Secondary Streptococcus pnuemoniae infection impairs the immunity to influenza virus by down-regulating virus specific IgG response
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1
The University of Hong Kong, Department of Paediatrics and Adolescent Medicine, Hong Kong, SAR China
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2
The University of Hong Kong, Department of Microbiology, Hong Kong, SAR China
Background: During pandemic and seasonal influenza, secondary bacterial infection often enhances mortality. Given the clinical importance of the co-infection and the increasing risk of influenza outbreak, it is important to understand how the immune system would be affected in dealing with the dual infection.
Methods: Mice were sequentially infected with influenza virus and Streptococcus pneumoniae. Survival and weight lost were recorded. The lung from infected mice were examined for virus titre, bacterial cell counts and inflammatory cytokines production. The lung, spleen and lymph node from infected mice were examined for cellular immune response against the pathogens.
Results: Co-infected mice lost their body weight significantly and resulted in 100% mortality, whereas mice infected with either influenza virus or pneumococcus alone lost their body weight transiently and all recovered from the infection. Co-infected mice had significantly higher virus titre, bacterial cell counts and inflammatory cytokines in their lung when compared to the mice infected with either of the pathogens alone. When compared to single influenza virus infection, secondary pneumococcal infection significantly accelerated disease kinetic of influenza to cause lymphopenia in the spleen. Co-infection reduced the production of influenza virus specific IgG. The suppression of the IgG response was critical to cause excess mortality as adaptive transfer of immune serum against influenza virus after secondary pneumococcal infection rescued co-infected mice from death.
Conclusion: Secondary pneumococcal infection reduced the IgG response to the initial influenza virus infection, which impaired the control of influenza virus and caused excess mortality. This study contributes to the understanding of the pathogenesis of the co-infection.
Acknowledgements
This study was supported by the Area of Excellence program on Influenza, the University Grants Committee of the Hong Kong SAR, China; General Research Fund, Research Grants Council of Hong Kong; a Commission Grant from the Research Fund for the Control of Infectious Diseases (RFCID) of the Health, Welfare and Food Bureau of the Hong Kong SAR Government (2009-2014, Lab-11); Edward Sai-Kim Hotung Paediatric Education and Research Fund; Chung Ko Lee and Cheung Yuen Kan Education and Research Fund
Keywords:
Influenza Virus,
Streptococcus pneumoniae,
Co-infection,
IgG,
Immunity, Cellular
Conference:
15th International Congress of Immunology (ICI), Milan, Italy, 22 Aug - 27 Aug, 2013.
Presentation Type:
Abstract
Topic:
Immune-mediated disease pathogenesis
Citation:
Wu
Y,
Tu
W,
Lam
K,
Chow
K,
Ho
P and
Lau
Y
(2013). Secondary Streptococcus pnuemoniae infection impairs the immunity to influenza virus by down-regulating virus specific IgG response.
Front. Immunol.
Conference Abstract:
15th International Congress of Immunology (ICI).
doi: 10.3389/conf.fimmu.2013.02.00996
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Received:
28 Jun 2013;
Published Online:
22 Aug 2013.
*
Correspondence:
Dr. Wenwei Tu, The University of Hong Kong, Department of Paediatrics and Adolescent Medicine, Hong Kong, Hong Kong, SAR China, wwtu@hku.hk
Prof. Yu-Lung Lau, The University of Hong Kong, Department of Paediatrics and Adolescent Medicine, Hong Kong, Hong Kong, SAR China, lauylung@hku.hk