Drift Variants Research Articles

Sex Differences during Influenza A Virus Infection and Vaccination and Comparison of Cytokine and Antibody Responses between Plasma and Serum Samples.

In this study, we evaluated sex differences during infection with mouse-adapted H1N1 and H3N2 influenza A viruses (IAVs) in the C57BL/6J mouse model and compared the cytokine and antibody responses between plasma and serum samples during IAV infection and vaccination. Lethal doses for both H1N1 and H3N2 IAVs were lower for adult females and they suffered with greater morbidity than adult males when infected with sublethal doses. In influenza virus-infected mice, cytokine responses differed between plasma and serum samples. After inactivated influenza virus vaccination and drift variant challenge, adult female mice had greater antibody responses and were better protected. In influenza-vaccinated and challenged mice, binding antibodies were unaffected between paired plasma or serum samples. However, functional antibody assays, including hemagglutination inhibition, microneutralization, and antibody-dependent cellular cytotoxicity assays, were affected by the use of plasma and serum sample types. Our results indicate that careful consideration is required while selecting plasma versus serum samples to measure cytokine and antibody responses during IAV infection and vaccination.

Antigenic drift and immunity gap explain reduction in protective responses against influenza A(H1N1)pdm09 and A(H3N2) viruses during the COVID-19 pandemic: a cross-sectional study of human sera collected in 2019, 2021, 2022, and 2023

BackgroundNon-pharmaceutical interventions implemented during the COVID-19 pandemic resulted in a marked reduction in influenza infections globally. The absence of influenza has raised concerns of waning immunity, and potentially more severe influenza seasons after the pandemic.MethodsTo evaluate immunity towards influenza post-COVID-19 pandemic we have assessed influenza A epidemics in Norway from October 2016 to June 2023 and measured antibodies against circulating strains of influenza A(H1N1)pdm09 and A(H3N2) in different age groups by hemagglutination inhibition (HAI) assays in a total of 3364 serum samples collected in 2019, 2021, 2022 and 2023.ResultsInfluenza epidemics in Norway from October 2016 until June 2023 were predominately influenza As, with a mixture of A(H1N1)pdm09 and A(H3N2) subtype predominance. We did not observe higher numbers of infections during the influenza epidemics following the COVID-19 pandemic than in pre-COVID-19 seasons. Frequencies of protective HAI titers against A(H1N1)pdm09 and A(H3N2) viruses were reduced in sera collected in 2021 and 2022, compared to sera collected in 2019. The reduction could, however, largely be explained by antigenic drift of new virus strains, as protective HAI titers remained stable against the same strain from one season to the next. However, we observed the development of an immunity gap in the youngest children during the pandemic which resulted in a prominent reduction in HAI titers against A(H1N1)pdm09 in 2021 and 2022. The immunity gap was partially closed in sera collected in 2023 following the A(H1N1)pdm09-dominated influenza seasons of 2022/2023. During the 2022/2023 epidemic, drift variants of A(H1N1)pdm09 belonging to the 5a.2a.1 clade emerged, and pre-season HAI titers were significantly lower against this clade compared to the ancestral 5a.2 clade.ConclusionThe observed reduction in protective antibodies against A(H1N1)pdm09 and A(H3N2) viruses post COVID-19 is best explained by antigenic drift of emerging viruses, and not waning of antibody responses in the general population. However, the absence of influenza during the pandemic resulted in an immunity gap in the youngest children. While this immunity gap was partially closed following the 2022/2023 influenza season, children with elevated risk of severe infection should be prioritized for vaccination.

Pre-existing T cell immune response specific to computationally optimized broadly reactive hemagglutinin antigens (COBRA-HA) in influenza vaccinees

