Vertical transmission of HIV in New York State: a basis for statewide testing of newborns

Infants (n = 313) of HIV-infected mothers were enrolled (mean age 1.9 weeks, range 0-8 weeks) in a 3-year prospective study of vertical transmission. Fifty-six infants (17.9%) had laboratory and clinical evidence of HIV infection. Polymerase chain reaction (PCR) provided early and reliable identification of infected infants. Thirty-one of the 56 infected infants had specimens submitted when the infants were 4 weeks of age or less and 30 (97%) tested PCR positive. This percentage increased to 100% by 8 weeks of age when 51 of the 56 infected infants had specimens tested for that time period. Immune complex dissociation (ICD) antigen testing was a sensitive method for diagnosis of infection but only in infants older than 1 month. p24 antigen testing, although free of false positives, is less sensitive than either of the other methods. Among surrogate markers of HIV infection, elevation of soluble CD8 levels precedes an increase in immunoglobulin levels or a decline in CD4 T lymphocytes. Vertical transmission is significantly lower in Central and Western New York State than other regions. Transmission is significantly higher in low birthweight babies and in infants whose mothers have CD4 counts < 500. This study provided the basis for establishing a Pediatric HIV PCR Testing Service for the early diagnosis of HIV infection in neonates.     

An ATP-activated channel is involved in mitogenic stimulation of human T lymphocytes

We investigated the effect of pharmacologic modulation of the ATP receptor on intracellular ion changes and proliferative response of human peripheral blood lymphocytes (PBLs) and purified T lymphocytes. Extracellular ATP (ATPe) triggered in these cells an increase in the cytoplasmic Ca2+ concentration ([Ca2+]i) and plasma membrane depolarization. Whereas both Ca2+ release from intracellular stores and influx across the plasma membrane were detected in the whole PBL population, only Ca2+ influx was observed in T cells. In the presence of near physiologic extracellular Na+ concentrations (125 mmol/L), Ca2+ permeability through the ATPe-gated channel was very low, suggesting a higher selectivity for monovalent over divalent cations. The selective P2Z agonist benzoylbenzoic ATP (BzATP) increased [Ca2+]i in the presence but not the absence of extracellular Ca2+ and also caused plasma membrane depolarization. The covalent blocker oxidized ATP (oATP), an inhibitor of P2X and P2Z receptors, prevented Ca2+ influx and plasma membrane depolarization, but had no effect on Ca2+ release from stores. Stimulation with ATPe alone had no significant effects on PBL 3H-thymidine incorporation. On the contrary, ATPe or BzATP had a synergistic effect on DNA synthesis stimulated by selective T-cell mitogens such as phytohemagglutinin, anti-CD3 monoclonal antibody, or allogenic PBLs (mixed lymphocyte cultures). Treatment with oATP inhibited mitogenic stimulation by these receptor-directed agents but not by the combined application of the Ca2+ ionophore ionomycin and phorbol myristate acetate. Interleukin-2 partially relieved inhibition by oATP. These results suggest that human T lymphocytes express a plasma membrane channel gated by ATPe that is involved in mitogenic stimulation.     

