Integration Of Clinical Signs, Pathology And Transcript Analysis In Porcine Lung Dual Infected With Swine Influenza Virus H1N1and Streptococcus Suis Serotype2

Both Swine influenza virus and Streptococcus suis serotype2are important respiratory tract pathogens. In clinic, PRDC caused by the dual infection of SIV (mostly H1N1) and SS2is common and leads to great economic losses in swine industry worldwide. But till now not much is known about the pathogenesis, the host response and the treatment to this dual infection. In this study, we used microarray to describe the gene expression profiles of porcine lungs which suffered from PBS, SIV, SS2, SIV-SS2respectively to improve the understanding of the pathogenesis of SIV-SS2dual infection.1. Effect of experimental dual infection of SIV and SS2on pigletsA total of12piglets of high-health status were randomly divided into4groups with3piglets per group. On day1, piglets in SIV group and SIV-SS2group were inoculated intranasally with SIV while piglets in other two groups were inoculated intranasally with DMEM as control. On day4, piglets in SS2group and SIV-SS2group were inoculated intranasally with SS2while piglets in other two groups were inoculated intranasally with PBS as control. On day6, all piglets were humanely euthanized. The macroscopic lesions were recorded and lungs were taken immediately (for extraction of total RNA, for isolation of virus and bacteria, for histopathology evaluation). During the whole experiment, all piglets were monitored daily for rectal temperature and clinical signs. In this study, we found that the dual infection of SIV and SS2can result in more serious disorder of temperature and clinical signs. In addition, the area and degree of macroscopic lesions and microscopic lesions caused by dual infection were greater than either single infection. Beside, we also found that SS2do favor to SIV replication and make symptom of swine influenza last for longer time.2. Transcript profiling of piglets dual infected with SIV and SS2We extracted total RNA from lungs collected in the above experiment and the RNA labeling, hybridization were carried out later. After microarray data being normalized, one-way analysis of variance (ANOVA) was used for statistic analyzing. The differentially expressed (DE) transcripts were identified by taking a fold change (Fc) greater than1.5and p value lesser than0.05as criteria. In SIV group,1314transcripts were differentially expressed which represented444unique genes. In SS2group, there were1354transcripts that changed expression and represented411unique genes. While in SIV-SS2group, the number of differentially expressed transcripts reached up to2652and represented844unique genes. By MAS3.0software, the DE genes of SIV group, SS2group and SIV-SS2group were mainly clustered into92,105,200categories respectively based on biological process and majority of DE genes were associated with signal transduction, transcription, development, immune response, cell adhesion, inflammatory response, apoptosis, innate immune response. Pathway analysis was also performed and the DE genes of SIV group, SS2group, SIV-SS2group were mainly involved in Cytokine-cytokine receptor interaction, Toll-like receptor signaling pathway, MAPK signaling pathway, Apoptosis, Complement and coagulation cascades, Cell adhesion molecules (CAMs), Natural killer cell mediated cytotoxicity, Hematopoietic cell lineage. By comparing the transcript profiling of those three groups, we presume that the exaggerated cytokine and apoptosis caused by the dual infection of Swine influenza virus H1N1and Streptococcus suis serotype2were at least a part of pathogenesis of this kind of dual infection.