Prospective 5-year study of peripheral blood CD4, CD8, and CD19/CD20 lymphocytes and serum Igs in children born to HIV-1 women. The P(2)C(2) HIV Study Group

Performance Evaluation of Microscanner Plus, an Automated Image-Based Cell Counter, for Counting CD4+ T Lymphocytes in HIV Patients

Counting CD4+ T lymphocytes using flow cytometry is a standard method for monitoring patients with HIV infections. Simpler and cheaper alternatives to flow cytometry are in high demand because getting access to flow cytometers is difficult or impossible in resource-limited settings. We evaluated the performance of the Microscanner Plus, a simple and automated image-based cell counter, in determining CD4 counts against a flow cytometer. CD4 count results of the Microscanner Plus and flow cytometer were compared using samples from 47 HIV-infected patients and 87 healthy individuals. All CV% for precision and reproducibility tests were less than 10%. The Microscanner Plus's lowest detectable CD4 count was determined to be 15.27 cells/µL of whole blood samples. The correlation coefficient (R) between Microscanner Plus and flow cytometry for CD4 counting in 134 clinical samples was very high, at 0.9906 (p < 0.0001). The automated Microscanner Plus showed acceptable analytical performance for counting CD4+ T lymphocytes and may be particularly useful for monitoring HIV patients in resource-limited settings.

Immune Modulation to Improve Survival of Viral Pneumonia in Mice

Viral pneumonias remain global health threats, as exemplified in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, requiring novel treatment strategies both early and late in the disease process. We have reported that mice treated before or soon after infection with a combination of inhaled Toll-like receptor (TLR) 2/6 and 9 agonists (Pam2-ODN) are broadly protected against microbial pathogens including respiratory viruses, but the mechanisms remain incompletely understood. The objective of this study was to validate strategies for immune modulation in a preclinical model of viral pneumonia and determine their mechanisms. Mice were challenged with the Sendai paramyxovirus in the presence or absence of Pam2-ODN treatment. Virus burden and host immune responses were assessed to elucidate Pam2-ODN mechanisms of action and to identify additional opportunities for therapeutic intervention. Enhanced survival of Sendai virus pneumonia with Pam2-ODN treatment was associated with reductions in lung virus burden and with virus inactivation before internalization. We noted that mortality in sham-treated mice corresponded with CD8+ T-cell lung inflammation on days 11-12 after virus challenge, after the viral burden had declined. Pam2-ODN blocked this injurious inflammation by minimizing virus burden. As an alternative intervention, depleting CD8+ T cells 8 days after viral challenge also decreased mortality. Stimulation of local innate immunity within the lungs by TLR agonists early in disease or suppression of adaptive immunity by systemic CD8+ T-cell depletion late in disease improves outcomes of viral pneumonia in mice. These data reveal opportunities for targeted immunomodulation to protect susceptible human subjects.

Biological Aging and Immune Senescence in Children with Perinatally Acquired HIV

Chronic HIV-infected children suffer from premature aging and aging-related diseases. Viral replication induces an ongoing inflammation process, with the release of pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs), the activation of the immune system, and the production of proinflammatory cytokines. Although combined highly active antiretroviral therapy (ART) has significantly modified the natural course of HIV infection, normalization of T and B cell phenotype is not completely achievable; thus, many HIV-infected children display several phenotypical alterations, including higher percentages of activated cells, that favor an accelerated telomere attrition, and higher percentages of exhausted and senescent cells. All these features ultimately lead to the clinical manifestations related to premature aging and comorbidities typically observed in older general population, including non-AIDS-related malignancies. Therefore, even under effective treatment, the premature aging process of HIV-infected children negatively impacts their quality and length of life. This review examines the available data on the impact of HIV and ART on immune and biological senescence of HIV-infected children.

Immune responses to oral poliovirus vaccine in HIV-exposed uninfected Zimbabwean infants

It remains uncertain whether HIV-exposed uninfected (HEU) infants have impaired responses to oral vaccines. We performed a cross-sectional study of 6-month-old infants recruited at birth to the ZVITAMBO trial in Zimbabwe between 1997–2001, before introduction of prevention of mother-to-child transmission interventions. We measured poliovirus-specific IgA to type 1–3 polio strains by semi-quantitative capture ELISA in cryopreserved serum samples collected from 85 HEU and 101 HIV-unexposed infants at 6 months of age, one month after their last immunisation with trivalent OPV. Almost all infants were breastfed, with the majority in both groups mixed breastfed (70.6% HEU versus 71.3% HIV-unexposed). Median (IQR) vaccine titers for HEU and HIV-unexposed infants were 1592 (618–4896) vs. 1774 (711–5431) for Sabin 1 (P = 0.46); 1895 (810–4398) vs. 2308 (1081–4283) for Sabin 2 (P = 0.52); and 1798 (774–4192) vs. 2260 (996–5723) for Sabin 3 (P = 0.18). There were no significant differences in vaccine titers between HEU and HIV-unexposed infants, suggesting that vertical HIV exposure does not impact oral poliovirus vaccine immunogenicity.