The ErbB4 Ligand Neuregulin-4 Protects against Experimental Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) affects up to 10% of premature infants, has a mortality of 30%, and can leave surviving patients with significant morbidity. Neuregulin-4 (NRG4) is an ErbB4-specific ligand that promotes epithelial cell survival. Thus, this pathway could be protective in diseases such as NEC, in which epithelial cell death is a major pathologic feature. We sought to determine whether NRG4-ErbB4 signaling is protective in experimental NEC. NRG4 was used i) in the newborn rat formula feeding/hypoxia model; ii) in a recently developed model in which 14- to 16-day-old mice are injected with dithizone to induce Paneth cell loss, followed by Klebsiella pneumoniae infection to induce intestinal injury; and iii) in bacterially infected IEC-6 cells in vitro. NRG4 reduced NEC incidence and severity in the formula feed/hypoxia rat model. It also reduced Paneth cell ablation–induced NEC and prevented dithizone-induced Paneth cell loss in mice. In vitro, cultured ErbB4^−/− ileal epithelial enteroids had reduced Paneth cell markers and were highly sensitive to inflammatory cytokines. Furthermore, NRG4 blocked, through a Src-dependent pathway, Cronobacter muytjensii–induced IEC-6 cell apoptosis. The potential clinical relevance of these findings was demonstrated by the observation that NRG4 and its receptor ErbB4 are present in human breast milk and developing human intestine, respectively. Thus, NRG4-ErbB4 signaling may be a novel pathway for therapeutic intervention or prevention in NEC.Necrotizing enterocolitis (NEC) is a devastating intestinal disease primarily affecting premature infants. In the United States, NEC afflicts 7% of infants weighing <1500 g.¹ In addition to prematurity, risk factors include hypoxia, bacterial colonization of the intestine, and formula feeding.² The development of NEC seems to be multifactorial, and patients may have any combination of risk factors at the time of presentation. The current disease model is that the immature gut barrier, along with defects in endogenous antimicrobial activity,³ allows bacterial translocation across the epithelium, triggering an inflammatory response that further worsens gut barrier function. Pathogenic bacteria,^{4, 5} inflammatory cytokines such as tumor necrosis factor (TNF),^{6, 7, 8} and Paneth cell dropout³ have all been associated with human NEC and contribute to NEC-like injury in animal models.Available therapy for either prevention or treatment of NEC is limited, and patients currently face a mortality rate of approximately 30%.^{9, 10, 11} Breast-fed infants have a lower risk of NEC than their formula-fed peers,^{12, 13} and a variety of studies have attempted to identify and characterize factors in human milk that confer this protection. Candidate protective molecules to date include immunoglobulins, oligosaccharides, lactoferrin, and soluble growth factors, such as epidermal growth factor (EGF)¹⁴ and heparin-binding EGF-like growth factor (HB-EGF).¹⁵ In rat and mouse models, enteral administration of either EGF^{16, 17} or HB-EGF¹⁸ decreases the incidence and severity of NEC. The primary receptor for both EGF and HB-EGF is EGF receptor (EGFR), the prototypic member of the ErbB receptor tyrosine kinase family. However, HB-EGF also activates ErbB4, a member of the ErbB family whose potential role in the developing gut and NEC is not known.ErbB4 has unique biochemical properties distinguishing it from other ErbB family members. Compared with EGFR, ErbB2, or ErbB3, it recognizes a broader collection of ligands, including the EGF-like growth factors HB-EGF and betacellulin as well as the heregulin/neuregulin molecules.¹⁹ At the same time, the ErbB4 c-terminus contains a distinct and somewhat restricted set of functional docking sites for downstream effectors²⁰ and is thus predicted to elicit divergent cellular effects on activation versus other family members. In fact, we recently demonstrated that neuregulin-4 (NRG4), an ErbB4-specific ligand that does not bind or activate other family members, including EGFR,²¹ specifically promotes survival but not migration or proliferation of mouse colon epithelial cells.²² Thus, ErbB4 is a potentially unique and selective target for therapeutic protection in diseases in which intestinal epithelial cell death is a major pathologic feature.We previously reported that ErbB4 is up-regulated in adult human and murine colon inflammation in vivo²³ and that ErbB4 overexpression protects cultured colonocytes from cytokine-induced apoptosis in a ligand-dependent manner.²⁴ Furthermore, i.p. NRG4 administration reduces the severity of acute murine dextran sulfate sodium colitis.²² Thus, it seems that ErbB4 induction is a natural compensatory response meant to preserve the epithelium rather than part of disease pathology and that ErbB4 activation with exogenous ligand is protective against induced inflammation. However, the role of this signaling pathway in the small intestine, or during development, has not been described. We hypothesized that ErbB4 and its ligands have a protective role in the small bowel during postnatal development, particularly in the setting of NEC-associated acute injury and inflammation. To advance our understanding of ErbB4 biology in intestinal homeostasis and disease, we tested the hypothesis that NRG4-ErbB4 signaling is protective in experimental NEC.     

