Impaired Immune Response in Severe Human Lower Tract Respiratory Infection by Respiratory Syncytial Virus

Pediatr Infect Dis J. 2009 Oct;28(10):867-73. doi: 10.1097/INF.0b013e3181a3ea71.


Background: Respiratory syncytial virus (RSV) is a major cause of acute lower respiratory infection in infants. The immune response plays a leading role in the severity of the disease. We hypothesized that severe RSV disease is associated with an impaired immune response characterized by low circulating T lymphocytes and plasma cytokine concentrations.

Methods: We evaluate the in vivo immune responses of previously healthy infants with their first proven RSV-acute lower respiratory infection that required hospitalization. According to the clinical severity, defined by using a strict scoring system, the in vivo immune response was compared through the analysis of plasma cytokine values and the phenotyping of peripheral blood lymphocyte and natural killer (NK) cells.

Results: Absolute blood cell counts of CD4+, CD8+, and CD19+ lymphocytes and NK cells were lower in subjects with RSV than in control infants. Lowest cell counts were observed in more severe RSV-infected infants. Significant low values were obtained in CD8+ lymphocytes (P = 0.03) and nonactive NK cells, that express CD94 antigen (P = 0.046). In contrast, activated NK cells that do not express CD94 molecules were significantly higher in RSV infected infants than in healthy controls (% of cells: P = 0.004). The interferon-gamma and tumor necrosis factor-alpha values in RSV infected patients were lower than in controls subjects. Interleukin-17 cytokine was not detected in healthy infants and the largest concentration was found in moderately ill patients as compared with severe cases (P = 0.033). RSV infection showed significantly higher interleukin-8 chemokine than in control infants (P = 0.024).

Conclusion: We propose that severe RSV infection in very young infants is associated with poor blood proinflammatory cytokine production, low counts of CD8+ T cells and with a greater activity of a group of NK cells, that are independent of the major histocompatibility complex class Ib recognition system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, CD / analysis
  • Cytokines / blood*
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Killer Cells, Natural / immunology*
  • Male
  • Respiratory Syncytial Virus Infections / immunology*
  • Respiratory Syncytial Virus, Human / immunology*
  • Respiratory Syncytial Virus, Human / isolation & purification
  • Respiratory Tract Infections / immunology*
  • Respiratory Tract Infections / virology*
  • Severity of Illness Index
  • T-Lymphocyte Subsets / immunology*


  • Antigens, CD
  • Cytokines