SIV clearance from neonatal macaques following transient CCR5 depletion.

Treatment of people with HIV (PWH) with antiretroviral therapy (ART) results in sustained suppression of viremia, but HIV persists indefinitely as integrated provirus in CD4-expressing cells. Intact persistent provirus, the "rebound competent viral reservoir" (RCVR), is the primary obstacle to achieving a cure. Most variants of HIV enter CD4 + T cells by binding to the chemokine receptor, CCR5. The RCVR has been successfully depleted only in a handful of PWH following cytotoxic chemotherapy and bone marrow transplantation from donors with a mutation in CCR5 . Here we show that long-term SIV remission and apparent cure can be achieved for infant macaques via targeted depletion of potential reservoir cells that express CCR5. Neonatal rhesus macaques were infected with virulent SIVmac251, then treated with ART beginning one week after infection, followed by treatment with either a CCR5/CD3-bispecific or a CD4-specific antibody, both of which depleted target cells and increased the rate of plasma viremia decrease. Upon subsequent cessation of ART, three of seven animals treated with CCR5/CD3-bispecific antibody rebounded quickly and two rebounded 3 or 6 months later. Remarkably, the other two animals remained aviremic and efforts to detect replication-competent virus were unsuccessful. Our results show that bispecific antibody treatment can achieve meaningful SIV reservoir depletion and suggest that functional HIV cure might be achievable for recently infected individuals having a restricted reservoir.

Cytomegalovirus infection disrupts the influence of short-chain fatty acid producers on Treg/Th17 balance.

BACKGROUND: Both the gut microbiota and chronic viral infections have profound effects on host immunity, but interactions between these influences have been only superficially explored. Cytomegalovirus (CMV), for example, infects approximately 80% of people globally and drives significant changes in immune cells. Similarly, certain gut-resident bacteria affect T-cell development in mice and nonhuman primates. It is unknown if changes imposed by CMV on the intestinal microbiome contribute to immunologic effects of the infection. RESULTS: We show that rhesus cytomegalovirus (RhCMV) infection is associated with specific differences in gut microbiota composition, including decreased abundance of Firmicutes, and that the extent of microbial change was associated with immunologic changes including the proliferation, differentiation, and cytokine production of CD8+ T cells. Furthermore, RhCMV infection disrupted the relationship between short-chain fatty acid producers and Treg/Th17 balance observed in seronegative animals, showing that some immunologic effects of CMV are due to disruption of previously existing host-microbe relationships. CONCLUSIONS: Gut microbes have an important influence on health and disease. Diet is known to shape the microbiota, but the influence of concomitant chronic viral infections is unclear. We found that CMV influences gut microbiota composition to an extent that is correlated with immunologic changes in the host. Additionally, pre-existing correlations between immunophenotypes and gut microbes can be subverted by CMV infection. Immunologic effects of CMV infection on the host may therefore be mediated by two different mechanisms involving gut microbiota. Video Abstract.

Human Immunodeficiency Virus-1 Latency Reversal via the Induction of Early Growth Response Protein 1 to Bypass Protein Kinase C Agonist-Associated Immune Activation.

Human Immunodeficiency Virus-1 (HIV) remains a global health challenge due to the latent HIV reservoirs in people living with HIV (PLWH). Dormant yet replication competent HIV harbored in the resting CD4+ T cells cannot be purged by antiretroviral therapy (ART) alone. One approach of HIV cure is the "Kick and Kill" strategy where latency reversal agents (LRAs) have been implemented to disrupt latent HIV, expecting to eradicate HIV reservoirs by viral cytopathic effect or immune-mediated clearance. Protein Kinase C agonists (PKCa), a family of LRAs, have demonstrated the ability to disrupt latent HIV to an extent. However, the toxicity of PKCa remains a concern in vivo. Early growth response protein 1 (EGR1) is a downstream target of PKCa during latency reversal. Here, we show that PKCa induces EGR1 which directly drives Tat-dependent HIV transcription. Resveratrol, a natural phytoalexin found in grapes and various plants, induces Egr1 expression and disrupts latent HIV in several HIV latency models in vitro and in CD4+ T cells isolated from ART-suppressed PLWH ex vivo. In the primary CD4+ T cells, resveratrol does not induce immune activation at the dosage that it reverses latency, indicating that targeting EGR1 may be able to reverse latency and bypass PKCa-induced immune activation.

