Developing and testing a web-based platform for antiretroviral therapy (ART) adherence support among adolescents and young adults (AYA) living with HIV

Objective

Describe the development and testing of a web-based platform for antiretroviral treatment (ART) adherence support among HIV+ adolescents and young adults (AYA) in a randomized controlled trial (RCT).

Methods

A seven-member multi-disciplinary team operationalized the flat, password protected, web-based platform. Manualized protocols guided the objectives and content for each of the eight web-based sessions. Team members evaluated usability and content validity. Client satisfaction and perceived ease of use was evaluated with the first ten HIV+ AYA participants.

Results

The web-based platform was developed, evaluated, refined, implemented and pilot tested between September 2020 to April 2022. Usability was rated as high; the evaluation of content validity showed an excellent fit between session content and objectives. HIV+ AYA participants (mean age = 24.2 years) were satisfied with the quality, type, and amount of support/education received, and found the platform easy to use, operate, and navigate. Average time spent per session was 6.5 min.

Conclusion

Findings support the usability, validity, acceptability, and feasibility of this web-based platform for ART adherence support among HIV+ AYA.

Innovation

Our research and findings are responsive to research gaps and the need for transparency in the methodological development and testing of web-based control arms for ART adherence support among HIV+ AYA.

Feasibility and Acceptability of the Adherence Connection Counseling, Education, and Support (ACCESS) Proof of Concept: A Peer-Led, Mobile Health (mHealth) Cognitive Behavioral Antiretroviral Therapy (ART) Adherence Intervention for HIV-Infected (HIV+) Adolescents and Young Adults (AYA)

Effective antiretroviral therapy (ART) adherence strategies for HIV+ adolescents and young adults (AYA) are needed to prevent HIV-related morbidity, mortality, and onward transmission. In the Adherence Connection for Counseling, Education, and Support (ACCESS) pilot, an exploratory sequential mixed-methods design was used to develop and test a peer-led, mobile health (mHealth) cognitive behavioral ART adherence intervention. HIV+ AYA (ages 16-29 years) with unsuppressed plasma HIV RNA (HIV viral load) were eligible for this five-session intervention directed to improving ART adherence and HIV viral load. A total of 78 peer-led remote videoconferencing sessions (via WebEx) were delivered to 16 participants. High completion rates (97.5%) and client satisfaction scores (mean = 29.13 of 32; SD = 2.45) were observed. Self-reported ART adherence improved (32% increase in doses taken; 95th CI 11.2-53.3) with an annualized average rate of 47.5% (0.28 log₁₀) reduction in HIV viral load. We established proof of concept for the ACCESS peer-led, mHealth cognitive behavioral ART adherence intervention, with promising adherence and virologic outcome data.

Internationally Acquired Severe Systemic Infections in Febrile Pediatric Travelers Presenting to the Emergency Department

OBJECTIVES

Most children in the United States who visit the emergency department (ED) with fever have minor illnesses not requiring treatment or hospitalization. However, when a child has recently immigrated or traveled abroad, internationally acquired severe systemic infections (ISSIs) must be considered. We sought to describe children who have traveled internationally and present to the ED with a complaint of fever and to determine risk factors associated with ISSIs in these patients.

METHODS

We conducted a retrospective study of children younger than 18 years who presented to 2 pediatric EDs in Bronx, NY (June 2007 to May 2017). Patients were included if they had both fever within 24 hours and international travel within 30 days. We compared groups using bivariate analyses and created a prediction model for ISSIs using multivariable logistic regression.

RESULTS

Of the 353 children included, 44 (12%) had ISSI: 25 (57%), malaria; 6 (14%), dengue; and 13 (30%), bacteremia. Eight (18%) of those with ISSI presented with fever to another medical provider in the week prior but did not receive bloodwork. Four variables were independently associated with ISSIs: headache (odds ratio [OR], 21.7; 95% confidence interval [CI], 6.8-69.3), travel to Africa or Asia (OR, 18.8; 95% CI, 4.8-73.2), platelets of 150,000/μL or less (OR, 15.1; 95% CI, 4.7-48.6), and alanine aminotransferase level of 30 IU/L or greater (OR, 8.9; 95% CI, 3.1-25.3).

CONCLUSIONS

Children who travel internationally and present with fever upon return are at substantial risk for developing ISSIs. The diagnosis of ISSIs is often overlooked, but certain risk factors have the potential to aid clinicians.

Restriction Factor Expression in Vertically Infected Children Living With HIV-1

INTRODUCTION

Around 1.7 million children are estimated to live with HIV-1 worldwide, and about 160,000 infants are newly infected every year. Since adaptive immunity takes time to mature and develop in infants, and maternal antibodies provide limited antiviral activity, innate and intrinsic immunity against HIV-1 in the young is of critical importance. Intrinsic restriction factors are cellular proteins that effectively inhibit HIV-1 replication in vitro, but there is limited understanding of their role in vivo, and little to no data has been reported on the expression of host restriction factors in children. We hypothesized that restriction factor expression might be particularly important in children living with HIV-1 and correlate with disease progression.

