Dendritic cells are less susceptible to human immunodeficiency virus type 2 (HIV-2) infection than to HIV-1 infection

Human immunodeficiency virus type 1 (HIV-1) infection of dendritic cells (DCs) has been documented in vivo and may be an important contributor to HIV-1 transmission and pathogenesis. HIV-1-specific CD4⁺ T cells respond to HIV antigens presented by HIV-1-infected DCs and in this process become infected, thereby providing a mechanism through which HIV-1-specific CD4⁺ T cells could become preferentially infected in vivo. HIV-2 disease is attenuated with respect to HIV-1 disease, and host immune responses are thought to be contributory. Here we investigated the susceptibility of primary myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) to infection by HIV-2. We found that neither CCR5-tropic primary HIV-2 isolates nor a lab-adapted CXCR4-tropic HIV-2 strain could efficiently infect mDCs or pDCs, though these viruses could infect primary CD4⁺ T cells in vitro. HIV-2-exposed mDCs were also incapable of transferring virus to autologous CD4⁺ T cells. Despite this, we found that HIV-2-specific CD4⁺ T cells contained more viral DNA than memory CD4⁺ T cells of other specificities in vivo. These data suggest that either infection of DCs is not an important contributor to infection of HIV-2-specific CD4⁺ T cells in vivo or that infection of DCs by HIV-2 occurs at a level that is undetectable in vitro. The frequent carriage of HIV-2 DNA within HIV-2-specific CD4⁺ T cells, however, does not appear to be incompatible with preserved numbers and functionality of HIV-2-specific CD4⁺ T cells in vivo, suggesting that additional mechanisms contribute to maintenance of HIV-2-specific CD4⁺ T-cell help in vivo.     

Dating the Age of the SIV Lineages That Gave Rise to HIV-1 and HIV-2

Great strides have been made in understanding the evolutionary history of simian immunodeficiency virus (SIV) and the zoonoses that gave rise to HIV-1 and HIV-2. What remains unknown is how long these SIVs had been circulating in non-human primates before the transmissions to humans. Here, we use relaxed molecular clock dating techniques to estimate the time of most recent common ancestor for the SIVs infecting chimpanzees and sooty mangabeys, the reservoirs of HIV-1 and HIV-2, respectively. The date of the most recent common ancestor of SIV in chimpanzees is estimated to be 1492 (1266–1685), and the date in sooty mangabeys is estimated to be 1809 (1729–1875). Notably, we demonstrate that SIV sequences sampled from sooty mangabeys possess sufficient clock-like signal to calibrate a molecular clock; despite the differences in host biology and viral dynamics, the rate of evolution of SIV in sooty mangabeys is indistinguishable from that of its human counterpart, HIV-2. We also estimate the ages of the HIV-2 human-to-human transmissible lineages and provide the first age estimate for HIV-1 group N at 1963 (1948–1977). Comparisons between the SIV most recent common ancestor dates and those of the HIV lineages suggest a difference on the order of only hundreds of years. Our results suggest either that SIV is a surprisingly young lentiviral lineage or that SIV and, perhaps, HIV dating estimates are seriously compromised by unaccounted-for biases.     

Kinetic studies of HIV-1 and HIV-2 envelope glycoprotein-mediated fusion

Background

Human immunodeficiency virus (HIV) enters target cells by a membrane fusion process that involves a series of sequential interactions between its envelope glycoproteins, the CD4 receptor and CXCR4/CCR5 coreceptors. CD4 molecules are expressed at the cell surface of lymphocytes and monocytes mainly as monomers, but basal levels of CD4 dimers are also present at the cell surface of these cells. Previous evidence indicates that the membrane distal and proximal extracellular domains of CD4, respectively D1 and D4, are involved in receptor dimerization.

Results

Here, we have used A201 cell lines expressing two CD4 mutants, CD4-E91K, E92K (D1 mutant) and CD4-Q344E (D4 mutant), harboring dimerization defects to analyze the role of CD4 dimerization in HIV-1 entry. Using entry assays based on β-lactamase-Vpr or luciferase reporter activities, as well as virus encoding envelope glycoproteins derived from primary or laboratory-adapted strains, we obtained evidence suggesting an association between disruption of CD4 dimerization and increased viral entry efficiency.

Conclusion

Taken together, our results suggest that monomeric forms of CD4 are preferentially used by HIV-1 to gain entry into target cells, thus implying that the dimer/monomer ratio at the cell surface of HIV-1 target cells may modulate the efficiency of HIV-1 entry.     

