Yamagata Lineage Research Articles

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.

A novel digital device-based adjuvant-like effect for influenza vaccine: A feasibility and pilot study

Abstract Viral infections such as influenza and COVID-19 have a huge impact on humans. Previous studies showed that some exercise could enhance the anti-viral antibody titers after vaccination. We developed a novel digital device designed to enhance host immune system against viral infection by acting like adjuvants. The digital device, SAT-008, is a mobile application based on an algorithm to regulate physical activity. To assess the feasibility of SAT-008, a randomized, open-label, and controlled study was conducted for 13 weeks (Oct 20 to Jan 21). A total of 42 healthy adults (mostly healthcare workers) aged 24 to 46 years were recruited and finally 32 subjects served for analysis. A single-dose of quadrivalent inactivated influenza vaccine was administered for each subject. The control group maintained daily life without using SAT-008, while the experimental group (Exp) used SAT-008 during the study. As a result, compared to the controls, the Exp showed a significant increase in hemagglutination-inhibition (HI) titers of antigen subtype B Yamagata lineage after 4 weeks of vaccination and antigen subtype B Victoria lineage after 12 weeks of vaccination (P < 0.05), whereas the controls did not. As for type A influenza, there was no significant difference in HI titers between groups. In addition, the Exp was divided into high performers (HP) and low performers (LP) based on the adherence rate. The HP showed significantly higher HI titers of B Yamagata lineage in 12 weeks after vaccination than controls and LP (P < 0.05) and of B Victoria lineage than controls (P < 0.01). Our findings indicate a novel approach using digital device may play an important role to enhance host immune system to act as a vaccine adjuvant against viral diseases such as influenza. Supported by grants from S-Alpha Therapeutics, Inc.

Recommended Adult Immunization Schedule, United States, 2022.

Recommended Adult Immunization Schedule, United States, 2022.

The Victoria and Yamagata Lineages of Influenza B Viruses, unknown and undervalued

El virus gripal B pertenece a la familia Orthomyxoviriridae y al género Influenzavirus B. Presenta un genoma de tipo ARN negativo formado por unos 14.648 nucleótidos divididos en ocho segmentos distintos que codifican unas 11 proteínas. Antes de 1980 todos los virus de la gripe B pertenecían a un único linaje genético; pero en este año emergieron dos linajes antigénica y genéticamente distintos que se denominaron B/ Victoria/2/1987 y B/Yamagata/16/1988. Se han podido demostrar procesos de intercambio genético intralinajes y entrelinajes; de ellos los mas frecuentes son aquellos en los que el linaje Victoria adquiere genes del linaje Yamagata. Se ha propuesto que las diferencias en las dinámicas evolutivas de los dos linajes se deban a las diferentes preferencias de unión de la hemaglutinina gripal al receptor celular. El linaje Victoria ha mostrado capacidad para unirse a los receptores celulares con restos de ácido siálico en las posiciones α-2,3 y α-2,6; mientras que el linaje Yamagata lo hace exclusivamente en las posiciones humanas α-2,6 del tracto respiratorio. La escasa circulación en los últimos meses podría haber contribuido a la eliminación (“extinción”) temporal del linaje Yamagata. Desde 2017 la casi totalidad de las cepas de este linaje pertenecen al clado 3A, cuando con anterioridad se detectaban clados múltiples circulando. Aunque este clado 3A es diverso a nivel genético y ha adquirido mutaciones sustitutivas en el gen de la hemaglutinina, éstas no han determinado cambios antigénicos significativos que hayan obligado a sustituir su componente antigénico (B/Pukhet/3073/2013) en la vacuna gripal desde 2015.

Report of the National Influenza Surveillance Scheme, 2011 to 2018.

