Changes in HIV-1 Capsid Stability Induced by Common Cytotoxic-T-Lymphocyte-Driven Viral Sequence Mutations.

UNLABELLED: HIV-1-infected individuals with protective HLA class I alleles exhibit better control of viremia and slower disease progression. Virus control in these individuals has been associated with strong and potent HIV-1-specific cytotoxic-T-lymphocyte (CTL) responses restricted by protective HLA alleles, but control of viremia also occurs in the presence of selected CTL escape mutations. CTL escape mutations restricted by protective HLA class I molecules are frequently located in the conserved p24 Gag sequence of HIV-1 that encodes the conical capsid core and have been suggested to reduce viral replication capacity. In this study, the consequences of well-described CTL-associated p24 Gag sequence mutations for HIV-1 capsid stability were assessed using a cyclosporine (CsA) washout assay. The frequently occurring HLA-B57- and HLA-B27-associated CTL escape mutations T242N and R264K resulted in delayed capsid uncoating, suggesting modulation of capsid stability. The described compensatory mutations L268M and S173A observed in R264K viruses reconstituted the capsid-uncoating half-time. Interestingly, capsid stability was correlated with infectivity. Taken together, these data demonstrate that CTL-driven escape mutations within p24 Gag restricted by protective HLA class I alleles have a significant impact on capsid stability that might contribute to the persistent control of viral replication observed despite viral escape from CTL responses. IMPORTANCE: Sequence mutations within p24 Gag selected by CTL responses restricted by protective HLA class I alleles have been associated with reduced viral fitness. However, the precise mechanisms underlying the reduced viral replication capacity and lower viral loads associated with these mutations remain unclear. Here, we demonstrate that dominant HLA-B27-associated CTL escape mutations within HIV-1 capsid lead to enhanced capsid rigidity, providing a possible mechanism for the reduced viral fitness of these variants.

Kinetics of HIV-1 Latency Reversal Quantified on the Single-Cell Level Using a Novel Flow-Based Technique.

UNLABELLED: HIV-1 establishes a pool of latently infected cells early following infection. New therapeutic approaches aiming at diminishing this persisting reservoir by reactivation of latently infected cells are currently being developed and tested. However, the reactivation kinetics of viral mRNA and viral protein production, and their respective consequences for phenotypical changes in infected cells that might enable immune recognition, remain poorly understood. We adapted a novel approach to assess the dynamics of HIV-1 mRNA and protein expression in latently and newly infected cells on the single-cell level by flow cytometry. This technique allowed the simultaneous detection of gagpol mRNA, intracellular p24 Gag protein, and cell surface markers. Following stimulation of latently HIV-1-infected J89 cells with human tumor necrosis factor alpha (hTNF-α)/romidepsin (RMD) or HIV-1 infection of primary CD4(+) T cells, four cell populations were detected according to their expression levels of viral mRNA and protein. gagpol mRNA in J89 cells was quantifiable for the first time 3 h after stimulation with hTNF-α and 12 h after stimulation with RMD, while p24 Gag protein was detected for the first time after 18 h poststimulation. HIV-1-infected primary CD4(+) T cells downregulated CD4, BST-2, and HLA class I expression at early stages of infection, proceeding Gag protein detection. In conclusion, here we describe a novel approach allowing quantification of the kinetics of HIV-1 mRNA and protein synthesis on the single-cell level and phenotypic characterization of HIV-1-infected cells at different stages of the viral life cycle. IMPORTANCE: Early after infection, HIV-1 establishes a pool of latently infected cells, which hide from the immune system. Latency reversal and immune-mediated elimination of these latently infected cells are some of the goals of current HIV-1 cure approaches; however, little is known about the HIV-1 reactivation kinetics following stimulation with latency-reversing agents. Here we describe a novel approach allowing for the first time quantification of the kinetics of HIV-1 mRNA and protein synthesis after latency reactivation or de novo infection on the single-cell level using flow cytometry. This new technique furthermore enabled the phenotypic characterization of latently infected and de novo-infected cells dependent on the presence of viral RNA or protein.

