A Human Immunodeficiency Virus Controller With a Large Population of CD4(+)CD8(+) Double-Positive T Cells.

Human immunodeficiency virus (HIV) controllers are patients who control viral replication without antiretroviral therapy. We present the case of an HIV controller who had CD4 and CD8 coexpressed on 40% of his T cells. Although a recent study found that double-positive T cells had superior antiviral capacity in HIV-1 controllers, in this case, the CD4(+)CD8(+) T cells did not have strong antiviral activity.

Human immunodeficiency virus (HIV) controllers are patients who control viral replication without antiretroviral therapy [1]. We present the case of an HIV controller who had CD4 and CD8 coexpressed on 40% of his T cells. Although a recent study found that double-positive T cells had superior antiviral capacity in HIV-1 controllers [2], in this case, the CD4+CD8+ T cells did not have strong antiviral activity.

CASE PRESENTATION

The patient is a 62-year-old African American male with human immunodeficiency virus (HIV) infection diagnosed 12 years ago. His CD4 count was 711 cells/µL, and his viral load was 141 copies/mL plasma without antiretroviral therapy (ART) at diagnosis. His viral load remained undetectable to low (<400 copies/mL), and although his absolute CD4 count was very high, his CD4+ T cell percentage was low and his CD8+ T cell percentage was elevated (Figure 1A). At year 3, it was noted that 26% of lymphocytes coexpressed CD4 and CD8 and the proportion eventually peaked at 40%. These cells were not reported before year 3, but the aggregate percentage of CD4+ and CD8+ T cells exceeded 100%, suggesting that CD4+CD8+ cells had always been present. A malignancy workup included a polymerase chain reaction (PCR) for clonal T cell rearrangement (negative), fluorescent in situ hybridization for B-cell chronic lymphocytic leukemia (negative), and cytogenetics (normal chromosomes). Human T-lymphotropic virus type-1 serology was negative.

Figure 1.

Percentage of different T cell populations over time in the subject (A). Flow cytometry showing the large population of CD4+CD8+ T cells (B). Comparison of activated (C) and effector memory (EM; D) CD8+ T cells in the subject compared with healthy donors (HD), untreated viremic patients, patients on antiretroviral therapy (ART), and human immunodeficiency virus controllers (HC). The percentage of CD4+CD8+ T cells was too low in the other patients for a meaningful comparison to be performed. Percentage of cells that expressed interferon-γ or tumor necrosis factor-α alone or in combination after stimulation with anti-CD3 and anti-CD28 monoclonal antibodies.

Flow cytometry showed that the density of CD4 was lower on CD4+CD8+ T cells than on CD4+ T cells (Figure 1B). Because HIV infection results in down-regulation of CD4, we measured the frequency of HIV infection with semiquantitative PCR. Infection was detected in 0.01% of CD4+ T cells but <0.001% of CD4+CD8+ cells (Table 1); therefore, double-positive cells were not a major infection target. Consistent with this finding, expression of CCR5 and CXCR4 was lower in CD4+CD8+ T cells than in CD4+ T cells, and there was less viral entry of CD4+CD8+ T cells than CD4+ T cells after spinoculation with CCR5-tropic and CXCR4-tropic viruses (Table 1).

Table 1.

