Hemagglutination Inhibition Responses Research Articles

Impact of Pre-Existing Immunity and Age on Antibody Responses to Live Attenuated Influenza Vaccine.

Live attenuated influenza vaccines (LAIV) typically induce a poor hemagglutination inhibition (HI) response, which is the standard correlate of protection for inactivated influenza vaccines. The significance of the HI response is complicated because the LAIV vaccine primarily induces the local mucosal immune system, while the HI assay measures the circulating serum antibody response. However, age and pre-existing immunity have been identified as important factors affecting LAIV immunogenicity. This study aimed to extend our understanding of LAIV-induced immunity, particularly, the impact age and pre-existing immunity have on eliciting functional and neutralising antibody responses in paediatric and adult populations vaccinated with LAIV. Thirty-one children and 26 adults were immunized with the trivalent LAIV during the 2013-2014 influenza season in Norway. Children under 9 years received a second dose of LAIV 28 days after the first dose. Blood samples were collected pre- and post-vaccination. HI, microneutralization (MN) and enzyme-linked lectin assay for neuraminidase (NA) antibodies were measured against the vaccine strains. IgG antibody avidity against hemagglutinin (HA) and NA proteins from the vaccine strains was also assessed. Significant correlations were observed between HI and MN responses to A/California/7/2009 (A/H1N1)pdm09-like strain and B/Massachusetts/2/2012-like strain, suggesting that MN is a potential immunological correlate for LAIV. However, the relationship between recipient age (or priming status) and serological response varied between vaccine strains. There was a notable increase in HI and MN responses in all cohorts except naive children against the H1N1 strain, where most recipients had responses below the protective antibody threshold. NAI responses were generally weak in naive children against all vaccine strains compared with adults or antigen-primed children. Post-vaccination antibody avidity increased only in primed children below nine years of age against the A/H1N1 strain. Overall, our findings indicate that LAIV elicits functional and neutralizing antibody responses in both naive and antigen experienced cohorts, however, the magnitude and kinetics of the response varies between vaccine strains.

Metabolomic Signatures Differentiate Immune Responses in Avian Influenza Vaccine Recipients.

Avian influenza viruses pose significant risk to human health. Vaccines targeting the hemagglutinin of these viruses are poorly immunogenic without the use of adjuvants. Twenty healthy men and women (18-49 years of age) were randomized to receive 2 doses of inactivated influenza A/H5N1 vaccine alone (IIV) or with AS03 adjuvant (IIV-AS03) 1 month apart. Urine and serum samples were collected on day 0 and on days 1, 3, and 7 following first vaccination and subjected to metabolomics analyses to identify metabolites, metabolic pathways, and metabolite clusters associated with immunization. Seventy-three differentially abundant (DA) serum and 88 urine metabolites were identified for any postvaccination day comparison. Pathway analysis revealed enrichment of tryptophan, tyrosine, and nicotinate metabolism in urine and serum among IIV-AS03 recipients. Increased urine abundance of 4-vinylphenol sulfate on day 1 was associated with serologic response based on hemagglutination inhibition responses. In addition, 9 DA urine metabolites were identified in participants with malaise compared to those without. Our findings suggest that tryptophan, tyrosine, and nicotinate metabolism are upregulated among IIV-AS03 recipients compared with IIV alone. Metabolites within these pathways may serve as measures of immunogenicity and may provide mechanistic insights for adjuvanted vaccines. NCT01573312.

Heterologous prime-boost H1N1 vaccination exacerbates disease following challenge with a mismatched H1N2 influenza virus in the swine model

