Rapid replacement of human respiratory syncytial virus A with the ON1 genotype having 72 nucleotide duplication in G gene

Evolutionary trends of respiratory syncytial viruses: Insights from large-scale surveillance and molecular dynamics of G glycoprotein

Human respiratory syncytial virus (RSV) is an underlying cause of lower respiratory illnesses in children, elderly and immunocompromised adults. RSV contains multiple structural and non-structural proteins with two major glycoproteins that control the initial phase of infection, fusion glycoprotein and the attachment (G) glycoprotein. G protein attaches to the ciliated cells of airways initiating the infection. The hypervariable G protein plays a vital role in evolution of RSV strains. We employed multiple bioinformatics tools on systematically accessed large-scale data to evaluate mutations, evolutionary history, and phylodynamics of RSV. Mutational analysis of central conserved region (CCR) on G protein-coding sequences between 163 and 189 positions revealed frequent mutations at site 178 in human RSV (hRSV) A while arginine to glutamine substitutions at site 180 positions in hRSV B, remained prevalent from 2009 to 2014. Phylogenetic analysis indicates multiple signature mutations within G protein responsible for diversification of clades. The USA and China have highest number of surveillance records, followed by Kenya. Markov Chain Monte Carlo Bayesian skyline plot revealed that RSV A evolved steadily from 1990 to 2000, and rapidly between 2003 and 2005. Evolution of RSV B continued from 2003 to 2022, with a high evolution stage from 2016 to 2020. Throughout evolution, cysteine residues maintained their strict conserved states while CCR has an entropy value of 0.0039(±0.0005). This study concludes the notion that RSV G glycoprotein is continuously evolving while the CCR region of G protein maintains its conserved state providing an opportunity for CCR-specific monoclonal antibodys (mAbs) and inhibitors as potential candidates for immunoprophylaxis.

Molecular characterization of human respiratory syncytial virus in Seoul, South Korea, during 10 consecutive years, 2010-2019

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections and hospitalization in infants and young children. Here, we analyzed the genetic diversity of RSV using partial G gene sequences in 84 RSV-A and 78 RSV- B positive samples collected in Seoul, South Korea, for 10 consecutive years, from 2010 to 2019. Our phylogenetic analysis revealed that RSV-A strains were classified into either the ON1 (80.9%) or NA1 (19.0%) genotypes. On the other hand, RSV-B strains demonstrated diversified clusters within the BA genotype. Notably, some sequences designated as BA-SE, BA-SE1, and BA-DIS did not cluster with previously identified BA genotypes in the phylogenetic trees. Despite this, they did not meet the criteria for the assignment of a new genotype based on recent classification methods. Selection pressure analysis identified three positive selection sites (amino acid positions 273, 274, and 298) in RSV-A, and one possible positive selection site (amino acid position 296) in RSV-B, respectively. The mean evolutionary rates of Korean RSV-A from 1999 to 2019 and RSV-B strains from 1991 and 2019 were estimated at 3.51 × 10-3 nucleotides (nt) substitutions/site/year and 3.32 × 10-3 nt substitutions/site/year, respectively. The population dynamics in the Bayesian skyline plot revealed fluctuations corresponding to the emergence of dominant strains, including a switch of the dominant genotype from NA1 to ON1. Our study on time-scaled cumulative evolutionary analysis contributes to a better understanding of RSV epidemiology at the local level in South Korea.

Molecular epidemiology of respiratory syncytial virus in hospitalised children in Heidelberg, Southern Germany, 2014-2017

BACKGROUND

Respiratory syncytial virus (RSV) is the leading cause of hopitalisation in young children with respiratory tract infections (RTI). The aim of this research project was to analyse RSV genotypes and the diversification of RSV strains among hospitalised children in Heidelberg, Germany.

METHODS

We prospectively analysed nasopharyngeal swabs (NPS) from children who were hospitalised with acute RTI at the University Hospital Heidelberg, Germany, during winter seasons 2014 to 2017. RSV RT-PCR and RSV sequence analysis of the G gene coding for the attachment glycoprotein were performed. Clinical data was obtained using a standardised questionnaire.

RESULTS

RSV was detected in 405 out of 946 samples from hospitalised children. Most RSV positive children were below the age of two years (84.4%) and had a lower RTI (78.8%). The majority of RSV positive children was male, significantly younger than RSV negative children with a median age of 0.39 years and with more severe respiratory symptoms. Out of 405 positive samples, 317 RSV strains were successfully sub-grouped into RSV subtypes A (57.4%; 182/317) and B (42.6%; 135/317). Both RSV subtypes cocirculated in all analysed winter seasons. Phylogenetic analysis of 317 isolates revealed that the majority of RSV-A strains (180/182) belonged to the ON1 genotype, most RSV-B strains could be attributed to the BAIX genotype (132/135). ON1 and BAIX strains showed a sub-differentiation into different lineages and we were able to identify new (sub)genotypes.

CONCLUSION

Analysis of the molecular epidemiology of RSV from different seasons revealed the cocirculation and diversification of RSV genotypes ON1 and BAIX.

Predominance of ON1 and BA9 genotypes of respiratory syncytial virus (RSV) in Bulgaria, 2016-2018

The objectives of this study were to investigate the prevalence of respiratory syncytial virus (RSV) infections in Bulgaria, to characterize the genetic diversity of the RSV strains, and to perform amino acid sequence analysis of the RSV G protein. Clinical, epidemiological data and nasopharyngeal swabs were prospectively collected from children aged less than 5 years presenting with acute respiratory infections from October 2016 to September 2018. Real-time polymerase chain reaction for 12 respiratory viruses, and sequencing, phylogenetic, and amino acid analyses of the RSV G gene/protein were performed. Of the 875 children examined, 645 (73.7%) were positive for at least one viral respiratory pathogen. RSV was the most commonly detected virus (26.2%), followed by rhinoviruses (15%), influenza A (H3N2) (9.7%), adenoviruses (9%), bocaviruses (7.2%), human metapneumovirus (6.1%), parainfluenza viruses 1/2/3 (5.8%), influenza type B (5.5%), and A(H1N1)pdm09 (3.4%). The detection rate for RSV varied across two winter seasons (36.7% vs 20.3%). RSV-B cases outnumbered those of the RSV-A throughout the study period. RSV was the most common virus detected in patients with bronchiolitis (45.1%) and pneumonia (24%). Phylogenetic analysis indicated that all the sequenced RSV-A strains belonged to the ON1 genotype and the RSV-B strains were classified as BA9 genotype. Amino acid substitutions at 15 and 22 positions of the HVR-2 were identified compared with the ON1 and BA prototype strains, respectively. This study revealed the leading role of RSV as a causative agent of serious respiratory illnesses in early childhood, year-on-year fluctuations in RSV incidence, the dominance of RSV-B, and relatively low genetic diversity in the circulating RSV strains.

Circulating Respiratory Syncytial Virus Genotypes and Genetic Variability of the G Gene during 2017 and 2018/2019 Seasonal Epidemics Isolated from Children with Lower Respiratory Tract Infections in Daejeon, Korea

BACKGROUND

Respiratory syncytial virus (RSV) is a major pathogen causing respiratory tract infections in infants and young children. The aim of this study was to confirm the genetic evolution of RSV causing respiratory infections in children at Daejeon in Korea, through G gene analysis of RSV-A and RSV-B strains that were prevalent from 2017 to 2019.

METHODS

Pediatric patients admitted for lower respiratory tract infections at The Catholic University of Korea Daejeon St. Mary's Hospital in the 2017 and 2018/2019 RSV seasonal epidemics, who had RSV detected via multiplex polymerase chain reaction (PCR) were included. The nucleic acid containing RSV-RNA isolated from each of the patients' nasal discharge during standard multiplex PCR testing was stored. The G gene was sequenced and phylogenetic analysis was performed using MEGA X program and the genotype was confirmed.

RESULTS

A total of 155 specimens including 49 specimens from 2017 and 106 specimens from 2018-2019 were tested. The genotype was confirmed in 18 specimens (RSV-A:RSV-B = 4:14) from 2017 and 8 specimens (RSV-A:RSV-B = 7:1) from 2018/2019. In the phylogenetic analysis, all RSV-A type showed ON1 genotype and RSV-B showed BA9 genotype.

CONCLUSION

RSV-B belonging to BA9 in 2017, and RSV-A belonging to ON1 genotype in 2018/2019 was the most prevalent circulating genotypes during the two RSV seasons in Daejeon, Korea.

