Effector HIV-specific cytotoxic T-lymphocyte activity in long-term nonprogressors: associations with viral replication and progression

Elevated CD8 T-cell counts and virological failure in HIV-infected patients after combination antiretroviral therapy

Elevated CD8 counts with combination antiretroviral therapy (cART) initiation may be an early warning indicator for future treatment failure. Thus, we investigated whether elevated CD8 counts were associated with virological failure (VF) in the first 4 years of cART in Asian HIV-infected patients in a multicenter regional cohort.We included patients from the TREAT Asia HIV Observational Database (TAHOD). Patients were included in the analysis if they started cART between 1996 and 2013 with at least one CD8 measurement within 6 months prior to cART initiation and at least one CD8 and viral load (VL) measurement beyond 6 months after starting cART. We defined VF as VL ≥400 copies/mL after 6 months on cART. Elevated CD8 was defined as CD8 ≥1200 cells/μL. Time to VF was modeled using Cox regression analysis, stratified by site.In total, 2475 patients from 19 sites were included in this analysis, of whom 665 (27%) experienced VF in the first 4 years of cART. The overall rate of VF was 12.95 per 100 person-years. In the multivariate model, the most recent elevated CD8 was significantly associated with a greater hazard of VF (HR = 1.35, 95% CI 1.14-1.61; P = 0.001). However, the sensitivity analysis showed that time-lagged CD8 measured at least 6 months prior to our virological endpoint was not statistically significant (P = 0.420).This study indicates that the relationship between the most recent CD8 count and VF was possibly due to the CD8 cells reacting to the increase in VL rather than causing the VL increase itself. However, CD8 levels may be a useful indicator for VF in HIV-infected patients after starting cART.

Carbohydrate targets in HIV vaccine research: lessons from failures

Learning from the successes of other vaccines that enhance natural and existing protective responses to pathogens, the current effort in HIV vaccine research is directed toward inducing cytotoxic responses. Nevertheless, antibodies are fundamental players in vaccine development and are still considered in the context of passive specific immunotherapy of HIV, especially since several broadly neutralizing monoclonals are available. Special interest is directed toward antibodies binding to the glycan array on gp120 since they have the potential of broader reactivity and cross-clade neutralizing capacity. Humoral responses to carbohydrate antigens have proven effective against other pathogens, why not HIV? The variability of the epitope targets on HIV may not be the only problem to developing active or passive immunotherapeutic strategies. The dynamics of the infected immune system leads to ambiguous effects of most of the effector mechanisms calling for new approaches; some may already be available, while others are in the making.

HIV-specific CD8+ T cell responses to HXB2 Gag and Nef peptide pools in Chinese HIV/AIDS patients

HXB2 is primarily used as a template strain in developing HIV vaccines in Europe and the US. However, it is not yet known whether the strain can induce strong HIV-specific CD8+ T cell responses in Chinese HIV/AIDS patients. In the present study, two groups of subjects were investigated: 9 AIDS patients and 7 long-term nonprogressors (LTNPs). HIV-specific CD8+ T cell responses were examined in all patients through the ELISPOT assay. CD4+ T cell counts, CD8+ T cell counts, viral load and HIV subtype of each patient were also measured. Thailand B virus strain was identified among all the patients. The breadth and magnitude of HIV-specific CD8+ T cell responses in the LTNPs group are greater than those in the AIDS group (P<0.01). There is a positive correlation between magnitude of HIV-specific CD8+ T cell responses and CD4+ T cells, and a negative correlation between HIV-specific CD8+ T cell responses and mean viral load. In summary, the HIV-specific CD8+ T cell responses to the HXB2 Gag and Nef peptide pools are considerable in Chinese HIV/AIDS patients infected with Thailand B virus strain. HIV-1 vaccines based on HXB2 strain that can induce extensive immunity may be helpful for Chinese.

Predictors of disease progression in HIV infection: a review

During the extended clinically latent period associated with Human Immunodeficiency Virus (HIV) infection the virus itself is far from latent. This phase of infection generally comes to an end with the development of symptomatic illness. Understanding the factors affecting disease progression can aid treatment commencement and therapeutic monitoring decisions. An example of this is the clear utility of CD4+ T-cell count and HIV-RNA for disease stage and progression assessment. Elements of the immune response such as the diversity of HIV-specific cytotoxic lymphocyte responses and cell-surface CD38 expression correlate significantly with the control of viral replication. However, the relationship between soluble markers of immune activation and disease progression remains inconclusive. In patients on treatment, sustained virological rebound to >10,000 copies/mL is associated with poor clinical outcome. However, the same is not true of transient elevations of HIV RNA (blips). Another virological factor, drug resistance, is becoming a growing problem around the globe and monitoring must play a part in the surveillance and control of the epidemic worldwide. The links between chemokine receptor tropism and rate of disease progression remain uncertain and the clinical utility of monitoring viral strain is yet to be determined. The large number of confounding factors has made investigation of the roles of race and viral subtype difficult, and further research is needed to elucidate their significance. Host factors such as age, HLA and CYP polymorphisms and psychosocial factors remain important, though often unalterable, predictors of disease progression. Although gender and mode of transmission have a lesser role in disease progression, they may impact other markers such as viral load. Finally, readily measurable markers of disease such as total lymphocyte count, haemoglobin, body mass index and delayed type hypersensitivity may come into favour as ART becomes increasingly available in resource-limited parts of the world. The influence of these, and other factors, on the clinical progression of HIV infection are reviewed in detail, both preceding and following treatment initiation.

