Human immunodeficiency virus type 2 (HIV2)

APOBEC3B Potently Restricts HIV-2 but Not HIV-1 in a Vif-Dependent Manner

Vif is a lentiviral accessory protein that counteracts the antiviral activity of cellular APOBEC3 (A3) cytidine deaminases in infected cells. The exact contribution of each member of the A3 family for the restriction of HIV-2 is still unclear. Thus, the aim of this work was to identify the A3s with anti-HIV-2 activity and compare their restriction potential for HIV-2 and HIV-1. We found that A3G is a strong restriction factor of both types of viruses and A3C restricts neither HIV-1 nor HIV-2. Importantly, A3B exhibited potent antiviral activity against HIV-2, but its effect was negligible against HIV-1. Whereas A3B is packaged with similar efficiency into both viruses in the absence of Vif, HIV-2 and HIV-1 differ in their sensitivity to A3B. HIV-2 Vif targets A3B by reducing its cellular levels and inhibiting its packaging into virions, whereas HIV-1 Vif did not evolve to antagonize A3B. Our observations support the hypothesis that during wild-type HIV-1 and HIV-2 infections, both viruses are able to replicate in host cells expressing A3B but using different mechanisms, probably resulting from a Vif functional adaptation over evolutionary time. Our findings provide new insights into the differences between Vif protein and their cellular partners in the two human viruses. Of note, A3B is highly expressed in some cancer cells and may cause deamination-induced mutations in these cancers. Thus, A3B may represent an important therapeutic target. As such, the ability of HIV-2 Vif to induce A3B degradation could be an effective tool for cancer therapy. IMPORTANCE Primate lentiviruses encode a series of accessory genes that facilitate virus adaptation to its host. Among those, the vif-encoded protein functions primarily by targeting the APOBEC3 (A3) family of cytidine deaminases. All lentiviral Vif proteins have the ability to antagonize A3G; however, antagonizing other members of the A3 family is variable. Here, we report that HIV-2 Vif, unlike HIV-1 Vif, can induce degradation of A3B. Consequently, HIV-2 Vif but not HIV-1 Vif can inhibit the packaging of A3B. Interestingly, while A3B is packaged efficiently into the core of both HIV-1 and HIV-2 virions in the absence of Vif, it only affects the infectivity of HIV-2 particles. Thus, HIV-1 and HIV-2 have evolved two distinct mechanisms to antagonize the antiviral activity of A3B. Aside from its antiviral activity, A3B has been associated with mutations in some cancers. Degradation of A3B by HIV-2 Vif may be useful for cancer therapies.

Rapid and sensitive detection of HIV-1 p24 antigen by immunomagnetic separation coupled with catalytic fluorescent immunoassay

In this study, a system of magnetic beads (MBs) coupled with catalytic fluorescent immunoassay for rapid and sensitive determination of HIV-1 capsid antigen p24 was developed. p24 was captured by antibody immobilized MBs, and the detection antibody was linked to horseradish peroxidase (HRP) through biotin-streptavidin recognition, catalyzing the oxidation of o-phenylenediamine (OPD) and hydrogen peroxide to produce a fluorescent product. This is the first reported utilization of the fluorescence of OPD oxidation product catalyzed by HRP for immunoassay. Optimization of conditions afforded a low detection limit of 0.5 pg/mL (3σ) for p24 with a linear range of 1.4-90.0 pg/mL. The assay exhibited good reproducibility with a relative standard deviation (RSD) of 4.4 %, 4.7 %, and 5.0 % for detecting 1.4 pg/mL, 22.5 pg/mL, and 45.0 pg/mL p24, respectively. The assay can be completed in less than 90 min. Moreover, the proposed method was successfully applied to detect p24 in spiked serum. This method overcomes the interference of MBs to the fluorescence signal and demonstrated higher sensitivity for detection of p24 than conventional ELISA kits. The system could be applied for detecting other antigens with high sensitivity, rapidity, specificity, and simple operation. Graphical Abstract A rapid and sensitive biosensing method coupling immunomagnetic separation and catalytic fluorescence for determination of HIV-1 p24 has been developed.