Dominance of the ON1 Genotype of RSV-A and BA9 Genotype of RSV-B in Respiratory Cases from Jeddah, Saudi Arabia

Human respiratory syncytial virus (HRSV) is a main cause of hospital admission for lower respiratory tract infection. In previous studies from Saudi Arabia, higher prevalence of the NA1 genotype in group A was observed from Riyadh and Taif. This study recruited respiratory cases from Jeddah during January to December, 2017. RSV represented 13.4% in the recruited cases with 64% of them belonging to group A and 36% to group B. All group A cases in this study were ON1 type characterized by duplication of 72 nucleotides, 24 amino acids in the C-terminal in the second hypervariable region of the G gene. In addition, for group B all of the cases were clustered under BA9, which had uniquely characterized as duplication of 60 nucleotides in the G protein. Our sequences showed similarity with earlier sequences from Saudi Arabia, Kuwait, Thailand, South Africa, Spain, the USA and Cyprus. Some amino acid substitutions in the investigated sequences would cause a change in potential O-glycosylation and N-glycosylation profiles from prototype ON1. The predominance of the ON1 and BA9 genotype of RSV-A in Jeddah compared to previous Saudi studies showing predominance of the NA1 genotype for group A. This difference in genotype prevalence could be due to fast spread of the ON1 genotype worldwide or due to the flux of travelers through Jeddah during hajj/umrah compared to Riyadh and Taif. This shift in genotype distribution requires continuous surveillance for genetic characterization of circulating respiratory infections including RSV. These findings may contribute to the understanding of RSV evolution and to the potential development of a vaccine against RSV.

Genetic characterization of G protein in respiratory syncytial virus ON-1 genotype in Tehran

Aim: We investigated the genetic characterization of the respiratory syncytial virus (RSV) ON-1 genotypes and their different lineages based on the G gene among children <2 years of age presenting with acute respiratory tract infections in Tehran, Iran. Materials & methods: A phylogenetic tree from the Iranian samples and ON-1 strains of various parts of the world were constructed. The amino acid composition of the RSV G protein of the ON-1 genotype was mapped. Results: Human RSV ON-1 genotypes from the Iranian samples clustered in three lineages. The most common amino acid substitutions were as follows: X218Q, I240S, L289P, Y304H and L310P. Conclusion: Continuing molecular epidemiological surveys in other regions of Iran will provide deeper insight into the nature of this replacement of the dominant RSV genotype from GA2 to ON-1 in Iran.

Respiratory syncytial virus in the Western Pacific Region: a systematic review and meta-analysis

Background

Respiratory syncytial virus (RSV) is the leading cause of viral pneumonia and bronchiolitis, especially in younger children. The burden of RSV infection in adults, particularly in the older age group, is increasingly recognised. However, RSV disease burden and molecular epidemiology in the World Health Organization (WHO) Western Pacific Region (WPR) has not been reviewed systematically. The aim of this systematic review is to investigate the epidemiological aspects of RSV (incidence, prevalence, seasonality and hospitalisation status) and the associated molecular data in the WPRO countries.

Methods

A systematic search was conducted in international literature databases (MEDLINE, EMBASE, Scopus and Web of Science) to identify RSV-related publications from January 2000 to October 2017 in the WPR countries.

Results

A total of 196 studies from 15 WPR countries were included. The positivity rate for RSV among respiratory tract infection patients was 16.73% (95% confidence interval (CI) = 15.12%-18.4%). The RSV-positive cases were mostly found in hospitalised compared with outpatients (18.28% vs 11.54%, P < 0.001), and children compared with adults (20.72% vs 1.87%, P < 0.001). The seasonality of RSV in the WPR countries follows the latitude, with the peak of RSV season occurring in the winter in temperate countries, and during the rainy season in tropical countries. The molecular epidemiology pattern of RSV in WPR countries was similar to the global pattern, with NA1 (RSV A) and BA (RSV B) being the predominant genotypes.

Conclusions

The available data on RSV are limited in several countries within the WPR, with most data focusing on children and hospitalised patients. Further studies and surveillance, incorporating laboratory testing, are needed to determine the burden of RSV infection in the WPR countries.

Molecular epidemiology of respiratory syncytial virus for 28 consecutive seasons (1990-2018) and genetic variability of the duplication region in the G gene of genotypes ON1 and BA in South Korea

We investigated the molecular epidemiology of respiratory syncytial virus (RSV) isolated from children during 28 consecutive seasons (1990-2018) and the genetic variability of the duplication region of RSV genotypes ON1 and BA in South Korea. RSV was identified using culture-based methods in Hep-2 cells and was grouped as RSV-A or RSV-B by an immunofluorescence assay. The second hypervariable region of the G gene was sequenced for genotyping. The nucleotide and deduced amino acid sequences of the duplication region of RSV ON1 and BA were analyzed. A total of 670 RSV-A and 233 RSV-B isolates were obtained. For RSV-A, the NA1 genotype predominated during the 2004/2005-2011/2012 seasons. The ON1 genotype was first detected in 2011 and has since replaced all other genotypes. For RSV-B, the GB3 genotype predominated during the 1999/2000-2005/2006 seasons, but the BA genotype also replaced all other genotypes of RSV-B after the first season in which it was isolated (2005/2006). In ON1 and BA genotype RSV strains, novel sequence types of the duplication region of the G gene were identified in 50-95% and 33-80% of the isolates, respectively, in each season. The ON1 and BA9 genotypes are responsible for the current epidemics of RSV infection in South Korea. The sequences in the duplication region of the G gene have evolved continuously and might be sufficient for the identification of specific strains of the RSV-A ON1 and RSV-B BA genotypes.

Preliminary functional and phylogeographic analyses of the 72 nucleotide duplication region in the emerging human respiratory syncytial virus ON1 strain attachment glycoprotein gene

The emerging human respiratory syncytial virus (hRSV) ON1 strain, which is characterized by a 72-nt duplication in the attachment glycoprotein (G) gene, has replaced other prevailing global genotypes since its discovery in 2012. In this study, we used the pseudotype lentiviral system to directly address the effect of the duplication on hRSV infection. In addition, representative 199 ON1 sequences selected from 2599 ON1 sequences that were downloaded from GenBank were used to perform Bayesian skyline and phylogeographic analyses. Our results showed that lentiviral pseudoparticles mimicked the key functions of the G-protein on hRSV cell entry. Further, we showed that deletion of the G-protein duplication decreased the efficiency of pLV infection. The mean substitution rate of the second mucin-like highly variable region for the ON1 G-protein gene was 2.14 × 10^-3 (95 % HPD: 1.23 × 10^-3, 3.08 × 10^-3) nucleotide substitutions per site per year. Phylogeographic analyses showed that the ON1 isolates might originate from Europe at the time of MRCA (i.e., the most recent common ancestors), which dated back to 1998.3 (95 % HPD: 1989.2, 2005.2). These preliminary findings revealed the enhanced attachment function of the duplication region in the ON1 G gene and highlighted the importance of ongoing surveillance of ON1 to better understand the molecular epidemiology of hRSV.

Respiratory syncytial virus A genotype classification based on systematic intergenotypic and intragenotypic sequence analysis

Respiratory syncytial virus (RSV), a leading cause of lower respiratory tract infections, is classified in two major groups (A and B) with multiple genotypes within them. Continuous changes in spatiotemporal distribution of RSV genotypes have been recorded since the identification of this virus. However, there are no established criteria for genotype definition, which affects the understanding of viral evolution, immunity, and development of vaccines. We conducted a phylogenetic analysis of 4,353 RSV-A G gene ectodomain sequences, and used 1,103 complete genome sequences to analyze the totallity of RSV-A genes. Intra- and intergenotype p-distance analysis and identification of molecular markers associated to specific genotypes were performed. Our results indicate that previously reported genotypes can be classified into nine distinct genotypes: GA1-GA7, SAA1, and NA1. We propose the analysis of the G gene ectodomain with a wide set of reference sequences of all genotypes for an accurate genotype identification.

