Molecular Characterization of Seasonal Influenza A and B from Hospitalized Patients in Thailand in 2018–2019

Influenza viruses continue to be a major public health threat due to the possible emergence of more virulent influenza virus strains resulting from dynamic changes in virus adaptability, consequent of functional mutations and antigenic drift in surface proteins, especially hemagglutinin (HA) and neuraminidase (NA). In this study, we describe the genetic and evolutionary characteristics of H1N1, H3N2, and influenza B strains detected in severe cases of seasonal influenza in Thailand from 2018 to 2019. We genetically characterized seven A/H1N1 isolates, seven A/H3N2 isolates, and six influenza B isolates. Five of the seven A/H1N1 viruses were found to belong to clade 6B.1 and were antigenically similar to A/Switzerland/3330/2017 (H1N1), whereas two isolates belonged to clade 6B.1A1 and clustered with A/Brisbane/02/2018 (H1N1). Interestingly, we observed additional mutations at antigenic sites (S91R, S181T, T202I) as well as a unique mutation at a receptor binding site (S200P). Three-dimensional (3D) protein structure analysis of hemagglutinin protein reveals that this unique mutation may lead to the altered binding of the HA protein to a sialic acid receptor. A/H3N2 isolates were found to belong to clade 3C.2a2 and 3C.2a1b, clustering with A/Switzerland/8060/2017 (H3N2) and A/South Australia/34/2019 (H3N2), respectively. Amino acid sequence analysis revealed 10 mutations at antigenic sites including T144A/I, T151K, Q213R, S214P, T176K, D69N, Q277R, N137K, N187K, and E78K/G. All influenza B isolates in this study belong to the Victoria lineage. Five out of six isolates belong to clade 1A3-DEL, which relate closely to B/Washington/02/2009, with one isolate lacking the three amino acid deletion on the HA segment at position K162, N163, and D164. In comparison to the B/Colorado/06/2017, which is the representative of influenza B Victoria lineage vaccine strain, these substitutions include G129D, G133R, K136E, and V180R for HA protein. Importantly, the susceptibility to oseltamivir of influenza B isolates, but not A/H1N1 and A/H3N2 isolates, were reduced as assessed by the phenotypic assay. This study demonstrates the importance of monitoring genetic variation in influenza viruses regarding how acquired mutations could be associated with an improved adaptability for efficient transmission.

Download Full-text

Analysis of influenza A virus reinfection in children in Japan during 1983–91

Epidemiology and Infection ◽

10.1017/s0950268800058751 ◽

1995 ◽

Vol 115 (3) ◽

pp. 591-601 ◽

Cited By ~ 5

Author(s):

S. Nakajima ◽

F. Nishikawa ◽

K. Nakamura ◽

K. Nakajima

Keyword(s):

Amino Acid ◽

Influenza A Virus ◽

Influenza A ◽

Haemagglutination Inhibition ◽

Influenza Viruses ◽

Antigenic Drift ◽

H3n2 Virus ◽

Influenza B ◽

Influenza A H1n1 ◽

Influenza H3n2

SummaryThe epidemiology of influenza A in Japan was studied during 1979–91 and viruses isolated from reinfections during 1983–91 were analysed, Of 2963 influenza viruses isolated during this period, 922 and 1006 were influenza A(H1N1) and A(H3N2) viruses respectively; the others were influenza B viruses. Influenza A(H1N1) and A(H3N2) caused 5 and 6 epidemics respectively, most accompanied by antigenic drift. Seventeen reinfections with H1N1 and 17 with H3N2 were detected during our study. The primary and reinfection strains isolated from 7 H1N1 and 10 H3N2 cases were studied by haemagglutination-inhibition, and amino acid and nucleotide sequences of the HA1 region of the haemagglutinin. Most of the primary and reinfection strains were antigenically and genetically similar to the epidemic viruses circulating at that time. However, in 4 out of 10 cases of reinfection with influenza H3N2 virus, reinfection strains were genetically different from the epidemic viruses.

Download Full-text

The Molecular Basis for Antigenic Drift of Human A/H2N2 Influenza Viruses

Journal of Virology ◽

10.1128/jvi.01907-18 ◽

2019 ◽

Vol 93 (8) ◽

Cited By ~ 6

Author(s):

M. Linster ◽

E. J. A. Schrauwen ◽

S. van der Vliet ◽

D. F. Burke ◽

P. Lexmond ◽

...