Humoral Immunity in Arsenic-Exposed Children in Rural Bangladesh: Total Immunoglobulins and Vaccine-Specific Antibodies

BACKGROUND

Early-life arsenic exposure has been associated with reduced cell-mediated immunity, but little is known about its effects on humoral immunity.

OBJECTIVE

We evaluated whether prenatal and childhood arsenic exposure was associated with humoral immune function in school-aged children.

METHODS

Children born in a prospective mother–child cohort in rural Bangladesh were immunized with measles, mumps, and rubella (MMR) vaccines at 9 years of age (n=525). Arsenic exposure was assessed in urine (U-As), from mothers during pregnancy and their children at 4.5 and 9 years of age. Total IgG (tIgG), tIgE, tIgA, and MMR-specific IgG concentrations were measured in plasma using immunoassays.

RESULTS

Arsenic exposure was positively associated with child tIgG and tIgE, but not tIgA. The association with tIgG was mainly apparent in boys (p for interaction=0.055), in whom each doubling of maternal U-As was related to an increase in tIgG by 28 mg/dL. The associations of U-As at 9 years with tIgG and tIgE were evident in underweight children (p for interaction <0.032). Childhood arsenic exposure tended to impair mumps-specific vaccine response, although the evaluation was complicated by high preimmunization titers. Postimmunization mumps–specific IgG titers tended to decrease with increasing U-As at 4.5 and 9 years of age [regression coefficient (β)=−0.16; 95% confidence interval (CI): −0.33, 0.01; p=0.064 and β=−0.12; 95% CI: −0.27, −0.029; p=0.113, respectively) in 25% children with the lowest preexisting mumps-specific IgG titers.

CONCLUSIONS

Arsenic exposure increased tIgG and tIgE in plasma, and tended to decrease mumps-specific IgG in children at 9 years of age. https://doi.org/10.1289/EHP318.

Assessing immune aging in HIV-infected patients

Many of the alterations that affect innate and adaptive immune cell compartments in HIV-infected patients are reminiscent of the process of immune aging, characteristic of old age. These alterations define the immunological age of individuals and are likely to participate to the decline of immune competence with HIV disease progression. It is therefore important to characterize these changes, which point toward the accumulation of highly differentiated immunocompetent cells, associated with overall telomere length shortening, as well as understanding their etiology, especially related to the impact of chronic immune activation. Particular attention should be given to the exhaustion of primary immune resources, including haematopoietic progenitors and naïve cells, which holds the key for effective hematopoiesis and immune response induction, respectively. The alteration of these compartments during HIV infection certainly represents the foundation of the immune parallel with aging.

Serum free light chains in patients with HIV infection: their association with markers of disease severity and antiretroviral use

AIM

Serum free light chain measurements are used to follow-up and manage patients with monoclonal gammopathies, and abnormal ratios are associated with risk of progression in certain diseases. B cell dysfunction is well described in HIV and patients are at risk of developing B cell lymphomas. This study investigated whether HIV is associated with abnormal free light chain levels and the impact of antiretroviral treatment (ART) on these.

METHODS

κ And λ free light chain concentrations and ratios, serum albumin and immunoglobulin G (IgG) were measured in 366 HIV positive subjects and correlated with CD4+ counts, viral loads, IgG, albumin and ART use.

RESULTS

66% were women and most were black Africans (66%), 26% were of mixed ethnicity and 8% were Caucasian or of unknown or other race. 89% were on ART. κ Free light chain values ranged from 5.59 to 357.0 mg/L (median 19.6 mg/L) and λ free light chain values ranged from 9.28 to 286 mg/L (median 22.3 mg/L). Both correlated positively with viral load and IgG and negatively with CD4+ counts and albumin concentrations. The ratio only correlated with IgG concentrations. Patients on ART had significantly lower free light chain concentrations, but the ratio was not significantly affected.

CONCLUSIONS

This study demonstrated that free light chain concentrations were significantly correlated with markers of HIV disease severity, suggesting ongoing B cell dysfunction despite ART use. Free light chain ratio was not significantly affected.

Effect of HIV-1 exposure and antiretroviral treatment strategies in HIV-infected children on immunogenicity of vaccines during infancy

INTRODUCTION

We studied the effect of maternal HIV-exposure and timing of antiretroviral treatment (ART) in HIV-infected infants on antibody responses to combined diphtheria-toxoid-tetanus-toxoid-whole cell pertussis and Haemophilus influenzae type b conjugate vaccine (HibCV) and monovalent hepatitis B vaccine (HBV).

