CD95 (APO-1/Fas) expression on naive CD4(+) T cells increases with disease progression in HIV-infected children and adolescents: effect of highly active antiretroviral therapy (HAART)

Expansion of Stem Cell-Like CD4+ Memory T Cells during Acute HIV-1 Infection Is Linked to Rapid Disease Progression

Acute HIV-1 infection is characterized by high viremia and massive depletion of CD4⁺ T cells throughout all tissue compartments. During this time the latent viral reservoir is established but the dynamics of memory CD4⁺ T cell subset development, their infectability and influence on disease progression during acute HIV-1 infection has not been carefully described. We therefore investigated the dynamics of CD4⁺ T cell memory populations in the RV217 (ECHO) cohort during the acute phase of infection. Interestingly, while we found only small changes in central or effector memory compartments, we observed a profound expansion of stem cell-like memory CD4⁺ T cells (SCM) (2.7-fold; P < 0.0001). Furthermore, we demonstrated that the HIV-1 integration and replication preferentially take place in highly differentiated CD4⁺ T cells such as transitional memory (TM) and effector memory (EM) CD4⁺ T cells, while naive and less mature memory cells prove to be more resistant. Despite the relatively low frequency of productively infected SCM, we suggest that their quiescent phenotype, increased susceptibility to HIV-1 integration compared to naive cells and extensive expansion make them one of the key players in establishment and persistence of the HIV-1 reservoir. Moreover, the expansion of SCM in acute HIV-1 infection was a result of Fas upregulation on the surface of naive CD4⁺ T cells. Interestingly, the upregulation of Fas receptor and expansion of SCM in acute HIV-1 infection was associated with the early viral set point and disease progression (rho = 0.47, P = 0.02, and rho = 0.42, P = 0.041, respectively). Taken together, our data demonstrate an expansion of SCM during early acute HIV-1 infection which is associated with disease outcome.IMPORTANCE Understanding the immunopathology of acute HIV-1 infection will help to develop eradication strategies. We demonstrate here that a CD4⁺ T cell memory subset expands during acute HIV-1 infection, which is associated with disease progression.

Caspase-1 Activity in CD4 T Cells Is Downregulated Following Antiretroviral Therapy for HIV-1 Infection

Both Caspase 1-induced cell death and Caspase 3-induced cell death were reported to be the causes of CD4⁺ T cell depletion in HIV infection. We measured by flow cytometry the expression of key proteins associated with pyroptosis (Caspase 1), apoptosis (Caspase 3, Caspase 8, Caspase 9), and immune activation in peripheral T cells. The percentages of CD4⁺ T cells that expressed Caspase 1 and Caspase 3 were significantly higher in untreated human immunodeficiency virus 1 (HIV-1) patients compared with healthy control (Caspase 1: 19.40% vs. 4.65%, p = .006; Caspase 3: 12.75% vs. 4.18%, p < .001). However, the percentages of Caspase 3 in CD8⁺ T cells increased significantly, while the percentages of Caspase 1 in CD8⁺ T cells did not change significantly (Caspase 1: 3.33% vs. 1.99%, p = .821; Caspase 3: 20.35% vs 4.74%, p < .001). The percentages of HLA-DR⁺ CD38⁺ CD8⁺ T cells were positively correlated with those of Caspase 1⁺ CD4⁺ T cells, but not with those of Caspase 3⁺ CD4⁺ T cells. After highly active antiretroviral therapy, the percentages of Caspase 1, but not of Caspase 3, -expressing CD4⁺ T cells decreased to a level comparable with those of healthy controls (Caspase 1: 6.05% vs. 4.65%, p = .514; Caspase 3: 9.67% vs. 4.18%, p < .001). Our study indicated that CD4⁺ T cells experience both pyroptosis and apoptosis, while CD8⁺ T cells undergo only apoptosis in HIV-1 infection. Pyroptosis, but not apoptosis, in CD4⁺ T cells may be inhibited by effective antiretroviral therapy.