Sequential broadening of CTL responses in early HIV-1 infection is associated with viral escape

Background

Antigen-specific CTL responses are thought to play a central role in containment of HIV-1 infection, but no consistent correlation has been found between the magnitude and/or breadth of response and viral load changes during disease progression.

Methods and Findings

We undertook a detailed investigation of longitudinal CTL responses and HIV-1 evolution beginning with primary infection in 11 untreated HLA-A2 positive individuals. A subset of patients developed broad responses, which selected for consensus B epitope variants in Gag, Pol, and Nef, suggesting CTL-induced adaptation of HIV-1 at the population level. The patients who developed viral escape mutations and broad autologous CTL responses over time had a significantly higher increase in viral load during the first year of infection compared to those who did not develop viral escape mutations.

Conclusions

A continuous dynamic development of CTL responses was associated with viral escape from temporarily effective immune responses. Our results suggest that broad CTL responses often represent footprints left by viral CTL escape rather than effective immune control, and help explain earlier findings that fail to show an association between breadth of CTL responses and viral load. Our results also demonstrate that CTL pressures help to maintain certain elements of consensus viral sequence, which likely represent viral escape from common HLA-restricted CTL responses. The ability of HIV to evolve to escape CTL responses restricted by a common HLA type highlights the challenges posed to development of an effective CTL-based vaccine.

Alterations of natural killer cell and T-lymphocyte counts in adults infected with human immunodeficiency virus through blood and plasma sold in the past in China and in whom infection has progressed slowly over a long period

Natural killer (NK) cells, natural killer T (NKT) cells, and T lymphocytes were analyzed by using a flow cytometer in 225 human immunodeficiency virus (HIV)-positive individuals infected through the past sale of blood and plasma without receiving antiretroviral therapy in the People's Republic of China. According to CD4 T-cell counts these HIV-infected adults were stratified into three groups: long-term slow progressors, HIV-infected subjects, and AIDS patients. NK cell counts in long-term slow progressors were higher compared to HIV infection and AIDS patients (P < 0.05) and lower compared to normal controls (P < 0.05), whereas NKT cell counts in slow progressors and the HIV infection group were not different from those of normal controls. NK cell counts in HIV-seropositive subjects were positively correlated with CD4 T-cell counts (P < 0.05), and NKT cell counts were positively correlated with CD4 T-cell and CD8 T-cell counts (P < 0.05). The CD8 T-cell counts were higher in slow progressors compared to those with HIV infection, AIDS patients, and normal controls. These results indicated that HIV infection causes alterations of NK cells and T cells in slow progressors, HIV-infected subjects, and AIDS patient groups, but no difference was found in NKT cell counts and percentages in slow progressors and the HIV-infected group compared to normal controls.

HIV-Specific Cytotoxic Cell Frequencies Measured Directly Ex Vivo by the Lysispot Assay Can Be Higher or Lower Than the Frequencies of IFN-γ-Secreting Cells: Anti-HIV Cytotoxicity Is Not Generally Impaired Relative to Other Chronic Virus Responses

CD8(+) T cells in HIV-infected patients are believed to contribute to the containment of the virus and the delay of disease progression. However, the frequencies of HIV-specific CD8(+) T cells, as measured by IFN-gamma secretion and tetramer binding, often do not correlate with a delay in disease progression during chronic infection. Using the Lysispot and ELISPOT assays, we measured the frequencies of cytotoxic and IFN-gamma-secreting T cells responding to overlapping peptides from Gag, Nef, Env, and Pol consensus HIV-1 clade B sequences. PBMC from the majority of HIV-infected subjects have significant frequencies of HIV-specific cells that killed targets within 5 h directly ex vivo. The relative frequencies of IFN-gamma-secreting and cytotoxic cells varied markedly between different HIV peptide pools within the same patient, and some T cells lysed targets without secreting IFN-gamma. These results indicate that measurement of IFN-gamma production alone may be insufficient to evaluate the breadth of the HIV-specific T cell response. Also, neither the CTL to IFN-gamma ratios nor the ex vivo CTL frequencies specific for different HIV proteins were consistently lower than responses specific for two other chronic viral infections, human CMV and EBV, within the same subjects. Thus ex vivo cytotoxic T cell frequencies do not provide evidence for a model of "preterminal differentiation" of HIV-specific CD8(+) T cells during chronic HIV infection. Analysis of the frequency of directly cytotoxic HIV-specific T cells may be of considerable value in the assessment of disease progression and the potential efficacy of HIV vaccines.

