Immunologic and virologic responses to HAART in severely immunocompromised HIV-1-infected children

Thirty-year Perspective of the Long-term Survival, CD4 Percentage and Social Achievements of Perinatally HIV-infected Children as a Function of Their Birth Era

BACKGROUND

Pediatric HIV has evolved from a pre-antiretroviral (ART) era (pre-1989 or pre-ART) to an ART era (1989 to 1996) and to a highly active antiretroviral therapy (HAART) era (post-1996). As we have passed the third decade following these individuals, we thought it useful to review clinical, laboratory and social outcomes.

METHODS

A retrospective, cross-sectional study of 399 children infected perinatally. They were divided into pre-ART, ART and HAART groups. A Kaplan-Meier plot was constructed. One hundred seventy-nine have been lost to follow-up at an average of 7.6 (0.3-27.6) years.

RESULTS

Approximately 40%, 80% and 90% of individuals in the pre-ART, ART and HAART groups have long-term survival. One hundred twenty-one died at an average of 5.1 (0-26.1) years. Pre-ART, ART and HAART groups had mean most recent CD4% values (±SEM) of 16.74 (1.09), 22.97 (0.96) and 33.07 (2.09), respectively (P < 0.001). Pre-ART RNA is limited in that era and present if they survived to another era. In this group, the median RNA values in those who died (311,300, n = 16) was greater than in survivors (19,402, n = 45). Forty-three percent of the individuals in the ART group and 77% of individuals in the HAART group had most recent HIV RNA <400 copies/mL. Eighteen individuals >18 years of age have only a grade school or no education. Fifty-five have graduated high school or received an equivalency diploma. Twenty-three more have completed college. Nadir and recent CD4% of those who did and did not complete high school was equivalent to college graduates. Sixteen survivors (1/2 male) have had 18 uninfected children.

CONCLUSIONS

This first long-term follow-up study demonstrates remarkable survival and social skills of our patients.

Incomplete immune reconstitution despite virologic suppression in HIV-1 infected children and adolescents

OBJECTIVES

Some perinatally infected children do not regain normal CD4(+) T-cell counts despite suppression of HIV-1 plasma viremia by antiretroviral therapy (ART). The frequency, severity and significance of these discordant treatment responses remain unclear.

DESIGN

We examined the persistence of CD4(+) lymphocytopenia despite virologic suppression in 933 children (≥ 5 years of age) in the USA, Latin America and the Caribbean.

METHODS

CD4(+) T-cell trajectories were examined and Kaplan-Meier methods used to estimate median time to CD4(+) T-cell count at least 500 cells/μl.

RESULTS

After 1 year of virologic suppression, most (99%) children achieved a CD4(+) T-cell count of at least 200 cells/μl, but CD4(+) T-cell counts remained below 500 cells/μl after 1 and 2 years of virologic suppression in 14 and 8% of children, respectively. Median times to first CD4(+) T-cell count at least 500 cells/μl were 1.29, 0.78 and 0.46 years for children with less than 200, 200-349 and 350-499 cells/μl at the start of virologic suppression. New AIDS-defining events occurred in nine children, including four in the first 6 months of virologic suppression. Other infectious and HIV-related diagnoses occurred more frequently and across a wide range of CD4(+) cell counts.

CONCLUSION

ART improved CD4(+) cell counts in most children, but the time to CD4(+) cell count of at least 500 cells was highly dependent upon baseline immunological status. Some children did not reach a CD4(+) T-cell count of 500 cells/μl despite 2 years of virologic suppression. AIDS-defining events occurred in 1% of the population, including children in whom virologic suppression and improved CD4(+) T-cell counts were achieved.

Safety and effectiveness of combination antiretroviral therapy during the first year of treatment in HIV-1 infected Rwandan children: a prospective study

Background

With increased availability of paediatric combination antiretroviral therapy (cART) in resource limited settings, cART outcomes and factors associated with outcomes should be assessed.

Methods

HIV-infected children <15 years of age, initiating cART in Kigali, Rwanda, were followed for 18 months. Prospective clinical and laboratory assessments included weight-for-age (WAZ) and height-for-age (HAZ) z-scores, complete blood cell count, liver transaminases, creatinine and lipid profiles, CD4 T-cell count/percent, and plasma HIV-1 RNA concentration. Clinical success was defined as WAZ and WAZ >−2, immunological success as CD4 cells ≥500/mm³ and ≥25% for respectively children over 5 years and under 5 years, and virological success as a plasma HIV-1 RNA concentration <40 copies/mL.

Results

Between March 2008 and December 2009, 123 HIV-infected children were included. The median (interquartile (IQR) age at cART initiation was 7.4 (3.2, 11.5) years; 40% were <5 years and 54% were female. Mean (95% confidence interval (95%CI)) HAZ and WAZ at baseline were −2.01 (−2.23, −1.80) and −1.73 (−1.95, −1.50) respectively and rose to −1.75 (−1.98, −1.51) and −1.17 (−1.38, −0.96) after 12 months of cART. The median (IQR) CD4 T-cell values for children <5 and ≥5 years of age were 20% (13, 28) and 337 (236, 484) cells/mm³respectively, and increased to 36% (28, 41) and 620 (375, 880) cells/mm³. After 12 months of cART, 24% of children had a detectable viral load, including 16% with virological failure (HIV-RNA>1000 c/mL). Older age at cART initiation, poor adherence, and exposure to antiretrovirals around birth were associated with virological failure. A third (33%) of children had side effects (by self-report or clinical assessment), but only 9% experienced a severe side effect requiring a cART regimen change.

Conclusions

cART in Rwandan HIV-infected children was successful but success might be improved further by initiating cART as early as possible, optimizing adherence and optimizing management of side effects.

Immunology of pediatric HIV infection

Most infants born to human immunodeficiency virus (HIV)-infected women escape HIV infection. Infants evade infection despite an immature immune system and, in the case of breastfeeding, prolonged repetitive exposure. If infants become infected, the course of their infection and response to treatment differs dramatically depending upon the timing (in utero, intrapartum, or during breastfeeding) and potentially the route of their infection. Perinatally acquired HIV infection occurs during a critical window of immune development. HIV's perturbation of this dynamic process may account for the striking age-dependent differences in HIV disease progression. HIV infection also profoundly disrupts the maternal immune system upon which infants rely for protection and immune instruction. Therefore, it is not surprising that infants who escape HIV infection still suffer adverse effects. In this review, we highlight the unique aspects of pediatric HIV transmission and pathogenesis with a focus on mechanisms by which HIV infection during immune ontogeny may allow discovery of key elements for protection and control from HIV.

Immune reconstitution and vaccination outcome in HIV-1 infected children: present knowledge and future directions

Current evidence on routine immunization of HIV-1 infected children point out the need for a special vaccine schedule in this population. However, optimal strategies for identifying individuals susceptible to infections, and then offering them sustained protection through appropriate immunization schedule, both in terms of timing and number of vaccine doses, still remain to be elucidated. Understanding the degree of immune recovery after HAART initiation is important in guiding administration of routine vaccination in HIV-1 infected children. Although quantitative measures (e.g., CD4+ T-cell counts and immunoglobulin levels) are frequently performed to evaluate immune parameters, these measures do not fully mirror functional immune recovery. Here, we will review the status of single mandatory and recommended vaccines for HIV-1 infected children in relation to immune recovery after HAART initiation with the aim of identifying new means to help design personalized vaccine schedules for this population.

The long-term effectiveness of generic adult fixed-dose combination antiretroviral therapy for HIV-infected Ugandan children

BACKGROUND

Access to pediatric antiretroviral formulations is increasing in resource-limited countries, however adult FDCs are still commonly used by antiretroviral therapy (ART) programs.

OBJECTIVE

To describe long-term effectiveness of using adult FDC of d4T+3TC+NVP (Triomune) in children for HIV treatment.

METHODS

Clinical, immunologic, and virologic outcomes of HIV-infected ART-naïve children aged six months to 12 years, were evaluated up to 96 weeks post-ART initiation.