This report describes influenza surveillance activities in Australia for the period 2011 to 2018. Data were extracted from several sources constituting the National Influenza Surveillance Scheme (NISS). Laboratory-confirmed influenza notification rates (per 100,000 population) increased from 122 in 2011 to 1,021 in 2017, before declining to 235 in 2018. The highest laboratory-confirmed notification rates during the eight-year period were from the smaller jurisdictions (South Australia and the Northern Territory), except in 2016 when Queensland reported the highest rate. Similar trends were observed in community reports of influenza-like illness (ILI), presentations of ILI to sentinel general practice (GP) sites, and influenza hospitalisations. Children aged 14 years or younger, and adults 65 years of age or older, had the highest notification rates of laboratory-confirmed influenza. Adults aged 65 years or older and patients with comorbidities had higher rates of influenza-associated hospitalisations and mortality. Over half of eligible patients admitted to sentinel hospitals (57%) received oseltamivir treatment, with 17% receiving the treatment within 48 hours of symptom onset. Influenza type A predominated over the eight years, except in 2015 when type B predominated. This trend was consistent with Australian World Health Organization Collaborating Centre (WHOCC) data for influenza isolates tested. Of influenza viruses circulating during the reporting period, A(H1N1) viruses were mostly antigenically similar to the vaccine strain A/California/7/2009 (H1N1), except in 2017 and 2018 when they were mostly similar to A/Michigan/45/2015. The A(H3N2) strains varied over the years but included the vaccine strains A/Perth/16/2009, A/Switzerland/9715293/2013, A/Hong Kong/4801/2014, and A/Singapore/INFIMH/2016. The B/Victoria/2/87 lineage (represented by the 2016 vaccine strain B/Brisbane/60/2008) and the B/Yamagata/16/88 lineage (represented by the southern hemisphere 2015 vaccine strain B/Phuket/3073/2013) were the circulating influenza B viruses during the reporting period. Influenza B accounted for just under a third of notifications (32%) from 2011 to 2018. Fifty-four per cent of influenza B viruses characterised by the Australian WHOCC site during the eight-year period were from the Yamagata lineage, although the proportion was higher (67%) when analysing the most recent four years (2015 to 2018). In contrast, during the 2010 season, 99% of all influenza B viruses characterised by the Australian WHOCC site were in the B-Victoria lineage. During the 2018 season the Australian WHOCC site detected, for the first time, swine A(H3N2)v virus from a human patient in Australia, highlighting the need to maintain vigilance for zoonotic infections.

Influenza in the COVID-19 era: principles of modern pharmacotherapy

Influenza is one of the most common infectious diseases and a significant public health problem. Every year, the influenza virus causes 3–5 million severe cases, millions hospitalizations and approximately 650,000 deaths. According to WHO four new influenza strains are projected to circulate in the 2020–2021 epidemic season. Influenza A and B strains are: A/Guangdong-Maonan/ SWL1536/2019 (H1N1) pdm09, A/Hong Kong/2671/2019 (H3N2), B/Washington/02/2019 (Victoria lineage), B/ Phuket/3073/2013 (Yamagata lineage). In this context, the problem of prescribing rational antiviral therapy is particularly importance. COVID-19, along with influenza, is a group of respiratory viral infections, but important differences exist in terms of viral agents and the spread of infection. Important differences include the rate of transmission. The average incubation period and generation time (the time between infecting one person and infecting another) for influenza are shorter. COVID-19 may be more severe, causing complications and deaths in 3–4% of cases. The estimated generation time for COVID 19 is 5-6 days, while for influenza it is 3 days. According to the latest data, the reproductive number, i.e., the number of people who can be infected by one patient, is in the range of 2 to 2.5 in COVID 19, which is higher than in influenza. Only a laboratory test can accurately identify the type of pathogen and distinguish it from influenza and other respiratory viruses. Neuraminidase inhibitors are currently first-line drugs recommended by WHO for the treatment and prevention of influenza.

Genomic surveillance: Brief summary of the Influenza virological activity in Ecuador reported by National Influenza Centre of Ecuador from INSPI

For H1N1pdm were grouped within clade 6B.1, and related to the strain of vaccine reference for that year, regarding the H3 subtype were grouped within genotype 3C.2a, which are related to the strain of vaccine reference for the H3N2 subtype recommended by WHO in the formulation of the 2016 Southern Hemisphere and 2017-18 Northern Hemisphere (A/Hong Kong/ 4801/2014), but other group of Ecuadorian samples from 2017, were genetically related to clade 3C.3a, this cluster is more related to Northern Hemisphere Vaccine strain 2015-2016 and Southern Hemisphere 2015 (A/Switzerland/9715293/2013), so we could observe different genetic lineages of H3N2 subtype co-circulate in Ecuador during 2017. In the case of Influenza B we also had a co-circulation of Yamagata and Victoria lineages but the trivalent formulation only had Victoria lineages.