METHODS

We analyzed gene expression of APOBEC3A, APOBEC3C, APOBEC3G, APOBEC3H, SAMHD1, ISG15, CDKN1A, MX2, TRIM5, and SLFN11 by qPCR in 121 samples of CD4+ T cells from vertically infected children living with HIV-1. Cell surface expression of BST-2/tetherin and markers of CD4+ T-cell activation were analyzed by flow cytometry.

RESULTS

After adjusting for gender and age, BST-2/tetherin expression on CD4+ T cells showed significant positive correlation with viral load (P = 0.0006; ρ = 0.33), CD4+ T-cell activation (P < 0.0001; ρ = 0.53), CD8+ T-cell activation (P < 0.0001; ρ = 0.53), and a negative correlation with CD4+ T-cell counts (P = 0.0008; ρ = -0.33). The expression of SAMHD1 correlated negatively with markers of T-cell activation (P = 0.046; ρ = -0.22).

DISCUSSION

These results suggest an important role of some restriction factors in the pathogenesis of HIV-1 in children.

MAIT cells are activated in acute Dengue virus infection and after in vitro Zika virus infection

Dengue virus (DENV) and Zika virus (ZIKV) are members of the Flaviviridae and are predominantly transmitted via mosquito bites. Both viruses are responsible for a growing number of infections in tropical and subtropical regions. DENV infection can cause lethargy with severe morbidity and dengue shock syndrome leading to death in some cases. ZIKV is now linked with Guillain-Barré syndrome and fetal malformations including microcephaly and developmental disorders (congenital Zika syndrome). The protective and pathogenic roles played by the immune response in these infections is unknown. Mucosal-associated invariant T (MAIT) cells are a population of innate T cells with potent anti-bacterial activity. MAIT cells have also been postulated to play a role in the immune response to viral infections. In this study, we evaluated MAIT cell frequency, phenotype, and function in samples from subjects with acute and convalescent DENV infection. We found that in acute DENV infection, MAIT cells had elevated co-expression of the activation markers CD38 and HLA-DR and had a poor IFNγ response following bacterial stimulation. Furthermore, we found that MAIT cells can produce IFNγ in response to in vitro infection with ZIKV. This MAIT cell response was independent of MR1, but dependent on IL-12 and IL-18. Our results suggest that MAIT cells may play an important role in the immune response to Flavivirus infections.

Antiretroviral therapy in HIV-infected adolescents: clinical and pharmacologic challenges

INTRODUCTION

With the currently available combined antiretroviral therapy regimens, durable suppression of viral replication, preservation of immune function and normalizing life expectancy, are all becoming achievable goals. Teenagers and young adults living with HIV present unique clinical and pharmacologic challenges to optimizing antiretroviral treatment outcomes. Areas covered: In this expert review of the topic, we examine recent clinical trial data and draw on our program's 25 year experience working with both perinatally and behaviorally HIV infected adolescents. Expert commentary: In order to be effective, the antiretrovirals we provide must be combined with multidisciplinary interventions and ongoing socio-behavioral support to ensure treatment adherence and prevent the emergence of viral resistance.

HIV-1 drug resistance prevalence, drug susceptibility and variant characterization in the Jacobi Medical Center paediatric cohort, Bronx, NY, USA

OBJECTIVES

With the advent of combined antiretroviral therapy (cART), perinatally HIV-infected children are surviving into adolescence and beyond. However, drug resistance mutations (DRMs) compromise viral control, affecting the long-term effectiveness of ART. The aims of this study were to detect and identify DRMs in a HIV-1 infected paediatric cohort.

METHODS

Paired plasma and dried blood spots (DBSs) specimens were obtained from HIV-1 perinatally infected patients attending the Jacobi Medical Center, New York, USA. Clinical, virological and immunological data for these patients were analysed. HIV-1 pol sequences were generated from samples to identify DRMs according to the International AIDS Society (IAS) 2011 list.

RESULTS

Forty-seven perinatally infected patients were selected, with a median age of 17.7 years, of whom 97.4% were carrying subtype B. They had a mean viral load of 3143 HIV-1 RNA copies/mL and a mean CD4 count of 486 cells/μL at the time of sampling. Nineteen patients (40.4%) had achieved undetectable viraemia (< 50 copies/mL) and 40.5% had a CD4 count of > 500 cells/μL. Most of the patients (97.9%) had received cART, including protease inhibitor (PI)-based regimens in 59.6% of cases. The DRM prevalence was 54.1, 27.6 and 27.0% for nucleoside reverse transcriptase inhibitors (NRTIs), PIs and nonnucleoside reverse transcriptase inhibitors (NNRTIs), respectively. Almost two-thirds (64.9%) of the patients harboured DRMs to at least one drug class and 5.4% were triple resistant. The mean nucleotide similarity between plasma and DBS sequences was 97.9%. Identical DRM profiles were present in 60% of plasma-DBS paired sequences. A total of 30 DRMs were detected in plasma and 26 in DBSs, with 23 present in both.