Influenza A viruses (IAVs) pose a significant threat to both human and animal health. Developing IAV vaccine strategies able to elicit broad heterologous protection against antigenically diverse IAV strains is pivotal in effectively controlling the disease. The goal of this study was to examine the immunogenicity and protective efficacy of diverse H1N1 influenza vaccine strategies including monovalent, bivalent, and heterologous prime-boost vaccination regimens, against a mismatched H1N2 swine influenza virus. Five groups were homologous prime-boost vaccinated with either an oil-adjuvanted whole-inactivated virus (WIV) monovalent A/swine/Georgia/27480/2019 (GA19) H1N2 vaccine, a WIV monovalent A/sw/Minnesota/A02636116/2021 (MN21) H1N1 vaccine, a WIV monovalent A/California/07/2009 (CA09) H1N1, a WIV bivalent vaccine composed of CA09 and MN21, or adjuvant only (mock-vaccinated group). A sixth group was prime-vaccinated with CA09 WIV and boosted with MN21 WIV (heterologous prime-boost group). Four weeks post-boost pigs were intranasally and intratracheally challenged with A/swine/Georgia/27480/2019, an H1N2 swine IAV field isolate. Vaccine-induced protection was evaluated based on five critical parameters: (i) hemagglutination inhibiting (HAI) antibody responses, (ii) clinical scores, (iii) virus titers in nasal swabs and respiratory tissue homogenates, (iv) BALf cytology, and (v) pulmonary pathology. While all vaccination regimens induced seroprotective titers against homologous viruses, heterologous prime-boost vaccination failed to enhance HAI responses against the homologous vaccine strains compared to monovalent vaccine regimens and did not expand the scope of cross-reactive antibody responses against antigenically distinct swine and human IAVs. Mismatched vaccination regimens not only failed to confer clinical and virological protection post-challenge but also exacerbated disease and pathology. In particular, heterologous-boosted pigs showed prolonged clinical disease and increased pulmonary pathology compared to mock-vaccinated pigs. Our results demonstrated that H1-specific heterologous prime-boost vaccination, rather than enhancing cross-protection, worsened the clinical outcome and pathology after challenge with the antigenically distant A/swine/Georgia/27480/2019 strain.

An Oil-in-Water adjuvant significantly increased influenza A/H7N9 split virus Vaccine-Induced circulating follicular helper T (cTFH) cells and antibody responses

BackgroundUnadjuvanted A/H7N9 vaccines are poorly immunogenic. The immune response is improved with the addition of MF59, an oil-in-water adjuvant. However, the cellular immunologic responses of MF59-adjuvanted A/H7N9 vaccine are not fully understood. Methods37 participants were vaccinated with 2 doses of 2013 influenza A/H7N9 vaccine (at Days 1 and 21) with or without MF59 and enrolled in an immunology substudy. Responses were assessed at multiple timepoints (Days 0, 8, 21, 29, and 42) for hemagglutination inhibition (HAI) and neutralizing antibody (Neut) assays, memory B cell responses by enzyme-linked ImmunoSpot; circulating follicular helper T cells (cTFH) and CD4 + T cells by intracellular cytokine staining. ResultsMF59-adjuvanted influenza A/H7N9 vaccine induced significantly higher hemagglutination inhibition (HAI) and neutralizing antibody (Neut) responses when compared to unadjuvanted vaccine. The adjuvanted vaccine elicited significantly higher levels of Inducible T-cell Co-Stimulator (ICOS) expression by CXCR3+CXCR5+CD4+ cTFH cells, compared to unadjuvanted vaccine. The magnitude of increase in cTFH cells (from baseline to Day 8) and in IL-21 expressing CD154+CD4+ T cells (from baseline to Days 8 and 21) correlated with HAI (at Day 29) and Neut antibody (at Days 8 and 29) titers. The increase in frequency of IL-21 expressing CD154+CD4+T cells (from baseline to Day 21) correlated with memory B cell frequency (at Day 42). ConclusioncTFH activation is associated with HAI and Neut responses in recipients of MF59-adjuvanted influenza A/H7N9 vaccine relative to unadjuvanted vaccine. Future studies should focus on optimizing the cTFH response and use cTFH as an early biomarker of serological response to vaccination.This trial was registered at clinicaltrials.gov, trial number NCT01938742.

