Viral infections have been associated with cellular immune responses and production of Th-1 cytokines. Respiratory syncytial virus (RSV), however, induces virus-specific IgE, which might be a consequence of a Th-2-like activation. To test this hypothesis we quantified interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) in the supernatant of peripheral blood mononuclear cells cultured for 24 and 48 h in the presence or absence of phytohemaglutinin and pokeweed mitogen and the lymphocyte phenotypes to analyze subsets and their activation markers, from 15 hospitalized infants during an acute lower respiratory infection caused by RSV and 17 healthy control infants from 1 to 15 mo of age. Compared with the control infants, those infected with RSV had an increase in the number of B-cells (p < 0.02) and decreases in both CD8+ T-cells (p < 0.01) and activated CD8+/CD25+ suppressor/ cytotoxic T-cells (p < 0.007). In RSV-infected infants, IFN-gamma production was subtotally suppressed, whereas IL-4 production was decreased to a lesser degree, giving significantly (p < 0.001) increased IL-4/IFN-gamma ratio compared with that in the control infants. These findings suggest a predominant Th-z-like response in RSV-infected infants, which could explain some aspects of the immunopathogenesis of RSV infection and the RSV-specific and nonspecific IgE antibody responses observed.

In this study, we demonstrate that during the acute phase of RSV infection, there is an increase in the level of plasma cortisol that is parallel to the decrease in IL-12 and IFN-gamma production. These findings suggest an association between increased plasma cortisol and a decreased Th1-type response. The increase in plasma cortisol was greater in infants with the more severe symptomatology in association with a lower level of IL-12 and IFN-gamma production. The potential causative role of endogenous cortisol in the imbalance of the Th1/Th2 response observed during severe RSV infection requires additional investigation. Our results suggest that the immunologic changes observed in the more severely ill patients may be partially explained by the increased levels of plasma cortisol. This finding should be taken into consideration when systemic steroids are prescribed to infants infected with the RSV because there is still controversy regarding the efficacy of systemic steroid use in severe bronchiolitis.

We have measured the total and differential cell counts, histamine, leukotriene (LT) B4 and LTC4, immunoglobulins, complement (C3), eosinophil-derived basic proteins, and monocyte complement rosettes in bronchoalveolar lavage (BAL) 6 h after challenge with either antigen or diluent control in seven patients with antigen-induced single early reactions, and seven with dual (early and late phase) reactions. In both groups, the total cell counts in BAL were similar, irrespective of whether they were challenged with antigen or diluent. However, in the late-phase responders (LPR), there were significant increases in lymphocytes, neutrophils, and eosinophils (p less than 0.05), and significant decreases in the percentage of lung mast cells (p less than 0.05). The eosinophil major basic protein and eosinophil-derived neurotoxin increased in four of five subjects with dual responses and in the majority of single early responders (SER). BAL histamine concentrations increased in five of seven patients with dual responses. There were no consistent changes in LTB4 concentrations in either the LPR or the SER between diluent and antigen days, but a small but significant increase in LTC4 was observed in the LPR. Concentrations of IgG, IgA, IgM, IgE, C3, and albumin did not differ significantly. The percentage of monocyte complement rosettes also increased significantly (p less than 0.05) in LPR, but not in SER. These findings support the hypothesis that eosinophils and their products play a role in tissue injury in LPR and that eosinophil infiltration may be associated with macrophage activation.

The negative factor (Nef) of human immunodeficiency virus (HIV) is an accessory protein that is thought to be integral to HIV-associated immune- and neuroimmune pathogenesis. Here, we show that nef-transfected microglia-released Nef+ exosome (exNef) disrupts the apical blood-brain barrier (BBB) and that only nef-transfected microglia release Nef in exosomes. nef-gfp-transduced neurons and astrocytes release exosomes but did not release exNef in the extracellular space. Apical administration of exNef derived from nef-transfected 293T cells reduced transendothelial electrical resistance (TEER) and increased permeability of the BBB. Microglia-derived exNef applied to either the apical/basal BBB significantly reduced expression of the tight junction protein, ZO-1, suggesting a mechanism of exNef-mediated neuropathogenesis. Microglia exposed to exNef release elevated levels of Toll-like receptor-induced cytokines and chemokines IL-12, IL-8, IL-6, RANTES, and IL-17A. Magnetic nanoparticle delivery of Nef peptides containing the Nef myrisolation site across an in vitro BBB ultimately reduced nef-transfected microglia release of Nef exosomes and prevented the loss of BBB integrity and permeability as measured by TEER and dextran-FITC transport studies, respectively. Overall, we show that exNef is released from nef-gfp-transfected microglia; exNef disrupts integrity and permeability, and tight junctions of the BBB, and induces microglial cytokine/chemokine secretion. These exNef-mediated effects were significantly restricted by Nef peptides. Taken together, this study provides preliminary evidence of the role of exNef in HIV neuroimmune pathogenesis and the feasibility of a nanomedicine-based therapeutics targeting exNef to treat HIV-associated neuropathogenesis.