Keyword(s):

Amino Acid ◽

Influenza A ◽

Influenza Pandemic ◽

Virus Evolution ◽

Influenza Viruses ◽

Antigenic Drift ◽

Amino Acid Substitutions ◽

Receptor Binding Site ◽

Antigenic Evolution ◽

H2n2 Virus

ABSTRACTInfluenza A/H2N2 viruses caused a pandemic in 1957 and continued to circulate in humans until 1968. The antigenic evolution of A/H2N2 viruses over time and the amino acid substitutions responsible for this antigenic evolution are not known. Here, the antigenic diversity of a representative set of human A/H2N2 viruses isolated between 1957 and 1968 was characterized. The antigenic change of influenza A/H2N2 viruses during the 12 years that this virus circulated was modest. Two amino acid substitutions, T128D and N139K, located in the head domain of the H2 hemagglutinin (HA) molecule, were identified as important determinants of antigenic change during A/H2N2 virus evolution. The rate of A/H2N2 virus antigenic evolution during the 12-year period after introduction in humans was half that of A/H3N2 viruses, despite similar rates of genetic change.IMPORTANCEWhile influenza A viruses of subtype H2N2 were at the origin of the Asian influenza pandemic, little is known about the antigenic changes that occurred during the twelve years of circulation in humans, the role of preexisting immunity, and the evolutionary rates of the virus. In this study, the antigenic map derived from hemagglutination inhibition (HI) titers of cell-cultured virus isolates and ferret postinfection sera displayed a directional evolution of viruses away from earlier isolates. Furthermore, individual mutations in close proximity to the receptor-binding site of the HA molecule determined the antigenic reactivity, confirming that individual amino acid substitutions in A/H2N2 viruses can confer major antigenic changes. This study adds to our understanding of virus evolution with respect to antigenic variability, rates of virus evolution, and potential escape mutants of A/H2N2.

Download Full-text

Plasticity of the Influenza Virus H5 HA Protein

mBio ◽

10.1128/mbio.03324-20 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Huihui Kong ◽

David F. Burke ◽

Tiago Jose da Silva Lopes ◽

Kosuke Takada ◽

Masaki Imai ◽

...

Keyword(s):

Influenza Virus ◽

Amino Acid ◽

Mammalian Cells ◽

Influenza A ◽

Viral Antigen ◽

Influenza Viruses ◽

Influenza A Viruses ◽

Highly Pathogenic ◽

Antigenic Properties ◽

Ha Protein

ABSTRACT Since the emergence of highly pathogenic avian influenza viruses of the H5 subtype, the major viral antigen, hemagglutinin (HA), has undergone constant evolution, resulting in numerous genetic and antigenic (sub)clades. To explore the consequences of amino acid changes at sites that may affect the antigenicity of H5 viruses, we simultaneously mutated 17 amino acid positions of an H5 HA by using a synthetic gene library that, theoretically, encodes all combinations of the 20 amino acids at the 17 positions. All 251 mutant viruses sequenced possessed ≥13 amino acid substitutions in HA, demonstrating that the targeted sites can accommodate a substantial number of mutations. Selection with ferret sera raised against H5 viruses of different clades resulted in the isolation of 39 genotypes. Further analysis of seven variants demonstrated that they were antigenically different from the parental virus and replicated efficiently in mammalian cells. Our data demonstrate the substantial plasticity of the influenza virus H5 HA protein, which may lead to novel antigenic variants. IMPORTANCE The HA protein of influenza A viruses is the major viral antigen. In this study, we simultaneously introduced mutations at 17 amino acid positions of an H5 HA expected to affect antigenicity. Viruses with ≥13 amino acid changes in HA were viable, and some had altered antigenic properties. H5 HA can therefore accommodate many mutations in regions that affect antigenicity. The substantial plasticity of H5 HA may facilitate the emergence of novel antigenic variants.

Download Full-text

Evolutionary, genetic, structural characterization and its functional implications for the influenza A (H1N1) infection outbreak in India from 2009 to 2017

Scientific Reports ◽

10.1038/s41598-019-51097-w ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 3

Author(s):

Sara Jones ◽

Shijulal Nelson-Sathi ◽

Yejun Wang ◽

Raji Prasad ◽

Sabrina Rayen ◽

...