Graft Copolymers with Complex Polyether Structures: Poly(ethylene oxide)‐graft‐Poly(isobutyl vinyl ether) by Combination of Living Anionic and Photoinduced Cationic Graft Polymerization

A novel polymerization mechanism transformation strategy, involving anionic ring‐opening polymerization and photoinduced cationic polymerization, is successfully applied for the synthesis of poly(ethylene oxide)‐graft‐poly(isobutyl vinyl ether) (PEO‐g‐PIBVE). First, poly(ethylene oxide‐co‐ethoxyl vinyl glycidyl ether) [P(EO‐co‐EVGE)] is synthesized by living anionic polymerization. The vinyl moieties of the functional PEO‐based polymer are converted to the hydrogen iodide adduct by photolysis of diphenyliodonium iodide, monitored using NMR spectroscopy. A modified mode of Lewis acid‐catalyzed living cationic polymerization is performed as a “grafting from” method to generate PIBVE segments grafted onto the PEO main chain. Both the intermediates and the final graft copolymers are characterized by gel‐permeation chromato­graphy (GPC) and ¹H NMR analysis.

     

Novelty exposure overcomes foot shock-induced spatial-memory impairment by processes of synaptic-tagging in rats

Novelty processing can transform short-term into long-term memory. We propose that this memory-reinforcing effect of novelty could be explained by mechanisms outlined in the "synaptic tagging hypothesis." Initial short-term memory is sustained by a transient plasticity change at activated synapses and sets synaptic tags. These tags are later able to capture and process the plasticity-related proteins (PRPs), which are required to transform a short-term synaptic change into a long-term one. Novelty is involved in inducing the synthesis of PRPs [Moncada D, et al. (2011) Proc Natl Acad Sci USA 108:12937-12936], which are then captured by the tagged synapses, consolidating memory. In contrast to novelty, stress can impair learning, memory, and synaptic plasticity. Here, we address questions as to whether novelty-induced PRPs are able to prevent the loss of memory caused by stress and if the latter would not interact with the tag-setting process. We used water-maze (WM) training as a spatial learning paradigm to test our hypothesis. Stress was induced by a strong foot shock (FS; 5 × 1 mA, 2 s) applied 5 min after WM training. Our data show that FS reduced long-term but not short-term memory in the WM paradigm. This negative effect on memory consolidation was time- and training-dependent. Interestingly, novelty exposure prevented the stress-induced memory loss of the spatial task and increased BDNF and Arc expression. This rescuing effect was blocked by anisomycin, suggesting that WM-tagged synapses were not reset by FS and were thus able to capture the novelty-induced PRPs, re-establishing FS-impaired long-term memory.     

Clinical impact of the use of 16S rRNA sequencing method for the identification of "difficult-to-identify" bacteria in immunocompromised hosts

Molecular method of 16S rRNA sequencing is reported to be helpful in the accurate identification of organisms with ambiguous phenotypic profiles. We analyzed the use of 16S rRNA sequencing method to identify clinically significant, “difficult‐to‐identify” bacteria recovered from clinical specimens, and evaluated its role in patient management and consequent clinical outcome. Among the 172 “difficult‐to‐identify” bacteria recovered over a 4‐year period, 140 were gram‐positive cocci or gram‐negative bacilli; identification by 16S rRNA did not play a role in the management of patients infected with these bacteria. From 32 patients, 33 “difficult‐to‐identify” gram‐positive bacilli were identified; the organisms were mycobacteria, Nocardia, Tsukamurella, Rhodococcus, and Gordonia. In 24 patients for whom clinical data were available, results from the 16S rRNA sequencing method led to treatment change in 14 immunocompromised patients (including 7 hematopoietic stem cell recipients and 1 liver transplant recipient). Therapy was modified in 9 patients, initiated in 3 patients, and discontinued in 2 patients. Most patients’ therapy was switched to oral antibiotics with discontinuation of intravascular catheters, facilitating early hospital discharge. All 14 patients were alive 30 days after infection onset. The present study demonstrates the clinical application of 16S rRNA sequencing method to identify “difficult‐to‐identify” mycobacteria and other gram‐positive bacilli in clinical specimens, particularly in immunocompromised hosts.