Killer-cell Immunoglobulin-like Receptor (KIR) gene profiles modify HIV disease course, not HIV acquisition in South African women.

BACKGROUND: Killer-cell Immunoglobulin-like Receptors (KIR) interact with Human Leukocyte Antigen (HLA) to modify natural killer- and T-cell function. KIR are implicated in HIV acquisition by small studies that have not been widely replicated. A role for KIR in HIV disease progression is more widely replicated and supported by functional studies. METHODS: To assess the role of KIR and KIR ligands in HIV acquisition and disease course, we studied at-risk women in South Africa between 2004-2010. Logistic regression was used for nested case-control analysis of 154 women who acquired vs. 155 who did not acquire HIV, despite high exposure. Linear mixed-effects models were used for cohort analysis of 139 women followed prospectively for a median of 54 months (IQR 31-69) until 2014. RESULTS: Neither KIR repertoires nor HLA alleles were associated with HIV acquisition. However, KIR haplotype BB was associated with lower viral loads (-0.44 log10 copies/ml; SE = 0.18; p = 0.03) and higher CD4+ T-cell counts (+80 cells/µl; SE = 42; p = 0.04). This was largely explained by the protective effect of KIR2DL2/KIR2DS2 on the B haplotype and reciprocal detrimental effect of KIR2DL3 on the A haplotype. CONCLUSIONS: Although neither KIR nor HLA appear to have a role in HIV acquisition, our data are consistent with involvement of KIR2DL2 in HIV control. Additional studies to replicate these findings are indicated.

HIV evolution: CTL escape mutation and reversion after transmission.

Within-patient HIV evolution reflects the strong selection pressure driving viral escape from cytotoxic T-lymphocyte (CTL) recognition. Whether this intrapatient accumulation of escape mutations translates into HIV evolution at the population level has not been evaluated. We studied over 300 patients drawn from the B- and C-clade epidemics, focusing on human leukocyte antigen (HLA) alleles HLA-B57 and HLA-B5801, which are associated with long-term HIV control and are therefore likely to exert strong selection pressure on the virus. The CTL response dominating acute infection in HLA-B57/5801-positive subjects drove positive selection of an escape mutation that reverted to wild-type after transmission to HLA-B57/5801-negative individuals. A second escape mutation within the epitope, by contrast, was maintained after transmission. These data show that the process of accumulation of escape mutations within HIV is not inevitable. Complex epitope- and residue-specific selection forces, including CTL-mediated positive selection pressure and virus-mediated purifying selection, operate in tandem to shape HIV evolution at the population level.

The role of natural killer cells in liver inflammation.

The liver is an important immunological site that can promote immune tolerance or activation. Natural killer (NK) cells are a major immune subset within the liver, and therefore understanding their role in liver homeostasis and inflammation is crucial. Due to their cytotoxic function, NK cells are important in the immune response against hepatotropic viral infections but are also involved in the inflammatory processes of autoimmune liver diseases and fatty liver disease. Whether NK cells primarily promote pro-inflammatory or tolerogenic responses is not known for many liver diseases. Understanding the involvement of NK cells in liver inflammation will be crucial in effective treatment and future immunotherapeutic targeting of NK cells in these disease settings. Here, we explore the role that NK cells play in inflammation of the liver in the context of viral infection, autoimmunity and fatty liver disease.

Substantial differences in specificity of HIV-specific cytotoxic T cells in acute and chronic HIV infection.