Correlation of Influenza B Haemagglutination Inhibiton, Single-Radial Haemolysis and Pseudotype-Based Microneutralisation Assays for Immunogenicity Testing of Seasonal Vaccines.

Influenza B is responsible for a significant proportion of the global morbidity, mortality and economic loss caused by influenza-related disease. Two antigenically distinct lineages co-circulate worldwide, often resulting in mismatches in vaccine coverage when vaccine predictions fail. There are currently operational issues with gold standard serological assays for influenza B, such as lack of sensitivity and requirement for specific antigen treatment. This study encompasses the gold standard assays with the more recent Pseudotype-based Microneutralisation assay in order to study comparative serological outcomes. Haemagglutination Inhibition, Single Radial Haemolysis and Pseudotype-based Microneutralisation correlated strongly for strains in the Yamagata lineage; however, it correlated with neither gold standard assays for the Victoria lineage.

Safety, Immunogenicity, and Protective Efficacy of a Chimeric A/B Live Attenuated Influenza Vaccine in a Mouse Model.

Influenza A and B viruses cause significant morbidity and mortality worldwide. Current influenza vaccines are composed of three or four strains: A/H1N1, A/H3N2, and B (Victoria and Yamagata lineages). It is of great interest if immunization against both type A and B influenza viruses can be combined in a single vaccine strain, thus reducing the cost of vaccine production and the possibility of strain interference within the multicomponent vaccine. In the current study, we developed an experimental live cold-adapted influenza intertype reassortant (influenza A and B) vaccine on the live attenuated influenza vaccine (LAIV) A/Leningrad/134/17/57 backbone. Hemagglutinin (HA) and neuraminidase (NA) functional domains were inherited from the influenza B/Brisbane/60/2008 strain, whereas their packaging signals were substituted with appropriate fragments of influenza A virus genes. The recombinant A/B virus efficiently replicated in eggs and Madin–Darby Canine Kidney (MDCK) cells under optimal conditions, temperature-sensitive phenotype was maintained, and its antigenic properties matched the influenza B parental virus. The chimeric vaccine was attenuated in mice: after intranasal immunization, viral replication was seen only in nasal turbinates but not in the lungs. Immunological studies demonstrated the induction of IgG antibody responses against the influenza A and B virus, whereas hemagglutination inhibition (HAI) and neutralizing antibodies were detected only against the influenza B virus, resulting in significant protection of immunized animals against influenza B virus challenge. IFNγ-secreting CD8 effector memory T cells (CD44+CD62L−) were detected in mouse splenocytes after stimulation with the specific influenza A peptide (NP366); however, the T-cell response was not sufficient to protect animals against infection with a high-dose mouse-adapted A/California/07/2009 (H1N1pdm09) virus, most probably due to the mismatch of key T-cell epitopes of the H1N1 virus and the LAIV backbone. Overall, generation of the chimeric A/B LAIV virus on a licensed LAIV backbone demonstrated prospects for the development of safe and efficacious vaccine candidates that afford combined protection against both type A and type B influenza viruses; however, further optimization of the T-cell epitope content within the LAIV backbone may be required.

159. efficacy of CD377, a Novel Antiviral Fc-conjugate, Against Seasonal Influenza in Lethal Mouse Infection Models