CONCLUSIONS

Although more perinatally HIV-1-infected children are reaching adulthood as a result of advances in cART, our study cohort presented a high prevalence of resistant viruses, especially viruses resistant to NRTIs. DBS specimens can be used for DRM detection.

Impact of HIV-1 infection and pregnancy on maternal health: comparison between perinatally and behaviorally infected young women

Background

The introduction of combination antiretroviral therapy has resulted in improved survival and quality of life for individuals infected with the human immunodeficiency virus (HIV). There is, as expected, a growing population of perinatally HIV-infected women who are, have been, or will become pregnant. We describe a large cohort of perinatally infected women, compare it with a similar age-matched behaviorally HIV-infected group, and examine factors affecting maternal and infant health.

Methods

We reviewed the records of 30 perinatally infected women who gave birth at two hospitals between January 2000 and December 2011. The comparison group comprised behaviorally infected women who delivered at these hospitals during the same period. The outcome measures were differences in CD4 counts and viral load between the cohorts, and comparisons of maternal morbidity, mortality, and mother-to-child HIV transmission.

Results

Median CD4 counts were significantly lower in the perinatal group before, during, and after pregnancy. The median viral load was significantly higher in the perinatal group. Interval prepregnancy to post partum viral load decline was also greater in the behavioral group. Viral load decreases in the perinatal population were not sustained in the post partum period, at which time viral load trended back to prepregnancy levels. There was one mother-to-child HIV transmission in a perinatally infected woman. Over an extended 4 years of follow-up, there were four deaths in the perinatal group and none in the behavioral group.

Conclusion

After delivery, the differences between perinatally and behaviorally infected mothers accentuate, with immunologic deterioration in the former group. The perinatal population may require novel management strategies to ensure outcomes comparable with those observed in the behavioral group.

Age-related expansion of Tim-3 expressing T cells in vertically HIV-1 infected children

As perinatally HIV-1-infected children grow into adolescents and young adults, they are increasingly burdened with the long-term consequences of chronic HIV-1 infection, with long-term morbidity due to inadequate immunity. In progressive HIV-1 infection in horizontally infected adults, inflammation, T cell activation, and perturbed T cell differentiation lead to an "immune exhaustion", with decline in T cell effector functions. T effector cells develop an increased expression of CD57 and loss of CD28, with an increase in co-inhibitory receptors such as PD-1 and Tim-3. Very little is known about HIV-1 induced T cell dysfunction in vertical infection. In two perinatally antiretroviral drug treated HIV-1-infected groups with median ages of 11.2 yr and 18.5 yr, matched for viral load, we found no difference in the proportion of senescent CD28(-)CD57(+)CD8(+) T cells between the groups. However, the frequency of Tim-3(+)CD8(+) and Tim-3(+)CD4(+) exhausted T cells, but not PD-1(+) T cells, was significantly increased in the adolescents with longer duration of infection compared to the children with shorter duration of HIV-1 infection. PD-1(+)CD8(+) T cells were directly associated with T cell immune activation in children. The frequency of Tim-3(+)CD8(+) T cells positively correlated with HIV-1 plasma viral load in the adolescents but not in the children. These data suggest that Tim-3 upregulation was driven by both HIV-1 viral replication and increased age, whereas PD-1 expression is associated with immune activation. These findings also suggest that the Tim-3 immune exhaustion phenotype rather than PD-1 or senescent cells plays an important role in age-related T cell dysfunction in perinatal HIV-1 infection. Targeting Tim-3 may serve as a novel therapeutic approach to improve immune control of virus replication and mitigate age related T cell exhaustion.

Decay kinetics of HIV-1 specific T cell responses in vertically HIV-1 exposed seronegative infants

OBJECTIVE

The majority of infants born, in developed countries, to HIV-1 positive women are exposed to the HIV-1 virus in utero or peri/post-partum, but are born uninfected. We, and others, have previously shown HIV-1 specific T cell responses in HIV-1 exposed seronegative (HESN) neonates/infants. Our objective in this study was to examine the rate of decay in their HIV-1 specific T cell response over time from birth.

DESIGN

Cross-sectional and longitudinal studies of HIV-1 specific T cell responses in HESN infants were performed.