Cytotoxic T lymphocytes (CTLs) play a vital part in controlling viral replication during human viral infections. Most studies in human infections have focused on CTL specificities in chronic infection and few data exist regarding the specificity of the initial CTL response induced in acute infection. In this study, HIV-1 infection in persons expressing human histocompatibility leukocyte antigen (HLA)-A*0201 was used as a means of addressing this issue. In chronic infection, the dominant HLA-A*0201-restricted CTL response is directed towards the epitope SLYNTVATL ("SL9") in p17 Gag (residues 77-85). This epitope is targeted by 75% of HLA-A*0201-positive adults, and the magnitude of this A*0201-SL9 response shows a strong negative association with viral load in progressive infection. Despite using the highly sensitive peptide-major histocompatibility complex tetramer and intracellular cytokine assays, responses to the SL9 epitope were not detectable in any of 11 HLA-A*0201-positive subjects with acute HIV-1 infection (P = 2 x 10(-6)), even when assays were repeated using the SL9 peptide variant that was encoded by their autologous virus. In contrast, multiple responses (median 3) to other epitopes were evident in 7 of the 11 A*0201-positive subjects. Longitudinal study of two subjects confirmed that the A*0201-SL9 response emerged later than other CTL responses, and after viral set point had been reached. Together, these data show that the CTL responses that are present and that even may dominate in chronic infection may differ substantially from those that constitute the initial antiviral CTL response. This finding is an important consideration in vaccine design and in the evaluation of vaccine candidates.

Functionally inert HIV-specific cytotoxic T lymphocytes do not play a major role in chronically infected adults and children.

The highly sensitive quantitation of virus-specific CD8(+) T cells using major histocompatibility complex-peptide tetramer assays has revealed higher levels of cytotoxic T lymphocytes (CTLs) in acute and chronic virus infections than were recognized previously. However, studies in lymphocytic choriomeningitis virus infection have shown that tetramer assays may include measurement of a substantial number of tetramer-binding cells that are functionally inert. Such phenotypically silent CTLs, which lack cytolytic function and do not produce interferon (IFN)-gamma, have been hypothesized to explain the persistence of virus in the face of a quantitatively large immune response, particularly when CD4 help is impaired. In this study, we examined the role of functionally inert CTLs in chronic HIV infection. Subjects studied included children and adults (n = 42) whose viral loads ranged from <50 to >100,000 RNA copies/ml plasma. Tetramer assays were compared with three functional assays: enzyme-linked immunospot (Elispot), intracellular cytokine staining, and precursor frequency (limiting dilution assay [LDA]) cytotoxicity assays. Strong positive associations were observed between cell numbers derived by the Elispot and the tetramer assay (r = 0.90). An even stronger association between tetramer-derived numbers and intracellular cytokine staining for IFN-gamma was present (r = 0.97). The majority (median 76%) of tetramer-binding cells were consistently detectable via intracellular IFN-gamma cytokine staining. Furthermore, modifications to the LDA, using a low input cell number into each well, enabled LDAs to reach equivalence with the other methods of CTL enumeration. These data together show that functionally inert CTLs do not play a significant role in chronic pediatric or adult HIV infection.

Cellular immune responses and viral diversity in individuals treated during acute and early HIV-1 infection.

Immune responses induced during the early stages of chronic viral infections are thought to influence disease outcome. Using HIV as a model, we examined virus-specific cytotoxic T lymphocytes (CTLs), T helper cells, and viral genetic diversity in relation to duration of infection and subsequent response to antiviral therapy. Individuals with acute HIV-1 infection treated before seroconversion had weaker CTL responses directed at fewer epitopes than persons who were treated after seroconversion. However, treatment-induced control of viremia was associated with the development of strong T helper cell responses in both groups. After 1 yr of antiviral treatment initiated in acute or early infection, all epitope-specific CTL responses persisted despite undetectable viral loads. The breadth and magnitude of CTL responses remained significantly less in treated acute infection than in treated chronic infection, but viral diversity was also significantly less with immediate therapy. We conclude that early treatment of acute HIV infection leads to a more narrowly directed CTL response, stronger T helper cell responses, and a less diverse virus population. Given the need for T helper cells to maintain effective CTL responses and the ability of virus diversification to accommodate immune escape, we hypothesize that early therapy of primary infection may be beneficial despite induction of less robust CTL responses. These data also provide rationale for therapeutic immunization aimed at broadening CTL responses in treated primary HIV infection.

NK cells in HIV-1 infection: evidence for their role in the control of HIV-1 infection.

Increasing evidence supports the notion that the innate immune response, and in particular, natural killer cells play a central role in determining the quality of the host immune response to infection. In this review we highlight recent evidence that suggests that NK cells influence the clinical fate of HIV-infected individuals.