METHODS

HIV-uninfected infants born to HIV-infected (HEU) or HIV-uninfected (HUU) mothers were enrolled in parallel with HIV-infected children with CD4⁺ ≥25%, who were randomized to initiate ART immediately upon confirmation of HIV-infection (ART-Immed) or when clinically and/or immunologically indicated (ART-Def). Infants received three doses of diphtheria-toxoid-tetanus-toxoid -wP-HibC/HBV at 7.3, 11.4 and 15.4 weeks of age. Antibody to diphtheria-toxoid, tetanus-toxoid, pertussis toxin, filamentous hemagglutinin (FHA) and hepatitis B surface antigen (HBsAg) were measured by Luminex multiplex-immunoassay and polyribosyl-ribitol phosphate (PRP) antibodies by standard ELISA and bactericidal assay.

RESULTS

Prevaccination antibody geometric mean concentrations (GMCs) were higher in HUU than HEU infants for tetanus-toxoid, but lower for HBsAg, diphtheria-toxoid and FHA. Postvaccination GMCs and proportion with seroprotective antibody levels or sero-conversion rates were similar between HUU and HEU infants for all vaccines. Postvaccination GMCs were higher in HUU for tetanus-toxoid, diphtheria-toxoid, HBsAg and FHA than ART-Immed infants; and for tetanus-toxoid, HBsAg and pertussis-toxoid than ART-Def infants. Nevertheless, there was no difference in proportion of HUU and HIV-infected infants who developed sero-protective vaccine-specific antibody levels postvaccination. The timing of ART initiation generally did not affect immune responses to vaccines between HIV-infected groups.

CONCLUSION

Vaccination with DTwP-HibCV/HBV of HEU and HIV-infected infants initiated on early-ART confers similar immunity compared with HUU children.

Vaccine poliovirus shedding and immune response to oral polio vaccine in HIV-infected and -uninfected Zimbabwean infants

BACKGROUND

With prolonged replication, attenuated polioviruses used in oral polio vaccine (OPV) can mutate into vaccine-derived poliovirus (VDPV) and cause poliomyelitis outbreaks. Individuals with primary humoral immunodeficiencies can become chronically infected with vaccine poliovirus, allowing it to mutate into immunodeficiency-associated VDPV (iVDPV). It is unclear if children perinatally infected with the human immunodeficiency virus (HIV), who have humoral as well as cellular immunodeficiencies, might be sources of iVDPV.

METHODS

We conducted a prospective study collecting stool and blood samples at multiple time points from Zimbabwean infants receiving OPV according to the national schedule. Nucleic acid extracted from stool was analyzed by real-time polymerase chain reaction for OPV serotypes.

RESULTS

We analyzed 825 stool samples: 285 samples from 92 HIV-infected children and 540 from 251 HIV-uninfected children. Poliovirus shedding was similar after 0-2 OPV doses but significantly higher in the HIV-infected versus uninfected children after ≥ 3 OPV doses, particularly within 42 days of an OPV dose, independent of seroconversion status. HIV infection was not associated with prolonged or persistent poliovirus shedding. HIV infection was associated with significantly lower polio seroconversion rates.

CONCLUSIONS

HIV infection is associated with decreased mucosal and humoral immune responses to OPV but not the prolonged viral shedding required to form iVDPV.

Suboptimal immune reconstitution in vertically HIV infected children: a view on how HIV replication and timing of HAART initiation can impact on T and B-cell compartment

Today, HIV-infected children who have access to treatment face a chronic rather than a progressive and fatal disease. As a result, new challenges are emerging in the field. Recent lines of evidence outline several factors that can differently affect the ability of the immune system to fully reconstitute and to mount specific immune responses in children receiving HAART. In this paper, we review the underlying mechanisms of immune reconstitution after HAART initiation among vertically HIV-infected children analyzing the possible causes of suboptimal responses.

Immunologic response to oral polio vaccine in human immunodeficiency virus-infected and uninfected Zimbabwean children

BACKGROUND

Poliovirus eradication is dependent on maintaining adequate community-wide levels of serologic protection. Many African countries with conditions that favor continued wild poliovirus propagation also have a high prevalence of pediatric human immunodeficiency virus (HIV) infection. Data are limited regarding the degree of serologic immunity conferred on HIV-infected children after immunization with oral polio vaccine (OPV).

METHODS

This was a cross-sectional study correlating HIV infection and neutralizing antibodies against poliovirus serotypes 1, 2, and 3 in 95 Zimbabwean children 2 months to 2 years of age, born to HIV-infected mothers, who received OPV according to the national schedule.

RESULTS

HIV-infected children had significantly lower rates of seroconversion to all 3 poliovirus serotypes than HIV-uninfected children (60%, 67%, and 47% vs. 96%, 100%, and 82%, P = 0.001, 0.0003, and 0.015 for serotypes 1, 2, and 3 in HIV-infected and uninfected children, respectively, after ≥3 OPV doses). Among poliovirus seroconverters, HIV-infected children also had significantly lower geometric mean titers against serotypes 1 and 2 than HIV-uninfected children (geometric mean titers: 198 and 317 vs. 1193 and 1056, P = 0.032 and 0.050, for serotypes 1 and 2, respectively, after ≥3 OPV doses). In addition, HIV-infected children had significantly higher levels of total IgG and significantly lower CD4% and mean weight than HIV-uninfected children. Of note, none of the HIV-infected children were receiving antiretroviral therapy, and 71% had a CD4% indicating severe immunodeficiency.

