HIV type 1 molecular clones able to use the Bonzo/STRL-33 coreceptor for virus entry

The Role of CXCL16 in the Pathogenesis of Cancer and Other Diseases

CXCL16 is a chemotactic cytokine belonging to the α-chemokine subfamily. It plays a significant role in the progression of cancer, as well as the course of atherosclerosis, renal fibrosis, and non-alcoholic fatty liver disease (NAFLD). Since there has been no review paper discussing the importance of this chemokine in various diseases, we have collected all available knowledge about CXCL16 in this review. In the first part of the paper, we discuss background information about CXCL16 and its receptor, CXCR6. Next, we focus on the importance of CXCL16 in a variety of diseases, with an emphasis on cancer. We discuss the role of CXCL16 in tumor cell proliferation, migration, invasion, and metastasis. Next, we describe the role of CXCL16 in the tumor microenvironment, including involvement in angiogenesis, and its significance in tumor-associated cells (cancer associated fibroblasts (CAF), microglia, tumor-associated macrophages (TAM), tumor-associated neutrophils (TAN), mesenchymal stem cells (MSC), myeloid suppressor cells (MDSC), and regulatory T cells (T_reg)). Finally, we focus on the antitumor properties of CXCL16, which are mainly caused by natural killer T (NKT) cells. At the end of the article, we summarize the importance of CXCL16 in cancer therapy.

Marginal Effects of Systemic CCR5 Blockade with Maraviroc on Oral Simian Immunodeficiency Virus Transmission to Infant Macaques

Current approaches do not eliminate all human immunodeficiency virus type 1 (HIV-1) maternal-to-infant transmissions (MTIT); new prevention paradigms might help avert new infections. We administered maraviroc (MVC) to rhesus macaques (RMs) to block CCR5-mediated entry, followed by repeated oral exposure of a CCR5-dependent clone of simian immunodeficiency virus (SIV) mac251 (SIVmac766). MVC significantly blocked the CCR5 coreceptor in peripheral blood mononuclear cells and tissue cells. All control animals and 60% of MVC-treated infant RMs became infected by the 6th challenge, with no significant difference between the number of exposures (P = 0.15). At the time of viral exposures, MVC plasma and tissue (including tonsil) concentrations were within the range seen in humans receiving MVC as a therapeutic. Both treated and control RMs were infected with only a single transmitted/founder variant, consistent with the dose of virus typical of HIV-1 infection. The uninfected RMs expressed the lowest levels of CCR5 on the CD4+ T cells. Ramp-up viremia was significantly delayed (P = 0.05) in the MVC-treated RMs, yet peak and postpeak viral loads were similar in treated and control RMs. In conclusion, in spite of apparent effective CCR5 blockade in infant RMs, MVC had a marginal impact on acquisition and only a minimal impact on the postinfection delay of viremia following oral SIV infection. Newly developed, more effective CCR5 blockers may have a more dramatic impact on oral SIV transmission than MVC.IMPORTANCE We have previously suggested that the very low levels of simian immunodeficiency virus (SIV) maternal-to-infant transmissions (MTIT) in African nonhuman primates that are natural hosts of SIVs are due to a low availability of target cells (CCR5+ CD4+ T cells) in the oral mucosa of the infants, rather than maternal and milk factors. To confirm this new MTIT paradigm, we performed a proof-of-concept study in which we therapeutically blocked CCR5 with maraviroc (MVC) and orally exposed MVC-treated and naive infant rhesus macaques to SIV. MVC had only a marginal effect on oral SIV transmission. However, the observation that the infant RMs that remained uninfected at the completion of the study, after 6 repeated viral challenges, had the lowest CCR5 expression on the CD4+ T cells prior to the MVC treatment appears to confirm our hypothesis, also suggesting that the partial effect of MVC is due to a limited efficacy of the drug. New, more effective CCR5 inhibitors may have a better effect in preventing SIV and HIV transmission.