The role of CD4(+) T helper cells in the cytotoxic T lymphocyte response to HIV-1.

Virus-specific CD4(+) T cell help and CD8(+) cytotoxic T cell (CTL) responses are critical for the maintenance of effective immunity in chronic viral infections. HIV-1 infection presents a unique situation in which HIV-1-specific T helper cell responses are characteristically impaired and virus-specific CTLs wane over time as disease progresses; a relationship exists between T cell help and CTL responses in HIV-1 infection.

Structured treatment interruptions following immediate initiation of HAART in eight patients with acute HIV-1 seroconversion.

BACKGROUND: The immunological and clinical benefits of structured treatment interruptions (STIs) during primary HIV-1 infection remain largely unclear. PATIENTS AND METHODS: Eight patients identified during primary HIV-1 infection were immediately treated with HAART and underwent subsequent STIs after reaching complete viral suppression of HIV-RNA in peripheral plasma. HAART was re-initiated if either HIV-1 RNA >5000 copies/ml, CD4-cells <200 cells/microl or symptomatic HIV-1 disease was observed. RESULTS: After treatment discontinuation, four of eight patients were able to persistently control HIV-1 viremia below 5000 copies/ml until the last time point of follow-up (median 3 years). CD4-cell counts were within the interquartile range of untreated individuals compared to historical reference data from the MACS cohort. In the remaining study subjects persistent virological control was not reached despite repeated STIs. Moreover, compared to the MACS cohort repetitive virological failures during STIs appeared to induce an accelerated decline of CD4-cells. CONCLUSION: Spontaneous HIV-1 control after treated primary HIV-1 infection was possible in four out of eight individuals, however, if STIs after treated primary infection ameliorate the overall HIV-1 disease progression remains unknown. In the absence of viral control, repetitive viral exposure during STIs might be associated with accelerated decline of CD4-cell counts.

Distinct genital tract HIV-specific antibody profiles associated with tenofovir gel.

The impact of topical antiretrovirals for pre-exposure prophylaxis on humoral responses following HIV infection is unknown. Using a binding antibody multiplex assay, we investigated HIV-specific IgG and IgA responses to envelope glycoproteins, p24 Gag and p66, in the genital tract (GT) and plasma following HIV acquisition in women assigned to tenofovir gel (n=24) and placebo gel (n=24) in the CAPRISA 004 microbicide trial to assess if this topical antiretroviral had an impact on mucosal and systemic antibody responses. Linear mixed effect modeling and partial least squares discriminant analysis was used to identify multivariate antibody signatures associated with tenofovir use. There were significantly higher response rates to gp120 Env (P=0.03), p24 (P=0.002), and p66 (P=0.009) in plasma and GT in women assigned to tenofovir than placebo gel at multiple time points post infection. Notably, p66 IgA titers in the GT and plasma were significantly higher in the tenofovir compared with the placebo arm (P<0.05). Plasma titers for 9 of the 10 HIV-IgG specificities predicted GT levels. Taken together, these data suggest that humoral immune responses are increased in blood and GT of individuals who acquire HIV infection in the presence of tenofovir gel.

Regulatory and accessory HIV-1 proteins: potential targets for HIV-1 vaccines?

The HIV-1 regulatory proteins Tat and Rev and the accessory proteins Vpr, Vpu and Vif are essential for efficient viral replication, and their cytoplasmic production suggests that they should be processed for recognition by cytotoxic T lymphocytes. However, only limited data is available, evaluating the role of immune responses directed against these proteins in natural HIV-1 infection. Recent advances in the methods used for the characterization of HIV-1-specific cellular immune responses, including quantification of antigen-specific IFN-gamma production by ELISpot assay and flow-cytometry-based intracellular cytokine quantification, have allowed for a much more comprehensive assessment of virus-specific immune responses. Emerging data show that the regulatory and accessory proteins serve as important targets for HIV-1-specific T cell responses, and multiple CTL epitopes have been identified in functionally important regions of these proteins. Moreover, the use of autologous peptides have allowed for the detection of significantly stronger HIV-1-specific T cell responses in the more variable regulatory and accessory HIV-1 proteins Tat and Vpr. These data indicate that despite the small size of these proteins, regulatory and accessory proteins are targeted by cellular immune responses in natural HIV-1 infection and contribute importantly to the total HIV-1-specific CD8+ T cell response. A multi-component vaccine, with the inclusion of these proteins plus structural proteins remains the most promising choice for an effective AIDS vaccine.

