scholarly journals Evolutionary conservation of the DRACH signatures of potential N6-methyladenosine (m6A) sites among influenza A viruses

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mahmoud Bayoumi ◽  
Muhammad Munir
Keyword(s):  
Cell Biology ◽  
Influenza A ◽  
Large Scale ◽  
Influenza Infection ◽  
Bioinformatic Analysis ◽  
Sequence Motif ◽  
Sequencing Analysis ◽  
Wild Type ◽  
Influenza A Viruses ◽  
Conservation Patterns

AbstractThe addition of a methyl group to the N6-position of adenosine (m6A) is considered one of the most prevalent internal post-transcriptional modifications and is attributed to virus replication and cell biology. Viral epitranscriptome sequencing analysis has revealed that hemagglutinin (HA) mRNA of H1N1 carry eight m6A sites which are primarily enriched in 5′-DRACH-3′ sequence motif. Herein, a large-scale comparative m6A analysis was conducted to investigate the conservation patterns of the DRACH motifs that corresponding to the reference m6A sites among influenza A viruses. A total of 70,030 complete HA sequences that comprise all known HA subtypes (H1–18) collected over several years, countries, and affected host species were analysed on both mRNA and vRNA strands. The bioinformatic analysis revealed the highest degree of DRACHs conservation among all H1 sequences that clustered largely in the middle and in the vicinity to 3′ end with at least four DRACH motifs were conserved in all mRNA sequences. The major HA-containing subtypes displayed a modest DRACH motif conservation located either in the middle region of HA transcript (H3) or at the 3′ end (H5) or were distributed across the length of HA sequence (H9). The lowest conservation was demonstrated in HA subtypes that infect mostly the wild type avian species and bats. Interestingly, the total number and the conserved DRACH motifs in the vRNA were found to be much lower than those observed in the mRNA. Collectively, the identification of putative m6A topology provides a foundation for the future intervention of influenza infection, replication, and pathobiology in susceptible hosts.

scholarly journals Evaluating the fitness of PA/I38T-substituted influenza A viruses with reduced baloxavir susceptibility in a competitive mixtures ferret model

2020 ◽  
Author(s):  
Leo YY Lee ◽  
Jie Zhou ◽  
Paulina Koszalka ◽  
Rebecca Frise ◽  
Rubaiyea Farrukee ◽  
...  
Keyword(s):  
Influenza A ◽  
Relative Fitness ◽  
Replication Capacity ◽  
Wild Type ◽  
Influenza A Viruses ◽  
Widespread Occurrence ◽  
Host Fitness ◽  
Recombinant Viruses ◽  
Risk Patients ◽  
Virus Isolates

AbstractBaloxavir is approved in several countries for the treatment of uncomplicated influenza in otherwise-healthy and high-risk patients. Treatment-emergent viruses with reduced susceptibility to baloxavir have been detected in clinical trials, but the likelihood of widespread occurrence depends on replication capacity and onward transmission. We evaluated the fitness of A/H3N2 and A/H1N1pdm09 viruses with the polymerase acidic I38T-variant conferring reduced susceptibility to baloxavir relative to wild-type (WT) viruses, using a competitive mixture ferret model, recombinant viruses and patient-derived virus isolates. The A/H3N2 I38T virus showed a reduction in within-host fitness but comparable between-host fitness to the WT virus, while the A/H1N1pdm09 I38T virus had broadly similar within-host fitness but substantially lower between-host fitness. Although I38T viruses replicate and transmit between ferrets, our data suggest that viruses with this amino acid substitution have lower fitness relative to WT and this relative fitness cost was greater in A/H1N1pdm09 viruses than in A/H3N2 viruses.