Selectivity in the Use of Gi/o Proteins Is Determined by the DRF Motif in CXCR6 and Is Cell-Type Specific

CXCR6, the receptor for CXCL16, is expressed on multiple cell types and can be a coreceptor for human immunodeficiency virus 1. Except for CXCR6, all human chemokine receptors contain the D(3.49)R(3.50)Y(3.51) sequence, and all but two contain A(3.53) at the cytoplasmic terminus of the third transmembrane helix (H3C), a region within class A G protein-coupled receptors that contacts G proteins. In CXCR6, H3C contains D(3.49)R(3.50)F(3.51)I(3.52)V(3.53) at positions 126-130. We investigated the importance and interdependence of the canonical D126 and the noncanonical F128 and V130 in CXCR6 by mutating D126 to Y, F128 to Y, and V130 to A singly and in combination. For comparison, we mutated the analogous positions D142, Y144, and A146 to Y, F, and V, respectively, in CCR6, a related receptor containing the canonical sequences. Mutants were analyzed in both human embryonic kidney 293T and Jurkat E6-1 cells. Our data show that for CXCR6 and/or CCR6, mutations in H3C can affect both receptor signaling and chemokine binding; noncanonical H3C sequences are functionally linked, with dual changes mitigating the effects of single mutations; mutations in H3C that compromise receptor activity show selective defects in the use of individual Gi/o proteins; and the effects of mutations in H3C on receptor function and selectivity in Gi/o protein use can be cell-type specific. Our findings indicate that the ability of CXCR6 to make promiscuous use of the available Gi/o proteins is exquisitely dependent on sequences within the H3C and suggest that the native sequence allows for preservation of this function across different cellular environments.

Toll-like receptor 3 signalling up-regulates expression of the HIV co-receptor G-protein coupled receptor 15 on human CD4+ T cells

Background

Many HIV-2 and SIV isolates, as well as some HIV-1 strains, can use the orphan 7-transmembrane receptor GPR15 as co-receptor for efficient entry into host cells. GPR15 is expressed on central memory and effector memory CD4⁺ T cells in healthy individuals and a subset of these cells is susceptible to HIV-1 and SIV infection. However, it has not been determined whether GPR15 expression is altered in the context of HIV-1 infection.

Results

Here, we show that GPR15 expression in CD4⁺ T cells is markedly up-regulated in some HIV-1 infected individuals compared to the rest of the infected patients and to healthy controls. Infection of the PM1 T cell line with primary HIV-1 isolates was found to up-regulate GPR15 expression on the infected cells, indicating that viral components can induce GPR15 expression. Up-regulation of GPR15 expression on CD4⁺ T cells was induced by activation of Toll-like receptor 3 signalling via TIR-domain-containing adapter-inducing interferon-β (TRIF) and was more prominent on gut-homing compared to lymph node-homing CD4⁺ T cells.

Conclusion

These results suggest that infection-induced up-regulation of GPR15 expression could increase susceptibility of CD4⁺ T cells to HIV infection and target cell availability in the gut in some infected individuals.

International Union of Basic and Clinical Pharmacology. [corrected]. LXXXIX. Update on the extended family of chemokine receptors and introducing a new nomenclature for atypical chemokine receptors

Sixteen years ago, the Nomenclature Committee of the International Union of Pharmacology approved a system for naming human seven-transmembrane (7TM) G protein-coupled chemokine receptors, the large family of leukocyte chemoattractant receptors that regulates immune system development and function, in large part by mediating leukocyte trafficking. This was announced in Pharmacological Reviews in a major overview of the first decade of research in this field [Murphy PM, Baggiolini M, Charo IF, Hébert CA, Horuk R, Matsushima K, Miller LH, Oppenheim JJ, and Power CA (2000) Pharmacol Rev 52:145-176]. Since then, several new receptors have been discovered, and major advances have been made for the others in many areas, including structural biology, signal transduction mechanisms, biology, and pharmacology. New and diverse roles have been identified in infection, immunity, inflammation, development, cancer, and other areas. The first two drugs acting at chemokine receptors have been approved by the U.S. Food and Drug Administration (FDA), maraviroc targeting CCR5 in human immunodeficiency virus (HIV)/AIDS, and plerixafor targeting CXCR4 for stem cell mobilization for transplantation in cancer, and other candidates are now undergoing pivotal clinical trials for diverse disease indications. In addition, a subfamily of atypical chemokine receptors has emerged that may signal through arrestins instead of G proteins to act as chemokine scavengers, and many microbial and invertebrate G protein-coupled chemokine receptors and soluble chemokine-binding proteins have been described. Here, we review this extended family of chemokine receptors and chemokine-binding proteins at the basic, translational, and clinical levels, including an update on drug development. We also introduce a new nomenclature for atypical chemokine receptors with the stem ACKR (atypical chemokine receptor) approved by the Nomenclature Committee of the International Union of Pharmacology and the Human Genome Nomenclature Committee.