BackgroundCidara’s AVCs (antiviral Fc-conjugates) are novel conjugates of potent, antiviral agents with the Fc domain of human IgG1. CD377 is an AVC development candidate for prevention and treatment of influenza that has broad anti-neuraminidase activity in both enzymatic and cell-based assays and the potential to engage the immune system, as well as a long half-life.MethodsEfficacy studies were conducted in BALB/c mice lethally challenged intranasally at 3x the LD95 with influenza A (H1N1, H3N2) and influenza B (both lineages). CD377 was administered as a single dose subcutaneously (SC) 2 hours after viral challenge. Body weights (BW) and health scores were monitored daily, with 20% BW loss recorded as a mortality.ResultsIn mice challenged with a lethal dose of an H1N1 strain (A/California/12/2012), a single 0.3 mg/kg dose of CD377 administered 2 hours post-challenge was fully protective (P=0.0015 relative to vehicle) (Fig 1A). In a similar study against a mouse-adapted H3N2 subtype (A/Hong Kong/1/1968), a single dose of CD377 at 0.1 mg/kg was fully protective (P=0.0025) (Fig 1B). In both studies, only a transient loss of BW was observed before mice began recovering weight.The activity of CD377 was also evaluated against both lineages of influenza B (Fig 1C, 1D). Against influenza B/Colorado/06/2017 (Victoria), a single CD377 dose of 0.3 mg/kg was fully protective (P=0.0035) while the Fc-only control dosed at 1 mg/kg was not, as expected. Against the Yamagata lineage (B/Florida/4/2006), CD377 demonstrated full protection at a dose of only 0.03 mg/kg (P=0.0023).ConclusionA single dose of CD377 (0.3 mg/kg or less) was protective against lethal challenge with several seasonal influenza A/B subtypes. The exceptional PK profile of CD377 combined with potent broad-spectrum activity highlight its potential for use as a long-term preventative against seasonal influenza.Seasonal influenza efficacy DisclosuresJames Levin, PhD, Cidara Therapeutics (Shareholder) Karin Amundson, BSc, Cidara Therapeutics (Shareholder) Allen Borchardt, PhD, Cidara Therapeutics (Employee) Thanh Lam, PhD, Cidara Therapeutics (Shareholder) Tom Brady, PhD, Cidara Therapeutics (Shareholder) Alain Noncovich, PhD, Cidara Therapeutics (Shareholder) Les Tari, PhD, Cidara Therapeutics (Shareholder)

Antibodies That Engage the Hemagglutinin Receptor-Binding Site of Influenza B Viruses.

We describe cross-reactive human antibodies recognizing influenza B viruses spanning nearly 80 years of antigenic drift. Structures show that they engage the receptor-binding site (RBS) of the viral hemagglutinin with strong similarities to their influenza A counterparts, despite structural differences between the RBS of influenza A and B. Our data show that these antibodies readily cross-react with both influenza B Victoria and Yamagata lineages. We also note that all antibodies are encoded by IGHV3-9/IGK1-33. Future research will provide insight into the prevalence of these antibodies in the human population.

Comparison of influenza antibody titers among women who were vaccinated in the 2nd and the 3rd trimesters of pregnancy

BackgroundWe compared cord blood antibody titers in unvaccinated pregnant women to those vaccinated with seasonal influenza vaccine during the 2nd and the 3rd trimesters. MethodsPregnant women had cord blood collected at delivery for hemagglutination inhibition assay against vaccine reference viruses: A/California/07/2009 (H1N1)pdm09, A/Switzerland/9715293/2013 (H3N2), and B/Phuket/3073/2013 (Yamagata lineage). Geometric mean titer (GMT) ratios were calculated comparing vaccinated versus unvaccinated pregnant women, and women vaccinated in the 2nd and the 3rd trimesters. Proportions of women achieving defined titers were compared using the χ2 test. ResultsOf 307 women, 190 (62%) were unvaccinated. Fifty and 67 were vaccinated during the 2nd and the 3rd trimesters, respectively. Median enrollment age was 29 years (interquartile range 24–34). Sixteen (5%) women had pre-existing conditions, but none were immunocompromised. GMT ratios comparing vaccinated and unvaccinated women were 5.90 (95% confidence interval [CI] 5.06–6.96) for influenza A/California, 5.39 (95% CI 4.18–6.08) for influenza A/Switzerland, and 5.05 (95% CI 4.43–5.85) for influenza B/Phuket. Similarly, the GMT ratios comparing the 3rd and the 2nd trimester vaccinated women were 2.90 (95% CI 2.54–3.39), 2.82 (95% CI 2.56–3.13), and 2.83 (95% CI 2.56–3.14), respectively. The proportions of women with defined titers for the three vaccine reference viruses did not differ between 2nd and 3rd trimester vaccinated women (titers ≥40: 68–92% versus 70–93%; ≥110: 32% versus 33–63%; and ≥330: 4–10% versus 3–21%). ConclusionsPregnant women vaccinated against influenza had more placental transfer of influenza antibodies to their infants than unvaccinated women. Placental transfer of antibodies was higher among those vaccinated in the 3rd trimester than in the 2nd trimester. There was no difference in the proportions of women achieving antibody titers corresponding to protection against influenza in children. Findings support the current World Health Organization’s recommendation that pregnant women may be vaccinated in either 2nd or 3rd trimester of pregnancy.