The emergence of subgenotype ON-1 of Human orthopneumovirus type A in Riyadh, Saudi Arabia: A new episode of the virus epidemiological dynamic

Lower respiratory tract infections caused by Human orthopneumovirus are still a threat to the pediatric population worldwide. To date, the molecular epidemiology of the virus in Saudi Arabia has not been adequately charted. In this study, a total of 205 nasopharyngeal aspirate samples were collected from hospitalized children with lower respiratory tract symptoms during the winter seasons of 2014/15 and 2015/16. Human orthopneumovirus was detected in 89 (43.4%) samples, of which 56 (27.3%) were positive for type A and 33 (16.1%) were positive for type B viruses. The fragment that spans the two hypervariable regions (HVR1 and HVR2) of the G gene of Human orthopneumovirus A was amplified and sequenced. Sequence and phylogenetic analyses have revealed a genotype shift from NA1 to ON-1, which was prevalent during the winter seasons of 2007/08 and 2008/09. Based on the intergenotypic p-distance values, ON-1 was reclassified as a subgenotype of the most predominant genotype GA2. Three conserved N-glycosylation sites were observed in the HVR2 of Saudi ON-1 strains. The presence of a 23 amino acid duplicated region in ON-1 strains resulted in a higher number of O-glycosylation sites as compared to other genotypes. The data presented in this report outlined the replacement of NA1 and NA2 subgenotypes in Saudi Arabia with ON-1 within 7 to 8 years. The continuous evolution of Human orthopneumovirus through point mutations and nucleotide duplication may explain its ability to cause recurrent infections.

Epidemiology and genetic variability of respiratory syncytial virus in Portugal, 2014-2018

INTRODUCTION

Respiratory syncytial virus (RSV) is associated with substantial morbidity and mortality since it is a predominant viral agent causing respiratory tract infections in infants, young children and the elderly. Considering the availability of the RSV vaccines in the coming years, molecular understanding in RSV is necessary.

OBJECTIVE

The objective of the present study was to describe RSV epidemiology and genotype variability in Portugal during the 2014/15-2017/18 period.

MATERIAL AND METHODS

Epidemiological data and RSV-positive samples from patients with a respiratory infection were collected through the non-sentinel and sentinel influenza surveillance system (ISS). RSV detection, subtyping in A and B, and sequencing of the second hypervariable region (HVR2) of G gene were performed by molecular methods. Phylogenetic trees were generated using the Neighbor-Joining method and p-distance model on MEGA 7.0.

RESULTS

RSV prevalence varied between the sentinel (2.5%, 97/3891) and the non-sentinel ISS (20.7%, 3138/16779), being higher (P < 0.0001) among children aged <5 years. Bronchiolitis (62.9%, 183/291) and influenza-like illness (24.6%, 14/57) were associated (P < 0.0001) with RSV laboratory confirmation among children aged <6 months and adults ≥65 years, respectively. The HVR2 was sequenced for 562 samples. RSV-A (46.4%, 261/562) and RSV-B (53.6%, 301/562) strains clustered mainly to ON1 (89.2%, 233/261) and BA9 (92%, 277/301) genotypes, respectively, although NA1 and BA10 were also present until 2015/2016.

CONCLUSION

The sequence and phylogenetic analysis reflected the relatively high diversity of Portuguese RSV strains. BA9 and ON1 genotypes, which have been circulating in Portugal since 2010/2011 and 2011/2012 respectively, predominated during the whole study period.

Molecular epidemiology of human respiratory syncytial virus and human metapneumovirus in hospitalized children with acute respiratory infections in Croatia, 2014-2017

Acute respiratory infection (ARI) is the most common infection in children under 5 years of age and it is frequently caused by two pneumoviruses, human respiratory syncytial virus (HRSV) and human metapneumovirus (HMPV). Epidemic seasons of these viruses overlap and disease manifestations are highly similar, including severe lower ARI such as bronchiolitis or pneumonia. Reinfections with pneumoviruses are frequent and limited prevention treatment is available. Genetic diversity of HRSV and HMPV strains circulating in Croatia was monitored during four consecutive years (2014-2017). Co-circulation of multiple lineages was observed for both viruses. Within HRSV group A, ON1 strains gained strong predominance during the 4-year period, while previously dominant genotype NA1 was detected only sporadically. Similarly, newly occurring HMPV genotype A2c gained predominance over genotype A2b during this period, resulting in all infection in 2017 being caused by A2c. Along with phylogenetic analysis based on the commonly used fragments for detection and genotyping of these viruses, full length G and SH genes were also analysed. Evolutionary dynamics showed that inferred substitution rates of HRSV and HMPV are between 2.51 × 10^-3 and 3.61 × 10^-3 substitutions/site/year. This study established presence of recently described HMPV strains containing large duplications in the G gene in Croatia. Viruses with either of the two duplications belong to a subcluster A2c, which has completely replaced all other group A subclusters in 2017.

Spread and clinical severity of respiratory syncytial virus A genotype ON1 in Germany, 2011-2017

Background

The Respiratory Syncytial Virus (RSV) A genotype ON1, which was first detected in Ontario (Canada) in 2010/11, appeared in Germany in 2011/12. Preliminary observations suggested a higher clinical severity in children infected with this new genotype. We investigated spread and disease severity of RSV-A ON1 in pediatric in- and outpatient settings.

Methods

During 2010/11 to 2016/17, clinical characteristics and respiratory samples from children with acute respiratory tract infections (RTI) were obtained from ongoing surveillance studies in 33 pediatric practices (PP), one pediatric hospital ward (PW) and 23 pediatric intensive care units (PICU) in Germany. RSV was detected in the respiratory samples by PCR; genotypes were identified by sequencing. Within each setting, clinical severity markers were compared between RSV-A ON1 and RSV-A non-ON1 genotypes.

Results

A total of 603 children with RSV-RTI were included (132 children in PP, 288 in PW, and 183 in PICU). Of these children, 341 (56.6%) were infected with RSV-A, 235 (39.0%) with RSV-B, and one child (0.2%) with both RSV-A and RSV-B; in 26 (4.3%) children, the subtype could not be identified. In the 341 RSV-A positive samples, genotype ON1 was detected in 247 (72.4%), NA1 in 92 (26.9%), and GA5 in 2 children (0.6%). RSV-A ON1, rarely observed in 2011/12, was the predominant RSV-A genotype in all settings by 2012/13 and remained predominant until 2016/17. Children in PP or PW infected with RSV-A ON1 did not show a more severe clinical course of disease compared with RSV-A non-ON1 infections. In the PICU group, hospital stay was one day longer (median 8 days, inter-quartile range (IQR) 7–12 vs. 7 days, IQR 5–9; p = 0.02) and duration of oxygen treatment two days longer (median 6 days, IQR 4–9 vs. 4 days, IQR 2–6; p = 0.03) for children infected with RSV-A ON1.

Conclusions

In children, RSV-A ON1 largely replaced RSV-A non-ON1 genotypes within two seasons and remained the predominant RSV-A genotype in Germany during subsequent seasons. A higher clinical severity of RSV-A ON1 was observed within the group of children receiving PICU treatment, whereas in other settings clinical severity of RSV-A ON1 and non-ON1 genotypes was largely similar.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4266-y) contains supplementary material, which is available to authorized users.

Emergence of new antigenic epitopes in the glycoproteins of human respiratory syncytial virus collected from a US surveillance study, 2015-17

Respiratory syncytial virus (RSV) is a significant cause of lower respiratory tract infection in infants and elderly. To understand the evolution of neutralizing epitopes on the RSV glycoprotein (G) and fusion (F) proteins, we conducted a multi-year surveillance program (OUTSMART-RSV) in the US. Analysis of 1,146 RSV samples from 2015-2017 revealed a slight shift in prevalence from RSV A (58.7%) to B (53.7%) between the two seasons. RSV B was more prevalent in elderly (52.9% and 73.4%). Approximately 1% of the samples contained both RSV A and B viruses. All RSV A isolates were ON1 and almost all the B isolates were BA9 genotypes. Compared with the 2013 reference sequences, changes at the F antigenic sites of RSV B were greater than RSV A, which mainly occurred at antigenic sites V (L172Q/S173L at 99.6%), Ø (I206M/Q209K at 18.6%) and IV (E463D at 7%) of RSV B F. Sequence diversities in the G protein second hypervariable region were observed in the duplicated regions for RSV A and B, and at the G stop codon resulting in extension of 7 amino acids (22.1%) for RSV B in 2016-17. Thus, RSV surface glycoproteins are continuously evolving, and continued surveillance is important for the clinical evaluation of immunoprophylactic products.

[A molecular epidemiological study of respiratory syncytial virus circulating in southern Zhejiang Province, China, from 2009 to 2014]

OBJECTIVE

To find out the prevalence of respiratory syncytial virus (RSV) genotypes in southern Zhejiang Province, China, and to study the genetic characteristics of G protein from subtype A of RSV.

