Deficiency of HIV-Gag-specific T cells in early childhood correlates with poor viral containment

Accelerated CD8+ T cell maturation in infants with perinatal HIV infection

In perinatal HIV infection, early antiretroviral therapy (ART) initiation is recommended but questions remain regarding infant immune responses to HIV and its impact on immune development. Using single cell transcriptional and phenotypic analysis we evaluated the T cell compartment at pre-ART initiation of infants with perinatally acquired HIV from Maputo, Mozambique (Towards AIDS Remission Approaches cohort). CD8+ T cell maturation subsets exhibited altered distribution in HIV exposed infected (HEI) infants relative to HIV exposed uninfected infants with reduced naive, increased effectors, higher frequencies of activated T cells, and lower frequencies of cells with markers of self-renewal. Additionally, a cluster of CD8+ T cells identified in HEI displayed gene profiles consistent with cytotoxic T lymphocytes and showed evidence for hyper expansion. Longitudinal phenotypic analysis revealed accelerated maturation of CD8+ T cells was maintained in HEI despite viral control. The results point to an HIV-directed immune response that is likely to influence reservoir establishment.

An immunoinformatics study reveals a new BoLA-DR-restricted CD4+ T cell epitopes on the Gag protein of bovine leukemia virus

Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leucosis (EBL), which has been reported worldwide. The expression of viral structural proteins: surface glycoprotein (gp51) and three core proteins - p15 (matrix), p24 (capsid), and p12 (nucleocapsid) induce a strong humoral and cellular immune response at first step of infection. CD4+ T-cell activation is generally induced by bovine leukocyte antigen (BoLA) region- positive antigen-presenting cells (APC) after processing of an exogenous viral antigen. Limited data are available on the BLV epitopes from the core proteins recognized by CD4+ T-cells. Thus, immunoinformatic analysis of Gag sequences obtained from 125 BLV isolates from Poland, Canada, Pakistan, Kazakhstan, Moldova and United States was performed to identify the presence of BoLA-DRB3 restricted CD4+ T-cell epitopes. The 379 15-mer overlapping peptides spanning the entire Gag sequence were run in BoLA-DRB3 allele-binding regions using a BoLA-DRB- peptide binding affinity prediction algorithm. The analysis identified 22 CD4+ T-cell peptide epitopes of variable length ranging from 17 to 22 amino acids. The predicted epitopes interacted with 73 different BoLA-DRB3 alleles found in BLV-infected cattle. Importantly, two epitopes were found to be linked with high proviral load in PBMC. A majority of dominant and subdominant epitopes showed high conservation across different viral strains, and therefore could be attractive targets for vaccine development.

Role of Early Life Cytotoxic T Lymphocyte and Natural Killer Cell Immunity in Paediatric HIV Cure/Remission in the Anti-Retroviral Therapy Era

Only three well-characterised cases of functional cure have been described in paediatric HIV infection over the past decade. This underlines the fact that early initiation of combination antiretroviral therapy (cART), whilst minimising the size of the viral reservoir, is insufficient to achieve cure, unless other factors contribute. In this review, we consider these additional factors that may facilitate functional cure in paediatric infection. Among the early life immune activity, these include HIV-specific cytotoxic T-lymphocyte (CTL) and natural killer (NK) cell responses. The former have less potent antiviral efficacy in paediatric compared with adult infection, and indeed, in early life, NK responses have greater impact in suppressing viral replication than CTL. This fact may contribute to a greater potential for functional cure to be achieved in paediatric versus adult infection, since post-treatment control in adults is associated less with highly potent CTL activity, and more with effective antiviral NK cell responses. Nonetheless, antiviral CTL responses can play an increasingly effective role through childhood, especially in individuals expressing then 'protective' HLA-I molecules HLA-B*27/57/58:01/8101. The role of the innate system on preventing infection, in shaping the particular viruses transmitted, and influencing outcome is discussed. The susceptibility of female fetuses to in utero mother-to-child transmission, especially in the setting of recent maternal infection, is a curiosity that also provides clues to mechanisms by which cure may be achieved, since initial findings are that viral rebound is less frequent among males who interrupt cART. The potential of broadly neutralising antibody therapy to facilitate cure in children who have received early cART is discussed. Finally, we draw attention to the impact of the changing face of the paediatric HIV epidemic on cure potential. The effect of cART is not limited to preventing AIDS and reducing the risk of transmission. cART also affects which mothers transmit. No longer are mothers who transmit those who carry genes associated with poor immune control of HIV. In the cART era, a high proportion (>70% in our South African study) of transmitting mothers are those who seroconvert in pregnancy or who for social reasons are diagnosed late in pregnancy. As a result, now, genes associated with poor immune control of HIV are not enriched in mothers who transmit HIV to their child. These changes will likely influence the effectiveness of HLA-associated immune responses and therefore cure potential among children.

