Stimulation of lipopolysaccharide from Pseudomonas aeruginosa following H9N2 IAV infection exacerbates inflammatory responses of alveolar macrophages and decreases virus replication.

H9N2 IAV infection contributed to P. aeruginosa coinfection, causing severe hemorrhagic pneumonia in mink. In this study, the in vitro alveolar macrophage models were developed to investigate the innate immune responses to P. aeruginosa LPS stimulation following H9N2 IAV infection, using MH-S cells. The cytokine levels, apoptosis levels and the viral nucleic acid levels were detected and analyzed. As a result, the levels of IFN-α, IL-1ß, TNF-α, and IL-10 in MH-S cells with P. aeruginosa LPS stimulation following H9N2 IAV infection were significantly higher than those in MH-S cells with single H9N2 IAV infection and single LPS stimulation (P < 0.05), exacerbating inflammatory responses. LPS stimulation aggravated the apoptosis of MH-S cells with H9N2 IAV infection. Interestingly, LPS stimulation influences H9N2 IAV replication and indirectly reduced H9N2 IAV replications in in vitro AMs. It implied that LPS should play an important role in the pathogenesis of H9N2 IAV and P. aeruginosa coinfection.

Klebsiella pneumoniae infection following H9N2 influenza A virus infection contributes to the development of pneumonia in mice.

In this study, whether H9N2 influenza A virus (IAV) infection contributed to secondary Klebsiella pneumoniae infection was investigated. From post-infection onwards, clinical symptoms were monitored, examined and recorded daily for 11 days. As a result, no clinical signs were observed in the mice infected with single H9N2 IAV, implying that H9N2 IAV was less pathogenic to mice. Compared to single K. pneumonia infection, K. pneumoniae infection following H9N2 IAV infection exacerbates lung histopathological lesions and apoptosis, resulting in more severe diseases. Lung index of the mice with H9N2 IAV and K. pneumoniae co-infection was significantly higher than those in the other groups. Bacterial loads in the tissues in H9N2 IAV and K. pneumoniae co-infection group were significantly higher than those in the single K. pneumoniae infection group at 7 dpi. It demonstrated that prior H9N2 IAV infection contributed to K. pneumonia proliferation and delayed bacterial clearance in mice. Secondary K. pneumoniae infection influences seroconversion of anti-H9N2 antibody titers and the cytokine profiles. The findings demonstrated that H9N2 IAV infection facilitated secondary K. pneumonia infection, causing severe the diseases in mice.

Nucleotide sequences of the infectious DNA clones of two mink enteritis virus isolates exhibit the diversity of the terminal palindromic sequences and predicted secondary structures.

In this study, the infectious RF-DNA clones of two mink enteritis viruses, MEV-SD1 and MEV-SD7, were constructed, which generated progeny virions and seemed to contain an almost or completely full-length genome. The genomes of MEV-SD1 and MEV-SD7 were 5162 bp and 5113 bp in length, respectively. The genomic organizations of MEV-SD1 and MEV-SD7 were similar to that of the other carnivore parvoviruses. The 3'-UTR of the virion strand of MEV-SD1 and MEV-SD7 were 311 bp and 313 bp in length, respectively, containing a 208 bp palindromic sequence assuming Y-shaped configurations. Interestingly, the difference of the 3' palindromic sequences between MEV-SD1 and MEV-SD7 resulted in the orientation inversion of the hairpin ears. And the 5'-UTRs of MEV-SD1 and MEV-SD7 were 582 bp and 531 bp, respectively, containing a 198 bp palindromic sequence assuming U-shaped configurations, a triplet mismatch (5'-TAC-3') in the center of the duplex stem and a triplet mismatch (5'-AGA-3') forming a small asymmetric bubble. The findings demonstrated that the genomic termini of the carnivore parvoviruses showed the diversity in length, base composition, and predicted secondary structure.