A CXC chemokine receptor, CXCR5/BLR1, is a novel and specific coreceptor for human immunodeficiency virus type 2.

G protein-coupled receptors serve as coreceptors in the infection process of human immunodeficiency virus type-1 (HIV-1), type-2 (HIV-2), and simian immunodeficiency virus (SIV). In this study, we showed that a CXC-CKR, CXCR5/BLR1, is a novel coreceptor for HIV-2, but for neither HIV-1 nor SIV. The expression of CXCR5 was detected by polymerase chain reaction after reverse transcription of cellular mRNA from S+L-HOS/CD4 cells and MT-2 human T cells, and the CXCR5 gene was cloned into an expression vector. S+L-HOS/CD4 cells were susceptible to several HIV-2 strains but not most HIV-1 strains. To examine a coreceptor activity of CXCR5, we used NP-2/CD4, which is a human glioma cell line, NP-2, transduced with the CD4 gene that shows strict resistance to infection with HIV-1, HIV-2, SIVmac, SIVagm, or SIVmnd strain. When CXCR5 was transduced into NP-2/CD4 cells, they became highly susceptible to HIV-2ROD and HIV-2CBL23 strains in a CD4-dependent manner but to not to HIV-1 or SIV strains. Anti-CXCR5 monoclonal antibody and a ligand for CXCR5, BCA-1, inhibited HIV-2 infection to NP-2/CD4/CXCR5 cells. Our findings suggest a possibility that CXCR5/BLR1 serves as a coreceptor for HIV-2 strains in vivo.

Kanbe K ，Shimizu N ，Soda Y ，Takagishi K ，Hoshino H ... -  《VIROLOGY》

Use of GPR1, GPR15, and STRL33 as coreceptors by diverse human immunodeficiency virus type 1 and simian immunodeficiency virus envelope proteins.

Human and simian immunodeficiency viruses (HIV and SIV, respectively) use chemokine receptors as coreceptors along with CD4 to mediate viral entry. Several orphan receptors, including GPR1, GPR15, and STRL33, can also serve as coreceptors for a more limited number of HIV and SIV isolates. We investigated whether these orphan receptors could function as efficient coreceptors for a diverse group of HIV and SIV envelopes (Envs) in comparison with the principal coreceptors CCR5 and CXCR4. We found that a limited number of HIV-1 isolates could mediate inefficient cell-cell fusion with the orphan receptors relative to CCR5 and CXCR4; however, none of the orphan receptors tested could support pseudotype virus infection despite robust infection via CCR5 or CXCR4. All except one of the SIV Envs tested mediated some degree of cell-cell fusion and pseudotype infection, with target cells expressing at least one of these orphan receptors, although CCR5 proved to be the most efficient coreceptor for infection. Only one SIV Env protein, BK28, could mediate infection using GPR1 as a coreceptor, albeit much less efficiently than with CCR5. In addition, use of these coreceptors did not correlate with the published tropism of the SIV clones and was strictly CD4 dependent for both SIV and HIV. We also examined the expression of these molecules in cell lines and primary cells widely used for virus propagation and as targets for infection. All cells examined expressed STRL33, a more limited number expressed GPR15, and GPR1 was much more restricted in its expression pattern. Taken together, our results indicate that GPR15 and STRL33 are rarely used by HIV-1 but are more frequently used by SIV strains, although not in a manner that correlates with SIV tropism.

Edinger AL ，Hoffman TL ，Sharron M ，Lee B ，O'Dowd B ，Doms RW ... -  《VIROLOGY》

CD4-Dependent and CD4-independent utilization of coreceptors by human immunodeficiency viruses type 2 and simian immunodeficiency viruses.