RESULTS

From March 2004 to June 2006, 104 children were followed with a median age of 5.4 years, median CD4 cell percent and HIV-1 RNA were 11.0% (IQR 6.7-13.9) and 348,846copies/mL (IQR 160,941-681,313) respectively at baseline. Using Kaplan-Meir estimates, 75% of children had undetectable viral loads (<400copies/mL) at 96 weeks of ART. Children with a baseline CD4 cell percent >15% were 3 times more likely to achieve viral load <400copies/mL than those with baseline CD4 cell percent <5% after adjusting for baseline age {aHR = 3.03 (1.10-8.32), p=0.03}; no difference was found among those with CD4 cell percent >5-14.9% and <5%.

CONCLUSION

Treatment with generic adult FDC for HIV-infected Ugandan children led to sustained clinical, immunologic and virologic response during 96 weeks of ART. Early initiation of ART is key to achieving virological success.

Developmental regulation of P-glycoprotein activity within thymocytes results in increased anti-HIV protease inhibitor activity

The thymus harbors HIV-1 and supports its replication. Treatment with PI-containing ART restores thymic output of naïve T cells. This study demonstrates that CXCR4-using WT viruses are more sensitive to PI in fetal thymcocytes than mature T cells with average IC(50) values for two PIs, RTV and IDV, of 1.5 nM (RTV) and 4.4 nM (IDV) in thymocytes versus 309.4 nM (RTV) and 27.3 nM (IDV) in mature T cells. P-gp activity, as measured using Rh123 efflux and quantitation of P-gp mRNA, increased with thymocyte maturation into CD4 and CD8 lineage T cells. P-gp activity is developmentally regulated in the thymus. Thymocytes developed increased levels of P-gp activity as maturation from DP to SP CD4 or CD8 T cells occurred, although CD4 T cells acquired activity more rapidly. Reduced P-gp activity in thymocytes is one mechanism for effectiveness of PI therapy in suppressing viral replication in the thymus and in reconstitution of naïve T cells, particularly among children receiving PI-containing ART.

Post-HAART outcomes in pediatric populations: comparison of resource-limited and developed countries

CONTEXT

No formal comparison has been made between the pediatric post-highly active antiretroviral therapy (HAART) outcomes of resource-limited and developed countries.

OBJECTIVE

To systematically quantify and compare major baseline characteristics and clinical end points after HAART between resource-limited and developed settings.

METHODS

Published articles and abstracts (International AIDS Society 2009, Conference on Retroviruses and Opportunistic Infections 2010) were examined from inception (first available publication for each search engine) to March 2010. Publications that contained data on post-HAART mortality, weight-for-age z score (WAZ), CD4 count, or viral load (VL) changes in pediatric populations were reviewed. Selected studies met the following criteria: (1) patients were younger than 21 years; (2) HAART was given (≥ 3 antiretroviral medications); and (3) there were >20 patients. Data were extracted for baseline age, CD4 count, VL, WAZ, and mortality, CD4 and virologic suppression over time. Studies were categorized as having been performed in a resource-limited country (RLC) or developed country (DC) on the basis of the United Nations designation. Mean percentage of deaths per cohort and deaths per 100 child-years, baseline CD4 count, VL, WAZ, and age were calculated for RLCs and DCs and compared by using independent samples t tests.

RESULTS

Forty RLC and 28 DC publications were selected (N = 17 875 RLCs; N = 1835 DC). Mean percentage of deaths per cohort and mean deaths per 100 child-years after HAART were significantly higher in RLCs than DCs (7.6 vs 1.6, P < .001, and 8.0 vs 0.9, P < .001, respectively). Mean baseline CD4% was 12% in RLCs and 23% in DCs (P = .01). Mean baseline VLs were 5.5 vs 4.7 log(10) copies per mL in RLCs versus DCs (P < .001).

CONCLUSIONS

Baseline CD4% and VL differ markedly between DCs and RLCs, as does mortality after pediatric HAART. Earlier diagnosis and treatment of pediatric HIV in RLCs would be expected to result in better HAART outcomes.

Immunologic basis for revaccination of HIV-infected children receiving HAART

With increasing access to antiretroviral therapy for children infected with HIV, especially in sub-Saharan Africa, better understanding of the development and maintenance of memory T- and B-cell responses to pathogens after immune reconstitution is needed to assess the risk of infection. Knowledge of long-term immune responses after starting HAART is of particular importance for policies on revaccination of HIV-infected children, who may lose protective immunity to prior infections and immunizations. We review normal development of T- and B-cell memory responses to viruses and vaccines against viral pathogens, and contrast the immunological effects of perinatal HIV transmission with HIV infection acquired later in life. We then explore the potential benefits of antiretroviral therapy and revaccination, using measles virus as a model.

Growth, immune and viral responses in HIV infected African children receiving highly active antiretroviral therapy: a prospective cohort study

Background

Scale up of paediatric antiretroviral therapy in resource limited settings continues despite limited access to routine laboratory monitoring. We documented the weight and height responses in HIV infected Ugandan children on highly active antiretroviral therapy and determined clinical factors associated with successful treatment outcomes.

Methods

A prospective cohort of HIV infected children were initiated on HAART and followed for 48 weeks. Body mass index for age z scores(BAZ), weight and height-for-age z scores (WAZ & HAZ) were calculated: CD4 cell % and HIV-1 RNA were measured at baseline and every 12 weeks. Treatment outcomes were classified according to; both virological and immunological success (VS/IS), virological failure and immunological success (VF/IS). virological success and immunological failure (VS/IF) and both virological and immunological failure (VF/IF).

Results

From March 2004 until May 2006, 124 HIV infected children were initiated on HAART. The median age (IQR) was 5.0 years (2.1 - 7.0) and 49% (61/124) were female. The median [95% confidence interval (CI)] BAZ, WAZ and HAZ at baseline were 0.29 (-2.9, -1.2), -1.2 (-2.1, -0.5) and -2.06 (-2.9, -1.2) respectively. Baseline median CD4 cell % and log10 HIV-1 RNA were; 11.8% (7.5-18.0) and 5.6 (5.2-5.8) copies/ml. By 48 weeks, mean WAZ and HAZ in the VF/IS group, which was younger, increased from - 0.98 (SD 1.7) to + 1.22 (SD 1.2) and from -1.99 (1.7) to + 0.76 (2.4) respectively. Mean increase in WAZ and HAZ in the VS/IF group, an older group was modest, from -1.84 (1.3) to - 0.41 (1.2) and -2.25 (1.2) to -1.16 (1.3) respectively. Baseline CD4 cell % [OR 6.97 95% CI (2.6 -18.6)], age [OR 4.6 95% CI (1.14 -19.1)] and WHO clinical stage [OR 3.5 95%CI (1.05 -12.7)] were associated with successful treatment outcome.

Conclusions

HIV infected Ugandan children demonstrated a robust increase in height and weight z scores during the first 48 weeks of HAART, including those who failed to completely suppress virus. Older children initiating HAART with severe immune suppression were less likely to achieve a successful treatment outcome. These data emphasize the importance of initiating HAART early to ensure adequate immune and growth responses.

The influence of nutritional status on the response to HAART in HIV-infected children in South Africa

BACKGROUND

While the impact of HAART on growth in children is well established, the influence of prior nutritional status on the response to HAART is not well known.

METHODS

A retrospective study was conducted on 120 children in South Africa. Patients were divided into 3 groups (normal, moderately underweight, and severely underweight) based on weight-for-age z-scores (WAZ). Age, weight, height, CD4 cell percentage, and viral load were recorded at initiation of HAART and after 24 months of therapy. Data were analyzed using t-tests, chi tests, and one-way ANOVA.

RESULTS

At baseline, 58% of children were normal weight, 18% moderately underweight, and 23% severely underweight. After 24 months of HAART, WAZ improved significantly in moderately and severely underweight patient groups compared with the normal group. Height-for-age z-scores (HAZ) increased in all 3 groups with severely underweight children gaining more height than normal weight counterparts. Weight-for-height z-scores (WHZ) normalized in the severely underweight group. Mean CD4 cell percentages increased significantly in all 3 groups while viral loads decreased significantly in all groups with no differences among the groups at the end of 24 months of therapy. Of the entire cohort, 75% achieved undetectable HIV RNA viral loads.

CONCLUSIONS

Underlying malnutrition does not adversely affect growth, immunologic or virologic response to HAART in HIV-infected children. Underweight children exhibit an equally robust response to treatment as their well-nourished peers.

