Differences in HIV replication in CD4+ lymphocytes are not related to beta-chemokine production

The CD8+ T Cell Noncytotoxic Antiviral Responses

The CD8+ T cell noncytotoxic antiviral response (CNAR) was discovered during studies of asymptomatic HIV-infected subjects more than 30 years ago. In contrast to CD8+ T cell cytotoxic lymphocyte (CTL) activity, CNAR suppresses HIV replication without target cell killing. This activity has characteristics of innate immunity: it acts on all retroviruses and thus is neither epitope specific nor HLA restricted. The HIV-associated CNAR does not affect other virus families. It is mediated, at least in part, by a CD8+ T cell antiviral factor (CAF) that blocks HIV transcription. A variety of assays used to measure CNAR/CAF and the effects on other retrovirus infections are described. Notably, CD8+ T cell noncytotoxic antiviral responses have now been observed with other virus families but are mediated by different cytokines. Characterizing the protein structure of CAF has been challenging despite many biologic, immunologic, and molecular studies. It represents a low-abundance protein that may be identified by future next-generation sequencing approaches. Since CNAR/CAF is a natural noncytotoxic activity, it could provide promising strategies for HIV/AIDS therapy, cure, and prevention.

Pre-infection transcript levels of FAM26F in peripheral blood mononuclear cells inform about overall plasma viral load in acute and post-acute phase after simian immunodeficiency virus infection

CD8⁺ cells from simian immunodeficiency virus (SIV)-infected long-term non-progressors and some uninfected macaques can suppress viral replication in vitro without killing the infected cells. The aim of this study was to identify factors responsible for non-cytolytic viral suppression by transcriptional profiling and to investigate their potential impact on SIV replication. Results of microarray experiments and further validation with cells from infected and uninfected macaques revealed that FAM26F RNA levels distinguished CD8⁺ cells of controllers and non-controllers (P=0.001). However, FAM26F was also expressed in CD4⁺ T-cells and B-cells. FAM26F expression increased in lymphocytes after in vitro IFN-γ treatment on average 40-fold, and ex vivo FAM26F RNA levels in peripheral blood mononuclear cells correlated with plasma IFN-γ but not with IFN-α. Baseline FAM26F expression appeared to be stable for months, albeit the individual expression levels varied up to tenfold. Investigating its role in SIV-infection revealed that FAM26F was upregulated after infection (P<0.0008), but did not directly correlate with viral load in contrast to MX1 and CXCL10. However, pre-infection levels of FAM26F correlated inversely with overall plasma viral load (AUC) during the acute and post-acute phases of infection (e.g. AUC weeks post infection 0–8; no AIDS vaccine: P<0.0001, Spearman rank correlation coefficient (rs)=−0.89, n=16; immunized with an AIDS vaccine: P=0.033, rs=−0.43; n=25). FAM26F transcript levels prior to infection can provide information about the pace and strength of the antiviral immune response during the early stage of infection. FAM26F expression represented, in our experiments, one of the earliest prognostic markers, and could supplement major histocompatibility complex (MHC)-typing to predict disease progression before SIV-infection.

Development of a contemporary globally diverse HIV viral panel by the EQAPOL program

The significant diversity among HIV-1 variants poses serious challenges for vaccine development and for developing sensitive assays for screening, surveillance, diagnosis, and clinical management. Recognizing a need to develop a panel of HIV representing the current genetic and geographic diversity NIH/NIAID contracted the External Quality Assurance Program Oversight Laboratory (EQAPOL) to isolate, characterize and establish panels of HIV-1 strains representing global diverse subtypes and circulating recombinant forms (CRFs), and to make them available to the research community. HIV-positive plasma specimens and previously established isolates were collected through a variety of collaborations with a preference for samples from acutely/recently infected persons. Source specimens were cultured to high-titer/high-volume using well-characterized cryopreserved PBMCs from National y donors. Panel samples were stored as neat culture supernatant or diluted into defibrinated plasma. Characterization for the final expanded virus stocks included viral load, p24 antigen, infectivity (TCID), sterility, coreceptor usage, and near full-length genome sequencing. Viruses are made available to approved, interested laboratories using an online ordering application. The current EQAPOL Viral Diversity panel includes 100 viral specimens representing 6 subtypes (A, B, C, D, F, and G), 2 sub-subtypes (F1 and F2), 7 CRFs (01, 02, 04, 14, 22, 24, and 47), 19 URFs and 3 group O viruses from 22 countries. The EQAPOL Viral Diversity panel is an invaluable collection of well-characterized reagents that are available to the scientific community, including researchers, epidemiologists, and commercial manufacturers of diagnostics and pharmaceuticals to support HIV research, as well as diagnostic and vaccine development.