Two distinct mechanisms leading to loss of virological control in the rare group of antiretroviral therapy-naïve, transiently aviraemic children living with HIV

HIV-specific CD8+ T-cells play a central role in immune control of adult HIV, but their contribution in paediatric infection is less well-characterised. Previously, we identified a group of ART-naïve children with persistently undetectable plasma viraemia, termed 'elite controllers', and a second group who achieved aviraemia only transiently. To investigate the mechanisms of failure to maintain aviraemia, we characterized in three transient aviraemics (TAs), each of whom expressed the disease-protective HLA-B*81:01, longitudinal HIV-specific T-cell activity and viral sequences. In two TAs, a CD8+ T-cell response targeting the immunodominant epitope TPQDLNTML ('Gag-TL9') was associated with viral control, followed by viral rebound and the emergence of escape variants with lower replicative capacity. Both TAs mounted variant-specific responses, but only at low functional avidity, resulting in immunological progression. By contrast, in TA-3, intermittent viraemic episodes followed aviraemia without virus escape or a diminished CD4+ T-cell count. High quality and magnitude of the CD8+ T-cell response was associated with aviraemia. We therefore identify two distinct mechanisms of loss of viral control. In one scenario, CD8+ T-cell responses initially cornered low replicative capacity escape variants, but with insufficient avidity to prevent viraemia and disease progression. In the other, loss of viral control was associated neither with virus escape nor progression, but with a decrease in the quality of the CD8+ T-cell response, followed by recovery of viral control in association with improved antiviral response. These data suggest the potential for a consistently strong and polyfunctional antiviral response to achieve long-term viral control without escape. IMPORTANCE Very early initiation of antiretroviral therapy (ART) in paediatric HIV infection offers a unique opportunity to limit the size and diversity of the viral reservoir. However, only exceptionally is ART alone sufficient to achieve remission. Additional interventions are therefore required that likely include contributions from host immunity. The HIV-specific T-cell response plays a central role in immune control of adult HIV, often mediated through protective alleles such as HLA-B*57/58:01/81:01. However, due to the tolerogenic and type 2 biased immune response in early life, HLA-I-mediated immune suppression of viraemia is seldom observed in children. We describe a rare group of HLA-B*81:01-positive, ART-naïve children who achieved aviraemia, albeit only transiently, and investigate the role of the CD8+ T-cell response in the establishment and loss of viral control. We identify a mechanism by which the HIV-specific response can achieve viraemic control without viral escape, that can be explored in strategies to achieve remission.

An HLA-I signature favouring KIR-educated Natural Killer cells mediates immune control of HIV in children and contrasts with the HLA-B-restricted CD8+ T-cell-mediated immune control in adults

Natural Killer (NK) cells contribute to HIV control in adults, but HLA-B-mediated T-cell activity has a more substantial impact on disease outcome. However, the HLA-B molecules influencing immune control in adults have less impact on paediatric infection. To investigate the contribution NK cells make to immune control, we studied >300 children living with HIV followed over two decades in South Africa. In children, HLA-B alleles associated with adult protection or disease-susceptibility did not have significant effects, whereas Bw4 (p = 0.003) and low HLA-A expression (p = 0.002) alleles were strongly associated with immunological and viral control. In a comparator adult cohort, Bw4 and HLA-A expression contributions to HIV disease outcome were dwarfed by those of protective and disease-susceptible HLA-B molecules. We next investigated the immunophenotype and effector functions of NK cells in a subset of these children using flow cytometry. Slow progression and better plasma viraemic control were also associated with high frequencies of less terminally differentiated NKG2A+NKp46+CD56dim NK cells strongly responsive to cytokine stimulation and linked with the immunogenetic signature identified. Future studies are indicated to determine whether this signature associated with immune control in early life directly facilitates functional cure in children.

Understanding Early-Life Adaptive Immunity to Guide Interventions for Pediatric Health

Infants are capable of mounting adaptive immune responses, but their ability to develop long-lasting immunity is limited. Understanding the particularities of the neonatal adaptive immune system is therefore critical to guide the design of immune-based interventions, including vaccines, in early life. In this review, we present a thorough summary of T cell, B cell, and humoral immunity in early life and discuss infant adaptive immune responses to pathogens and vaccines. We focus on the differences between T and B cell responses in early life and adulthood, which hinder the generation of long-lasting adaptive immune responses in infancy. We discuss how knowledge of early life adaptive immunity can be applied when developing vaccine strategies for this unique period of immune development. In particular, we emphasize the use of novel vaccine adjuvants and optimization of infant vaccine schedules. We also propose integrating maternal and infant immunization strategies to ensure optimal neonatal protection through passive maternal antibody transfer while avoiding hindering infant vaccine responses. Our review highlights that the infant adaptive immune system is functionally distinct and uniquely regulated compared to later life and that these particularities should be considered when designing interventions to promote pediatric health.

Birth Weight and Preterm Delivery Outcomes of Perinatally vs Nonperinatally Human Immunodeficiency Virus-Infected Pregnant Women in the United States: Results From the PHACS SMARTT Study and IMPAACT P1025 Protocol

Background

Pregnancy outcomes of perinatally human immunodeficiency virus-infected women (PHIV) are poorly defined.

Methods

We compared preterm delivery and birth weight (BW) outcomes (low BW [LBW], <2500 g), small-for-gestational-age [SGA], and BW z scores [BWZ]) in HIV-exposed uninfected infants of PHIV vs nonperinatally HIV-infected (NPHIV) pregnant women in the Pediatric HIV/AIDS Cohort Study Surveillance Monitoring of ART Toxicities or International Maternal Pediatric Adolescent AIDS Clinical Trials P1025 studies. Mixed effects models and log binomial models were used to assess the association of maternal PHIV status with infant outcomes. Age-stratified analyses were performed.

