ABSTRACT. Objective. Cryptococcus neoformans is an important cause of central nervous system infection in adults with acquired immunodeficiency syndrome (AIDS) but an unusual cause of disease in children with AIDS. The basis for this age-related difference in incidence is not known but may be caused by differences in exposure or immune response. The objective of this study was to determine whether the low prevalence of cryptococcal disease among children is related to a lack of exposure to C neoformans.Methods. Sera were obtained from 185 immunocompetent individuals ranging in age from 1 week to 21 years who were being evaluated in an urban emergency department. Sera were analyzed for antibodies to C neoformans and Candida albicans proteins by immunoblotting. Immunoblot patterns were compared with those obtained from sera of patients with cryptococcosis (n ‫؍‬ 10) and workers in a laboratory devoted to the study of C neoformans. The specificity of our results was confirmed by several approaches, including antibody absorption and blocking studies. Sera were also analyzed for the presence of cryptococcal polysaccharide by both enzyme-linked immunosorbent assay and latex agglutination assays.Results. Sera from children 1.1 to 2 years old demonstrated minimal reactivity to C neoformans proteins. In contrast, the majority of sera from children >2 years old recognized many (>6) C neoformans proteins. For children between 2.1 and 5 years old, 56% of sera (n ‫؍‬ 25) reacted with many proteins, whereas for children >5 years old (n ‫؍‬ 120), 70% of samples reacted with many proteins. Reactivity was decreased by absorbing sera with C neoformans extracts or by preincubating blots with sera from experimentally infected but not from control rats. Reactivity to C neoformans proteins did not correlate with reactivity to C albicans proteins, which was common in sera from children between the ages of 1.1 and 2 years. Cryptococcal polysaccharide was detected at a titer of 1:16 (ϳ10 ng/mL) in the sera of 1 child, a 5.6-year-old boy who presented to the emergency department with vomiting.Conclusions. Our findings provide both indirect and direct evidence of C neoformans infection in immunocompetent children. Our results indicate that C neoformans infects a majority of children living in the Bronx after 2 years old. These results are consistent with several observations: the ubiquitous nature of C neoformans in the environment, including its association with pigeon excreta; the large number of pigeons in urban areas; and the increased likelihood of environmental exposure for children once they have learned to walk. The signs and symptoms associated with C neoformans infection in immunocompetent children remained to be determined. Primary pulmonary cryptococcosis may be asymptomatic or produce symptoms confused with viral infections and, therefore, not recognized as a fungal infection. Our results suggest that the low incidence of symptomatic cryptococcal disease in children with AIDS is not a result of lack of exposure to C neoforman...

Background In utero transmission of HIV-1 occurs on average in only 3%–15% of HIV-1-exposed neonates born to mothers not on antiretroviral drug therapy. Thus, despite potential exposure, the majority of infants remain uninfected. Weak HIV-1-specific T-cell responses have been detected in children exposed to HIV-1, and potentially contribute to protection against infection. We, and others, have recently shown that the removal of CD4+CD25+ T-regulatory (Treg) cells can reveal strong HIV-1 specific T-cell responses in some HIV-1 infected adults. Here, we hypothesized that Treg cells could suppress HIV-1-specific immune responses in young children.Methodology/Principal FindingsWe studied two cohorts of children. The first group included HIV-1-exposed-uninfected (EU) as well as unexposed (UNEX) neonates. The second group comprised HIV-1-infected and HIV-1-EU children. We quantified the frequency of Treg cells, T-cell activation, and cell-mediated immune responses. We detected high levels of CD4+CD25+CD127− Treg cells and low levels of CD4+ and CD8+ T cell activation in the cord blood of the EU neonates. We observed HIV-1-specific T cell immune responses in all of the children exposed to the virus. These T-cell responses were not seen in the cord blood of control HIV-1 unexposed neonates. Moreover, the depletion of CD4+CD25+ Treg cells from the cord blood of EU newborns strikingly augmented both CD4+ and CD8+ HIV-1-specific immune responses.Conclusions/SignificanceThis study provides new evidence that EU infants can mount strong HIV-1-specific T cell responses, and that in utero CD4+CD25+ T-regulatory cells may be contributing to the lack of vertical transmission by reducing T cell activation.

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

We compiled the clinical and immunologic features of Cryptococcus neoformans infections in human immunodeficiency virus (HIV) -infected children from 1985 to 1996 in a retrospective case series. Thirty cases of cryptococcosis were identified. These children had a median age of 9.8 years, a median CD4 / cell count of 54/mL at the time of diagnosis, and either a culture positive for C. neoformans or cryptococcal antigen in serum or cerebrospinal fluid. Sixty-three percent of the cases occurred in children vertically infected with HIV and in children between 6 and 12 years of age. The clinical and laboratory characteristics of this pediatric cohort were similar to those of adults with AIDS and cryptococcosis. On the basis of a subset of the cases, a 10-year point prevalence of cryptococcosis among children with AIDS of Ç1% was estimated.

Human immunodeficiency virus (HIV)-infected persons manifest decreased antibody responses to pneumococcal polysaccharide vaccines. Since human antibody responses to polysaccharides are often restricted, the molecular structure of antibodies elicited by a 23-valent pneumococcal vaccine was analyzed. Anti-idiotypic reagents were used to detect V(H)1, V(H)3, and V(H)4 gene usage by antibodies to pneumococcal capsular polysaccharides in HIV-uninfected and HIV-infected subjects by ELISA. HIV-uninfected persons generated beta-mercaptoethanol-sensitive and -resistant antibodies to pneumococcal capsular polysaccharides expressing V(H)3 determinants recognized by the D12, 16.84, and B6 monoclonal antibodies; antibodies expressing V(H)1 determinants were not detected, and V(H)4 determinants were expressed by beta-mercaptoethanol-sensitive antibodies only; and HIV-infected subjects had significantly lower capsular polysaccharide-specific and V(H)3-positive antibody responses. These findings confirm decreased antibody responses to pneumococcal vaccination in HIV-infected persons and suggest that their poor responses may result from HIV-associated depletion of restricted B cell subsets.