CD4-CD8 Ratio

A low CD4/CD8 ratio in elderly HIV-uninfected adults is associated with increased morbidity and mortality. A subset of HIV-infected adults receiving effective antiretroviral therapy (ART) fails to normalize this ratio, even after they achieve normal CD4+ T cell counts. The immunologic and clinical characteristics of this clinical phenotype remain undefined. Using data from four distinct clinical cohorts and three clinical trials, we show that a low CD4/CD8 ratio in HIV-infected adults during otherwise effective ART (after CD4 count recovery above 500 cells/mm3) is associated with a number of immunological abnormalities, including a skewed T cell phenotype from naïve toward terminally differentiated CD8+ T cells, higher levels of CD8+ T cell activation (HLADR+CD38+) and senescence (CD28- and CD57+CD28-), and higher kynurenine/tryptophan ratio. Changes in the peripheral CD4/CD8 ratio are also reflective of changes in gut mucosa, but not in lymph nodes. In a longitudinal study, individuals who initiated ART within six months of infection had greater CD4/CD8 ratio increase compared to later initiators (>2 years). After controlling for age, gender, ART duration, nadir and CD4 count, the CD4/CD8 ratio predicted increased risk of morbidity and mortality. Hence, a persistently low CD4/CD8 ratio during otherwise effective ART is associated with increased innate and adaptive immune activation, an immunosenescent phenotype, and higher risk of morbidity/mortality. This ratio may prove useful in monitoring response to ART and could identify a unique subset of individuals needed of novel therapeutic interventions.

IntroductionAbsolute CD4 T cell count and plasma viral load have been established as predictors of HIV disease progression, and CD4 T cell count is used as an indicator for initiation of antiretroviral therapy. Following long-term therapy, patients generally present with significant CD4 T cell recovery contrasting with persistently elevated CD8 T cell counts, which leads to a partial restoration of CD4:CD8 ratio. This review focuses on the relevance of the CD4:CD8 ratio on clinical outcomes, immune dysfunction and HIV reservoir size in long-term treated patients.MethodWe conducted a comprehensive literature review of publications in English language using major electronic databases. Our search was focused on factors contributing to CD4:CD8 T cell ratio and clinical outcome in adult HIV-positive patients in the context of treated infection.DiscussionLow CD4:CD8 ratio has been linked to ageing and acts as a predictor of mortality in the general population. This ratio may represent the combined effects of inflammation and immunological changes called "inflammaging." Although the mechanisms underlying partial correction of the CD4:CD8 ratio and persistently elevated CD8 T cell count in long-term treated patients remain poorly understood, it has been recently indicated that patients with optimal CD4 T cell recovery and low CD4:CD8 ratio still harbour increased immune activation, an immune senescent phenotype and have a higher risk of non-AIDS morbidity and mortality. This review reconsiders CD4:CD8 ratio in the light of advances in the understanding of immune dysfunction and examines its pathophysiological features and implications on clinical outcome and HIV reservoir size in long-term treated HIV-positive adults.ConclusionThe CD4:CD8 ratio can contribute to the immunological evaluation of treated patients in a long-term follow-up and may be applied for monitoring both immune dysfunction and viral reservoir size in immune-based clinical trials.

BackgroundWe investigated whether CD4:CD8 ratio and CD8 count were prognostic for all-cause, AIDS, and non-AIDS mortality in virologically suppressed patients with high CD4 count.MethodsWe used data from 13 European and North American cohorts of human immunodeficiency virus-infected, antiretroviral therapy (ART)-naive adults who started ART during 1996-2010, who were followed from the date they had CD4 count ≥350 cells/μL and were virologically suppressed (baseline). We used stratified Cox models to estimate unadjusted and adjusted (for sex, people who inject drugs, ART initiation year, and baseline age, CD4 count, AIDS, duration of ART) all-cause and cause-specific mortality hazard ratios for tertiles of CD4:CD8 ratio (0-0.40, 0.41-0.64 [reference], >0.64) and CD8 count (0-760, 761-1138 [reference], >1138 cells/μL) and examined the shape of associations using cubic splines.ResultsDuring 276526 person-years, 1834 of 49865 patients died (249 AIDS-related; 1076 non-AIDS-defining; 509 unknown/unclassifiable deaths). There was little evidence that CD4:CD8 ratio was prognostic for all-cause mortality after adjustment for other factors: the adjusted hazard ratio (aHR) for lower vs middle tertile was 1.11 (95% confidence interval [CI], 1.00-1.25). The association of CD8 count with all-cause mortality was U-shaped: aHR for higher vs middle tertile was 1.13 (95% CI, 1.01-1.26). AIDS-related mortality declined with increasing CD4:CD8 ratio and decreasing CD8 count. There was little evidence that CD4:CD8 ratio or CD8 count was prognostic for non-AIDS mortality.ConclusionsIn this large cohort collaboration, the magnitude of adjusted associations of CD4:CD8 ratio or CD8 count with mortality was too small for them to be useful as independent prognostic markers in virally suppressed patients on ART.

The CD4/CD8 ratio is a pivotal metric in assessing the status of the immune system, crucially implicated in human immunodeficiency virus (HIV) infection dynamics. This review elucidates the multifaceted roles of CD4 and CD8 T cells in immune surveillance and response orchestration. We explore the intricate mechanisms governing their equilibrium and the consequential impact on immune homeostasis. Moreover, we dissect how HIV undermines this delicate balance, precipitating a cascade of immune dysregulation culminating in AIDS progression. Insights into the CD4/CD8 ratio's prognostic value for disease trajectory and treatment efficacy are discussed, highlighting its potential as a pivotal biomarker in clinical management. Additionally, it interrogates emerging therapeutic modalities leveraging the manipulation of CD4/CD8 ratios as a strategic avenue for HIV intervention. Immunomodulatory agents and gene-based approaches aimed at restoring immune balance hold promise in bolstering host defenses against HIV. By harnessing a deeper understanding of the interplay between CD4 and CD8 T cells, novel therapeutic strategies seek to fortify the immune landscape against HIV-induced immunopathogenesis. This review underscores the significance of CD4/CD8 ratios as not only diagnostic indicators but also as potential targets for therapeutic intervention, heralding new horizons in the battle against HIV/AIDS.