Naturally occurring influenza reassortment in pigs facilitates the emergence of intrahost virus subpopulations with distinct genotypes and replicative fitness

ABSTRACT Pigs are recognized as amplifying hosts for influenza A virus (IAV) reassortant viruses. Understanding the extent of IAV reassortment occurring at the individual pig level in naturally infected pigs and how reassortment impacts virus diversity, persistence, and replicative fitness is essent...

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Main Authors: Chong Li, Victoria Meliopoulos, Aaron Rendahl, Stacey Schultz-Cherry, Montserrat Torremorell
Format: Article
Language:English
Published: American Society for Microbiology 2025-01-01
Series:mBio
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Online Access:https://journals.asm.org/doi/10.1128/mbio.01924-24
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author Chong Li
Victoria Meliopoulos
Aaron Rendahl
Stacey Schultz-Cherry
Montserrat Torremorell
author_facet Chong Li
Victoria Meliopoulos
Aaron Rendahl
Stacey Schultz-Cherry
Montserrat Torremorell
author_sort Chong Li
collection DOAJ
description ABSTRACT Pigs are recognized as amplifying hosts for influenza A virus (IAV) reassortant viruses. Understanding the extent of IAV reassortment occurring at the individual pig level in naturally infected pigs and how reassortment impacts virus diversity, persistence, and replicative fitness is essential for countering IAV threats to humans and animals. Here, 244 IAV plaques were isolated from 24 commercial pigs, resulting in 26 distinct genome segment constellations. About 33% (8/24) of pigs were infected with two or more different genotypes, with two pigs harboring two or more different subtypes. Our results indicate that few pigs in a population harbor significantly more genotypes than other pigs and generate most of the diversity, including the emergence of reassortants. However, detecting distinct genotypes during surveillance was dynamic, with most of the genotypes subsiding over time. All the IAV genotypes could replicate in various swine and human-sourced respiratory epithelial cells, and we observed that distinct reassortant genotypes recovered from a single pig could exhibit different growth abilities, especially in human cells. Overall, we demonstrated that multiple distinct IAV genotypes with distinct antigenic profiles and varying growth abilities on swine and human respiratory tracts can be shed simultaneously from a single pig, which contributes to the dynamic nature of IAV prevalence. The striking magnitude of IAV reassortment at the single pig level revealed in this study highlights the need to strengthen surveillance efforts and plans to eliminate IAV from swine farms because pigs have a high potential to produce diverse and potentially zoonotic influenza reassortant viruses.IMPORTANCEPigs play a crucial role in driving influenza A virus (IAV) diversification and evolution by reassorting the viruses originating from different hosts. Despite IAV reassortment and diversity being well documented in pig populations at different scales (e.g., farm, region, country), limited field research has explored the extent of reassortment happening at the single pig level and how that contributes to the overall genetic and biological variation observed in populations. We provide initial information on levels of reassortment happening at the single pig level in naturally infected pigs, and that particular pigs can shed a plethora of distinct genotypes, with certain genotypes having distinct replicative fitness on swine and human respiratory tracts, which preserves the potential for IAV long-term evolution and facilitates the emergence of zoonotic/pandemic-capable reassortants.
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spelling doaj-art-d475218b5fa34ea2a300c3d65ee83fa72025-01-08T14:00:38ZengAmerican Society for MicrobiologymBio2150-75112025-01-0116110.1128/mbio.01924-24Naturally occurring influenza reassortment in pigs facilitates the emergence of intrahost virus subpopulations with distinct genotypes and replicative fitnessChong Li0Victoria Meliopoulos1Aaron Rendahl2Stacey Schultz-Cherry3Montserrat Torremorell4College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota, USADepartment of Host-Microbe Interactions, St. Jude Children’s Research Hospital, Memphis, Tennessee, USACollege of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota, USADepartment of Host-Microbe Interactions, St. Jude Children’s Research Hospital, Memphis, Tennessee, USACollege of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota, USAABSTRACT Pigs are recognized as amplifying hosts for influenza A virus (IAV) reassortant viruses. Understanding the extent of IAV reassortment occurring at the individual pig level in naturally infected pigs and how reassortment impacts virus diversity, persistence, and replicative fitness is essential for countering IAV threats to humans and animals. Here, 244 IAV plaques were isolated from 24 commercial pigs, resulting in 26 distinct genome segment constellations. About 33% (8/24) of pigs were infected with two or more different genotypes, with two pigs harboring two or more different subtypes. Our results indicate that few pigs in a population harbor significantly more genotypes than other pigs and generate most of the diversity, including the emergence of reassortants. However, detecting distinct genotypes during surveillance was dynamic, with most of the genotypes subsiding over time. All the IAV genotypes could replicate in various swine and human-sourced respiratory epithelial cells, and we observed that distinct reassortant genotypes recovered from a single pig could exhibit different growth abilities, especially in human cells. Overall, we demonstrated that multiple distinct IAV genotypes with distinct antigenic profiles and varying growth abilities on swine and human respiratory tracts can be shed simultaneously from a single pig, which contributes to the dynamic nature of IAV prevalence. The striking magnitude of IAV reassortment at the single pig level revealed in this study highlights the need to strengthen surveillance efforts and plans to eliminate IAV from swine farms because pigs have a high potential to produce diverse and potentially zoonotic influenza reassortant viruses.IMPORTANCEPigs play a crucial role in driving influenza A virus (IAV) diversification and evolution by reassorting the viruses originating from different hosts. Despite IAV reassortment and diversity being well documented in pig populations at different scales (e.g., farm, region, country), limited field research has explored the extent of reassortment happening at the single pig level and how that contributes to the overall genetic and biological variation observed in populations. We provide initial information on levels of reassortment happening at the single pig level in naturally infected pigs, and that particular pigs can shed a plethora of distinct genotypes, with certain genotypes having distinct replicative fitness on swine and human respiratory tracts, which preserves the potential for IAV long-term evolution and facilitates the emergence of zoonotic/pandemic-capable reassortants.https://journals.asm.org/doi/10.1128/mbio.01924-24influenza A virusreassortmentreplicative fitnesspigswine farm
spellingShingle Chong Li
Victoria Meliopoulos
Aaron Rendahl
Stacey Schultz-Cherry
Montserrat Torremorell
Naturally occurring influenza reassortment in pigs facilitates the emergence of intrahost virus subpopulations with distinct genotypes and replicative fitness
mBio
influenza A virus
reassortment
replicative fitness
pig
swine farm
title Naturally occurring influenza reassortment in pigs facilitates the emergence of intrahost virus subpopulations with distinct genotypes and replicative fitness
title_full Naturally occurring influenza reassortment in pigs facilitates the emergence of intrahost virus subpopulations with distinct genotypes and replicative fitness
title_fullStr Naturally occurring influenza reassortment in pigs facilitates the emergence of intrahost virus subpopulations with distinct genotypes and replicative fitness
title_full_unstemmed Naturally occurring influenza reassortment in pigs facilitates the emergence of intrahost virus subpopulations with distinct genotypes and replicative fitness
title_short Naturally occurring influenza reassortment in pigs facilitates the emergence of intrahost virus subpopulations with distinct genotypes and replicative fitness
title_sort naturally occurring influenza reassortment in pigs facilitates the emergence of intrahost virus subpopulations with distinct genotypes and replicative fitness
topic influenza A virus
reassortment
replicative fitness
pig
swine farm
url https://journals.asm.org/doi/10.1128/mbio.01924-24
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