99. Immune Responses to Influenza Vaccines in Children and Young Adults

BackgroundImmune responses to influenza vaccines (IV) are influenced by pre-existing antibodies to vaccine components. Immune responses to vaccines were evaluated following vaccination with quadrivalent egg-based live-attenuated influenza vaccine (LAIV4) and cell-culture inactivated influenza vaccine (ccIIV4).MethodsRacially diverse (48.0% non-white), healthy, community-dwelling children and young adults aged 4-21 years (median, 18.3 years) were randomized 1:1 in blocks of 4 to receive intramuscular ccIIV4 (Flucelvax: n=100) or nasal LAIV4 (FluMist: n=98); baseline demographics were similar between groups. Blood was drawn at day 0 pre-vaccination and at day 28 (21-35 days) post vaccination. Hemagglutination inhibition (HI) assays against egg-grown A/H1N1, A/H3N2, both vaccine B/strains and cell-grown A/H3N2 antigens were conducted. Geometric mean titers (GMT) and geometric mean fold rise (GMFR) in titers were analyzed. ResultsDay 0 GMTs were similar for LAIV4 and ccIIV4. Day 28 GMTs were higher for ccIIV4 (p< 0.05) and increased following vaccination for all 5 antigens (p< 0.05) except B/Phuket following LAIV4. The GMFR range was 2.4 to 3.0 for ccIIV4 and 1.0 to 1.3 for LAIV4. In linear regression controlling for age and prior season vaccination for both vaccines, baseline titers inversely predicted GMFR. The GMFR to A/H3N2 cell-grown and egg-grown antigens were similar within vaccine type.Figure 1. Day 0 and Day 28 A(H1N1) titers for ccIIV4Figure 2. Day 0 and Day 28 A(H1N1) titers for LAIV4ConclusionThe HI response to ccIIV4 was greater than LAIV4 in this study of mostly older children. Day 0 HI titers were 1) a significant determinant of GMFR; 2) the strongest predictors of day 28 GMFR; and 3) more highly correlated (negatively) with GMFR following ccIIV4 than LAIV4. For both IV, the GMFR for cell-grown and egg-grown A/H3N2 antigens did not differ within IV type. Future studies incorporating immunoglobulin and cellular immune responses may delineate differences between these IV types not observable through HI assays. Disclosures Mary Patricia Nowalk, PhD, Merck & Co., Inc. (Grant/Research Support) Richard K. Zimmerman, MA;MD;MPH;MS, Sanofi Pasteur (Research Grant or Support) Judith M. Martin, MD, Merck Sharp and Dohme (Consultant)

Phase III: Randomized observer-blind trial to evaluate lot-to-lot consistency of a new plant-derived quadrivalent virus like particle influenza vaccine in adults 18–49 years of age

BackgroundThe global reliance on eggs to produce most influenza vaccines has several limitations and new approaches to influenza vaccine production are needed. Herein we describe a phase 3, lot-to-lot consistency trial (NCT03321968) of a quadrivalent, recombinant, virus-like particle (VLP) influenza vaccine produced in plants. This platform is based on transient expression of proteins in Nicotiana benthamiana and yields VLPs bearing hemagglutinin (HA) protein trimers that are combined in a quadrivalent vaccine (QVLP). MethodsThe HAs targeted in this study were A/California/07/2009 H1N1, A/Hong Kong/4801/2014 H3N2, B/Brisbane/60/08 and B/Phuket/3073/2013: recommended for the 2016–2017 Northern Hemisphere season. Healthy adults 18–49 years of age (n = 1200) were randomized 1:1:1 to receive a 0.5 mL intramuscular injection of QVLP (30 μg HA/strain) from three sequential lots. Local and systemic reactions were monitored for 21 days post-vaccination and blood was collected pre-vaccination and at day 21 (D21) after vaccination to measure hemagglutination inhibition (HI) antibodies. ResultsSubject demographics were similar between groups and compliance with study procedures was 96.3%. The study population was 54.8% female, the mean age (±SD) was 29.9 ± 9.01 and the racial distribution was 77.8% Caucasian, 15.6% Asian, 5.8% Black/African American and 0.8% other. The HI responses met the Center for Biologics Evaluation and Research criteria for seroconversion (SCR ≥ 40%) and seroprotection rates (SPR ≥ 70%). The geometric mean fold rise in HI titers was ≥ 2.5 for all 4 strains for each lot. Lot-to-lot consistency was met with the 95% confidence intervals of the D21 mean geometric titre ratios falling between 0.67 and 1.5 for all four strains. No safety concerns were identified. Solicited adverse events were generally mild and transient: typical for what is reported after inactivated influenza vaccines. ConclusionsThis study supported earlier findings of the safety profile and immunogenicity of the plant-derived QVLP and demonstrated the consistency with which it can be produced.

