Multiple viral introductions: molecular characterization of influenza B virus in Wenzhou, Zhejiang, China, from 2011 to 2014 based on hemagglutinin and neuraminidase genes

A Hemagglutinin Stem Vaccine Designed Rationally by AlphaFold2 Confers Broad Protection against Influenza B Infection

Two lineages of influenza B viruses (IBV) co-circulating in human beings have been posing a significant public health burden worldwide. A substantial number of broadly neutralizing antibodies (bnAbs) have been identified targeting conserved epitopes on hemagglutinin (HA) stem domain, posing great interest for universal influenza vaccine development. Various strategies to design immunogens that selectively present these conserved epitopes are being explored. However, it has been a challenge to retain native conformation of the HA stem region, especially for soluble expression in prokaryotic systems. Here, using a structure prediction tool AlphaFold2, we rationally designed a stable stem antigen “B60-Stem-8071”, an HA stem vaccine derived from B/Brisbane/60/2006 grafted with a CR8071 epitope as a linker. The B60-Stem-8071 exhibited better solubility and more stable expression in the E. coli system compared to the naïve HA stem antigen. Immunization with B60-Stem-8071 in mice generated cross-reactive antibodies and protected mice broadly against lethal challenge with Yamagata and Victoria lineages of influenza B virus. Notably, soluble expression of B60-stem-8071 in the E. coli system showed the potential to produce the influenza B vaccine in a low-cost way. This study represents a proof of concept for the rational design of HA stem antigen based on structure prediction and analysis.

Evolutionary dynamics of influenza B strains detected from paediatric acute respiratory infections in central Vietnam

Influenza virus B belongs to the family Orthomyxoviridae with segmented negative-sense RNA genomes. Since 1970s, influenza B has diverged intoVictoria and Yamagata, which differs in antigenic and evolutionary characteristics. Yet, molecular-epidemiological information of influenza B from developing nations is limited. In central Vietnam, influenza A subtype-specific circulation pattern and clinical characteristics were previously described. However, molecular evolutionary characteristics of influenza B has not been discussed to date. We utilized the influenza B positives obtained from paediatric ARI surveillance during 2007-2013. Influenza B HA and NA genes were amplified, sequenced, and phylogenetic/molecular evolutionary analysis was performed using Maximum Likelihood and Bayesian MCMC. Phylodynamics analysis was performed with Bayesian Skyline Plot (BSP). Furthermore, we performed selection pressure analysis and estimated N-glycosylation sites. In the current study, overall positive rate for influenza B was 3.0%, and Victoria lineage immediately became predominant in post-A/H1N1pdm09 period. The noticeable shift in Victoria lineage WHO Group occurred. With respect to the evolutionary rate (substitutions/site/year), Victoria lineage HA gene was evolving faster than Yamagata lineage (2.43 × 10^-3 vs 2.00 × 10^-3). Furthermore, the evolutionary rate of Victoria Group 5 was greater than Group 1. BSP presented the rapid growth in Effective Population Size (EPS) of Victoria lineage occurred soon after the 1st A/H1N1pdm09 case was detected whereas the EPS of Yamagata lineage was stable for both genes. N-glycosylation pattern between lineages and among WHO Groups were slightly different, and HA gene had a total of 6 amino acid substitutions under positive section pressure (4 for Victoria and 2 for Yamagata). The current results highlight the importance of Victoria lineage in post-A/H1N1pdm09 period. Difference in evolutionary characteristics and phylodynamics may indicate lineage and WHO Group-specific evolutionary dynamics. It is necessary to further continue the molecular-epidemiological surveillance in local setting to gain a better understanding of local evolutionary characteristics of influenza B strains.

Co-circulation of influenza A(H1N1), A(H3N2), B(Yamagata) and B(Victoria) during the 2017-2018 influenza season in Zhejiang Province, China

Influenza is a major human respiratory pathogen. Due to the high levels of influenza-like illness (ILI) in Zhejiang, China, the control and prevention of influenza was challenging during the 2017-2018 season. To identify the clinical spectrum of illness related to influenza and characterise the circulating influenza virus strains during this period, the characteristics of ILI were studied. Viral sequencing and phylogenetic analyses were conducted to investigate the virus types, substitutions at the amino acid level and phylogenetic relationships between sequences. This study has shown that the 2017/18 influenza season was characterised by the co-circulation of influenza A (H1N1) pdm09, A (H3N2) and B viruses (both Yamagata and Victoria lineage). From week 36 of 2017 to week 12 of 2018, ILI cases accounted for 5.58% of the total number of outpatient and emergency patient visits at the surveillance sites. Several amino acid substitutions were detected. Vaccination mismatch may be a potential reason for the high percentage of ILI. Furthermore, it is likely that multiple viral introductions played a role in the endemic co-circulation of influenza in Zhejiang, China. More detailed information regarding the molecular epidemiology of influenza should be included in long-term influenza surveillance.

Analysis of influenza B virus lineages and the HA1 domain of its hemagglutinin gene in Guangzhou, southern China, during 2016

Background

Few studies have analyzed influenza B virus lineages based on hemagglutinin A (HA) gene sequences in southern China. The present study analyzed the HA gene and the lineages of influenza B virus isolates from Guangzhou during 2016, and compared our results with the WHO-recommended vaccine strain.

Methods

Ninety patients with influenza B were recruited from the First Hospital of Guangzhou Medical University. Throat swab specimens of 72 patients had high viral loads. Among these 72 isolates, the HA1 domain of the HA gene in 43 randomly selected isolates was sequenced using reverse transcription-polymerase chain reaction (RT-PCR), and analyzed using MEGA 5.05.

Results

Eight of the 90 patients (8.9%) also had influenza A virus infections. Analysis of the 43 influenza B virus isolates indicated that 34 (79.1%) were from the Victoria lineage and 9 (20.9%) were from the Yamagata lineage. A comparison isolates in our Victoria lineage with the B/Brisbane/60/2008 strain indicated 12 mutation sites in the HA1 domain, 4 of which (I132V, N144D, C196S, and E198D) were in antigenic epitopes. A comparison of isolates in our Yamagata lineage with the B/Phuket/3073/2013 stain indicated 5 mutation sites in the HA1 domain, none of which was in an antigenic epitope. None of the isolates had a mutation in regions of the neuraminidase gene (NA) that are known to confer resistance to NA inhibitors.

Conclusion

In Guangzhou during 2016, most influenza B virus isolates were from the Victoria lineage, in contrast to the vaccine strain recommended by the WHO for this period.

Electronic supplementary material

The online version of this article (10.1186/s12985-018-1085-5) contains supplementary material, which is available to authorized users.