Cytomegalovirus mediates expansion of IL-15-responsive innate-memory cells with SIV killing function.

Interindividual immune variability is driven predominantly by environmental factors, including exposure to chronic infectious agents such as cytomegalovirus (CMV). We investigated the effects of rhesus CMV (RhCMV) on composition and function of the immune system in young macaques. Within months of infection, RhCMV was associated with impressive changes in antigen presenting cells, T cells, and NK cells-and marked expansion of innate-memory CD8+ T cells. These cells express high levels of NKG2A/C and the IL-2 and IL-15 receptor beta chain, CD122. IL-15 was sufficient to drive differentiation of the cells in vitro and in vivo. Expanded NKG2A/C+CD122+CD8+ T cells in RhCMV-infected macaques, but not their NKG2-negative counterparts, were endowed with cytotoxicity against class I-deficient K562 targets and prompt IFN-γ production in response to stimulation with IL-12 and IL-18. Because RhCMV clone 68-1 forms the viral backbone of RhCMV-vectored SIV vaccines, we also investigated immune changes following administration of RhCMV 68-1-vectored SIV vaccines. These vaccines led to impressive expansion of NKG2A/C+CD8+ T cells with capacity to inhibit SIV replication ex vivo. Thus, CMV infection and CMV-vectored vaccination drive expansion of functional innate-like CD8 cells via host IL-15 production, suggesting that innate-memory expansion could be achieved by other vaccine platforms expressing IL-15.

Transient Effect of Infant Formula Supplementation on the Intestinal Microbiota.

Breastfeeding is the gold standard for feeding infants because of its long-term benefits to health and development, but most infants in the United States are not exclusively breastfed in the first six months. We enrolled 24 infants who were either exclusively breastfed or supplemented with formula by the age of one month. We collected diet information, stool samples for evaluation of microbiotas by 16S rRNA sequencing, and blood samples for assessment of immune development by flow cytometry from birth to 6 months of age. We further typed the Bifidobacterium strains in stool samples whose 16S rRNA sequencing showed the presence of Bifidobacteriaceae. Supplementation with formula during breastfeeding transiently changed the composition of the gut microbiome, but the impact dissipated by six months of age. For example, Bifidobacterium longum, a bacterial species highly correlated with human milk consumption, was found to be significantly different only at 1 month of age but not at later time points. No immunologic differences were found to be associated with supplementation, including the development of T-cell subsets, B cells, or monocytes. These data suggest that early formula supplementation, given in addition to breast milk, has minimal lasting impact on the gut microbiome or immunity.

Disruption of latent HIV in vivo during the clearance of actinic keratosis by ingenol mebutate.

Actinic keratosis (AK) is a precancerous skin lesion that is common in HIV-positive patients. Without effective treatment, AKs can progress to squamous cell carcinoma. Ingenol mebutate, a PKC agonist, is a US Food and Drug Administration-approved (FDA-approved) topical treatment for AKs. It can induce reactivation of latent HIV transcription in CD4+ T cells both in vitro and ex vivo. Although PKC agonists are known to be potent inducers of HIV expression from latency, their effects in vivo are not known because of the concerns of toxicity. Therefore, we sought to determine the effects of topical ingenol mebutate gel on the HIV transcription profile in HIV-infected individuals with AKs, specifically in the setting of suppressive antiretroviral therapy (ART). We found that AKs cleared following topical application of ingenol mebutate and detected marginal changes in immune activation in the peripheral blood and in skin biopsies. An overall increase in the level of HIV transcription initiation, elongation, and complete transcription was detected only in skin biopsies after the treatment. Our data demonstrate that application of ingenol mebutate to AKs in ART-suppressed HIV-positive patients can effectively cure AKs as well as disrupt HIV latency in the skin tissue microenvironment in vivo without causing massive immune activation.

