Nataraj, R. | bioRxiv Science

bioRxiv2024

Decoding non-human mammalian adaptive signatures of 2.3.4.4b H5N1 to assess its human adaptive potential

The recent panzootic 2.3.4.4b clade H5N1 infected diverse non-human mammalian species globally, showed mammal-to-mammal transmission among them and caused sporadic human infections. However, whether 2.3.4.4b H5N1 circulating in non-human mammals can establish human infections and spread among humans is unclear. Gain-of-function research restrictions preclude assessing human adapting mutations of 2.3.4.4b H5N1. Here, we tracked the evolution of 2.3.4.4b H5N1 that infected non-human mammals and evaluated their ability to gain human adaptations. The non-human mammal 2.3.4.4b H5N1 partly acquired classical human adapting mutations, which are identical to the residues of H1N1pdm09 and seasonal human H3N2 infections while showing a few species-specific adaptations that might be potential barriers for successful human adaptations. Despite minimal changes in Hemagglutinin (HA), A160T and T199I mutations near the receptor binding site of HA in dairy cattle viruses indicate the rapid HA glycan surface evolution affecting virus entry and immune evasion. The quantitative assessment indicated that 2.3.4.4b H5N1 circulating in bears, cattle, dolphins, and foxes show higher human adaptive potential than other hosts. Also, H5N1 infections in mammals across time showed a unique set of adaptations in the 2.3.4.4b clade compared to previously circulating strains, especially the acquisition of Q591 adaptation in PB2 that enables human adaptation. Thus, 2.3.4.4b H5N1 acquires human adaptations due to natural selection pressure in non-human mammals. Overall, our study delineates human adaptation and infection risk of specific non-human mammalian circulating HPAI 2.3.4.4b H5N1 strains. O_FIG O_LINKSMALLFIG WIDTH=164 HEIGHT=200 SRC="FIGDIR/small/609722v1_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@2dde4borg.highwire.dtl.DTLVardef@15d4983org.highwire.dtl.DTLVardef@1857093org.highwire.dtl.DTLVardef@1a1eec2_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGRAPHICAL ABSTRACTC_FLOATNO C_FIG

microbiology↗

bioRxiv2024

Avian influenza virus neuraminidase stalk length and haemagglutinin glycosylation patterns reveal molecularly directed reassortment promoting the emergence of highly pathogenic clade 2.3.4.4b A (H5N1) viruses

The recently emerged panzootic clade 2.3.4.4b H5N1 influenza viruses show unprecedented extensive spread in wild birds and have been transmitted to several mammals, including humans. The virologic factors that have driven the success of the 2.3.4.4b H5N1 viruses, which has not been achieved by previous H5N1 clades, is unclear. We show that the 2.3.4.4b H5 haemagglutinin (HA) paired exclusively with full length (long stalk) N1 neuraminidase (NA) in birds and mammals, unlike previous clades of H5 viruses, which preferentially paired with N1 proteins with stalk deletions (short stalk). We found that the emergence of a 2.3.4.4b H5 HA with seven glycosylation sites was critical in driving its pairing with long stalk N1. The earlier H5 clades that paired with short stalk N1s showed a pattern of eight or more glycosylation sites. A prior shift in a glycosylation site from position 103 to 171 in the receptor binding domain of H5 HA and the subsequent S173A mutation that removed it triggered the emergence of 2.3.4.4b clade H5N1 viruses. Thus, the evolution of novel variations in the H5 HA and their preference for long stalk N1 pairing led to increased fitness and pathogenicity. These observations led us to establish and validate the hypothesis that the pairing of avian virus HA and NA subtypes is not stochastic but is rather molecularly programmed by HA glycosylation and NA stalk length, modulating fitness and emergence of novel avian influenza viruses. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=182 SRC="FIGDIR/small/595329v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@1659b26org.highwire.dtl.DTLVardef@1ace4b6org.highwire.dtl.DTLVardef@1db7c0corg.highwire.dtl.DTLVardef@ad3654_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