Abstract: From examining the protein alignments, we found several residue changes in the seal virus that did not occur in the bird viruses, including D701N in the PB2 segment, a rare mutation, and a hallmark of mammalian adaptation of bird viruses.
Result: Many of these changes occur in the polymerase complex genes: D701N in the PB2 segment is a rare mutation, and a hallmark of mammalian adaptation of bird influenza viruses, regardless of genetic background.
Result: We compared all the substitutions with previously described mutations in seal influenza virus infections, and found that apart from D701N, which was also found in the H3N8 seal virus infection in Massachusetts in 2011, there were no convergent amino acid changes.
Table:
Amino acid substitutions involved in the adaptation of a novel H7N7 avian influenza virus in mice.
PMID: 32200160
2020
Research in veterinary science
Abstract: Genomic analysis of the mouse-adapted virus revealed amino acid changes in the PB2 (E525G, M645I, and D701N), NP (I475V), HA(D103N), and NA(K142E) proteins.
The effect of mutations derived from mouse-adapted H3N2 seasonal influenza A virus to pathogenicity and host adaptation.
Introduction: Furthermore, the E627K and D701N substitutions in the PB2 gene have been commonly detected in mouse-adapted IAVs and related to enhanced virulence in mice.
Low Polymerase Activity Attributed to PA Drives the Acquisition of the PB2 E627K Mutation of H7N9 Avian Influenza Virus in Mammals.
Abstract: Furthermore, the impaired viral polymerase activity of H7N9 AIV caused by the depletion of ANP32A led to reduced virus replication in Anp32a-/- mice, abolishing the acquisition of the PB2 E627K mutation and instead driving the virus to acquire the alternative PB2 D701N mutation.
Introduction: Different mutations in PB2 have been identified to contribute to the adaptation of influenza viruses to mammalian hosts; these mutations include E627K, D701N, T271A, Q591R/K, and E158G.
Introduction: Remarkably, the PB2 of H7N9 viruses easily acquires the PMID: 31173771
2019
Virus research
Abstract: Furthermore, we found that PB2-D701N could enhance viral replication in vitro and in vivo and expanded viral tissue tropism.
Abstract: Our data suggest that PB2-D701N and M1-M192V are the virulence markers of H3N2 avian influenza virus, and these markers can be used in the trans-species transmission surveillance for the H3N2 avian influenza virus.
Abstract: We found that both PB2-D701N mutation and M1-M192V mutation were implicated in the viral pathogenic phenotypic variation of H3N2 avian influenza virus in mice.
PB2 and hemagglutinin mutations confer a virulent phenotype on an H1N2 avian influenza virus in mice.
Abstract: By evaluating the virulence of mouse-adapted H1N2 variants at different generations, we found that the PB2-D701N and HA-G228S mutations both contribute to the virulence of this virus in mammals.
Abstract: Furthermore, we found that the PB2-D701N and HA-G228S mutations both enhance the ability of the virus to replicate in vivo and in vitro and that the PB2-D701N substitution results in an expansion of viral tissue tropism.
Abstract: These results suggest that the PB2-D701N mutation and the HA-
The PB2 Polymerase Host Adaptation Substitutions Prime Avian Indonesia Sub Clade 2.1 H5N1 Viruses for Infecting Humans.
Introduction: Among the known PB2 adaptive substitutions, E627K, and to a lesser extent D701N, are the most common and well characterized in H5N1 human isolates.
Result: Uniquely, the K526R PB2 substitution in Indonesian H5N1 viruses is rarely associated with either E627K or D701N.
Discussion: However, most human H5N1 isolates from Indonesia do not harbor the E627K or D701N substitutions frequently observed in other human isolates from avian H5N1 or H7N9 virus infections.
Discussion: Similarly, a D701N adaptation in a duck H5N1 virus which predisposed towards transmission to a mammalian host has also been reported.
Amino Acid Residue 217 in the Hemagglutinin Glycoprotein Is a Key Mediator of Avian Influenza H7N9 Virus Antigenicity.
Introduction: In addition to human receptor binding characteristics, human H7N9 isolates often possess several other markers of mammalian adaptation, such as E627K and D701N in the PB2 protein.
Prevailing I292V PB2 mutation in avian influenza H9N2 virus increases viral polymerase function and attenuates IFN-beta induction in human cells.
PMID: 31305236
2019
The Journal of general virology
Introduction: To overcome this restriction, the avian PB2 gene needs to acquire certain mutational changes to improve its activity in mammalian cells, as exemplified in PB2-E627K, -D701N, -T271A, -K526R and -A588V.
Discussion: Unlike the PB2-I292V mutation reported in the current study, the well-known human adaptive mutations of PB2-E627K and -D701N are rarely found in prevailing avian H9N2 viruses.
Evolved avian influenza virus (H7N9) isolated from human cases in a middle Yangtze River city in China, from February to April 2017.
Result: Another crucial mutant, a PB2 Asp701Asn substitution, was associated with increased viral polymerase activity, and was also present in A/changsha/26/20
Table: Asp701Asn
Discussion: Previous studies demonstrated that one or more of the Ile292Val, Ala588Val, Glu627Lys, and Asp701Asn substitutions are important for avian influenza viruses to break the host species barrier to infect mammals.
Discussion: The mutation in other sites, including Ile292Val, Ala588Val and D701N in PB2, could be found effective to compensate for the absence of E627K.
IV mutation literature information.
PMID: 
2020
Virus evolution
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