CD4 Depletion in SIV-Infected Macaques Results in Macrophage and Microglia Infection with Rapid Turnover of Infected Cells

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CD4 tropism is conserved among all primate lentiviruses and likely contributes to viral pathogenesis by targeting cells that are critical for adaptive antiviral immune responses. Although CD4-independent variants of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) have been described that can utilize the coreceptor CCR5 or CXCR4 in the absence of CD4, these viruses typically retain their CD4 binding sites and still can interact with CD4. We describe the derivation of a novel CD4-independent variant of pathogenic SIVmac239, termed iMac239, that was used to derive an infectious R5-tropic SIV lacking a CD4 binding site. Of the seven mutations that differentiate iMac239 from wild-type SIVmac239, a single change (D178G) in the V1/V2 region was sufficient to confer CD4 independence in cell-cell fusion assays, although other mutations were required for replication competence. Like other CD4-independent viruses, iMac239 was highly neutralization sensitive, although mutations were identified that could confer CD4-independent infection without increasing its neutralization sensitivity. Strikingly, iMac239 retained the ability to replicate in cell lines and primary cells even when its CD4 binding site had been ablated by deletion of a highly conserved aspartic acid at position 385, which, for HIV-1, plays a critical role in CD4 binding. iMac239, with and without the D385 deletion, exhibited an expanded host range in primary rhesus peripheral blood mononuclear cells that included CCR5 ؉ CD8 ؉ T cells. As the first non-CD4-tropic SIV, iMac239-⌬D385 will afford the opportunity to directly assess the in vivo role of CD4 targeting on pathogenesis and host immune responses. IMPORTANCECD4 tropism is an invariant feature of primate lentiviruses and likely plays a key role in pathogenesis by focusing viral infection onto cells that mediate adaptive immune responses and in protecting virions attached to cells from neutralizing antibodies. Although CD4-independent viruses are well described for HIV and SIV, these viruses characteristically retain their CD4 binding site and can engage CD4 if available. We derived a novel CD4-independent, CCR5-tropic variant of the pathogenic molecular clone SIVmac239, termed iMac239. The genetic determinants of iMac239's CD4 independence provide new insights into mechanisms that underlie this phenotype. This virus remained replication competent even after its CD4 binding site had been ablated by mutagenesis. As the first truly non-CD4-tropic SIV, lacking the capacity to interact with CD4, iMac239 will provide the unique opportunity to evaluate SIV pathogenesis and host immune responses in the absence of the immunomodulatory effects of CD4 ؉ T cell targeting and infection.T he primate lentiviruses human immunodeficiency virus type 1 (HIV-1), HIV-2, and simian immunodeficiency virus (SIV) share a mechanism of target cell entry by interacting with CD4 and a member of the chemokine receptor family (1-3). CD4 binding to the envelope glycoprotein (Env) trimer initiates a ca...

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Derivation and Characterization of a CD4-Independent, Non-CD4-Tropic Simian Immunodeficiency Virus

Swanstrom

Haggarty

Jordan

et al. 2016

Self Cite

“…It was recently suggested that myeloid cells in the gut and lymphoid tissues from SIV-infected primates are resistant to infection and acquire SIV DNA primarily through the phagocytosis of infected T cells (90). However, it was reported that macrophages in lymph nodes and mucosal tissues get heavily infected in macaques depleted in CD4 ϩ T cells (91) and that the uptake of HIV-infected T lymphocytes by blood-derived macrophages leads to their infection (92). Macrophages are functionally and phenotypically extremely heterogeneous among anatomical sites.…”

Section: Discussionmentioning

confidence: 99%

Detection of Simian Immunodeficiency Virus in Semen, Urethra, and Male Reproductive Organs during Efficient Highly Active Antiretroviral Therapy

