The characteristics of the evolutionary variability of influenza A (H1N1) viruses]

Studies of the antigenic structure of hemagglutinins of influenza A (H1N1) viruses isolated in 1978-1988 using monospecific and monoclonal antibodies demonstrated the strains of the H1N1 subtype to be highly apt to antigenic drift. The evolutional variability of that period was peculiar and characterized by antigenic drift in various directions. In those years, the variants were regularly isolated which had retained the determinants of viruses of 1933-1957 circulation period in their hemagglutinin structure. The variants containing in their hemagglutinin 2 antigenic sites common with A/USSR/090/77 virus and antigenic groupings characterizing the strain specificity of each isolate, were epidemically active. At the same time, epidemically important variants were dominant whose properties were markedly different from those of previously known viruses. Their hemagglutinin contained 2 basically new antigenic determinants. This direction of evolutional development of influenza A (H1N1) virus is the most prospective epidemically.     

Analysis of etiology of influenza-like morbidity and monitoring influenza epidemic of 1998-1999 by laboratory diagnosis methods

The etiological structure of influenza-like was analyzed in the population in cities and towns and in Russia as a whole in November 1998 to April 1999 by the findings of immunofluorescence and serological surveys of patients with acute respiratory viral infections (ARVI). By the results of both tests, the proportion of the incidence of influenza A (H3N2) was largest, the decreasing order in their significance was as follows: adenoviruses, type 3 parainfluenza virus, RSV, influenza B virus, influenza A(H1N1), types 2 and 1 parainfluenza virus. All influenza viruses A(H1N1) were isolated in Samara in February 1999. Three of them were similar to the reference strain A/Johannesburg/82/96 in antigenic properties, two strains appeared to be its drift variants. No A/Beijing/262/95 (H1N1)-like viruses recommended for incorporation as part of vaccines were detected. All influenza A(H3N2) viruses were drift variants of strain A/Sydney/05/97, and all influenza B viruses were similar to the reference strain B/Harbin/07/94 in antigenic structure.     

Influenza viruses which preconditioned the epidemic rise in Russia in 2002-2003. A resumed circulation of influenza viruses similar to V/Victoria/2/87

According to research, the epidemic rise of influenza was preconditioned, during 2002-2003, in Russia by the circulation of influenza A(H1N1), A(H3N2) and B viruses. The Center of Influenza Ecology and Epidemiology undertook a study of 178 epidemic strains: 41 strains A(H1N1), 116 strains A(H3N2) and 21 strains of influenza B were among them. All strains were isolated in the MDCK cell culture. A simultaneous isolation in embryonated eggs as well as changing of the isolation system from MDCK to embryonated eggs were found to be effective only for influenza A(H1N1) viruses. According to the antigenic analysis, all A(H1N1) viruses were variants of the etalon A/New Caledonia/20/99. The A(H3N2) viral strains' population was heterogeneous by its antigenic properties: among its isolates, there were variants similar to the etalons of A/Moscow/10/99 and of A/Panama/200/99 as well as strains, which weakly reacted with sera of both above etalons; possibly the latter were close to the etalon of A/Fujian/411/02. All epidemic strains of influenza B virus belonged, according to the antigenic properties of hemagglutinin, to the virus group of B/Victoria/2/87-like and were antigenic variants of the etalon of B/Hong Kong/22/01. This confirmed that influenza B viruses with the antigenic hemagglutinin structure of the virus group of B/Victoria/2/87-like, which were not present in Russia for more than 10 years, re-entered the active circulation. An analysis of antigenic properties of neuraminidases (NA) of the mentioned epidemic strains showed their different degrees of relationship with the NA etalons of both evolutionary groups, i.e. B/Victoria/2/87 and B/Yamagata/16/88-like. A study of paired sera obtained from patients showed a growth of antibodies to the etalons of influenza A(H1N1), A(H3N2) and B viruses of the season in question, which confirmed the virology data.     