应用斑点金免疫渗滤试验快速同步检测抗HIV-1,HIV-2 IgG抗体

应用斑点金免疫渗滤试验(dotimmunogoldfiltration assay,DIGFA)建立了一种同步快速检测四种抗HIV-1/2IgG抗体的HIV诊断试纸.通过基因工程技术在大肠杆菌中表达了5种HIV抗原蛋白片段(P24,GP41,GP36,GP120V3,GP120C).这5种抗原蛋白首先被固定在硝酸纤维素膜上,然后滴加待测血清,其中的病毒抗体通过免疫反应与抗原结合,再加胶体金标记的葡萄球菌蛋白A(SPA),待其渗过膜片后,洗涤,即可形成肉眼可见的红色斑点.用已确证的21份HIV阳性血清(其中包括1份HIV-1标准阳性血清和1份HIV-2标准阳性血清)和30份阴性血清进行了试验,结果表明该快速检测方法与ELISA方法无显著差异.该检测方法不需任何仪器,仅凭肉眼即可判定结果,整个检测过程不超过5分钟.与传统的的ELISA法相比,具有方便快速,成本低廉,应用范围广等优点.同时,此HIV快速诊断试纸可以同步检测并区分针对HIV-1和HIV-2感染的不同检测标志物(抗P24、GP41、GP120和GP36抗体),这对提高快速检测的灵敏度和准确性,以及对判断HIV感染者是否临近或已进入AIDS期有着较高的应用价值.     

Greater CD8+ TCR heterogeneity and functional flexibility in HIV-2 compared to HIV-1 infection

Virus-specific CD8(+) T cells are known to play an important role in the control of HIV infection. In this study we investigated whether there may be qualitative differences in the CD8(+) T cell response in HIV-1- and HIV-2-infected individuals that contribute to the relatively efficient control of the latter infection. A molecular comparison of global TCR heterogeneity showed a more oligoclonal pattern of CD8 cells in HIV-1- than HIV-2-infected patients. This was reflected in restricted and conserved TCR usage by CD8(+) T cells recognizing individual HLA-A2- and HLA-B57-restricted viral epitopes in HIV-1, with limited plasticity in their response to amino acid substitutions within these epitopes. The more diverse TCR usage observed for HIV-2-specific CD8(+) T cells was associated with an enhanced potential for CD8 expansion and IFN-gamma production on cross-recognition of variant epitopes. Our data suggest a mechanism that could account for any possible cross-protection that may be mediated by HIV-2-specific CD8(+) T cells against HIV-1 infection. Furthermore, they have implications for HIV vaccine development, demonstrating an association between a polyclonal, virus-specific CD8(+) T cell response and an enhanced capacity to tolerate substitutions within T cell epitopes.     

Antibody-mediated enhancement of HIV-1 and HIV-2 production from BST-2/tetherin-positive cells

BST-2/CD317/HM1.24/tetherin is a B-cell antigen overexpressed on the surface of myeloma cell lines and on neoplastic plasma cells of patients with multiple myeloma. Antibodies to BST-2 are in clinical trial for the treatment of multiple myeloma and are considered for the treatment of solid tumors with high BST-2 antigen levels. Functionally, BST-2 restricts the secretion of retroviruses, including human immunodeficiency virus type 1, as well as members of the herpesvirus, filovirus, and arenavirus families, presumably by tethering nascent virions to the cell surface. Here we report that BST-2 antibody treatment facilitates virus release from BST-2(+) cells by interfering with the tethering activity of BST-2. BST-2 antibodies were unable to release already tethered virions and were most effective when added early during virus production. BST-2 antibody treatment did not affect BST-2 dimerization and did not reduce the cell surface expression of BST-2. Interestingly, BST-2 antibody treatment reduced the nonspecific shedding of BST-2 and limited the encapsidation of BST-2 into virions. Finally, flotation analyses indicate that BST-2 antibodies affect the distribution of BST-2 within membrane rafts. Our data suggest that BST-2 antibody treatment may enhance virus release by inducing a redistribution of BST-2 at the cell surface, thus preventing it from accumulating at the sites of virus budding.     

Plasma HIV-2 RNA According to CD4 Count Strata among HIV-2-Infected Adults in the IeDEA West Africa Collaboration

Background

Plasma HIV-1 RNA monitoring is one of the standard tests for the management of HIV-1 infection. While HIV-1 RNA can be quantified using several commercial tests, no test has been commercialized for HIV-2 RNA quantification. We studied the relationship between plasma HIV-2 viral load (VL) and CD4 count in West African patients who were either receiving antiretroviral therapy (ART) or treatment-naïve.

Method

A cross sectional survey was conducted among HIV-2-infected individuals followed in three countries in West Africa from March to December 2012. All HIV-2 infected-patients who attended one of the participating clinics were proposed a plasma HIV-2 viral load measurement. HIV-2 RNA was quantified using the new ultrasensitive in-house real-time PCR assay with a detection threshold of 10 copies/ mL (cps/mL).