METHODS

Peripheral blood mononuclear cells (PBMC) were isolated from 18 HIV-1 DNA PCR negative infants born to HIV-1 infected mothers receiving care at the Jacobi Medical Center, Bronx, NY, USA. PBMC were examined for T cell responses to HIV-1 antigens by interferon-gamma (IFN-γ) ELISPOT.

RESULTS

PBMC from 15 HESN neonates/infants were analyzed. We observed a decay of HIV-1 specific T cell responses from birth at a rate of -0.599 spot forming unit/10⁶ cells per day, with a median half-life decay rate of 21.38 weeks (13.39-115.8).

CONCLUSION

Our results support the dynamic nature of T cell immunity in the context of a developing immune system. The disparate rate of decay with studies of adults placed on antiretroviral drugs suggests that antigen specific T cell responses are driven by the natural rate of decay of the T cell sub-populations themselves.

Association of differentiation state of CD4+ T cells and disease progression in HIV-1 perinatally infected children

BACKGROUND

In the USA, most HIV-1 infected children are on antiretroviral drug regimens, with many individuals surviving through adolescence and into adulthood. The course of HIV-1 infection in these children is variable, and understudied.

METHODOLOGY/PRINCIPAL FINDINGS

We determined whether qualitative differences in immune cell subsets could explain a slower disease course in long term survivors with no evidence of immune suppression (LTS-NS; CD4%≥25%) compared to those with severe immune suppression (LTS-SS; CD4%≤15%). Subjects in the LTS-NS group had significantly higher frequencies of naïve (CCR7+CD45RA+) and central memory (CCR7+CD45RA-) CD4+ T cells compared to LTS-SS subjects (p = 0.0005 and <0.0001, respectively). Subjects in the rapid progressing group had significantly higher levels of CD4+ T(EMRA) (CCR7-CD45RA+) cells compared to slow progressing subjects (p<0.0001).

CONCLUSIONS/SIGNIFICANCE

Rapid disease progression in vertical infection is associated with significantly higher levels of CD4+ T(EMRA) (CCR7-CD45RA+) cells.

Identification of human endogenous retrovirus-specific T cell responses in vertically HIV-1-infected subjects

Human endogenous retrovirus (HERV)-specific T cell responses in HIV-1-infected adults have been reported. Whether HERV-specific immunity exists in vertically HIV-1-infected children is unknown. We performed a cross-sectional analysis of HERV-specific T cell responses in 42 vertically HIV-1-infected children. HERV (-H, -K, and -L family)-specific T cell responses were identified in 26 of 42 subjects, with the greatest magnitude observed for the responses to HERV-L. These HERV-specific T cell responses were inversely correlated with the HIV-1 plasma viral load and positively correlated with CD4(+) T cell counts. These data indicate that HERV-specific T cells may participate in controlling HIV-1 replication and that certain highly conserved HERV-derived proteins may serve as promising therapeutic vaccine targets in HIV-1-infected children.

Profile of darunavir in the treatment of HIV-infected pediatric and adolescent patients

The introduction of protease inhibitors (PI) containing antiretroviral regimens in the treatment of HIV infection in infants, children, and adolescents has dramatically decreased morbidity and mortality. Darunavir, the latest PI to be FDA approved for pediatric patients older than 6 years and currently the preferred PI for use in adult patients, was added as an alternative PI for use in children based on a combination of data from both adult and pediatric trials. This review of darunavir in the treatment of HIV-infected children and adolescents looks at the major published clinical trials findings, pharmacokinetic and resistance studies, and preliminary data on use in younger children.

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.

Human endogenous retrovirus K106 (HERV-K106) was infectious after the emergence of anatomically modern humans

HERV-K113 and HERV-K115 have been considered to be among the youngest HERVs because they are the only known full-length proviruses that are insertionally polymorphic and maintain the open reading frames of their coding genes. However, recent data suggest that HERV-K113 is at least 800,000 years old, and HERV-K115 even older. A systematic study of HERV-K HML2 members to identify HERVs that may have infected the human genome in the more recent evolutionary past is lacking. Therefore, we sought to determine how recently HERVs were exogenous and infectious by examining sequence variation in the long terminal repeat (LTR) regions of all full-length HERV-K loci. We used the traditional method of inter-LTR comparison to analyze all full length HERV-Ks and determined that two insertions, HERV-K106 and HERV-K116 have no differences between their 5′ and 3′ LTR sequences, suggesting that these insertions were endogenized in the recent evolutionary past. Among these insertions with no sequence differences between their LTR regions, HERV-K106 had the most intact viral sequence structure. Coalescent analysis of HERV-K106 3′ LTR sequences representing 51 ethnically diverse individuals suggests that HERV-K106 integrated into the human germ line approximately 150,000 years ago, after the emergence of anatomically modern humans.