CONCLUSIONS

Pediatric HIV infection is associated with a poor serologic response to OPV, which could pose an obstacle to global polio eradication.

Memory B cell function in HIV-infected children-decreased memory B cells despite ART

B cell dysfunction is a well-studied complication of HIV infection in adults. Data on B cell differentiation in normal and HIV-infected children are lacking. We show the distribution of B cell subsets and immunoglobulin levels in HIV-infected children compared with controls. Furthermore, we observe the long-term B cell reconstitution of vaccine-specific immunity after antiretroviral therapy (ART). Phenotype of B cells (naive, non-switched memory, switched memory) was analyzed in 48 infected children and 62 controls. In nine HIV-infected children, functional reconstitution was quantified by tetanus-specific antibodies and by performing a lymphocyte transformation test (LTT) in a longitudinal approach. Switched memory B cells are significantly reduced in HIV-infected children. Vaccine-specific antibodies and response to LTT increase after initiation of ART. Our data indicate a significant dysfunction in the B cell system, despite effective ART. Partial reconstitution of humoral immunity may have therapeutic implications in a subset of HIV-infected children.

B cells in HIV infection and disease

In recent years, intense research efforts have been dedicated to elucidating the pathogenic mechanisms of HIV-associated disease progression. In addition to the progressive depletion and dysfunction of CD4(+) T cells, HIV infection also leads to extensive defects in the humoral arm of the immune system. The lack of immune control of the virus in almost all infected individuals is a great impediment to the treatment of HIV-associated disease and to the development of a successful HIV vaccine. This Review focuses on advances in our understanding of the mechanisms of B-cell dysfunction in HIV-associated disease and discusses similarities with other diseases that are associated with B-cell dysfunction.

Significantly skewed memory CD8+ T cell subsets in HIV-1 infected infants during the first year of life

HIV-1 infection causes a severe T cell compromise; however, little is known about changes in naive, memory, effector and senescent T cell subsets during the first year of life. T cell subsets were studied over the first year of life in blood from 3 infant cohorts: untreated HIV-infected, HIV-exposed but uninfected, and HIV-unexposed. In HIV-infected infants, the frequency of CCR7(+)CD45RA(+) naive CD8(+) T cells was significantly decreased, while the frequency of CCR7(-)CD45RA(-) effector memory CD8(+) T cells was increased, compared with the control cohorts. A larger population of CD8(+) T cells in HIV-infected infants displayed a phenotype consistent with senescence. Differences in CD4(+) T cell subset frequencies were less pronounced, and no significant differences were observed between exposed and unexposed HIV-uninfected infants. We concluded that the proportion of naive, memory, effector and senescent CD8(+) T cells during the first year of life is significantly altered by HIV-1 infection.

The role of polyclonal intravenous immunoglobulin in treating HIV-infected children with severe bacterial infections: a retrospective cohort study

Background

Mortality among HIV-infected children in developing countries remains high after serious bacterial infections despite the use of antibiotics. Intravenous immunoglobulin (IVIG) has been used as an adjuvant therapy to treat these infections, but little data exists regarding its efficacy, and previous studies have focused on IVIG as a prophylactic agent. We examined the impact of IVIG as an adjuvant therapy in reducing mortality and length of hospital stay in HIV-infected children with serious bacterial infections.

Methods

This retrospective study focused on pediatric admissions at a large urban hospital between 2002 and 2006. Children between the ages of one month and nine years of age with laboratory confirmed HIV-status, serious bacterial infection, no prior exposure to IVIG, and a hospital length of stay of 5 days or more, were eligible for inclusion.

Results

A total of 140 children (median age 1.2 years) met inclusion criteria; lower respiratory tract infection was diagnosed in 94 (67%) of the children, while 74 (53%) had bacterial sepsis. Fifty-four (39%) children were receiving antiretroviral therapy and 39 (28%) were receiving tuberculosis treatment. Overall 73 (52%) were treated with IVIG, with the majority (74%) of children receiving a single dose. Thirteen (9%) died during their hospital admission. In crude analysis IVIG was significantly associated with increased mortality was (Odds Ratio (OR): 5.8; 95% Confidence Interval (CI): 1.2–27.1) and this association was weakened by adjustment for other predictors of mortality (OR 4.3, 95% CI 0.7–27.9, p = 0.123). IVIG use was also associated with longer hospital stays.

Conclusion

Administration of one to three doses of IVIG during the acute phase of illness does not appear to reduce mortality or the length of hospital stays in HIV-infected children with serious bacterial infections. However, the retrospective nature of this study makes confounding by indication difficult to control and further studies regarding the timing, dosing, and method of administration are required. Nonetheless the routine use of IVIG in resource-limited settings should be carefully considered given its high cost.