Paradoxical effects of obesity on T cell function during tumor progression and PD-1 checkpoint blockade.

The recent successes of immunotherapy have shifted the paradigm in cancer treatment, but because only a percentage of patients are responsive to immunotherapy, it is imperative to identify factors impacting outcome. Obesity is reaching pandemic proportions and is a major risk factor for certain malignancies, but the impact of obesity on immune responses, in general and in cancer immunotherapy, is poorly understood. Here, we demonstrate, across multiple species and tumor models, that obesity results in increased immune aging, tumor progression and PD-1-mediated T cell dysfunction which is driven, at least in part, by leptin. However, obesity is also associated with increased efficacy of PD-1/PD-L1 blockade in both tumor-bearing mice and clinical cancer patients. These findings advance our understanding of obesity-induced immune dysfunction and its consequences in cancer and highlight obesity as a biomarker for some cancer immunotherapies. These data indicate a paradoxical impact of obesity on cancer. There is heightened immune dysfunction and tumor progression but also greater anti-tumor efficacy and survival after checkpoint blockade which directly targets some of the pathways activated in obesity.

Subclinical Cytomegalovirus Infection Is Associated with Altered Host Immunity, Gut Microbiota, and Vaccine Responses.

Subclinical viral infections (SVI), including cytomegalovirus (CMV), are highly prevalent in humans, resulting in lifelong persistence. However, the impact of SVI on the interplay between the host immunity and gut microbiota in the context of environmental exposures is not well defined. We utilized the preclinical nonhuman primate (NHP) model consisting of SVI-free (specific-pathogen-free [SPF]) rhesus macaques and compared them to the animals with SVI (non-SPF) acquired through natural exposure and investigated the impact of SVI on immune cell distribution and function, as well as on gut microbiota. These changes were examined in animals housed in the outdoor environment compared to the controlled indoor environment. We report that SVI are associated with altered immune cell subsets and gut microbiota composition in animals housed in the outdoor environment. Non-SPF animals harbored a higher proportion of potential butyrate-producing Firmicutes and higher numbers of lymphocytes, effector T cells, and cytokine-producing T cells. Surprisingly, these differences diminished following their transfer to the controlled indoor environment, suggesting that non-SPFs had increased responsiveness to environmental exposures. An experimental infection of indoor SPF animals with CMV resulted in an increased abundance of butyrate-producing bacteria, validating that CMV enhanced colonization of butyrate-producing commensals. Finally, non-SPF animals displayed lower antibody responses to influenza vaccination compared to SPF animals. Our data show that subclinical CMV infection heightens host immunity and gut microbiota changes in response to environmental exposures. This may contribute to the heterogeneity in host immune response to vaccines and environmental stimuli at the population level.IMPORTANCE Humans harbor several latent viruses that modulate host immunity and commensal microbiota, thus introducing heterogeneity in their responses to pathogens, vaccines, and environmental exposures. Most of our understanding of the effect of CMV on the immune system is based on studies of children acquiring CMV or of immunocompromised humans with acute or reactivated CMV infection or in ageing individuals. The experimental mouse models are genetically inbred and are completely adapted to the indoor laboratory environment. In contrast, nonhuman primates are genetically outbred and are raised in the outdoor environment. Our study is the first to report the impact of long-term subclinical CMV infection on host immunity and gut microbiota, which is evident only in the outdoor environment but not in the indoor environment. The significance of this study is in highlighting the impact of SVI on enhancing host immune susceptibility to environmental exposures and immune heterogeneity.

HIV latency is reversed by ACSS2-driven histone crotonylation.