Results

From 1998 to 2013, 2270 HIV-infected pregnant women delivered 2692 newborns (270 born to PHIV and 2422 to NPHIV women). PHIV women were younger, (mean age 21 vs 25 years, P < .01) and more likely to have a pregnancy CD4 count <200 cells/mm3 (19% vs 11%, P = .01). No associations between maternal PHIV status and preterm delivery, SGA, or LBW were observed. After adjustment, BWZ was 0.12 lower in infants of PHIV vs NPHIV women (adjusted mean, -0.45 vs -0.33; P = .04). Among women aged 23-30 years (n = 1770), maternal PHIV was associated with LBW (aRR = 1.74; 95% confidence interval, 1.18, 2.58; P < .01).

Conclusion

The overall lack of association between maternal PHIV status and preterm delivery or infant BW outcomes is reassuring. The higher rates of LBW observed in PHIV women aged 23-30 years warrants further mechanism-based investigations as this is a rapidly growing and aging population worldwide.

Clinical Trials Registration

PHACS SMARTT study, NCT01310023.

Clinical Trials Registration

IMPAACT 1025, NCT00028145.

Conserved HIV-1 Gag p24 Epitopes Elicit Cellular Immune Responses That Impact Disease Outcome

Although the breadth of the human immunodeficiency virus type 1 (HIV-1)-specific cellular immune response and its impact on the control of viral replication have already been addressed, reported data have proven controversial. We hypothesize that the nature of targeted epitopes, rather than the simple breadth or magnitude of responses, correlates with disease outcome. In this study, we explore the occurrence of patterns of Gag p24 recognition among untreated HIV-1-infected patients by identifying the epitopes that compose such patterns and how they distinctly associate with disease progression. Utilizing enzyme-linked immunospot (ELISPOT) interferon gamma (IFN-γ), we screened cellular responses of 27 HIV-1-infected subjects against 15-mer peptides encompassing the whole Gag p24 protein. Obtained data were used to develop a clustering analysis that allowed definition of two groups of individuals with totally distinct patterns of recognition. Although targeted Gag p24 peptides were completely different between the two groups, the breadth and magnitude of the responses were not. Interestingly, viral control and preservation of CD4⁺ T cells were increased in one group. In addition, we compared genetic conservation of amino acid sequences of the recognized peptides, as well as of the human leucocyte antigen class I (HLA-I)-restricted epitopes within them. Subjects presenting higher control of HIV-1 replication targeted more conserved epitopes, and higher genetic variation was present mainly in anchor residues for HLA-I molecules. We strengthen the existing evidence from cases of HIV-1 infection in humans that, cellular immune responses targeting conserved epitopes, rather than the magnitude and breadth of responses, associate with a better control of viral replication and maintenance of peripheral CD4⁺ T cell counts.

Early Combination Antiretroviral Therapy Limits HIV-1 Persistence in Children

Globally, 240,000 infants are newly infected with HIV-1 each year and 3.2 million children are living with the infection. Combination antiretroviral therapy (cART) has reduced HIV-1-related disease and mortality in children but is not curative owing to the early generation of a latent reservoir of long-lived memory CD4(+) T cells bearing replication-competent HIV-1 provirus integrated into cellular DNA. This review focuses on recent advances in our understanding of the establishment of HIV-1 persistence in children and how early initiation of cART in the setting of the developing infant immune system limits the formation of the long-lived latent CD4(+) cell reservoir that remains a barrier to remission or cure.

Obstetrical, maternal characteristics and outcome of HIV-infected rapid progressor infants at Yaounde: a retrospective study

BACKGROUND

Rapid progressors are exposed to HIV infection at an early stage of life, and the prognosis is poor without treatment. Reducing the proportion of infants who are rapid progressors, require strengthening strategies to achieve the highest level of performance for the PMTCT program.

METHODS

This was a retrospective study carried out on HIV infected infants aged less than 12 months, clinically classified stage 4 (WHO) or having CD4 count <25%. We described maternal and obstetrical characteristics of HIV-infected rapid progressors using univariate and bivariate analysis. Patients' survival was monitored from the inclusion time to the end of the study. We then estimated their probability of survival with or without anti-retroviral (ARV) treatment from birth using the Kaplan-Meier method.

RESULTS

The characteristics of the mothers of the 150 rapid progressors infants we included were: low level of education (OR=3.87; P=0.016), CD4 count less than 200/mm(3) (OR=43.3; P=0.000), absence of ARV prophylaxis (OR=6.02; P=0.043), or treatment with HAART (OR=5.74; P=0.000) during pregnancy. In the children, the most important findings were lack of co-trimoxazole prophylaxis (OR=11.61; P=0.000) and antiretroviral prophylaxis (OR=2.70; P=0.0344). The survival rate was 84.3% in infants who were receiving HAART as opposed to 43.3% in those who were not (P<0.05).

CONCLUSIONS

HIV infected women who are eligible should start antiretroviral treatment prior to a pregnancy, in order to improve their immunological status. This measure associated to cotrimoxazole prophylaxis and ART could improve their survival.

Reduced frequencies of polyfunctional CMV-specific T cell responses in infants with congenital CMV infection

PURPOSE

CMV infection remains a priority for vaccine development. Vaccination of infants could modify congenital infection and provide lifetime immunity. Properties of CMV-specific T cells associated with control of viral replication in early life have not been fully defined.