METHODS

The lower respiratory tract secretions of children under 5 years of age who were hospitalized for pneumonia and bronchiolitis in three hospitals in southern Zhejiang Province from July 2009 to June 2014 were collected. Direct immunofluorescence assay was used to detect RSV antigens from the collected secretions. A total of 200 samples were randomly selected from RSV-positive specimens in each prevailing year (from July of a specific year to June of the next year). RT-PCR was used to determine RSV subtypes, and the near-full length gene sequence of G protein from subtype A was amplified and sequenced to identify the genotype.

RESULTS

A total of 25 449 samples of lower respiratory tract secretions were collected from 2009 to 2014, among which 6 416 (25.21%) samples were RSV-positive. Among the 1 000 RSV-positive specimens randomly sampled, 462 strains (46.2%) were subtype A, and 538 strains (53.8%) were subtype B. Subtype A accounted for 22.5%, 74.5%, 84.5%, 19.0%, and 30.5% of the total strains in each year from 2009 to 2014. A total of 25 RSV subtype A strains were randomly sampled and sent out for bidirectional sequencing in each year, which confirmed 52 positive subtype A strains. Four genotypes of subtype A strains were obtained from the above strains, including NA1 (39 strains), NA4 (1 strain), ON1 (10 strains), and GA2 (2 strains). NA1 was the dominant genotype between 2009 and 2012, and ON1 was the only genotype of subtype A during 2013-2014. The nucleotide homology and amino acid homology between the G protein of subtype A and the prototype strain A2 were 80.7%-89.3% and 74.4%-82.6%, respectively. The nucleotide homology and amino acid homology between the isolates of subtype A were 81.5%-100% and 80.2%-100%, respectively.

CONCLUSIONS

In southern Zhejiang Province from 2009 to 2014, there was a co-circulation of RSV subtypes A and B, as well as a co-circulation of several different genotypes of RSV subtype A, which had highly variable G protein genes.

[A molecular epidemiological study of respiratory syncytial virus circulating in southern Zhejiang Province, China, from 2009 to 2014]

OBJECTIVE

To find out the prevalence of respiratory syncytial virus (RSV) genotypes in southern Zhejiang Province, China, and to study the genetic characteristics of G protein from subtype A of RSV.

METHODS

The lower respiratory tract secretions of children under 5 years of age who were hospitalized for pneumonia and bronchiolitis in three hospitals in southern Zhejiang Province from July 2009 to June 2014 were collected. Direct immunofluorescence assay was used to detect RSV antigens from the collected secretions. A total of 200 samples were randomly selected from RSV-positive specimens in each prevailing year (from July of a specific year to June of the next year). RT-PCR was used to determine RSV subtypes, and the near-full length gene sequence of G protein from subtype A was amplified and sequenced to identify the genotype.

RESULTS

A total of 25 449 samples of lower respiratory tract secretions were collected from 2009 to 2014, among which 6 416 (25.21%) samples were RSV-positive. Among the 1 000 RSV-positive specimens randomly sampled, 462 strains (46.2%) were subtype A, and 538 strains (53.8%) were subtype B. Subtype A accounted for 22.5%, 74.5%, 84.5%, 19.0%, and 30.5% of the total strains in each year from 2009 to 2014. A total of 25 RSV subtype A strains were randomly sampled and sent out for bidirectional sequencing in each year, which confirmed 52 positive subtype A strains. Four genotypes of subtype A strains were obtained from the above strains, including NA1 (39 strains), NA4 (1 strain), ON1 (10 strains), and GA2 (2 strains). NA1 was the dominant genotype between 2009 and 2012, and ON1 was the only genotype of subtype A during 2013-2014. The nucleotide homology and amino acid homology between the G protein of subtype A and the prototype strain A2 were 80.7%-89.3% and 74.4%-82.6%, respectively. The nucleotide homology and amino acid homology between the isolates of subtype A were 81.5%-100% and 80.2%-100%, respectively.

CONCLUSIONS

In southern Zhejiang Province from 2009 to 2014, there was a co-circulation of RSV subtypes A and B, as well as a co-circulation of several different genotypes of RSV subtype A, which had highly variable G protein genes.

BA9 lineage of respiratory syncytial virus from across the globe and its evolutionary dynamics

Respiratory syncytial virus (RSV) is an important pathogen of global significance. The BA9 is one of the most predominant lineages of the BA genotype of group B RSV that has acquired a 60bp duplication in its G protein gene. We describe the local and global evolutionary dynamics of the second hyper variable region in the C- terminal of the G protein gene of the BA9 lineage. A total of 418 sequences (including 31 study and 387 GenBank strains) from 29 different countries were used for phylogenetic analysis. This analysis showed that the study strains clustered with BA (BA9 and BA8) and SAB4 genotype of group B RSV. We performed time-scaled evolutionary clock analyses using Bayesian Markov chain Monte Carlo methods. We also carried out glycosylation, selection pressure, mutational, entropy and Network analyses of the BA9 lineage. The time to the most recent common ancestor (tMRCA) of the BA genotype and BA9 lineage were estimated to be the years 1995 (95% HPD; 1987–1997) and 2000 (95% HPD; 1998–2001), respectively. The nucleotide substitution rate of the BA genotype [(4.58×10⁻³ (95% HPD; 3.89–5.29×10⁻³) substitution/site/year] was slightly faster than the BA9 lineage [4.03×10⁻³ (95% HPD; 4.65–5.2492×10⁻³)]. The BA9 lineage was categorized into 3 sub lineages (I, II and III) based on the Bayesian and Network analyses. The local transmission pattern suggested that BA9 is the predominant lineage of BA viruses that has been circulating in India since 2002 though showing fluctuations in its effective population size. The BA9 lineage established its global distribution with report from 23 different countries over the past 16 years. The present study augments our understanding of RSV infection, its epidemiological dynamics warranting steps towards its overall global surveillance.

Spread and Evolution of Respiratory Syncytial Virus A Genotype ON1, Coastal Kenya, 2010-2015

In February 2012, the novel respiratory syncytial virus (RSV) group A, genotype ON1, was detected in Kilifi County, coastal Kenya. ON1 is characterized by a 72-nt duplication within the highly variable G gene (encoding the immunogenic attachment surface protein). Cases were diagnosed through surveillance of pneumonia in children at the county hospital. Analysis of epidemiologic, clinical, and sequence data of RSV-A viruses detected over 5 RSV seasons (2010/2011 to 2014/2015) indicated the following: 1) replacement of previously circulating genotype GA2 ON1, 2) an abrupt expansion in the number of ON1 variants detected in the 2014/2015 epidemic, 3) recently accumulation of amino acid substitutions within the ON1 duplicated sequence, and 4) no clear evidence of altered pathogenicity relative to GA2. The study demonstrates the public health importance of molecular surveillance in defining the spread, clinical effects, and evolution of novel respiratory virus variants.

Molecular epidemiology of human respiratory syncytial virus among children in Japan during three seasons and hospitalization risk of genotype ON1

We investigated the genetic diversity, the circulation patterns, and risk for hospital admission of human respiratory syncytial virus (HRSV) strains in Japan between 2012 through 2015. During the study period, 744 HRSV-positive cases were identified by rapid diagnostic test. Of these, 572 samples were positive by real-time PCR; 400 (69.9%) were HRSV-A, and 172 (30.1%) were HRSV-B. HRSV-A and -B alternated as the dominant strain in the subsequent seasons. Phylogenetic tree analysis of the second hyper-variable region of the G protein classified the HRSV-A specimens into NA1 (n = 242) and ON1 (n = 114) genotypes and the HRSV-B specimens into BA9 (n = 60), and BA10 (n = 27). The ON1 genotype, containing a 72-nucleotide duplication in the G protein’s second hyper-variable region, was first detected in the 2012–2013 season but it predominated and replaced the older NA1 HRSV-A in the 2014–2015 season, which also coincided with a record number of HRSV cases reported to the National Infectious Disease Surveillance in Japan. The risk of hospitalization was 6.9 times higher for the ON1 genotype compared to NA1. In conclusion, our data showed that the emergence and predominance of the relatively new ON1 genotype in Japan was associated with a record high number of cases and increased risk for hospitalization.