Eradication of HIV-1 (HIV) is hindered by stable viral reservoirs. Viral latency is epigenetically regulated. While the effects of histone acetylation and methylation at the HIV long-terminal repeat (LTR) have been described, our knowledge of the proviral epigenetic landscape is incomplete. We report that a previously unrecognized epigenetic modification of the HIV LTR, histone crotonylation, is a regulator of HIV latency. Reactivation of latent HIV was achieved following the induction of histone crotonylation through increased expression of the crotonyl-CoA-producing enzyme acyl-CoA synthetase short-chain family member 2 (ACSS2). This reprogrammed the local chromatin at the HIV LTR through increased histone acetylation and reduced histone methylation. Pharmacologic inhibition or siRNA knockdown of ACSS2 diminished histone crotonylation-induced HIV replication and reactivation. ACSS2 induction was highly synergistic in combination with either a protein kinase C agonist (PEP005) or a histone deacetylase inhibitor (vorinostat) in reactivating latent HIV. In the SIV-infected nonhuman primate model of AIDS, the expression of ACSS2 was significantly induced in intestinal mucosa in vivo, which correlated with altered fatty acid metabolism. Our study links the HIV/SIV infection-induced fatty acid enzyme ACSS2 to HIV latency and identifies histone lysine crotonylation as a novel epigenetic regulator for HIV transcription that can be targeted for HIV eradication.

Memory T Cell Proliferation before Hepatitis C Virus Therapy Predicts Antiviral Immune Responses and Treatment Success.

The contribution of the host immune system to the efficacy of new anti-hepatitis C virus (HCV) drugs is unclear. We undertook a longitudinal prospective study of 33 individuals with chronic HCV treated with combination pegylated IFN-α, ribavirin, and telaprevir/boceprevir. We characterized innate and adaptive immune cells to determine whether kinetics of the host response could predict sustained virologic response (SVR). We show that characteristics of the host immune system present before treatment were correlated with successful therapy. Augmentation of adaptive immune responses during therapy was more impressive among those achieving SVR. Most importantly, active memory T cell proliferation before therapy predicted SVR and was associated with the magnitude of the HCV-specific responses at week 12 after treatment start. After therapy initiation, the most important correlate of success was minimal monocyte activation, as predicted by previous in vitro work. In addition, subjects achieving SVR had increasing expression of the transcription factor T-bet, a driver of Th1 differentiation and cytotoxic effector cell maturation. These results show that host immune features present before treatment initiation predict SVR and eventual development of a higher frequency of functional virus-specific cells in blood. Such host characteristics may also be required for successful vaccine-mediated protection.

IL-21 Therapy Controls Immune Activation and Maintains Antiviral CD8+ T Cell Responses in Acute Simian Immunodeficiency Virus Infection.

Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) replicate during acute infection in lymphocytes of the gastrointestinal tract, before disseminating systemically. Localized replication and associated loss of gut-resident CD4+ T cells occur regardless of the portal of entry of the virus (e.g., intravenous vs. rectal). Thus, HIV and SIV are tropic for gut tissue, and their pathogenesis requires the special environment of the intestine. T helper 17 (Th17) cells are important contributors to microbial defense in the gut that are vulnerable to HIV infection and whose loss is associated with translocation of microbial products to the systemic circulation, leading to chronic immune activation and disease progression. Interleukin (IL)-21 promotes differentiation and survival of Th17 cells and stimulates CD8+ T cell function. By promoting Th17 cell survival, IL-21 could limit bacterial translocation and immune activation in the setting of acute or rebounding HIV/SIV disease. In this study, we tested the effect of recombinant IL-21-IgFc treatment, given at the time of infection, on SIVmac251 infection. We found that rIL-21-IgFc decreases immune activation and maintains effective antiviral responses by CD8+ T cells in blood, but this maintenance is not associated with lower viral loads. rIL-21-IgFc treatment also did not generally support Th17 cell populations, but Th17 cells remained strongly and independently associated with control of plasma viremia. For example, the single animal exhibiting greatest control over viremia in our study also manifested the highest levels of IL-21 in plasma, Th17 cell maintenance in blood, and Th17 cells in intestinal tissue. These findings provide rationale for further exploration of IL-21 treatment as a support for host CD8+ T cell responses in HIV cure strategies.

