Host factors drive the within-host competition between highly and low pathogenic H5N8 avian influenza viruses

Abstract

Highly pathogenic avian influenza viruses (HPAIV) emerge from low pathogenic avian influenza viruses (LPAIV) through the introduction of basic amino acids at the hemagglutinin (HA) cleavage site. Following viral evolution, the newly formed HPAIV likely represents a minority variant within the index host, predominantly infected with the LPAIV precursor. Using reverse-genetics engineered H5N8 viruses differing solely at the HA cleavage, we tested the hypothesis that the interaction between the minority HPAIV and the majority LPAIV could modulate the risk of HPAIV emergence and that the nature of the interaction could depend on the host species. In chickens, we observed that the H5N8 LP increased H5N8 HP replication and pathogenesis. By contrast, the H5N8 LP antagonized H5N8 HP replication and pathogenesis in ducks. Ducks mounted a more potent antiviral innate immune response than chickens against the H5N8 LP , which correlated with H5N8 HP inhibition. Our results provide evidence that HPAIV may be more likely to emerge in chickens than in ducks because of differences in the host response to HPAIV and LPAIV co-infections.

Australia as a global sink for the genetic diversity of avian influenza A virus

“…Wild birds, particularly Anseriformes (ducks, geese and swans), and to a lesser extent Charadriiformes (shorebirds and gulls), are central reservoirs of AIV, with 16 of the 18 HA (haemagglutinin) and 9 of the 11 NA (neuraminidase) subtypes identified in these taxa [ 6 , 17 , 18 ]. AIVs do not generally cause high morbidity or mortality in their hosts, with the exception of subtype H5 and H7 HPAIVs that emerge in poultry [ 5 , 19 – 21 ]. In northern hemisphere systems, the prevalence of AIV peaks in the autumn, driven by the recruitment of immunologically naïve juvenile avian hosts and population congregations associated with migration [ 8 , 9 , 18 , 22 ].…”

Australia as a global sink for the genetic diversity of avian influenza A virus

“…Wild birds, particularly Anseriformes (ducks, geese and swans), and to a lesser extent Charadriiformes (shorebirds and gulls), are central reservoirs of AIV, with 16 of the 18 HA (haemagglutinin) and 9 of the 11 NA (neuraminidase) subtypes identified in these taxa [6,17,18]. AIVs do not generally cause high morbidity or mortality in their hosts, with the exception of subtype H5 and H7 HPAIVs that emerge in poultry [5,[19][20][21]. In northern hemisphere systems, the prevalence of AIV peaks in the autumn, driven by the recruitment of immunologically naïve juvenile avian hosts and population congregations associated with migration [8,9,18,22].…”