Results

A total of 351 HIV-2-infected individuals participated in this study, of whom 131 (37.3%) were treatment naïve and 220 (62.7%) had initiated ART. Among treatment-naïve patients, 60 (46.5%) had undetectable plasma HIV-2 viral load (<10 cps/mL), it was detectable between 10-100 cps/mL in 35.8%, between 100-1000 cps/mL in 11.7% and >1000 cps/mL in 6.0% of the patients. Most of the treatment-naïve patients (70.2%) had CD4-T cell count ≥500 cells/mm³ and 43 (46.7%) of these patients had a detectable VL (≥10 cps/mL). Among the 220 patients receiving ART, the median CD4-T cell count rose from 231 to 393 cells/mm³ (IQR [259-561]) after a median follow-up duration of 38 months and 145 (66.0%) patients had CD4-T cell count ≤ 500 cells/mm³ with a median viral load of 10 cps/mL (IQR [10-33]). Seventy five (34.0%) patients had CD4-T cell count ≥ 500 cells/mm³, among them 14 (18.7%) had a VL between 10-100 cps/mL and 2 (2.6%) had VL >100 cps/mL.

Conclusion

This study suggests that the combination of CD4-T cell count and ultrasensitive HIV-2 viral load quantification with a threshold of 10 cps/mL, could improve ART initiation among treatment naïve HIV-2-infected patients and the monitoring of ART response among patients receiving treatment.     

应用斑点金免疫渗滤试验快速同步检测抗HIV-1，HIV-2 IgG抗体

应用斑点金免疫渗滤试验(dotimmunogoldfiltrationassay,DIGFA)建立了一种同步快速检测四种抗HIV-1/2IgG抗体的HIV诊断试纸。通过基因工程技术在大肠杆菌中表达了5种HIV抗原蛋白片段(P24,GP41,GP36,GP120V3,GP120C)。这5种抗原蛋白首先被固定在硝酸纤维素膜上,然后滴加待测血清,其中的病毒抗体通过免疫反应与抗原结合,再加胶体金标记的葡萄球菌蛋白A(SPA),待其渗过膜片后,洗涤,即可形成肉眼可见的红色斑点。用已确证的21份HIV阳性血清(其中包括1份HIV-1标准阳性血清和1份HIV-2标准阳性血清)和30份阴性血清进行了试验,结果表明该快速检测方法与ELISA方法无显著差异。该检测方法不需任何仪器,仅凭肉眼即可判定结果,整个检测过程不超过5分钟。与传统的的ELISA法相比,具有方便快速,成本低廉,应用范围广等优点。同时,此HIV快速诊断试纸可以同步检测并区分针对HIV-1和HIV-2感染的不同检测标志物(抗P24、GP41、GP120和GP36抗体),这对提高快速检测的灵敏度和准确性,以及对判断HIV感染者是否临近或已进入AIDS期有着较高的应用价值。     

Characteristics of HIV-2 and HIV-1/HIV-2 Dually Seropositive Adults in West Africa Presenting for Care and Antiretroviral Therapy: The IeDEA-West Africa HIV-2 Cohort Study

Background

HIV-2 is endemic in West Africa. There is a lack of evidence-based guidelines on the diagnosis, management and antiretroviral therapy (ART) for HIV-2 or HIV-1/HIV-2 dual infections. Because of these issues, we designed a West African collaborative cohort for HIV-2 infection within the framework of the International epidemiological Databases to Evaluate AIDS (IeDEA).

Methods

We collected data on all HIV-2 and HIV-1/HIV-2 dually seropositive patients (both ARV-naive and starting ART) and followed-up in clinical centres in the IeDEA-WA network including a total of 13 clinics in five countries: Benin, Burkina-Faso Côte d’Ivoire, Mali, and Senegal, in the West Africa region.

Results

Data was merged for 1,754 patients (56% female), including 1,021 HIV-2 infected patients (551 on ART) and 733 dually seropositive for both HIV-1 and HIV 2 (463 on ART). At ART initiation, the median age of HIV-2 patients was 45.3 years, IQR: (38.3–51.7) and 42.4 years, IQR (37.0–47.3) for dually seropositive patients (p = 0.048). Overall, 16.7% of HIV-2 patients on ART had an advanced clinical stage (WHO IV or CDC-C). The median CD4 count at the ART initiation is 166 cells/mm³, IQR (83–247) among HIV-2 infected patients and 146 cells/mm³, IQR (55–249) among dually seropositive patients. Overall, in ART-treated patients, the CD4 count increased 126 cells/mm³ after 24 months on ART for HIV-2 patients and 169 cells/mm³ for dually seropositive patients. Of 551 HIV-2 patients on ART, 5.8% died and 10.2% were lost to follow-up during the median time on ART of 2.4 years, IQR (0.7–4.3).