Depletion of Gut-Resident CCR5+ Cells for HIV Cure Strategies.

The HIV reservoir forming at the earliest stages of infection is likely composed of CCR5+ cells, because these cells are the targets of transmissible virus. Restriction of the CCR5+ reservoir, particularly in the gut, may be needed for subsequent cure attempts. Strategies for killing or depleting CCR5+ cells have been described, but none have been tested in vivo in nonhuman primates, and the extent of achievable depletion from tissues is not known. In this study we investigate the efficacy of two novel cytotoxic treatments for targeting and eliminating CCR5+ cells in young rhesus macaques. The first, an immunotoxin consisting of the endogenous CCR5 ligand RANTES fused with Pseudomonas exotoxin (RANTES-PE38), killed CCR5+ lamina propria lymphocytes (LPLs) ex vivo, but had no detectable effect on CCR5+ LPLs in vivo. The second, a primatized bispecific antibody for CCR5 and CD3, depleted all CCR5+ cells from blood and the vast majority of such cells from the colonic mucosa (up to 96% of CD4+CCR5+). Absence of CCR5-expressing cells from blood endured for at least 1 week, while CCR5+ cells in colon were substantially replenished over the same time span. These data open an avenue to investigation of combined early ART treatment and CCR5+ reservoir depletion for cure of HIV-infected infants.

Persistent effects of early infant diet and associated microbiota on the juvenile immune system.

Early infant diet has significant impacts on the gut microbiota and developing immune system. We previously showed that breast-fed and formula-fed rhesus macaques develop significantly different gut microbial communities, which in turn are associated with different immune systems in infancy. Breast-fed animals manifested greater T cell activation and proliferation and harbored robust pools of T helper 17 (TH17) cells. These differences were sustained throughout the first year of life. Here we examine groups of juvenile macaques (approximately 3 to 5 y old), which were breast-fed or formula-fed in infancy. We demonstrate that juveniles breast-fed in infancy maintain immunologic differences into the fifth year of life, principally in CD8(+) memory T cell activation. Additionally, long-term correlation networks show that breast-fed animals maintain persistent relationships between immune subsets that are not seen in formula-fed animals. These findings demonstrate that infant feeding practices have continued influence on immunity for up to 3 to 5 y after birth and also reveal mechanisms for microbial modulation of the immune system.

Breast-fed and bottle-fed infant rhesus macaques develop distinct gut microbiotas and immune systems.

Diet has a strong influence on the intestinal microbiota in both humans and animal models. It is well established that microbial colonization is required for normal development of the immune system and that specific microbial constituents prompt the differentiation or expansion of certain immune cell subsets. Nonetheless, it has been unclear how profoundly diet might shape the primate immune system or how durable the influence might be. We show that breast-fed and bottle-fed infant rhesus macaques develop markedly different immune systems, which remain different 6 months after weaning when the animals begin receiving identical diets. In particular, breast-fed infants develop robust populations of memory T cells as well as T helper 17 (TH17) cells within the memory pool, whereas bottle-fed infants do not. These findings may partly explain the variation in human susceptibility to conditions with an immune basis, as well as the variable protection against certain infectious diseases.

Maraviroc reduces the regulatory T-cell frequency in antiretroviral-naive HIV-infected subjects.