Ongoing burden of disease and mortality from HIV/CMV coinfection in Africa in the antiretroviral therapy era

Human Cytomegalovirus (CMV) is a well-recognized pathogen in the context of HIV infection, but since the roll out of ART, clinical and scientific interest in the problem of HIV/CMV coinfection has diminished. However, CMV remains a significant cofactor in HIV disease, with an influence on HIV acquisition, disease progression, morbidity, and mortality. Disease manifestations may be a result of direct interplay between the two viruses, or may arise as a secondary consequence of immune dysregulation and systemic inflammation. The problem is most relevant when the rates of coinfection are high, most notably in sub-Saharan Africa, and in children at risk of acquiring both infections early in life. Understanding the interplay between these viruses and developing strategies to diagnose, treat and prevent CMV should be a priority.

Acute cytomegalovirus infection is associated with increased frequencies of activated and apoptosis-vulnerable T cells in HIV-1-infected infants

Cytomegalovirus (CMV) coinfection is associated with infant HIV-1 disease progression and mortality. In a cohort of Kenyan HIV-infected infants, the frequencies of activated (CD38(+) HLA-DR(+)) and apoptosis-vulnerable (CD95(+) Bcl-2(-)) CD4(+) and CD8(+) T cells increased substantially during acute CMV infection. The frequency of activated CD4(+) T cells was strongly associated with both concurrent CMV coinfection (P = 0.001) and HIV-1 viral load (P = 0.05). The frequency of apoptosis-vulnerable cells was also associated with CMV coinfection in the CD4 (P = 0.02) and CD8 (P < 0.001) T cell subsets. Similar observations were made in HIV-exposed uninfected infants. CMV-induced increases in T cell activation and apoptosis may contribute to the rapid disease progression in coinfected infants.

Constitutive activation and accelerated maturation of peripheral blood T cells in healthy adults in Burkina Faso compared to Germany: the case of malaria?

OBJECTIVE

It is not exactly known how frequent exposure to Plasmodium falciparum shapes the peripheral blood T-cell population in healthy West Africans.

METHODS

The frequency of peripheral blood CD4(+) lymphocytes responding to Plasmodium falciparum merozoite surface protein 1 (PfMSP-1) by production of interferon-gamma (IFN-γ), interleukin-2 (IL-2) or tumor necrosis factor-alpha (TNF-α) was determined using a commercially available flow cytometric activation assay (FastImmune) in 17 healthy adults in Nouna, Burkina Faso. T-cell activation and maturation in peripheral blood of healthy adults in Burkina Faso (n=40) and Germany (n=20) were compared using immunophenotyping and three-colour flow cytometry.

RESULTS

Significant numbers of PfMSP-1 -specific CD4(+) lymphocytes producing IFN-γ, IL-2 and/or TNF-α were detected in 14 healthy adults in Nouna. Cytokine profiles showed predominant production of IFN-γ and TNF-α. Compared to Germans, Burkinabé showed markedly lower proportions of CCR7+ CD45RA+ naive CD4(+) cells and slightly higher frequencies of CD95(+)CD4(+) T-cells and of CD38(+) CD8(+) T-cells. The median antibody-binding capacity of CD95(dim) CD4(+) T-cells in Burkinabé was more than twice the value observed in Germans (263 vs. 108 binding sites per cell, p<0.0001).

CONCLUSIONS

We hypothesize that an IFN-γ-induced increase in the expression level of CD95 on CD4(+) lymphocytes may lower the activation threshold of resting naive CD4(+) T-cells in healthy adults living in Burkina Faso. Bystander activation of these cells deserves further study as a molecular mechanism linking strong IFN-γ responses against Plasmodium falciparum to decreased susceptibility to parasitemia observed in specific ethnic groups in West Africa.

Immune Reconstitution During the First Year of Antiretroviral Therapy of HIV-1-Infected Adults in Rural Burkina Faso