Semiquantitation of human chemokine mRNA levels with a newly constructed multispecific competitor fragment.

Chemokines are a group of inducible, locally acting proinflammatory cytokines which have been implicated in the pathogenesis of a variety of diseases. Important members of the group include monocyte chemoattractant protein (MCP)-1, -2, -3, macrophage inhibitory protein (MIP)-1alpha, -1beta and RANTES (regulated upon activation, normal T expressed and secreted). To facilitate further investigation of the human chemokines, we have constructed a novel multispecific competitor fragment containing primer binding sites for the CC-chemokines MCP-1, MCP-2, MCP-3, MIP-1alpha, MIP-1beta and RANTES, the CXC-chemokines MIP-2alpha, MIP-2beta as well as for the housekeeping gene beta-actin. Using this competitor fragment we can demonstrate reliable semiquantitation of reverse transcribed chemokine mRNAs. The assay should be useful for further studies, in particular for the semiquantitation of chemokine mRNA species from small cell or tissue specimens.

Parallel decrease in neurotoxin quinolinic acid and soluble tumor necrosis factor receptor p75 in serum during highly active antiretroviral therapy of HIV type 1 disease.

The chronic immune activation state in HIV disease leads to increased activity of the rate-limiting tryptophan-kynurenine pathway enzyme indoleamine 2,3-dioxygenase (2,3-IDO), thereby increasing the formation of neurotoxic tryptophan metabolites such as kynurenine and quinolinic acid. We investigated whether highly active antiretroviral therapy (HAART) (median duration, 100 days; range, 50-188 days) lowers serum levels of these metabolites in HIV-infected individuals and if so, whether this was paralleled by changes in a surrogate marker for immune activation, i.e., soluble tumor necrosis factor receptor p75 (sTNFR p75) concentrations. Baseline quinolinic acid (848 nM, 95% CI 567-1130 vs. 303 nM, 95% CI 267.1-339.5) and kynurenine (4.1 microM, 95% CI 3.3-4.9 vs. 2.7 microM, 95% CI 2.4-2.9) concentrations as well as the mean kynurenine-to-tryptophan ratio (108.2, 95% CI 76.1-140.4 vs. 51.4, 95% CI 47.6-55.3) in 17 HIV-1-infected outpatients (7 with AIDS) were significantly higher than those in 55 healthy age-matched controls (p < 0.01), respectively. Serum quinolinic acid concentrations in 14 of 17 patients decreased (mean, -44.4%) during HAART in comparison with baseline (471.2 nM, 95% CI 288-654.3; p = 0. 022). Thirteen of these 14 patients also had decreases in sTNFR p75 concentrations. Overall, the mean sTNFR p75 concentration decreased by 36.3% (13.5 ng/ml, 95% CI 9.3-17.8 vs. 8.6 ng/ml, 95% CI 5.9-11. 4; p = 0.01, n = 17). Reduction in viral load through HAART and subsequent mitigation of the pathological immune activation state in HIV disease may have reduced 2,3-IDO over activation. This eventually led to a decrease in quinolinic acid formation. The parallel reduction of the immune activation marker sTNFR p75 supports this hypothesis.

Cytotoxic T-lymphocyte (CTL) responses directed against regulatory and accessory proteins in HIV-1 infection.