Abstract The biggest challenge in developing a universal influenza vaccine is the extensive antigenic drift. In contrast to humoral immunity, cell-mediated immunity is more cross-reactive and can protect against various subtypes and drift variants. Our research group has described computationally optimized broadly reactive antigens (COBRA) to develop HA-based broadly protective influenza vaccine. However, studies that characterize the potential of COBRA-HA to elicit a functional T-cell response have yet to be developed. Cross-reactive response to conserved T cell epitopes from previous exposure can provide an efficient heterologous immunity. Thus, we aim to immune profile the pre-existing and cross-reactive COBRA-HA T cell response at the functionality and epitope conservation level to identify potential targets to be included in universal flu vaccine design. To achieve this goal, 50 donors who received the seasonal influenza vaccine (Fluzone, Sanofi) for two consecutive seasons were HLA typed, and the epitopes of COBRA-HA vaccine candidates Y2 (H1) and NG2 (H3) were predicted using IEDB software. Using the high dimensional flow cytometry, eight peptides for Y2 and 15 for NG2 were combined in pools to determine the phenotypes and cytokine secretion. We found that the vaccination induced a cross-reactive COBRA HA-specific CD4+ and CD8+ T cell response independent of antibody titers. Next, we will evaluate the Th helper subsets (Th1/Th2/Th17/cTfh) and the breadth of immune response by deconvoluting the pools in IFNγ Fluospot assay. Nonetheless, the next generation of the universal influenza vaccine recalled a functional CD4+ pre-existing response, demonstrating the potential efficacy of COBRA-HA in clinical trials. National Institute of Allergy and Infectious Diseases (NIAID), U.S. National Institutes of Health (NIH), Department of Health and Human Services contract 75N93019C00052 (TMR).

A rationally designed combined intranasal adjuvant drives robust and broad humoral, cellular, and mucosal immune responses to SARS-CoV-2

Abstract Multiple FDA-approved SARS-CoV-2 vaccines have provided excellent protection against severe disease. Despite this, immunity can wane relatively fast, particularly in the elderly and novel viral variants capable of evading infection- and vaccination-induced immunity continue to emerge. Furthermore, while these parenteral vaccines have provided substantial protection, they have been less effective in inducing mucosal immune responses which are critical for effectively blocking viral transmission in vaccinated individuals. As mucosal immune responses are most effectively induced through infection or mucosal immunization, we have developed an intranasal, rationally designed adjuvant integrating a nanoemulsion (NE) that activates TLRs and NLRP3 with an RNA agonist of RIG-I (IVT DI). Through activating this array of receptors, we have shown that the NE/IVT adjuvant better recapitulates the innate immune activation events that occur during natural viral infection, subsequently leading to more tailored and effective downstream adaptive immune responses. The combination adjuvant with various spike protein antigens elicited robust protective humoral, mucosal, and cellular responses to SARS-CoV-2 in mice, with markedly enhanced T H1-biased cellular responses and high virus-neutralizing antibody titers towards both homologous and antigenically distant drift variants of SARS-CoV-2. These results highlight the potential of this adjuvant to improve the immune profile of a variety of SARS-CoV-2 vaccine candidates for use mucosally. This research was supported by R01-AI160706 to P.W. and M.S, and in part by R01-DK130425 to M.S.

Tracking the emergence of antigenic variants in influenza A virus epidemics in Brazil.

Influenza A virus (IAV) circulation patterns differ in North America and South America, with influenza seasons often characterized by different subtypes and strains. However, South America is relatively undersampled considering the size of its population. To address this gap, we sequenced the complete genomes of 220 IAVs collected between 2009 and 2016 from hospitalized patients in southern Brazil. New genetic drift variants were introduced into southern Brazil each season from a global gene pool, including four H3N2 clades (3c, 3c2, 3c3, and 3c2a) and five H1N1pdm clades (clades 6, 7, 6b, 6c, and 6b1). In 2016, H1N1pdm viruses belonging to a new 6b1 clade caused a severe influenza epidemic in southern Brazil that arrived early and spread rapidly, peaking mid-autumn. Inhibition assays showed that the A/California/07/2009(H1N1) vaccine strain did not protect well against 6b1 viruses. Phylogenetically, most 6b1 sequences that circulated in southern Brazil belong to a single transmission cluster that rapidly diffused across susceptible populations, leading to the highest levels of influenza hospitalization and mortality seen since the 2009 pandemic. Continuous genomic surveillance is needed to monitor rapidly evolving IAVs for vaccine strain selection and understand their epidemiological impact in understudied regions.

A Bayesian approach to incorporate structural data into the mapping of genotype to antigenic phenotype of influenza A(H3N2) viruses.