BACKGROUND: Maraviroc is the first antiretroviral (ART) drug to target a human protein, the CCR5 coreceptor; however, the mechanisms of maraviroc-associated immunomodulation in human immunodeficiency virus (HIV)-infected subjects remain to be elucidated. Regulatory T cells (Tregs) play a key role in HIV-associated immunopathology and are susceptible to maraviroc-mediated CCR5 blockade. Our aim was to evaluate the effect of maraviroc on Tregs. METHODS: We compared the effect of maraviroc-containing or -sparing combination ART (cART) on Tregs in ART-naive, HIV-infected subjects. Tregs were characterized as CD4(+)CD25(hi)FoxP3(+) on day 0, 8, and 30. Additional analysis on week 48 was performed in a subgroup of patients. The potential reduction in the frequency of Tregs among maraviroc-treated peripheral blood mononuclear cells (PBMCs) was also tested in vitro. The suppressive function of Tregs was also analyzed in maraviroc-treated Tregs. RESULTS: We found that maraviroc significantly reduced the Treg frequency in both the short term and 1 year after treatment initiation. In vitro experiments showed a dose-dependent reduction in the Treg frequency after treatment of PBMCs with maraviroc, although their in vitro suppressive function was not altered. CONCLUSIONS: These findings partially explain maraviroc-associated immunomodulatory effects and open new therapeutic expectations for the development of Treg-depleting immunotherapies.

HIV infection deregulates the balance between regulatory T cells and IL-2-producing CD4 T cells by decreasing the expression of the IL-2 receptor in Treg.

Indexation of regulatory T cells (Treg) to the number of activated T cells constitutes a homeostatic mechanism ensuring that T-cell expansion remains under control. However, immune hyperactivation observed in HIV-infected patients suggests a possible dysfunction of this mechanism. Here we show that the Treg/IL-2-producing cells' balance is deeply disturbed in viremic HIV-infected patients. We found a lower expression of IL-2 receptor alpha on Treg from viremic patients. We confirmed in vitro that HIV infection of Treg downregulates IL-2 receptor alpha and phosphorylated STAT5. Our results argue for an impaired capacity of Treg to sense the expansion of activated T cells in HIV-infected patients that could contribute to the immune deregulation.

Long-term suppressive combined antiretroviral treatment does not normalize the serum level of soluble CD14.

Levels of soluble CD14 (sCD14) were longitudinally measured in 85 human immunodeficiency virus (HIV)-infected subjects during long-term receipt of suppressive combined antiretroviral therapy (cART) and compared to those in young and elderly HIV-negative control subjects. cART did not normalize sCD14 levels; rather, the HIV-infected group displayed a significantly higher sCD14 level at baseline (ie, before cART initiation), 1 year after cART initiation, and 5 years after cART initiation, compared with both control groups. Furthermore, the baseline CD4(+) T-cell count was inversely associated with the baseline sCD14 level. Our results point to the necessity of complementary therapies to treat the activated/inflamed status associated with chronic HIV infection and to the benefits of early initiation of cART.

High prevalence of X4/DM-tropic variants in children and adolescents infected with HIV-1 by vertical transmission.

BACKGROUND: We studied HIV coreceptor tropism in vertically HIV-infected children and adolescents with the objective of predicting the proportion of children and adolescents that could be treated with CCR5 (R5) antagonists. METHODS: One hundred eighteen multidrug-resistant pediatric patients (36 children and 82 adolescents) were enrolled in a cross-sectional study. Viral tropism was assessed using the new phenotypic HIV-1 tropism coreceptor assay information and Trofile. RESULTS: Of 118 antiretroviral-experienced HIV-infected children and adolescents, 49 (57.0%) had dual-tropic and 20 (23.3%) had X4-tropic viruses by tropism coreceptor assay information testing. Only 17 (19.7%) showed R5-tropic variants. HIV-1 coreceptor usage was not detectable in 32 of 118 (27%) patients. Among 24 children and 62 adolescents with tropism coreceptor assay information results, 17 (70.8%) children and 51 (82.2%) adolescents showed viruses with dual-tropic or X4-tropic variants. Additionally, Trofile (ES) was performed in 42 of 118 patients with HIV-1 RNA > 1000 copies/mL. No patient showed X4-tropic variants; dual-tropic viruses were observed in 12 (28.6%) patients. In 6 (14.3%) patients, HIV tropism could not be determined. X4-tropic variants were more common in children (P = 0.031). CD4 T cell percentage was significantly lower in children (P = 0.011) and adolescents (P = 0.027) with R5-tropic viruses than in those with X4-tropic viruses. CONCLUSIONS: The presence of X4-tropic variants in more than 80% of our cohort of antiretroviral-experienced children and adolescents with vertical HIV-1 infection indicates a very limited role for CCR5 antagonists as part of salvage regimens for highly treatment-experienced vertically HIV-1-infected patients with extensive antiretroviral drug resistance and limited treatment options.

