Association of CD4+ T-lymphocyte counts and new thymic emigrants in HIV-infected children during successful highly active antiretroviral therapy

Evaluation of HIV-1 DNA levels among adolescents living with perinatally acquired HIV-1 in Yaounde, Cameroon: A contribution to paediatric HIV cure research in Sub-Saharan Africa

Background

With the advent of antiretroviral therapy (ART), most children living with HIV in sub-Saharan Africa (SSA) are growing toward adolescence, with scarcity of evidence on the size of viral reservoirs to enhance paediatric cure research strategies. This study aims to compare HIV-1 proviral DNA levels according to virological response among adolescents living with perinatally acquired HIV-1 (ALPHIV) and identify associated-factors in the Cameroonian context.

Methods

In this observational cohort study, HIV-1 RNA viremia and CD4+ T-cell count were assessed through RT-PCR and flow cytometry respectively at three time-points over 18 months of observation. At the third time-point, 80 randomly-selected participants were classified as with viremia (≥50 HIV-1 copies/mL; n = 40) or without viremia (<50 HIV-1 copies/mL; n = 40); immune-competent (≥500 CD4+ T cells/mm3) or immunocompromised (<500 CD4+ T cells/mm3). Among these participants, total HIV-1 DNA load was quantified through droplet digital PCR using Bio-Rad QX200.

Results

Of the 80 randomly-selected adolescents, median [IQR] age was 15 (13-17) years, 56.2% were female, duration on ART was 9.3 [5.4-12.2] years. Among the 40 viremic ones (median viremia 7312 [283-71482]) HIV-1 copies/ml, 75.0% (30/40) were in virological failure (≥1000 HIV-1 copies/ml), while median of CD4 T cells were 494 [360-793] cell/mm3 with 48.8% (39/80) immunocompromised. No significant variation in HIV-1 RNA viremia and CD4 T cell count was observed between the three time-points, and 13.7% (11/80) adolescents remained aviremic and immune-competent throughout (stable adolescents). A positive and moderate correlation (r = 0.59; p < 0.001) was found between HIV-1 DNA levels and HIV- 1 RNA viremia. Regarding the CD4 T cell count, a negative and weak correlation (r = -0.28; p = 0.014) was found with HIV-1 DNA loads only among adolescents with viremia. Starting ART within the first year of life, ART for over 9 years and aviremia appear as predictors of low HIV-1 DNA loads.

Conclusion

Among ALPHIV, high HIV-1 RNA indicates an elevated viral reservoir size, representing a drawback to cure research. Interestingly, early ART initiation and longer ARTduration lead to sustained viral control and limited HIV-1 reservoir size. As limited size of viral reservoir appears consistent with viral control and immune competence, adolescents with sustained viral control (about 14% of this target population) would be candidates for analytical ART interruptions toward establishing paediatric post-treatment controllers in SSA.

Characterization of CD31 expression in CD4+ and CD8+T cell subpopulations in chronic untreated HIV infection

BACKGROUND

The platelet endothelial cell adhesion molecule-1 (PECAM-1) or CD31 has been involved in regulation of T-cell tolerance, activation, survival and homing in mice cells. However, there is limited knowledge about the expression pattern and role of this molecule in human T cells, particularly in conditions of chronic immune activation.

OBJECTIVES

We explored CD31 expression in T cell differentiation subsets of individuals with untreated HIV infection and in non-HIV-infected controls. We also assessed phenotypic differences between CD31+ and CD31- subsets in memory and terminally differentiated (TEMRA) CD4+ and CD8 + T cells.

METHODS

Forty-one individuals with untreated HIV infection and 34 non-HIV-infected controls were included in the study. We compared the expression of CD31 in CD4+ and CD8 + T cells across stages of differentiation in the two study groups by flow cytometry. We also analyzed the expression of CD57 (a marker of senescence), Ki67 (a marker of cycling cells), PD-1 (a marker of exhaustion), and CD38/HLA-DR (a marker of immune activation) on memory and TEMRA CD31+ and CD31- T cells.

RESULTS

CD31 expression was significantly higher in CD8 + T cells than in CD4 + T cells, measured as frequency, absolute numbers and median fluorescence intensity (MFI), in both study groups (p < 0.0001 in all cases). Intermediate differentiation subsets of CD4+ and CD8 + T cells expressed higher levels of CD31 in the context of HIV infection (p < 0.001 in all cases). CD31 expression frequency decreased with cellular differentiation of CD4+ and CD8 + T cells in both groups, but this decrease was steeper in individuals without HIV infection (CD4+: p < 0.001 and CD8+: p < 0.0001). As expected, memory and TEMRA CD4+ and CD8 + T cells expressed significantly higher levels of CD57, PD-1, Ki67 and CD38/HLA-DR in HIV-infected compared to non-HIV-infected individuals (p < 0.01 in all cases). CD31 expression was associated with lower activation of memory (but not TEMRA) CD4 + T cells in non-HIV-infected persons, an effect not observed in the HIV-infected group. CD31 expression on memory CD8 + T cells of HIV-infected individuals was associated higher levels of PD-1 (p = 0.0019) and CD38/HLADR (p = 0.0345), and higher PD-1 expression on CD8 + TEMRA (p = 0.0024), an effect not observed in non-HIV-infected individuals.

CONCLUSION

In the context of HIV-associated chronic immune activation, specifically on memory CD8 + T cells, CD31 expression was associated with higher PD-1 and CD38/HLA-DR co-expression, suggesting that CD31 expression may result from an insufficient attempt to contain T cell exhaustion and activation. CD31-targeted therapies may contribute to modulate these cellular responses.

