Molecular mechanisms involved in HIV latency and implications for HIV treatment and eradication

The aim of this presentation is to review the molecular mechanisms necessary for the establishment of HIV-1 latency, their relationship with different cellular and anatomic reservoirs, as well as the current treatment strategies targeting viral persistence in latent reservoirs, their main limitations and future perspectives.S

PKC-omerga and HIV-1 transcriptional regulator Tat co-exist at the LTR promoter in CD4⁺ T cells

PKCtheta is essential for the activation of CD4+ T cells. Upon TCR/CD28 stimulation, PKCtheta is phosphorylated and migrates to the immunological synapse, inducing the activation of cellular transcription factors such as NF-kB and kinases as ERK that are critical for HIV-1 replication. We previously demonstrated that PKCtheta is also necessary for HIV-1 replication but the precise mechanism is unknown. Efficient HIV-1 transcription and elongation is absolutely dependent on the synergy between NF-kB and the viral regulator Tat. Tat exerts its function by binding a RNA stem-loop structure proximal to the viral mRNA cap site termed TAR. Besides, due to its effect on cellular metabolic pathways, Tat causes profound changes in infected CD4+ T cells such as the activation of NF-kB and ERK. We hypothesized that the aberrant up-regulation of Tat-mediated activation of NF-kB and ERK occurred through PKCtheta signaling. In fact, Jurkat TetOff cells with stable and doxycycline-repressible expression of Tat (Jurkat-Tat) expressed high levels of mRNA for PKCtheta. In these cells, PKCtheta located at the plasma membrane was phosphorylated at T538 residue in undivided cells, in the absence of stimulation. Treatment with doxycycline inhibited PKCtheta phosphorylation in Jurkat-Tat, suggesting that Tat expression was directly related to the activation of PKCtheta. Both NF-kB and Ras/Raf/MEK/ERK signaling pathway were significantly activated in Jurkat-Tat cells, and this correlated with high transactivation of HIV-1 LTR promoter. RNA interference for PKCtheta inhibited NF-kB and ERK activity, as well as LTR-mediated transactivation even in the presence of Tat. In addition to Tat-mediated activation of PKCtheta in the cytosol, we demonstrated by sequential ChIP that Tat and PKCtheta coexisted in the same complex bound at the HIV-1 LTR promoter, specifically at the region containing TAR loop. In conclusion, PKCtheta-Tat interaction seemed to be essential for HIV-1 replication in CD4+ T cells and could be used as a therapeutic target

Comprehensive characterization of LEDGF/p75 in a HIV-1-infected patient cohort

BACKGROUND: Lens epithelium derived growth factor/transcriptional co-activator p75 (LEDGF/p75) is an important cellular co-factor for the HIV enzyme integrase. In the present study, we evaluated if genetic variation in the LEDGF/p75 gene and mRNA expression levels might explain differences in HIV disease progression. METHODS: Samples were derived from a therapy-naïve patient cohort from the Ghent University Hospital and from the long-term-non-progressor patient Spanish RIS cohort. A comprehensive genomic scan of the coding region and 3’UTR of LEDGF/p75 was performed using high resolution melting curve analysis and Sanger sequencing to identify single nucleotide polymorphisms (SNPS). In addition, LEDGF/p75 mRNA expression levels were determined from patient PBMCs using RT-qPCR with validated reference genes for normalization. RESULTS: In total 325 patient samples were investigated, of which 291 (90%) of Caucasian and 34 (10%) of African origin, and among which a large group of Elite controllers (n=49) and Viremic controllers (n=62). In these samples, 24 SNPs were analyzed, including 5 in the coding region (2 synonymous and 3 non-synonymous), 17 in the flanking non-coding regions and in the 3’UTR, and two additional tagSNPs as described by Madlala et al. (Aids, 2011) in two South African cohorts. One SNP in the 3’UTR region (rs2737835, n=46) had a higher representation in Caucasian Elite controllers and was correlated with lower LEDGF/p75 mRNA levels (P=0.047) and with a slower CD4 decline (P= 0.042). rs2737828 (n=13) was under-represented in Caucasian HIV patients and linked to lower LEDGF/p75 expression (P=0.013). The presence of intron SNP (rs16933270, n=6) was associated with a slower CD4 decline in African patients (P=0.017), and this CD4 decline was comparable with that of African slow disease progressors. Interestingly, the presence of one tagSNP (rs12339417, n=95) was significantly correlated with a decreased viral load, but in contrast to the results of Madlala et al. (Aids, 2011), this SNP was not correlated with the CD4 slope and neither with LEDGF/p75 mRNA levels. CONCLUSIONS: Although the data of the present investigation was not entirely comparable with the results of Madlala et al. (Aids, 2011), our data supports their hypothesis that host factors influence HIV disease progression. The observed differences between the European and South African cohorts may be of ethnical origin, or due to different infection phases. In the investigated cohorts, two SNPs were associated with lower LEDGF/p75 mRNA expression in Caucasians, and one SNP was associated with slower disease progression in Africans. The significant correlation with the tagSNP (rs12339417) and the decreased viral load is surprising as this was not correlated with a delayed CD4 decline, nor with LEDGF/p75 expression. This might indicate that either conformational changes or factors upstream of mRNA transcription might influence the action of LEDGF/p75 in these HIV patients

