T cells target APOBEC3 proteins in human immunodeficiency virus type 1-infected humans and simian immunodeficiency virus-infected Indian rhesus macaques.

APOBEC3 proteins mediate potent antiretroviral activity by hypermutating the retroviral genome during reverse transcription. To counteract APOBEC3 and gain a replicative advantage, lentiviruses such as human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV) have evolved the Vif protein, which targets APOBEC3 proteins for proteasomal degradation. However, the proteasome plays a critical role in the generation of T cell peptide epitopes. Whether Vif-mediated destruction of APOBEC3 proteins leads to the generation and presentation of APOBEC3-derived T cell epitopes on the surfaces of lentivirus-infected cells remains unknown. Here, using peptides derived from multiple Vif-sensitive APOBEC3 proteins, we identified APOBEC3-specific T cell responses in both HIV-1-infected patients and SIV-infected rhesus macaques. These results raise the possibility that these T cell responses may be part of the larger antiretroviral immune response.

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.

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.

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.

Etravirine in treatment-experienced HIV-1-infected children 1 year to less than 6 years of age.

OBJECTIVE: To describe the pharmacokinetics, safety, and efficacy of etravirine (ETR) in HIV-infected children 1 to less than 6 years of age. DESIGN: Phase I/II, open-label, multicenter, dose-finding study. METHODS: Antiretroviral therapy (ART)-experienced children in two age cohorts (I: 2 to <6 years; II: 1 to less than 2 years) received weight-based ETR, swallowed whole or dispersed in liquid, with optimized ART including a ritonavir-boosted protease inhibitor. Intensive pharmacokinetics occurred 7-18 days after starting ETR. Participants with ETR AUC12h less than 2350 ng h/ml had a dose increase and repeat pharmacokinetics. RESULTS: Twenty-six children enrolled and 21 (15 in cohort I and 6 in cohort II) had evaluable intensive pharmacokinetics sampling at the final weight-based dose. On the final dose, the geometric mean ETR AUC12h was 3823 ng h/ml for cohort I and 3328 ng h/ml for cohort II. Seven children (33.3%) on the final dose, all taking ETR dispersed, had an AUC12  h less than 2350 ng h/ml and underwent a dose increase. ETR AUC12  h was 3.8-fold higher when ETR was swallowed whole vs. dispersed, P less than 0.0001. On the final dose, 75 and 33.3% in cohorts I and II, respectively, had HIV-1 RNA 400 copies/ml or less or at least 2 log reductions from baseline at week 48. Three children (11.5%) experienced a grade at least 3 adverse event related to ETR but only 1 discontinued. CONCLUSION: ETR was well tolerated. Predefined pharmacokinetics targets were met but overall exposures were low vs. historical data in adults, particularly in young children taking dispersed tablets. A high rate of viral efficacy was observed among those aged 2 to more than 6 years but not in those less than 2 years.

Safety and efficacy at 240 weeks of different raltegravir formulations in children with HIV-1: a phase 1/2 open label, non-randomised, multicentre trial.

BACKGROUND: Raltegravir is an integrase inhibitor approved for use in adults and children with HIV-1 infection, but there are no data on the long-term use of this medication in children. We aimed to assess the long-term safety, tolerability, pharmacokinetics, and efficacy of multiple raltegravir formulations in children aged 4 weeks to 18 years with HIV-1 infection. METHODS: In this phase 1/2 open-label multicentre trial (IMPAACT P1066), done in 43 IMPAACT network sites in the USA, South Africa, Brazil, Botswana, and Argentina, eligible participants were children aged 4 weeks to 18 years with HIV-1 infection who had previously received antiretroviral therapy (ART), had HIV-1 RNA higher than 1000 copies per mL, and no exposure to integrase inhibitors. Participants were separated into five age groups and enrolled in six cohorts. Three formulations of open-label raltegravir-adult tablets, chewable tablets, and granules for oral suspension-were added to individualised optimised background therapy, according to the age and weight of participants. The primary outcome at 48 weeks has been previously reported. In the 240-week follow-up, outcomes of interest included graded clinical and laboratory safety of raltegravir formulations during the study and virological efficacy (with virological success defined as HIV-1 RNA reduction of >1 log10 from baseline or HIV-1 RNA <400 copies per mL) at week 240. The primary analysis group for safety and efficacy comprised patients treated only with the final selected dose of raltegravir. This trial is registered with ClinicalTrials.gov, number NCT00485264. FINDINGS: Between August, 2007, and December, 2012, 220 patients were assessed for eligibility, and 153 were enrolled and treated. Of these patients, 122 received only the final selected dose of raltegravir (63 received adult tablets, 33 chewable tablets, and 26 oral granules), and one was not treated. There were few serious clinical or laboratory safety events noted, with two patients having a drug-related adverse event (skin rash), which led one patient to discontinue the study treatment. The addition of raltegravir to an individually optimised ART regimen resulted in virological success at week 240 in 19 (44·2%, 95% CI 29·1-60·1) of 43 patients receiving 400 mg tablets, 24 (77·4%, 58·9-90·4) of 31 patients receiving the chewable tablets, and 13 (86·7%, 59·5-98·3) of 15 patients receiving oral granules. Among patients with virological failure, raltegravir resistance was noted in 19 (38%) of 50 patients who had virological rebound after initial suppression and had samples at virological failure available for testing. INTERPRETATION: Our study suggests that raltegravir can be used for the treatment of HIV-1 infection in children as young as 4 weeks, with the expectation of long-term safety and efficacy, but should be used with caution among older children who had previous extensive antiretroviral therapy. FUNDING: National Institute of Allergy and Infectious Diseases, National Institute of Child Health and Human Development, National Institute of Mental Health, and Merck.

