| Respiratory syncytial virus (RSV) bronchiolitis had been identified as a risk factor for later recurrent wheezing and childhood asthma, in which an imbalance of CD4 helper T cell (Th) function, favoring a Th2 predominant response, is believed to be very important. The asthma-like symptoms of RSV bronchiolitis and its close relationship to asthma suggest that RSV bronchiolitis and childhood asthma may have the same immunological phenotype. Animal studies have shown that RSV stimulates a Th2 lymphocyte response with the strongest evidence coming from a model of formalin-inactivated RSV (FI-RSV) enhanced disease, in which the selective activation of virus-specific Th2 cells was shown to play an important role in the development of RSV vaccine-enhanced illness. However, the selective differentiation of Th2 cells can be influenced by a variety of factors, including the nature of antigen and genetic background. Experimental infection with live RSV induced Th1-predominant response without exception.Previous studies of the relationship between cytokine response pattern and RSV infection were usually based on the analyses of proteins or mRNA in plasma or culture supernatants. They had great diversity in the methods such as culture conditions, stimulation protocols, study population characteristics, the time of experiment, and produced conflicting results. To our knowledge, there were very few studies involving single-cell based cytokine response patterns, especially Thl/Th2 balance, in human RSVinfection, also with different results. To reveal the relationship between RSV infection and cytokine response patterns on both system and single-cell bases, we determined the cytokine profiles (IL-4 and IFN-γ) of CD3+ and CD8+ lymphocytes by intracellular cytokine staining technique and flow cytometry, combined with serum IL-4, IFN- y and IL-12 determinations. We also explored the relationship between RSV infection and the gene polymorphisms of IL-12p40, one of IL-12 subunits, in both the 3'-untranslated region (UTR) and promoter.Part one Association of cytokine response patterns with the phenotypeof infantile RSV infection Aim:To reveal the relationship between the phenotype of RSV infection in infancy and cytokine response patterns on both system and single-cell bases.Methods:Forty-four infants with RSV lower respiratory infection (26 bronchiolitis and 18 pneumonia, of them 15 were severe) and 41 infants with non-RSV lower respiratory infection, 30 infants as control group were enrolled in the study.1. Direct immunofluorescence technique was utilized to identify RSV antigen in the respiratory epithelium cells.2. The frequencies of IL-4 and IFN- Y expression in the peripheral blood CD3+ and CD8+ T lymphocytes were measured by intracellular cytokine staining technique and four-colour flow cytometry. CD4+ lymphocytes were identified indirectly by CD3+ CD8-cells.3. Serum IL-4, IFN-γ and IL-12 levels were determined by solid-phase sandwich enzyme-linked immunosorbent assay.Results:1.There were no statistical differences in the percentages of blood CD3+, CD3+ CD8-and CD3+ CD8+ lymphocytes among the RSV-infected, non-RSV-infected and control infants. No differences were found either between RSV bronchiolitis and RSV pneumonia groups or between mild and severe RSV infection groups.2. RSV-infected infants showed no significant differences from non-RSV-infected patients and control group in the frequency of IL-4 or IFN- Y expression in CD3+ CD8-lymphocytes. After comparing IL-4 and IFN-γ expression in CD3+ CD8+ lymphocytes, we observed a significant increase in IFN- Y expression in RSV-infected (M=2.70% vs 0.81%) and non-RSV-infected patients (M=3.59% vs 0.81% ) compared to control.3. RSV-infected infants had a slightly elevated serum IL-12 level (M=64.62pg/ml vs 48.23pg/ml) without any statistical difference from that of control, while non-RSV-infected infants (M=152.00pg/ml) showed a statistically much higher level. When compared with the serum IL-4 level of control, both RSV-infec...
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