| Background The common cause of acute respiratory tract inflammation among clinical diseases is the infection of Influenza Virus(Flu) and Respiratory Syncytial Virus(RSV). Both the Flu and the RSV caused diseases have the characters of high morbidity and mortality. The cooperative organizations of WHO have paid highly attention to the surveillance and detection of the pathogens among respiratory diseases, which aim is to prevent spreading through the world. Under this condition, the results reported by the health care organizations from the surveys and statistics showed that, among the causative pathogens of respiratory infection, virus share a significant portion, then among the viruses that can cause severe acute respiratory inflammation are influenza virus and respiratory syncytial virus. For example, the infants and young children age between 1 month and 5 years, the teenagers of 6 to 24 years old, and the adults from 25 to 65 years old, hospital diagnosed influenza like illness (ILI) cases are nearly 45% caused by respiratory viruses, the RSV positive is nearly 50% among the cases of co-infection with 2 or more respiratory viruses, subsequently are type A and type B influenza viruses, which is 9.84% and 10.39% respectively.The potential infectious populations cover all ages. Furthermore, there were no efficient vaccine-supply for all aged in large-scale. The harm to human society or the loss in pandemic or epidemic is immeasurable. In situations mentioned above, there is an urgent need for the research of the dual infection of these two viruses. Methods For research how the immune system response after the success infected with both influenza and RSV, and the reverse the infection order, by creating the dual infectious model with influenza virus(H1N1, A/Puerto Rico/8/34) and respiratory syncytial virus(Respiratory Syncytial Virus, RSV-Long) on BALB/c mice. The infectious order is primary challenged with H1N1 then followed with RSV 3 days later, we also reversed the infectious order as primary challenged with RSV then followed with H1N1 3 days later, both are through intranasal. We studied the Th1, Th2, Th17 and Treg cell ratios among splenic lymphocytes, and the shifting of CD4+ and CD8+ cell ratios by using Flow Cytometry(FCM). To study the polarization of CD4+T cells during inflammation by quantifying the inflammatory cytokines using Bio-plex suspension array technology. Then analyzed the viral load in lung by using quantification RT-PCR(qPCR) and the viral distribution within respiratory tract by immunohistochemistry(IHC). The pathology studies using hematoxylin and eosin(H & E)-stained paraffin embedding pathological sections combined with the observing during the mouse dissecting, which enable to compare the degree of inflammation when dual infection occurred either after shifting the challenge order.Findings The results showed that,1) the pathology studies revealed that the dual infected mouse developed more severe inflammation in compared with single infectious mouse, and the mouse primary challenged with RSV then followed with H1N1 developed the most severity inflammation.2) the FCM results showed that in different stages of dual infection, the CD4+ T cell ratios are different among Th subgroups:at the onset stage, primary challenged with H1N1 then followed RSV is dominant by Th2 response, the Th2 shift to Thl after reversed challenge order. At the middle stage of dual infection, both primary challenged with H1N1 then followed with RSV or reversed get the equal level of Thl and Th2 response, but the mouse primary challenged with RSV then followed with H1N1 trends to bias to Th2 response. At the later stage of dual infection, both challenge orders are dominant by Thl response.Interpretation Dual infected with influenza virus and RSV caused more severity of lung inflammation in compared with single infectious either influenza virus or RSV. The primary challenged with RSV then followed by influenza virus can cause the most tissue damage are observed. |
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