Baseline resistance to nucleoside reverse transcriptase inhibitors fails to predict virologic response to combination therapy in children (PACTG 338).

BACKGROUND: The association between baseline drug resistance mutations and subsequent increase in viral failure has not been established for HIV-infected children. We evaluated drug resistance mutations at 39 codon sites (21 protease inhibitor (PI) resistant codons and 18 nucleoside reverse transcriptase inhibitor (NRTI) resistant codons) for 92 clinically stable NRTI-experienced, PI-naive HIV-infected children 2 to 17 years of age who were initiating new therapy with ritonavir plus zidovudine (ZDV) and lamivudine or plus stavudine. The association between baseline drug resistance mutations and subsequent viral failure after 12 and 24 weeks of highly active antiretroviral therapy (HAART) was studied. RESULTS: There were few primary PI associated mutations in this PI-naïve population, but 84% had NRTI mutations--codons 215 (66%), 41 (42%), 67 (37%), 210 (33%) and 70 (32%). None of the specific baseline drug resistance mutations were associated with a higher rate of virologic failure after 12 or 24 weeks of HAART. Median week 12 viral load decreased as the total number of NRTI mutations at baseline increased (P = 0.006). Specifically, a higher level of baseline ZDV resistance mutation was associated with a decrease in viral failure after 12 weeks on a ZDV-containing HAART regimen (P = 0.017). CONCLUSION: No increase was seen in the rate of viral failure after HAART associated with the presence of resistance mutations at baseline. This paradoxical result may be due to adherence, replicative capacity, or ZDV hypersusceptibility to the new regimen.

Decline in CD4 T lymphocytes with monotherapy bridging strategy for non-adherent adolescents living with HIV infection: Results of the IMPAACT P1094 randomized trial.

INTRODUCTION: Management of persistently non-adherent youth living with HIV (YLHIV) with virologic failure (VF) on combination antiretroviral therapy (cART) remains challenging. One strategy has been using 3TC/ FTC monotherapy (3TC/FTC), which in the presence of the M184V resistance mutation, does not suppress viral replication nor select for additional drug resistance mutations, and reduces viral fitness with limited side effects. P1094 compared the immunologic outcome of continuing failing cART vs. switching to 3TC/FTC as a "bridging strategy" to subsequent suppressive cART for non-adherent YLHIV with pre-existing M184V resistance. MATERIALS & METHODS: Participants with documented nonadherence, M184V mutation, CD4+ T cell count ≥100 cells/mm3 and VF (HIV-1 plasma RNA ≥400 copies/mL (2.6 log10 HIV-1 RNA) were enrolled and randomized to continue failing cART vs. switch to 3TC/FTC. The primary endpoint (time to ≥30% CD4+ T cell decline or development of CDC class C events) at 28-weeks were assessed by Kaplan-Meier (K-M) curves in an intent-to-treat analysis. RESULTS: Thirty-three perinatally acquired YLHIV participants (16 continuing cART and 17 3TC/FTC) enrolled in the study. The median age, entry CD4+ T cell count, and viral load were 15 years (Inter-quartile range (IQR) 14-20), 472 cells/mm3 (IQR 384-651), and 4.0 log10HIV-1 RNA copies/ml (IQR 3.2-4.5), respectively. Five participants, all in the 3TC/FTC arm, reached the primary endpoint for absolute CD4+ T cell decline (p = 0.02, exact log-rank test comparing monotherapy to cART). The Kaplan-Meier estimate of probability of primary endpoint on 3TC/FTC at 28 weeks was 0.41 (standard error 0.14). There were no CDC class C events or deaths and no statistically significant difference in frequencies of adverse events between the arms. CONCLUSIONS: Non-adherent participants randomized to 3TC/FTC were more likely than those maintained on failing cART to experience a confirmed decline in CD4+ count of ≥30%. Although this study suffers from limitations of small sample size and premature discontinuation, the randomized comparison to continuing failing cART indicates that 3TC/FTC provides inferior protection from immunologic deterioration for non-adherent youth with M184V resistance. Better alternatives to 3TC/FTC such as ART with higher barriers to resistance and novel adherence and treatment strategies for nonadherent youth are urgently needed. TRIAL REGISTRATION: Clinical Trials.gov NCT01338025.