Surface antigens of pathogens are commonly targeted by vaccine-elicited antibodies but antigenic variability, notably in RNA viruses such as influenza, HIV and SARS-CoV-2, pose challenges for control by vaccination. For example, influenza A(H3N2) entered the human population in 1968 causing a pandemic and has since been monitored, along with other seasonal influenza viruses, for the emergence of antigenic drift variants through intensive global surveillance and laboratory characterisation. Statistical models of the relationship between genetic differences among viruses and their antigenic similarity provide useful information to inform vaccine development, though accurate identification of causative mutations is complicated by highly correlated genetic signals that arise due to the evolutionary process. Here, using a sparse hierarchical Bayesian analogue of an experimentally validated model for integrating genetic and antigenic data, we identify the genetic changes in influenza A(H3N2) virus that underpin antigenic drift. We show that incorporating protein structural data into variable selection helps resolve ambiguities arising due to correlated signals, with the proportion of variables representing haemagglutinin positions decisively included, or excluded, increased from 59.8% to 72.4%. The accuracy of variable selection judged by proximity to experimentally determined antigenic sites was improved simultaneously. Structure-guided variable selection thus improves confidence in the identification of genetic explanations of antigenic variation and we also show that prioritising the identification of causative mutations is not detrimental to the predictive capability of the analysis. Indeed, incorporating structural information into variable selection resulted in a model that could more accurately predict antigenic assay titres for phenotypically-uncharacterised virus from genetic sequence. Combined, these analyses have the potential to inform choices of reference viruses, the targeting of laboratory assays, and predictions of the evolutionary success of different genotypes, and can therefore be used to inform vaccine selection processes.

Establishment of a Pseudovirus Platform for Neuraminidase Inhibiting Antibody Analysis.

Neuraminidase (NA)-based immunity to influenza can be useful for protecting against novel antigenic variants. To develop safe and effective tools to assess NA-based immunity, we generated a baculovirus-based pseudotyped virus, N1-Bac, that expresses the full-length NA of the influenza A/California/07/2009 (H1N1)pdm09 strain. We evaluated the level of NA-inhibiting (NI) antibodies in the paired blood sera of influenza patients by means of an enzyme-linked lectin assay (ELLA) using the influenza virus or N1-Bac. Additionally, we evaluated the level of NA antibodies by means of the enzyme-linked immunosorbent assay (ELISA) with an N1-expressing Sf21 culture. We detected a strong correlation between our results from using the influenza virus and NA-Bac pseudoviruses to detect NI antibodies and a medium-strong correlation between NI antibodies and NA antibodies determined by an N1-cell ELISA, indicating that baculovirus-based platforms can be successfully used to evaluate NI or NA antibodies. Furthermore, animal experiments showed that immunization with N1-Bac protected against infection with a drift variant of the A/H1N1pdm09 influenza virus. Our results demonstrate that recombinant baculovirus can be an effective influenza pseudotype to evaluate influenza serologic immunity and protect against influenza virus infection.

Modeling Infectious Bursal Disease Virus (IBDV) Antigenic Drift In Vitro

Infectious bursal disease virus (IBDV) vaccines do not induce sterilizing immunity, and vaccinated birds can become infected with field strains. Vaccine-induced immune selection pressure drives the evolution of antigenic drift variants that accumulate amino acid changes in the hypervariable region (HVR) of the VP2 capsid, which may lead to vaccine failures. However, there is a lack of information regarding how quickly mutations arise, and the relative contribution different residues make to immune escape. To model IBDV antigenic drift in vitro, we serially passaged a classical field strain belonging to genogroup A1 (F52/70) ten times, in triplicate, in the immortalized chicken B cell line, DT40, in the presence of sub-neutralizing concentrations of sera from birds inoculated with IBDV vaccine strain 2512, to generate escape mutants. This assay simulated a situation where classical strains may infect birds that have suboptimal vaccine-induced antibody responses. We then sequenced the HVR of the VP2 capsid at passage (P) 5 and 10 and compared the sequences to the parental virus (P0), and to the virus passaged in the presence of negative control chicken serum that lacked IBDV antibodies. Two escape mutants at P10 had the same mutations, D279Y and G281R, and a third had mutations S251I and D279N. Furthermore, at P5, the D279Y mutation was detectable, but the G281R mutation was not, indicating the mutations arose with different kinetics.

