Pre-exposure to Streptococcus suis improved survival of influenza virus co-infection in mice
Jingjiao Ma1, Mingqing Wu1, Zhaofei Wang1
1Shanghai Key Laboratory of Veterinary Biotechnology, Key Laboratory of Urban Agriculture (South), Ministry of Agriculture, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, 200240, China.
Abstract:
The synergism of the influenza virus and respiratory tract pathogens is known to exacerbate diseases in both humans and animals. The mechanism of the co-infection of associated respiratory tract pathogens is explored in this study. Co-infection has a directional effect when influenza virus or other pathogens occur in a different order. In the present study, we used a mouse animal model to study the synergism of influenza virus and Streptococcus suis co-infection in different orders of administration. We found that the group infected with bacteria alone did not show any clinical symptoms, but the group infected with the virus alone showed 100 % mortality and clinical signs typical in infected mice. In the bacteria infected following virus pre-exposure group, the mice died before the virus-infected group and showed severer clinical signs. When the influenza virus was administered after the bacteria, the infected mice showed reduced mortality compared with mice administered the influenza virus alone. The results indicated that the order of infection significantly affected the outcome of the co-infection of these two pathogens in the mice. However, the underlying mechanism was unclear. Therefore, a transcriptome analysis of mouse lungs was conducted to explore the potential mechanism. The results showed that inflammation and cell damage signaling pathways were upregulated, which may have contributed to the increased mortality in the secondary bacterial infection group. Upregulated innate immunity may have been a major cause of reduced mortality when the bacteria were inoculated before the virus infection.
Insights
The order of influenza virus and Streptococcus suis co-infection significantly impacts disease severity in mice. Secondary bacterial infection after influenza increases mortality, while preceding bacteria reduces it, suggesting distinct immune responses.
Area of Science:
- * Veterinary Medicine
- * Infectious Diseases
- * Immunology
Background:
- * Co-infections involving influenza virus and bacterial pathogens like Streptococcus suis can worsen respiratory diseases in humans and animals.
- * The sequence of pathogen exposure is hypothesized to influence the outcome of such co-infections.
Purpose of the Study:
- * To investigate the impact of administration order on the synergism between influenza virus and Streptococcus suis co-infection in a mouse model.
- * To explore the underlying molecular mechanisms, particularly focusing on host immune responses and lung transcriptome changes.
Main Methods:
- * A mouse model was utilized to study co-infections with influenza virus and Streptococcus suis administered in different sequences.
- * Clinical signs, mortality rates, and lung transcriptome analysis were employed to assess the effects of co-infection order.
Main Results:
- * Influenza virus alone caused 100% mortality, while Streptococcus suis alone showed no clinical symptoms.
- * Sequential infection with bacteria after influenza virus led to increased mortality and more severe clinical signs compared to virus-only infection.
- * Preceding bacterial infection before influenza virus administration resulted in reduced mortality compared to influenza virus alone.
Conclusions:
- * The order of influenza virus and Streptococcus suis co-infection critically determines the disease outcome in mice.
- * Transcriptome analysis suggests that upregulated inflammation and cell damage pathways contribute to increased mortality in secondary bacterial infections.
- * Enhanced innate immunity following initial bacterial exposure may be responsible for the reduced mortality observed when bacteria precede viral infection.
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