Cytomegalovirus-specific cell-mediated immunity in HIV-infected children on HAART.

The objectives of this study were to define the magnitude, time course, and virologic and immunologic correlates of HAART-associated reconstitution of cytomegalovirus (CMV)-specific cell-mediated immunity (CMI) in pediatric HAART recipients. Thirty-five HIV-infected CMV-seropositive subjects < or = 22 years on or about to receive HAART had CMV-CMI measured by responder cell frequency (RCF) and interferon-gamma (IFN-gamma) secretion over 3 years. RCF was detected in 33, 52, 38, and 28% before HAART and at years 1, 2, and > or = 3, respectively. Corresponding percentages for IFN-gamma were 100, 85, 100, and 38%. Neither RCF nor IFN-gamma was significantly associated with CD4% before or after HAART initiation. Lower HIV replication was associated with a higher proportion of subjects with positive RCF, but not IFN-gamma. There were no clinical CMV manifestations during the study. HIV-infected children did not demonstrate a significant increase in CMV-CMI with longer HAART duration, which suggests that CMV immunereconstitution involves more complex immunologic and virologic interactions than previously anticipated.

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.

Growth of human immunodeficiency virus-infected children receiving highly active antiretroviral therapy.

BACKGROUND: Weight and height growth of HIV-infected children tends to lag behind that of uninfected children of similar age. Previous reports of the effect of highly active antiretroviral therapy (HAART) on the growth of HIV-infected children have been contradictory. METHODS: Age- and gender-adjusted height and weight z scores were studied for 192 HIV-infected children, 4 months to 17 years of age, who had been treated with antiretroviral therapy for at least 16 weeks. These children, in clinically and immunologically stable condition, were enrolled into one of 4 HAART regimens and evaluated for 96 weeks. RESULTS: At baseline, these HIV-infected children were significantly shorter than uninfected children (mean z score, -0.57; 95% confidence interval, -0.73 to -0.41; P < 0.001). Children with greater viral loads at baseline were significantly shorter and lighter than children with smaller viral loads (both P < 0.001). Administration of HAART led to an increase in mean weight z scores to normal values (mean z score increase, from -0.16 to >0) by week 48 and an increase in mean height z scores of 72% toward normal values (mean z score increase, from -0.57 to -0.16) by week 96. Younger children gained height more rapidly (P < 0.001), and children with greater baseline viral loads gained weight more rapidly (P < 0.001). There was no evidence of differential height or weight changes in 48 weeks between children with different degrees of virologic control. CONCLUSIONS: HAART improved the average weight gain of HIV-infected children from subnormal to normal after 1 year and improved average height growth to nearly normal after 2 years.

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.

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.

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.

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.

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.

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.

Immunological response to highly active antiretroviral therapy in children with clinically stable HIV-1 infection.

We studied changes in 60 immunological parameters after the administration of highly active antiretroviral therapy (HAART) in 192 clinically stable antiretroviral drug-experienced HIV-1-infected children 4 months-17 years old. The studied immunological parameters included standard lymphocyte subsets and lymphocyte surface markers of maturation and activation. The most significant changes during the 48-week study period were seen for CD8(+), CD8(+)CD62L(+)CD45RA(+), CD8(+)CD38(+)HLA-DR(+), and CD4(+) T cell percentages (P < .0001 for all parameters). These changes suggest that significant decreases in the expression of activation markers and increases in the expression of naive markers in the CD8(+) T cell population may be related to better virologic control in these HIV-1-infected children, who had relatively stable immune function at the initiation of HAART. At week 44 of HAART, the major immunological parameters in these HIV-1-infected children moved from baseline values to about halfway to two-thirds of the way toward the values in healthy, uninfected children.

Tetanus immunity after diphtheria, tetanus toxoids, and acellular pertussis vaccination in children with clinically stable HIV infection.

BACKGROUND: HIV infection often impairs the immune response to childhood vaccines. OBJECTIVE: We sought to study the ability of HIV-infected children receiving highly active antiretroviral therapy (HAART) to generate a booster response to immunization with a recall antigen to which they had lost humoral immunity. METHODS: Diphtheria, tetanus toxoids, and acellular pertussis (DTaP) vaccination was given at either 16 or 36 weeks after initiation of HAART to 37 HIV-infected children 2 to 9 years of age with a history of DTaP or diphtheria-tetanus-pertussis receipt who had negative tetanus antibody titers (