METHODS

CMV-specific CD4 and CD8 T cell responses were investigated in infants with congenital CMV infection and compared to adults with primary or chronic infection. PBMC were stimulated with UL83 (pp65) or UL122 (IE-2) peptide pools then stained with antibodies to markers of T cell subset (CD4 or CD8), phenotype (CD45RA, CCR7), or function (MIP1β, CD107, IFNγ, IL2) for flow cytometry analysis.

RESULTS

Detection of CMV pp65-specific CD4 T cells was less common in infants than adults. Responder cells were primarily effector memory (EM, CD45RA-CCR7-) in adults, but mixed memory subsets in infants. Detection of CMV pp65-specific CD8 T cells did not differ between the groups, but infants had lower frequencies of total responding cells and of MIP1β- or CD107-expressing cells. Responder cells were EM or effector memory RA (CD45RA + CCR7-) in all groups. Polyfunctional T cells were less commonly detected in infants than adults. Responses to IE-2 were detected in adults but not infants. All infants had detectable circulating CMV DNA at initial study (versus 60 % of adults with primary infection) despite longer duration of CMV infection.

CONCLUSIONS

Reduced frequencies and altered functional profile of CMV-specific CD4 and CD8 T cell responses were detected in infants compared to adults, and were associated with persistent CMV DNA in peripheral blood.

Growth patterns in the first year of life differ in infants born to perinatally vs. nonperinatally HIV-infected women

OBJECTIVE

To compare the growth patterns in the first year of life between children born to perinatally HIV-infected (PHIV) vs. nonperinatally HIV-infected (NPHIV) women in the United States.

DESIGN

Retrospective cohort study of HIV-infected pregnant women who received care and delivered a live-born at two urban tertiary centers from January 2004 to March 2012.

METHODS

We collected data via chart review on demographics, behavioral risk factors, HIV clinical markers, combination antiretroviral therapy (cART), mode of HIV acquisition, pregnancy outcomes, and infant anthropometrics on study participants. Mixed-effects models were used to assess the association between maternal mode of HIV acquisition and weight-for-age z-score (WAZ), length-for-age z-score (LAZ), and weight-for-length z-score (WLZ).

RESULTS

Of the 152 pregnancies evaluated, 32 and 120 infants were born to 25 PHIV and 99 NPHIV women, respectively. Infants of PHIV women exhibited lower mean WAZ and LAZ throughout the first year of life in unadjusted analyses. After adjusting for potential confounders, the relationship between PHIV women and LAZ persisted (β = -0.54, P = 0.026). Small-for-gestational age for each birth anthropometric parameter (birth length, birth weight, and both birth length and weight) was associated with decreased LAZ (β = -0.48, P = 0.007), WAZ (β = -0.99, P < 0.001), and WLZ (β = -0.36, P = 0.027), respectively. A delivery HIV RNA level below 400 copies/ml was associated with increased WAZ and WLZ (β = 0.43, P = 0.015 and β = 0.38, P = 0.021, respectively).

CONCLUSIONS

Infants of PHIV women may remain at persistently decreased lengths throughout the first year of life. Further studies aimed at understanding intrauterine and environmental factors in PHIV women are warranted.

Immunity to HIV in Early Life

The developing immune system is adapted to the exposure to a plethora of pathogenic and non-pathogenic antigens encountered in utero and after birth, requiring a fine balance between protective immunity and immune tolerance. In early stages of life, this tolerogenic state of the innate and adaptive immune system and the lack of immunological memory render the host more susceptible to infectious pathogens like HIV. HIV pathogenesis is different in children, compared to adults, with more rapid disease progression and a substantial lack of control of viremia compared to adults. Plasma viral load remains high during infancy and only declines gradually over several years in line with immune maturation, even in rare cases where children maintain normal CD4 T-lymphocyte counts for several years without antiretroviral therapy (ART). These pediatric slow progressors also typically show low levels of immune activation despite persistently high viremia, resembling the phenotype of natural hosts of SIV infection. The lack of immunological memory places the fetus and the newborn at higher risk of infections; however, it may also provide an opportunity for unique interventions. Frequencies of central memory CD4+ T-lymphocytes, one of the main cellular reservoirs of HIV, are very low in the newborn child, so immediate ART could prevent the establishment of persistent viral reservoirs and result in "functional cure." However, as recently demonstrated in the case report of the "Mississippi child" who experienced viral rebound after more than 2 years off ART, additional immunomodulatory strategies might be required for sustained viral suppression after ART cessation. In this review, we discuss the interactions between HIV and the developing immune system in children and the potential implications for therapeutic and prophylactic interventions.

[Control of HIV infection and selection/ accumulation of HIV escape mutants by HIV-specific cytotoxic T lymphocytes (CTLs)]

HIV-specific cytotoxic T lymphocytes (CTLs) play an important role in control of HIV infection. HLA class I molecules, which mediate recognition of HIV-infected cells by the CTLs, have great diversity. Some HLA class I molecules are well known to associate with HIV control. HIV escapes from the CTLs through amino acid mutations within CTL epitopes. The rapid and extensive spread of HIV escape mutants provides accumulation of the mutants at a population level, demonstrating strong evidence of HIV adaptation to HLA class I. In this review, we discuss the role of the CTLs in controlling HIV, the relationship between HLA alleles and HIV control, and the accumulation of HIV mutants selected by the CTLs at a population level.

