A lower viral set point but little immunological impact after early treatment during primary HIV infection

Abstract

The Primo-SHM trial, a multicenter randomized trial comparing no treatment with 24 or 60 weeks of combination antiretroviral therapy (cART) during primary human immunodeficiency virus (HIV) infection (PHI), recently demonstrated that temporary early cART lowered the viral set point and deferred the need for re-initiation of cART during chronic HIV infection. This study examined whether the beneficial effect of early treatment was caused by preservation of immunological responses. Twenty-seven treated and 20 untreated PHI individuals participating in the Primo-SHM trial were compared at viral set point, that is, 36 weeks after baseline or after treatment interruption, respectively, for a diverse set of immunological parameters. The results show no differences between treated and untreated individuals at the level of effector T-cell formation or replication capacity of the T-cells; regulation of various T, B, natural killer, or dendritic cells; polyfunctionality of the CD8 T-cells; preservation of CD4 T-cells in the gut associated lymphoid tissue; or immune activation. There were subtle differences in the quality of the cytolytic CD4 T-cell response: 11% (median) of CD4 T-cells of the early treated individuals produced the cytolytic molecule perforin compared to 5% in untreated individuals (p=0.046), and treatment caused a modest increase in CD4 T-cells expressing both perforin and granzyme B (median 9% vs. 4% of CD4 T-cells; p=0.045). Early treatment had a modest positive effect on the quality of the CD4 T-cell response. It remains unclear, however, whether these subtle immunological differences were the cause or a result of the lower viral set point in patients who received early treatment.

FIG. 1.

Schematic overview of timeline. All immunological parameters were measured at the time of patient inclusion and randomization (baseline) and/or 36 weeks after inclusion or treatment interruption (viral load [VL] set point).

FIG. 2.

No change in T-cell subsets after early treatment. Markers of maturation (CD45RO–CD27–) and senescence (CD57+) on CD4 (A) and CD8 T-cells (B) are shown for treated (T, n=25, square), untreated (UT, n=13 for terminally differentiated and n=8 for senescent T-cells respectively, open circle), and healthy donor (HD, n=12, triangle). Dots represent individuals, with a bar at the median. **p=0.01–0.001; ***p<0.001.

FIG. 3.

Ex vivo cytolytic T-cell activity is not enhanced at viral set point after treatment. The ex vivo effector functions of CD4 (A) and CD8 T-cells (B) in terms of granzyme A, granzyme B, and perforin production in treated (n=5, square), untreated (n=8, open circle), and healthy (n=6, triangle) individuals was assessed. Individual production of granzyme B by CD4 and CD8 T-cells was assessed in a larger group of individuals (n=10, 14, and 18 for T, UT, and HD, respectively). Dots represent individuals, with a bar at the median. *p=0.05–0.01; **p=0.01–0.001; ***p=0.001–0.0001; ****p<0.0001.

FIG. 4.

Preservation of a more polyfunctional T-cell response due to treatment. PHI individuals with treatment (n=10) and no treatment (n=8) were compared. The pie charts depict the relative contribution of the number of functions, that is, cytokines/chemokines secreted, which are produced by CD8+T-cells in response to HIV gag (A). The graphs zoom in on the relative contribution of the cytokine (MIP1β, INF-γ, TNF-α, and IL-2) combinations to the total CD8 T-cell response (B). The bars represent the frequency of the CD8 T-cell response expressing the particular combination of functions shown. Each dot indicates MIP1β, INF-γ, TNF-α, and/or IL-2 positivity. In all graphs, medians (with range) are shown, and the number of functions (1 function=white; 2 functions=gray; 3 functions=dark gray; 4 functions=black) are depicted.

FIG. 5.

No changes in regulatory and inhibitory molecules after early treatment. To assess the level of inhibitory receptor expression, the % (y-axis) of inhibitory receptors on CD4 T-cells, CD8 T-cells, B-cells, natural killer (NK) cells, and dendritic cells was determined. The parameters were compared between healthy individuals (HD, n=13, black), treated individuals (T, n=8, dark gray), and untreated individuals (UT, n=10, white). Bars represent the median with range. *p=0.01–0.05; **p=0.01–0.001; ***p<0.001.

FIG. 6.

No differences in gut homing marker expression between treated and untreated patients. The expression of gut homing marker a4b7 within the T-cell compartments (naïve, central memory, effector memory, and effector) on CD4 T-cells (A) and CD8 T-cells (B) is depicted. The mean fluorescent intensity of a4b7 was compared for treated (T, n=8, light gray), untreated (UT, n=10, dark gray), and healthy (HD, n=12, black) individuals. Bars represent the median with range.*p=0.05–0.01; **p=0.01–0.001.