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Abstract: The HA protein of the 2009 pandemic H1N1 viruses (H1N1pdm) is antigenically closely related to the HA of classical North American swine H1N1 influenza viruses (cH1N1). Since 1998, through mutation and reassortment of HA genes from human H3N2 and H1N1 influenza viruses, swine influenza strains are undergoing substantial antigenic drift and shift. In this report we describe the development of a novel monoclonal antibody (S-OIV-3B2) that shows high hemagglutination inhibition (HI) and neutralization titers not only against H1N1pdm, but also against representatives of the α, β, and γ clusters of swine-lineage H1 influenza viruses. Mice that received a single intranasal dose of S-OIV-3B2 were protected against lethal challenge with either H1N1pdm or cH1N1 virus. These studies highlight the potential use of S-OIV-3B2 as effective intranasal prophylactic or therapeutic antiviral treatment for swine-lineage H1 influenza virus infections. [Copyright &y& Elsevier]

In 2012, swine influenza surveillance detected a novel reassorted influenza A virus (IAV) strain containing human-seasonal hemagglutinin (HA) and neuraminidase (NA). Subsequently, these viruses reassorted, maintaining only the human-origin H3, which resulted in a new lineage of viruses that became the most frequently detected H3 clade in US swine (2010.1 HA clade). Here, we assessed the antigenic phenotype, virulence, and transmission characteristics of this virus lineage following its introduction to swine. Relative to 2010.1 viruses from 2012 and 2014, recent 2010.1 contemporary strains from 2015 to 2017 resulted in equivalent macroscopic lung lesions and transmission in pigs. A single mutation at amino acid residue 145 within the previously defined HA antigenic motif was associated with a change of antigenic phenotype, potentially impairing vaccine efficacy. Contemporary 2010.1 viruses circulating in swine since 2012 were significantly different from both pre-2012H3N2 in swine and human-seasonal H3N2 viruses and demonstrated continued evolution within the lineage. • Human-like H3N2 swine 2010.1 viruses evolved antigenically at position 145 in the HA. • Recent 2010.1 viruses with different genome combinations were not more virulent or transmissible compared to the prototype. [ABSTRACT FROM AUTHOR]

H4Nx viruses were reported in swine in Canada and China, but had not been recognized in swine in the USA. In late 2015, an avian-origin H4N6 influenza A virus was isolated from pigs in the United States during a routine diagnostic investigation of clinical respiratory disease in the herd. Serological analysis from additional pigs at the farm and other pigs within the swine production system indicated that the virus did not efficiently transmit from pig-to-pig and the mode of transmission to swine could not be determined. The isolate was characterized at the molecular level and the pathogenesis and transmission was experimentally evaluated in pigs. Although the virus replicated in the lungs of pigs and caused mild pulmonary lesions, there was no evidence of replication in the upper respiratory tract or transmission to indirect contacts, supporting the findings on the farm. [ABSTRACT FROM AUTHOR]