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HIV-1-specific cytolytic T-lymphocyte activity correlates with lower viral load, higher CD4 count, and CD8+CD38-DR-
N M Lubaki1, M E Shepherd, R S Brookmeyer
1Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Insights
Higher HIV-1 specific cytolytic T-lymphocyte (CTL) activity correlates with lower viral load in HIV-infected patients. Novel statistical methods, AUC and LR, proved superior in demonstrating this correlation compared to the standard LU20 method.
Area of Science:
- Immunology
- Virology
- Statistical Analysis
Background:
- Cytolytic T-lymphocyte (CTL) activity plays a crucial role in controlling HIV-1 replication.
- Understanding the correlation between CTL activity and viral load is essential for managing HIV infection.
- Existing statistical methods for quantifying CTL activity may have limitations.
Purpose of the Study:
- To investigate the correlation between HIV-1-specific CTL activity and plasma viral load using novel statistical methods.
- To compare the efficacy of three statistical methods (AUC, LU20, LR) in demonstrating this correlation.
- To explore the relationship between CTL activity, viral load, and T-cell activation markers.
Main Methods:
- Collected peripheral blood mononuclear cells (PBMC) from 15 HIV-infected individuals on stable antiretroviral therapy.
- Measured HIV-1-specific CTL activity using in vitro antigen stimulation.
- Quantified CTL activity with Area Under the Net HIV-specific Lysis Curve (AUC), Lytic Units (LU20), and Linear Regression (LR).
- Assessed plasma viral load and T-cell activation markers (DR, CD38) on CD4+ and CD8+ T lymphocytes.
Main Results:
- HIV-1 nef-, pol-, and gag-specific CTL activity (AUC method) was significantly higher in patients with viral load ≤30,000 copies/ml.
- Strong correlation found between higher CTL activity and lower viral load for nef, pol, and gag targets using AUC analysis (r² > 0.63, p < .001).
- Linear Regression (LR) analysis demonstrated an independent association between nef- and gag-specific CTL activity and lower viral load.
- Higher CTL activity correlated with a greater percentage of circulating CD8+DR-CD38- T lymphocytes.
Conclusions:
- Higher HIV-1-specific CTL activity is correlated with lower plasma viral load, especially in patients with CD4 counts <500 cells/mm³.
- AUC and LR statistical methods are more effective than LU20 for demonstrating the CTL activity-viral load correlation.
- The CD8+DR-CD38- T lymphocyte phenotype may represent circulating HIV-specific CD8+ CTLs.
Objectives:
The objective of this study was to use novel statistical methods to determine the correlation between HIV-1-specific cytolytic T-lymphocyte (CTL) activity and HIV-1 plasma viral load, in a blinded study of HIV-infected patients at various stages of clinical disease.
Methods:
Peripheral blood mononuclear cells (PBMC) were collected and stored at enrollment and 2 weeks later, from 15 HIV-infected individuals who were receiving stable antiretroviral therapy for the previous 6 weeks and during the study period. HIV-1-specific CTL activity was measured using an antigen-specific PBMC in vitro stimulation method. Measurements of plasma viral load, as well as CD4+ and CD8+ T lymphocytes expressing T-cell activation markers (DR and CD38) were also performed at each time point. CTL activity was quantified using three separate statistical methods: area under the net HIV-specific lysis curve (AUC), lytic units (LU20), and linear regression (LR) of net HIV-specific lysis.
Results:
HIV-1 nef-, pol- and gag-specific CTL activity (AUC method) was significantly higher in subjects with a plasma viral load < or = 30,000 RNA copies/ml, than in those with viral load >30,000 RNA copies/ml. When plasma viral load was analyzed as a continuous variable, there was a strong correlation between higher CTL activity and lower viral load for nef (r2 = .77; p < .001), pol (r2 = .63; p < .001) and gag (r2 = 0.75; p < .001) targets by the AUC, but not for the LU20 analysis. Using the LR analysis, which is less dependent on in vitro PBMC growth than the AUC analysis, an independent association was demonstrated between nef- and gag-specific CTL activity and lower viral load. Measurement of CTL activity was also significantly correlated with a higher percentage of circulating CD8+DR-CD38- T lymphocytes.
Conclusions:
In this blinded study using an in vitro stimulation of frozen PBMC, higher HIV-1 nef-, pol-, and gag-specific CTL activity correlated with lower plasma viral load, particularly in patients with a CD4 count <500 cells/mm3. Two new statistical methods for estimating CTL activity, AUC and LR analyses, were superior to the standard lytic unit (LU20) method for demonstrating this correlation. These data also demonstrated that higher circulating CD8+ T lymphocytes with a DR-CD38-phenotype, correlate with a lower plasma viral and load and higher HIV-specific CTL activity. This suggests that lymphocytes with this double-negative phenotype may include circulating HIV-specific CD8+ CTL.