The impact of differential antiviral immunity in children and adults

The course of immune maturation has evolved to favour survival at each stage of development in early life. Fetal and neonatal immune adaptations facilitate intrauterine survival and provide early postnatal protection against extracellular pathogens, but they leave infants susceptible to intracellular pathogens such as viruses that are acquired perinatally. This Review focuses on three such pathogens--HIV, hepatitis B virus and cytomegalovirus--and relates the differential impact of these infections in infants and adults to the antiviral immunity that is generated at different ages. A better understanding of age-specific antiviral immunity may inform the development of integrated prevention, treatment and vaccine strategies to minimize the global disease burden resulting from these infections.

The T-cell response to HIV

HIV is a disease in which the original clinical observations of severe opportunistic infections gave the first clues regarding the underlying pathology, namely that HIV is essentially an infection of the immune system. HIV infects and deletes CD4(+) T cells that normally coordinate the adaptive T- and B-cell response to defend against intracellular pathogens. The immune defect is immediate and profound: At the time of acute infection with an AIDS virus, typically more than half of the gut-associated CD4(+) T cells are depleted, leaving a damaged immune system to contend with a life-long infection.

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.

Phylogenetic analysis of human immunodeficiency virus type 1 subtype C env gp120 sequences among four drug-naive families following subsequent heterosexual and vertical transmissions

To characterize phylogenetic relatedness of plasma HIV-1 RNA subtype C env gp120 viral variants capable of establishing an infection following heterosexual and subsequent vertical transmission events a 650-base pair fragment within the C2-V5 subregion was sequenced from four HIV-1-infected families each consisting of biological parent(s), index children (first), and subsequent (second) siblings. None of the family members had received antiretroviral therapy at the time of sample collection. Sequence alignment and analysis were done using Gene Doc, Clustal X, and MEGA software programs. Second siblings' sequences were homogeneous and clustered in a single branch while first siblings' sequences were more heterogeneous, clustering in separate branches, suggestive of more than one donor variants responsible for the infection or evolution from founder variant(s) could have occurred. While the directionality for heterosexual transmission could not be determined, homogeneous viral variants were a unique characteristic of maternal variants as opposed to the more heterogeneous paternal variants. Analysis of families' sequences demonstrated a localized expansion of the subtype C infection. We demonstrated that families' sequences clustered quite closely with other regional HIV-1 subtype C sequences supported by a bootstrap value of 86%, confirming the difficulty of classifying subtype C sequences on a geographic basis. Data are indicative of several mechanisms that may be involved in both vertical and heterosexual transmission. Larger studies are warranted to address the caveats of this study and build on the strengths. Our study could be the beginning of family-based HIV-1 intervention research in Zimbabwe.

Characterization of HIV-specific CD4+ T cell responses against peptides selected with broad population and pathogen coverage

CD4+ T cells orchestrate immunity against viral infections, but their importance in HIV infection remains controversial. Nevertheless, comprehensive studies have associated increase in breadth and functional characteristics of HIV-specific CD4+ T cells with decreased viral load. A major challenge for the identification of HIV-specific CD4+ T cells targeting broadly reactive epitopes in populations with diverse ethnic background stems from the vast genomic variation of HIV and the diversity of the host cellular immune system. Here, we describe a novel epitope selection strategy, PopCover, that aims to resolve this challenge, and identify a set of potential HLA class II-restricted HIV epitopes that in concert will provide optimal viral and host coverage. Using this selection strategy, we identified 64 putative epitopes (peptides) located in the Gag, Nef, Env, Pol and Tat protein regions of HIV. In total, 73% of the predicted peptides were found to induce HIV-specific CD4+ T cell responses. The Gag and Nef peptides induced most responses. The vast majority of the peptides (93%) had predicted restriction to the patient’s HLA alleles. Interestingly, the viral load in viremic patients was inversely correlated to the number of targeted Gag peptides. In addition, the predicted Gag peptides were found to induce broader polyfunctional CD4+ T cell responses compared to the commonly used Gag-p55 peptide pool. These results demonstrate the power of the PopCover method for the identification of broadly recognized HLA class II-restricted epitopes. All together, selection strategies, such as PopCover, might with success be used for the evaluation of antigen-specific CD4+ T cell responses and design of future vaccines.

Small for gestational age birth outcomes in pregnant women with perinatally acquired HIV

OBJECTIVE

To compare small for gestational age (SGA) birth weight in children born to women with perinatally acquired HIV (PAH) vs. those with behaviorally acquired HIV (BAH).

DESIGN

Retrospective cohort study of HIV-infected pregnant women who received care and delivered a live born at a single hospital in New York City from January 2004 to April 2011.

METHODS

We collected data via chart review on demographics, behavioral risk factors, HIV clinical markers, antiretroviral therapy (ART), mode of HIV acquisition, and pregnancy outcomes on study participants. We compared rates of these exposures among participants by method of HIV acquisition. Generalized Estimating Equation was applied to evaluate the effect of HIV acquisition type on SGA birth weight, adjusting for potential confounders.