Features of T Cell Subsets

	CD4+ T Cells	CD8+ T Cells	CD4+CD8+ T Cells
T cell phenotype
Activated (CD38+/HLA-DR+)	8%	49%	53%
Naive (CCR7+/CD45RA+)	9%	2%	1%
Terminal Effector (CCR7−/CD45RA+)	0%	18%	2%
Central memory (CCR7+/CD45RA−)	31%	2%	1%
Effector memory (CCR7−/CD45RA−)	18%	35%	55%
HIV-1 susceptibility
% infected cells (PCR analysis)	0.01%	NA	<0.001%
CCR5 positive	35%	25%	15%
CXCR4 positive	88%	59%	76%
% CCR5-tropic virus entry	27%	0.3%	6%
% CXCR4-tropic virus entry	20%	0.4%	7%
Polyclonal T cell responses
IFN-γ and/or TNF-α expression: Unstimulated cells	0%	0.5%	0.4%
IFN-γ and/or TNF-α expression: PHA-stimulated cells	11.9%	30.4%	44.8%
IFN-γ and/or TNF-α expression: CD3/CD28-stimulated cells	25.9%	40.9%	39.1%
IFN-γ and/or TNF-α expression: PMA/ionomycin-stimulated cells	72.5%	78.3%	69.4%
HIV-1-specific responses
TNF-α expression: Unstimulated cells	0.4%	0.1%	0.1%
TNF-α expression: Gag-stimulated cells	5.2%	7%	6.1%
TNF-α, IFN-γ, IL-2 expression: Gag-stimulated cells	<0.1%	<0.1%	<0.1%
% Inhibition of HIV-1 replication: Day 5	NA	29%	0%

Abbreviations: HIV, human immunodeficiency virus; IFN, interferon; IL, interleukin; NA, not applicable; PCR, polymerase chain reaction; PHA, phytohemagglutinin; PMA, phorbol 12-myristate 13-acetate; TNF, tumor necrosis factor.

A much larger fraction of CD8+ and CD4+CD8+ T cells was activated compared with CD4+ T cells as measured by HLA-DR/CD38+ expression (Table 1). The percentage of activated CD8+ T cells was comparable to that seen in untreated individuals and higher than that in treated patients, HIV controllers, and uninfected individuals (Figure 1C).

CD4+CD8+ and CD8+ T cell fractions contained high levels of effector memory cells (Table 1) that exceeded the percentage seen in healthy donor and HIV-infected subjects (Figure 1D). The CD4+CD8+ T cells, CD4+ T cells and CD8+ T cell produced comparable levels of cytokines in response to polyclonal stimulation (Table 1), but the pattern of the cytokine production in CD4+CD8+ T cells was more similar to CD8+ T cells than CD4+ T cells (Figure 1E). To determine whether the cells were HIV-1 specific, they were stimulated with HIV-1 antigens. A similar proportion of all 3 cell populations expressed TNF-α in response to stimulation with Gag peptides (Table 1). In contrast to a prior study in which CD4+CD8+ T cells were often multifunctional [2], <0.1% of CD4+, CD8+, and CD4+CD8+ simultaneously expressed TNF-α, IFN-γ, and IL-2 (Table 1). Furthermore, although CD8+ T cells had a modest inhibitory effect on viral replication, CD4+CD8+ T had no detectable effect (Table 1).

CONCLUSIONS

We present the case of an HIV controller with a very large, persistent population of CD4+CD8+ T cells (15%–40%). There is a prior report of an HIV-infected individual with progressive disease who had elevated CD4+CD8+ T cells (approximately 7.5%) over 8 years [3]. In that case, CD4+CD8+ T cells had a low CD8 density and were phenotypically similar to CD4+ cells, whereas in our case, the CD4+CD8+ T cells are similar to CD8+ T cells based on the cytokine expression pattern and activation and memory markers. Although some studies suggest that CD4+CD8+ T cells have enhanced antiviral activity [2, 4], this was not observed here.

Although we were not able to determine the etiology of the mutual expression of CD4 and CD8 on T cells, flow cytometry revealed that the majority of these CD4+CD8+ T cells were effector memory cells with an activated phenotype. Human immunodeficiency virus controllers generally have higher levels of activated CD8+ T cells [5], elevated inflammatory biomarkers [6, 7], and higher rates of atherosclerosis [8, 9] compared with treated and uninfected individuals. The significance of this inflammation is an active area of investigation. A recent study reported HIV controllers have higher rates of hospitalization than treated patients [10]. Preliminary studies suggest that ART decreases immune activation in some HIV controllers [11-13]. Randomized controlled trials are needed to determine the impact of ART and/or anti-inflammatory treatment in HIV controllers.