Antigenic Characterization of Neuraminidase of Influenza A/H7N9 Viruses Isolated in Different Years.

Influenza outbreaks caused by A/H7N9 viruses have occurred since 2013. After 2016, A/H7N9 influenza viruses underwent evolutionary changes. In this study, we examined the antigenic properties of influenza neuraminidase (NA) of A/H7N9 viruses as part of a live influenza vaccine (LAIV). It was shown that neuraminidase inhibiting (NI) antibodies obtained after A/Anhui/1/2013(H7N9)-based LAIV vaccination did not inhibit A/Hong Kong/125/2017(H7N9) NA and vice versa. The A/Hong Kong/125/2017(H7N9)-based LAIV elicited higher levels of NI antibodies compared to the A/Anhui/1/2013(H7N9)-based LAIV after two doses. Thelow degree of coincidence of the antibody response to hemagglutinin (HA) and NA after LAIV vaccination allows us to consider an enzyme-linked lectin assay (ELLA) as an additional measure for assessing the immunogenicity of influenza vaccines. In mice, N9-reactive monoclonal antibodies (mABs) for the A/environment/Shanghai/RL01/2013(H7N9) influenza virus partially protected against lung infection from the A/Guangdong/17SF003/2016 IDCDC-RG56N(H7N9) virus, thus showing the cross-protective properties of monoclonal antibodies against the drift variant.

From concept drift to model degradation: An overview on performance-aware drift detectors

The dynamicity of real-world systems poses a significant challenge to deployed predictive machine learning (ML) models. Changes in the system on which the ML model has been trained may lead to performance degradation during the system’s life cycle. Recent advances that study non-stationary environments have mainly focused on identifying and addressing such changes caused by a phenomenon called concept drift. Different terms have been used in the literature to refer to the same type of concept drift and the same term for various types. This lack of unified terminology is set out to create confusion on distinguishing between different concept drift variants. In this paper, we start by grouping concept drift types by their mathematical definitions and survey the different terms used in the literature to build a consolidated taxonomy of the field. We also review and classify performance-based concept drift detection methods proposed in the last decade. These methods utilize the predictive model’s performance degradation to signal substantial changes in the systems. The classification is outlined in a hierarchical diagram to provide an orderly navigation between the methods. We present a comprehensive analysis of the main attributes and strategies for tracking and evaluating the model’s performance in the predictive system. The paper concludes by discussing open research challenges and possible research directions.

A Combination Adjuvant for the Induction of Potent Antiviral Immune Responses for a Recombinant SARS-CoV-2 Protein Vaccine.

Several SARS-CoV-2 vaccines have received EUAs, but many issues remain unresolved, including duration of conferred immunity and breadth of cross-protection. Adjuvants that enhance and shape adaptive immune responses that confer broad protection against SARS-CoV-2 variants will be pivotal for long-term protection as drift variants continue to emerge. We developed an intranasal, rationally designed adjuvant integrating a nanoemulsion (NE) that activates TLRs and NLRP3 with an RNA agonist of RIG-I (IVT DI). The combination adjuvant with spike protein antigen elicited robust responses to SARS-CoV-2 in mice, with markedly enhanced TH1-biased cellular responses and high virus-neutralizing antibody titers towards both homologous SARS-CoV-2 and a variant harboring the N501Y mutation shared by B1.1.7, B.1.351 and P.1 variants. Furthermore, passive transfer of vaccination-induced antibodies protected naive mice against heterologous viral challenge. NE/IVT DI enables mucosal vaccination, and has the potential to improve the immune profile of a variety of SARS-CoV-2 vaccine candidates to provide effective cross-protection against future drift variants.

Efficacy of recombinant Marek’s disease virus vectored vaccines with computationally optimized broadly reactive antigen (COBRA) hemagglutinin insert against genetically diverse H5 high pathogenicity avian influenza viruses