RESULTS

Of 87 live births evaluated, 17 were born to 14 women with PAH. Overall, 20 (23%) were SGA. Eight of these SGA neonates were born preterm. Live births to women with PAH were more likely to be born SGA in our unadjusted analysis [odds ratio (OR) = 4.13, 95% confidence interval (CI) = 1.38-12.41). After adjusting for mother's age, substance use during pregnancy, nadir CD4 cell count during pregnancy, viral suppression at delivery, and second-line ART use during pregnancy, this relationship persisted with an adjusted OR of 5.7 (95% CI = 1.03-31.61).

CONCLUSION

In comparison to infants born to women with BAH, infants born to women with PAH were at high risk for compromised intrauterine growth. Future studies are warranted to determine possible causal mechanisms.

HIV-specific gag responses in early infancy correlate with clinical outcome and inversely with viral load

Many HIV-infected infants progress to AIDS during the first year of life when antiretroviral therapy (ART) is not given. The immune determinants of progression to AIDS are not known. We hypothesized that distinct HIV-specific T cell responses correlate with viral load and survival over the first year of life. Whole blood of infants at 3, 6, 9, and 12 months of age was incubated with HIV antigens Gag and Env. The frequency of specific T cells producing interferon (IFN)-γ was then measured by flow cytometry. Viral load and CD4% in HIV(+) infants were determined at each time point. ART was not available for this population at the time of sample collection. Those infants who survived to 12 months of age (n=12) had lower viral loads and higher Gag-specific CD8(+) T cell responses at 3 months, compared with infants who died (n=8). Furthermore, the frequency of Gag-specific CD4(+) T cells correlated inversely with viral load at 3 and 6 months of age. Together these data indicate that the early presence of quantitatively higher Gag-specific T cell responses in HIV-infected infants is associated with lower viral loads and decreased mortality in the first year of life. Our data support the design of a vaccine that preferentially elicits Gag responses, which may result in lower levels of viremia and possibly improve outcome.

Short communication: CD8(+) T cell polyfunctionality profiles in progressive and nonprogressive pediatric HIV type 1 infection

Pediatric HIV-1 infection is characterized by rapid disease progression and without antiretroviral therapy (ART), more than 50% of infected children die by the age of 2 years. However, a small subset of infected children progresses slowly to disease in the absence of ART. This study aimed to identify functional characteristics of HIV-1-specific T cell responses that distinguish children with rapid and slow disease progression. Fifteen perinatally HIV-infected children (eight rapid and seven slow progressors) were longitudinally studied to monitor T cell polyfunctionality. HIV-1-specific interferon (IFN)-γ(+) CD8(+) T cell responses gradually increased over time but did not differ between slow and rapid progressors. However, polyfunctional HIV-1-specific CD8(+) T cell responses, as assessed by the expression of four functions (IFN-γ, CD107a, TNF-α, MIP-1β), were higher in slow compared to rapid progressors (p=0.05) early in infection, and was associated with slower subsequent disease progression. These data suggest that the quality of the HIV-specific CD8(+) T cell response is associated with the control of disease in children as has been shown in adult infection.

Immunodominance of HIV-1 specific CD8+ T-cell responses is related to disease progression rate in vertically infected adolescents

BACKGROUND

HIV-1 vertically infected children in the USA are living into adolescence and beyond with the widespread use of antiretroviral drugs. These patients exhibit striking differences in the rate of HIV-1 disease progression which could provide insights into mechanisms of control. We hypothesized that differences in the pattern of immunodomination including breadth, magnitude and polyfunctionality of HIV-1 specific CD8+ T cell response could partially explain differences in progression rate.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we mapped, quantified, and assessed the functionality of these responses against individual HIV-1 Gag peptides in 58 HIV-1 vertically infected adolescents. Subjects were divided into two groups depending upon the rate of disease progression: adolescents with a sustained CD4%≥25 were categorized as having no immune suppression (NS), and those with CD4%≤15 categorized as having severe immune suppression (SS). We observed differences in the area of HIV-1-Gag to which the two groups made responses. In addition, subjects who expressed the HLA- B*57 or B*42 alleles were highly likely to restrict their immunodominant response through these alleles. There was a significantly higher frequency of naïve CD8+ T cells in the NS subjects (p = 0.0066) compared to the SS subjects. In contrast, there were no statistically significant differences in any other CD8+ T cell subsets. The differentiation profiles and multifunctionality of Gag-specific CD8+ T cells, regardless of immunodominance, also failed to demonstrate meaningful differences between the two groups.

CONCLUSIONS/SIGNIFICANCE

Together, these data suggest that, at least in vertically infected adolescents, the region of HIV-1-Gag targeted by CD8+ T cells and the magnitude of that response relative to other responses may have more importance on the rate of disease progression than their qualitative effector functions.

Gag-specific CD4+ T-cell responses are associated with virological control of paediatric HIV-1 infection

HIV-specific Elispot responses were investigated in 57 antiretroviral therapy-naive children, of median age 9.9 years. CD8(+) T-cell responses were detected in 96% children; Nef was the immunodominant protein. Responses broadened over time, but there was no association between magnitude, breadth or specificity of response and viraemia. Gag-specific CD4(+) T-cell responses, detectable in 26% children, correlated inversely with viraemia (R = -0.43, P < 0.001), suggesting that preservation of this cell population may be an important goal of therapeutic/vaccine strategies.