CD4+/CD8+ T cell ratio for diagnosis of HIV-1 infection in infants: Women and Infants Transmission Study

OBJECTIVE

In this study, we tested the hypothesis that the CD4(+)/CD8(+) T cell ratio could predict HIV infection status in HIV-exposed infants.

METHODS

CD4(+)/CD8(+) T cell ratios were determined from data for live-born singleton infants who had been prospectively enrolled in the Women and Infants Transmission Study. Data for 2208 infants with known HIV infection status (179 HIV-infected and 2029 uninfected infants) were analyzed.

RESULTS

Receiver operating characteristic curves indicated that the CD4(+)/CD8(+) T cell ratio performed better than the proportion of CD4(+) T cells for diagnosis of HIV infection as early as 2 months of age, and this relationship was unaffected by adjustment for maternal race/ethnicity, infant birth weight, gestational age, and gender. At 4 months of age, 90% specificity for HIV diagnosis was associated with 60% sensitivity. For ease of use, graphical estimates based on cubic splines for the time-dependent parameters in a Box-Cox transformation (L), the median (M), and the coefficient of variation (S) were used to create LMS centile curves to show the sensitivity and specificity of CD4(+)/CD8(+) T cell ratios in HIV-infected and uninfected infants until 12 months of age. At 6 months of age, a simplified equation that incorporated sequential CD4(+)/CD8(+) T cell ratios and hematocrit values resulted in improved receiver operating characteristic curves, with 94% positive predictive value and 98% negative predictive value. The positive and negative predictive values remained above 90% in simulated infant populations over a wide range of HIV infection prevalence values.

CONCLUSIONS

In the absence of virological diagnosis, a presumptive diagnosis of HIV infection status can be made on the basis of CD4(+)/CD8(+) T cell ratios in HIV-1-exposed infants after 2 months of age; sensitivity and specificity can be improved at 6 months by using a discriminant analysis equation.

Pathogenic mechanisms of B-lymphocyte dysfunction in HIV disease

HIV disease is associated with abnormalities in all major lymphocyte populations, including B cells. Aberrancies in the B-cell compartment can be divided into 3 broad categories: changes that arise as a result of HIV-induced immune activation, changes that arise as a result of HIV-induced lymphopenia, and changes that arise independently of these 2 parameters. We review recent developments in all 3 categories of abnormalities and highlight how observations made in the early years of the HIV epidemic are better understood today in large part because of the advent of effective antiretroviral therapy. Insight into the mechanisms of B-cell dysfunction in HIV disease has also been achieved as a result of increased knowledge of the B-cell subpopulations as they exist in healthy individuals, compared with their abnormalities in HIV-infected individuals. A better understanding of the pathogenic mechanisms of B-cell abnormalities in HIV disease can potentially lead to new strategies for improving antibody responses against opportunistic pathogens that afflict HIV-infected individuals and against HIV itself, in the context of both HIV infection and an antibody-based HIV vaccine.

Diagnosis of HIV-1 infection in children younger than 18 months in the United States

The objectives of this technical report are to describe methods of diagnosis of HIV-1 infection in children younger than 18 months in the United States and to review important issues that must be considered by clinicians who care for infants and young children born to HIV-1-infected women. Appropriate HIV-1 diagnostic testing for infants and children younger than 18 months differs from that for older children, adolescents, and adults because of passively transferred maternal HIV-1 antibodies, which may be detectable in the child's bloodstream until 18 months of age. Therefore, routine serologic testing of these infants and young children is generally only informative before the age of 18 months if the test result is negative. Virologic assays, including HIV-1 DNA or RNA assays, represent the gold standard for diagnostic testing of infants and children younger than 18 months. With such testing, the diagnosis of HIV-1 infection (as well as the presumptive exclusion of HIV-1 infection) can be established within the first several weeks of life among nonbreastfed infants. Important factors that must be considered when selecting HIV-1 diagnostic assays for pediatric patients and when choosing the timing of such assays include the age of the child, potential timing of infection of the child, whether the infection status of the child's mother is known or unknown, the antiretroviral exposure history of the mother and of the child, and characteristics of the virus. If the mother's HIV-1 serostatus is unknown, rapid HIV-1 antibody testing of the newborn infant to identify HIV-1 exposure is essential so that antiretroviral prophylaxis can be initiated within the first 12 hours of life if test results are positive. For HIV-1-exposed infants (identified by positive maternal test results or positive antibody results for the infant shortly after birth), it has been recommended that diagnostic testing with HIV-1 DNA or RNA assays be performed within the first 14 days of life, at 1 to 2 months of age, and at 3 to 6 months of age. If any of these test results are positive, repeat testing is recommended to confirm the diagnosis of HIV-1 infection. A diagnosis of HIV-1 infection can be made on the basis of 2 positive HIV-1 DNA or RNA assay results. In nonbreastfeeding children younger than 18 months with no positive HIV-1 virologic test results, presumptive exclusion of HIV-1 infection can be based on 2 negative virologic test results (1 obtained at > or = 2 weeks and 1 obtained at > or = 4 weeks of age); 1 negative virologic test result obtained at > or = 8 weeks of age; or 1 negative HIV-1 antibody test result obtained at > or = 6 months of age. Alternatively, presumptive exclusion of HIV-1 infection can be based on 1 positive HIV-1 virologic test with at least 2 subsequent negative virologic test results (at least 1 of which is performed at > or = 8 weeks of age) or negative HIV-1 antibody test results (at least 1 of which is performed at > or = 6 months of age). Definitive exclusion of HIV-1 infection is based on 2 negative virologic test results, 1 obtained at > or = 1 month of age and 1 obtained at > or = 4 months of age, or 2 negative HIV-1 antibody test results from separate specimens obtained at > or = 6 months of age. For both presumptive and definitive exclusion of infection, the child should have no other laboratory (eg, no positive virologic test results) or clinical (eg, no AIDS-defining conditions) evidence of HIV-1 infection. Many clinicians confirm the absence of HIV-1 infection with a negative HIV-1 antibody assay result at 12 to 18 months of age. For breastfeeding infants, a similar testing algorithm can be followed, with timing of testing starting from the date of complete cessation of breastfeeding instead of the date of birth.