Could differential virological characteristics account for ongoing viral replication and insidious damage of the brain during HIV 1 infection of the central nervous system?

Neurocognitive disorders due to human immunodeficiency virus type 1 (HIV-1) infection have been reported in 25-60% of cases,(1-3) despite a sustained viral response in peripheral blood while on highly active anti-retroviral therapy (HAART). A possible reason may be that the central nervous system (CNS) is less accessible for anti-retroviral agents, therefore this sanctuary site can provide a reservoir for ongoing HIV-1 replication. Mutations conferring resistance to anti-retroviral drugs may predominate in compartments where drug levels are suboptimal. This review provides an overview on the literature regarding the development of resistance mutations and the sensitivity for co-receptors in CNS. Mutations caused by the anti-retroviral drugs with the lowest intracerebral penetration would be expected to be found in higher percentages in the CNS than in the periphery of the human body. However, few studies have been performed that can confirm or reject this claim. Zidovudine, the anti-retroviral drug with the best intracerebral penetration, has been studied to some extent. This drug indeed induces resistance mutations in blood as well as the CNS. HAART induces a switch from HIV that uses co-receptor CRR5 to HIV that uses co-receptor CXCR4. This switch may appear later in the CNS compartment compared to the periphery. However, current literature shows conflicting evidence. In conclusion, the current understanding of HIV-strain evolution under drug pressure in sanctuary sites like CNS is incomplete. Therefore, more research is needed in order to establish the role of these sites in the development of drug resistant mutants under adequate HAART.

HIV-1 coreceptors and their inhibitors

Entry of human immunodeficiency virus (HIV) into target cells is mediated by the viral Envelope glycoprotein (Env) and its coordinated interaction with a receptor (CD4) and a coreceptor (usually the chemokine receptors CCR5 or CXCR4). This review describes the identification of chemokine receptors as coreceptors for HIV-1 Env-mediated fusion, the determinants of chemokine receptor usage, and the impact of nonfunctional chemokine receptor alleles on HIV-1 resistance and disease progression. Due to the important role of chemokine receptors in HIV-1 entry, inhibitors of these coreceptors are good candidates for blocking entry and development of antiretroviral therapies. We discuss the different CCR5- and CXCR4-based antiretroviral drugs that have been developed thus far, highlighting the most promising drug candidates. Resistance to these coreceptor inhibitors as well as the impact of these drugs on clinical monitoring and treatment are also discussed.

Use of alternate coreceptors on primary cells by two HIV-1 isolates

Two HIV-1 isolates (CM4 and CM9) able to use alternate HIV-1 coreceptors on transfected cell lines were tested for their sensitivity to inhibitors of HIV-1 entry on primary cells. CM4 was able to use CCR5 and Bob/GPR15 efficiently in transfected cells. The R5 isolate grew in Delta32/Delta32 CCR5 PBMC in the absence or presence of AMD3100, a CXCR4-specific inhibitor, indicating that it uses a receptor other than CCR5 or CXCR4 on primary cells. It was insensitive to the CCR5 entry inhibitors RANTES and PRO140, but was partially inhibited by vMIP-1, a chemokine that binds CCR3, CCR8, GPR15 and CXCR6. The coreceptor used by this isolate on primary cells is currently unknown. CM9 used CCR5, CXCR4, Bob/GPR15, CXCR6, CCR3, and CCR8 on transfected cells and was able to replicate in the absence or presence of AMD3100 in Delta32/Delta32 CCR5 PBMC. It was insensitive to eotaxin, vMIP-1 and I309 when tested individually, but was inhibited completely when vMIP-1 or I309 was combined with AMD3100. Both I309 and vMIP-1 bind CCR8, strongly suggesting that this isolate can use CCR8 on primary cells. Collectively, these data suggest that some HIV-1 isolates can use alternate coreceptors on primary cells, which may have implications for strategies that aim to block viral entry.