Phenotypic characterization of HIV-specific CD8+ T cells during early and chronic infant HIV-1 infection

Although CD8(+) T cells play an important role in the containment of adult HIV-1 replication, their role in infant HIV-1 infection is not as well understood. Impaired HIV-specific CD8(+) T cell responses may underlie the persistently high viral loads observed in infants. We examined the frequency and phenotype of infant HIV-specific CD8(+) T cells in 7 HIV-infected antiretroviral therapy-naïve infants during the first 2 years of life, using class I HLA tetramers and IFN-γ-ELISPOT. The frequency (0.088-3.9% of CD3(+)CD8(+) cells) and phenotype (CD27(+)CD28(-), CD45RA(+/-), CD57(+/-), HLA-DR(+), CD95(+)) of infant HIV-specific CD8(+) T cells were similar to reports in adults undergoing early infection. Unlike adults, at 23-24 months post-infection a high frequency of HIV-specific CD8(+) T cells expressed HLA-DR (mean 80%, range 68-85%) and CD95 (mean 88%, range 79-96%), suggesting sustained activation and vulnerability to apoptosis. Despite comparable expansion of HIV-specific CD8(+) T cells of a similar phenotype to adults during early infection, infant T cells failed to contain HIV-1 replication, and remained persistently activated and vulnerable to apoptosis during chronic infection.

Cellular immune responses in human immunodeficiency virus (HIV)-1-infected children: is immune restoration by highly active anti-retroviral therapy comparable to non-progression?

The objective of this study was to investigate whether the restored immune functions of vertically human immunodeficiency virus (HIV)-infected children who were severely immunodeficient before the initiation of highly active anti-retroviral therapy (HAART) are comparable to those of untreated slow progressors. We therefore assessed T cell proliferation and cytokine [interferon (IFN)-γ, interleukin (IL)-5 and IL-13] secretions after mitogen, recall antigens and HIV-1-specific stimulation in 12 untreated slow progressors, 16 untreated progressors and 18 treated patients. Treated children were profoundly immunodeficient before the initiation of HAART and had long-lasting suppression of viral replication on treatment. We demonstrated that slow progressors are characterized not only by the preservation of HIV-1-specific lymphoproliferative responses but also by the fact that these responses are clearly T helper type 1 (Th1)-polarized. Children on HAART had proliferative responses to HIV-1 p24 antigen, purified protein derivative (PPD) and tetanus antigen similar to slow progressors and higher than those of progressors. However, in contrast to slow progressors, most treated children exhibited a release of Th2 cytokines accompanying the IFN-γ secretion in response to the HIV-1 p24 antigen. Moreover, despite higher proliferative responses to phytohaemagglutinin (PHA) than the two groups of untreated children, treated children had lower levels of IFN-γ secretion in response to PHA than slow progressors. These data show that in severely immunodeficient vertically HIV-infected children, a long-lasting HAART allows recovering lymphoproliferative responses similar to untreated slow progressors. However, alterations in IFN-γ secretion in response to the mitogen PHA persisted, and their cytokine release after HIV-specific stimulation was biased towards a Th2 response.

Association of HIV diversity and survival in HIV-infected Ugandan infants

BACKGROUND

The level of viral diversity in an HIV-infected individual can change during the course of HIV infection, reflecting mutagenesis during viral replication and selection of viral variants by immune and other selective pressures. Differences in the level of viral diversity in HIV-infected infants may reflect differences in viral dynamics, immune responses, or other factors that may also influence HIV disease progression. We used a novel high resolution melting (HRM) assay to measure HIV diversity in Ugandan infants and examined the relationship between diversity and survival through 5 years of age.

METHODS

Plasma samples were obtained from 31 HIV-infected infants (HIVNET 012 trial). The HRM assay was used to measure diversity in two regions in the gag gene (Gag1 and Gag2) and one region in the pol gene (Pol).

RESULTS

HRM scores in all three regions increased with age from 6-8 weeks to 12-18 months (for Gag1: P = 0.005; for Gag2: P = 0.006; for Pol: P = 0.016). Higher HRM scores at 6-8 weeks of age (scores above the 75(th) percentile) were associated with an increased risk of death by 5 years of age (for Pol: P = 0.005; for Gag1/Gag2 (mean of two scores): P = 0.003; for Gag1/Gag2/Pol (mean of three scores): P = 0.002). We did not find an association between HRM scores and other clinical and laboratory variables.

CONCLUSIONS

Genetic diversity in HIV gag and pol measured using the HRM assay was typically low near birth and increased over time. Higher HIV diversity in these regions at 6-8 weeks of age was associated with a significantly increased risk of death by 5 years of age.

Dendritic cells reveal a broad range of MHC class I epitopes for HIV-1 in persons with suppressed viral load on antiretroviral therapy

Background

HIV-1 remains sequestered during antiretroviral therapy (ART) and can resume high-level replication upon cessation of ART or development of drug resistance. Reactivity of memory CD8⁺ T lymphocytes to HIV-1 could potentially inhibit this residual viral replication, but is largely muted by ART in relation to suppression of viral antigen burden. Dendritic cells (DC) are important for MHC class I processing and presentation of peptide epitopes to memory CD8⁺ T cells, and could potentially be targeted to activate memory CD8⁺ T cells to a broad array of HIV-1 epitopes during ART.