Genetic diversity of human respiratory syncytial virus circulating among children in Ibadan, Nigeria

Human respiratory syncytial virus (HRSV) is the most common viral cause of acute lower respiratory tract infections (LRTIs) in infants and young children however, without an effective vaccine licensed for human use till date. Information on the circulating genotypes of HRSV from regions with high-burden of infection is vital in the global efforts towards the development of protective vaccine. We report here the genotypes of HRSV circulating among children in Ibadan, the first of such from Nigeria.Nasopharyngeal and oropharyngeal swabs collected from 231 children presenting with respiratory infections in some health facilities for care as well as those attending immunization centers for routine vaccination in Ibadan, Nigeria were used for the study. The 2^nd hypervariable (HVR2) region of the glycoprotein (G) gene of HRSV was amplified and sequenced using HRSV group specific primers. HRSV was detected in 41 out of the 231 samples. Thirty-three of the isolates were successfully subtyped(22 subtype A and 11 subtype B). Fourteen of the subtype A and all the subtype B were successfully sequenced and genotyped. Phylogenetic analysis showed that genotype ON1 with 72 nucleotide (nt) duplication was the major subgroup A virus (11 of 14) detected together with genotype NA2. All the HRSV subtype B detected belong to the BA genotype with characteristic 60nt duplication. The ON1 genotypes vary considerably from the prototype strain due to amino acid substitutions including T292I which has not been reported elsewhere. The NA2 genotypes have mutations on four antigenic sites within the HVR2relative to the prototype A2. In conclusion, three genotypes of HRSV were found circulating in Ibadan, Nigeria. Additional study that will include isolates from other parts of the country will be done to determine the extent of genotype diversity of HRSV circulating in Nigeria.

Genetic variability human respiratory syncytial virus subgroups A and B in Turkey during six successive epidemic seasons, 2009-2015

Human respiratory syncytial virus (HRSV) is most important viral respiratory pathogen of acute lower respiratory tract infections in infants and young children worldwide. The circulating pattern and genetic characteristics in the HRSV attachment glycoprotein gene were investigated in Turkey during six consecutive seasons from 2009 to 2015. HRSVA was dominant in the all epidemic seasons except 2011‐2012 season. Partial sequences of the HVR2 region of the G gene of 479 HRSVA and 135 HRSVB were obtained. Most Turkish strains belonged to NA1, ON1, and BA9, which were the predominant genotypes circulating worldwide. Although three novel genotypes, TR‐A, TR‐BA1, and TR‐BA2, were identified, they were not predominant. Clinical data were available for 69 HRSV‐positive patients who were monitored due to acute lower respiratory tract illness. There were no significant differences in the clinical diagnosis, hospitalization rates, laboratory findings and treatment observed between the HRSVA and HRSVB groups, and co‐infections in this study. The major population afflicted by HRSV infections included infants and children between 13 and 24 months of age. We detected that the CB1, GB5, and THB strains clustered in the same branch with a bootstrap value of 100%. CB‐B and BA12 strains clustered in the same branch with a bootstrap value of 65%. The BA11 genotype was clustered in the BA9 genotype in our study. The present study may contribute on the molecular epidemiology of HRSV in Turkey and provide data for HRSV strains circulating in local communities and other regions worldwide.

Respiratory syncytial virus genotypes NA1, ON1, and BA9 are prevalent in Thailand, 2012-2015

Respiratory syncytial virus (RSV) causes acute lower respiratory tract infection in infants and young children worldwide. To investigate the RSV burden in Thailand over four consecutive years (January 2012 to December 2015), we screened 3,306 samples obtained from children ≤5 years old with acute respiratory tract infection using semi-nested reverse-transcription polymerase chain reaction (RT-PCR). In all, 8.4% (277/3,306) of the specimens tested positive for RSV, most of which appeared in the rainy months of July to November. We then genotyped RSV by sequencing the G glycoprotein gene and performed phylogenetic analysis to determine the RSV antigenic subgroup. The majority (57.4%, 159/277) of the RSV belonged to subgroup A (RSV-A), of which NA1 genotype was the most common in 2012 while ON1 genotype became prevalent the following year. Among samples tested positive for RSV-B subgroup B (RSV-B) (42.6%, 118/277), most were genotype BA9 (92.6%, 87/94) with some BA10 and BA-C. Predicted amino acid sequence from the partial G region showed highly conserved N-linked glycosylation site at residue N237 among all RSV-A ON1 strains (68/68), and at residues N296 (86/87) and N310 (87/87) among RSV-B BA9 strains. Positive selection of key residues combined with notable sequence variations on the G gene contributed to the continued circulation of this rapidly evolving virus.

Molecular and clinical characterization of human respiratory syncytial virus in South Korea between 2009 and 2014

Respiratory syncytial virus (RSV) can cause serious respiratory infections, second only to influenza virus. In order to know RSV's genetic changes we examined 4028 respiratory specimens from local hospital outpatients in Gyeonggi Province, South Korea over six consecutive years by real-time one-step RT-PCR; 183 patients were positive for RSV infection. To investigate the specific distribution of RSV genotypes, we performed partial sequencing of the glycoprotein gene. Of the 131 RSV-A specimens sequenced, 61 (43·3%) belonged to the ON1 genotype, 66 (46·8%) were NA1 genotype, 3 (2·1%) were GA5 genotype, and 1 (0·7%) belonged to the GA1 genotype. Of the 31 RSV-B specimens sequenced, 29 were BA9 genotype (87·9%) and 2 were BA10 genotype (6·1%). The most common clinical symptoms were fever, cough, nasal discharge, and phlegm; multiple logistic regression analysis showed that RSV-positive infection on pediatric patients was strongly associated with cough (OR = 2·8, 95% CI 1·6-5·1) and wheezing (OR = 2·8, 95% CI 1·7-4·4). The ON1 genotype was significantly associated with phlegm (OR = 11·8, 95% CI 3·8-46·7), while the NA1 genotype was associated with the pediatric patients' gender (males, OR = 2·4, 95% CI 1·1-5·4) and presence of chills (OR = 5·1, 95% CI 1·1-27·2). RSV subgroup B was showed association with nasal obstruction (OR = 4·6, 95% CI 1·2-20·0). The majority of respiratory virus coinfections with RSV were human rhinovirus (47·2%). This study contributes to our understanding of the molecular epidemiological characteristics of RSV, which promotes the potential for improving RSV vaccines.

Prevalence and genetic characterisation of respiratory syncytial viruses circulating in Bulgaria during the 2014/15 and 2015/16 winter seasons

The respiratory syncytial virus (RSV) is a leading cause of acute respiratory illnesses (ARI) in infants and young children. The objectives of this study were to investigate the RSV circulation among children aged <5 years in Bulgaria, to identify the RSV-A and RSV-B genotypes and to perform an amino acid sequence analysis of second hypervariable region (HVR2) of the G gene. During the 2014/15 and 2015/16 winter seasons, nasopharyngeal specimens of 610 children aged <5 years with ARI were tested using Real Time RT-PCR for influenza viruses, RSV, metapneumovirus, parainfluenza viruses, rhinoviruses and adenoviruses. Viral respiratory pathogens were detected in 429 (70%) out of 610 patients examined and RSV was the most frequently identified virus (26%) followed by influenza A(H1N1)pdm09 virus (14%) (p < .05). RSV was the most prevalent pathogen in patients with bronchiolitis (48%) and pneumonia (38%). In the 2014/15 season, RSV-A dominated slightly (53%), while in the next season RSV-B viruses prevailed more strongly (66%). The phylogenetic analysis based on the G gene indicated that all 21 studied RSV-A strains belonged to the ON1 genotype; the vast majority (96%) of the RSV-B strains were classified into BA9 genotype and only one - into BA10 genotype. All Bulgarian RSV-A and RSV-B sequences contained a 72-nt and a 60-nt duplication in the HVR2, respectively. The study showed the leading role of this pathogen as a causative agent of serious respiratory illnesses in early childhood, year-on-year fluctuations in RSV incidence, a shift from RSV-A to RSV-B subgroup dominance and relatively low genetic divergence in the circulating strains.

Molecular characterization and clinical epidemiology of human respiratory syncytial virus (HRSV) A and B in hospitalized children, Southern Brazil

Human respiratory syncytial virus (HRSV) is a major etiologic agent of pediatric respiratory infections. Genetic variability of its glycoprotein G enables HRSV to evade the immune response and determines its seasonal dissemination. This study reports genetic variability and clinical profiles of HRSV-infected patients from Southern Brazil. Seventy positive samples, 78% type A and 22% type B, were analyzed. Of the patients (median age, 6 months; interquartile range, 2-11 years), 16% had co-morbidities and 17% developed severe disease. The ON1 HRSV genotype first appeared in 2012, and patients infected with this genotype showed an increased tendency to develop severe disease.