Pregnancy in women with perinatally acquired HIV-infection: outcomes and challenges

This is a retrospective comparison of pregnant women with perinatally acquired HIV-infection (PAH) with a cohort of pregnant women with behaviorally acquired HIV-infection (BAH). PAH cases (11 women) included all pregnant adolescents followed at our HIV clinic from January 2000 to January 2009. BAH cases (27 women) were randomly selected from all deliveries within the study period at the same institution. Demographics, mode of delivery, CD4+ counts, and viral loads (VLs) before, during, and six months postpartum, as well as neonatal outcomes, were reviewed.

CD4 counts were significantly lower in the PAH group. VLs were statistically higher in the PAH group. VLs were undetectable at delivery in 60% of the PAH group compared with 88% of the BAH group. No cases of vertical transmission occurred.

PAH women may be at a higher risk for HIV-related disease progression. This may increase vertical transmission risks. Further studies and interventions with this growing population are warranted.

Cross-sectional dating of novel haplotypes of HERV-K 113 and HERV-K 115 indicate these proviruses originated in Africa before Homo sapiens

The human genome, human endogenous retroviruses (HERV), of which HERV-K113 and HERV-K115 are the only known full-length proviruses that are insertionally polymorphic. Although a handful of previously published papers have documented their prevalence in the global population; to date, there has been no report on their prevalence in the United States population. Here, we studied the geographic distribution of K113 and K115 among 156 HIV-1+ subjects from the United States, including African Americans, Hispanics, and Caucasians. In the individuals studied, we found higher insertion frequencies of K113 (21%) and K115 (35%) in African Americans compared with Caucasians (K113 9% and K115 6%) within the United States. We also report the presence of three single nucleotide polymorphism sites in the K113 5′ long terminal repeats (LTRs) and four in the K115 5′ LTR that together constituted four haplotypes for K113 and five haplotypes for K115. HERV insertion times can be estimated from the sequence differences between the 5′ and 3′ LTR of each insertion, but this dating method cannot be used with HERV-K115. We developed a method to estimate insertion times by applying coalescent inference to 5′ LTR sequences within our study population and validated this approach using an independent estimate derived from the genetic distance between K113 5′ and 3′ LTR sequences. Using our method, we estimated the insertion dates of K113 and K115 to be a minimum of 800,000 and 1.1 million years ago, respectively. Both these insertion dates predate the emergence of anatomically modern Homo sapiens.

Natural killer cells in perinatally HIV-1-infected children exhibit less degranulation compared to HIV-1-exposed uninfected children and their expression of KIR2DL3, NKG2C, and NKp46 correlates with disease severity

NK cells play an integral role in the innate immune response by targeting virally infected and transformed cells with direct killing and providing help to adaptive responses through cytokine secretion. Whereas recent studies have focused on NK cells in HIV-1-infected adults, the role of NK cells in perinatally HIV-1-infected children is less studied. Using multiparametric flow cytometric analysis, we assessed the number, phenotype, and function of NK cell subsets in the peripheral blood of perinatally HIV-1-infected children on highly active antiretroviral therapy and compared them to perinatally exposed but uninfected children. We observed an increased frequency of NK cells expressing inhibitory killer Ig-like receptors in infected children. This difference existed despite comparable levels of total NK cells and NK cell subpopulations between the two groups. Additionally, NK cell subsets from infected children expressed, with and without stimulation, significantly lower levels of the degranulation marker CD107, which correlates with NK cell cytotoxicity. Lastly, increased expression of KIR2DL3, NKG2C, and NKp46 on NK cells correlated with decreased CD4+ T-lymphocyte percentage, an indicator of disease severity in HIV-1- infected children. Taken together, these results show that HIV-1-infected children retain a large population of cytotoxically dysfunctional NK cells relative to perinatally exposed uninfected children. This reduced function appears concurrently with distinct NK cell surface receptor expression and is associated with a loss of CD4+ T cells. This finding suggests that NK cells may have an important role in HIV-1 disease pathogenesis in HIV-1-infected children.

Rational peptide selection to detect human immunodeficiency virus type 1-specific T-cell responses under resource-limited conditions

Understanding human immunodeficiency virus type 1 (HIV-1)-specific cytotoxic T-lymphocyte responses is important for the development of vaccines and therapies. We describe a novel method for the rational selection of peptides that target stable regions of the HIV-1 genome, rich in epitopes specifically recognized by the study population. This method will be of particular use under resource/sample-limited conditions.

Strong HIV-1-specific T cell responses in HIV-1-exposed uninfected infants and neonates revealed after regulatory T cell removal

BACKGROUND

In utero transmission of HIV-1 occurs on average in only 3%-15% of HIV-1-exposed neonates born to mothers not on antiretroviral drug therapy. Thus, despite potential exposure, the majority of infants remain uninfected. Weak HIV-1-specific T-cell responses have been detected in children exposed to HIV-1, and potentially contribute to protection against infection. We, and others, have recently shown that the removal of CD4(+) CD25(+) T-regulatory (Treg) cells can reveal strong HIV-1 specific T-cell responses in some HIV-1 infected adults. Here, we hypothesized that Treg cells could suppress HIV-1-specific immune responses in young children.