Relevance of CD38 expression on CD8 T cells to evaluate antiretroviral therapy response in HIV-1-infected youths

Surrogate markers for monitoring immuno-virological discordant responders, in addition to plasma viral load and CD4 cells, are still lacking. We assessed the diagnostic utility of CD38 expression on CD8 T cell assay, alone or in association with lymphocyte proliferation to mycotic antigens, in evaluating antiretroviral response. 28 vertically HIV-infected youths, 21 HAART- and seven 2 nucleotide reverse transcriptase inhibitors-treated, were enrolled in a retrospective study. Responders (57.1%) and non-responders (42.9%) to stable antiretroviral therapy for a minimum of 6 months, on the basis of viral load and CD4 T cells, comprehensively evaluated by CD38 expression on CD8 T lymphocytes [measured as CD38 antibody bound per CD8 T cell (CD38 ABC) and %CD38+ of total CD8 T cells (%CD38/CD8)] and lymphocyte proliferation to P. jiroveci, C. albicans, C. neoformans, A. fumigatus at a single time point after treatment, were selected. CD38 expression > or =2401 CD38 ABC and > or =85% CD38/CD8 cut-off points, accurately discriminates responders versus non-responders, both measures resulting in 75.0% (CI 42.8-94.5) sensitivity (identification of non-responder) and 93.8% (CI 69.8-99.8) specificity (identification of responder), when considered as single assays. The association '> or =2401 CD38 ABC or > or =85% CD38/CD8' improved sensitivity to 83.3% (CI 51.6-97.9), while the association '<2401 CD38ABC (or <85% CD38/CD8) and lymphoproliferative response positive to > or =2 tested organisms' improved specificity to 100% (CI 79.4-100). In conclusions, CD38 expression and mycotic antigen-specific T-cell proliferation may be used as additional parameters to existing criteria to evaluate antiretroviral response in immuno-virological discordant patients.

Genetic determinants in HIV-1 Gag and Env V3 are related to viral response to combination antiretroviral therapy with a protease inhibitor

OBJECTIVE

To identify novel viral determinants in HIV-1 protease, Gag, and envelope V3 that relate to outcomes to initial protease inhibitor-based antiretroviral therapy.

DESIGN

A longitudinal cohort study of protease inhibitor-naive, HIV-infected individuals was designed to identify genetic variables in viral Gag and envelope sequences associated with response to antiretroviral therapy.

METHODS

Genetic and statistical models, including amino acid profiles, phylogenetic analyses, receiver operating characteristic analyses, and covariation analyses, were used to evaluate viral sequences and clinical variables from individuals who developed immune reconstitution with or without suppression of viral replication.

RESULTS

Pretherapy chemokine (C-X-C motif) receptor 4-using V3 regions had significant associations with viral failure (P = 0.04). Amino acid residues in protease covaried with Gag residues, particularly in p7(NC), independent of cleavage sites. Pretherapy V3 charge combined with p6(Pol) and p2/p7(NC) cleavage site genotypes produced the best three-variable model to predict viral suppression in 88% of individuals. Combinations of baseline CD4 cell percentage with genetic determinants in Gag-protease predicted viral fitness in 100% of individuals who failed to suppress viral replication.

CONCLUSION

Baseline genetic determinants in Gag p6(Pol) and p2/p7(NC), as well as envelope, provide novel combinations of biomarkers for predicting emergence of viral resistance to initial therapy regimens.

CD8+ T-cell interleukin-7 receptor alpha expression as a potential indicator of disease status in HIV-infected children

BACKGROUND

Initiation and modification of antiretroviral therapy in HIV-infected children depend on viral load and CD4+ T-cell count. However, these surrogates have limitations, and complementary immunological markers to assess therapeutic response are needed. Our aim was to evaluate CD8+ T-cell expression of CD127 as a marker of disease status in HIV-infected children, based on adult data suggesting its usefulness. We hypothesized that CD127 expression on CD8+ T-cells is lower in children with more advanced disease.

METHODS

In a cross-sectional evaluation, we used flow cytometry to measure CD127+ expression on CD8+ T-cells in whole blood from HIV-infected children with varying disease status. This was compared with expression of CD38 on this subset, currently used in clinical practice as a marker of disease status.

RESULTS

51 HIV-infected children were enrolled. There was a strong positive correlation between CD127 expression on CD8+ T-cells and CD4+ T-cell count, and height and weight z-scores, and a strong negative correlation between CD127 expression and viral load. In contrast, we found no association between CD38 expression and these disease status markers.

CONCLUSIONS

CD8+ T-cell CD127 expression is significantly higher in children with better HIV disease control, and may have a role as an immunologic indicator of disease status. Longitudinal studies are needed to determine the utility of this marker as a potential indicator of HIV disease progression.

Impaired immunity to recall antigens and neoantigens in severely immunocompromised children and adolescents during the first year of effective highly active antiretroviral therapy

BACKGROUND

We studied whether severely immunocompromised, human immunodeficiency virus (HIV)-infected children who were beginning highly active antiretroviral therapy (HAART) or changing HAART regimens could spontaneously respond to a recall antigen (tetanus toxoid [TT] vaccine) or respond to a recall antigen and neoantigen (hepatitis A virus [HAV] vaccine) after 3 vaccinations.

METHODS

A total of 46 children who had CD4 cell percentages <15% and who demonstrated a >0.75-log reduction in plasma HIV RNA levels within 4 weeks of starting HAART were randomized to receive vaccinations with either TT or HAV vaccines during the first 6 months of HAART. Study subjects then received the alternate vaccine during the next 6 months of HAART.

RESULTS

Despite the early decline in viremia and the later increase in the percentage of CD4 T cells, spontaneous recovery of cell-mediated immunity (CMI) was not seen for TT. Serologic responses to TT required 3 vaccinations and were comparable in both groups. Serologic responses to HAV were infrequent and of low titer, although the group that received HAV vaccine after receiving TT vaccine performed somewhat better. CMI to HAV was virtually absent.

CONCLUSIONS

Severely immunocompromised children who are receiving HAART develop CMI and antibody to a recall antigen independent of the timing of vaccination, but they require a primary series of vaccinations. Antibodies to a neoantigen, HAV, developed when vaccination was delayed after initiation of HAART. CMI to a neoantigen was difficult to establish.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT00004735/PACTG P1006 .

Impact of Delta 32-CCR5 heterozygosity on HIV-1 genetic evolution and variability--a study of 4 individuals infected with closely related HIV-1 strains

A cluster of four patients acutely infected with a genetically almost identical virus, allowed us to investigate genetic variability and disease progression in early HIV-1 infection with minimal interference of virus specific factors. Two of the patients were heterozygous for the 32-bp deletion in the CCR5 coreceptor gene. Both showed a slower disease progression with lower viral load levels and a reduced rate of genetic evolution compared to the patients with normal CCR5 alleles. During 3 years of treatment-free follow-up, the mean pairwise genetic distance increased with 1.45% and 1.58% in the two patients with a 32-bp deletion allele compared to 3.05% and 3.57% in the two patients with normal CCR5 alleles. The observed relation between slower disease progression and a reduced evolutionary rate illustrates the influence of the virus replicative capacity, here most possibly hampered by the CCR5 heterozygosity in two of the four individuals, on the genetic evolution of the virus in the host.

Long-term effects of highly active antiretroviral therapy on CD4+ cell evolution among children and adolescents infected with HIV: 5 years and counting

BACKGROUND

Lower percentages of CD4(+) T lymphocytes are associated with adverse clinical outcomes among children and adolescents infected with human immunodeficiency virus (HIV). CD4(+) lymphocyte percentage generally increases with receipt of highly active antiretroviral therapy (HAART), but long-term follow-up is required to assess whether these increases in CD4(+) cell percentage are maintained and whether they lead to normal CD4(+) cell percentages in children with severe immunosuppression.

METHODS

The study population included 1236 children and adolescents perinatally infected with HIV who were enrolled in a US-based multicenter prospective cohort study (Pediatric AIDS Clinical Trials Group 219/219C) and who were not receiving HAART at study initiation. We estimated the effects of HAART, HAART with protease inhibitors, and HAART with nonnucleoside reverse-transcriptase inhibitors on CD4(+) cell percentage, using marginal structural models to account for confounding by severity.