The genetic and antigenic drift associated with the high pathogenicity avian influenza (HPAI) viruses of Goose/Guangdong (Gs/GD) lineage and the emergence of vaccine-resistant field viruses underscores the need for a broadly protective H5 influenza A vaccine. Here, we tested experimental vector herpesvirus of turkey (vHVT)-H5 vaccines containing either wild-type clade 2.3.4.4A-derived H5 inserts or computationally optimized broadly reactive antigen (COBRA) inserts with challenge by homologous and genetically divergent H5 HPAI Gs/GD lineage viruses in chickens. Direct assessment of protection was confirmed for all the tested constructs, which provided clinical protection against the homologous and heterologous H5 HPAI Gs/GD challenge viruses and significantly decreased oropharyngeal shedding titers compared to the sham vaccine. The cross reactivity was assessed by hemagglutinin inhibition (HI) and focus reduction assay against a panel of phylogenetically and antigenically diverse H5 strains. The COBRA-derived H5 inserts elicited antibody responses against antigenically diverse strains, while the wild-type-derived H5 vaccines elicited protection mostly against close antigenically related clades 2.3.4.4A and 2.3.4.4D viruses. In conclusion, the HVT vector, a widely used replicating vaccine platform in poultry, with H5 insert provides clinical protection and significant reduction of viral shedding against homologous and heterologous challenge. In addition, the COBRA-derived inserts have the potential to be used against antigenically distinct co-circulating viruses and future drift variants.

Next generation methodology for updating HA vaccines against emerging human seasonal influenza A(H3N2) viruses

While vaccines remain the best tool for preventing influenza virus infections, they have demonstrated low to moderate effectiveness in recent years. Seasonal influenza vaccines typically consist of wild-type influenza A and B viruses that are limited in their ability to elicit protective immune responses against co-circulating influenza virus variant strains. Improved influenza virus vaccines need to elicit protective immune responses against multiple influenza virus drift variants within each season. Broadly reactive vaccine candidates potentially provide a solution to this problem, but their efficacy may begin to wane as influenza viruses naturally mutate through processes that mediates drift. Thus, it is necessary to develop a method that commercial vaccine manufacturers can use to update broadly reactive vaccine antigens to better protect against future and currently circulating viral variants. Building upon the COBRA technology, nine next-generation H3N2 influenza hemagglutinin (HA) vaccines were designed using a next generation algorithm and design methodology. These next-generation broadly reactive COBRA H3 HA vaccines were superior to wild-type HA vaccines at eliciting antibodies with high HAI activity against a panel of historical and co-circulating H3N2 influenza viruses isolated over the last 15 years, as well as the ability to neutralize future emerging H3N2 isolates.

Selection, identification, and characterization of SARS-CoV-2 monoclonal antibody resistant mutants

The use of monoclonal neutralizing antibodies (mNAbs) is being actively pursued as a viable intervention for the treatment of Severe Acute Respiratory Syndrome CoV-2 (SARS-CoV-2) infection and associated coronavirus disease 2019 (COVID-19). While highly potent mNAbs have great therapeutic potential, the ability of the virus to mutate and escape recognition and neutralization of mNAbs represents a potential problem in their use for the therapeutic management of SARS-CoV-2. Studies investigating natural or mNAb-induced antigenic variability in the receptor binding domain (RBD) of SARS-CoV-2 Spike (S) glycoprotein, and their effects on viral fitness are still rudimentary. In this manuscript we described experimental approaches for the selection, identification, and characterization of SARS-CoV-2 monoclonal antibody resistant mutants (MARMs) in cultured cells. The ability to study SARS-CoV-2 antigenic drift under selective immune pressure by mNAbs is important for the optimal implementation of mNAbs for the therapeutic management of COVID-19. This will help to identify essential amino acid residues in the viral S glycoprotein required for mNAb-mediated inhibition of viral infection, to predict potential natural drift variants that could emerge upon implementation of therapeutic mNAbs, as well as vaccine prophylactic treatments for SARS-CoV-2 infection. Additionally, it will also enable the assessment of MARM viral fitness and its potential to induce severe infection and associated COVID-19 disease.

Identification of H3N2 NA and PB1-F2 genetic variants and their association with disease symptoms during the 2014-15 influenza season.