Immunogenicity and safety of different dose schedules and antigen doses of an MF59-adjuvanted H7N9 vaccine in healthy adults aged 65 years and older

BackgroundThe number of human influenza A (H7N9) infections has escalated since 2013 with high resultant mortality. We conducted a phase II, randomized, partially-blinded trial to evaluate the safety and immunogenicity of an MF59-adjuvanted inactivated, split virion, H7N9 influenza vaccine (H7N9 IIV) administered at various dose levels and schedules in older adults. Methods479 adults ≥ 65 years of age in stable health were randomized to one of six groups to receive either 3.75, 7.5 or 15 µg of influenza A/Shanghai/02/2013 (H7N9) IIV adjuvanted with MF59 given as a 3-dose series either on days 1, 28 and 168 or on days 1, 57 and 168. Immunogenicity was assessed using both hemagglutination inhibition (HAI) and microneutralization (MN) assays prior to and 28 days following each dose. Safety was assessed through 1 year following the last dose. ResultsSubjects in all groups had only modest immune responses, with the HAI GMT < 20 after the second vaccine dose and <29 after the third vaccine dose. HAI titers ≥ 40 were seen in <37% of subjects after the second dose and <49% after the third dose. There were no significant differences seen between the two dose schedules. MN titers followed similar patterns, although the titers were approximately two-fold higher than the HAI titers. Logistic regression modeling demonstrated no statistically significant associations between the immune responses and age, sex or body mass index whereas recent prior receipt of seasonal influenza vaccine significantly reduced the HAI response [OR 0.13 (95% CI 0.05, 0.33); p < 0.001]. Overall, the vaccine was well tolerated. Two mild potentially immune mediated adverse events occurred, lichen planus and guttate psoriasis. ConclusionsMF59-adjuvanted H7N9 IIV was only modestly immunogenic in the older adult population following three doses. There were no significant differences in antibody responses noted among the various antigen doses or the two dose schedules.

Study of Neuraminidase-Inhibiting Antibodies in Clinical Trials of Live Influenza Vaccines.

Background: Currently, the immunogenicity of influenza vaccines is assessed by detecting an increase of hemagglutination inhibition (HI) antibodies. As neuraminidase (NA)-based immunity may be significant in protecting against influenza infection, detection of neuraminidase inhibiting (NI) antibodies may improve the assessment of the immunogenicity of influenza vaccines. Methods: We investigated the immune response to NA in people after immunization with live influenza vaccines (LAIVs). A number of A/H7NX or A/H6NX viruses were used to detect NI antibodies, using an enzyme-linked lectin assay (ELLA). Results: Seasonal LAIV immunization stimulated an increase in NI antibodies not only to homologous A/H1N1 influenza, but also to A/H1N1pdm09 and A/H5N1 influenza. After A/17/California/09/38 (H1N1) pdm09 LAIV vaccination, there was no statistical relationship between post-vaccinated antibody seroconversion and two surface glycoproteins in serum samples obtained from the same individuals (p = 0.24). Vaccination with LAIV of H5N2, H2N2, H7N3, and H7N9 subtypes led to 7%–29.6% NI antibody seroconversions in the absence of HI antibody conversions. There was relatively low coordination of hemagglutinin (HA) and NA antibody responses (r = 0.24–0.59). Conclusions: The previously noted autonomy for HI and NI immune responses was confirmed when assessing the immunogenicity of LAIVs. Combining the traditional HI test with the detection of NI antibodies can provide a more complete assessment of LAIV immunogenicity.

