Variation by lineage in serum antibody responses to influenza B virus infections

A Phase 1/2 Randomized Study to Evaluate the Safety, Tolerability, and Immunogenicity of Nucleoside-Modified Messenger RNA Influenza Vaccines in Healthy Adults

Background/Objectives: Circulating influenza strains antigenically differing from vaccine antigens increase disease burden by decreasing vaccine efficacy. Nucleoside-modified mRNA (modRNA) influenza vaccines may facilitate rapid production allowing later antigen selection and improved antigenic similarity compared to circulating strains. We studied different influenza modRNA vaccine (IRV) formulations and dose levels. Methods: This phase 1/2 randomized study evaluated IRV safety/tolerability and immunogenicity in healthy 18- through 85-year-olds. Based on safety and immunogenicity for different IRV doses, schedules, and valencies versus the quadrivalent influenza vaccine (QIV; Fluzone High-Dose Quadrivalent, Sanofi Pasteur) in phase 1 (65-85-year-olds), quadrivalent IRV (qIRV) was further evaluated in 65- through 85-year-olds and 18- through 64-year-olds in phase 2, leading to phase 3 dose selection. Results: Phase 1 (65-85-year-olds) safety/tolerability and immunogenicity findings supported qIRV 30-µg and 60-µg phase 2 assessment (18-85-year-olds, N = 610). qIRV was well tolerated. Injection site pain was the most frequently reported local reaction. Reactogenicity event incidences ≤ 7 days postvaccination for qIRV were generally higher versus QIV, observed more frequently in 18- through 64-year-olds than 65- through 85-year-olds, and showed dose-related trends (60 μg > 30 μg). qIRV and QIV adverse event profiles in 65- through 85-year-olds were similar. There were higher postvaccination hemagglutination inhibition assay geometric mean titers and fold rises and seroconversion rates observed with qIRV versus QIV for A strains, with no consistent pattern for B strains. Cell-mediated immune responses to qIRV by Day 7 showed overall higher T-cell responses against all strains versus QIV. Antibody and cell-mediated immune responses showed comparable trends across qIRV doses in 18- through 85-year-olds; a dose-related pattern was observed in 65- through 85-year-olds (60 μg > 30 μg). Conclusions: Phase 3 investigations of qIRV 60 µg in older adults and qIRV 30 µg in younger adults are warranted (ClinicalTrials.gov Identifier: NCT05052697).

Development and evaluation of mosaic VLPs vaccine for enhanced broad-Spectrum immunity against influenza B virus lineages in mice

Influenza B virus (IBV) causes annual respiratory outbreaks, posing significant public health challenges. Traditional vaccines are limited in their effectiveness by antigenic drift and strain mismatches. This study introduces innovative mosaic virus-like particle (VLP) vaccines designed to present a broader range of epitopes, aiming for broad-spectrum immunity against both B/Victoria (BV) and B/Yamagata (BY) IBV lineages in mice. Two mosaic hemagglutinin (HAM) proteins were incorporated into VLPs, mimicking the morphology and size of the virus. Notably, the BV component of our mosaic VLPs demonstrated significant cross-reactivity against the BY strain, surpassing a commercial quadrivalent inactivated influenza vaccine (QIV) in generating broad immune responses. Immunogenicity and efficacy assessments in mice revealed that the mosaic VLPs induced Th1/Th2 cytokine responses and provided effective protection against homologous IBV challenge, notably reducing lung damage. This study highlights the potential of mosaic VLPs in universal influenza B vaccine development and emphasizes the importance of T cell immunity in influenza vaccine design.

Delay of innate immune responses following influenza B virus infection affects the development of a robust antibody response in ferrets

Due to its natural influenza susceptibility, clinical signs, transmission, and similar sialic acid residue distribution, the ferret is the primary animal model for human influenza research. Antibodies generated following infection of ferrets with human influenza viruses are used in surveillance to detect antigenic drift and cross-reactivity with vaccine viruses and circulating strains. Inoculation of ferrets, with over 1,500 human clinical influenza isolates (1998-2019) resulted in lower antibody responses (HI <1:160) to 86% (387 out of 448) influenza B viruses (IBVs) compared to 2.7% (30 out of 1,094) influenza A viruses (IAVs). Here, we show that the immune responses in ferrets inoculated with IBV were delayed and reduced compared to IAV. Innate gene expression in the upper respiratory tract and blood indicated that IAV generated a strong inflammatory response, including an early activation of the interferon (IFN), whereas IBV elicited a delayed and reduced response. Serum levels of cytokines and IFNs were all much higher following IAV infection than IBV infection. Pro-inflammatory, IFN, TH1/TH2, and T-effector proteins were significantly higher in sera of IAV-infected than IBV-infected ferrets over 28 days following the challenge. Serum levels of Type-I/II/III IFNs were detected following IAV infection throughout this period, whereas Type-III IFN was only late for IBV. An early increase in IFN-lambda corresponded to gene expression following IAV infection. Reduced innate immune responses following IBV infection reflected the subsequent delayed and reduced serum antibodies. These findings may help in understanding the antibody responses in humans following influenza vaccination or infection and consideration of potential addition of innate immunomodulators to overcome low responses.