Matusali

Dereuddre-Bosquet

Tortorec

et al. 2015

A number of men receiving prolonged suppressive highly active antiretroviral therapy (HAART) still shed human immunodeficiency virus (HIV) in semen. To investigate whether this seminal shedding may be due to poor drug penetration and/or viral production by long-lived cells within male genital tissues, we analyzed semen and reproductive tissues from macaques chronically infected with simian immunodeficiency virus mac251 (SIVmac251) who were treated for 4 months with HAART, which was intensified over the last 7 weeks with an integrase inhibitor. We showed that a subset of treated animals continued shedding SIV in semen despite efficient HAART. This shedding was not associated with low antiretroviral drug concentrations in semen or in testis, epididymis, seminal vesicles, and prostate. HAART had no significant impact on SIV RNA in the urethra, whereas it drastically reduced SIV RNA levels in the prostate and vas deferens and to a lesser extent in the epididymis and seminal vesicle. The only detectable SIV RNA-positive cells within the male genital tract after HAART were urethral macrophages. SIV DNA levels in genital tissues were not decreased by HAART, suggesting the presence throughout the male genital tract of nonproductively infected cells. In conclusion, our results demonstrate that 4 months of HAART induced variable and limited control of viral infection in the male reproductive organs, particularly in the urethra, and suggest that infected long-lived cells in the male genital tract may be involved in persistent seminal shedding during HAART. These results pave the way for further investigations of male genital organ infection in long-term-treated infected individuals. IMPORTANCEA substantial subset of men receiving prolonged HAART suppressing viral loads in the blood still harbor HIV in semen, and cases of sexual transmission have been reported. To understand the origin of this persistence, we analyzed the semen and male reproductive tissues from SIV-infected macaques treated with HAART. We demonstrated that persistent seminal shedding was not linked to poor drug penetration in semen or semen-producing prostate, seminal vesicle, epididymis, and testis. We revealed that HAART decreased SIV RNA to various extents in all male genital organs, with the exception of the urethra, in which SIV RNA ؉ macrophages were observed despite HAART. Importantly, HAART did not impact SIV DNA levels in the male genital organs. These results suggest that infection of male genital organs, and particularly the urethra, could be involved in the release of virus in semen during HAART.A pproximately 35.3 million people worldwide are living with human immunodeficiency virus (HIV)/AIDS, and 2.3 million new infections occur annually (1). Over 80% of these new infections are caused by unprotected sexual intercourse. The risk of sexual transmission of HIV is strongly correlated with HIV RNA levels in genital secretions (2). Because semen is the most common vector of HIV dissemination worldwide (3-5), preventing HIV transmission by...

“…BAL, BaL viral Env protein; JRCSF, viral Env protein; AID, amplicon identifier; PID, patient identifier. been described during late-stage infection with a highly pathogenic X4 simian-human immunodeficiency virus (SHIV) and early in infection with simian immunodeficiency virus (SIV) when the animals were depleted of CD4 ϩ T cells using an anti-CD4 antibody (2,19). Collectively, these studies suggest that macrophage-tropic viruses evolve when CD4 ϩ T cells become limiting.…”

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confidence: 98%

“…Typically, this diversity has been analyzed as that of the viral population in the blood; however, virus can also be detected in other bodily fluids (reviewed in reference 1). Most virus detected in the blood is likely produced in lymphoid tissues that are not themselves easily sampled; thus, our knowledge of HIV-1 diversity across tissues is limited (2). Furthermore, this limitation affects our ability to analyze the possible unequal distributions of viral diversity throughout the infected host, which could affect treatment and cure efforts.…”

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confidence: 99%

R5 Macrophage-Tropic HIV-1 in the Male Genital Tract

Bednar

Hauser

et al. 2015

The entry tropism of HIV-1 Env proteins from virus isolated from the blood and genital tract of five men with compartmentalized lineages was determined. The Env proteins isolated from the genital tract of subject C018 were macrophage-tropic proteins, while the remaining cloned env genes encoded R5 T cell-tropic proteins. The detection of a macrophage-tropic lineage of HIV-1 within the male genital tract strongly suggests that evolution of macrophage-tropic viruses can occur in anatomically isolated sites outside the central nervous system.