Comparative potency of three antiretroviral therapy regimes in primary HIV infection

BACKGROUND

Virally mediated destruction of HIV-specific CD4+ T-cells in primary HIV infection (PHI) may be abrogated by potent antiretroviral therapy (ART) started in acute infection. To best achieve the most rapid reduction in primary viraemia we compared three different ART regimens in PHI.

STUDY DESIGN AND METHODS

A sequential, unblinded, non-randomized prospective cohort study. The primary endpoint was time to achieve plasma viral load (pVL) < 50 copies HIV RNA/ml. One hundred and five patients identified with PHI according to the definition: HIV antibody negative with positive HIV DNA (n = 22), HIV antibody positive with a documented negative test within the previous 6 months (n = 53), low-level incident 'detuned' assay (n = 10) or an evolving HIV-antibody test (n = 20) were recruited. Ninety of 105 individuals chose to take a short course of ART at PHI whereas 15 of 105 declined therapy. Seventy-nine of 90 were included for analysis and were allocated sequentially to either three (29 of 79) or four-drug (33 of 79) or protease inhibitor-containing ART (17 of 79).

RESULTS

A mathematical model-based analysis of viral decay indicated significantly faster viral load decline in patients receiving the four-drug regimen (P = 0.01). This conclusion was supported by a non-significant on-treatment analysis of the time taken to reach pVL <50 copies HIV RNA/ml (P = 0.07) but not by the corresponding intend-to-treat analysis. This discordance was caused by greater toxicities associated with the four-drug regimen, although the differences were not significant.

CONCLUSION

Of the three treatment regimens compared, the four-drug arm enhanced the rate of decline of primary viraemia but at the cost of toxicity.

HIV-1 reverse transcriptase targeted for proteasomal degradation as a prototype vaccine against drug-resistant HIV-1

Acquisition of drug-resistance conferring mutations leads to an enhanced degradation of HIV-1 reverse transcriptase (RT) affecting its immunogenicity. The mechanism of this degradation is not known. We investigated the input of proteasome in this degradation, and explored a possibility to enhance the proteasomal degradation of RTs to potentiate the immunogenic peformance of RT genes. To this end, a C-terminal fusion was made of RT with ornithine decarboxylase (ODC) that is rapidly degraded by proteasome in an ubiquitine-independent fashion. Eukaryotic cells were transiently transfected with the genes for wild-type (wt) RT, multi-drug-resistant (MDR) RT, and their chimeras with ODC. RT expression in the presence or absence of the proteasome inhibitors MG132 and epoxomicin was quantified by Western blotting. Treatment with MG132 led to a two-fold increase in the level of wtRT, and a four-fold increase in the level of MDR-RT accumulation. Treatment with epoxomicin had virtually no effect on the accumulation of wtRT, while stabilizing MDR-RT two-fold. Since epoxomicin is a more specific proteasome inhibitor, it indicated that degradation of wtRT may not be solely proteasomal. Fusion to ODC considerably decreased the intracellular levels of both RT-ODC and MDR-RT-ODC as compared to parental proteins. MG132 treatment increased the intracellular RT-ODC content 20-fold (up the level of the MG132-treated wtRT; 60-80 fg/cell), and epoxomicin treatment, 10-fold as compared to non-treated samples. Thus, attachment of ODC moiety has modified the metabolic pathway of RT targeting it to proteasomal degradation. We are currently testing if this is translated into an enhanced MHC class I performance of wild-type and drug-resistant RTs in gene immunization.

Properties of anti-gp41 core structure antibodies, which compete with sera of HIV-1-infected patients

To determine the correlation between the immunoreaction against the core structure of human immunodeficiency virus type (HIV-1) transmembrane protein gp41 epitopes and the disease progression, it is essential to evaluate the anti-core structure antibody epitopes and the humoral immunity against the epitopes. For this purpose we evaluated monoclonal antibodies (mAbs) against the gp41 core structure such as mAbs 50.69, 98.6 and T26, by Western blotting (WB) and flow cytometry. WB showed mAbs 50.69 and 98.6 bound to both monomeric and oligomeric gp41, and mAb T26 exclusively bound to oligomeric gp41. We evaluated the sera from Pneumocystis pneumonia patients (PCP; n=7) and long-term survivors (LTS; n=7). Competition assay with sera and mAbs for binding to H9 cells infected with HIV-1 IIIB virus was done using flow cytometry. The results revealed that PCP sera as well as LTS sera inhibited the binding of all the three mAbs, and the PCP sera inhibited mAb T26 binding more efficiently than LTS. Therefore, PCP patients retain competing immunity to antibodies against not only the shared epitopes of the core structure (binding sites of mAbs 50.69 and 98.6) but also against oligomeric gp41 specific epitope (binding site of mAb T26).