Principal Findings

We show for the first time that HIV-1 peptide-loaded, CD40L-matured DC from HIV-1 infected persons on ART induce IFN gamma production by CD8⁺ T cells specific for a much broader range and magnitude of Gag and Nef epitopes than do peptides without DC. The DC also reveal novel, MHC class I restricted, Gag and Nef epitopes that are able to induce polyfunctional T cells producing various combinations of IFN gamma, interleukin 2, tumor necrosis factor alpha, macrophage inhibitory protein 1 beta and the cytotoxic de-granulation molecule CD107a.

Significance

There is an underlying, broad antigenic spectrum of anti-HIV-1, memory CD8⁺ T cell reactivity in persons on ART that is revealed by DC. This supports the use of DC-based immunotherapy for HIV-1 infection.

Correlates of spontaneous viral control among long-term survivors of perinatal HIV-1 infection expressing human leukocyte antigen-B57

OBJECTIVE

We sought to identify immunologic and virologic correlates of spontaneous viral control among long-term survivors of perinatal HIV infection expressing the protective human leukocyte antigen (HLA)-B57 allele.

DESIGN

The frequency, epitope specificity, and functional attributes of HIV-specific T cells and sequence variation within B57-restricted epitopes were compared between 'spontaneous controllers' who maintained normal CD4 percentages and viral loads less than 3000 copies/ml without antiretroviral therapy, and 'treated progressors' who had initiated HAART.

METHODS

Recognition of HIV optimal epitopes was assessed by interferon gamma (IFNgamma) enzyme-linked immunosorbent spot. Functional characterization of CD8 cells targeting B57 epitopes was performed by staining for cytokine production (intracellular IFNgamma, interleukin-2, tumor necrosis factor alpha) and degranulation. Sequencing of autologous RNA was performed to determine the prevalence of viral escape mutations within B57-restricted epitopes and associated compensatory mutations.

RESULTS

HLA-B57 remained immunodominant during chronic infection in both controllers and progressors, but controllers recognized fewer epitopes and targeted epitopes within Gag and reverse transcriptase only, whereas progressors demonstrated a broader response targeting additional proteins. No individual epitope was targeted more frequently by spontaneous controllers. CD8 cytokine production patterns were heterogeneous among individuals and even among different epitopes in the same individual and did not correlate with spontaneous viral control. Extensive sequence variation within B57 epitopes was observed in both groups, but only progressors displayed additional capsid mutations that are known to offset the viral fitness cost of B57-driven immune escape.

CONCLUSION

Among HLA-B57-positive long-term survivors, spontaneous control of viremia is not associated with a qualitatively or quantitatively superior T-cell response, but with uncompensated fitness-attenuating mutations in the viral capsid.

Replicative capacity of human immunodeficiency virus type 1 transmitted from mother to child is associated with pediatric disease progression rate

Human immunodeficiency virus (HIV)-infected infants in the developing world typically progress to AIDS or death within the first 2 years of life. However, a minority progress relatively slowly. This study addresses the potential contribution of viral factors to HIV disease progression in eight infants selected from a well-characterized cohort of C clade HIV-infected infants, monitored prospectively from birth in Durban, South Africa. Three infants were defined as "progressors," and five were defined as "slow progressors." We observed that slow-progressor infants carry HIV isolates with significantly lower replicative capacity compared to virus from progressors. Furthermore, our data suggest a link between the attenuated viral phenotype and HLA-B* 57/5801 epitope-specific Gag mutational patterns of the transmitted virus and not to coreceptor usage or to the presence of Nef deletions or insertions. These data underline the importance of virus-host interactions and highlight the contribution of viral attenuation through Gag-specific CD8(+) T-cell escape mutations, among other factors, in the control of pediatric HIV infection.

Effective simian immunodeficiency virus-specific CD8+ T cells lack an easily detectable, shared characteristic

The immune correlates of human/simian immunodeficiency virus control remain elusive. While CD8(+) T lymphocytes likely play a major role in reducing peak viremia and maintaining viral control in the chronic phase, the relative antiviral efficacy of individual virus-specific effector populations is unknown. Conventional assays measure cytokine secretion of virus-specific CD8(+) T cells after cognate peptide recognition. Cytokine secretion, however, does not always directly translate into antiviral efficacy. Recently developed suppression assays assess the efficiency of virus-specific CD8(+) T cells to control viral replication, but these assays often use cell lines or clones. We therefore designed a novel virus production assay to test the ability of freshly ex vivo-sorted simian immunodeficiency virus (SIV)-specific CD8(+) T cells to suppress viral replication from SIVmac239-infected CD4(+) T cells. Using this assay, we established an antiviral hierarchy when we compared CD8(+) T cells specific for 12 different epitopes. Antiviral efficacy was unrelated to the disease status of each animal, the protein from which the tested epitopes were derived, or the major histocompatibility complex (MHC) class I restriction of the tested epitopes. Additionally, there was no correlation with the ability to suppress viral replication and epitope avidity, epitope affinity, CD8(+) T-cell cytokine multifunctionality, the percentage of central and effector memory cell populations, or the expression of PD-1. The ability of virus-specific CD8(+) T cells to suppress viral replication therefore cannot be determined using conventional assays. Our results suggest that a single definitive correlate of immune control may not exist; rather, a successful CD8(+) T-cell response may be comprised of several factors.