Detectable viral load aggravates immunosenescence features of CD8 T-cell subsets in vertically HIV-infected children.

BACKGROUND: CD8 T cells are crucial in the immune responses against HIV infection, but HIV-infected adults suffer a naive CD8 T-cell depletion and accelerated senescence caused by chronic antigen stimulation. Although HIV-infected children preserve a better immune reconstitution capacity their CD8 responses are defective. We wanted to know, whether HIV vertical transmission produces a premature aging of the CD8 population due to antigen exposition to HIV from birth and persistent chronic activation. METHODS: We conducted a multicentre cross-sectional study that compared vertically HIV-infected children with detectable (viremic) or undetectable (aviremic) viral load and age-matched healthy children. Using multiparameter flow cytometry, we studied within the CD8 population the frequencies of naive, memory, effector memory (effector memory), and TemRA subsets and measured markers of senescence, activation, and proliferation in these cells. RESULTS: We found that naive subset in viremic children was markedly decreased and had a replicative senescence phenotype. Furthermore, viremic children showed increased frequencies of memory, TEM and TemRA CD8 T cells, with a more activated and replicative senescence phenotype. We found that HIV-infected children with undetectable viral load have an increased senescence in memory and effector CD8 T cells, but the frequencies and phenotype of the CD8 subsets analyzed are comparable to healthy children. CONCLUSIONS: [corrected] Our study shows that CD8 T cells of HIV-infected children have a more senescent phenotype when compared with age-matched healthy children. Interestingly enough, our results support the importance of maintaining undetectable viral load in HIV-infected children to avoid the premature ageing and dysfunction of CD8 T cells.

Severe immune dysregulation affects CD4⁺CD25(hi)FoxP3⁺ regulatory T cells in HIV-infected patients with low-level CD4 T-cell repopulation despite suppressive highly active antiretroviral therapy.

We hypothesized that CD4(+)CD25(hi)FoxP3(+) regulatory T cells (Tregs) could be involved in the high immune activation existing in patients with low-level CD4 T-cell repopulation under suppressive high active antiretroviral therapy (hereafter, "LLR patients"). Sixteen LLR patients, 18 human immunodeficiency virus (HIV)-infected controls (hereafter, "HIV controls"), and 16 healthy subjects were included. The frequency of CD4(+)CD25(hi)FoxP3(+) and HIV-specific Treg suppressive function were assessed. Relationships between Treg and CD4/CD8 activation (HLA-DR/CD38) and the frequency of naive CD4 T-cells were assessed. Low-level patients showed a higher Treg frequency but reduced HIV-specific immunosuppressive functions than HIV controls. Whereas in healthy subjects a strong negative correlation between Tregs and activated CD8 T cells emerged (r = -0.75, P < .001), it appeared disrupted in both HIV-infected groups (r = -0.06 and P = .83 for LLR patients; r = -0.11 and P = .68 for and HIV controls). Nevertheless, in LLR patients, Tregs negatively correlated with naive CD4 T cells (r = -0.60, P = .01), whereas there was no such correlation in HIV controls (r = -0.19, P = .46) or healthy subjects (r = -0.10, P = .73). Remarkably, a higher ratio of Tregs to naive CD4 T cells was observed in LLR patients than in HIV controls (P = .001) and healthy subjects (P < .001). We conclude that LLR patients have important alterations in immunoregulation involving CD4(+)CD25(hi)FoxP3(+) Tregs. In this scenario, the role of Tregs seems to be more related to the control of the naive CD4 T-cell homeostatic proliferation, rather than to the immune activation.