CD4/CD8 T-cell ratio predicts HIV infection in infants: the National Heart, Lung, and Blood Institute P2C2 Study

BACKGROUND

In resource-poor regions of the world, HIV virologic testing is not available.

OBJECTIVE

We sought to evaluate the diagnostic usefulness of the CD4/CD8 T-cell ratio in predicting HIV infection in infants.

METHODS

Data from the 3- and 9-month visits for non-breast-fed infants born to HIV-infected mothers enrolled (1990-1994) in the Pediatric Pulmonary and Cardiac Complications of Vertically Transmitted HIV Infection Study (mother-to-child transmission of HIV, 17%) were analyzed. Data from the 3-month visit for infants enrolled (1985-1996) in the Perinatal AIDS Collaborative Transmission Study (mother-to-child transmission of HIV, 18%) were used for validation.

RESULTS

At 3 months of age, data were available on 79 HIV-infected and 409 uninfected non-breast-fed infants in the Pediatric Pulmonary and Cardiac Complications of Vertically Transmitted HIV Infection Study. The area under the curve (AUC) of the receiver operating characteristic curve at 3 months was higher for the CD4/CD8 ratio compared with the CD4(+) T-cell count (AUC, 0.83 and 0.75; P = .03). The mean CD4/CD8 ratio at the 3-month visit was 1.7 for HIV-infected infants and 3.0 for uninfected infants. A CD4/CD8 ratio of 2.4 at 3 months of age was almost 2.5 times more likely to occur in an HIV-infected infant compared with an uninfected infant (test sensitivity, 81%; posttest probability of HIV, 33%). Model performance in the Centers for Disease Control and Prevention Perinatal AIDS Collaborative Transmission Study validation test (224 HIV-infected and 1015 uninfected 3-month-old infants) was equally good (AUC, 0.78 for CD4/CD8 ratio).

CONCLUSION

The CD4/CD8 T-cell ratio is a more sensitive predictor of HIV infection in infants than the CD4(+) T-cell count.

CLINICAL IMPLICATIONS

The CD4/CD8 T-cell ratio can be used with caution to predict HIV infection in children.

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.

Pediatric HIV infection: immune and viral evaluation

Advances in laboratory methods have driven improvements in the management and treatment of HIV infection. The methods to accurately and rapidly diagnose HIV infection in infants and children have been outlined in the previous article. In this review, the laboratory evaluation of infected children is described and methods to monitor progression of disease and response to therapy outlined.

Persistent humoral immune defect in highly active antiretroviral therapy-treated children with HIV-1 infection: loss of specific antibodies against attenuated vaccine strains and natural viral infection

OBJECTIVE

In the pre-highly active antiretroviral therapy era, a loss of specific antibodies was seen. Our objective with this study was to describe the loss of specific antibodies during treatment with highly active antiretroviral therapy.

METHODS

In a prospective, single-center, cohort study of 59 children with HIV-1 infection, we investigated the long-term effect of highly active antiretroviral therapy on the titers and course of specific antibodies against measles, mumps, and rubella vaccine strains compared with wild-type varicella zoster virus, cytomegalovirus, and Epstein-Barr virus.