scholarly journals Broadly Reactive H2 Hemagglutinin Vaccines Elicit Cross-Reactive Antibodies in Ferrets Preimmune to Seasonal Influenza A Viruses

mSphere ◽  
2021 ◽  
Vol 6 (2) ◽  
Author(s):  
Z. Beau Reneer ◽  
Amanda L. Skarlupka ◽  
Parker J. Jamieson ◽  
Ted M. Ross
Keyword(s):  
Influenza Virus ◽  
Immune Responses ◽  
Recombinant Proteins ◽  
Human Population ◽  
Influenza A ◽  
Seasonal Influenza ◽  
Influenza Viruses ◽  
Wild Type ◽  
Influenza A Viruses ◽  
Global Pandemic

ABSTRACT Influenza vaccines have traditionally been tested in naive mice and ferrets. However, humans are first exposed to influenza viruses within the first few years of their lives. Therefore, there is a pressing need to test influenza virus vaccines in animal models that have been previously exposed to influenza viruses before being vaccinated. In this study, previously described H2 computationally optimized broadly reactive antigen (COBRA) hemagglutinin (HA) vaccines (Z1 and Z5) were tested in influenza virus “preimmune” ferret models. Ferrets were infected with historical, seasonal influenza viruses to establish preimmunity. These preimmune ferrets were then vaccinated with either COBRA H2 HA recombinant proteins or wild-type H2 HA recombinant proteins in a prime-boost regimen. A set of naive preimmune or nonpreimmune ferrets were also vaccinated to control for the effects of the multiple different preimmunities. All of the ferrets were then challenged with a swine H2N3 influenza virus. Ferrets with preexisting immune responses influenced recombinant H2 HA-elicited antibodies following vaccination, as measured by hemagglutination inhibition (HAI) and classical neutralization assays. Having both H3N2 and H1N1 immunological memory regardless of the order of exposure significantly decreased viral nasal wash titers and completely protected all ferrets from both morbidity and mortality, including the mock-vaccinated ferrets in the group. While the vast majority of the preimmune ferrets were protected from both morbidity and mortality across all of the different preimmunities, the Z1 COBRA HA-vaccinated ferrets had significantly higher antibody titers and recognized the highest number of H2 influenza viruses in a classical neutralization assay compared to the other H2 HA vaccines. IMPORTANCE H1N1 and H3N2 influenza viruses have cocirculated in the human population since 1977. Nearly every human alive today has antibodies and memory B and T cells against these two subtypes of influenza viruses. H2N2 influenza viruses caused the 1957 global pandemic and people born after 1968 have never been exposed to H2 influenza viruses. It is quite likely that a future H2 influenza virus could transmit within the human population and start a new global pandemic, since the majority of people alive today are immunologically naive to viruses of this subtype. Therefore, an effective vaccine for H2 influenza viruses should be tested in an animal model with previous exposure to influenza viruses that have circulated in humans. Ferrets were infected with historical influenza A viruses to more accurately mimic the immune responses in people who have preexisting immune responses to seasonal influenza viruses. In this study, preimmune ferrets were vaccinated with wild-type (WT) and COBRA H2 recombinant HA proteins in order to examine the effects that preexisting immunity to seasonal human influenza viruses have on the elicitation of broadly cross-reactive antibodies from heterologous vaccination.

scholarly journals Influenza A Viruses Expressing Intra- or Intergroup Chimeric Hemagglutinins

2016 ◽  
Vol 90 (7) ◽  
pp. 3789-3793 ◽  
Author(s):  
Chi-Jene Chen ◽  
Megan E. Ermler ◽  
Gene S. Tan ◽  
Florian Krammer ◽  
Peter Palese ◽  
...  
Keyword(s):  
Growth Kinetics ◽  
Influenza A ◽  
Wild Type ◽  
Influenza A Viruses ◽  
Vaccine Candidates ◽  
Specific Antibodies

A panel of influenza A viruses expressing chimeric hemagglutinins (cHA) with intragroup or intergroup head/stalk combinations was generated. Viruses were characterized for growth kinetics and preservation of stalk epitopes. With a few notable exceptions, cHA viruses behaved similarly to wild-type viruses and maintained stalk epitopes, which indicated their potential as vaccine candidates to induce stalk-specific antibodies.