METHODOLOGY/PRINCIPAL FINDINGS

We studied two cohorts of children. The first group included HIV-1-exposed-uninfected (EU) as well as unexposed (UNEX) neonates. The second group comprised HIV-1-infected and HIV-1-EU children. We quantified the frequency of Treg cells, T-cell activation, and cell-mediated immune responses. We detected high levels of CD4(+) CD25(+) CD127(-) Treg cells and low levels of CD4(+) and CD8(+) T cell activation in the cord blood of the EU neonates. We observed HIV-1-specific T cell immune responses in all of the children exposed to the virus. These T-cell responses were not seen in the cord blood of control HIV-1 unexposed neonates. Moreover, the depletion of CD4(+) CD25(+) Treg cells from the cord blood of EU newborns strikingly augmented both CD4(+) and CD8(+) HIV-1-specific immune responses.

CONCLUSIONS/SIGNIFICANCE

This study provides new evidence that EU infants can mount strong HIV-1-specific T cell responses, and that in utero CD4(+) CD25(+) T-regulatory cells may be contributing to the lack of vertical transmission by reducing T cell activation.

Partial treatment interruption of protease inhibitor-based highly active antiretroviral therapy regimens in HIV-infected children

Treatment guidelines for HIV-infected children recommend using combinations of reverse transcriptase inhibitors (RTIs) and protease inhibitors (PIs). Successful suppression of HIV replication and adherence to these regimens are often suboptimal because of multiple factors. For patients with detectable viremia and limited treatment options, therapy simplification consisting of RTIs, referred to as partial treatment interruption (PTI), may represent a temporizing option. We describe a cohort of 26 HIV-infected children who underwent treatment simplification by discontinuing the PI and continuing therapy with 2 or more RTIs. The subjects, who were identified retrospectively, were followed for a period of 24 to 96 weeks. Data collected included clinical information, viral load, and CD4T lymphocyte percentage (CD4%) at baseline and 24, 48, and 96 weeks after PTI. Twenty-six, 21, and 11 patients were evaluated at 24, 48, and 96 weeks, respectively. No child had Centers for Disease Control and Prevention-defined disease progression, and there were no significant changes in viral loads (P > 0.5) across all study intervals after interruption of the PIs. Although most children maintained a CD4% > 15%, comparisons of CD4% at 24 and 48 weeks demonstrated a statistically significant decrease compared with baseline. Therapy simplification by PTI may provide a practical option in patients intolerant of or failing PI-based highly active antiretroviral therapy.

CD8 T cell effector maturation in HIV-1-infected children

HIV-1 infection generates maturational responses in overall CD4 and CD8 T cell populations in adults, with elevated expression of lytic effector molecules perforin and granzyme B, and reduced expression of CCR7 and CD45RA. Here, we have found that these marked effects were significantly less pronounced in children, both in terms of the skewed CCR7/CD45RA expression profile as well as the increased perforin expression. Similar to adults, HIV-specific CD8 cells in children were largely CD27+ CD45RA- and lacked perforin. However, one pediatric subject with late-stage infection displayed robust expansion of Gag 77-85-specific CD8 T cells which were perforin+ and lytic, but lacked expression of CD27 and IFNgamma. Our data indicate that the T cell effector maturation induced by HIV-1 infection is markedly weaker in children as compared to adults. The data also suggest, however, that the perforin-deficient state of HIV-specific CD8 T cells in children may be reversible.

Partial treatment interruption of protease inhibitors augments HIV-specific immune responses in vertically infected pediatric patients

BACKGROUND

Although highly active antiretroviral therapy has significantly reduced morbidity and mortality in HIV-infected children, it often fails to completely suppress viral replication, thereby allowing the emergence of drug-resistant variants. Protease inhibitor (PI) based therapy has been hypothesized to depress cell-mediated immune responses by reducing antigen presentation.

OBJECTIVES

To determine the effects of partial treatment interruption (PTI) of PI on HIV-specific cellular immune responses in children.

METHODS

We conducted a retrospective longitudinal study of HIV-specific cellular immune responses in 13 children who were vertically infected with HIV. All had detectable plasma viremia and had undergone PTI for a median of 1.0 year (range, 0.41-3.35 years) while continuing nucleoside reverse transcriptase inhibitor and non-nucleoside reverse transcriptase inhibitor therapy.