Keyword(s):

Influenza A ◽

Influenza Viruses ◽

Surface Proteins ◽

Antigenic Drift ◽

Global Perspective ◽

Global Circulation ◽

Influenza A H1n1 ◽

Indian Isolates ◽

H1n1 Strain ◽

The Tropics

Abstract Influenza A (H1N1) continues to be a major public health threat due to possible emergence of a more virulent H1N1 strain resulting from dynamic changes in virus adaptability consequent to functional mutations and antigenic drift in the hemagglutinin (HA) and neuraminidase (NA) surface proteins. In this study, we describe the genetic and evolutionary characteristics of H1N1 strains that circulated in India over a period of nine years from 2009 to 2017 in relation to global strains. The finding is important from a global perspective since previous phylogenetic studies have suggested that the tropics contributed substantially to the global circulation of influenza viruses. Bayesian phylogenic analysis of HA sequences along with global strains indicated that there is a temporal pattern of H1N1 evolution and clustering of Indian isolates with globally circulating strains. Interestingly, we observed four new amino acid substitutions (S179N, I233T, S181T and I312V) in the HA sequence of H1N1 strains isolated during 2017 and two (S181T and I312V) were found to be unique in Indian isolates. Structurally these two unique mutations could lead to altered glycan specificity of the HA gene. Similarly, sequence and structural analysis of NA domain revealed that the presence of K432E mutation in H1N1 strains isolated after 2015 from India and in global strains found to induce a major loop shift in the vicinity of the catalytic site. The findings presented here offer an insight as to how these acquired mutations could be associated to an improved adaptability of the virus for efficient human transmissibility.

Download Full-text

Epidemiology and pathogenesis of influenza

Journal of Antimicrobial Chemotherapy ◽

10.1093/jac/44.suppl_2.3 ◽

1999 ◽

Vol 44 (suppl_2) ◽

pp. 3-9 ◽

Cited By ~ 120

Author(s):

Maria C. Zambon

Keyword(s):

Neutralizing Antibodies ◽

Influenza A ◽

Systemic Disease ◽

Influenza Viruses ◽

The Body ◽

Antigenic Drift ◽

Host Cells ◽

Influenza B ◽

Systemic Complications ◽

Segmented Genome

Abstract Influenza A, B and C all have a segmented genome, although only certain influenza A subtypes and influenza B cause severe disease in humans. The two major proteins of influenza are the surface glycoproteins—haemagglutinin (HA) and neuraminidase (NA). HA is the major antigen for neutralizing antibodies and is involved in the binding of virus particles to receptors on host cells. Pandemics are a result of novel virus subtypes of influenza A, created by reassortment of the segmented genome (antigenic shift), whereas annual epidemics are a result of evolution of the surface antigens of influenza A and B virus (antigenic drift). The rapid evolution of influenza viruses highlights the importance of surveillance in identifying novel circulating strains. Infectivity of influenza depends on the cleavage of HA by specific host proteases, whereas NA is involved in the release of progeny virions from the cell surface and prevents clumping of newly formed virus. In birds, the natural hosts of influenza, the virus causes gastrointestinal infection and is transmitted via the faeco-oral route. Virulent avian influenza strains, which cause systemic disease, have an HA that is cleaved by proteases present in all cells of the body, rather than by proteases restricted to the intestinal tract. In mammals, replication of influenza subtypes appears restricted to respiratory epithelial cells. Most symptoms and complications, therefore, involve the respiratory tract. However, systemic complications are sometimes observed and other viral genes besides the HA, including the NA, may be involved in determination of virulence of influenza strains in mammals.