RESULTS

Initiation of any type of HAART increased CD4(+) cell percentage by 2.34% (95% confidence interval, 1.35%-3.33%) in the first year, relative to noninitiation of HAART. The substantial increases in CD4(+) cell percentage observed after the first year of experience with these combination therapies were followed by relatively smaller increases that continued for 5 years after initiation. Although larger increases in CD4(+) cell percentage were observed among children with a greater degree of immunosuppression at baseline, the mean CD4(+) cell percentage after 5 years of HAART did not reach normal levels.

CONCLUSIONS

Our study supports the initiation of HAART in children before severe immunosuppression occurs for long-term maintenance of normal CD4(+) cell percentages. This beneficial result must be weighed against the evidence of potential adverse events associated with the prolonged use of such therapy.

Clinical implications of discordant viral and immune outcomes following protease inhibitor containing antiretroviral therapy for HIV-infected children

Many HIV-infected children treated with protease inhibitors (PI) reconstitute immunity despite viral breakthrough predicting disease progression. We studied a unique cohort of PI treated children with advanced disease who demonstrated sustained CD4 T cell counts but median post therapy viral load rebounded to >4.0 log(10) copies/ml. Phylogenetic relationships between pre- and post-therapy viruses reveals significant bottlenecks for quasispecies with natural polymorphisms mapping outside of protease active site providing selective advantage for emergence. Among discordant subjects post-therapy viruses fell into two phenotypes; high viral loads (median >5.0 log(10) copies/ml) and attenuated post-therapy replication (median <4.0 log(10) copies/ml). Both groups showed similar degrees of CD4 T cell immune reconstitution and were similar to children who optimally suppressed virus to <400 copies/ml. Both high fit and low fit discordant response groups showed high reconstitution of naïve CD4 CD45RA T cells (median 388 and 357 cells/microl, respectively). Naïve T cells increases suggest virus replicating under PI selective pressure do not impair thymic output. If therapeutic options are limited, selection of therapy which allows immune reconstitution despite suboptimal viral control may be beneficial. This novel paradigm for virus/host interactions may lead to therapeutic approaches to attenuate viral pathogenesis.

Chinese pediatric highly active antiretroviral therapy observational cohort: a 1-year analysis of clinical, immunologic, and virologic outcomes

BACKGROUND

Few data are available on the outcomes of pediatric antiretroviral therapy (ART) in the developing world.

METHODS

Eighty-three children were followed prospectively in China from July 2005 to August 2006 and received (zidovudine or stavudine) plus lamivudine plus (nevirapine or efavirenz).

RESULTS

Fifty-one children were ART naive at enrollment, and 32 were ART experienced. After 12 months, median weight increased by 0.3 weight for age z-score, median CD4 count increased from 116 to 340 cells/mm (P < 0.0001), and median viral load decreased from 5.53 to <2.60 log10 copies/mL (P < 0.0001) in the previously ART-naive children. In the ART-experienced children, median CD4 count increased from 193 to 318 cells/mm (P = 0.13), despite little change in median viral load (4.85 to 4.58 log10 copies/mL; P = 0.83). The viral load was <400 copies/mL in 55% of the previously ART-naive children and in 16% of the ART-experienced children.

CONCLUSIONS

Weight and CD4 cell counts improved, and more than half of previously ART-naive patients had undetectable viral loads at 1 year. Future efforts should focus on improved virologic suppression through improved adherence and access to second-line regimens.

Efficacy of highly active antiretroviral therapy in HIV-1 infected children in Kenya

OBJECTIVE

Few studies have investigated the efficacy of antiretroviral therapy among HIV-infected children in resource-poor settings. This observational, retrospective analysis describes the clinical, immunologic, and virologic effects of highly active antiretroviral therapy in treatment-naive, HIV-infected children in Mombasa, Kenya. In keeping with a public health approach, all children were treated by using a simplified, nationally approved, triple-drug regimen.

METHODS

Clinical data and stored plasma samples from 29 children who were followed prospectively between April 2003 and October 2004 were analyzed. All children received generic formulations of nevirapine, zidovudine, and lamivudine and were evaluated at baseline and at 3, 6, 9, 12, and 15 months. At each visit, weight and CD4 lymphocyte counts were measured and plasma samples were stored for analysis. HIV RNA load was determined retrospectively at baseline and 9 months after initiation of therapy.

RESULTS

The mean age of the children was 8.5 years (range: 2-16 years). At baseline, the mean CD4 count (+/-SD) was 182.3 x 10(6) cells per microL (+/-145.6). On treatment, CD4 counts increased step-wise by a mean of 187 x 10(6) cells per microL at 3 months, 293 cells per microL at 6 months, 308 cells per microL at 9 months, 334 cells per microL at 12 months, and 363 cells per microL at 15 months. The mean plasma viral load decreased from a baseline level of 622,712 to 35,369 copies per mL, and at 9 months was undetectable in 55% of the patients. Mean z scores for weight for age increased from a baseline of -1.61 to -1.12 at 12 months into therapy.

CONCLUSIONS

A public health approach using 1 treatment regimen in generic form showed excellent efficacy among treatment-naive, HIV-infected children in a resource-limited country. Clinical and immunologic improvement occurred in all patients, but 9 months after the start of therapy, only 55% of the children had an undetectable viral load.

Immunologic, virologic, and neuropsychologic responses in human immunodeficiency virus-infected children receiving their first highly active antiretroviral therapy regimen

Our objective was to measure the early dynamics, evolution, and durability over 96 wk of immunologic responses in children receiving their first highly active antiretroviral therapy (HAART) regimen. The study was designed as a prospective, single-arm study. Twelve human immunodeficiency virus (HIV)-infected children (median age, 11.8 yr) were enrolled. All subjects received stavudine, nevirapine, and ritonavir. Serial measurements included HIV viral load, lymphocyte subsets, thymic volume by computed tomography (CT), neurocognitive testing, and brain CT. Baseline median CD4(+) T cell count was 589 cells/mm(3) , viral load was 3.9 log(10) HIV RNA copies/mL, and thymic volume was 16.3 cm(3) . Ten children had an undetectable viral load at week 48. Eight maintained an undetectable viral load at 96 wk. The median increase in absolute CD4(+) T cell count was 225 cells/mm(3) by week 48, and 307 cells/mm(3) by week 96. The median increase in naive (CD45RA(+) CD62L(+) ) CD4(+) T cells was 133 cells/mm(3) by week 48, and 147 cells/mm(3) by week 96. The median number of naive CD8(+) T cells increased from 205 to 284 cells/mm(3) by week 24; this increase was sustained to week 96. The number of B cells increased and was associated with a decrease in immunoglobulin levels. The number of natural killer cells was stable. There were no significant changes in thymic volume. Most children exhibited stable cognitive function over the course of the study. We conclude that, in this cohort of relatively immunocompetent HIV-infected children, an initial HAART regimen was associated with rapid and sustained increases in total CD4(+) T cells, in naive CD4(+) and CD8(+) T cells, and in B cells through 96 wk.

HIV-1-infected children on HAART: Immunologic features of three different levels of viral suppression

BACKGROUND

HIV-1-infected children show changes of blood lymphocyte subpopulations. We have, therefore, investigated how highly active anti-retroviral therapy (ART) alter these subsets. Blood samples were taken from 41 HIV-1-infected children on ART who were divided into groups showing good, partial and poor responses to ART on the basis of viral load (VL) measurement in blood. The observations were compared to those seen in 20 uninfected children.

METHODS

The samples were studied using 4-color flow cytometry for "naïve", central memory and effector memory cells as well as for CD38 expression as the sign of activation within both the CD4+ and the CD8+ T cell populations. HIV-1 infected children were also evaluated for the presence and the titers of antibodies induced by vaccination against childhood infections in our patients while on HAART.