RESULTS

No significant changes in viral load were observed in the immediate time-point before and during PTI (P = 0.84) as well as in the overall period before and during PTI (P = 0.17). CD4 T-cell levels declined slowly immediately before and during PTI (P = 0.07) as well as during the overall PTI period (P = 0.0002), but the rate of CD4 T-cell decline was not significantly increased during PTI. Immediate to PTI, HIV-specific CD4 and CD8 T-cell responses increased by 70% (P < 0.0001) and 92% (P < 0.0001), respectively, and CD4 and CD8 T-cell activation levels (P = 0.6834 and P = 0.6081, respectively) remained unchanged.

CONCLUSION

HIV-specific cellular immune responses are boosted in children who have interrupted PI-based therapy.

Higher frequency of HIV-1-specific T cell immune responses in African American children vertically infected with HIV-1

The progression of human immunodeficiency virus (HIV) disease and plasma levels of HIV may differ between racial groups. We compared HIV-specific T cell responses between vertically HIV-1-infected Hispanic and African American children. Subjects were matched for sex, age, viral load, and CD4(+) cell count in 18 pairs; T cell responses were measured by cytokine-enhanced interferon- gamma assay. Peripheral blood mononuclear cells were stimulated with HIV consensus peptides from Gag, Nef, and Tat. The influence of ethnicity, sex, age, viral load, and CD4(+) cell count on T cell responses was determined through linear regression analyses. After adjustment for CD4(+) count, age, and log(10) viral load, African American children demonstrated significantly higher Gag responses (average, 486 spot-forming cells higher; P=.01) than Hispanic children; this was significantly driven by robust responses in African American girls near the age of puberty, many of whom carried the human leukocyte antigen class I B*58 allele.

Expansion of CD7(low) and CD7(negative) CD8 T-cell effector subsets in HIV-1 infection: correlation with antigenic load and reversion by antiretroviral treatment

The antiviral response of CD8 T cells involves the differentiation of naive T cells into distinct types of effector and memory cells, which may be distinguished by the level of CD7 expression. We have investigated CD8 T cells in adults and children infected with HIV-1 to determine the disease relevance of cell subsets defined by CD7. CD8 T cells from patients infected with HIV-1 displayed profound down-modulation of CD7 expression as compared with healthy subjects, with expansion of both CD7(low) and CD7(negative) effector subsets. Loss of CD7(high) cells correlated directly with HIV-1 load and was particularly pronounced in patients with rapid disease progression. CD8 T cells specific for HIV-1, as well as Epstein-Barr virus (EBV) and cytomegalovirus (CMV) were predominantly found in the CD7(low) effector cell subset. Furthermore, recovery of CD4 counts on antiretroviral therapy was associated with reversion of the skewed CD7 profile in CD8 T cells. Thus, effector CD8 T-cell subsets distinguished by lowered CD7 expression expand in a manner that correlates with the magnitude of HIV-1, EBV, and CMV antigenic challenge and contract in response to successful antiretroviral treatment. The results are discussed in relation to the dual roles of CD7 as a receptor of both costimulation and cell death.

Limited Magnitude and Breadth in the HLA-A2-Restricted CD8 T-Cell Response to Nef in Children with Vertically Acquired HIV-1 Infection

CD8 T cells are believed to play a key role in the immune control of human immunodeficiency virus-1 (HIV-1) infection in children as well as in adults. We have used an enhanced EliSpot (AmpliSpot) assay to quantitate CD8 T-cell responses directed to five human leucocyte antigen (HLA)-A2-presented HIV-1 epitopes derived from the key viral antigen Nef. Responses were assayed in one group of 21 children with vertically acquired HIV infection and one group of 19 adult subjects with chronic infection. The paediatric group displayed significantly weaker and more narrowly focused CD8 T-cell responses as compared with the adult subjects. Two epitopes stood out as the most frequently and strongly recognized, suggesting that they should be considered immunodominant in the CD8 T-cell response to HIV-1 Nef. Interestingly, the most frequently and strongly recognized epitope in both adults and children was previously identified in HLA-A2-transgenic mice, demonstrating the usefulness of such mice in finding natural viral epitopes. These findings indicate significant weakness in strength and breadth of the CD8 T-cell response to the target protein Nef in infected children and prompt renewed efforts into the immunology of vertically acquired HIV-1 infection.