Influenza vaccine effectiveness against laboratory-confirmed influenza in a vaccine-mismatched influenza B-dominant season

BackgroundThe 2017–2018 influenza season in Israel was characterized by the predominance of influenza B Yamagata, with a lesser circulation of influenza A(H1N1)pdm09 and influenza A(H3N2). We estimated vaccine effectiveness (VE) of the inactivated influenza vaccine which was selected for use that season. MethodsEnd-of-season VE and 95% confidence intervals (CI) against laboratory-confirmed influenza-like illness (ILI) were estimated by means of the test-negative design. Age-specific VE analysis was carried out using a moving age interval. ResultsSpecimen were obtained from 1,453 community ILI patients; 610 (42.0%) were influenza-positive, among which 69.7% were B, 17.2% A(H1N1)pdm09 and 13.4% A(H3N2). A 98.6% of molecularly characterized influenza B belonged to the Yamagata lineage. Of the sampled individuals, 1320 were suitable for VE analysis. Of those vaccinated, 90.6% received the inactivated trivalent influenza vaccine (TIV) containing a Victoria lineage influenza B-like virus. VE against influenza A differed by age, with the highest VE of 72.9% (95%CI 31.9–89.2%) observed in children 0.5–14 years old, while all ages VE was 46.6% (95%CI 10.4–68.2%). All ages VE against influenza B was 23.2% (95%CI −10.1–46.4%) with age-specific analysis showing non-significant VE estimates. Utilizing a moving age interval of 15 years, afforded a detailed age-specific insight into influenza VE against the influenza viruses circulating during the 2017–2018 season. ConclusionsThe moderate-high 2017–2018 influenza A VE among children and adolescents, supports seasonal influenza vaccination at a young age. The low VE against influenza B in Israel, is most likely the result of influenza B/TIV-mismatch.

Influenza B infections in children: A review.

Influenza B (IFB) virus belongs to the Orthomyxoviridae family and has two antigenically and genetically distinct lineages; B/Victoria/2/87-like (Victoria lineage) and B/Yamagata/16/88-like (Yamagata lineage). The illness caused by IFB differs from that caused by influenza A. Outbreaks of IFB occur worldwide and young children exposed to IFB are likely to have a higher disease severity compared with adults. IFB mostly causes mild to moderate respiratory illness in healthy children. However, the involvement of other systems, a severe disease especially in children with chronic medical conditions and immunosuppression, and rarely mortality, has been reported. Treatment with oseltamivir or zanamivir decreases the severity of illness and hospitalization. Due to the enormous health and economic impact of IFB, these strains are included in vaccines. IFB illness is less studied in children although its impact is substantial. In this review, the epidemiology, clinical manifestations, treatment, prognosis, and prevention of IFB illness in children are discussed.

2011-2019年中国B型流感季节性、年龄特征和疫苗匹配度分析

Objective: To analyze the seasonality, age distribution of influenza B cases and matching degree of influenza B vaccine in China from 2011 to 2019, and provide evidences for the future surveillance, estimation of disease burden of influenza B, application of quadrivalent vaccines, and development of vaccine strategies. Methods: The epidemiological and virological surveillance data of influenza B from week 14 of 2011 to week 13 of 2019 obtained from National Influenza Surveillance Network were used to draw hot spot maps and conduct descriptive statistics to analyze the seasonality and age distribution of influenza B cases. The published antigenicity analysis results from the China Weekly Influenza Report were used to analyze the matching degree between the trivalent vaccine strain and the circulating influenza B strains. Results: From 2011 to 2019, the incidence of influenza B showed obvious seasonal characteristics, and influenza B virus co-circulated with influenza A virus in six winter-spring seasons, and influenza B virus/Victoria and Yamagata lineages circulated alternately. In some southern provinces, two lineages co-circulated in some southern areas in certain years. The age distribution of influenza B cases was double-peaked, and both lineages had the highest positive rate in age-group 5-15 years, with peaks at age of 10 years; B/Victoria virus had a sub-peak in age-group 25-35 years; B/Yamagata virus had a sub-peak in age-group 55-65 years. Trivalent influenza vaccine strain and influenza B epidemic strains mismatched in 2015-2016 and 2017-2018 seasons, matched in 2011-2012, 2012-2013, 2013-2014, 2014-2015 and 2016-2017 seasons, and moderately matched in 2018-2019 season, but reactivity was low. Conclusions: Influenza B mainly occurred in winter-spring season in China, and its intensity was lower than that of influenza A. There was a difference in the age distribution of the cases among different virus strains. Trivalent influenza vaccine strains and influenza B epidemic strains mismatched in several seasons. It is crucial to conduct continuous surveillance of influenza B and disease burden evaluation, improve vaccine immunization strategy, increase influenza vaccination rate to reduce the harm of influenza B in high-risk groups.

