Highly pathogenic avian influenza A(H5N1) viruses of clade 2.3.4.4b underwent an explosive geographic expansion in 2021 among wild birds and domestic poultry across Asia, Europe, and Africa. By the ...end of 2021, 2.3.4.4b viruses were detected in North America, signifying further intercontinental spread. Here we show that the western movement of clade 2.3.4.4b was quickly followed by reassortment with viruses circulating in wild birds in North America, resulting in the acquisition of different combinations of ribonucleoprotein genes. These reassortant A(H5N1) viruses are genotypically and phenotypically diverse, with many causing severe disease with dramatic neurologic involvement in mammals. The proclivity of the current A(H5N1) 2.3.4.4b virus lineage to reassort and target the central nervous system warrants concerted planning to combat the spread and evolution of the virus within the continent and to mitigate the impact of a potential influenza pandemic that could originate from similar A(H5N1) reassortants.
In August 2021, we detected highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b viruses in poultry in southern Benin. The isolates were genetically similar to H5N1 viruses of clade 2.3.4.4b ...isolated during the same period in Africa and Europe. We also found evidence for 2 separate introductions of these viruses into Benin.
mRNA lipid nanoparticle (LNP) vaccines would be useful during an influenza virus pandemic since they can be produced rapidly and do not require the generation of egg-adapted vaccine seed stocks. ...Highly pathogenic avian influenza viruses from H5 clade 2.3.4.4b are circulating at unprecedently high levels in wild and domestic birds and have the potential to adapt to humans. Here, we generate an mRNA lipid nanoparticle (LNP) vaccine encoding the hemagglutinin (HA) glycoprotein from a clade 2.3.4.4b H5 isolate. The H5 mRNA-LNP vaccine elicits strong T cell and antibody responses in female mice, including neutralizing antibodies and broadly-reactive anti-HA stalk antibodies. The H5 mRNA-LNP vaccine elicits antibodies at similar levels compared to whole inactivated vaccines in female mice with and without prior H1N1 exposures. Finally, we find that the H5 mRNA-LNP vaccine is immunogenic in male ferrets and prevents morbidity and mortality of animals following 2.3.4.4b H5N1 challenge. Together, our data demonstrate that a monovalent mRNA-LNP vaccine expressing 2.3.4.4b H5 is immunogenic and protective in pre-clinical animal models.
The influenza endonuclease is an essential subdomain of the viral RNA polymerase. It processes host pre-mRNAs to serve as primers for viral mRNA and is an attractive target for antiinfluenza drug ...discovery. Compound L-742,001 is a prototypical endonuclease inhibitor, and we found that repeated passaging of influenza virus in the presence of this drug did not lead to the development of resistant mutant strains. Reduced sensitivity to L-742,001 could only be induced by creating point mutations via a random mutagenesis strategy. These mutations mapped to the endonuclease active site where they can directly impact inhibitor binding. Engineered viruses containing the mutations showed resistance to L-742,001 both in vitro and in vivo, with only a modest reduction in fitness. Introduction of the mutations into a second virus also increased its resistance to the inhibitor. Using the isolated wild-type and mutant endonuclease domains, we used kinetics, inhibitor binding and crystallography to characterize how the two most significant mutations elicit resistance to L-742,001. These studies lay the foundation for the development of a new class of influenza therapeutics with reduced potential for the development of clinical endonuclease inhibitor-resistant influenza strains.
Migratory birds play a major role in spreading influenza viruses over long distances. We report highly pathogenic avian influenza A(H5N6) viruses in migratory and resident ducks in Bangladesh. The ...viruses were genetically similar to viruses detected in wild birds in China and Mongolia, suggesting migration-associated dissemination of these zoonotic pathogens.
Influenza is a serious hazard to human health that causes hundreds of thousands of deaths annually. Though vaccines and current therapeutics can blunt some of the perilous impact of this viral ...infection, new treatments are needed due to the constantly evolving nature of this virus. Recently, our growing understanding of an essential influenza viral protein, PA, has led to the development of focused libraries of new small molecules that specifically target the active site of the PA influenza endonuclease, which we report here. Our overarching approach has been to proactively develop lead inhibitors that are less likely to rapidly develop clinical resistance by optimizing inhibitors that retain activity against induced resistant mutants. Here, we report details behind the discovery of new potent inhibitors of wild type and resistant mutant endonucleases along with their high-resolution co-crystal structure-activity relationships. These results add to our understanding of nuclease protein targets and potentially serve as starting points for a new therapeutic approach to the treatment of influenza.
In 2017, a novel influenza A virus (IAV) was isolated from an Egyptian fruit bat. In contrast to other bat influenza viruses, the virus was related to avian A(H9N2) viruses and was probably the ...result of a bird-to-bat transmission event. To determine the cross-species spill-over potential, we biologically characterize features of A/bat/Egypt/381OP/2017(H9N2). The virus has a pH inactivation profile and neuraminidase activity similar to those of human-adapted IAVs. Despite the virus having an avian virus-like preference for α2,3 sialic acid receptors, it is unable to replicate in male mallard ducks; however, it readily infects ex-vivo human respiratory cell cultures and replicates in the lungs of female mice. A/bat/Egypt/381OP/2017 replicates in the upper respiratory tract of experimentally-infected male ferrets featuring direct-contact and airborne transmission. These data suggest that the bat A(H9N2) virus has features associated with increased risk to humans without a shift to a preference for α2,6 sialic acid receptors.
CREB is a key mediator of cAMP‐ and calcium‐inducible transcription, where phosphorylation of serine 133 in its Kinase‐Inducible Domain (KID) is often equated with transactivation. Phospho‐Ser133 is ...required for CREB to bind the KIX domain of the coactivators CBP and p300 (CBP/p300) in vitro, although the importance of this archetype coactivator interaction for endogenous gene expression is unclear. Here, we show that the CREB interaction with KIX is necessary for only a part of cAMP‐inducible transcription and CBP/p300 recruitment. Surprisingly, individual cAMP‐inducible genes with CREB bound at their promoters differed in their reliance on KIX and none examined showed complete dependence. Alternatively, we found that arginine 314 (Arg314) in the CREB basic‐leucine zipper (bZIP) domain contributed to CBP/p300 recruitment and KIX‐independent CREB transactivation function. This implicates Transducer Of Regulated CREB (TORC), an unrelated cAMP‐responsive coactivator that binds via Arg314, and which can bind CBP/p300, in these functions. Interestingly, KIX was also required for the full cAMP induction of a gene that did not require CREB. Thus, individual CREB‐target gene context dictates the relative contribution of at least two different cAMP‐responsive coactivation mechanisms.
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