IMPORTANCE

The ferret is the primary animal model for human influenza research. Using a ferret model, we studied the differences in both innate and adaptive immune responses following infection with influenza A and B viruses (IAV and IBV). Antibodies generated following infection of ferrets is used for surveillance assays to detect antigenic drift and cross-reactivity with vaccine viruses and circulating influenza strains. IAV infection of ferrets to generate these reagents resulted in a strong antibody response, but IBV infection generated weak antibody responses. In this study using influenza-infected ferrets, we found that IAV resulted in an early activation of the interferon (IFN) and pro-inflammatory response, whereas IBV showed a delay and reduction in these responses. Serum levels of IFNs and other cytokines or chemokines were much higher in ferrets following IAV infection. These reduced innate responses were reflected the subsequent delayed and reduced antibody responses to IBV in the sera. These findings may help in understanding low antibody responses in humans following influenza B vaccination and infection and may warrant the use of innate immunomodulators to overcome these weak responses.

The added value of serologic testing: A comparison of influenza incidence among pregnant persons based on molecular-based surveillance versus serologic testing

BACKGROUND

We examined the added value of serologic testing for estimating influenza virus infection incidence based on illness surveillance with molecular testing versus periodic serologic testing.

METHODS

Pregnant persons unvaccinated against influenza at <28 weeks gestation were enrolled before the 2017 and 2018 influenza seasons in Peru and Thailand. Blood specimens were collected at enrollment and ≤14 days postpartum for testing by hemagglutination inhibition assay for antibodies against influenza reference viruses. Seroconversion was defined as a ≥4-fold rise in antibody titers from enrollment to postpartum with the second specimen's titer of ≥40. Throughout pregnancy, participants responded to twice weekly surveillance contacts asking about influenza vaccination and influenza-like symptoms (ILS). A mid-turbinate swab was collected with each ILS episode for influenza real-time reverse transcription polymerase chain reaction (rRT-PCR).

RESULTS

Of 1,466 participants without evidence of influenza vaccination during pregnancy, 296 (20.2%) had evidence of influenza virus infections. Fifteen (5.1%) were detected by rRT-PCR only, 250 (84.4%) by serologic testing only, and 31 (10.5%) by both methods.

CONCLUSIONS

Influenza virus infections during pregnancy occurred in 20% of cohort participants; >80% were not detected by a broad illness case definition coupled with rRT-PCR.

A Multiseason Randomized Controlled Trial of Advax-Adjuvanted Seasonal Influenza Vaccine in Participants With Chronic Disease or Older Age

BACKGROUND

The aim of the current study was to determine the safety and immunogenicity of trivalent inactivated influenza vaccine (TIV) alone or formulated with Advax delta inulin adjuvant in those who were older (aged >60 years) or had chronic disease.

METHODS

Over 4 consecutive years from 2008 through 2011, adult participants with chronic disease or >60 years of age were recruited into a randomized controlled study to assess the safety, tolerability and immunogenicity of Advax-adjuvanted TIV (TIV + Adj) versus standard TIV. The per-protocol population with ≥1 postbaseline measurement of influenza antibodies comprised 1297 participants, 447 in the TIV and 850 in the TIV + Adj) group.

RESULTS

No safety issues were identified. Variables negatively affecting vaccine responses included obesity and diabetes mellitus. Advax adjuvant had a positive impact on anti-influenza immunoglobulin M responses and on H3N2 and B strain seropositivity as assessed by hemagglutination inhibition.

CONCLUSIONS

TIV + Adj was safe and well tolerated in individuals with chronic disease. There is an ongoing need for research into improved influenza vaccines for high-risk populations.

CLINICAL TRIALS REGISTRATION

Australia New Zealand Clinical Trial Registry: ACTRN 12608000364370.

Immune imprinting in early life shapes cross-reactivity to influenza B virus haemagglutinin

Influenza exposures early in life are believed to shape future susceptibility to influenza infections by imprinting immunological biases that affect cross-reactivity to future influenza viruses. However, direct serological evidence linked to susceptibility is limited. Here we analysed haemagglutination-inhibition titres in 1,451 cross-sectional samples collected between 1992 and 2020, from individuals born between 1917 and 2008, against influenza B virus (IBV) isolates from 1940 to 2021. We included testing of 'future' isolates that circulated after sample collection. We show that immunological biases are conferred by early life IBV infection and result in lineage-specific cross-reactivity of a birth cohort towards future IBV isolates. This translates into differential estimates of susceptibility between birth cohorts towards the B/Yamagata and B/Victoria lineages, predicting lineage-specific birth-cohort distributions of observed medically attended IBV infections. Our data suggest that immunological measurements of imprinting could be important in modelling and predicting virus epidemiology.