RESULTS

During highly active antiretroviral therapy, age-adjusted CD4+ T cells and B cells increased, whereas total immunoglobulin levels declined. Although these children were preimmunized before the start of highly active antiretroviral therapy, only 24 (43%) had antibodies against all 3 measles, mumps, and rubella. Antibodies against measles, mumps, and rubella were lost in 14 (40%), 11 (38%), and 5 (11%) children who were seropositive at baseline. We also observed loss of varicella zoster virus immunoglobulin G in 7 (21%) of 34, cytomegalovirus immunoglobulin G in 3 (7%) of 45, but none of 53 Epstein-Barr virus-seropositive children. During highly active antiretroviral therapy, primary vaccination in 3 patients and 15 revaccinations in those with negative serology demonstrated incomplete seroconversion.

CONCLUSIONS

Humoral reactivity in children with HIV-1 infection remains abnormal during highly active antiretroviral therapy. Despite immune reconstitution, antibodies against live-attenuated vaccine and wild-type natural virus strains disappear over time in up to 40% of children with HIV-1 infection.

Virologic, immunologic, and clinical benefits from early combined antiretroviral therapy in infants with perinatal HIV-1 infection

OBJECTIVE

To investigate the impact of early versus deferred combined antiretroviral treatment (ART) in asymptomatic or moderately symptomatic [Centers for Disease Control and Prevention (CDC) category N, A or B] infants with perinatal HIV-1 infection.

METHODS

A multi-centre nationwide case-control study was conducted. Data from 30 infants treated with combined ART with three or more drugs before 6 months of age were compared with data from 103 infants starting ART with three or more drugs after 6 months of age. The median follow-up time was 4.1 years (range, 1.0-6.5 years).

RESULTS

No difference was evident in the first available viral load and CD4 T-lymphocyte percentage between the two groups of children. Early-treated infants showed significantly lower viral loads than infants receiving deferred treatment at all the follow-up periods. A higher proportion of early-treated infants than infants receiving deferred treatment (73.3% versus 30.1%; P < 0.0001) reached an undetectable viral load. Higher CD4 T-lymphocyte percentages were found in early-treated infants at 13-24 (P < 0.0001), 25-36 (P < 0.0001), and 37-48 (P = 0.003) months of age. No early-treated infant versus 20 of 103 (19.4%) infants receiving deferred ART (P = 0.02) showed a CD4 T-lymphocyte percentage of less than 15% at one time point during follow-up. No CDC category A, B or C clinical event occurred in early-treated infants over the follow-up period while 44 of 103 (42.7%) infants receiving deferred treatment presented a decline in the CDC category. Kaplan-Meier analyses revealed significant differences in CDC category A (P = 0.0002), B (P = 0.0003), and C (P = 0.0018) event-free survivals.

CONCLUSION

The data suggest virologic, immunologic, and clinical benefits from early administration of ART.

Biomarkers to assess potential developmental immunotoxicity in children

Clinical tests are readily available for assessing severe loss of immune function in children with diseases such as AIDS or primary immunodeficiency. However tests that could reliably identify subtle immune changes, as might be expected to result from exposure to developmental immunotoxic agents, are not readily available. A number of tests are described which we believe have potential applicability for epidemiological studies involving developmental immunotoxicity. Several of the tests, such as T cell receptor rearrangement excision circles (TRECs) and cytokine measurements, while highly relevant from a biological standpoint, may be precluded from use at the current time, for either technical issues or insufficient validation. Immunophenotyping and measurement of serum immunoglobulin levels, on the other hand, are well validated. Yet they may require extraordinary care in experimental design and technical performance in order to obtain data that would consistently detect subtle changes, as these tests are not generally considered highly sensitive. Quantification of the immune response to childhood vaccine, while up to the present used sparingly, may represent an excellent indicator for developmental immunotoxicity when conducted under appropriate conditions.

Persistently high IgA serum levels are a marker of immunological or virological failure of combined antiretroviral therapy in children with perinatal HIV-1 infection

Non-expensive and low-complexity surrogate markers for monitoring the response to combined antiretroviral therapy (combined-ART) are needed in poor-resource settings where routine assessment of CD4+ T-lymphocyte count and viral load can not be afforded. We longitudinally evaluated Ig serum levels in 234 HIV-1 infected children receiving combined-ART with > or = 3 drugs. Since Ig levels physiologically vary with age, differences at different age periods were evaluated as differences in z-scores calculated using the mean and standard deviation of the normal population for each age period. Data from 17 (7.3%) children with immunological failure and from 54 (23.1%) children with virological failure of combined-ART were compared with data from not-failed children. At baseline children with immunological failure showed higher IgM z-scores (P = 0.042) than children without. After 3-12 months of therapy immunologically failed children displayed higher viral loads (P < 0.0001) and IgA (P = 0.043) z-scores than not-failed children. Similarly, at the same follow-up time, children with virological failure showed lower CD4(+) T-lymphocyte percentages (P = 0.005) and higher IgA z-scores (P < 0.0001) than not-failed children. No difference in IgG or IgM z-scores was evidenced between failed and not-failed children after 3-12 months of therapy. In conclusion, IgA serum level is a cheap and low-complexity marker of immunological or virological failure of combined-ART which might be adopted in poor-resource settings.