scholarly journals Comparison of Serum Hemagglutinin and Neuraminidase Inhibition Antibodies After 2010–2011 Trivalent Inactivated Influenza Vaccination in Healthcare Personnel

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Maryrose R. Laguio-Vila ◽  
Mark G. Thompson ◽  
Sue Reynolds ◽  
Sarah M. Spencer ◽  
Manjusha Gaglani ◽  
...  
Keyword(s):  
Influenza Vaccine ◽  
Influenza A ◽  
Influenza Infection ◽  
Fold Increase ◽  
Healthcare Personnel ◽  
Virus Infections ◽  
Influenza A Viruses ◽  
Duration Of Illness ◽  
Antibody Titers ◽  
Influenza Vaccinations

Abstract Background.  Most inactivated influenza vaccines contain purified and standardized hemagglutinin (HA) and residual neuraminidase (NA) antigens. Vaccine-associated HA antibody responses (hemagglutination inhibition [HAI]) are well described, but less is known about the immune response to the NA. Methods.  Serum of 1349 healthcare personnel (HCP) electing or declining the 2010–2011 trivalent-inactivated influenza vaccine ([IIV3], containing A/California/7/2009 p(H1N1), A/Perth/16/2009 [H3N2], B/Brisbane/60/2008 strains) were tested for NA-inhibiting (NAI) antibody by a modified lectin-based assay using pseudotyped N1 and N2 influenza A viruses with an irrelevant (H5) HA. Neuraminidase-inhibiting and HAI antibody titers were evaluated approximately 30 days after vaccination and end-of-season for those with polymerase chain reaction (PCR)-confirmed influenza infection. Results.  In 916 HCP (68%) receiving IIV3, a 2-fold increase in N1 and N2 NAI antibody occurred in 63.7% and 47.3%, respectively. Smaller responses occurred in HCP age >50 years and those without prior 2009–2010 IIV3 nor monovalent A(H1N1)pdm09 influenza vaccinations. Forty-four PCR-confirmed influenza infections were observed, primarily affecting those with lower pre-exposure HAI and NAI antibodies. Higher pre-NAI titers correlated with shorter duration of illness for A(H1N1)pdm09 virus infections. Conclusions.  Trivalent-inactivated influenza vaccine is modestly immunogenic for N1 and N2 antigens in HCP. Vaccines eliciting robust NA immune responses may improve efficacy and reduce influenza-associated morbidity.

scholarly journals Attenuation and immunogenicity in mice of temperature-sensitive influenza viruses expressing truncated NS1 proteins

2005 ◽  
Vol 86 (10) ◽  
pp. 2817-2821 ◽  
Author(s):  
Ana M. Falcón ◽  
Ana Fernandez-Sesma ◽  
Yurie Nakaya ◽  
Thomas M. Moran ◽  
Juan Ortín ◽  
...  
Keyword(s):  
Influenza A ◽  
Influenza Viruses ◽  
Wild Type Virus ◽  
Temperature Sensitive ◽  
Ns1 Protein ◽  
Wild Type ◽  
Influenza A Viruses ◽  
Lethal Challenge

It was previously shown that two mutant influenza A viruses expressing C-terminally truncated forms of the NS1 protein (NS1-81 and NS1-110) were temperature sensitive in vitro. These viruses contain HA, NA and M genes derived from influenza A/WSN/33 H1N1 virus (mouse-adapted), and the remaining five genes from human influenza A/Victoria/3/75 virus. Mice intranasally infected with the NS1 mutant viruses showed undetectable levels of virus in lungs at day 3, whereas those infected with the NS1 wild-type control virus still had detectable levels of virus at this time. Nevertheless, the temperature-sensitive mutant viruses induced specific cellular and humoral immune responses similar to those induced by the wild-type virus. Mice immunized with the NS1 mutant viruses were protected against a lethal challenge with influenza A/WSN/33 virus. These results indicate that truncations in the NS1 protein resulting in temperature-sensitive phenotypes in vitro correlate with attenuation in vivo without compromising viral immunogenicity, an ideal characteristic for live attenuated viral vaccines.