Engineering regulable Escherichia coli beta-galactosidases as biosensors for anti-HIV antibody detection in human sera

The activity of engineered, peptide-displaying enzymes is modulated by binding to specific anti-peptide antibodies. This new concept of a quantitative antibody detection system allows test kits to be set up for fast diagnosis of infectious diseases. To develop a quick and homogeneous assay for the detection of human immunodeficiency virus (HIV) infection, we have explored two acceptor sites of the bacterial Escherichia coli beta-galactosidase for the accommodation of HIV antigenic peptides. Two overlapping epitopes (namely P1 and P2) from the gp41 envelope glycoprotein, contained in different sized peptides, were inserted in the vicinity of the enzyme active site to generate a set of hybrid, enzymatically active beta-galactosidases. Regulable enzymes of different responsiveness to monoclonal antibody binding were generated with both acceptor sites tested. These biosensors were also sensitive to immune sera from HIV-infected patients. Modeling data provide insight into the structural modifications in the vicinity of the active site induced by peptide insertion that strongly affect the responsiveness of the engineered proteins through different parameters of their catalytic properties.

Clinicopathological characterization of an HIV-2-infected individual with two clonally unrelated primary lymphomas

Human immunodeficiency virus 2 (HIV-2) is endemic in West Africa and is a causative agent of the acquired immunodeficiency syndrome. Only a small number of HIV-2-infected patients have been described in detail. Non-Hodgkin's lymphoma (NHL) is the second most common neoplasm occurring in HIV-1-infected patients, but its incidence seems to be lower in HIV-2-infected individuals. We report an HIV-2-infected patient from Cape Verde (West Africa) with separate and distinct systemic and primary central nervous system large B-cell lymphomas and review the findings of cases of HIV-2-associated lymphomas reported in the literature. Different clonal rearrangements of the immunoglobulin heavy chain gene could be detected in the two lymphomas of our patient by polymerase chain reaction and sequence analysis. These data indicate the presence of two clonally unrelated large B-cell lymphomas in the same patient, which is an unusual finding. Neither Epstein-Barr virus nor human herpesvirus 8 could be detected in the tumor tissues or the cerebrospinal fluid. HIV-2 infection should be considered in patients with NHL, especially in those from West Africa.

Detection of human immunodeficiency virus type 1 and type 2 in the female genital tract: implications for the understanding of virus transmission

Risk of perinatal or female to male sexual transmission of HIV is likely to be associated with whether, and at what concentration, the virus is present in the cervical and vaginal secretions of the HIV-infected woman. Examining correlates of cervical and vaginal HIV shedding is, therefore, essential for the development of strategies to interrupt HIV transmission. This article presents the rationale for using detection of HIV in the female genital tract as a marker of infectivity, and briefly describes methods for detecting HIV-1 and HIV-2 in cervical or vaginal fluids. Findings from studies incorporating the measurement of HIV in the female genital tract are reviewed, placing particular emphasis on issues relevant to epidemiological studies of HIV transmission.

The envelope glycoprotein of human immunodeficiency virus type 2 enhances viral particle release: a Vpu-like factor?

The Vpu protein is a human immunodeficiency virus type 1 (HIV-1)-specific accessory protein that is required for the efficient release of viral particles from infected cells. Even though HIV-2 does not encode Vpu, we found that this virus is nevertheless capable of efficiently releasing virus particles. In fact, the rate of virus release from HeLa cells transfected with a full-length molecular clone of HIV-2, ROD10, was comparable to that observed for the vpu+ HIV-1 NL4-3 isolate and was not further enhanced by expression of Vpu in trans. However, consistent with previous observations showing that HIV-2 particle release is Vpu responsive in the context of HIV-1/HIV-2 chimeric constructs; exchanging the gag-pol region of NL4-3 with the corresponding region from pROD10 rendered the resulting chimeric virus Vpu responsive. Our finding that the responsiveness of HIV-2 particle release to Vpu is context dependent suggested the presence of a Vpu-like factor(s) encoded by HIV-2. Using chimeric proviruses encoding HIV-2 gag and pol in the context of the HIV-1 provirus that were coexpressed with subgenomic HIV-2 constructs, we found that the HIV-2 envelope glycoprotein had the ability to enhance HIV-2 particle release with an efficiency comparable to that of the HIV-1 Vpu protein. Conversely, inactivation of the HIV-2 env gene in the original ROD10 clone resulted in a decrease in the rate of viral particle release to a level that was comparable to that of Vpu-deficient HIV-1 isolates. Providing the wild-type envelope in trans rescued the particle release defect of the ROD10 envelope mutant. Thus, unlike HIV-1, which encodes two separate proteins to regulate virus release or to mediate viral entry, the HIV-2 Env protein has evolved to perform both functions.