Combined antiretroviral therapy reduces hyperimmunoglobulinemia in HIV-1 infected children

OBJECTIVE

To evaluate the effect of combined antiretroviral therapy on serum immunoglobulin (Ig) levels in HIV-1 perinatally infected children.

METHODS

Data from 1250 children recorded by the Italian Register for HIV Infection in Children from 1985 to 2002 were analysed. Since Ig levels physiologically vary with age, differences at different age periods were evaluated as differences in z-scores calculated using means and standard deviations of normal population for each age period. Combined antiretroviral therapy has become widespread in Italy since 1996, thus differences in Ig z-scores between the periods 1985-1995 and 1996-2002 were analysed. Data according to type of therapeutic regimen were also analysed.

RESULTS

Between the two periods 1985-1995 and 1996-2002, significant (P < 0.0001) decreases in IgG (6.29 +/- 4.72 versus 4.44 +/- 4.33), IgM (9.25 +/- 13.32 versus 5.61 +/- 7.93), and IgA (10.25 +/- 15.68 versus 6.48 +/- 11.56) z-scores, together with a parallel significant (P < 0.0001) increase in CD4 T-lymphocyte percentages, were found. These decreases were confirmed regardless of whether the children were receiving intravenous Ig or not. Ig z-scores were significantly higher in children receiving mono-therapy than in those receiving double-combined therapy (IgG, P < 0.0001; IgM, P = 0.003; IgA, P = 0.031) and in the latter children than in those receiving three or more drugs (P < 0.0001 for all z-scores). Ig z-scores correlated inversely with CD4 T-lymphocyte percentages and, directly, with viral loads.

CONCLUSIONS

Our data show that in HIV-1 infected children combined antiretroviral therapy leads to reduction of hyperimmunoglobulinemia which parallels restoration of CD4 T-lymphocyte percentage and viral load decrease, which it turn probably reflects improved B-lymphocyte functions.

Varicella zoster as a manifestation of immune restoration disease in HIV-infected children

BACKGROUND

Exacerbation of opportunistic infections in HIV-infected patients shortly after initiation of highly active antiretroviral therapy (HAART) has been named immune restoration disease (IRD). Thus far, IRD has not been reported in children.

OBJECTIVE

We describe the clinical and immune characteristics of IRD in HIV-infected children treated with HAART.

METHODS

A historical cohort study was conducted in a tertiary HIV center in perinatally HIV-infected children who were started on a first stable HAART between January 1996 and July 2002. The incidence of opportunistic infections, newly AIDS-defining events or death after initiation of HAART, and virologic and immunologic information was evaluated at baseline and every 3 months post-HAART.

RESULTS

Sixty-one perinatally HIV-infected children were started and maintained on HAART for >6 months. Seven episodes of IRD occurred. All were cutaneous herpes zoster (HZ). Children who developed HZ had significantly lower baseline CD4+ and CD8+ T-cell numbers compared with children who did not. HZ occurred only in children (7 of 34 subjects) with virological and immunological success to HAART. In children with a previous history of varicella infection, the risk of developing HZ after HAART was higher in those without a protective level of varicella-specific IgG (50%, or 5 of 10 subjects) compared with those with seroprotection (10%, or 2 of 20).

CONCLUSION

Herpes zoster is a common manifestation of IRD in HIV-infected children after the initiation of HAART. Risks for developing HZ include no protective varicella-specific antibody despite previous varicella infection, severe immunodeficiency at baseline, and vigorous immunologic and virologic responses to HAART.

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

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

Decline of CD3-positive T-cell counts by 6 months of age is associated with rapid disease progression in HIV-1--infected infants

Because HIV-1 infected infants with rapid progression (RP) of disease might benefit from early and intense antiretroviral therapy, the identification of predictive factors of RP becomes extremely important. Currently, the best predictive factors of RP in HIV-1 infected children are HIV-1 RNA levels and CD4-positive T-cell counts. A decrease in CD3-positive T-cell count has been identified as a predictive factor of AIDS development in HIV-1 infected adults. Our objective was to evaluate decreased number of CD3-positive T-cells as a predictive factor of RP in infants. Peripheral blood lymphocytes from HIV-1 infected infants (up to 6 months of age) were analyzed for an association of lymphocyte subsets with RP, which was defined as the occurrence of AIDS or death before 18 months of age. In infants with RP (n = 32), CD3-positive T-cell counts were 3093 cells/microL at <1 month of age, 3092 cells/microL at 1 to 3 months, and 2062 cells/microL at 3 to 6 months. Non-RP infants (n = 49) maintained their CD3-positive T-cells counts at approximately 4000 cells/microL for at least 6 months of life. CD3-positive and CD4-positive T-cell counts were significantly associated with RP. Our results suggest that a decreased CD3-positive T-cell count may be used to predict RP in HIV-1 infected infants (RR = 2.16, P =.001).