The CCR5 and CXCR4 coreceptors--central to understanding the transmission and pathogenesis of human immunodeficiency virus type 1 infection

In this review, we will discuss what is known, what is suspected, and what still remains obscure about the central role played by coreceptor expression and usage in the transmission and pathogenic consequences of human immunodeficiency virus type 1 (HIV-1) infection. An emphasis will be on the HIV-1 phenotypic variants that are defined by their usage of the CCR5 or CXCR4 coreceptors, and how the different cellular tropism of these variants influences how and where HIV-1 replicates in vivo. We will also review what might happen when coreceptor antagonists are used clinically to treat HIV-1 infection.

The N-linked glycan g15 within the V3 loop of the HIV-1 external glycoprotein gp120 affects coreceptor usage, cellular tropism, and neutralization

We have studied infectivity and neutralization of X4, R5, and R5X4 tropic HIV-1 mutants, which are lacking N-linked glycosylation sites for glycans g13, g14, g15, and g17 in the V3 loop region of gp120. X4-tropic NL4-3 mutants lacking combinations of g14/15 or g15/17 showed markedly higher infectivity in CXCR4-specific infection. The role of g15 in CCR5-specific infection was investigated using viruses with high (NL-918, R5-monotropic), medium (NL-991, R5-monotropic), and low (NL-952, R5X4-dualtropic) CCR5-specific infectivity. For NL-991, a reduction of infectivity on GHOST-CCR5 cells was observed for a mutant lacking g15. For NL-952 mutants all lacking g15, a complete loss of CCR5-specificity was observed and NL-952 was shifted from R5X4 to X4 tropism. For all mutants of NL4-3, NL-991, and NL-952, where the lack of g15 markedly influenced infectivity or coreceptor usage, neutralization was enhanced. In contrast, NL-918 mutants with or without g15 showed no difference in neutralization and no difference in GHOST-CCR5 infection rates. Thus, for viruses with a low or medium CCR5-specificity the role of g15 for changing CCR5-usage and sensitivity to neutralization was more significant than for viruses with high infection rates on GHOST-CCR5 cells. Our data demonstrate that V3 glycans play an important role in the usage of CXCR4 and CCR5. The lack of g15 was relevant for a more efficient use of CXCR4, whereas interaction with CCR5 was facilitated in the presence of g15. This study also demonstrates that glycan g15 is involved in blocking of neutralizing antibodies and shifting HIV tropism from R5X4 to X4.

The transcriptional map of the common eliminated region 1 (C3CER1) in 3p21.3

Occurrence of chromosome 3p deletions in a large number of human tumours suggests the existence of uncharted tumour suppressor gene(s). We previously applied a functional assay, named the Elimination test (Et), for the identification of regions containing tumour growth antagonising genes. This resulted in the definition of chromosome 3 common eliminated region 1 (C3CER1) on 3p21.3, which is regularly eliminated from SCID-derived tumours. Systematic genomic sequencing of 11 PAC clones, combined with comparisons of genomic sequence against EST databases and PCR-based cloning of cDNA sequences allowed us to assemble a comprehensive transcriptional map of 1.4 Mb that includes 19 active genes and three processed pseudogenes. We report four novel genes: FYVE and coiled-coil domain containing 1 (FYCO1), transmembrane protein 7 (TMEM7), leucine-rich repeat-containing 2 (LRRC2) and leucine zipper protein 3 (LUZP3). A striking feature of C3CER1 is a presence of a cluster of eight chemokine receptor genes. Based on a new analysis of the microcell hybrid-derived panel of SCID tumours we also redefined the centromeric border of the C3CER1. It is now located within LRRC2 gene, which is a relative of RSP-1 (Ras Suppressor Protein 1). The detailed knowledge of gene content in C3CER1 is a prerequisite for functional analysis of these genes and understanding of their possible role in tumorigenesis.

Maintenance of glycoprotein-determined phenotype in an HIV type 1 (pNL43) env gene-cassetting system

Here we report the construction and use of a full-length env gene-cassetting system, C2, based on the HIV-1 infectious molecular clone NL43. C2 produces virus with the same phenotype as NL43 but with 2-fold lower growth kinetics. The latter probably relates to alteration in the vpu and/or nef genes. C2-env chimeras of macrophage-tropic and T cell-tropic laboratory strains and primary HIV-1 isolates retain the glycoprotein-determined phenotypes of their parent viruses. The cassette will assist studies of HIV-1 pathogenesis.