HIV-specific CD8+ T cell function in children with vertically acquired HIV-1 infection is critically influenced by age and the state of the CD4+ T cell compartment

The immunology of vertical HIV transmission differs from that of adult infection in that the immune system of the infant is not fully matured, and the factors that influence the functionality of CD8(+) T cell responses against HIV in children remain largely undefined. We have investigated CD8(+) T cell responses in 65 pediatric subjects with vertically acquired HIV-1 infection. Vigorous, broad, and Ag dose-driven CD8(+) T cell responses against HIV Ags were frequently observed in children who were older than 3 years of age and maintained CD4(+) T cell counts >400 cells/ micro l. In contrast, younger age or a CD4(+) T cell count <400 cells/ micro l was associated with poor CD8(+) T cell responses and high HIV loads. Furthermore, subjects with a severely depleted and phenotypically altered CD4(+) T cell compartment had circulating Gag-specific CD8(+) T cells with impaired IFN-gamma production. When viral load was not suppressed by antiviral treatment, subjects that fell below the putative age and CD4(+) T cell count thresholds had significantly reduced CD8(+) T cell responses and significantly higher viral loads. Thus, the data suggest that fully effective HIV-specific CD8(+) T cell responses take years to develop despite an abundance of Ag in early life, and responses are further severely impaired, independent of age, in children who have a depleted or skewed CD4(+) T cell compartment. The results are discussed in relation to differences between the neonatal and adult immune systems in the ability to respond to HIV infection.

Generation of CD3+CD8low thymocytes in the HIV type 1-infected thymus

Infection with the HIV type 1 (HIV-1) can result both in depletion of CD4(+) T cells and in the generation of dysfunctional CD8(+) T cells. In HIV-1-infected children, repopulation of the peripheral T cell pool is mediated by the thymus, which is itself susceptible to HIV-1 infection. Previous work has shown that MHC class I (MHC I) molecules are strongly up-regulated as result of IFN-alpha secretion in the HIV-1-infected thymus. We demonstrate in this study that increased MHC I up-regulation on thymic epithelial cells and double-positive CD3(-/int)CD4(+)CD8(+) thymocytes correlates with the generation of mature single-positive CD4(-)CD8(+) thymocytes that have low expression of CD8. Treatment of HIV-1-infected thymus with highly active antiretroviral therapy normalizes MHC I expression and surface CD8 expression on such CD4(-)CD8(+) thymocytes. In pediatric patients with possible HIV-1 infection of the thymus, a low CD3 percentage in the peripheral circulation is also associated with a CD8(low) phenotype on circulating CD3(+)CD8(+) T cells. Furthermore, CD8(low) peripheral T cells from these HIV-1(+) pediatric patients are less responsive to stimulation by Ags from CMV. These data indicate that IFN-alpha-mediated MHC I up-regulation on thymic epithelial cells may lead to high avidity interactions with developing double-positive thymocytes and drive the selection of dysfunctional CD3(+)CD8(low) T cells. We suggest that this HIV-1-initiated selection process may contribute to the generation of dysfunctional CD8(+) T cells in HIV-1-infected patients.

Selective loss of innate CD4(+) V alpha 24 natural killer T cells in human immunodeficiency virus infection

V alpha 24 natural killer T (NKT) cells are innate immune cells involved in regulation of immune tolerance, autoimmunity, and tumor immunity. However, the effect of human immunodeficiency virus type 1 (HIV-1) infection on these cells is unknown. Here, we report that the V alpha 24 NKT cells can be subdivided into CD4(+) or CD4(-) subsets that differ in their expression of the homing receptors CD62L and CD11a. Furthermore, both CD4(+) and CD4(-) NKT cells frequently express both CXCR4 and CCR5 HIV coreceptors. We find that the numbers of NKT cells are reduced in HIV-infected subjects with uncontrolled viremia and marked CD4(+) T-cell depletion. The number of CD4(+) NKT cells is inversely correlated with HIV load, indicating depletion of this subset. In contrast, CD4(-) NKT-cell numbers are unaffected in subjects with high viral loads. HIV infection experiments in vitro show preferential depletion of CD4(+) NKT cells relative to regular CD4(+) T cells, in particular with virus that uses the CCR5 coreceptor. Thus, HIV infection causes a selective loss of CD4(+) lymph node homing (CD62L(+)) NKT cells, with consequent skewing of the NKT-cell compartment to a predominantly CD4(-) CD62L(-) phenotype. These data indicate that the key immunoregulatory NKT-cell compartment is compromised in HIV-1-infected patients.

Expression of IgA and IgM Fc receptors on murine T lymphocytes

Fc receptors are induced on T cells following activation via the TCR. T cells that express Fc receptors transiently have the ability to use two different cognate systems: the TCR and immunoglobulins bound to the Fc receptors. The studies discussed in this article are focused on the Fc alpha and Fc mu receptors that can be induced on certain subsets of murine T lymphocytes. The article emphasizes the role of the T cell receptor for antigen in the expression of Fc alpha and Fc mu receptors on murine T cells and reviews experimental observations that suggest significant molecular heterogeneity of these Fc receptors. The finding that regulation of expression of Fc alpha receptors and Fc mu receptors on T lymphocytes is linked to cellular activation via the CD3/TCR complex implies that these Fc receptors might mediate important functions in the biology and pathology of T cells.