virus Type 1 Blocks Infectivity of a Human Endogenous Retrovirus K Provirus in the Human Genome

Journal of Virology ◽

10.1128/jvi.01439-08 ◽

2008 ◽

Vol 83 (2) ◽

pp. 1105-1114 ◽

Cited By ~ 14

Author(s):

David J. Heslin ◽

Pablo Murcia ◽

Frederick Arnaud ◽

Koenraad Van Doorslaer ◽

Massimo Palmarini ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Amino Acid ◽

Human Genome ◽

Particle Production ◽

Endogenous Retrovirus ◽

Single Amino Acid ◽

Human Endogenous Retrovirus ◽

C Terminus ◽

Immunodeficiency Virus

ABSTRACT Human endogenous retrovirus K (HERV-K) is the most intact retrovirus in the human genome. However, no single HERV-K provirus in the human genome today appears to be infectious. Since the Gag protein is the central component for the production of retrovirus particles, we investigated the abilities of Gag from two HERV-K proviruses to support production of virus-like particles and viral infectivity. HERV-K113 has full-length open reading frames for all viral proteins, while HERV-K101 has a full-length gag open reading frame and is expressed in human male germ cell tumors. The Gag of HERV-K101 allowed production of viral particles and infectivity, although at lower levels than observed with a consensus sequence Gag. Thus, including HERV-K109, at least two HERV-K proviruses in human genome today have functional Gag proteins. In contrast, HERV-K113 Gag supported only very low levels of particle production, and no infectivity was detectable due to a single amino acid substitution (I516M) near the extreme C terminus of the CA protein within Gag. The sequence of this portion of HERV-K CA showed similarities to that of human immunodeficiency virus type 1 and other primate immunodeficiency viruses. The extreme C terminus of CA may be a general determinant of retrovirus particle production. In addition, precise mapping of the defects in HERV-K proviruses as was done here identifies the key polymorphisms that need to be analyzed to assess the possible existence of infectious HERV-K alleles within the human population.

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Determinants of Syncytium Formation in Microglia by Human Immunodeficiency Virus Type 1: Role of the V1/V2 Domains

Journal of Virology ◽

10.1128/jvi.74.2.693-701.2000 ◽

2000 ◽

Vol 74 (2) ◽

pp. 693-701 ◽

Cited By ~ 35

Author(s):

Joseph T. C. Shieh ◽

Julio Martín ◽

Gordon Baltuch ◽

Michael H. Malim ◽

Francisco González-Scarano

Keyword(s):

Human Immunodeficiency Virus ◽

Amino Acid ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Syncytium Formation ◽

Single Amino Acid ◽

Single Amino Acid Change ◽

Immunodeficiency Virus ◽

Hiv 1

ABSTRACT Microglia are the main reservoir for human immunodeficiency virus type 1 (HIV-1) in the central nervous system (CNS), and multinucleated giant cells, the result of fusion of HIV-1-infected microglia and brain macrophages, are the neuropathologic hallmark of HIV dementia. One potential explanation for the formation of syncytia is viral adaptation for these CD4+ CNS cells. HIV-1BORI-15, a virus adapted to growth in microglia by sequential passage in vitro, mediates high levels of fusion and replicates more efficiently in microglia and monocyte-derived-macrophages than its unpassaged parent (J. M. Strizki, A. V. Albright, H. Sheng, M. O'Connor, L. Perrin, and F. Gonzalez-Scarano, J. Virol. 70:7654–7662, 1996). Since the interaction between the viral envelope glycoprotein and CD4 and the chemokine receptor mediates fusion and plays a key role in tropism, we have analyzed the HIV-1BORI-15 env as a fusogen and in recombinant and pseudotyped viruses. Its syncytium-forming phenotype is not the result of a switch in coreceptor use but rather of the HIV-1BORI-15envelope-mediated fusion of CD4+CCR5+ cells with greater efficiency than that of its parental strain, either by itself or in the context of a recombinant virus. Genetic analysis indicated that the syncytium-forming phenotype was due to four discrete amino acid differences in V1/V2, with a single-amino-acid change between the parent and the adapted virus (E153G) responsible for the majority of the effect. Additionally, HIV-1BORI-15 env-pseudotyped viruses were less sensitive to decreases in the levels of CD4 on transfected 293T cells, leading to the hypothesis that the differences in V1/V2 alter the interaction between this envelope and CD4 or CCR5, or both. In sum, the characterization of the envelope of HIV-1BORI-15, a highly fusogenic glycoprotein with genetic determinants in V1/V2, may lead to a better understanding of the relationship between HIV replication and syncytium formation in the CNS and of the importance of this region of gp120 in the interaction with CD4 and CCR5.

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