RESULTS

Lymphocyte counts were lower in the "poor" viral load responding (VLR) group when compared with partial and good VLRs. Poor VLRs had lower total and naïve CD4+ T cell counts. HIV-1-infected children from all three groups had high CD8+ T cell counts. Central memory CD4+ and CD8+ T cell percentages were particularly low in the poor VLR group while in the poor VLR group the percentages of effector memory CD4+ and CD8+ T cells were higher when compared with the control group. Higher cellular activation of CD8+ T cells was observed in HIV-1-infected children, particularly when analyzed for the intensity of CD38 expression in the poor VLR group. CD5 expression on B cells was higher among all HIV-1-infected children. Antibodies to tetanus, diphtheria, measles, rubella, and hepatitis B were present in a large proportion of children but the titers were similarly low for all three groups of HIV-infected children.

CONCLUSIONS

Children with different levels of viral response to HAART present immune phenotype characteristics that tend to place the children with partial and good virological responses into the same group. These children are still moderately deficient in their immune responses but show better recovery than seen with children in the poor VLR group. These observations indicate that the proportions of central memory cells among the CD4+ T cells and the intensity of the expression of CD38 activation antigen on CD8+ T cells provide more informative parameters for monitoring children on HAART than the absolute numbers of CD4+ and CD8+ T cells alone.

Thymic function in HIV infection

Current models hold that CD4+ depletion occurs as a result of direct and indirect effects of HIV, which both kill peripheral CD4+ cells and prevent adequate regeneration. Although age-associated involution diminishes thymic reserve and HIV is clearly thymotoxic, clinical trials have nonetheless shown that large proportions of patients who sustain adequate control of viral replication with highly active antiretroviral therapy (HAART) will demonstrate some evidence for thymic-dependent immune reconstitution, which is associated with improved immune competence. Furthermore, patients with insufficient or absent immune reconstitution following HAART generally lack evidence for thymopoiesis. Current studies are focused on improving our understanding of the causes for thymic failure in HIV infection. Recent work has demonstrated that some HIV strains, especially those that are CXCR4 trophic, are more thymotoxic and may contribute to irreversible thymic damage in this population.

Protease inhibitor combination therapy, severity of illness, and quality of life among children with perinatally acquired HIV-1 infection

OBJECTIVES

This study examines quality of life (QOL) among school-aged children with perinatally acquired HIV infection and compares QOL outcomes between treatment groups that differ according to the use of protease inhibitor (PI) combination therapy (PI therapy). To gain insights into how PI therapy might influence QOL, associations between severity of illness and QOL were also investigated.

METHODS

Cross-sectional data for 940 children, 5 to 18 years of age, who were enrolled in Pediatric AIDS Clinical Trials Group Late Outcomes Protocol 219 were used to examine domains of caregiver-reported QOL, as assessed with the General Health Assessment for Children, during 1999. The General Health Assessment for Children is an age-specific, modular, QOL assessment that was developed for the study with previously validated measures. QOL differences between treatment groups were estimated with linear and logistic regressions that controlled for sociodemographic characteristics (age, gender, race/ethnicity, maternal/caregiver education, and respondent) and severity-of-illness indicators related to receipt of PI therapy (AIDS status, log(10) CD4+ cell counts, and height-for-age z scores).

RESULTS

The mean age of participants was 9.7 years. Most children were non-Hispanic black (54%) or Hispanic (31%), and 49% of the participants were female. At the 1999 study visit, approximately 14% of children had severe immune suppression (<15% CD4+ cells), whereas 62% of children had > or =25% CD4+ cells, ie, no immune suppression. Participants did exhibit some lag in growth, with mean height and weight z scores of -0.70 and -0.20, respectively. Twenty-eight percent of the children were reported to have met criteria for AIDS at study entry (1993-1999). When treatment groups were compared, children receiving PI therapy (72%) were older, had lower CD4+ cell percentages, and had lower height and weight z scores than did those receiving non-PI therapies. They were also more likely to have met criteria for AIDS at study entry. The most commonly used PIs were ritonavir (46%) and nelfinavir (63%). Health perceptions ratings for most children were at the upper end of the scale, whereas ratings for 25% of the children ranged over the lower 70% of scale scores. Almost one half of the children had at least some limitations in physical functioning, with more frequent limitations in energy-demanding activities (46%) than in basic activities of daily living (32%). The Behavior Problems Index was used to assess psychologic functioning. The mean total Behavior Problems Index score (9.34) and the proportion of children with extreme scores (23%) were consistent with values reported for chronically ill children and those at social and economic risk. One or more limitations in social/school functioning were reported for 58% of children. More than one third of the children (38%) experienced > or =1 physical symptoms that were at least moderately distressing. Health perceptions, physical functioning, psychologic functioning, social/school functioning, and overall HIV symptom scores did not differ between treatment groups. However, receipt of PI therapy was associated with an increased rate of diarrhea (28 vs 13%; adjusted odds ratio: 2.59; 95% confidence interval: 1.74-3.85). Severity of illness was associated with QOL in all domains except psychologic functioning. Higher log(10) CD4+ cell counts, higher height-for-age z scores, and absence of AIDS at study entry were independently associated with fewer social/school limitations and better HIV symptom scores. Health perceptions and physical functioning scores were associated with log(10) CD4+ cell counts and height z scores, respectively.

CONCLUSIONS

QOL among children receiving PI therapy differed little from that among children receiving non-PI therapy, despite clinical indications of more advanced disease. Importantly, the study found no evidence of direct negative effects of PI therapy on QOL outcomes, other than an increased rate of diarrhea. Findings suggest that the effects of PI combination therapies to slow or to prevent disease progression and to increase CD4+ cell counts and height growth have the potential to improve QOL among children with HIV infection. However, many children do experience a constellation of functional impairments indicated by behavioral problems and clinical symptoms, with limitations in activities and in school performance. Comprehensive health services will continue to be required to minimize long-term illness and disability and to maximize children's potential as they move into adolescence and adulthood.

Relationship between Changes in Thymic Emigrants and Cell-Associated HIV-1 Dna in HIV-1-Infected Children Initiating Antiretroviral Therapy

Objectives and methods

To investigate the relationship between cell-associated HIV-1 dynamics and recent thymic T-cell emigrants, HIV-1 DNA and T-cell receptor rearrangement excision circles (TREC, a marker of recent thymic emigrants) were measured in peripheral blood mononuclear cells in 181 samples from 33 HIV-1-infected children followed for 96 weeks after antiretroviral therapy (ART) initiation.

Results

At baseline, HIV-1 DNA was higher in children with higher TREC ( P=0.02) and was not related to age, CD4 or HIV-1 RNA in multivariate analyses ( P>0.3). Overall, TREC increased and HIV-1 DNA decreased significantly after ART initiation, with faster HIV-1 DNA declines in children with higher baseline TREC ( P=0.009). The greatest decreases in HIV-1 DNA occurred in children with the smallest increases in TREC levels during ART ( P=0.002). However, this inverse relationship between changes in HIV-1 DNA and TREC tended to vary according to the phase of HIV-1 RNA decline ( P=0.13); for the same increase in TREC, HIV-1 DNA decline was much smaller during persistent or transient viraemia compared with stable HIV-1 RNA suppression.

Conclusions

Overall, these findings indicate that TREC levels predict HIV-1 DNA response to ART and suggest that immune repopulation by thymic emigrants adversely affects HIV-1 DNA decline in the absence of persistent viral suppression, possibly by providing a cellular source for viral infection and replication.

Genotypic and phenotypic correlates of the HIV Type 1 env gene evolution in infected children with discordant response to antiretroviral therapy

The genotypic-phenotypic correlates of human immunodeficiency virus type 1 (HIV-1) env gene evolution were investigated in samples from eight infected children under antiretroviral therapy (ART) and virological failure. Evolution of the gp120 C2-V5 env sequence was demonstrated in all subjects but one by sequence analysis of the replicating plasma virus collected at baseline and 12-15 months after ART initiation. The analysis of the host's selective pressure showed that in four subjects, the ratio of nonsynonymous to synonymous amino acid substitutions was higher in the V3 sequences than in the C2-V5 region ([K (a)/K (s)](V3)/[K (a)/K (s)](C2V5) >1.0). Interestingly, this feature was observed only in subjects (four of five) showing an increase in T cell receptor rearrangement excision circle (TREC)-bearing cells and in CD4(+) T-lymphocytes despite persistent viremia (discordant therapeutic response) (p = 0.02), thus suggesting that the V3 loop is a target of the immune reconstitution under ART. Using phenotypic analysis of recombinant viruses expressing exogenous V3 sequences, a reverse shift from CXCR4-tropic to CCR5-tropic variants was demonstrated in two of the four subjects, further indicating that the host's selective pressure sharply forces the V3 evolution of replicating variants. The data indicate that a complex HIV-1-host interplay occurs in children receiving antiretroviral treatments and suggest that the recovery of thymic function places a selective constraint on the viral V3 loop.