Selection of antigenic variants of H1N1 influenza viruses by means of monoclonal antibodies

Six different monoclonal antibodies to influenza A/Brazil/11/78 virus hemagglutinin were used for selection of antigenic variants of H1N1 viruses: A/USSR/090/77 and A/black-headed gull/ Kaz . SSR/470/79. The group-specific monoclonal antibody completely neutralized the infective activity of the parental viruses (dilutions 1:5 to 1:640). Two antigenic variants of wild type viruses were obtained using cross-reactive antibody. A comparative study of the antigenic structure, biological properties, and peptide maps of the heavy chain of the original viruses, antigenic variants, and some epidemic H1N1 strains was carried out. The selected variants of A/black-headed gull/ Kaz . SSR/470/77 and A/USSR/090/79 viruses were shown to be similar to epidemic H1N1 strains isolated in 1953 and 1978.     

The properties of the epidemic influenza viruses A and B strains circulating in Russia in the 2004-2005 epidemic season

The epidemic upsurge of influenza morbidity in Russia in 2004-2005 was caused by the active circulation of influenza A(H3N2) and B viruses. A hundred and sixty-six epidemic strains were studied. All the strains were isolated in the MCK cell culture. Influenza A(H3N2) viruses (n=77) were antigenic variants of the reference A/Fujian/411/ 2002 and A/California/7/2004 strains. Three influenza A(H1N1) viral strains that were antigenic variants of A/New Caledonia/20/99 strains were isolated in sporadic cases. Influenza B virus strains (n=83) were antigenic variants of the reference B/Shanghai/361/02--lineage B/Yamagata/l6/88. In addition, 3 antigenic variants of B/Hong Kong/ 330/2002 (lineage B/Victoria/2/87) strains were isolated. Nine (20%) strains resistant to rimantadine at a concentration of 5 microg/ml were identified. Chromatographic analysis of B/Shanghai/361/02 and BIHong Kong/330/01 viral protein M1 trypsin hydrolysates revealed differences in the profiles of chromatograms of influenza A virus proteins M1. Examination of 121 pair sera from patients revealed an increase in antibodies to influenza A(H3N2) viruses in 10-21% of cases and to influenza B viruses in 20-36% of cases.     

Genetic characterization of influenza viruses from influenza-related hospital admissions in the St. Petersburg and Valencia sites of the Global Influenza Hospital Surveillance Network during the 2013/14 influenza season

BackgroundContinuous surveillance for genetic changes in circulating influenza viruses is needed to guide influenza prevention and control.ObjectivesTo compare intra-seasonal influenza genetic diversity of hemagglutinin in influenza A strains isolated from influenza hospital admissions collected at two distinct sites during the same season.Study designComparative phylogenetic analysis of full-length hemagglutinin genes from 77 isolated influenza A viruses from the St. Petersburg, Russian Federation and Valencia, Spain sites of the Global Influenza Hospital Surveillance Network (GIHSN) during the 2013/14 season.ResultsWe found significant variability in A(H3N2) and A(H1N1)pdm09 viruses between the two sites, with nucleotide variation at antigenic positions much lower for A(H1N1)pdm09 than for A(H3N2) viruses. For A(H1N1)pdm09, antigenic sites differed by three to four amino acids from the vaccine strain, two of them common to all tested isolates. For A(H3N2) viruses, antigenic sites differed by six to nine amino acids from the vaccine strain, four of them common to all tested isolates. A fifth amino acid substitution in the antigenic sites of A(H3N2) defined a new clade, 3C.2. For both influenza A subtypes, pairwise amino acid distances between circulating viruses and vaccine strains were significantly higher at antigenic than at non-antigenic sites. Whereas A(H1N1)pdm09 viruses clustered with clade 6B and 94% of A(H3N2) with clade 3C.3, at both study sites A(H3N2) clade 3C.2 viruses emerged towards the end of the season, showing greater pairwise amino acid distances from the vaccine strain compared to the predominant clade 3C.3.ConclusionsInfluenza A antigenic variants differed between St. Petersburg and Valencia, and A(H3N2) clade 3C.2 viruses were characterized by more amino acid differences from the vaccine strain, especially at the antigenic sites.     

Antigenic and genomic analyses of influenza A(H1N1) viruses from different regions of the world, February 1978 to March 1980.