A novel combination of intramuscular vaccine adjuvants, nanoemulsion and CpG produces an effective immune response against influenza A virus

BackgroundVaccination is the most effective approach to prevent infection with highly pathogenic avian influenza (HPAI). Adjuvants are often used to induce effective immune responses and overcome the immunological weakness of recombinant HPAI antigens. Given the logistical challenges of immunization to HPAI during pandemic situations, vaccines administered via the intramuscular (I.M.) route would be of value. MethodsA new formulation of nanoemulsion adjuvant (NE02) suitable for I.M. vaccination was developed. This NE02 was evaluated alone and in combination with CpG to develop H5 immune responses in mouse and ferret models. Measures of recombinant H5 (rH5) specific immunity evaluated included serum IgG and IgG subclasses, bronchoalveolar lavage fluid IgA, and cytokines. The activation of NF-kB was also analyzed. The efficacy of the vaccine was assessed by performing hemagglutination inhibition (HAI), virus neutralization (VN) assays, and viral challenges in ferrets. ResultsI.M. vaccination with rH5-NE02 significantly increased rH5-specific IgG and protected ferrets in the viral challenge model providing complete protection and sterile immunity in all animals tested. Combining NE02 and CpG produced accelerated antibody responses and this was accompanied by an elevation of IFN-γ and IL-17 responses and the downregulation of IL-5. The combination also caused a synergistic effect on NF-kB activation. In immunized ferrets after viral challenge, the rH5-NE02 + CpG vaccine via I.M. achieved at least 75% and 88% seroconversion of HAI and VN antibody responses, respectively, and improved body temperature stabilization and weight loss over NE02 alone. ConclusionsThe I.M. injection of NE02 adjuvanted rH5 elicits strong and broad immune responses against H5 antigens and effectively protects animals from lethal H5 challenge. Combining this adjuvant with CpG enhanced immune responses and provided improvements in outcomes to viral challenge in ferrets. The results suggest that combinations of adjuvants may be useful to enhance H5 immune responses and improve protection against influenza infection.

Fc functional antibody responses to adjuvanted versus unadjuvanted seasonal influenza vaccination in community-dwelling older adults

BackgroundSeasonal influenza vaccination with a standard trivalent influenza vaccine (TIV) induces a modest, and cross-reactive, Fc functional antibody response in older adults. Recent improvements to influenza vaccines include a quadrivalent influenza vaccine (QIV) and a TIV adjuvanted with the squalene-based oil-in-water emulsion MF59. MethodsPre- and post-vaccination serum samples from older adults vaccinated with QIV (n = 27) and adjuvanted TIV (n = 44) were studied using hemagglutination inhibition (HAI) assays and dimeric Fc-gamma receptor IIIa binding ELISAs, as a surrogate of antibody-dependent cellular cytotoxicity (ADCC). ResultsWe found that the unadjuvanted QIV elicited a stronger HAI response against the H1N1 vaccine virus than the adjuvanted TIV. Post-vaccination levels of HA-specific ADCC antibodies were similar for older adults vaccinated with QIV and adjuvanted TIV. The ADCC response to influenza vaccination was largely determined by pre-vaccination or baseline levels of these antibodies, with older adults with low baseline levels of ADCC activity demonstrating greater post-vaccination rises. ConclusionsIn this cohort of community-dwelling older adults, the QIV was at least as good as the adjuvanted TIV in the induction of ADCC and HAI responses. Further studies on how these antibody responses translate to efficacy in preventing influenza infections are warranted.

2759. Immunogenicity of Inactivated Influenza Vaccines Given Early vs. Late After Pediatric Allogeneic Hematopoietic Cell Transplantation