The 2014–15 influenza season saw the emergence of an H3N2 antigenic drift variant that formed the 3C.2a HA clade. Whole viral genomes were sequenced from nasopharyngeal swabs of ninety-four patients with confirmed influenza A virus infection and primary human nasal epithelial cell cultures used to efficiently isolate H3N2 viruses. The isolates were classified by HA clade and the presence of a new set of co-selected mutations in NA (a glycosylation site, NAg+) and PB1-F2 (H75P). The NA and PB1-F2 mutations were present in a subset of clade 3C.2a viruses (NAg+F2P), which dominated during the subsequent influenza seasons. In human nasal epithelial cell cultures, a virus with the novel NAg+F2P genotype replicated less well compared with a virus with the parental genotype. Retrospective analyses of clinical data showed that NAg+F2P genotype viruses were associated with increased cough and shortness of breath in infected patients.

Cocirculation of Swine H1N1 Influenza A Virus Lineages in Germany.

The genome analysis of 328 H1N1 swine influenza virus isolates collected in a 13-year long-term swine influenza surveillance in Germany is reported. Viral genomes were sequenced with the Illumina next-generation sequencing technique and conventional Sanger methods. Phylogenetic analyses were conducted with Bayesian tree inference. The results indicate continued prevalence of Eurasian avian swine H1N1 but also emergence of a novel H1N1 reassortant, named Schneiderkrug/2013-like swine H1N1, with human-like hemagglutinin and avian-like neuraminidase and internal genes. Additionally, the evolution of an antigenic drift variant of A (H1N1) pdm09 was observed, named Wachtum/2014-like swine H1N1. Both variants were first isolated in northwest Germany, spread to neighboring German states and reached greater proportions of the H1N1 isolates of 2014 and 2015. The upsurge of Wachtum/2014-like swine H1N1 is of interest as this is the first documented persistent swine-to-swine spread of A (H1N1) pdm09 in Germany associated with antigenic variation. Present enzootic swine influenza viruses in Germany now include two or more co-circulating, antigenically variant viruses of each of the subtypes, H1N1 and H1N2.

Emergence of Drift Variants That May Affect COVID-19 Vaccine Development and Antibody Treatment.

New coronavirus (SARS-CoV-2) treatments and vaccines are under development to combat COVID-19. Several approaches are being used by scientists for investigation, including (1) various small molecule approaches targeting RNA polymerase, 3C-like protease, and RNA endonuclease; and (2) exploration of antibodies obtained from convalescent plasma from patients who have recovered from COVID-19. The coronavirus genome is highly prone to mutations that lead to genetic drift and escape from immune recognition; thus, it is imperative that sub-strains with different mutations are also accounted for during vaccine development. As the disease has grown to become a pandemic, B-cell and T-cell epitopes predicted from SARS coronavirus have been reported. Using the epitope information along with variants of the virus, we have found several variants which might cause drifts. Among such variants, 23403A>G variant (p.D614G) in spike protein B-cell epitope is observed frequently in European countries, such as the Netherlands, Switzerland, and France, but seldom observed in China.

Features of Epidemic Process of Influenza and its Etiology in the Countries of the Northern and Southern Hemispheres in the Period of Circulation of Pandemic Virus A(H1N1)pdm09 (According to WHO)

Relevance. Influenza is characterized by global distribution and the difference in its seasonality in countries with temperate and tropical climates. The importance of studying antigenic variation of influenza viruses due to the fact that changes in the antigenic structure is an evolutionary mechanism of adaptation of the virus to ensure its survival and cause annual epidemics.Aims. The Aim of this study was to identify the peculiarities of the geographical spread of influenza (seasonal), etiology and the rate of antigenic variability of influenza viruses A and B.Materials and methods. Based on data from WHO Reference research centers, information was collected on circulating influenza virus strains from 1975 A(H3N2), 1977 A(H1N1)pdm09 and type B of the Yamagata and Victoria lines from 1987 to 2019, as well as data on the number of all identified influenza viruses and individual strains circulating in the Northern and Southern hemispheres from 2008 to 2018.Results and discussion. Analysis of the global spread of influenza, its etiology and antigenic variability of viruses, according to WHO, showed that the influenza A(H1N1)pdm09 virus was the main causative agent of epidemics and regional outbreaks in seasons of high influenza activity in all countries except the United States and Canada, where influenza A(H3N2) and B viruses dominated in countries with severe seasonality, the change of season led to a change in the etiology of influenza, and in tropical countries, the A(H1N1)pdm09 virus more often remained dominant in all seasons of the year.Conclusions. The pronounced seasonality of influenza in Northern countries and its absence in tropical countries, where regional outbreaks prevailed in all seasons of the year, were confirmed. Low antigenic variability of influenza A(H1N1)pdm09 strains was confirmed, and the highest – A(H3N2). Among influenza B strains in the Victoria line had less antigenic variability, because the duration of its circulation before the appearance of a new drift variant was longer than that of the Yamagata line. The tendency to increase the total duration of circulation of influenza viruses B/Victoria, A(H1N1)pdm09 and B/Yamagata due to increased circulation before the emergence of new drift variants is shown.

