Abstract
The world’s first natural avian-origin H6N1 influenza A virus infection case in dogs was confirmed in Taiwan in 2014. The H6N1 virus in chickens has been endemic in Taiwan since 1972. Whether the dog H6N1 virus has interspecies transmission potential is the key issue we aim to understand. Following one virus passage in embryonated eggs and two further passages in MDCK cells, we obtained two virus derivatives, E01EE (PB1 739E and PB2 627E) and E01GK (PB1 739G and PB2 627K), respectively. The pathogenicity of E01EE and E01GK was investigated using plaque assay, growth dynamic analysis and cell viability quantification in cells from different animal species. The impact of amino acid mutation on PB1 739 and PB2 627 on viral ribonucleoprotein (RNP) activity was also analyzed. Further mouse infection experiments were performed. The results showed that both E01EE and E01GK decreased cell relative viability of canine MDCK cells, human A549 cells and chicken DF1 cells. E01Gk caused greater cellular harm in MDCK and A549 cells and had significantly higher virus titers in all of the cells compared to E01EE. The PB2 627K but not PB1 739G was the critical mutation that influenced the viral RNP activity. Both E01EE and E01GK caused mice pneumonia and considerable virus shedding, especially E01GK. This report verifies PB2 E627K mutation in virulence and spotlights the potential for the dog H6N1 virus to extend interspecies transmission.
Highlights
The influenza A virus has a wide host range and causes varied disease symptoms, making it an important zoonotic pathogen in the world [1]
E01EE was multiplied through two Madin–Darby canine kidney (MDCK) cell passages and its PB1 739 altered to G (Glycine) and PB2 627 turned back to K; this virus was termed as E01GK
E01GK were acquired after three times of plaque purifications (Table 1)
Summary
The influenza A virus has a wide host range and causes varied disease symptoms, making it an important zoonotic pathogen in the world [1]. In 2007 avian-origin H3N2 canine influenza A virus was discovered and confirmed in South. Both H3N8 and H3N2 subtypes were able to cause sustained transmission among dogs [4,5]. Sporadic influenza infections in dogs were successively reported in Asia, such as H3N2, H3N1, H5N2 and H5N1 in China, South Korea and Thailand [6,7,8,9,10,11,12]. The world’s first H6N1 human infection and dog natural infection cases happened in Taiwan in 2013 [14] and 2014 [15], respectively. The human H6N1 virus (A/Taiwan/2/2013) and the dog H6N1 virus (A/canine/Taiwan/E01/2014) were demonstrated to originate from avian sources [15], which have attracted attention to their interspecies transmission
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