Download Full-text

Amino Acid 226 in the Hemagglutinin of H9N2 Influenza Viruses Determines Cell Tropism and Replication in Human Airway Epithelial Cells

Journal of Virology ◽

10.1128/jvi.02827-06 ◽

2007 ◽

Vol 81 (10) ◽

pp. 5181-5191 ◽

Cited By ~ 181

Author(s):

Hongquan Wan ◽

Daniel R. Perez

Keyword(s):

Amino Acid ◽

Influenza A ◽

Airway Epithelial Cells ◽

Influenza Viruses ◽

Cell Tropism ◽

Airway Epithelial ◽

Receptor Binding Site ◽

Human Virus ◽

Human Airway

ABSTRACT Influenza A viruses of the H9N2 subtype are endemic in poultry in many Eurasian countries and have occasionally caused clinical respiratory diseases in humans. While some avian H9N2 viruses have glutamine (Q) at amino acid position 226 of the hemagglutinin (HA) receptor-binding site, an increasing number of isolates have leucine (L) at this position, which has been associated with the establishment of stable lineages of the H2 and H3 subtypes of viruses in humans. Little is known about the importance of this molecular trait in the infection of H9N2 viruses in humans. We show here that during the course of a single cycle of infection in human airway epithelial (HAE) cells cultured in vitro, the L-226-containing H9N2 viruses displayed human virus-like cell tropisms (preferentially infecting nonciliated cells) different from the tropisms showed by Q-226-containing H9N2 isolates (which infect both ciliated and nonciliated cells at ratios of 1:1 to 3:2) or other waterfowl viruses (which preferentially infect ciliated cells). During multiple cycles of replication in HAE cultures, L-226-containing H9N2 isolates grew consistently more efficiently and reached approximately 100-fold-higher peak titers than those containing Q-226, although peak titers were significantly lower than those induced by human H3N2 viruses. Our results suggest that the variation in residue 226 in the HA affects both cell tropism and replication of H9N2 viruses in HAE cells and may have implications for the abilities of these viruses to infect humans.

Download Full-text

The evolution of human influenza viruses

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2001.0999 ◽

2001 ◽

Vol 356 (1416) ◽

pp. 1861-1870 ◽

Cited By ~ 278

Author(s):

Alan J. Hay ◽

Victoria Gregory ◽

Alan R. Douglas ◽

Yi Pu Lin

Keyword(s):

Influenza A ◽

Influenza Viruses ◽

Antigenic Drift ◽

Influenza B ◽

Mixed Infections ◽

Human Influenza ◽

Influenza A Viruses ◽

Genetic Reassortment ◽

Influenza Ah1n1 ◽

Novel Influenza A

The evolution of influenza viruses results in (i) recurrent annual epidemics of disease that are caused by progressive antigenic drift of influenza A and B viruses due to the mutability of the RNA genome and (ii) infrequent but severe pandemics caused by the emergence of novel influenza A subtypes to which the population has little immunity. The latter characteristic is a consequence of the wide antigenic diversity and peculiar host range of influenza A viruses and the ability of their segmented RNA genomes to undergo frequent genetic reassortment (recombination) during mixed infections. Contrasting features of the evolution of recently circulating influenza AH1N1, AH3N2 and B viruses include the rapid drift of AH3N2 viruses as a single lineage, the slow replacement of successive antigenic variants of AH1N1 viruses and the co–circulation over some 25 years of antigenically and genetically distinct lineages of influenza B viruses. Constant monitoring of changes in the circulating viruses is important for maintaining the efficacy of influenza vaccines in combating disease.

Download Full-text

Epidemiology of seasonal influenza in Bangkok between 2009 and 2012

The Journal of Infection in Developing Countries ◽

10.3855/jidc.2929 ◽

2013 ◽

Vol 7 (10) ◽

pp. 734-740 ◽

Cited By ~ 11

Author(s):

Slinporn Prachayangprecha ◽

Jarika Makkoch ◽

Kamol Suwannakarn ◽

Preeyaporn Vichaiwattana ◽

Sumeth Korkong ◽

...

Keyword(s):