Impact of highly active antiretroviral treatment on expression of HIV-1 coreceptors and ligand levels in peripheral blood from HIV-1 infected patients in China

OBJECTIVE

Coreceptors are important for HIV-1 entry into target cells and disease progression. The impact of HIV-1 and highly active antiretroviral treatment (HAART) on coreceptor expression has been little studied.

METHODS

Expression of C-C chemokine receptor (CCR) 5 and C-X-C chemokine receptor (CXCR) 4 on CD4+ and CD8 + T cells was compared in HIV-1-infected individuals who had/had not received HAART, and in healthy controls. Relationships between coreceptors and their chemokine ligands were studied.

RESULTS

This study included 23 controls and 88 HIV-1-infected individuals, 35 of whom were HAART naïve. Percentages of CCR5 and CXCR4+ CD8 + T cells were higher, and CXCR4+ CD4 + T cells were lower, in patients than in controls. Patients receiving HAART showed a higher percentage of CCR5 expression on CD4 + T cells compared with HAART-naïve patients. HIV-infected individuals had significantly increased levels of peripheral ligands for coreceptors, compared with controls; levels were significantly higher in those receiving HAART compared with the HAART-naïve.

CONCLUSIONS

HIV-1 infection increases coreceptor expression on T cells; HAART increases CCR5 expression further and decreases CXCR4 expression, reversing the switch from CCR5 to CXCR4, which was significant for CD4 + T.

Lack of good correlation of serum CC-chemokine levels with human immunodeficiency virus-1 disease stage and response to treatment

Three CC-chemokines-MIP-1alpha (CCL3), MIP-1beta (CCL4), and RANTES (CCL5)-are natural ligands for the human immunodeficiency virus-1 (HIV-1) coreceptor CCR5. To determine correlations between CC-chemokines and HIV-1 disease stage or response to treatment, we examined serum levels of MIP-1alpha, MIP-1beta, and RANTES in 60 infected patients during 18 months while they were taking highly active antiretroviral therapy (HAART). Our results demonstrate that serum levels of MIP-1alpha and RANTES were increased in HIV-1-infected individuals compared with those in healthy controls. We found no significant differences among 4 clinical stages of HIV-1 infection in the serum levels of three CC-chemokines. Longitudinal HAART analyses revealed a pronounced decline in serum MIP-1alpha levels over time. We found no difference in this decline between HAART responders and nonresponders. These findings indicate that production of MIP-1alpha and RANTES changes during HIV-1 infection and treatment; however, our results suggest that serum levels of CC-chemokines should not be used as biomarkers for HIV-1 disease stage or response to treatment.

Herpesvirus saimiri-immortalized human lymphocytes: novel hosts for analyzing HIV type 1 in vitro neutralization

Herpesvirus saimiri-immortalized CD4(+) T lymphocytes (HVS T cells) are activated memory cells that support efficient replication of primary R5 strains of HIV-1, which predominate in virus transmission. Being continuous, they are phenotypically more stable and technically less demanding than peripheral blood mononuclear cells (PBMCs). Here we present the first report using HVS T cells to assay HIV-1 neutralization in vitro. Neutralization sensitivities of paired viruses isolated from individuals in both HVS T cells (CN-2 cells) and PBMCs were similar, with homologous and heterologous plasma/sera in both CN-2- and PBMC-based assays. Analysis of V3 loop and CD4-binding site (CD4-BS) sequences showed that changes present in CN-2 isolates were neither more numerous nor more significant than those selected in their PBMC counterparts. Neutralization profiles of CN-2/PBMC virus pairs were similar again when V3- and CD4-binding site (BS)-specific monoclonal antibodies, whose mapped epitopes were conserved or of similar sequence in the virus pairs, were tested. Unlike other T cell line isolates, CN-2 isolates were not more sensitive to neutralization than their PBMC counterparts. We also show that HVS T cells do not appear to exert significant biological selection pressures on primary isolates. Paired viruses have a similar phenotype with respect to syncytium formation, cell tropism, and coreceptor usage. Thus CN-2 cells are suitable hosts for assaying neutralization and could be useful in standardizing neutralization assays performed in different laboratories.

Selective regulation of human immunodeficiency virus-infected CD4(+) lymphocytes by a synthetic immunomodulator leads to potent virus suppression in vitro and in hu-PBL-SCID mice