More than 10 G protein-coupled receptors (GPCRs) have been reported to act as coreceptors for entry of human and simian immunodeficiency viruses (HIV and SIV). We investigated the utilization of six GPCRs as coreceptors by T-cell-line-adapted HIV-2 strains (CBL-20, CBL-21, CBL-23, GH-1, ROD, and SBL6669) and SIV strains (SIVagmTYO-1, SIVmac251, and SIVmndGB-1). NP-2/CD4 cells were transduced with CCR3, CCR5, CCR8, CXCR4, GPR1, or APJ, and examined for susceptibilities to cell-free HIV/SIV. HIV-2 strains were grouped into two types by their coreceptor usage. The first group, CBL-20 and CBL-21, used CXCR4 exclusively; the other four strains used a few or all of the six coreceptors. These strains could further infect CD4-negative NP-2/CXCR4 or NP-2/CCR5 cells in the presence (all strains) or absence (SBL6669 and ROD strains) of soluble CD4. SIVagm and SIVmnd infected NP-2/CD4/GPR1 cells. The coreceptors CCR3, CCR8, GPR1, and APJ did not mediate the CD4-independent infection. Although HIV-2ROD and SIVmnd infected both NP-2/CD4/CXCR4 and NP-2/CD4/CCR5 cells, only CXCR4 and CCR5, respectively, were used in CD4-independent infection. Binding of virions to CD4-negative cells occurred at 4 degrees C. These findings suggest that there may be a correlation between the promiscuous use of coreceptors by HIV-2/SIV strains and their ability to infect CD4-negative cells.

Liu HY ，Soda Y ，Shimizu N ，Haraguchi Y ，Jinno A ，Takeuchi Y ，Hoshino H ... -  《VIROLOGY》

Nonproductive human immunodeficiency virus type 1 infection of human fetal astrocytes: independence from CD4 and major chemokine receptors.

Human immunodeficiency virus type 1 (HIV-1) infection of the brain is associated with neurological manifestations both in adults and in children. The primary target for HIV-1 infection in the brain is the microglia, but astrocytes can also be infected. We tested 26 primary HIV-1 isolates for their capacity to infect human fetal astrocytes in culture. Eight of these isolates, independent of their biological phenotype and chemokine receptor usage, were able to infect astrocytes. Although no sustained viral replication could be demonstrated, the virus was recovered by coculture with receptive cells such as macrophages or on stimulation with interleukin-1beta. To gain knowledge into the molecular events that regulate attachment and penetration of HIV-1 in astrocytes, we investigated the expression of several chemokine receptors. Fluorocytometry and calcium-mobilization assay did not provide evidence of expression of any of the major HIV-1 coreceptors, including CXCR4, CCR5, CCR3, and CCR2b, as well as the CD4 molecule on the cell surface of human fetal astrocytes. However, mRNA transcripts for CXCR4, CCR5, Bonzo/STRL33/TYMSTR, and APJ were detected by RT-PCR. Furthermore, infection of astrocytes by HIV-1 isolates with different chemokine receptor usage was not inhibited by the chemokines SDF-1beta, RANTES, MIP-1beta, or MCP-1 or by antibodies directed against the third variable region or the CD4 binding site of gp120. These data show that astrocytes can be infected by primary HIV-1 isolates via a mechanism independent of CD4 or major chemokine receptors. Furthermore, astrocytes are potential carriers of latent HIV-1 and on activation may be implicated in spreading the infection to other neighbouring cells, such as microglia or macrophages.

Sabri F ，Tresoldi E ，Di Stefano M ，Polo S ，Monaco MC ，Verani A ，Fiore JR ，Lusso P ，Major E ，Chiodi F ，Scarlatti G ... -  《VIROLOGY》

Establishment of a new system for determination of coreceptor usages of HIV based on the human glioma NP-2 cell line.

CD4 and one of the G-protein-coupled receptors (GPCRs) on the cell surface function as a receptor and a coreceptor, respectively, in infection of cells with human and simian immunodeficiency viruses (HIV/SIV). To determine which GPCRs can be coreceptors for HIV (HIV-1 and HIV-2) or SIV infection, several cell lines, including human osteosarcoma HOS-T4 cells and human glioma U87/CD4 cells, have been used. However, these cells often show susceptibilities to some HIV or SIV strains before transduction of GPCRs. The results of this study showed that a CD4-transduced human glioma cell line, NP-2/CD4, a human erythroleukemia cell line, K562/CD4, and a human ovarian cancer cell line, TYK/CD4, were completely resistant to the HIV-1 and HIV-2 strains tested. After transduction of several GPCRs into NP-2/CD4, K562/CD4, or TYK/CD4 cells, NP-2/CD4 cells but not K562/CD4 or TYK/CD4 cells mostly showed expected susceptibilities to several HIV strains. Therefore, an NP-2 cell system would be useful to determine the coreceptor usage of HIV isolates, to find a new coreceptor for HIV/SIV, and to analyze the early stages of HIV/SIV infection.

Soda Y ，Shimizu N ，Jinno A ，Liu HY ，Kanbe K ，Kitamura T ，Hoshino H ... -  《BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS》