Brief Report: The Relationship Between Injection Drug Use Risk Behaviors and Markers of Immune Activation.

High levels of immune activation are reported for people who inject drugs. Studies of the relationship between injection behaviors and immune activation have yielded mixed results, in part due to lack of control for hepatitis C virus in analyses. This study, of 48 HIV-seronegative people who inject drugs, examines this relationship controlling for hepatitis C virus viremia.

Challenges in Recruiting People Who Use Drugs for HIV-Related Biomedical Research: Perspectives from the Field.

Recruitment of people who use drugs (PWUD) for HIV-related research has been undertaken since early in the epidemic. In early studies, recruitment was often performed by outreach workers with familiarity with the target population, who distributed risk reduction materials, and administered the surveys being conducted on drug use and risk behaviors. The evolution of effective treatments for HIV has provided opportunities for PWUD to participate in biobehavioral studies testing the efficacy of medical treatment advances and exploring the underlying biomedical basis for prevention and treatment efforts.

Helping Basic Scientists Engage With Community Partners to Enrich and Accelerate Translational Research.

Problem: Engaging basic scientists in community-based translational research is challenging but has great potential for improving health.

Approach: In 2009, The Rockefeller University Center for Clinical and Translational Science partnered with Clinical Directors Network, a practice-based research network (PBRN), to create a community-engaged research navigation (CEnR-Nav) program to foster research pairing basic science and community-driven scientific aims. The program is led by an academic navigator and a PBRN navigator.

Behavioural, Mucosal and Systemic Immune Parameters in HIV-infected and Uninfected Injection Drug Users.

Objective: Injection drug use (IDU) remains a major risk factor for HIV-1 acquisition. The complex interplay between drug use, non-sterile injection, and Hepatitis C remains poorly understood. We conducted a pilot study to determine the effect of IDU on immune parameters among HIV-uninfected and -infected individuals.

Species-specific activity of HIV-1 Vpu and positive selection of tetherin transmembrane domain variants.

Tetherin/BST-2/CD317 is a recently identified antiviral protein that blocks the release of nascent retrovirus, and other virus, particles from infected cells. An HIV-1 accessory protein, Vpu, acts as an antagonist of tetherin. Here, we show that positive selection is evident in primate tetherin sequences and that HIV-1 Vpu appears to have specifically adapted to antagonize variants of tetherin found in humans and chimpanzees.

Primate lentivirus capsid sensitivity to TRIM5 proteins.

Mammalian cells express several factors that inhibit lentiviral infection and that have been under strong selective pressure. One of these factors, TRIM5, targets the capsid protein of incoming retrovirus particles and inhibits subsequent steps of the replication cycle. By substituting human immunodeficiency virus type 1 capsid, we were able to show that a set of divergent primate lentivirus capsids was generally not susceptible to restriction by TRIM5 proteins from higher primates.

Tenofovir treatment augments anti-viral immunity against drug-resistant SIV challenge in chronically infected rhesus macaques.

Background: Emergence of drug-resistant strains of human immunodeficiency virus type 1 (HIV-1) is a major obstacle to successful antiretroviral therapy (ART) in HIV-infected patients. Whether antiviral immunity can augment ART by suppressing replication of drug-resistant HIV-1 in humans is not well understood, but can be explored in non-human primates infected with simian immunodeficiency virus (SIV). Rhesus macaques infected with live, attenuated SIV develop robust SIV-specific immune responses but remain viremic, often at low levels, for periods of months to years, thus providing a model in which to evaluate the contribution of antiviral immunity to drug efficacy.

Comparative analysis of the antiretroviral activity of APOBEC3G and APOBEC3F from primates.

APOBEC3G and APOBEC3F exhibit antiretroviral activity primarily as a consequence of their ability to deaminate cytidines in retroviral DNA. Here, we compare the properties of APOBEC3F and APOBEC3G from human, macaque, and African green monkey (AGM). While all APOBEC proteins tested exhibited anti-HIV-1 activity, human APOBEC3F was, surprisingly, 10- to 50-fold less potent than human APOBEC3G.

Evaluation of CD8+ T-cell and antibody responses following transient increased viraemia in rhesus macaques infected with live, attenuated simian immunodeficiency virus.

In vivo depletion of CD8+ T cells results in an increase in viral load in macaques chronically infected with simian immunodeficiency virus (SIVmac239deltanef). Here, the cellular and humoral immune responses associated with this transient period of enhanced viraemia in macaques infected with SIVmac239deltanef were characterized. Fourteen days after in vivo CD8+ T-cell depletion, two of six macaques experienced a 1-2 log10 increase in anti-gp130 and p27 antibody titres and a three- to fivefold increase in gamma interferon-ecreting SIV-specific CD8+ T cells.

HECT ubiquitin ligases link viral and cellular PPXY motifs to the vacuolar protein-sorting pathway.

Many enveloped viruses exploit the class E vacuolar protein-sorting (VPS) pathway to bud from cells, and use peptide motifs to recruit specific class E VPS factors. Homologous to E6AP COOH terminus (HECT) ubiquitin ligases have been implicated as cofactors for PPXY motif-dependent budding, but precisely which members of this family are responsible, and how they access the VPS pathway is unclear. Here, we show that PPXY-dependent viral budding is unusually sensitive to inhibitory fragments derived from specific HECT ubiquitin ligases, namely WWP1 and WWP2.

Identification of human VPS37C, a component of endosomal sorting complex required for transport-I important for viral budding.

Endosomal sorting complex required for transport-I (ESCRT-I) is one of three defined protein complexes in the class E vacuolar protein sorting (VPS) pathway required for the sorting of ubiquitinated transmembrane proteins into internal vesicles of multivesicular bodies. In yeast, ESCRT-I is composed of three proteins, VSP23, VPS28, and VPS37, whereas in mammals only Tsg101(VPS23) and VPS28 were originally identified as ESCRT-I components. Using yeast two-hybrid screens, we identified one of a family of human proteins (VPS37C) as a Tsg101-binding protein.

APOBEC3G incorporation into human immunodeficiency virus type 1 particles.

APOBEC3G is promiscuous with respect to its antiretroviral effect, requiring that it be packaged into diverse retrovirus particles. Here, we show that most virally encoded human immunodeficiency virus type 1 particle components are dispensable for APOPEC3G incorporation. However, replacement of the nucleocapsid (NC) Gag domain with a leucine zipper abolished APOBEC3G incorporation.

Human immunodeficiency virus type 1 matrix inhibits and confers cooperativity on gag precursor-membrane interactions.

Human immunodeficiency virus type 1 (HIV-1) Gag multimerization and membrane binding are required for particle formation. However, it is unclear what constitutes a minimal plasma membrane-specific targeting signal and what role the matrix (MA) globular head and other Gag domains play in membrane targeting. Here, we use membrane flotation and microscopic analysis of Gag deletion mutants to demonstrate that the HIV-1 MA globular head inhibits a plasma membrane-specific targeting signal contained within the six amino-terminal MA residues.

Capsid-dependent and -independent postentry restriction of primate lentivirus tropism in rodent cells.

Retrovirus tropism can be restricted by cellular factors such as Fv1, Ref1, and Lv1 that inhibit infection by targeting the incoming viral capsid. Here, we show that rodent cells exhibit differential sensitivity to infection by vesicular stomatitis virus G-pseudotyped lentiviruses and that differences between human immunodeficiency virus type 1 and simian immunodeficiency virus (SIVmac) infectivity are sometimes, but not always, governed by determinants in capsid-p2. In at least one case, resistance to SIVmac infection could be eliminated by saturation of target cells with noninfectious SIVmac particles.

Role of ESCRT-I in retroviral budding.

Retroviral late-budding (L) domains are required for the efficient release of nascent virions. The three known types of L domain, designated according to essential tetrapeptide motifs (PTAP, PPXY, or YPDL), each bind distinct cellular cofactors. We and others have demonstrated that recruitment of an ESCRT-I subunit, Tsg101, a component of the class E vacuolar protein sorting (VPS) machinery, is required for the budding of viruses, such as human immunodeficiency virus type 1 (HIV-1) and Ebola virus, that encode a PTAP-type L domain, but subsequent events remain undefined.

Restriction of multiple divergent retroviruses by Lv1 and Ref1.