Antigenic analysis of influenza A(H1N1) virus isolates by hemagglutination inhibition reactions with postinfection ferret sera and mouse monoclonal antibodies showed that, although the predominant virus in 1978 to 1979 had an A/Brazil/11/78-like hemagglutinin, several new antigenic variants could be detected which differed from those identified in 1977 to 1978. Most of the variants showed very minor changes and did not achieve epidemiological significance. Genome analysis by ribonucleic acid-ribonucleic acid hybridization, and supported by oligonucleotide mapping, indicated that nonrecombinant H1N1 viruses cocirculated in the world with recombinant H1N1 viruses, identified in 1978 to 1979. The results of our antigenic analysis and genomic analysis, in conjunction with genomic analysis by other authors, showed that recombinants with A/USSR/90/77-like and A/Brazil/11/78-like hemagglutinin had different genome compositions, indicating that H3N2 virus recombined separately with these different antigenic variants. Prevalence of the nonrecombinant and recombinant H1N1 viruses varied between regions of the world, and influenza A(H1N1) virus with a genotype almost identical to that of nonrecombinant A/Brazil/11/78 virus reappeared as a cause of local outbreaks in the United States in 1980 despite the predominance of recombinant H1N1 strains in the preceding winter.     

Genetic recombination between natural isolates of influenza virus serotypes H1N1 and H3N2

Oligonucleotide mapping of individual genes was used for search of possible genetic recombinants between natural isolates of influenza H1N1 and H3N2 viruses isolated in the USSR in 1977-1979. No antigenic hybrids and recombinants with the antigenic structure H3N2 were found, however, it was shown that isolates of H1N1 viruses of 1979 (the A/USSR/61/79 strain) might represent genetic recombinants carrying genes P1 + P2 from H3N2 viruses, the M-gene of the USSR/61/79 virus being closest in its structure to the analogous gene of the earliest isolate of H3N2 viruses, namely A/Hong Kong/1/68. Possible selective advantages of virus recombinants having M-genes from viruses of a different serotype are discussed.     

Epidemic strains influenza viruses A and B in the 2005-2006 season in Russia

Investigations indicated that the epidemic upsurge of influenza morbidity in the 2005-2006 season in Russia was caused by the active circulation of influenza viruses A and B. The Center for Ecology and Epidemiology of Influenza, D. I. Ivanovsky Institute of Virology, Russian Academy of Medical Sciences, studied 182 epidemic strains. A hundred and thirteen influenza viruses A(H3N2) were similar to the reference A/California/07/2004 or were its antigenic variants. Thirteen influenza virus A(H1N1) strains that were antigenic variants of the reference A/New Caledonia/20/99 were isolated in sporadic cases. Influenza viruses B were similar to B/Malaysia/2506/2004--lineage B/Victoria/2/87). All the strains were isolated in the MDCK cell culture. Comparative study of the sensitivity of the chicken embryo (CE) and MDCK isolation system to the 1999-2006 epidemic strains showed that CE tropism was least pronounced in influenza viruses A(H3N2). Analysis of the 2002-2006 strains demonstrated that influenza viruses A reacted actively with human erythrocytes of the blood groups 0(I) and A(II) and very slightly with chicken ones. Eighty-five influenza virus A(H3N2) strains from the 2005-2006 epidemic season were investigated for rimantadine susceptibility. The frequency of rimantadine-resistant influenza virus A(H3N2) strains was 38.0%. Studies of 79 paired sera from patients revealed a rise of antibodies to influenza viruses A(H3N2) and B in 25.9-33.3 and 20.7-23.8% of cases, respectively. There was an increase in antibodies to influenza viruses A and B in the sera collected from donors in Moscow and its region in September 2005 to June 2006.     

2004-2008年我国流行的A型流感病毒抗原性及HA1基因特性的研究

目的 了解我国2004-2008年A(H1N1、H3N2)型流感病毒流行情况、抗原性和基因特性变异关系,了解疫苗株与我国流行株之间抗原性变化情况.方法 选择2004年以来我国分离的A(H1N1、H3N2)型流感病毒进行抗原性及HA1区基因序列,通过比对HA1蛋白位点变异情况,分析我国流感病毒抗原性及基因特性变化情况.结果 A(H1N1)亚型流感毒株抗原性2004-2007年分离的A(H1N1)亚型流感病毒的抗原性与疫苗株A/New Caledonia/20/1999(H1N1)类似;2008年我国流行的A(H1N1)亚型毒株的抗原性与2008-2009年北半球的流感疫苗株A/Brisben/59/2007(H1N1)类似.2004-2005年分离的A(H3N2)亚型流感病毒的抗原性与疫苗株A/Fujian/411/12002(H3N2)比较发生了变异;2006-2007年我国流行的H3N2毒株与A/Wiscansin/67/2006(H3N2)类似,2008年我国流行的H3N2毒株与疫苗株A/Brisben/10/2006(H3N2)类似.结论 2004-2008年我国流行的A(H1N1、H3N2)亚型流感病毒的抗原性和基因特性发生了改变.     