Aquatic ecosystems in Byers Peninsula, Livingston Island. An Antarctic Noah’s Ark in a changing world

第6回極域科学シンポジウム[OB] 極域生物圏11月17日（火）　統計数理研究所 セミナー室1（D305

Mechanisms of abrupt loss of virus control in a cohort of previous HIV controllers

Altres ajuts: FIPSE grant 360737-09; AELIX TherapeuticsA few individuals can control HIV infection without the need for antiretroviral treatment and are referred to as HIV controllers. We have studied HIV controllers who suddenly lose this ability and present with high in vivo viral replication and decays in their CD4 + T-cell counts to identify potential immune and virological factors that were responsible for initial virus control. We identify in vitro -determined reductions in the ability of CD8 T cells to suppress viral control and the presence of PD-1-expressing CD8 + T cells with a naive immune phenotype as potential predictors of in vivo loss of virus control. The findings could be important for the clinical management of HIV controller individuals, and it may offer an important tool to anticipate viral rebound in individuals in clinical studies that include combination antiretroviral therapy (cART) treatment interruptions and which, if not treated quickly, could pose a significant risk to the trial participants. Elite and viremic HIV controllers are able to control their HIV infection and maintain undetectable or low-level viremia in the absence of antiretroviral treatment. Despite extensive studies, the immune factors responsible for such exclusive control remain poorly defined. We identified a cohort of 14 HIV controllers that suffered an abrupt loss of HIV control (LoC) to investigate possible mechanisms and virological and immunological events related to the sudden loss of control. The in-depth analysis of these subjects involved the study of cell tropism of circulating virus, evidence for HIV superinfection, cellular immune responses to HIV, as well as an examination of viral adaptation to host immunity by Gag sequencing. Our data demonstrate that a poor capacity of T cells to mediate in vitro viral suppression, even in the context of protective HLA alleles, predicts a loss of viral control. In addition, the data suggest that inefficient viral control may be explained by an increase of CD8 T-cell activation and exhaustion before LoC. Furthermore, we detected a switch from C5- to X4-tropic viruses in 4 individuals after loss of control, suggesting that tropism shift might also contribute to disease progression in HIV controllers. The significantly reduced inhibition of in vitro viral replication and increased expression of activation and exhaustion markers preceding the abrupt loss of viral control may help identify untreated HIV controllers that are at risk of losing control and may offer a useful tool for monitoring individuals during treatment interruption phases in therapeutic vaccine trials. IMPORTANCE A few individuals can control HIV infection without the need for antiretroviral treatment and are referred to as HIV controllers. We have studied HIV controllers who suddenly lose this ability and present with high in vivo viral replication and decays in their CD4 + T-cell counts to identify potential immune and virological factors that were responsible for initial virus control. We identify in vitro -determined reductions in the ability of CD8 T cells to suppress viral control and the presence of PD-1-expressing CD8 + T cells with a naive immune phenotype as potential predictors of in vivo loss of virus control. The findings could be important for the clinical management of HIV controller individuals, and it may offer an important tool to anticipate viral rebound in individuals in clinical studies that include combination antiretroviral therapy (cART) treatment interruptions and which, if not treated quickly, could pose a significant risk to the trial participants

International Network for Comparison of HIV Neutralization Assays: The NeutNet Report II