Recent Thymus Emigrant CD4+ T Cells Predict HIV Disease Progression in Patients With Perinatally Acquired HIV

BACKGROUND

Robust immune restoration in human immunodeficiency virus (HIV)-positive patients is dependent on thymic function. However, few studies have investigated thymic function and its correlation with disease progression over time in HIV-positive patients.

METHODS

In this longitudinal prospective study, we followed 69 HIV-positive patients who were perinatally infected. Peripheral blood mononuclear cells were stained with monoclonal anti-CD4 and anti-CD31 and recent thymic emigrants (CD4+recently emigrated from the thymus (RTE), CD4+CD31+) quantified by flow cytometry. Statistical analysis used Wilcoxon rank sum test, Kruskal-Wallis, Spearman correlation, and Kaplan-Meier estimates; Cox regression models were performed for the longitudinal analysis.

RESULTS

Median age of HIV positive patients enrolled was 13 years (interquartile range [IQR], 8.6). CD4+RTE% decreased with age and was higher in females. Median CD4+RTE% was 53.5%, IQR, 22.9. CD4+RTE% was closely related to CD4+% and absolute counts but independent of viral load and CD8+CD38+%. Antiretroviral compliance as well as higher nadir CD4+% were associated with higher CD4+RTE%. Low CD4+RTE% predicted poor progression of VL and CD4+% over time.

CONCLUSIONS

CD4+RTE% predicts disease progression and may reflect history of disease in HIV-positive patients and adolescents. They are easy to measure in the clinical setting and may be helpful markers in guiding treatment decisions.

Association between thymic function and allogeneic hematopoietic stem cell transplantation outcome: results of a pediatric study

Robust T cell function recovery has been shown to be crucial in determining allogeneic hematopoietic stem cell transplantation (HSCT) outcome, and there is growing evidence that the thymus plays a central role in regulating this process. We performed a long-term analysis of the role of thymic activity recovery in a population of pediatric patients undergoing allogeneic HSCT by signal joint T cell receptor excision circle (sjTREC) quantification. In this study, characterized by a long-term follow-up (median, 72 months), we found patients with higher levels of sjTRECs before transplantation had a statistically significant reduced risk of death compared with patients with lower values (relative risk, .31; 95% confidence interval, .30 to .32; P = .02), showing this different outcome was mainly related to a reduction of relapse incidence (14% versus 43%, P = .02). Unlike previous reports, we observed no correlation between sjTREC levels and lymphocyte recovery. Moreover, we confirmed that only graft-versus-host disease influenced thymic activity after transplantation. In conclusion, our results suggest an association between pretransplantation thymic activity and the long-term outcome of pediatric patients undergoing HSCT, mainly through a reduction of relapse opportunities.

HIV-1 DNA concentrations and evolution among African HIV-1-infected children under antiretroviral treatment (ANRS 1244/1278)

OBJECTIVES

The objectives of this study were to describe the pretreatment HIV-1 DNA concentrations in children infected with HIV and to evaluate the impact of antiretroviral therapy (ART) on HIV-DNA concentrations.

METHODS

This was a retrospective analysis of all children followed up in the 'Programme Enfant Yopougon' cohort, Abidjan, Côte d'Ivoire, from 2000 to 2004, who had cryopreserved peripheral blood mononuclear cells (PBMCs) and plasma samples. HIV-DNA was measured using a real-time PCR assay. Mixed-model analysis was used to analyse the factors associated with change in HIV-DNA concentration.

RESULTS

The study included 121 children infected with HIV-1. The median age at inclusion was 6 years (IQR: 3.5-9) and children were at an advanced stage of HIV disease (46.6% and 20.3% presenting CDC stage B and CDC stage C, respectively). At baseline, the median HIV-DNA concentration was 3.4 log₁₀ copies/10(6) PBMCs (IQR: 3.1-3.6). Fifty-four children were initiated on ART during follow-up. After 24 months of ART, HIV-DNA load decreased by 0.32 (IQR: 0.08-0.57) log₁₀ copies/10(6) PBMCs. The only factor associated with the HIV-DNA decrease was a concomitant low HIV-RNA viral load result. Children with efficient ART had a 0.51 log₁₀ copies (IQR: 0.40-0.86) HIV-DNA decrease per million PBMCs.

CONCLUSIONS

HIV-DNA concentrations decreased following ART initiation in a large African paediatric cohort. This decline was exclusively associated with the decrease in ongoing replication level achieved. Our study points out that a strong adherence is needed for ART to be efficient on the viral reservoirs, and further reinforces that adherence support is also essential to diminish the reservoir.

Advances in basic and clinical immunology in 2006

This article reviews the progress in the field of basic and clinical immunology in 2006, focusing on the articles published in the Journal. The role of Toll-like receptors in the immune response was explored in detail in several articles. The knowledge gained in these investigations is being used to develop strategies that enhance the immunogenicity of vaccines to prevent infectious diseases and to have an immunomodulatory effect on allergic diseases. Other components of the innate immunity reported on were the recognition of allergens with lipid-derived motifs by CD1d-restricted T cells and the role of dendritic cells in the development of an allergic response. More than 120 primary immunodeficiencies were defined at a molecular level, and biological agents such as TNF-alpha antagonists and IFN-alpha were shown to have therapeutic use. New anti-HIV drugs that block cell entry were proven to be effective, thus offering alternative therapies to respond to the development of multidrug-resistant HIV strains. The modern understanding of immunologic concepts is helping to elucidate the mechanisms of defense against viruses, bacteria, and parasites; as a result, strategies to improve management and prevention continue to emerge.