Co-Circulation of 72bp Duplication Group A and 60bp Duplication Group B Respiratory Syncytial Virus (RSV) Strains in Riyadh, Saudi Arabia during 2014

Respiratory syncytial virus (RSV) is an important viral pathogen of acute respiratory tract infection (ARI). Limited data are available on molecular epidemiology of RSV from Saudi Arabia. A total of 130 nasopharyngeal aspirates were collected from children less than 5 years of age with ARI symptoms attending the Emergency Department at King Khalid University Hospital and King Fahad Medical City, Riyadh, Saudi Arabia between October and December, 2014. RSV was identified in the 26% of the hospitalized children by reverse transcriptase PCR. Group A RSV (77%) predominated during the study as compared to group B RSV (23%). The phylogenetic analysis of 28 study strains clustered group A RSV in NA1 and ON1 genotypes and group B viruses in BA (BA9) genotype. Interestingly, 26% of the positive samples clustered in genotypes with duplication in the G protein gene (ON1 for group A and BA for group B). Both the genotypes showed enhanced O-linked glycosylation in the duplicated region, with 10 and 2 additional sites in ON1 and BA respectively. Selection pressure analysis revealed purifying selection in both the ON1 and BA genotypes. One codon each in the ON1 (position 274) and BA genotypes (position 219) were positively selected and had high entropy values indicating variations at these amino acid positions. This is the first report describing the presence of ON1 genotype and the first report on co-circulation of two different genotypes of RSV with duplication in the G protein gene from Saudi Arabia. The clinical implications of the simultaneous occurrence of genotypes with duplication in G protein gene in a given population especially in the concurrent infections should be investigated in future. Further, the ongoing surveillance of RSV in this region will reveal the evolutionary trajectory of these two genotypes with duplication in G protein gene from largest country in the Middle East.

Molecular evolution of respiratory syncytial virus subgroup A genotype NA1 and ON1 attachment glycoprotein (G) gene in central Vietnam

We performed molecular evolutionary analyses of the G gene C-terminal 3rd hypervariable region of RSV-A genotypes NA1 and ON1 strains from the paediatric acute respiratory infection patients in central Vietnam during the 2010-2012 study period. Time-scaled phylogenetic analyses were performed using Bayesian Markov Chain Monte Carlo (MCMC) method, and pairwise distances (p-distances) were calculated. Bayesian Skyline Plot (BSP) was constructed to analyze the time-trend relative genetic diversity of central Vietnam RSV-A strains. We also estimated the N-glycosylation sites within G gene hypervariable region. Amino acid substitutions under positive and negative selection pressure were examined using Conservative Single Likelihood Ancestor Counting (SLAC), Fixed Effects Likelihood (FEL), Internal Fixed Effects Likelihood (IFEL) and Mixed Effects Model for Episodic Diversifying Selection (MEME) models. The majority of central Vietnam ON1 strains detected in 2012 were classified into lineage 1 with few positively selected substitutions. As for the Vietnamese NA1 strains, four lineages were circulating during the study period with a few positive selection sites. Shifting patterns of the predominantly circulating NA1 lineage were observed in each year during the investigation period. Median p-distance of central Vietnam NA1 strains was wider (p-distance=0.028) than that of ON1 (p-distance=0.012). The molecular evolutionary rate of central Vietnam ON1 strains was estimated to be 2.55×10^-2 (substitutions/site/year) and was faster than NA1 (7.12×10^-3 (substitutions/site/year)). Interestingly, the evolutionary rates of both genotypes ON1 and NA1 strains from central Vietnam were faster than the global strains respectively. Furthermore, the shifts of N-glycosylation pattern within the G gene 3rd hypervariable region of Vietnamese NA1 strains were observed in each year. BSP analysis indicated the rapid growth of RSV-A effective population size in early 2012. These results suggested that the molecular evolution of RSV-A G gene detected in central Vietnam was fast with unique evolutionary dynamics.

Prevailing genotype distribution and characteristics of human respiratory syncytial virus in northeastern China

Although human respiratory syncytial virus (RSV) is one of the most common viruses inducing respiratory tract infections in young children and the elderly, the genotype distribution and characteristics of RSV in northeastern China have not been investigated. Here, we identified 25 RSV‐A and 8 RSV‐B strains from 80 samples of patients with respiratory infections between February 2015 and May 2015. All 25 RSV‐A viruses were classified as the ON1 genotype, which rapidly spread and became the dominant genotype in the world since being identified in Ontario (Canada) in December 2010. All eight RSV‐B viruses belonged to the BA genotype with a 60‐nucleotide duplication, seven of which formed two new genotypes, BA‐CCA and BA‐CCB. The remaining RSV‐B virus clustered with one of the Hangzhou strains belonging to genotype BA11. Construction of a phylogenetic tree and amino acid substitution analysis showed that Changchun ON1 viruses exclusively constituted Lineages 3, 5 and 6, and contained several unique and newly identified amino acid substitutions, including E224G, R244K, L289I, Y297H, and L298P. Selective pressure was also evaluated, and various N and O‐glycosylation sites were predicted. This study provides the first genetic analysis of RSV in northeastern China and may facilitate a better understanding of the evolution of this virus locally and globally. J. Med. Virol. 89:222–233, 2017. © 2016 The Authors. Journal of Medical Virology Published by Wiley Periodicals, Inc.

Molecular evolution of the capsid gene in human norovirus genogroup II

Capsid protein of norovirus genogroup II (GII) plays crucial roles in host infection. Although studies on capsid gene evolution have been conducted for a few genotypes of norovirus, the molecular evolution of norovirus GII is not well understood. Here we report the molecular evolution of all GII genotypes, using various bioinformatics techniques. The time-scaled phylogenetic tree showed that the present GII strains diverged from GIV around 1630CE at a high evolutionary rate (around 10(-3) substitutions/site/year), resulting in three lineages. The GII capsid gene had large pairwise distances (maximum > 0.39). The effective population sizes of the present GII strains were large (>10(2)) for about 400 years. Positive (20) and negative (over 450) selection sites were estimated. Moreover, some linear and conformational B-cell epitopes were found in the deduced GII capsid protein. These results suggested that norovirus GII strains rapidly evolved with high divergence and adaptation to humans.

Respiratory syncytial virus subtype ON1/NA1/BA9 predominates in hospitalized children with lower respiratory tract infections

Respiratory syncytial virus (RSV) infection is the leading cause of acute respiratory tract disease in children less than 5 years old. The aim of this study was to further elucidate the molecular properties and clinical characteristics of RSV infection. The study sample included 238 patients <5 years old who were hospitalized with clinical symptoms of upper or lower respiratory tract infection (URTI or LRTI) in the Pediatric Department at the First People's Hospital of Chenzhou, South China in 2014. We subjected nasopharyngeal aspirate (NPA) or nasal swab (NS) samples from the patients to indirect fluorescence assay screens. RSV G genes were amplified by reverse transcription‐PCR (RT‐PCR) and sequenced. Of the 238 patients screened, 64 (26.8%) were confirmed to have RSV infections. Of those 64 confirmed RSV infection cases, 39 (60.9%) had subtype BA9, 13 (20.3%) had the recently identified subtype ON1, 11 (17.2%) had subtype NA1, and 1 (1.6%) had subtype GB2. The predominant presentation was LRTI with coughing, sputum production, fever, and wheezing. RSV subtype NA1 and BA9 infections were found mostly in infants, whereas the age distribution of subtype ON1 infections was more uniform across the age bands. Phylogenetic analysis indicated that, compared with the prototype strain A2, all ON1 and most NA1 isolates had lost one potential N‐glycosylation site at amino acid 251 and 249 due to T251K and N249Y substitution, respectively. These findings suggest that NA1, BA9, and ON1 are the dominant RSV subtypes causing respiratory tract infections in young children presenting to the hospital in South China. J. Med. Virol. 89:213–221, 2017. © 2016 Wiley Periodicals, Inc.