The HIV-1 regulatory proteins Tat and Rev and the accessory proteins Vpr, Vpu, and Vif are essential for viral replication, and their cytoplasmic production suggests that they should be processed for recognition by cytotoxic T lymphocytes. However, only limited data is available evaluating to which extent these proteins are targeted in natural infection and optimal cytotoxic T lymphocyte (CTL) epitopes within these proteins have not been defined. In this study, CTL responses against HIV-1 Tat, Rev, Vpr, Vpu, and Vif were analyzed in 70 HIV-1 infected individuals and 10 HIV-1 negative controls using overlapping peptides spanning the entire proteins. Peptide-specific interferon-gamma (IFN-gamma) production was measured by Elispot assay and flow-based intracellular cytokine quantification. HLA class I restriction and cytotoxic activity were confirmed after isolation of peptide-specific CD8+ T-cell lines. All regulatory and accessory proteins served as targets for HIV-1- specific CTL and multiple CTL epitopes were identified in functionally important regions of these proteins. In certain individuals HIV-1-specific CD8+ T-cell responses to these accessory and regulatory proteins contributed up to a third to the magnitude of the total HIV-1-specific CTL response. These data indicate that despite the small size of these proteins regulatory and accessory proteins are targeted by CTL in natural HIV-1 infection, and contribute importantly to the total HIV-1-specific CD8+ T-cell responses. These findings are relevant for the evaluation of the specificity and breadth of immune responses during acute and chronic#10; infection, and will be useful for the design and testing of candidate human immunodeficiency virus (HIV) vaccines.

Indication, outcome and follow up of intensive care in patients with HIV-infection.

BACKGROUND/AIM: The admission to intensive care is controversially discussed in patients with HIV infection, since life expectancy is limited. Therefore, we analyzed indications, outcomes and follow up of all patients with confirmed HIV-infection and Aids defining symptoms who had been admitted to the intensive care unit (ICU) of our department between 1985-1996. RESULTS: 49 patients were admitted to the ICU, 42 of them with CDC stage C of HIV infection before admission. The leading indications were pneumonia (n = 15; PCP: 10, bacterial: 5), acute bleedings (n = 14), acute neurological diseases (n = 6), and gastrointestinal perforation (n = 5). Overall mortality was 39% (19/49) with a higher mortality seen in patients with respiratory disorders (53%) compared to non-respiratory disorders (22%, n.s.). The only significant predictor of mortality was the serum creatinine (p = 0.001), while differences in the APACHE II score between survivors and non-survivors did not reach statistical significance (22 +/- 7, 16 +/- 5; p = 0.14). During follow up no difference was seen in the life expectancy of HIV-infected survivors of intensive care as compared to those patients with AIDS who had never been admitted to ICU (8.4 months versus 9 months). DISCUSSION: The need for intensive care in HIV infected patients does not accelerate the progression of HIV infection to death, if the complications requiring ICU intervention can be managed successfully. Respiratory infections and impaired renal function are risk factors for a fatal outcome. Thus, HIV infected patients benefit from intensive care therapy.

Failure of double protease inhibitor therapy as a salvage therapy for HIV-infected patients resistant to conventional triple therapy.

A therapeutic dilemma arises once HIV-infected patients develop a break-through of HIV-replication under potent antiretroviral therapy. Therefore, we studied whether patients (n = 12) who failed double nucleoside reverse transcriptase (NRTI) plus indinavir or ritonavir triple therapy can be rescued when therapy is switched to double protease inhibitor (PI) treatment (nelfinavir and hard gel saquinavir) and stavudine. With the rescue regimen HIV-RNA levels initially dropped from 148,571 +/- 45,258 copies/ml to 9,310 +/- 6, 965 copies/ml at week 4 (p = 0.0117). However, virus load subsequently increased to almost baseline levels (131,230 +/- 37,743 copies/ml) at week 12. Likewise, CD4-cell counts could only be stabilized initially (baseline 267 +/- 51; week 4 296 +/- 65 cells/microl), but gradually declined thereafter (216 +/- 34 cells/microl week 12). Before therapy was switched, the viral protease gene from 5 analyzed patients showed 3-5 amino acid substitutions. Moreover, 4 of these patients had one amino acid substitution associated with resistance to nelfinavir. Our data suggest that HIV-infected patients resistant to indinavir or ritonavir and double NRTI combination therapy respond to double PI nelfinavir/saquinavir and D4T rescue therapy only initially but have no sustained benefit.