BackgroundPediatric hematopoietic cell transplant (HCT) recipients often fail to have robust responses to influenza (flu) vaccine. We conducted a blinded phase II trial comparing high-dose (HD) trivalent inactivated vaccine (TIV) vs. standard dose (SD) quadrivalent inactivated vaccine (QIV).MethodsChildren 3–17 years old and 3–35 months post-allogeneic HCT were enrolled at 9 centers and randomized to either 2 doses of HD-TIV or SD-QIV during the 2016–2017 flu season. We compared immune responses by hemagglutination inhibition (HAI) from children 3–11 (early) vs. 12–35 (late) months (m) post-HCT to 3 common flu vaccine antigens, irrespective of vaccine type. HAI responses were evaluated at baseline (visit 1), 1 m post dose 1 (visit 2) and dose 2 (visit 3), and 7 m post dose 2 (visit 4). Geometric mean titers (GMT) were adjusted for baseline log-titer values.ResultsThirty-one children, median age 11 (7–15) years, were enrolled; 17 (55%) were immunized early and 14 (45%) late. Over 50% of patients had a potentially seroprotective (≥1:40) HAI titer at baseline, with no significant difference post-vaccination between early and late subjects. Table 1 compares early vs late subjects with HAI seroconversion (4-fold HAI titer rise). Post dose 1, late subjects, compared with early, had higher rates of seroconversion to all influenza strains. Post dose 2, early subjects, compared with late, had increased seroconversion. Late subjects had higher GMTs for H1N1 post dose 1 and 2, H3N2 after dose 1, and strain B/VIC post dose 1 and 2 (Figure 1). Although immunogenicity waned throughout flu season, higher seroconversion rates and GMT to H3N2 and strain B/VIC were retained in late subjects.ConclusionCompared with subjects in early post-HCT group, late post-HCT subjects had better flu vaccine immune responses as noted by higher GMT and HAI seroconversion. However, 2 doses seemed more beneficial in the early post-HCT group. Future analyses are underway, including comparing immunogenicity of HD vs. SD flu vaccine. DisclosuresJennifer E. Schuster, MD, Satchel Health: Shareholder Flor M. Munoz, M.D, Biocryst: Grant/Research Support; CDC: Research Grant; Moderna: Other Financial or Material Support, Safety Monitoring Board Member/Chair; NIH: Research Grant; Novavax: Research Grant; UP to Date: Author and Editor - Royalties, Other Financial or Material Support.

Baseline Serum Vitamin A and D Levels Determine Benefit of Oral Vitamin A&D Supplements to Humoral Immune Responses Following Pediatric Influenza Vaccination.

Maximizing vaccine efficacy is critical, but previous research has failed to provide a one-size-fits-all solution. Although vitamin A and vitamin D supplementation studies have been designed to improve vaccine efficacy, experimental results have been inconclusive. Information is urgently needed to explain study discrepancies and to provide guidance for the future use of vitamin supplements at the time of vaccination. We conducted a randomized, blinded, placebo-controlled study of influenza virus vaccination and vitamin supplementation among 2 to 8 (inclusive) year old children over three seasons, including 2015–2016 (n = 9), 2016–2017 (n = 44), and 2017–2018 (n = 26). Baseline measurements of vitamins A and D were obtained from all participants. Measurements were of serum retinol, retinol-binding protein (RBP, a surrogate for retinol), and 25-hydroxyvitamin D (25(OH)D). Participants were stratified into two groups based on high and low incoming levels of RBP. Children received two doses of the seasonal influenza virus vaccine on days 0 and 28, either with an oral vitamin supplement (termed A&D; 20,000 IU retinyl palmitate and 2000 IU cholecalciferol) or a matched placebo. Hemagglutination inhibition (HAI) antibody responses were evaluated toward all four components of the influenza virus vaccines on days 0, 28, and 56. Our primary data were from season 2016–2017, as enrollment was highest in this season and all children exhibited homogeneous and negative HAI responses toward the Phuket vaccine at study entry. Responses among children who entered the study with insufficient or deficient levels of RBP and 25(OH)D benefited from the A&D supplement (p < 0.001 for the day 28 Phuket response), whereas responses among children with replete levels of RBP and 25(OH)D at baseline were unaffected or weakened (p = 0.02 for the day 28 Phuket response). High baseline RBP levels associated with high HAI titers, particularly for children in the placebo group (baseline RBP correlated positively with Phuket HAI titers on day 28, r = 0.6, p = 0.003). In contrast, high baseline 25(OH)D levels associated with weak HAI titers, particularly for children in the A&D group (baseline 25(OH)D correlated negatively with Phuket HAI titers on day 28, r = −0.5, p = 0.02). Overall, our study demonstrates that vitamin A&D supplementation can improve immune responses to vaccines when children are vitamin A and D-insufficient at baseline. Results provide guidance for the appropriate use of vitamins A and D in future clinical vaccine studies.