BACKGROUND: Neutralizing antibodies provide markers for vaccine-induced protective immunity in many viral infections. By analogy, HIV-1 neutralizing antibodies induced by immunization may well predict vaccine effectiveness. Assessment of neutralizing antibodies is therefore of primary importance, but is hampered by the fact that we do not know which assay(s) can provide measures of protective immunity. An international collaboration (NeutNet) involving 18 different laboratories previously compared different assays using monoclonal antibodies (mAbs) and soluble CD4 (Phase I study). METHODS: In the present study (Phase II), polyclonal reagents were evaluated by 13 laboratories. Each laboratory evaluated nine plasmas against an 8 virus panel representing different genetic subtypes and phenotypes. TriMab, a mixture of three mAbs, was used as a positive control allowing comparison of the results with Phase I in a total of nine different assays. The assays used either uncloned virus produced in peripheral blood mononuclear cells (PBMCs) (Virus Infectivity Assays, VIA), or Env (gp160)-pseudotyped viruses (pseudoviruses, PSV) produced in HEK293T cells from molecular clones or from uncloned virus. Target cells included PBMC and genetically engineered cell lines in either single- or multiple-cycle infection format. Infection was quantified by using a range of assay read-outs including extra- or intra-cellular p24 antigen detection, luciferase, beta-galactosidase or green fluorescent protein (GFP) reporter gene expression. FINDINGS: Using TriMab, results of Phase I and Phase II were generally in agreement for six of the eight viruses tested and confirmed that the PSV assay is more sensitive than PBMC (p = 0.014). Comparisons with the polyclonal reagents showed that sensitivities were dependent on both virus and plasma. CONCLUSIONS: Here we further demonstrate clear differences in assay sensitivities that were dependent on both the neutralizing reagent and the virus. Consistent with the Phase I study, we recommend parallel use of PSV and VIA for vaccine evaluation

International Network for Comparison of HIV Neutralization Assays: The NeutNet Report

BACKGROUND: Neutralizing antibody assessments play a central role in human immunodeficiency virus type-1 (HIV-1) vaccine development but it is unclear which assay, or combination of assays, will provide reliable measures of correlates of protection. To address this, an international collaboration (NeutNet) involving 18 independent participants was organized to compare different assays. METHODS: Each laboratory evaluated four neutralizing reagents (TriMab, 447-52D, 4E10, sCD4) at a given range of concentrations against a panel of 11 viruses representing a wide range of genetic subtypes and phenotypes. A total of 16 different assays were compared. The assays utilized either uncloned virus produced in peripheral blood mononuclear cells (PBMCs) (virus infectivity assays, VI assays), or their Env-pseudotyped (gp160) derivatives produced in 293T cells (PSV assays) from molecular clones or uncloned virus. Target cells included PBMC and genetically-engineered cell lines in either a single- or multiple-cycle infection format. Infection was quantified by using a range of assay read-outs that included extracellular or intracellular p24 antigen detection, RNA quantification and luciferase and beta-galactosidase reporter gene expression. FINDINGS: PSV assays were generally more sensitive than VI assays, but there were important differences according to the virus and inhibitor used. For example, for TriMab, the mean IC50 was always lower in PSV than in VI assays. However, with 4E10 or sCD4 some viruses were neutralized with a lower IC50 in VI assays than in the PSV assays. Inter-laboratory concordance was slightly better for PSV than for VI assays with some viruses, but for other viruses agreement between laboratories was limited and depended on both the virus and the neutralizing reagent. CONCLUSIONS: The NeutNet project demonstrated clear differences in assay sensitivity that were dependent on both the neutralizing reagent and the virus. No single assay was capable of detecting the entire spectrum of neutralizing activities. Since it is not known which in vitro assay correlates with in vivo protection, a range of neutralization assays is recommended for vaccine evaluation

Labcode 12- HIV neutralization Protocol Recombinant Viruses in HEK-293T

This document contained a protocol on HIV neutralization utilizing recombinant viruses in HEK-293T cells.Transfection efficiency is monitored by quantifying luciferase expression. Viral supernatants are titrated in U87.CD4-CCR5/CXCR4 cells depending on envelope tropism of the recombinant virus

Genetic Variability of Immunomodulatory Genes in Ectromelia Virus Isolates Detected by Denaturing High-Performance Liquid Chromatography

The genetic variability of nine genes in 12 isolates and strains of ectromelia virus, which causes a smallpox-like disease (mousepox) in mice, was determined and allows for classification of ectromelia viruses. The low genetic variability suggests that evolutionary pressure maintains the activity of immunomodulatory genes in natural poxvirus infections