Evolution of influenza viruses based on sensitivity to temperature of replication

Introduction. The assessment of the ability of influenza viruses to replication at temperature conditions beyond optimal values approaches us to understanding the laws of their evolutionary variability. The temperature range for the reproduction of epidemic viruses is also an important indicator for choosing a rational strategy for producing attenuated reassortants for a live influenza vaccine.The purpose of the study is a retrospective analysis of the biological properties of influenza viruses from various pandemic and epidemic cycles based on their ability to replicate at temperatures beyond optimal values.Materials and methods. We studied 234 strains of human influenza A and B viruses that caused epidemics in the 20th – 21st centuries. The infectious activity of viruses at different incubation temperatures was determined in developing chicken embryos. The temperature sensitivity and cold resistance of viruses replication were estimated as a difference of infectious titers at the optimum and raised or lowered incubation temperatures.Results. Data from a retrospective study indicate that the range of sensitivity to replication temperature during the natural drift of influenza A and B pathogens is subject to regular variability that has a cyclic character.Discussion. To assess the evolution and epidemic potential of influenza viruses, it is important not only to register a change in their antigenic properties but also to take into account the temperature sensitivity of the reproduction. Both of these properties contribute to the manifestation of the virulence of the virus. Prolonged circulation of temperature-sensitive viruses can be a prerequisite for the appearance of a radically new drift variant and even shift.Conclusion. The analysis of the variability of the biological properties of influenza viruses approaches to the comprehension of possible ways of their evolution, that contributes to the development of rational methods for preventing the spread of viruses and the incidence caused by them.

Antibody-dependent cell-mediated cytotoxicity antibody responses to inactivated and live-attenuated influenza vaccination in children during 2014–15

BackgroundSeasonal influenza vaccines aim to induce strain-specific neutralizing antibodies. Non-neutralizing antibodies may be more broadly cross-reactive and still protect through mechanisms including antibody-dependent cell-mediated cytotoxicity (ADCC). Influenza vaccines may stimulate ADCC antibodies in adults, but whether they do so in children is unknown. Here we examined how vaccination affects cross-reactive ADCC antibody responses in children after receipt of inactivated trivalent vaccine (IIV3) or quadrivalent live-attenuated vaccine (LAIV4). MethodsChildren aged 5–17 were recruited in fall 2014 to provide pre- and post-vaccination serum samples. Children aged 5–9 received LAIV4 based on then-current recommendation, and older children were randomly assigned to IIV3 or LAIV4. We used microtiter-plate-based flow cytometry with an NK cell line to examine ADCC antibody responses to the 2014–15 H3N2 vaccine component (A/Texas/50/2012 [TX12]) and a drifted strain, A/Switzerland/9715293/2013 (SW13). Responses were stratified by two-season (2013–14 and 2014–15) vaccine sequence. ResultsEighty-five children received LAIV4 and 45 received IIV3. Prevaccination ADCC activity was highest in children who had received any vaccine in the prior season. Increase in ADCC antibody responses against the vaccine strain TX12 following vaccination was greatest for participants who received IIV3 in 2014–15 and LAIV4 in the prior season (geometric mean fold rise [MFR] = 1.6, 95% CI.1.23–2.11). This group also had a detectable ADCC response to the drifted SW13 strain. There was a modest ADCC response against SW13 in LAIV4 recipients who were unvaccinated in the previous season (MFR = 1.18, 95% CI 1.10–1.25). There were no significant changes in 2014–15 ADCC response to vaccination among children who had received IIV3 in 2013–14. ConclusionsVaccinating children with IIV3 after prior receipt of LAIV4 generated a modest increase in ADCC antibodies, including some cross-reactivity with an emerging drift variant. Other vaccine-induced ADCC responses were minimal and not affected by vaccine type or sequence.