Genetic analysis of two influenza A (H1) swine viruses isolated from humans in Thailand and the Philippines

Abstract

Influenza viruses A/Philippines/341/2004 (H1N2) and A/Thailand/271/2005 (H1N1) were isolated from two males, with mild influenza providing evidence of sporadic human infection by contemporary swine influenza. Both viruses were antigenically and genetically distinct from influenza A (H1N1 and H1N2) viruses that have circulated in the human population. Genetic analysis of the haemagglutinin genes found these viruses to have the highest degree of similarity to the classical swine H1 viruses circulating in Asia and North America. The neuraminidase gene and the internal genes were found to be more closely related to viruses circulating in European swine, which appear to have undergone multiple reassorting events. Although transmission of swine influenza to humans appears to be a relatively rare event, swine have been proposed as the intermediate host in the generation of potential pandemic influenza virus that may have the capacity to cause human epidemics resulting in high morbidity and mortality.

Retrospective swine influenza serological surveillance in the four highest pig density provinces of Thailand before the introduction of the 2009 pandemic Influenza A virus subtype H1N1 using various antibody detection assays

“…5,27 In addition, the endemic swine H1N1 virus had been reported in 1 human case in 2005 in Thailand. 16 Moreover, sera from rabbit inoculated with pH1N1-09 showed no cross antibody reactivity to other Thai swine H1N1 viruses, and all sera tested in the present study had no cross-reactivity to pH1N1-09 (unpublished data). Hence, the HI test using pH1N1-09 virus antigen could be applied for the pandemic H1N1 2009 infected pig detection retrospectively.…”

Adaptive strategies of the influenza virus polymerase for replication in humans

“…Structural models of the PB2 627 domain from 2009 A(H1N1) viruses suggest that the SR polymorphism functions by neutralizing E627 and partially re- storing the positively charged surface of the 627 domain. Sequence analysis of two other swine-origin viruses from humans, A/Indonesia/CDC644/2006 and A/Thailand/271/2005, imply a similar strategy in which a lysine at PB2 position 591 is paired with a glutamic acid at position 627 (37). Thus, other viruses may evade restriction in human cells by introducing mutations into the PB2 627 domain or other regions of the polymerase complex that neutralize a glutamic acid present at PB2 residue 627.…”

Rapid generation of pandemic influenza virus vaccine candidate strains using synthetic DNA

“…The H5N1 mouse monoclonal antibodies were raised against NIBRG‐14 (mAb 151) or A/Bar Headed Goose/Qinghai/1A/2005 (mAbs 165, 166, 168). For swine H1N1 influenza haemagglutinin assays, antisera were collected from ferrets infected with wild‐type A/California/07/2009 (H1N1), A/Auckland/1/2009 (H1N1), A/Brisbane/2013/2009 (H1N1), and the swine‐derived human isolate A/Philippines/344/2004 (H1N2) 15 . Seronegative control sera were collected from uninfected ferrets.…”