Recent changes among human influenza viruses

Recurrent epidemics of influenza are due to the frequent emergence of antigenic variants. With co-circulation of two influenza A subtypes and two antigenically distinct lineages of B viruses, genetic reassortment also has an important role in antigenic drift, as illustrated by recent changes in both A and B viruses. The H1N2 subtype viruses, which emerged during 2001, possessed a H1 HA similar to those of contemporary A/New Caledonia/20/99 (H1N1)-like viruses and seven genes closely related to those of recent H3N2 viruses, and did not represent a significant increase in the antigenic diversity of circulating viruses. The re-emergence of B/Victoria/2/87-lineage viruses, previously prevalent during the 1980s, in 2000 has been followed by the predominant circulation of reassortant B viruses possessing a B/Victoria-lineage HA and a B/Yamagata-lineage NA similar in sequence to those of recent B/Sichuan/379/99-like viruses. These events emphasize not only the lack of divergence in the complementary functional characteristics of the HA and NA of divergent influenza B lineages, but also the apparent convergence in compatibility between the H1 and N2 components of the two influenza A subtypes.     

Characteristics of the causative agents of the influenza A (H3N2) epidemic in Leningrad in 1983

Investigation of influenza A (H3N2) epidemic of 1983 in Leningrad revealed simultaneous circulation of 3 antigenic variants similar to A/Bangkok/1/79, A/Bangkok/2/79, and A/Philippines/2/82 with significant predominance of the first antigenic variant. The viruses related to A/Philippines/2/82 comprising one-third of all isolations produced antibodies of a wide spectrum unlike the other two variants whose antisera neutralize actively the homologous virus only. The possibility of selecting epidemic strains of the A/Philippines/2/82 variety as vaccine strain candidates is discussed.     

Antigenic structure of the hemagglutinin of influenza virus B/Hong Kong/8/73 as determined from gene sequence analysis of variants selected with monoclonal antibodies

Antigenic variation among influenza B viruses is different from that of influenza A in several ways. Antigenic shift has not been observed, distinct antigenic variants of influenza B cocirculate, and antigenically similar viruses have been isolated many years apart. To study the mechanism of antigenic drift in influenza B viruses, monoclonal antibodies were used to select antigenic variants of B/Hong Kong/8/73 virus hemagglutinin (HA). Analyses of the nucleotide sequences of the HA gene of B/Hong Kong/8/73 and the eight variants identified specific regions of the influenza B HA molecule involved in antigenicity, and enabled antigenic mapping data to be correlated with the structure of the protein. The altered amino acids in the variants, when compared to the HA of A/Aichi/2/68, were found in two of the four antigenic regions previously identified for type A viruses. In addition, four of the eight variants showed multiple nucleotide changes some of which gave rise to double amino acid changes. In addition, in the present study monoclonal antibodies which belong to the same antigenic group recognize amino acid changes in regions corresponding to antigenic sites A and B of the H3 HA. These results are in contrast to those obtained with HA variants of A/Memphis/1/71 virus. In the influenza A studies only single amino acid changes were found and these correlated well with the three-dimensional structure as determined by D. C. Wiley, I. A. Wilson, and J. J. Skehel, (1981, Nature (London) 289, 366-373); monoclonal antibodies which recognized one region did not recognize any of the other antigenic sites. Our results suggest that although the basic three-dimensional structure of the influenza B HA may be similar to that of A viruses, the B HA molecule may be folded in a more compact manner so that antigenic sites A and B are in closer proximity to each other than in the H3 structure.     

