High Levels of Virus-Specific CD4+ T Cells Predict Severe Pandemic Influenza A Virus Infection
Tim J. Powell2,
Andrew J. McMichael2,
Ling-Pei Ho2,5,‡ and
+ Author Affiliations
1Beijing You’an Hospital, Capital Medical University, Beijing, China
2MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, Oxford University, Oxford, United Kingdom
3Nuffield Department of Anesthesia, The John Radcliffe Hospital, Oxford, United Kingdom
4Chinese National Influenza Center, National Institute for Viral Disease Control and Prevention, China CDC, Beijing, China; and
5Oxford Centre for Respiratory Medicine, Churchill Hospital, Oxford, United Kingdom
Correspondence and requests for reprints should be addressed to Tao Dong, Ph.D., or Ling-Pei Ho, M.D., Ph.D., MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK. E-mail: firstname.lastname@example.org or email@example.com
Rationale: T-cell responses have been implicated in control and exacerbation of lung injury during influenza A virus (IAV) infection.
Objectives: To examine the breadth and magnitude of influenza-specific CD4+ and CD8+ T-cell responses during acute phase of infection.
Methods: Influenza-specific T-cell response to the entire pandemic H1N1/09 IAV proteome and T cell–related cytokine levels were measured in blood from previously healthy individuals with mild (n = 32) and severe (n = 16) IAV infection during the 2009 influenza pandemic. Virus-specific T-cell response in lung and blood was also performed in two acutely infected, severely ill patients using fluorescent-conjugated pdmH1N1/09 Matrix-MHC-I tetrameric complexes.
Measurements and Main Results: Strong and broad CD4+ but not CD8+ T-cell responses were observed in the blood, and were higher in those with severe disease. Antigen-specific CD8+ T cells in the lungs were on average 45-fold higher compared with blood in severely ill patients. Paradoxically, in patients with severe disease, IL-17, IL-2, IL-4, and IFN-γ levels were significantly decreased.
Conclusions: High levels of circulating virus-specific CD4+ T cells to two viral internal proteins (nucleoprotein and matrix) in the first phase of infection are associated with subsequent development of severe IAV infection. This finding could be an early and specific marker for ensuing clinical deterioration. Contrasting levels of antigen-specific CD8+ T cells in lungs and blood have implications on design and analysis of clinical trials for T-cell vaccines because measurements of T cells in the periphery may not reflect events in the lungs.