There are no data on the outcome of highly active antiretroviral therapy (HAART) in HIV-infected adults in rural Burkina Faso. We therefore assessed CD4⁺ T-cell counts and HIV-1 plasma viral load (VL), the proportion of naive T-cells (co-expressing CCR7 and CD45RA) and T-cell activation (expression of CD95 or CD38) in 61 previously untreated adult patients from Nouna, Burkina Faso, at baseline and 2 weeks, 1, 3, 6, 9 and 12 months after starting therapy. Median CD4⁺ T-cell counts increased from 174 (10^th-90^th percentile: 33-314) cells/µl at baseline to 300 (114- 505) cells/µl after 3 months and 360 (169-562) cells/µl after 12 months of HAART. Median VL decreased from 5.8 (4.6- 6.6) log10 copies/ml at baseline to 1.6 (1.6-2.3) log10 copies/ml after 12 months. Early CD4⁺ T-cell recovery was accompanied by a reduction of the expression levels of CD95 and CD38 on T-cells. Out of 42 patients with complete virological follow-up under HAART, 19 (45%) achieved concordant good immunological (gain of ≥100 CD4⁺ T-cells/µl above baseline) and virological (undetectable VL) responses after 12 months of treatment (intention-to-treat analysis). Neither a decreased expression of the T-cell activation markers CD38 and CD95, nor an increase in the percentage of naive T-cells reliably predicted good virological treatment responses in patients with good CD4⁺ T-cell reconstitution. Repeated measurement of CD4⁺ T-cell counts during HAART remains the most important parameter for immunologic monitoring. Substitution of repeated VL testing by determination of T-cell activation levels (e.g., CD38 expression on CD8⁺ T-cells) should be applied with caution.

Activation and maturation of peripheral blood T cells in HIV-1-infected and HIV-1-uninfected adults in Burkina Faso: a cross-sectional study

Background

We wanted to explore to what extent environmental exposure to immune stimulants, which is expected to be more present in rural than in urban settings, influences T cell activation and maturation in healthy and in HIV-1-infected individuals in Burkina Faso in west Africa.

Methods

The proportion of circulating naïve T cells and the expression of the T cell activation markers, CD95 and CD38, were analyzed by immunophenotyping and three-colour flow cytometry in 63 healthy individuals and 137 treatment-naïve HIV-1-infected subjects from Ouagadougou (urban setting) and 26 healthy adults and 61 treatment-naïve patients from Nouna (rural).

Results

A slightly higher activation level of CD4⁺ and CD8⁺ peripheral blood T cells was seen in healthy adults living in Nouna than in those living in Ouagadougou. The percentages of naïve CD45RA^bright CCR7⁺ T cells were not significantly different between both study sites. Taking into consideration that relatively more HIV-1-infected patients in Nouna were in an advanced disease stage, no relevant differences were seen in T cell activation and maturation between patients at both study sites. As expected, the percentage of CD95⁺ CD4⁺ and CD38⁺ CD8⁺ T cells and the respective antigen density on these cells was significantly higher in patients than in controls in both settings. The percentage of naïve CD8⁺ T cells was lower in HIV-1-infected subjects than in healthy controls irrespective of the study site, while a lower proportion of naïve CD4⁺ T cells in patients compared with controls was seen only in Nouna.

Conclusions

Environmentally triggered immune activation may contribute to the increased expression of the activation markers CD95 and CD38 on peripheral blood T cells from healthy adults living in rural versus urban settings in Burkina Faso. T cell activation is further increased in HIV-1-infected individuals due to T cell loss and high plasma viral load levels. The observed variations in T cell activation levels or the proportion of naïve T cells in our study patients, however, are not explained by differences in CD4⁺ T cell counts or HIV-1 plasma viral load levels alone.

Lymphocyte expression of CD95 at rest and in response to acute exercise in healthy children and adolescents

CD95 is essential in regulating the immune system, and its reduced expression has been associated with anthracycline resistance in some childhood leukemias. We determined whether an acute bout of exercise would influence the mixed lymphocyte expression of CD95 in healthy children and adolescents. Fifty healthy pediatric subjects (female n=25) cycled for 60 min @ 70% V O(2max). Blood was collected before, during, and after exercise to determine CD95 expression on T (CD3(+)CD19(-)) and B (CD3(-)CD19(+)) cells using flow cytometry. At rest, the percentage of CD95(hi) T cells was 29% higher in girls versus boys (p<0.001). The percentage of CD95(hi) T cells and the median fluorescence intensity (MFI) of CD95(hi) were higher during recovery versus rest (p<0.0001). The percentage of CD95(lo) T cells was lower during recovery versus rest, whereas the MFI of CD95(lo) was higher during exercise versus rest. The CD95(hi) T cell count increased during exercise, but only in 14-yr-old girls, whereas CD95(lo) T cell counts increased similarly in all groups. CD95(+) B cells were relatively unresponsive to exercise. We conclude that lymphocyte expression of CD95 is influenced by acute exercise in healthy children and adolescents. Exercise-induced alterations in CD95 expression may have clinical implications for some pediatric conditions.