Genetic variability of epidemic strains of influenza virus serotypes H1N1 and H3N2 during antigenic drift

Data are presented on structural variability of individual genes of selected variants of epidemic influenza viruses H1N1 (1977-1979) and H3N2 (1968-1979) in the course of antigenic drift obtained by oligonucleotide mapping. Six out of 8 genes of H1N1 viruses were found to be more variable than the corresponding genes of H3N2 viruses. Only HA and NS genes of H3N2 viruses underwent greater structural changes as compared with the analogous genes of H1N1 viruses. In viruses of both serotypes, most variable were the genes coding for hemagglutinin and matrix protein. Possible causes of greater structural variability of the matrix protein gene in the course of antigenic drift are discussed.     

Antigenic and genetic variation in the hemagglutinins of H1N1 and H3N2 human influenza a viruses in the Shanghai area from 2005 to 2008

Continued rapid evolution of the influenza A virus is responsible for annual epidemics and occasional pandemics in the Shanghai area. In the present study, the representative strains of A/H1N1 and A/H3N2 influenza viruses isolated in the Shanghai area from 2005 to 2008 were antigenically and genetically characterized. The antigenic cartography method was carried out to visualize the hemagglutination-inhibition data. Antigenic differences were detected between circulating A/H1N1 strains isolated from 2005 to 2006 and the epidemic A/H1N1 strains isolated in 2008, which were found to be associated with the amino acid substitution K140E in HA1. The present vaccine strain A/Brisbane/59/2007 is considered to be capable of providing sufficient immunity against most of the circulating A/H1N1 viruses isolated in 2008 from the Shanghai population. The study showed that there were significant antigenic differences between the epidemic A/H3N2 strains isolated in 2007 and 2008, suggesting that antigenic drift had occurred in the A/H3N2 strains isolated in 2008. The P194L mutation was thought to be responsible for the antigenic evolution of influenza A/H3N2 viruses isolated from Shanghai in 2008. Evidence of antigenic drift suggests that the influenza A/H3N2 vaccine component needs to be updated.     

Immunological analysis of the chronological sequence of the shift in the antigenic determinants of influenza virus A (H1N1) hemagglutinins

The study of the antigenic composition of influenza A (H1N1) viruses of two circulation periods, 1933-1957 and 1977-1981, by the method of selective adsorption of highly active antihemagglutinating sera revealed the ways of antigenic variability of drift variants. The antigenic composition of the hemagglutinin of H1N1 viruses of the second circulation period was found to be similar to that of H1N1 viruses isolated in 1950-1953.     

Determination of the number of nonoverlapping antigenic areas on Hong Kong (H3N2) influenza virus hemagglutinin with monoclonal antibodies and the selection of variants with potential epidemiological significance

Monoclonal antibodies provided evidence for at least three nonoverlapping antigenic areas on the hemagglutinin molecule of A/Mem/V71 (H3N2) influenza virus. This was established by determining the reactivity patterns of 30 different monoclonal antibodies in hemagglutination-inhibition tests and by the failure to select antigenic variants of influenza virus when monoclonal antibodies from two nonoverlapping areas were used in combination. Antigenic analysis showed that most of the variants selected with monoclonal antibodies could not be distinguished from the parental virus with heterogeneous sera, suggesting that they are probably epidemiologically irrelevant. One variant, however, could be distinguished from the parental virus with heterogeneous sera and this variant had a change in sequence at residue 144 of the HAl polypeptide, from glycine in the parent to aspartic acid in the variant. A similar amino acid change has been found in naturally occurring variants at this residue. These studies suggest that some amino acid substitutions are more important than others for producing viruses with epidemiological potential. Antigenic analysis of naturally occurring H3N2 strains with monoclonal antibodies showed that antigenic variation occurs in each nonoverlapping antigenic area of the HA molecule and established that two distinct variants cocirculated in 1968, Hong Kong/1/68 being distinguishable from Aichi/2/68 in at least two antigenic areas. It appears that there may have been two separate lineages of H3N2 viruses, Hong Kong/1/68 giving rise to variants in England and Aichi/2/68 to variants in the USA and Australia.     

