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Introduction: Current advances in neonatology have improved survival among preterm and low-birth-weight infants. However, the risk of neonatal death in preterm infants is much greater than in full-term neonates and is frequently associated with infections., Methods: Little is known about the immune status of preterm neonates; therefore, we analyzed the frequency and absolute counts of different immune populations in 211 cord blood samples taken from very-preterm to full-term neonates., Results: We found that absolute counts of all the immune subsets analyzed (i.e., monocytes, granulocytes, B cells, natural killer (NK) cells, CD4(+), and CD8(+) T cells) were markedly lower in preterm infants than in full-term infants. Surprisingly, we observed that regulatory T cells (Tregs) were the only cell subset that did not decrease in preterm infants, and their frequency was even higher than in full-term infants., Discussion: Tregs are crucial to maternal-fetal tolerance, but their suppressive role could be also implicated in the leukopenia observed in preterm infants. We did not observe differences in thymic function, but we found that plasma levels of interleukin (IL)-7 and the frequency of its receptor were significantly decreased in preterm infants. Our results could help to identify leukopenia and to implement immune therapies that significantly diminish mortality in preterm neonates.

Our objective was to study the probability of achieving undetectable viral load levels in HIV-1-infected children after 36 mo of highly active antiretroviral therapy (HAART). A prospective, multicenter, longitudinal study in 41 HIV-1-infected children on HAART was undertaken. Viral load was quantified using standard molecular assay. CD4+ and CD8+ T cell subsets were determined by flow cytometry. The probability of achieving undetectable viral load was determined using Kaplan-Meier curves according to groups by percentage CD8+ at baseline (CD8+ <25% or >25%). Lower baseline CD8+ T cell levels conditioned a less effective virological response to HAART in children, independent of baseline CD4+ T cell numbers and viral load levels. A greater number of children (81%) from CD8+ >25% group than from the CD8+ <25% (40%) presented undetectable viral load levels (p = 0.013). Additionally, the CD8+ >25% group showed a 4.5-fold higher (95% confidence interval: 1.1-19.2) relative proportion for achieving viral load <400 copies/mL than the CD8+ <25% group (p = 0.039). We concluded that monitoring CD8+ T cell numbers may be valuable in deciding when to start HAART in vertically HIV-1-infected children.

We have investigated the relationship between disease progression and several immunologic and virologic markers of HIV infection. Plasma samples from infants born to HIV-1-infected mothers were collected at birth and at 1, 2, 4, 6, 9, 12, 15, and 18 mo of age and subsequently were assayed every 6 mo for viral load, viral phenotype, and lymphocyte populations. A cutoff level of 25% indicative of a preserved immunologic status, both of CD4+ and CD8+ blood T cells, was associated with significant differences in disease progression (p = 0.04 and 0.02, respectively). Infants with median CD4+ T cells <25% had a relative risk of progression to AIDS 3.35-fold higher than those with CD4+ above this level (p = 0.05). The relative risk of progression to AIDS for infants with median CD8+ <25% was 4.95-fold higher than for those with CD8+ percent above this threshold (p = 0.03). Similarly, a cutoff level of viral load of 5.5 log10 copies/mL was indicative of a worse prognosis. Infants with median viral load >5.5 log10 copies/mL had a relative risk of progression to AIDS 23.72-fold higher (p = 0.0001) than those with median viral load below this threshold. Interestingly, changes from a slow replication and low titer to a rapid replication and high titer of virus and from nonsyncytium-inducing to syncytium-inducing viral phenotype were indicative of progression to AIDS. Our results indicate that biologic phenotype of viral isolates and CD8+ T-lymphocyte percentages in peripheral blood as well as viral load and CD4+ T-lymphocyte percentages could predict rapid progression to advanced HIV-1 disease in HIV-1-infected infants.