Substitutions at H134 and in the 430-loop region in influenza B neuraminidases can confer reduced susceptibility to multiple neuraminidase inhibitors

With the introduction of the influenza specific neuraminidase inhibitors (NAIs) in 1999, there were concerns about the emergence and spread of resistant viruses in the community setting. Surveillance and testing of community isolates for their susceptibility to the NAIs was initially carried out by the Neuraminidase Inhibitor Susceptibility Network (NISN) and has subsequently been taken on by the global WHO influenza network laboratories. During the NISN surveillance, we identified two Yamagata lineage influenza B viruses with amino acid substitutions of H134Y (B/Auckland/2/2001) or W438R (B/Yokohama/12/2005) which had slightly elevated IC50 values for zanamivir and/or oseltamivir, but not sufficiently to be characterized as mild outliers at the time. As it has now been well demonstrated that mixed populations can mask the true magnitude of resistance of a mutant, we re-examined both of these isolates by plaque purification to see if the true susceptibilities were being masked due to mixed populations. Results confirmed that the B/Auckland isolate contained both wild type and H134Y mutant populations, with mutant IC50 values > 250 nM for both oseltamivir and peramivir in the enzyme inhibition assay. The B/Yokohama isolate also contained both wild type and W438R mutant populations, the latter now demonstrating IC50 values > 400 nM for zanamivir, oseltamivir and peramivir. In addition, plaque purification of the B/Yokohama isolate identified viruses with other single neuraminidase substitutions H134Y, H134R, H431R, or T436P. H134R and H431R viruses had IC50 values > 400 nM and >250 nM respectively against all three NAIs. All changes conferred much greater resistance to peramivir than to zanamivir, and less to oseltamivir, and affected the kinetics of binding and dissociation of the NAIs. Most affected affinity (Km) for the MUNANA substrate, but some had decreased while others had increased affinity. Despite resistance in the enzyme assay, no reduced susceptibility was seen in plaque reduction assays in MDCK cells for any of the mutant viruses. None of these substitutions was in the active site. Modelling suggests that these substitutions affect the 150 and 430-loop regions described for influenza A NAs, suggesting they may also be important for substrate and inhibitor binding for influenza B NAs.

Age- and sex-specific excess mortality associated with influenza in Shanghai, China, 2010–2015

ObjectiveFew studies have explored the different lineages of influenza B viruses, which cause excessive fatalities. This study aimed to estimate age- and sex-specific excessive mortality associated with influenza subtypes/lineages in Shanghai, during 2010–2015. MethodsWe used quasi-Poisson regression models to fit weekly numbers of deaths from various causes by adjusting long-term trend, seasonal trend, and absolute humidity as confounding factors. The mortality burden associated with influenza subtypes/lineages was estimated by age and sex. ResultsThe average influenza-associated excessive mortality rate in deaths coded as all-cause was 27.66 (95%CI: 22.30–33.88) per 100,000 person-years. The excessive deaths from six underlying causes in people aged ≥65 years weight heavily. Compared to influenza B(Victoria) lineage, influenza B(Yamagata) lineage had more effect on the influenza-associated disease burden, particularly in patients with respiratory and circulatory diseases. There was no statistical significance of sex in the mortality burden associated with influenza. ConclusionDisproportionate mortality associated with influenza B virus is dominated by B(Yamagata) lineage in Shanghai, and the evidence for sex differences in the influenza-associated mortality burden for respiratory and circulatory diseases is limited. Improving the vaccination of the elderly and strengthening laboratory-based surveillance of influenza B lineages in Shanghai are needed to reduce this influenza’s disease burden.

