Dynamics of regulatory T-cells during pregnancy: effect of HIV infection and correlations with other immune parameters

Abstract

Objectives: Regulatory T cells (Treg) increase in the context of HIV infection and pregnancy. We studied Treg subpopulations in HIV-infected and uninfected women during pregnancy and their relationship with inflammation, activation and cell-mediated immunity (CMI).

Design and methods: Blood obtained from 20 HIV-infected and 18 uninfected women during early and late gestation was used to measure Treg and activated T cells (Tact) by flow cytometry; plasma cytokines and inflammatory markers by ELISA and chemoluminescence; and CMI against varicella-zoster virus (VZV) by lymphocyte proliferation.

Results and conclusions: Compared with uninfected women, HIV-infected participants had higher frequencies of Treg subpopulations in early pregnancy, including CD4+CD25+FoxP3+%, CD8+CD25+FoxP3+%, CD4+TGFβ+% and CD4+IL10+%. In contrast, Treg frequencies were lower during late pregnancy in HIV-infected compared with uninfected women, including CD8+TGFβ+%, CD4+CTLA4+% and CD8+CTLA4+%. VZV-CMI, which was lower in HIV-infected compared with uninfected pregnant women, was inversely correlated with CD4+FoxP3+%, CD8+FoxP3+% and CD8+TGFβ+% in HIV-infected, but not in uninfected pregnant women. β₂-microglobulin, neopterin, IL1, IL4, IL8, IL10, IFNγ and TNFα plasma concentrations as well as Tact were higher in HIV-infected compared with uninfected women throughout pregnancy. In HIV-infected, but not in uninfected women, inflammatory, Th1, Th2 and regulatory cytokines increased with higher Treg%, suggesting that inflammation and regulation have a common pathophysiologic origin in the context of HIV infection. In HIV-infected and more commonly in uninfected pregnant women, higher Treg% correlated with lower Tact%. We conclude that Treg have different dynamics during pregnancy in HIV-infected and uninfected women. Higher levels of inflammatory cytokines and lower Treg% during late pregnancy in HIV-infected women may contribute to their increased incidence of maternal-fetal morbidity.

Figure 1. Proportions of Treg in HIV-infected and uninfected women during early and late gestation.

Bars represent means and standard error of the mean (SEM) of data generated by flow cytometric analysis of freshly thawed PBMC. The Treg are expressed as a percentage of the parent CD4+ or CD8+ T cell population. The graph titles indicate the Treg subpopulation depicted in each graph. Significant or marginally significant differences between HIV-infected and uninfected women are indicated by p values immediately above each time point (Mann Whitney). Horizontal lines indicate significant or marginally significant changes between early and late pregnancy. Such changes were detected only in uninfected women.

Figure 2. Cell-mediated immunity in HIV-infected and uninfected pregnant women during early and late gestation.

Data were generated using VZV- and mock-stimulated cryopreserved PBMC. Bars represent means and SEM of adjusted VZV-specific counts-per-minute (cpm) after subtraction of mock-stimulated cpm. Significant differences between HIV-infected and uninfected women at each time point are indicated by the p values on the graph (unpaired T test using log-transformed data).

Figure 3. Inflammatory factors and other cytokines in HIV-infected and uninfected women during early and late gestation.

Bars represent means and SEM. The analytes are indicated in the graph titles. Significant differences between HIV-infected and uninfected women are indicated by the p values immediately above the bars (Mann Whitney).

Figure 4. Proportions of Tact in HIV-infected and uninfected women during early and late gestation.

Bars indicate mean and SEM proportions of the Tact subpopulations indicated in the title of each graph. Tact are expressed as percentages of the parent CD4+ or CD8+ T cell populations. Significant differences between HIV-infected and uninfected women are indicated by p values immediately above each time point (Mann Whitney test).