The Influenza B Virus Victoria and Yamagata Lineages Display Distinct Cell Tropism and Infection-Induced Host Gene Expression in Human Nasal Epithelial Cell Cultures

Understanding Influenza B virus infections is of critical importance in our efforts to control severe influenza and influenza-related diseases. Until 2020, two genetic lineages of influenza B virus-Yamagata and Victoria-circulated in the population. These lineages are antigenically distinct, but the differences in virus replication or the induction of host cell responses after infection have not been carefully studied. Recent IBV clinical isolates of both lineages were obtained from influenza surveillance efforts of the Johns Hopkins Center of Excellence in Influenza Research and Response and characterized in vitro. B/Victoria and B/Yamagata clinical isolates were recognized less efficiently by serum from influenza-vaccinated individuals in comparison to the vaccine strains. B/Victoria lineages formed smaller plaques on MDCK cells compared to B/Yamagata, but infectious virus production in primary human nasal epithelial cell (hNEC) cultures showed no differences. While ciliated epithelial cells were the dominant cell type infected by both lineages, B/Victoria lineages had a slight preference for MUC5AC-positive cells, and B/Yamagata lineages infected more basal cells. Finally, while both lineages induced a strong interferon response 48 h after infection of hNEC cultures, the B/Victoria lineages showed a much stronger induction of interferon-related signaling pathways compared to B/Yamagata. This demonstrates that the two influenza B virus lineages differ not only in their antigenic structure but also in their ability to induce host innate immune responses.

The Influenza B Virus Victoria and Yamagata Lineages Display Distinct Cell Tropism and Infection Induced Host Gene Expression in Human Nasal Epithelial Cell Cultures

Understanding Influenza B virus infections is of critical importance in our efforts to control severe influenza and influenza-related disease. Until 2020, two genetic lineages of influenza B virus - Yamagata and Victoria - circulated in the population. These lineages are antigenically distinct but differences in virus replication or the induction of host cell responses after infection have not been carefully studied. Recent IBV clinical isolates of both lineages were obtained from influenza surveillance efforts of the Johns Hopkins Center of Excellence in Influenza Research and Response and characterized in vitro . B/Victoria and B/Yamagata clinical isolates were recognized less efficiently by serum from influenza-vaccinated individuals in comparison to the vaccine strains. B/Victoria lineages formed smaller plaques on MDCK cells compared to B/Yamagata, but infectious virus production in primary human nasal epithelial cell (hNEC) cultures showed no differences. While ciliated epithelial cells were the dominant cell type infected by both lineages, B/Victoria lineages had a slight preference for MUC5AC-positive cells, while B/Yamagata lineages infected more basal cells. Finally, while both lineages induced a strong interferon response 48 hours after infection of hNEC cultures, the B/Victoria lineages showed a much stronger induction of interferon related signaling pathways compared to B/Yamagata. This demonstrates that the two influenza B virus lineages differ not only in their antigenic structure but in their ability to induce host innate immune responses.

Mild and asymptomatic influenza B virus infection among unvaccinated pregnant persons: Implication for effectiveness of non-pharmaceutical intervention and vaccination to prevent influenza

BACKGROUND

We estimated symptomatic and asymptomatic influenza infection frequency in community-dwelling unvaccinated pregnant persons to inform risk communication.

METHODS

We collected residue sera from multiple antenatal-care blood draws during October 2016-April 2017. We determined influenza infection as seroconversion with ≥ 4-fold rise in antibody titers between any two serum samples by improved hemagglutinin-inhibition assay including ether-treated B antigens. The serology data were linked to the results of nuclei acid testing (rRT-PCR) based on acute respiratory illness (ARI) surveillance.

RESULTS

Among all participants, 43 %(602/1384) demonstrated serology and/or rRT-PCR evidenced infection, and 44 %(265/602) of all infections were asymptomatic. ARI-associated rRT-PCR testing identified only 10 %(61/602) of total infections. Only 1 %(5/420) of the B Victoria cases reported ARI and had a rRT-PCR positive result, compared with 33 %(54/165) of the H3N2 cases. Among influenza ARI cases with multiple serum samples, 19 %(11/58) had seroconversion to a different subtype prior to the illness.

CONCLUSIONS

The incidence of influenza B infection in unvaccinated pregnant persons is under-estimated substantially. Non-pharmaceutical intervention may have suboptimal effectiveness in preventing influenza B transmission due to the less clinical manifestation compared to influenza A. The findings support maternal influenza vaccination to protect pregnant persons and reduce consequent household transmission.