Hemagglutinin antigenic determinants of influenza viruses H1N1 isolated 1953-1957 in the composition of the hemagglutinins of influenza viruses H1N1 isolated 1978-1979

Immunological analysis of antigenic determinants in the composition of hemagglutinins (HA) of H1N1 viruses isolated in the epidemic season of 1978-1979 showed their difference from A/USSR/090/77 virus HA. The A/Brazil/11/78 HA is characterized by 3 antigenic determinants two of which are identical with those of A/USSR/090/77 HA and one shows relationship with HA determinant of A/Omachi/1/53 virus, A/Fukushima/103/78 and A/Kagoshima/22/79 HAs are characterized by 1 determinant common with that of A/USSR/090/77 HA and 2 determinants identical with A/Omachi/1/53 virus HA. HAs of these viruses contain a determinant responsible for the antigenic relation of A/Omahi/1/53 HA with that of H1N1 viruses isolated in 1956-1957. The results suggest that the antigenic drift of HA of H1N1 viruses isolated in 1977-1979 occurs by the cycle characteristic of HA of H1N1 viruses isolated in 1950-1957. By the sensitivity to alpha-, beta-, and gamma-inhibitory of rabbit serum H1N1 viruses isolated in 1947-1957 and in 1977-1979 are quite similar with the exception of A/USSR/184/79 virus showing high sensitivity to gamma-inhibitors like H2N2 and H2N2 viruses.     

Spread and properties of epidemic influenza A and B virus strains accountable for morbidity in Russia during 1999-2002

The strains of influenza A -A(H1N1), A(H3N2) and B viruses were shown in the paper to have been circulating in Russia in 1999-2002. A co-circulation of viruses of 2 to 3 types was detected in all epidemic seasons. A majority of strains was isolated on the culture of cells MDCK. A study of epidemic strains revealed the predominance of viruses A(H3N2) in 1999-2000, the predominance of viruses A(h1N1) in 2000-2001, and the predominance of influenza B viruses in 2001-2002. According to the conducted antigenic analysis, all A(H1N1) isolates were similar to the etalon A/New Caledonia/20/99. The antigenic drift of hemagglutinin of A(H3N2) epidemic strains was oriented towards the etalons of A/Sydney/5/97--A/Moscow/10/99; while in influenza B viruses it was oriented towards the etalons B/Beejing/184/93--B/Yamanashi/166/98--B/Sichuan/379/99. Sequencing of hemagglutinin gene HA1 showed certain difference in the gene structure of epidemic strains A(H1N1) and A(H3N2) versus the etalon ones, which were registered, including at antigen sites. An analysis of paired sera obtained from patients confirmed the virologic findings, i.e. it detected a growth of antibodies to viruses that circulated during an actual season.     

Characterization of H2 influenza virus hemagglutinin with monoclonal antibodies: influence of receptor specificity

Antigenic analysis of human and avian H2 influenza viruses were done with monoclonal antibodies to the HA molecules in hemagglutination inhibition (HI) assays. These studies revealed that the receptor-binding specificity of the hemagglutinin can markedly influence the antigenic analysis obtained with monoclonal antibodies in HI tests. Influenza viruses that are sensitive or resistant to inhibition by horse serum inhibitors showed marked differences in their reactivity with monoclonal antibodies to the hemagglutinin. This was apparent with the A/RI/5+/57 and A/RI/5-/57 strains of H2N2 viruses isolated by Choppin and Tamm (1960a), half of the panel of different monoclonal antibodies failed to inhibit hemagglutination of the RI/5- variant, whereas all of the 18 monoclonal antibodies inhibited RI/5+. These findings have important implications in the antigenic analysis of influenza viruses where HI assays are conventionally used to determine the extent of antigenic drift in nature. Antigenic differences were detectable between different human H2 influenza virus isolates from 1957 that were sensitive to inhibition by horse serum, indicating that minor antigenic variation occurs within the first year of appearance of the new subtype. Minor antigenic variation continued in the H2 viruses until 1961, but by 1962 antigenically distinguishable variants that could be discriminated with both monoclonal antibodies and postinfection ferret antisera predominated. Analysis of avian H2 influenza viruses with a panel of monoclonal antibodies indicated that antigenic variation occurs and that multiple different variants cocirculate in the population. There was no progressive antigenic change in the avian H2 influenza viruses with time, as was found with the human H2N2 strains. Topographical mapping of the H2 hemagglutinin by selection of antigenic variants with monoclonal antibodies and analysis of their reactivity patterns by HI showed overlap between the epitopes examined. These results may reflect restriction in the antibody repertoire of the mice used in preparation of the monoclonal antibodies or that the H2 hemagglutinin does not have such discrete nonoverlapping antigenic regions found in the early H3 influenza virus.