The mouse gene Fv1 encodes a saturable restriction factor that selectively blocks infection by N-tropic or B-tropic murine leukemia virus (MLV) strains. Despite the absence of an Fv1 gene, a similar activity is present in humans that blocks N-MLV infection (Ref1). Moreover, some non-human primate cell lines express a potentially related inhibitor of HIV-1 and/or SIVmac infection (Lv1).

The liver is a major organ for clearing simian immunodeficiency virus in rhesus monkeys.

Infection with human or simian immunodeficiency virus (SIV) is characterized by the rapid turnover of both viral particles and productively infected cells. It has recently been reported that the clearance of SIV in vivo is exceedingly fast, with half-lives on the order of minutes. The underlying mechanism or site responsible for this rapid clearance, however, remains unknown.

HIV-1 and Ebola virus encode small peptide motifs that recruit Tsg101 to sites of particle assembly to facilitate egress.

Retroviral Gag proteins encode sequences, termed late domains, which facilitate the final stages of particle budding from the plasma membrane. We report here that interactions between Tsg101, a factor involved in endosomal protein sorting, and short peptide motifs in the HIV-1 Gag late domain and Ebola virus matrix (EbVp40) proteins are essential for efficient egress of HIV-1 virions and Ebola virus-like particles. EbVp40 recruits Tsg101 to sites of particle assembly and a short, EbVp40-derived Tsg101-binding peptide sequence can functionally substitute for the HIV-1 Gag late domain.

High-resolution analysis of T-cell receptor beta-chain repertoires using DNA heteroduplex tracking: generally stable, clonal CD8+ expansions in all healthy young adults.

The accurate measurement of T-cell receptor (TCR) repertoire changes requires the analysis of a representative sampling of complex T-cell populations. The number and frequency of clonally expanded TCR beta-chain transcripts bearing distinct CDR3 sequences were accurately determined using a simple DNA heteroduplex tracking assay. This method allowed major and minor clonal expansions (> or = 1% of a Vbeta subfamily's transcripts) to be rapidly and reproducibly quantified.

CD4-immunoglobulin G2 protects Hu-PBL-SCID mice against challenge by primary human immunodeficiency virus type 1 isolates.

CD4-immunoglobulin G2 (IgG2) is a fusion protein comprising human IgG2 in which the Fv portions of both heavy and light chains have been replaced by the V1 and V2 domains of human CD4. Previous studies found that CD4-IgG2 potently neutralizes a broad range of primary human immunodeficiency virus type 1 (HIV-1) isolates in vitro and ex vivo. The current report demonstrates that CD4-IgG2 protects against infection by primary isolates of HIV-1 in vivo, using the hu-PBL-SCID mouse model.

Human immunodeficiency virus type 1 populations in blood and semen.

Transmission of human immunodeficiency virus type 1 (HIV-1) usually results in outgrowth of viruses with macrophage-tropic phenotype and consensus non-syncytium-inducing (NSI) V3 loop sequences, despite the presence of virus with broader host range and the syncytium-inducing (SI) phenotype in the blood of many donors. We examined proviruses in contemporaneous peripheral blood mononuclear cells (PBMC) and non-spermatozoal semen mononuclear cells (NSMC) of five HIV-1-infected individuals to determine if this preferential outgrowth could be due to compartmentalization and thus preferential transmission of viruses of the NSI phenotype from the male genital tract. Phylogenetic reconstructions of approximately 700-bp sequences covering the second constant region through the fifth variable region (C2 to V5) of the viral envelope gene revealed distinct variant populations in the blood versus the semen in two patients with AIDS and in one asymptomatic individual (patient 613), whereas similar variant populations were found in both compartments in two other asymptomatic individuals.

Macrophages and CD4+ T lymphocytes from two multiply exposed, uninfected individuals resist infection with primary non-syncytium-inducing isolates of human immunodeficiency virus type 1.

Despite multiple, high-risk sexual exposures, some individuals remain uninfected with human immunodeficiency virus type 1 (HIV-1). CD4+ lymphocytes from these individuals are less susceptible to infection in vitro with some strains of HIV-1, suggesting that the phenotype of the virus may influence its ability to interact with certain CD4+ cells. In the present study, we examined the susceptibility of CD4+ T lymphocytes and macrophages from two exposed uninfected individuals (EU2 and EU3) to infection with a panel of biologically cloned isolates of HIV-1 having either a non-syncytium-inducing (NSI) or a syncytium-inducing (SI) phenotype.