Biology subjects

Webby, R. J.

Publications and source records attributed to Webby, R. J..

4 recordsLinked to original sources

bioRxiv2021

Host diversity and behavior determine patterns of interspecies transmission and geographic diffusion of avian Influenza A subtypes among North American wild reservoir species

Wild birds can carry avian influenza viruses (AIV), including those with pandemic or panzootic potential, long distances. Even though AIV has a broad host range, few studies account for host diversity when estimating AIV spread. We analyzed AIV genomic sequences from North American wild birds, including 303 newly sequenced isolates, to estimate interspecies transmission and geographic diffusion patterns among multiple co-circulating subtypes. Our results show high transition rates within Anseriformes and Charadriiformes, but limited transitions between these orders. Patterns of interspecies transmission were positively associated with breeding habitat range overlap, and negatively associated with host genetic distance. Distance between regions (negative correlation) and summer temperature at origin (positive correlation) were strong predictors of diffusion. Taken together, this study demonstrates that host diversity and ecology can determine evolutionary processes that underlie AIV natural history and spread. Understanding these processes can provide important insights for effective control of AIV.

evolutionary biology↗

bioRxiv2021

Minor variants of swine H1N1 influenza viruses with enhanced polymerase activity and HA stability promote airborne transmission in ferrets

Understanding how animal influenza A viruses (IAVs) acquire airborne transmissibility in humans and ferrets is needed to prepare for and respond to pandemics. Here, we investigated in ferrets the replication and transmission of swine H1N1 isolates P4 and G15, whose majority population had decreased polymerase activity and poor HA stability, respectively. For both isolates, a minor variant was selected and transmitted in ferrets. Polymerase-enhancing variant PA-S321 airborne-transmitted and propagated in one ferret. HA-stabilizing variant HA1-S210 was selected in all G15-inoculated ferrets and was transmitted by contact and airborne routes. With an efficient polymerase and a stable HA, the purified minor variant G15-HA1-S210 had earlier and higher peak titers in inoculated ferrets and was recovered at a higher frequency after airborne transmission than P4 and G15. Overall, HA stabilization played a more prominent role than polymerase enhancement in the replication and transmission of these viruses in ferrets. The results suggest pandemic risk-assessment studies may benefit from deep sequencing to identify minor variants with human-adapted traits. IMPORTANCEDiverse IAVs circulate in animals, yet few acquire the viral traits needed to start a human pandemic. A stabilized HA and mammalian-adapted polymerase have been shown to promote the adaptation of IAVs to humans and ferrets (the gold-standard model for IAV replication, pathogenicity, and transmissibility). Here, we used swine IAV isolates of the gamma lineage a model to investigate the importance of HA stability and polymerase activity in promoting replication and transmission in ferrets. These are emerging viruses that bind to both -2,6- and -2,3-linked receptors. Using isolates containing mixed populations, a stabilized HA was selected within days in inoculated ferrets. An enhanced polymerase was also selected and propagated after airborne transmission to a ferret. Thus, HA stabilization was a stricter requirement, yet both traits promoted transmissibility. Knowing the viral traits needed for pandemic potential, and the relative importance of each, will help identify emerging viruses of greatest concern.

microbiology↗

bioRxiv2021

Tropism, susceptibility, infectivity, and cytokine releases of differentiated human tonsillar epithelial cells by different Influenza viruses

Human tonsil epithelium cells (HTEC) are a heterogeneous group of actively differentiating cells comprising stratified squamous epithelial and reticulated crypt cells with abundant keratin expression. We hypothesized that the tonsils are a primary site for influenza infection and sustained viral replication. Primary HTEC were grown using an air-liquid culture and infected apically with different influenza viruses (IVs) to measure viral growth kinetics. These cultures were highly differentiated, with subpopulations of heterogenous surface stratified squamous cells rich with both cilia and microvilli; these cells contained more 2,6-linked sialic acids, those preferentially bound by human IVs, than 2,3-linked avian like sialic acids. The stratified squamous cells were interrupted by patches of reticular epithelial cells rich in 2,3-linked sialic acids. The HTEC were permissive for influenza A and B virus replication. Following infection, a subset of cells, mostly ciliated cells, underwent apoptosis while others remained intact despite being positive for IV nucleoprotein. H3N2 virus antigen colocalized with non-ciliated cells while H1N1 virus antigen was mostly associated with ciliated cells. Exposure of HTECs to IVs triggers an early proinflammatory response that fluctuates between viruses. The H3N2 IV induces an early response that persists, whereas pH1N1 induces a primarily late response in HTECs. Our results implicated HTEC as a site for IV replication. The HTEC differentiated system provides a valuable in vitro model for studying cellular tropism, infectivity, cytokine responses and the pathogenesis of IVs. IMPORTANCETo develop an effective intervention against influenza, it is important to identify host factors affecting transmission, pathogenesis, and immune response. Tonsils are lymphoepithelial organs characterized by infiltration of B and T lymphocytes into the squamous epithelium of tonsillar crypts, beneath which germinal centers play key roles in antigen processing and immune response. The heterogenicity of HTECs as well as the sialic acid distributions supports the replication of IVs and may play a role in IV adaptation. Furthermore, Tonsillectomy is a surgical procedure in which tonsils are fully removed from the human throat and may contribute to the diverse outcomes among infected individuals.

immunology↗

bioRxiv2021

Time dependent proinflammatory responses shape virus interference during coinfections of influenza A virus and influenza D virus

Both influenza A virus (IAV) and influenza D virus (IDV) are enzootic in pigs. IAV causes approximately 100% morbidity with low mortality, whereas IDV leads to only mild respiratory diseases in pigs. In this study, we performed a series of coinfection experiments in vitro and in vivo to understand how IAV and IDV interact and cause pathogenesis during coinfection. Results showed that IAV inhibited IDV replication when infecting swine tracheal epithelial cells (STEC) with IAV 24- or 48-hours prior to IDV inoculation, and that IDV suppressed IAV replication when IDV preceded IAV inoculation by 48 hours. Virus interference was not identified during simultaneous IAV/IDV infections or with 6 hours between the two viral infections, regardless of their order. The interference pattern at 24- and 48-hours correlated with proinflammatory responses induced by the first infection, which was about 24-hours slower for IDV than IAV. The viruses did not interfere with each other if both infected the cells before proinflammatory responses were induced. Coinfection in pigs further demonstrated that IAV interfered both viral shedding and virus replication of IDV, especially in the upper respiratory tract. Clinically, coinfection of IDV and IAV did not show significant enhancement of disease pathogenesis, compared with the pigs infected with IAV alone. In summary, this study suggests that interference during coinfection of IAV and IDV is primarily due to the proinflammatory response and is therefore dependent on the time between infection, and the order of infection. ImportanceBoth IAV and IDV are enzootic in pigs, and feral pigs have a higher risk for both IAV and IDV exposures than IDV exposure alone. This study suggests that in coinfection with IAV and IDV either virus can interfere with the replication of the other virus by stimulating proinflammatory responses; however, the proinflammatory response was 24 hours slower for IDV than IAV. In vitro there was no interference during simultaneous coinfection, regardless of infection order. Coinfection of IDV and IAV in pigs did not show enhanced pathogenesis, compared with those infected only with IAV. This study can facilitate our understanding of virus epidemiology and pathogenesis associated with IAV and IDV coinfection.

microbiology↗