scholarly journals Profound Protection against Respiratory Challenge with a Lethal H7N7 Influenza A Virus by Increasing the Magnitude of CD8+ T-Cell Memory

2000 ◽  
Vol 74 (24) ◽  
pp. 11690-11696 ◽  
Author(s):  
Jan P. Christensen ◽  
Peter C. Doherty ◽  
Kristen C. Branum ◽  
Janice M. Riberdy
Keyword(s):  
T Cells ◽  
T Cell ◽  
Influenza A Virus ◽  
Influenza A ◽  
Memory T Cells ◽  
Influenza Infection ◽  
T Cell Memory ◽  
Influenza A Viruses ◽  
Cell Memory ◽  
Cell Pool

ABSTRACT The recall of CD8+ T-cell memory established by infecting H-2b mice with an H1N1 influenza A virus provided a measure of protection against an extremely virulent H7N7 virus. The numbers of CD8+ effector and memory T cells specific for the shared, immunodominant DbNP366epitope were greatly increased subsequent to the H7N7 challenge, and though lung titers remained as high as those in naive controls for 5 days or more, the virus was cleared more rapidly. Expanding the CD8+ memory T-cell pool (<0.5 to >10%) by sequential priming with two different influenza A viruses (H3N2→H1N1) gave much better protection. Though the H7N7 virus initially grew to equivalent titers in the lungs of naive and double-primed mice, the replicative phase was substantially controlled within 3 days. This tertiary H7N7 challenge caused little increase in the magnitude of the CD8+ DbNP366 + T-cell pool, and only a portion of the memory population in the lymphoid tissue could be shown to proliferate. The great majority of the CD8+ DbNP366 + set that localized to the infected respiratory tract had, however, cycled at least once, though recent cell division was shown not to be a prerequisite for T-cell extravasation. The selective induction of CD8+ T-cell memory can thus greatly limit the damage caused by a virulent influenza A virus, with the extent of protection being directly related to the number of available responders. Furthermore, a large pool of CD8+ memory T cells may be only partially utilized to deal with a potentially lethal influenza infection.

scholarly journals Notorious Novel Avian Influenza Viruses H10N8 and H7N9 in China in 2013 Co-originated from H9N2

2014 ◽  
Author(s):  
Liang Chen ◽  
Feng Zhu ◽  
Chenglong Xiong ◽  
Zhijie Zhang ◽  
Lufang Jiang ◽  
...  
Keyword(s):  
Avian Influenza ◽  
Influenza A ◽  
Phylogenetic Trees ◽  
Large Scale ◽  
Southern China ◽  
Influenza Viruses ◽  
Influenza A Viruses ◽  
Avian Influenza Viruses ◽  
Virus Reassortment ◽  
Epidemiological Characteristics

In 2013, two new avian influenza viruses (AIVs) H7N9 and H10N8 emerged in China caused worldwide concerns. Previous studies have studied their originations independently; this study is the first time to investigate their co-originating characteristics. Gene segments of assorted subtype influenza A viruses, as well as H10N8 and H7N9, were collected from public database. With the help of series software, small and large-scale phylogenetic trees, mean evolutionary rates, and divergence years were obtained successionally. The results demonstrated the two AIVs co-originated from H9N2, and shared a spectrum of mutations in common on many key sites related to pathogenic, tropism and epidemiological characteristics. For a long time, H9N2 viruses had been circulated in eastern and southern China; poultry was the stable and lasting maintenance reservoir. High carrying rate of AIVs H9N2 in poultry had an extremely high risk of co-infections with other influenza viruses, which increased the risk of virus reassortment. It implied that novel AIVs reassortants based on H9N2 might appear and prevail at any time in China; therefore, surveillance of H9N2 AIVs should be given a high priority.

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