A molecular epidemiological study of human respiratory syncytial virus in Croatia, 2011-2014

Human respiratory syncytial virus (HRSV) causes common respiratory tract infections in infants, young children and the elderly. The diversity of HRSV strains circulating in Croatia was investigated throughout a period of four consecutive years from March 2011-March 2014. The analysis was based on sequences from the second hypervariable region of the G gene. A predominance of HRSV group A was observed in the first three years of the study, while group B became slightly predominant during the first few months of 2014. Overall, 76% of viruses belonged to group A including the genotypes NA1, ON1 and GA5. NA1 was by far the most common genotype within group A in 2011-2013; however, only ON1 and a few GA5 viruses were detected in the first three months of 2014. The majority of group B strains were of genotype BA9 (97%), and a few BA10 genotypes were detected. BA9 had the highest substitution rate of all the detected genotypes, followed by ON1. Multiple analyses showed that HRSV group A strains were more diverse than group B strains. Gly at residue 232 (previously described to be specific for ON1) was also detected in three NA1 strains, which were phylogenetically placed on separate branches within the NA1 genotype. For all genotypes, the diversity was higher at the amino acid level than at the nucleotide level, although positive selection of mutations was shown for only a few sites using four different methods of codon-based analysis of selective pressure. More codons were predicted to be negatively selected. The complexity of the HRSV pools present during each epidemic peak was determined and compared to previous epidemiological data. In addition to presenting genetic versatility of HRSV in this geographic region, the collected sequences provide data for further geographical and temporal comparative analyses of HRSV and its evolutionary pathways.

Sixteen years of evolution of human respiratory syncytial virus subgroup A in Buenos Aires, Argentina: GA2 the prevalent genotype through the years

Human respiratory syncytial virus (HRSV) is the main viral cause of acute lower respiratory tract infections (LRTI) in children worldwide. In recent years, several preclinical trials with vaccine candidates have been reported. It is in this sense that molecular epidemiological studies become important. Understanding viral dispersion patterns before and after the implementation of a vaccine can provide insight into the effectiveness of the control strategies. In this work we analyzed the molecular epidemiology of HRSV-A over a period of sixteen years (1999-2014) in Buenos Aires. By bioinformatic tools we analyzed 169 sequences of the G glycoprotein gene from hospitalized pediatric patients with LRTI. We found that GA2 was the most prevalent genotype (73.35%). GA5 genotype co-circulated in our region until 2009 when it was no longer detected, except in 2011. The recently globally emerging ON1 lineage with a 72-nt duplication increased its frequency to become the only lineage detected in Buenos Aires in 2014. By discrete phylogeographic analysis of global ON1 strains we could determine that Panama could be the location of the MRCA dated June 20, 2010; and this lineage could be introduced in Argentina from Spain in April 2011. This analysis also showed temporary and geographical clustering of ON1 strains observed as phylogenetic clades with strains exclusively associated from a single country, nevertheless among our 44 ON1 strains from three outbreaks (2012-2014) we could also detect posterior reintroductions and circulation from United States, Cuba, South Korea, and Spain. The continuous phylogeographic analysis of one sublineage of Argentine ON1 strains allowed us to establish that there could be a local clustering of some strains even in neighborhoods. This work shows the potential of this type of bioinformatic tools in the context of a future vaccine surveillance network to trace the spread of new genetic lineages in human populations.

Molecular Characterization of Human Respiratory Syncytial Virus in the Philippines, 2012-2013

Human respiratory syncytial virus (HRSV) is a major cause of acute lower respiratory tract infections in infants and children worldwide. We performed molecular analysis of HRSV among infants and children with clinical diagnosis of severe pneumonia in four study sites in the Philippines, including Biliran, Leyte, Palawan, and Metro Manila from June 2012 to July 2013. Nasopharyngeal swabs were collected and screened for HRSV using real-time polymerase chain reaction (PCR). Positive samples were tested by conventional PCR and sequenced for the second hypervariable region (2^nd HVR) of the G gene. Among a total of 1,505 samples, 423 samples were positive for HRSV (28.1%), of which 305 (72.1%) and 118 (27.9%) were identified as HRSV-A and HRSV-B, respectively. Two genotypes of HRSV-A, NA1 and ON1, were identified during the study period. The novel ON1 genotype with a 72-nucleotide duplication in 2^nd HVR of the G gene increased rapidly and finally became the predominant genotype in 2013 with an evolutionary rate higher than the NA1 genotype. Moreover, in the ON1 genotype, we found positive selection at amino acid position 274 (p<0.05) and massive O- and N-glycosylation in the 2^nd HVR of the G gene. Among HRSV-B, BA9 was the predominant genotype circulating in the Philippines. However, two sporadic cases of GB2 genotype were found, which might share a common ancestor with other Asian strains. These findings suggest that HRSV is an important cause of severe acute respiratory infection among children in the Philippines and revealed the emergence and subsequent predominance of the ON1 genotype and the sporadic detection of the GB2 genotype. Both genotypes were detected for the first time in the Philippines.

Genetic diversity and evolutionary insights of respiratory syncytial virus A ON1 genotype: global and local transmission dynamics

Human respiratory syncytial virus (RSV) A ON1 genotype, first detected in 2010 in Ontario, Canada, has been documented in 21 countries to date. This study investigated persistence and transmission dynamics of ON1 by grouping 406 randomly selected RSV-positive specimens submitted to Public Health Ontario from August 2011 to August 2012; RSV-A-positive specimens were genotyped. We identified 370 RSV-A (181 NA1, 135 NA2, 51 ON1 3 GA5) and 36 RSV-B positive specimens. We aligned time-stamped second hypervariable region (330 bp) of G-gene sequence data (global, n = 483; and Ontario, n = 60) to evaluate transmission dynamics. Global data suggests that the most recent common ancestor of ON1 emerged during the 2008–2009 season. Mean evolutionary rate of the global ON1 was 4.10 × 10⁻³ substitutions/site/year (95% BCI 3.1–5.0 × 10⁻³), not significantly different to that of Ontario ON1. The estimated mean reproductive number (R₀ = ∼ 1.01) from global and Ontario sequences showed no significant difference and implies stability among global RSV-A ON1. This study suggests that local epidemics exhibit similar underlying evolutionary and epidemiological dynamics to that of the persistent global RSV-A ON1 population. These findings underscore the importance of continual molecular surveillance of RSV in order to gain a better understanding of epidemics.

Molecular evolution of the hypervariable region of the attachment glycoprotein gene in human respiratory syncytial virus subgroup B genotypes BA9 and BA10

We studied the molecular evolution of the C-terminal 3rd hypervariable region in the attachment glycoprotein gene of human respiratory syncytial virus subgroup B (HRSV-B) genotypes BA9 and BA10. We performed time-scaled phylogenetic analyses using Bayesian Markov chain Monte Carlo methods. We also performed a genetic distance analysis (p-distance analysis), positive and negative selection analyses, and a Bayesian skyline plot (BSP) analysis. We found that genotype BA9 diverged from the common ancestor of genotypes BA7, BA8, and BA10, while genotype BA10 diverged from the ancestor of genotypes BA7 and BA8. Strains of both genotypes were distributed worldwide. BA9 and BA10 diverged between 1999 and 2001. Both BA9 and BA10 evolved rapidly (about 4.8×10(-3)substitutions/site/year) and formed three distinct lineages in a 10-year period. BA10 strains belonging to lineage 3 had large genetic distances (p-distance>0.07). Thus, it may be possible to classify these strains as a new genotype, BA11. No positive selection site was detected in either genotype. Phylodynamic analyses showed that the effective population size of BA10 decreased gradually since 2010 and BA9 slightly decreased since 2009. The results suggested that the recently prevalent HRSV-B genotypes BA9 and BA10 evolved uniquely, leading to epidemics of HRSV-B worldwide over a 15-year period.

Molecular Evolution of the Capsid Gene in Norovirus Genogroup I

We studied the molecular evolution of the capsid gene in all genotypes (genotypes 1–9) of human norovirus (NoV) genogroup I. The evolutionary time scale and rate were estimated by the Bayesian Markov chain Monte Carlo (MCMC) method. We also performed selective pressure analysis and B-cell linear epitope prediction in the deduced NoV GI capsid protein. Furthermore, we analysed the effective population size of the virus using Bayesian skyline plot (BSP) analysis. A phylogenetic tree by MCMC showed that NoV GI diverged from the common ancestor of NoV GII, GIII, and GIV approximately 2,800 years ago with rapid evolution (about 10⁻³ substitutions/site/year). Some positive selection sites and over 400 negative selection sites were estimated in the deduced capsid protein. Many epitopes were estimated in the deduced virus capsid proteins. An epitope of GI.1 may be associated with histo-blood group antigen binding sites (Ser377, Pro378, and Ser380). Moreover, BSP suggested that the adaptation of NoV GI strains to humans was affected by natural selection. The results suggested that NoV GI strains evolved rapidly and date back to many years ago. Additionally, the virus may have undergone locally affected natural selection in the host resulting in its adaptation to humans.