Two-year clinical and immune outcomes in human immunodeficiency virus-infected children who reconstitute CD4 T cells without control of viral replication after combination antiretroviral therapy

OBJECTIVE

To evaluate 96-week clinical and immune outcomes to protease inhibitor-containing antiretroviral therapy.

METHODS

A prospective study was conducted of 40 human immunodeficiency virus (HIV)-infected children who displayed viral suppression (VS) with successful immune reconstitution (IS), failure to suppress virus (VF) or develop immune reconstitution (IF), or discordant immune and viral responses (VF/IS) at 24 weeks posttherapy. All children enrolled had viral RNA >4.0 log10 copies per mL and were Centers for Disease Control ad Prevention immune stage 2 or 3. Clinical, viral, and immune outcomes were assessed during the subsequent 72 weeks.

RESULTS

VS/IS and VF/IS groups displayed similar sustained increases in CD4 T cells, although viral levels rebounded by 48 and 96 weeks posttherapy to pretherapy levels in the discordant group. The VF/IS outcome group had significant increases in height and weight z scores compared with entry and were similar to the VS/IS group. After treatment, antigen-specific responses after tetanus immunization were similar in the VF/IS and VS/IS groups. Prevalence of HIV-associated illnesses decreased in both VS/IS and VF/IS but not in VF/IF response groups.

CONCLUSIONS

The findings indicate that viral replication under the selective pressure of protease inhibitors fails to exhibit the same deleterious impact on T-cell immunity as pretherapy viruses. CD4 T-cell counts may be a better predictor of disease progression and improvement in growth than viral burden in HIV-infected children who receive a protease inhibitor as part of a highly active antiretroviral therapy regimen.

Highly active antiretroviral therapies among HIV-1-infected children in Abidjan, Côte d'Ivoire

OBJECTIVE

To describe the effect of highly active antiretroviral therapy (HAART) in HIV-1-infected African children.

STUDY DESIGN

Observational ANRS 1244 cohort of 159 children with HIV between October 2000 and September 2002; 78 children (49%) receiving HAART were followed for a mean duration of 21 months.

METHODS

Weight-for-age Z-scores (WAZ), height-for-age Z-scores (HAZ), CD4 lymphocyte count and HIV-1 RNA viral load were measured before initiating HAART and every 6 months during treatment. Probability of survival and incidences of pneumonia and acute diarrhoea were calculated.

RESULTS

Values before and after 620 days of HAART, respectively, were -2.02 and -1.39 for mean WAZ, (P < 0.01); -2.03 and -1.83 for mean HAZ (P = 0.51); 0.07 and 0.025/child-month (P = 0.002) for incidence of pneumonia; and 0.12 and 0.048/child-month for incidence of acute diarrhoea (P < 0.001) (incidence changes statistically significant only in children < 6.5 years). Overall, the probability of survival under HAART was 72.8% at 24 months for children with < 5% CD4 cells versus 97.8% in children with >/= 5% (P < 0.01). At HAART initiation, median viral load and CD4 cell percentage were 5.41 log10 copies/ml and 7.7%, respectively. After 756 days of HAART, on average, 50% of patients had undetectable viral load and 10% had 2.4-3.0 log10 copies/ml. The median CD4 percentage was 22.5%.

CONCLUSION

In resource-limited setting, it is possible to use HAART to treat African children. This treatment appears as effective as in developed countries.

Response to highly active antiretroviral therapy varies with age: the UK and Ireland Collaborative HIV Paediatric Study

OBJECTIVE

To evaluate the effect of age, CD4 percentage (CD4%) and plasma HIV-1 RNA on response to highly active antiretroviral therapy (HAART) in previously untreated children.

DESIGN

Cohort study.

METHODS

We examined the association between age at HAART initiation, and CD4 and HIV-1 RNA response using logistic and Cox regression, adjusting for sex, route of infection and pre-HAART values.

RESULTS

CD4% increases of > 10% at 6 months were more likely in younger children [odds ratio (OR), 0.84 per year, P < 0.001] and those with lower pre-HAART CD4% (OR, 0.67 per 5% higher, P < 0.001), but were not related to pre-HAART HIV-1 RNA (P = 0.6). In contrast, HIV-1 RNA suppression < 400 copies/ml at 6 months was more likely in older children (OR, 1.09 per year, P = 0.03), and was unrelated to pre-HAART HIV-1 RNA or CD4% (P > 0.3). CD4% was still increasing during the second year following HAART initiation (60% followed > 24 months). Longer-term increases in CD4% occurred faster, and decreases in HIV-1 RNA occurred more slowly in younger children. The median time to CD4% >/= 30% after initiating HAART with CD4% </= 25% was under 12 months for children under 2 years irrespective of pre-HAART CD4%, and increased progressively in older children and as CD4% decreased.

CONCLUSIONS

Children respond immunologically to HAART irrespective of pre-HAART HIV-1 RNA or clinical status. However, immunological response is better in younger children and those with lowest CD4%, whereas younger children have poorer virological response, increasing the risk of resistance. Differences in response to HAART according to age and underlying risk of disease progression should be considered when initiating HAART in children.

Genotypic resistance and HIV-1 subtype in Brazilian children on dual and triple combination therapy

BACKGROUND

Antiretroviral therapy is provided by the Brazilian Ministry of Health to eligible HIV-infected individuals. Based on clinical and immunological classification, the Brazilian guidelines recommend dual or triple therapy for children. However, the development of drug-resistant strains or poor adherence to therapy could impact the efficacy of this approach.

OBJECTIVES

We examined relationships between RNA levels, CD4+ T-cell counts, treatment history, and the prevalence of drug-resistant variants in a cohort of HIV-1-infected children in Rio de Janeiro, Brazil.

STUDY DESIGN

Direct sequencing of reverse transcriptase and protease genes from plasma was performed. Virologic and CD4+ T-cell counts responses to therapy were assessed by changes in HIV-1 RNA levels and CD4+ T-cell counts from baseline.

RESULTS

Thirty-seven patients were receiving dual therapy and 38 were on triple therapy at enrollment, segregated by antiretroviral history. Both groups had a higher increase in CD4+ T cell counts and a lower viral load in pre-treatment antiretroviral-naïve subjects. Notably, there was a direct correlation between the higher frequencies of drug-resistance mutations and cross-resistance with previous usage of antiretroviral (ARV) therapy in both groups. Non-B subtypes isolates were found in 21.3% of samples. A smaller increase in CD4+ T cell counts was found between non-B subtypes when compared to B-subtypes.

CONCLUSIONS

These results suggest that less immunological recovery and a higher number of mutations related to drug resistance were associated with previous usage of ARV and consequent higher time under drug selective pressure in these HIV-infected Brazilian children. These facts suggest the preferential use of triple drug combination as first line regimen in children.

Antimicrobial-Specific Cell-Mediated Immune Reconstitution in Children with Advanced Human Immunodeficiency Virus Infection Receiving Highly Active Antiretroviral Therapy

To identify virological and immunological correlates of microbial-specific immune reconstitution in children with advanced human immunodeficiency virus (HIV) infection, Candida- and tetanus-specific lymphocyte proliferation was measured in 165 children initiating a new highly active antiretroviral therapy (HAART) regimen. During the study, the proportions of children with immunity to Candida and tetanus increased from 53% to 66% and 19% to 22%, respectively. Tetanus immunity was associated with an HIV load < or =400 RNA copies/mL and with Candida immunity. At the end of the study, 23% of the patients with baseline negative lymphocyte proliferation had tetanus immunity, and 65% had Candida immunity. Reconstitution of tetanus immunity correlated with lower end-of-study HIV loads and activated CD8+ cell percentages and higher baseline and in-study CD4+ cell percentages, but not with a gain of CD4+ cells. Reconstitution of Candida immunity showed similar trends. In conclusion, children with advanced HIV infection receiving HAART reconstituted Candida immunity more readily than they did tetanus immunity, suggesting a role for antigen reexposure. Additional factors for immune reconstitution were low HIV load, high CD4+ cell percentages, and low levels of activated CD8+ cells.

