Delayed HIV-1 Infection of CD4+T Lymphocytes from Therapy-Naïve Patients Demonstrated by Quantification of HIV-1 DNA Copy Numbers

Cellular HIV-1 DNA levels in patients receiving antiretroviral therapy strongly correlate with therapy initiation timing but not with therapy duration

Background

Viral reservoir size refers to cellular human immunodeficiency virus-1 (HIV-1) DNA levels in CD4⁺ T lymphocytes of peripheral blood obtained from patients with plasma HIV-1-RNA levels (viral load, VL) maintained below the detection limit by antiretroviral therapy (ART). We measured HIV-1 DNA levels in CD4⁺ lymphocytes in such patients to investigate their clinical significance.

Methods

CD4⁺ T lymphocytes were isolated from the peripheral blood of 61 patients with a VL maintained at less than 50 copies/ml for at least 4 months by ART and total DNA was purified. HIV-1 DNA was quantified by nested PCR to calculate the copy number per 1 million CD4⁺ lymphocytes (relative amount) and the copy number in 1 ml of blood (absolute amount). For statistical analysis, the Spearman rank or Wilcoxon signed-rank test was used, with a significance level of 5%.

Results

CD4 cell counts at the time of sampling negatively correlated with the relative amount of HIV-1 DNA (median = 33 copies/million CD4⁺ lymphocytes; interquartile range [IQR] = 7-123 copies/million CD4⁺ lymphocytes), but were not correlated with the absolute amounts (median = 17 copies/ml; IQR = 5-67 copies/ml). Both absolute and relative amounts of HIV-1 DNA were significantly lower in six patients in whom ART was initiated before positive seroconversion than in 55 patients in whom ART was initiated in the chronic phase, as shown by Western blotting. CD4 cell counts before ART introduction were also negatively correlated with both the relative and absolute amounts of HIV-1 DNA. Only the relative amounts of HIV-1 DNA negatively correlated with the duration of VL maintenance below the detection limit, while the absolute amounts were not significantly correlated with this period.

Conclusions

The amounts of cellular HIV-1 DNA in patients with VLs maintained below the detection limit by the introduction of ART correlated with the timing of ART initiation but not with the duration of ART. In addition, CD4⁺ T lymphocytes, which were newly generated by ART, diluted latently infected cells, indicating that measurements of the relative amounts of cellular HIV-1 DNA might be underestimated.

HIV-1 DNA for the measurement of the HIV reservoir is predictive of disease progression in seroconverters whatever the mode of result expression is

BACKGROUND

HIV-1 DNA levels, reported as copies/10(6) peripheral blood mononuclear cells (PBMC), are very predictive of disease progression in seroconverters, independently of CD4(+)T cell count and HIV-RNA. Previously, HIV-DNA levels have sometimes been reported by other means: copies/10(6) CD4(+)T cells, reflecting the proportion of infected cells; or copies/mL whole blood, reflecting the global blood reservoir size.

OBJECTIVES

We investigated if the predictive value over the natural course of the disease depends on how the results are reported.

STUDY DESIGN

Results reported as HIV-DNA copies/10(6) PBMC were converted to copies/10(6) CD4(+)T cells or to copies/mL whole blood for 422 seroconverters included in the French SEROCO cohort (ANRS).

RESULTS

The three methods for reporting HIV-DNA levels yielded different ranges, but these values were highly correlated. The level of HIV-DNA during the seroconversion period was strongly associated with disease progression in all three reporting methods.

CONCLUSIONS

This reinforces the value of HIV-DNA quantification in physiopathological and therapeutical studies, particularly in an era of research aimed at diminishing the HIV reservoir. Even if blood represents a small part of this reservoir, HIV-DNA in blood is a simple marker that provides an informative picture of the global reservoir and is strongly predictive of disease progression.

New estimation method for highly sensitive quantitation of human immunodeficiency virus type 1 DNA and its application

A new estimation method for quantitation of HIV-1 DNA was established by introducing a pre-quantitation polymerase chain reaction (PCR) before conventional real-time PCR. Two alternative methods for estimating the copy number can be used: the first method utilizes the rate of beta2-microglobulin (beta2M) gene amplification during the pre-quantitation PCR, and the second utilizes a calibration curve of the crossing point of real-time PCR versus the standard HIV-1-plasmid concentration. These methods could be used to reproducibly and accurately detect a provirus density down to five copies/10(6) cells (for methods 1 and 2, inter-assay CV=17 and 16% and accuracy=81 and 92%, respectively). The levels of HIV-1 DNA could be measurable using as little as 100 microl of whole blood or buffy coat cells. Using a combination of a conventional and highly sensitive methods, we found that the amount of HIV-1 DNA ranged from 2 to 5960 copies/10(6) cells (median of 830 copies/10(6) cells) in CD4-positive T lymphocytes isolated from 30 patients responding well to highly active antiretroviral therapy (HAART). Thus, the highly sensitive method developed in this study allows estimation of the HIV-1 reservoirs in peripheral CD4-positive T lymphocytes of patients responding well to HAART.