A newly developed real-time PCR assay for discriminating influenza B virus Yamagata and Victoria lineages.

Currently, two distinct lineages of influenza B virus (IBV), B/Victoria and B/Yamagata lineage, have been co-circulating in human beings. Assessment of the prevalent lineage is key for the recommendation of the seasonal influenza vaccine composition and the evaluation of its efficacy. In this study, a multiplex qRT-PCR assay for the discrimination of the IBV lineages was designed based on the genetic differences of the hemagglutinin genes between B/Yamagata and B/Victoria lineages. The assay was highly specific and able to discriminate the lineages of IBV without any non-specific reaction against other influenza A viruses. The detection limit of the assay was determined to be 10 genome-equivalent copies and 2.8 × 10-2 50% tissue culture infectious doses (TCID50 ) of live IBV per reaction. Moreover, our assay was able to discriminate the lineages of IBVs in clinical samples with 100% accuracy, when compared with pyrosequencing. Our results indicate that this assay may represent an update of the existing qRT-PCR assays and will be of great use for the rapid and accurate diagnosis and surveillance of the circulating IBVs.

Novel oseltamivir-resistant mutations distant from the active site of influenza B neuraminidase

We performed a neuraminidase sequence analysis of thirty-two pediatric patients with influenza B who visited Teikyo University Hospital from January 2016 to March 2017, and found oseltamivir-resistant samples belonging to the Yamagata and Victoria lineages. Comparison with the neuraminidase sequence of oseltamivir-susceptible B/Brisbane/60/2008 revealed 5 common amino acid substitutions in many of these samples. According to the binding free energy calculation, the N340D and E358K substitutions reduced the affinity of oseltamivir to neuraminidase. Unexpectedly, these substitutions were located distant from the oseltamivir-binding site in neuraminidase. According to the molecular dynamics simulations, the N340D substitution rearranged complicated hydrogen bond networks in an extensive surface region of neuraminidase. The E358K substitution extensively altered the electrostatic potential map of the overall neuraminidase structure. Through these novel mechanisms, the N340D and E358K substitutions indirectly influenced the affinity reduction. These results may be useful for designing drugs for the treatment of oseltamivir-resistant virus infections. Communicated by Ramaswamy H. Sarma

The role of influenza viruses in the development of severe acute respiratory infection in patients admitted to Yekaterinburg hospitals during 2017–2018 epidemic season

Objective. To study the role of influenza viruses in the development of severe acute respiratory infections (SARI) in patients admitted to Yekaterinburg hospitals during 2017-2018 epidemic season.Materials and Methods. A retrospective epidemiological analysis of influenza incidence in Yekaterinburg was conducted, 403 influenza and acute respiratory viral infections case sheets were studied, and PCR analysis of clinical samples from the patients for respiratory viral infections was performed.Results. During the epidemic period a total 27.0% of the Yekaterinburg population were reported with influenza and other SARI, with 1.8% patients hospitalized. 5.6% of the total number of patients admitted with influenza and SARI in Yekaterinburg hospitals were included in the study. The rate of the detection of influenza A and B viruses RNA in the clinical samples from the patients with SARI was 28.3%. The rates of the detection in PCR of influenza B/Yamagata, A(H1N1)pdm09 and A(H3N2) were 46.5, 20.2 and 10.5%, respectively.Conclusion. The study results indicated that influenza viruses remain significant pathogens of respiratory infections that required hospitalization. Among patients with SARI the highest incidence was observed in children of a younger age group and was mainly associated with influenza B virus of Yamagata lineage and influenza A virus (H1N1)pdm09. According to the results of a molecular genetic study, influenza A (H1N1) pdm09 viruses belonged to clade 6B.1, carried characteristic amino acid substitutions in hemagglutinin S84N, S162N (with the acquisition of a potential glycosylation site) and I216T and were similar to the A/Michigan/45/2015 vaccine strain. The influenza B viruses studied belonged to the Yamagata lineage, clade 3. The influenza B/Ekaterinburg /RII-4723S/2018 virus differed from the reference strain B/Phuket/3073/2013 by two amino acid substitutions in the hemagglutinin gene M251V and L172Q.