Principles of antiretroviral treatment of children and adolescents with human immunodeficiency virus infection

Human immunodeficiency virus (HIV) infection requires life-long therapy to attain durable suppression of HIV replication and prevent or reverse HIV-related symptoms or immune system dysfunction. Combination therapy with 3 or more antiretroviral medications is currently widely recommended for treatment of children and adolescents with HIV infection. While potent regimens can initially reduce virus load to below assay quantitation limits in the majority of persons with HIV infection, 30% to 80% of children will have regimen failure and return of detectable plasma virus within 1 year. Adherence to therapy is critical to regimen success. Optimal treatment requires careful use of potent combinations of drugs, with attention to adherence, palatability, toxicity, and pharmacokinetics. Practitioners with experience caring for children and adolescents with HIV infection should be involved.

[Recommendations for initial antiretroviral treatment in HIV-infected children. Update 2003]

Highly active antiretroviral therapy in HIV-infected children has been associated with a dramatic decrease in progression to AIDS and HIV-related deaths, and infected children currently have an excellent quality of life. Antiretroviral drugs cannot eradicate the virus, although they can achieve a situation of latent infection. However, chronic use of these drugs has multiple adverse effects, the most important of which are metabolic complications. The large number of drugs required and patient characteristics such as age, tolerance to drugs, adherence, and social problems make unifying the criteria for initial therapy in HIV-infected children difficult. A balance should be sought between not delaying the start of treatment, to avoid immunologic deterioration, and minimizing the long-term adverse effects of the therapy. The present treatment recommendations are adapted from international guidelines and are based on a literature review and on our own experience. Our group previously published recommendations on the treatment of HIV-infected children and the aim of the present article is to provide an update.

The CCR5 and CXCR4 coreceptors--central to understanding the transmission and pathogenesis of human immunodeficiency virus type 1 infection

In this review, we will discuss what is known, what is suspected, and what still remains obscure about the central role played by coreceptor expression and usage in the transmission and pathogenic consequences of human immunodeficiency virus type 1 (HIV-1) infection. An emphasis will be on the HIV-1 phenotypic variants that are defined by their usage of the CCR5 or CXCR4 coreceptors, and how the different cellular tropism of these variants influences how and where HIV-1 replicates in vivo. We will also review what might happen when coreceptor antagonists are used clinically to treat HIV-1 infection.

Long-term effects of protease-inhibitor-based combination therapy on CD4 T-cell recovery in HIV-1-infected children and adolescents

BACKGROUND

There is limited evidence about longer-term effects of combination antiretroviral therapy that includes protease inhibitors (PIs) on the immunological status of HIV-1-infected children. Better understanding might help to resolve questions on when to initiate treatment.

METHODS

The change in percentage of CD4-positive T lymphocytes (CD4%) was investigated in 1012 previously treated HIV-1-infected children (aged 0-17 years) who were enrolled in research clinics in the USA before 1996 and followed up to 2000. 702 started PI-based combination therapy. Data analyses ignored subsequent treatment changes.

FINDINGS

Among the 1012 children, the median CD4% increased from 22% to 28% between 1996, when PIs were first prescribed, and 2000. For the 702 who started PI-based therapy, the mean CD4% increase after 3 years was largest among participants with the greatest immunosuppression (15.7%, 10.6%, 5.1%, and 2.0% for participants with CD4% before therapy of <5%, 5-14%, 15-24%, and >25%; p<0.0001). After adjustment for pre-PI CD4%, the mean increase was largest among the youngest participants (9.2%, 8.0%, and 4.3% for ages <5 years, 5-9 years, and >10 years; p=0.001). However, only a minority of significantly immunocompromised participants (33%, 26%, and 49% of those with pre-PI CD4% of <5%, 5-14%, or 15-24%) achieved CD4% values above 25%, whereas 84% of those with pre-PI values above 25% maintained such values.

INTERPRETATION

Although PI-based therapy was associated with substantial improvements in CD4%, initiation before severe immunosuppression and at younger ages may be more effective for recovery or maintenance of normal CD4%. Randomised investigation of when to start combination therapy in children, particularly infants, is needed.

HIV-1 fitness and macrophages

HIV-1 comprises a collection of closely related, but not identical, viruses or quasispecies. Fitness represents a selective advantage for propagation among populations of organisms competing in a particular environment and is an important characteristic of viruses because of a link between fitness and pathogenesis. Environmental differences based on the type of cell that is targeted for infection or the cell type that produces virus, impact fitness. CD4-expressing cells of lymphocyte or macrophage lineage are the principal host cells for HIV-1, although the milieu in lymphocytes is distinct from the macrophage environment from the perspective of cell half-life and activation, signal transduction and expression of coreceptors, and bioavailability of antiretroviral drugs. Multiple viral determinants, including entry via envelope glycoproteins, replication by reverse transcriptase, and virion maturation by protease activity, contribute to fitness in different cells and provide targets for current antiretroviral therapies. This review focuses on fitness of HIV-1 in macrophages and examines the impact of protease inhibitors on fitness of quasispecies and an unexplained discordance between fitness and pathogenesis.

Phase I/II trial of intravenous recombinant interleukin-2 in HIV-infected children

OBJECTIVES

To define the tolerated dose of recombinant interleukin-2 (rIL-2) in HIV-infected children (part A), and to determine the safety and immunologic effects of the tolerated rIL-2 dose in a cohort of HIV-infected children (part B).

DESIGN

Open-label, dose-escalation.

SETTING

Multiple center study.

SUBJECTS

Twenty HIV-infected children, aged 3-12 years.

INTERVENTION

In part A six subjects received 1 x 10(6) IU/m2 and four subjects received 4 x 10(6) IU/m2 rIL-2 by continuous intravenous infusion for 5 days every 8 weeks for three cycles. In part B 10 different subjects received 1 x 10(6) IU/m2 for 5 days every 8 weeks for six cycles.

MAIN OUTCOME MEASURES

Toxicity, CD4 cell count and percentage, and viral load.

RESULTS

The tolerated dose of rIL-2 was 1 x 10(6) IU/m2. The most common side effects were fever and vomiting. Of 10 subjects enrolled in part B of the study, five discontinued rIL-2 therapy for a variety of reasons, most related to administration of study drug. Comparable rises in CD4 cell count and percentage were observed in each of the treatment arms. Six cycles of rIL-2 therapy did not appear to be better than three cycles with respect to improvement of CD4 parameters. Transient rises in plasma HIV-1 RNA levels were detected in some subjects.

CONCLUSIONS

These results suggest that rIL-2 therapy can raise CD4 cell counts and percentages in some HIV-infected children, although a high proportion of HIV-infected children may have to discontinue intravenous therapy because of drug- or administration-related toxicity. Controlled trials of rIL-2 in this patient population are warranted.

Recovery of T-cell subsets after antiretroviral therapy in HIV-infected children

BACKGROUND

Variation of percentageCD4+ T cells may accurately reflects the kinetics of a comprehensive immune recovery independently of the antiretroviral (ART) regimen. To test this we have investigated the relationship among peripheral blood T-cell subsets with the variation of percentageCD4+ T cells during follow up in 49 HIV-infected children.

METHODS

Children were divided into two groups according to the sign of slope percentageCD4+ T cell during follow up: Ps-group (positive slope) and Ns-group (negative percentageCD4 slope) indicative of immunological recovery or not, respectively. CD4+ and CD8+ T-cell subset percentages were examined by three-colour flow cytometry.

RESULTS

We found higher memory CD4+ and CD8+ T-cell percentages in the Ns-group than in the Ps-group, and inversely, higher naive CD4+ and CD8+ T cells in the Ps-group than in the Ns-group. CD4+ and CD8+ subsets in the Ps-group expressed higher levels of CD38+ and lower levels of HLA-DR+ compared with the Ns-group. We found a very strong positive correlation among the slope of percentageCD4+, CD4+ CD38+, whereas a negative correlation among the slope of percentageCD4+, the CD8+ CD28+ CD57+ and CD8+ CD57+ T-cell subsets.