Rainy Season ◽

Influenza A ◽

Seasonal Influenza ◽

Seasonal Pattern ◽

Laboratory Data ◽

Influenza Virus Infection ◽

Influenza Viruses ◽

Influenza B ◽

Rainy Period ◽

Influenza Activity

Introduction: This study investigated influenza activity in Bangkok, Thailand between June 2009 and July 2012. Methodology: Real-time reverse transcription polymerase chain reaction (RT-PCR) was performed to detect influenza viruses among patients with influenza-like illnesses. Results: Of the 6417 patients tested, influenza virus infection was detected in 42% (n = 2697) of the specimens. Influenza A pH1N1 viruses comprised the predominant strain between 2009 and 2010, and seasonal influenza (H3) had a high prevalence in 2011. Laboratory data showed a prevalence and seasonal pattern of influenza viruses. In 2009, influenza activity peaked in July, the rainy season. In 2010, influenza activity happened in two phases, with the initial one at the beginning of the year and another peak between June and August 2010, which again corresponded to the rainy period. Influenza activity was low for several consecutive weeks at the beginning of 2011, and high H3N2 activity was recorded during the rainy season between July and September 2011. However, from the beginning of 2012 through July 2012, pH1N1, influenza H3N2, and influenza B viruses continuously circulated at a very low level. Conclusion: The seasonal pattern of influenza activity in Thailand tended to peak during rainy season between July and September.

Download Full-text

What will the next influenza season bring about: seasonal influenza or the new A(H1N1)v? An analysis of German influenza surveillance data

Eurosurveillance ◽

10.2807/ese.14.32.19303-en ◽

2009 ◽

Vol 14 (32) ◽

Author(s):

H Uphoff ◽

S Geis ◽

A Grüber ◽

A M Hauri

Keyword(s):

Influenza A ◽

Seasonal Influenza ◽

Influenza Season ◽

Influenza Viruses ◽

Moderate Intensity ◽

Influenza Surveillance ◽

Influenza B ◽

Low Intensity ◽

Influenza A H1n1 ◽

Using Data

For the next influenza season (winter 2009-10) the relative contributions to virus circulation and influenza-associated morbidity of the seasonal influenza viruses A(H3N2), A(H1N1) and B, and the new influenza A(H1N1)v are still unknown. We estimated the chances of seasonal influenza to circulate during the upcoming season using data of the German influenza sentinel scheme from 1992 to 2009. We calculated type and subtype-specific indices for past exposure and the corresponding morbidity indices for each season. For the upcoming season 2009-10 our model suggests that it is unlikely that influenza A(H3N2) will circulate with more than a low intensity, seasonal A(H1N1) with more than a low to moderate intensity, and influenza B with more than a low to median intensity. The probability of a competitive circulation of seasonal influenza A with the new A(H1N1)v is low, increasing the chance for the latter to dominate the next influenza season in Germany.

Download Full-text

Serological studies of influenza viruses in pigs in Great Britain 1991–2

Epidemiology and Infection ◽

10.1017/s0950268800052225 ◽

1995 ◽

Vol 114 (3) ◽

pp. 511-520 ◽

Cited By ~ 31

Author(s):

I. H. Brown ◽

P. A. Harris ◽

D. J. Alexander

Keyword(s):

Great Britain ◽

Influenza A ◽

H1n1 Virus ◽

Haemagglutination Inhibition ◽

Influenza Viruses ◽

Antigenic Drift ◽

H3n2 Virus ◽

Influenza B Virus ◽

Influenza B ◽

Influenza A Viruses

SUMMARYSamples from a sow serum bank representative of the pig population of Great Britain collected during 1991–2, were examined for antibodies to influenza A, B and C viruses, using viruses which had been isolated from a variety of hosts. For influenza A viruses there was evidence of the continued circulation of ‘classical swine’ H1N1 virus (26%) seroprevalence), and human H3N2 viruses (39%) which are antigenically most closely-related to A/Port Chalmers/1/73 virus. In addition antibodies were detected to A/swine/England/201635/92 (8%), a strain of H3N2 virus which appears to have arisen by antigenic drift from conventional H3N2 swine strains. Specific antibodies (2%) were detected to an H1N1 virus (A/swine/England/195852/92) related most closely to avian H1N1 strains. In tests with human H1N1 and H3N2 viruses, excluding isolates from pigs, the highest seroprevalence was detected to the prevailing strains from the human population. Serological tests with avian H4 and H10, human H2, equine 1 and 2 influenza A viruses were all negative. Seven pigs seropositive by haemagglutination-inhibition, virus neutralization and immunoblotting assays for antibody to influenza B virus, were randomly distributed geographically suggesting that influenza B viruses may be transmitted to pigs but fail to spread. The seroprevalence to influenza C viruses was 9·9% indicating that these viruses are widespread in pigs. These results provide further evidence that the pig can be infected by a number of influenza viruses, some of which may have significance in the epidemiology of human influenza.

Download Full-text