Conclusions

This large multi-country study of HIV-2 and HIV-1/HIV-2 dual infection in West Africa suggests that routine clinical care is less than optimal and that management and treatment of HIV-2 could be further informed by ongoing studies and randomized clinical trials in this population.     

Demonstration of cross-reactive antibodies able to elicit lysis of both HIV-1- and HIV-2-infected cells.

A total of 100% of sera from a large number of HIV-1-infected patients contained antibodies able to elicit Antibody-dependent cellular cytotoxicity lysis of cells infected with the HIV-1 isolates IIIB or RF. Levels of activity could not be correlated with activities in ELISA or neutralizing antibody assays nor with the clinical status of the patients. Surprisingly, 8 of 156 patients sera could additionally elicit lysis of HIV-2-infected cells, and cold target competition assays demonstrated that the cross-reactivity was apparently mediated via recognition of common epitope(s) expressed on the surface of cells infected with either group of HIV. The ADCC mechanism was shown to be mediated by a CD16+ lymphocyte. This demonstration of an effector mechanism able to attack and eliminate cells infected with a wide range of HIV strains has obvious implications for development of putative vaccines.     

Hydrolysis of synthetic chromogenic substrates by HIV-1 and HIV-2 proteinases

Kinetic constants (Km,Kcat) are derived for the hydrolysis of a number of chromogenic peptide substrates by the aspartic proteinase from HIV-2. The effect of systematic replacement of the P2 residue on substrate hydrolysis by HIV-1 and HIV-2 proteinases is examined.     

BI-2 destabilizes HIV-1 cores during infection and Prevents Binding of CPSF6 to the HIV-1 Capsid

Background

The recently discovered small-molecule BI-2 potently blocks HIV-1 infection. BI-2 binds to the N-terminal domain of HIV-1 capsid. BI-2 utilizes the same capsid pocket used by the small molecule PF74. Although both drugs bind to the same pocket, it has been proposed that BI-2 uses a different mechanism to block HIV-1 infection when compared to PF74.

Findings

This work demonstrates that BI-2 destabilizes the HIV-1 core during infection, and prevents the binding of the cellular factor CPSF6 to the HIV-1 core.

Conclusions

Overall this short-form paper suggests that BI-2 is using a similar mechanism to the one used by PF74 to block HIV-1 infection.

     

Bifunctional recombinant fusion proteins for rapid detection of antibodies to both HIV-1 and HIV-2 in whole blood

Background  

Availability of accurate diagnostic tests has been helpful in curtailing the spread of HIV infection. Among these, simple, point of care, inexpensive tests which require only a drop of blood from finger-prick and give reliable results within minutes are a must for expansion of testing services and for reaching mobile and marginalised populations. Such tests will not only be a boon for the infrastructure-starved developing and underdeveloped countries but will also be extremely useful in developed countries where post-testing compliance is a major problem. Our laboratory has been involved in developing reagents for heamagglutination-based rapid detection of antibodies to HIV in whole blood using recombinant molecules specific for either HIV-1 or HIV-2. Since it is not required of a screening test to differentially detect HIV and HIV-2, it would useful to create a single molecule capable of simultaneous detection of both HIV-1 and HIV-2 in a drop of blood.     

Cytopathicity of human immunodeficiency virus type 2 (HIV-2) in human lymphoid tissue is coreceptor dependent and comparable to that of HIV-1

Epidemiological studies have shown that human immunodeficiency virus type 2 (HIV-2) is markedly less pathogenic than HIV-1 in vivo. Individuals infected with HIV-2 exhibit a remarkably slow rate of disease development, and these clinical properties have been attributed presumptively to an "attenuated" phenotype of HIV-2 itself. Here, we investigated the impact of coreceptor usage on the cytopathicity of HIV-2 and compared its pathogenic potential with that of HIV-1 in a unique human lymphoid histoculture model. We found that HIV-2 strains, as well as closely related simian immunodeficiency viruses (SIV), displayed mildly or highly aggressive cytopathic phenotypes depending on their abilities to use the coreceptor CCR5 or CXCR4, respectively. A side-by-side comparison of primary X4 HIV-1 and HIV-2 strains revealed similar, high degrees of cytopathicity induced by both HIV types. Furthermore, we found that HIV-2 coreceptor specificity for CCR5 and CXCR4 determined the target cell population for T-cell depletion in lymphoid tissue. Finally, utilization of the alternate coreceptors BOB and Bonzo did not significantly increase the cytopathic properties of HIV-2. These findings demonstrate that coreceptor preference is a key regulator of target cell specificity and the cytopathic potential of HIV-2, with indistinguishable rules compared with HIV-1. Moreover, HIV-2 strains are not characterized by an intrinsically lower cytopathicity than HIV-1 strains. Therefore, direct cytopathic potential per se does not explain the unique behavior of HIV-2 in people, highlighting that other unknown factors need to be elucidated as the basis for their lesser virulence in vivo.