CONCLUSION

Recovery of the CD4+ T-cell percentage induced by ART reflects a reduction in the chronic immune activation and a measurable reconstitution of the immune system and depends on naive CD4+ T cells.

[Complete immune and clinical recovery after highly active antiretroviral therapy in advanced vertically HIV-1 infected children]

BACKGROUND AND OBJECTIVE

The aim of this study was to evaluate the ability of long-term highly active antiretroviral therapy (HAART) to fully reconstitute the immune system in children with severe AIDS.

PATIENT AND METHOD

Lymphoproliferative responses (LPR) were evaluated by incorporation of [3H]-thymidine. Cytokine production in culture (IFN- gamma, IL-5) was quantified using commercially available specific ELISA assays. T-cells subsets were determined by 3-color flow cytometry and thymic production of T-cells was assessed by quantification of TCR rearrangement excision circles (TRECs).

RESULTS

We present a vertically HIV-1-infected child at clinical category C, with long-standing CD4+ T-cells below 50/l, who was monitored during 3-years after starting HAART by quantifying the viral load (VL), naïve, memory, and activated T-cell subsets, and thymical function as well as clinical events. VL was suppressed to undetectable levels since the beginning of HAART with d4T, 3TC, nelfinavir, and efavirenz resulting in a dramatic immune reconstitution, achieving normal CD4+ T-cells counts after 6 months (25%, 597 CD4+ T-cells/l) and perdurable undetectable VL levels. Naïve CD4 and CD8 T-cells increased in parallel to TCR rearrangement excision circles (TRECs) levels, with a concomitant decrease in T-cell activation markers. Interestingly, the patient showed an increase in the lymphoproliferative responses to PHA; the IFN-gamma production by PBMCs increased with HAART while the production of IL-5 diminished, thus indicating a switch of type 2 to type 1 response. He recovered clinically and immunologically (up to normal levels) and remains asymptomatic at present.

CONCLUSION

This report demonstrates that at least in these children, an immune and clinical recovery from an advanced stage of HIV-disease can be possible throught HAART.

The role of protease inhibitor therapy in children with HIV infection

In comparison with HIV infection in adults, higher HIV RNA levels in children with perinatal HIV infection, differences in the natural history of HIV disease progression, and the presence of a relatively immature immune system contribute to the more complex and problematic nature of pediatric antiretroviral therapy. Current US treatment guidelines for pediatric HIV infection advocate aggressive therapy with potent combination antiretroviral regimens, to achieve profound and durable suppression of viral replication and preservation of immune function. The combination of a protease inhibitor (PI) and dual nucleoside reverse transcriptase inhibitors (NRTIs) is the most commonly recommended form of highly active antiretroviral treatment (HAART). However, use of PI therapy in pediatrics has been constrained by the lack of suitable drug formulations, a paucity of pharmacokinetic and safety data, and drug intolerance. Pharmacokinetic studies of PIs demonstrate frequent differences between children and adults, and greater variability among children, which has led to subtherapeutic dosage regimens and the development of viral resistance. The optimal dosage of many PIs in younger children is not yet known. A therapeutically important drug interaction associated with PIs is that occurring between the various PIs themselves, which allows lower doses of PI at less frequent intervals. Dual PI regimens will probably become more common, as they permit a simpler antiretroviral regimen, lower pill/medication burden, fewer adverse effects and improved adherence. Poor adherence to antiretroviral therapy remains the greatest barrier to overall success in the treatment of HIV-infected children. The key to improving adherence in HIV-infected children is to find treatment regimens that are better suited to their normal life. With improvements in existing PIs and the development of newer ones, simplification of current antiretroviral therapy to once-daily regimens without loss of potency should be achievable. PI-containing HAART has transformed HIV infection into a chronic illness, and HIV-infected children now live longer.

Age-related immune reconstitution during highly active antiretroviral therapy in human immunodeficiency virus type 1-infected children

OBJECTIVES

To evaluate the immune reconstitution in HIV-1-infected children in whom highly active antiretroviral therapy (HAART) controlled viral replication and to assess the existence of a relation between the magnitude of this restoration and age.

METHODS

All HIV-1-infected children in whom a new HAART decreased plasma viral load below 400 copies/ml after 3 months of therapy were prospectively enrolled in a study of their immune reconstitution. Viral load, lymphocyte phenotyping, determination of CD4+ and CD8+ T cell receptor repertoires and proliferative responses to mitogens and recall antigens were assessed every 3 months during 1 year.

RESULTS

Nineteen children were evaluated. Naive and memory CD4+ percentages were already significantly increased after 3 months of HAART. In contrast to memory CD4+ percentages, naive CD4+ percentages continued to rise until 12 months. Age at baseline was inversely correlated with the magnitude of the rise in naive CD4+ cells after 3, 6 and 9 months of therapy but not after 12 months. Although memory and activated CD8+ cells were already decreasing after 3 months, abnormalities of the CD8 T cell receptor repertoire and activation of CD8+ cells persisted at 1 year. HAART increased the response to mitogens as early as 3 months after starting therapy.

CONCLUSIONS

In children the recovery of naive CD4+ cells occurs more rapidly if treatment is started at a younger age, but after 1 year of viral replication control, patients of all ages have achieved the same level of restoration. Markers of chronic activation in CD8+ cells persist after 1 year of HAART.

Immune reconstitution

Immune reconstitution in HIV-infected patients remains a potential mechanism to explain delayed disease progression and increased survival following suppressive therapy. Many discrepancies remain to be studied. Is an immune response to HIV protective? Why are anti-HIV CD4 responses lost so quickly in progressors and how can they be restored? What is the damage to the immune system that occurs early in disease and why can it not be overcome by simply controlling viral replication? Will management of immune reconstitution be used in future adjunct treatment strategies (vaccine or STI)? Because HAART is not the answer to long-term management of HIV throughout the world, the recovery of immune function and it's potential to control viral replication remains a key goal in the long-term management of HIV-infected persons.

CD8+ T-cell immunity to HIV infection

Fifteen years after the first, definitive reports of HIV-1-specific, CD8+ T cells [147,148], there is ample evidence for the importance of these cells in control of HIV-1 infection. As much is known of their role in the natural history of HIV-1 infection and their cellular and molecular mechanisms of reactivity than of T-cell responses to any other human virus. Indeed, HIV-1-related research has led the scientific field in revealing many new, fundamental principles of cellular immunity in the last 15 years. From these data, there are multiple, posited mechanisms for loss of CD8+ T-cell control of HIV-1 infection. These include both intrinsic defects in T-cell function and loss of T-cell recognition of HIV-1 because of its extraordinary genetic diversity and disruption of antigen presentation. Efforts have begun on devising approaches to reverse these immune defects in infected individuals and develop vaccines that induce T-cell immunity for protection from infection. Combination antiretroviral drug regimens now provide exceptional, long-lasting control of HIV-1 infection, even though they do not restore anti-HIV-1 T-cell immunity fully in persons with chronic HIV-1 infection. Very encouraging results show that such treatment can maintain normal T-cell reactivity specific for this virus in some persons with early HIV-1 infection. Unfortunately, the antiviral treatment does not cure the host of this persistent, latent virus. This has led to new strategies for immunotherapeutic intervention to enhance the level and breadth of the T-cell repertoire specific for the host's residual virus in persons with chronic HIV-1 infection. Although the principles of immunotherapy stem from early in the last century, modern era approaches are integrating highly sophisticated, molecular and cell biology reagents and methods for control of HIV-1 infection. The most promising immunotherapies are autologous virus activated in vivo by STI or administered in autologous DC that have been engineered ex vivo. There are also compelling rationales supported by animal models and early clinical trials for use of cytokines and chemokines as recombinant proteins or DNA to augment anti-HIV-1 T-cell reactivity and trafficking of T cells and APC to tissue sites of infection. For prevention of HIV-1 infection, the discouragingly poor results of vaccine development in the late 1980s and early 1990s have led to very encouraging, recent studies in monkeys that show partially protective and possibly sterilizing immunity. Finally, clinical trials of new-generation DNA and live vector vaccines already have indications of improved induction of HIV-1-specific T-cell responses. Knowledge of HIV-1-specific T-cell immunity and its role in protection from HIV-1 infection and disease must continue to expand until the goal of complete control of HIV-1 infection is accomplished.