Conservation of G-Protein Epitopes in Respiratory Syncytial Virus (Group A) Despite Broad Genetic Diversity: Is Antibody Selection Involved in Virus Evolution?

Worldwide G-glycoprotein phylogeny of human respiratory syncytial virus (hRSV) group A sequences revealed diversification in major clades and genotypes over more than 50 years of recorded history. Multiple genotypes cocirculated during prolonged periods of time, but recent dominance of the GA2 genotype was noticed in several studies, and it is highlighted here with sequences from viruses circulating recently in Spain and Panama. Reactivity of group A viruses with monoclonal antibodies (MAbs) that recognize strain-variable epitopes of the G glycoprotein failed to correlate genotype diversification with antibody reactivity. Additionally, no clear correlation was found between changes in strain-variable epitopes and predicted sites of positive selection, despite both traits being associated with the C-terminal third of the G glycoprotein. Hence, our data do not lend support to the proposed antibody-driven selection of variants as a major determinant of hRSV evolution. Other alternative mechanisms are considered to account for the high degree of hRSV G-protein variability.

IMPORTANCE

An unusual characteristic of the G glycoprotein of human respiratory syncytial virus (hRSV) is the accumulation of nonsynonymous (N) changes at higher rates than synonymous (S) changes, reaching dN/dS values at certain sites predictive of positive selection. Since these sites cluster preferentially in the C-terminal third of the G protein, like certain epitopes recognized by murine antibodies, it was proposed that immune (antibody) selection might be driving the apparent positive selection, analogous to the antigenic drift observed in the influenza virus hemagglutinin (HA). However, careful antigenic and genetic comparison of the G glycoprotein does not provide evidence of antigenic drift in the G molecule, in agreement with recently published data which did not indicate antigenic drift in the G protein with human sera. Alternative explanations to the immune-driven selection hypothesis are offered to account for the high level of G-protein genetic diversity highlighted in this study.

Early Evolution of Human Respiratory Syncytial Virus ON1 Strains: Analysis of the Diversity in the C-Terminal Hypervariable Region of Glycoprotein Gene within the First 3.5 Years since Their Detection

OBJECTIVE

Characterization of the phylogeny and diversity of human respiratory syncytial virus (HRSV) genotype ON1 that occurred during its early evolution (within the first 3.5 years since the detection of the first ON1 strains). ON1 strains have a 72-nucleotide-long in-frame duplication within the second hypervariable domain of the glycoprotein gene (HVR2).

METHODS

All available HVR2 sequences of strains belonging to the ON1 genotype published prior to June 20, 2014 were collected. Multiple sequence alignments, phylogeny, phylogeography, sequence clustering and putative protein analyses were performed.

RESULTS

The worldwide spread and diversification of ON1 strains are presented. Only in a minority of ON1 strains do the two replicas remain identical, and various ON1 strains possess common differences between the first and the second copy (segments A and B). Mutations of the progenitor sequence were more frequent in segment B, a higher overall diversity on the protein level and more putative glycosylation sites exist in segment B, and, unlike in segment A, positive selection acts on that protein region.

CONCLUSIONS

The fast spread of the novel HRSV genotype ON1 has been accompanied by its rapid concurrent diversification. Differences in variability of the two replicas within HVR2 were detected, with C-terminal replica being more variable.

Characteristics and Their Clinical Relevance of Respiratory Syncytial Virus Types and Genotypes Circulating in Northern Italy in Five Consecutive Winter Seasons

In order to investigate the genetic diversity and patterns of the co-circulating genotypes of respiratory syncytial virus (RSV) and their possible relationships with the severity of RSV infection, we studied all of the RSV-positive nasopharyngeal samples collected from children during five consecutive winters (2009–2010, 2010–2011, 2011–2012, 2012–2013 and 2013–2014). The RSVs were detected using the respiratory virus panel fast assay and single-tube RT-PCR, their nucleotides were sequenced, and they were tested for positive selection. Of the 165 positive samples, 131 (79.4%) carried RSV-A and 34 (20.6%) RSV-B; both groups co-circulated in all of the study periods, with RSV-A predominating in all the seasons except for winter 2010–2011, which had a predominance of RSV-B. Phylogenetic analysis of the RSV-A sequences identified genotypes NA1 and ON1, the second replacing the first during the last two years of the study period. The RSV-B belonged to genotypes BA9 and BA10. BA9 was detected in all the years of the study whereas BA only desultorily. Comparison of the subjects infected by RSV-A and RSV-B types did not reveal any significant differences, but the children infected by genotype A/NA1 more frequently had lower respiratory tract infections (p<0.0001) and required hospitalisation (p = 0.007) more often than those infected by genotype A/ON1. These findings show that RSV has complex patterns of circulation characterised by the periodical replacement of the predominant genotypes, and indicate that the circulation and pathogenic role of the different RSV strains should be investigated as each may have a different impact on the host. A knowledge of the correlations between types, genotypes and disease severity may also be important in order to be able to include the more virulent strains in future vaccines.

Rapid replacement of prevailing genotype of human respiratory syncytial virus by genotype ON1 in Beijing, 2012-2014

Human respiratory syncytial virus (HRSV) is the most common viral pathogen causing lower respiratory infections in infants and young children worldwide. HRSV ON1 genotype in subgroup A with a characteristic of a 72 nucleotide duplication in the second highly variable region of attachment glycoprotein gene, has been reported in some countries since it was first detected in clinical samples collected in Canada in 2010. In this study, 557 HRSV antigen-positive nasopharyngeal aspirates were randomly selected during 2012/2013 to 2013/2014 HRSV seasons in Beijing for subgroup typing and for ON1 genotype screening by using a PCR based method developed for easily identifying genotype ON1 out of strains of subtype A. It was found that subgroup B was dominant in the 2012/2013 season and sudden shift of subgroup dominance from B to A and rapid replacement of previously prevailing NA1 genotype by ON1 genotype occurred in the 2013/2014 season. Reversible amino acid replacement in the G protein gene was found in a new branch of ON1 genotype. The evolutionary rate of the 351 global ON1 sequences was estimated to 7.34 × 10(-3) nucleotide substitutions per site per year (95% highest probability density intervals, HPD, 5.71 × 10(-3) to 9.04 × 10(-3)), with the time of most recent common ancestor dating back to June 2009.

Complete genome sequences of human respiratory syncytial virus genotype a and B isolates from South Korea

There is a paucity of complete genome sequence information for human respiratory syncytial virus (HRSV). To this end, we sequenced the complete genome sequences of HRSV genotype A (HRSV-A/IC688/12) and genotype B (HRSV-B/GW0047/14 and HRSV-B/IC0027/14). This information will increase the understanding of HRSV genetic diversity, evolution, pathogenicity, antigenicity, and transmissibility.

Novel respiratory syncytial virus (RSV) genotype ON1 predominates in Germany during winter season 2012-13

Respiratory syncytial virus (RSV) is the leading cause of hospitalization especially in young children with respiratory tract infections (RTI). Patterns of circulating RSV genotypes can provide a better understanding of the molecular epidemiology of RSV infection. We retrospectively analyzed the genetic diversity of RSV infection in hospitalized children with acute RTI admitted to University Hospital Heidelberg/Germany between October 2012 and April 2013. Nasopharyngeal aspirates (NPA) were routinely obtained in 240 children younger than 2 years of age who presented with clinical symptoms of upper or lower RTI. We analyzed NPAs via PCR and sequence analysis of the second variable region of the RSV G gene coding for the attachment glycoprotein. We obtained medical records reviewing routine clinical data. RSV was detected in 134/240 children. In RSV-positive patients the most common diagnosis was bronchitis/bronchiolitis (75.4%). The mean duration of hospitalization was longer in RSV-positive compared to RSV-negative patients (3.5 vs. 5.1 days; p<0.01). RSV-A was detected in 82.1%, RSV-B in 17.9% of all samples. Phylogenetic analysis of 112 isolates revealed that the majority of RSV-A strains (65%) belonged to the novel ON1 genotype containing a 72-nucleotide duplication. However, genotype ON1 was not associated with a more severe course of illness when taking basic clinical/laboratory parameters into account. Molecular characterization of RSV confirms the co-circulation of multiple genotypes of subtype RSV-A and RSV-B. The duplication in the G gene of genotype ON1 might have an effect on the rapid spread of this emerging RSV strain.