We have previously observed that the synthetic immunomodulator Murabutide inhibits human immunodeficiency virus type 1 (HIV-1) replication at multiple levels in macrophages and dendritic cells. The present study was designed to profile the activity of Murabutide on CD8-depleted phytohemagglutinin-activated lymphocytes from HIV-1-infected subjects and on the outcome of HIV-1 infection in severe combined immunodeficiency mice reconstituted with human peripheral blood leukocytes (hu-PBL-SCID mice). Maintaining cultures of CD8-depleted blasts from 36 patients in the presence of Murabutide produced dramatically reduced levels of viral p24 protein in the supernatants. This activity correlated with reduced viral transcripts and proviral DNA, was evident in cultures harboring R5, X4-R5, or X4 HIV-1 isolates, was not linked to inhibition of cellular DNA synthesis, and did not correlate with beta-chemokine release. Moreover, c-myc mRNA expression was down-regulated in Murabutide-treated cells, suggesting potential interference of the immunomodulator with the nuclear transport of viral preintegration complexes. On the other hand, daily treatment of HIV-1-infected hu-PBL-SCID mice with Murabutide significantly reduced the viral loads in plasma and the proviral DNA content in human peritoneal cells. These results are the first to demonstrate that a clinically acceptable synthetic immunomodulator with an ability to enhance the host's nonspecific immune defense mechanisms against infections can directly regulate cellular factors in infected lymphocytes, leading to controlled HIV-1 replication.

Human immunodeficiency virus type-1 and chemokines: beyond competition for common cellular receptors

The chemokines and their receptors have been receiving exceptional attention in recent years following the discoveries that some chemokines could specifically block human immunodeficiency virus type 1 (HIV-1) infection and that certain chemokine receptors were the long-sought coreceptors which, along with CD4, are required for the productive entry of HIV-1 and HIV-2 isolates. Several chemokine receptors or orphan chemokine receptor-like molecules can support the entry of various viral strains, but the clinical significance of the CXCR4 and CCR5 coreceptors appear to overshadow a critical role for any of the other coreceptors and all HIV-1 and HIV-2 strains best employ one or both of these coreceptors. Binding of the HIV-1 envelope glycoprotein gp120 subunit to CD4 and/or an appropriate chemokine receptor triggers conformational changes in the envelope glycoprotein oligomer that allow it to facilitate the fusion of the viral and host cell membranes. During these interactions, gp120 appears to be capable of inducing a variety of signaling events, all of which are still not defined in detail. In addition, the more recently observed dichotomous effects, of both inhibition and enhancement, that chemokines and their receptor signaling events elicit on the HIV-1 entry and replication processes has once again highlighted the intricate and complex balance of factors that govern the pathogenic process. Here, we will review and discuss these new observations summarizing the potential significance these processes may have in HIV-1 infection. Understanding the complexities and significance of the signaling processes that the chemokines and viral products induce may substantially enhance our understanding of HIV-1 pathogenesis, and perhaps facilitate the discovery of new ways for the prevention and treatment of HIV-1 disease.

Enhanced replication of M-tropic HIV-1 strains in Herpesvirus saimiri immortalised T-cells which express CCR5

A better characterisation of mononuclear cell-tropic (M-tropic) HIV-1 is central to disease control as these viruses predominate in disease transmission. M-tropic viruses do not replicate in conventional T-cell lines, and virus titres obtained in peripheral blood mononuclear cells (PBMC) are low. Human T-lymphocytes which have been immortalised by Herpesvirus saimiri strain C488 (HVS T-cells) are highly permissive to the replication of T-cell tropic strains of HIV. This study aimed to determine if HVS T-cells support replication of M-tropic HIV isolates that have not been adapted to conventional T-cell lines. A panel of PBMC low passage/primary field isolates and their molecular clones was used. Results show that infection in HVS T-cells was longer lived than in PBMC. In terms of peak virus titre and duration of productive infection, the two HVS T-cell lines studied were superior to PBMC, and one supported enhanced replication of all M-tropic isolates. This is important for generating M-tropic virus pools of sufficient titre for further biological studies such as virus neutralisation, co receptor usage and testing of antivirals. Phenotypic analysis showed that HVS T-cells are CD4+-activated memory cells expressing both CXCR-4 and CCR5 co receptors. Thus, HVS immortalisation appears to select for the T-cell subset targeted by HIV-1 in vivo.

Differential effects of human immunodeficiency virus isolates on beta-chemokine and gamma interferon production and on cell proliferation

All human immunodeficiency virus (HIV) isolates can grow readily in primary CD4(+) T cells, but they can be distinguished by their ability to replicate in macrophages and established T-cell lines. The macrophage-tropic viruses are generally non-syncytium inducing (NSI), whereas the T-cell-line-tropic viruses are syncytium inducing (SI) in cultured cells. We now demonstrate that infection of CD4(+) T cells by NSI and SI viruses shows a differential effect on production of beta-chemokines and gamma interferon. Infection by NSI viruses increased production of MIP-1alpha, MIP-1beta, and gamma interferon, whereas infection by SI viruses had no effect or decreased production of these cytokines. Production of RANTES was slightly increased during infection by both virus phenotypes. This differential effect of NSI and SI viruses was observed at the level of beta-chemokine mRNA as well as at the level of protein expression. Infection by NSI viruses also increased CD4(+) cell proliferation. These results may have relevance for a differential role of HIV strains in AIDS pathogenesis.