Safety and immunogenicity of unadjuvanted subvirion monovalent inactivated influenza H3N2 variant (H3N2v) vaccine in children and adolescents

ObjectiveIn response to the emergence of influenza viruses with pandemic potential, we evaluated a swine-origin influenza A/H3N2 variant (H3N2v) vaccine in children. Study designThis multicenter phase II open-label study assessed the safety and immunogenicity of two doses, 21 days apart, of investigational unadjuvanted subvirion monovalent inactivated H3N2v vaccine administered via intramuscular injection. Children 6–35 months of age received 7.5mcg or 15mcg of hemagglutinin (HA)/dose; children 3–17 years of age received 15mcg HA/dose. Safety and reactogenicity were assessed by measuring the occurrence of solicited injection site and systemic reactions in the 7 days after each vaccination; adverse events were assessed for 42 days and serious adverse events for 7 months after the first vaccination. Immunogenicity was evaluated by measuring hemagglutination inhibition (HAI) and neutralizing (Neut) antibodies to H3N2v prior to and 21 days after each vaccination. Cross-reactivity against seasonal H3N2 strains was evaluated. ResultsThe H3N2v vaccine was well tolerated. Transient mild to moderate injection site tenderness, pain and erythema was observed, with the most commonly reported systemic reactogenicity being irritability in children 6–35 months, and headache and fatigue in children 9–17 years old. Children 6–35 months old, whether they received 7.5mcg or 15mcg/dose, had low HAI and Neut antibody responses after two doses compared to older children. Children under 9 years of age required two doses of vaccine to demonstrate a response, while 9–17 year olds responded well after one dose. Previous influenza vaccination and older age were associated with higher immune responses to H3N2v vaccine. Children 9–17 years of age also developed cross-reactive antibodies against recent seasonal H3N2 influenza viruses. ConclusionThe H3N2v vaccine was safe and immunogenic in children and adolescents. Age-related increases in immunogenicity against H3N2v and seasonal H3N2 viruses were observed, suggesting prior priming via infection and/or immunization.Clinical trial registry: The trial is registered with clinicaltrial.gov: NCT02100436.

HAI and NAI titer correlates of inactivated and live attenuated influenza vaccine efficacy

BackgroundHigh hemagglutination inhibition (HAI) and neuraminidase inhibition (NAI) titers are generally associated with reduced influenza risk. While repeated influenza vaccination reduces seroresponse, vaccine effectiveness is not always reduced.MethodsDuring the 2007-2008 influenza season, a randomized, placebo-controlled trial (FLUVACS) evaluated the efficacies of live-attenuated (LAIV) and inactivated influenza vaccines (IIV) among healthy adults aged 18-49 in Michigan; IIV vaccine efficacy (VE) and LAIV VE against influenza disease were estimated at 68% and 36%. Using the principal stratification/VE moderation framework, we analyzed data from this trial to assess how each VE varied by HAI or NAI responses to vaccination observed for vaccinated individuals and predicted counterfactually for placebo recipients. We also assessed how each VE varied with pre-vaccination/baseline variables including HAI titer, NAI titer, and vaccination history.ResultsIIV VE appeared to increase with Day 30 post-vaccination HAI titer, albeit not significantly (p=0.20 and estimated VE 14.4%, 70.5%, and 85.5% at titer below the assay lower quantification limit, 512, and 4096 (maximum)). Moreover, IIV VE increased significantly with Day 30 post-vaccination NAI titer (p=0.040), with estimated VE zero at titer 10 and 92.2% at highest titer 640. There was no evidence that fold-change in post-vaccination HAI or NAI titer associated with IIV VE (p=0.76, 0.38). For LAIV, there was no evidence that VE associated with post-vaccination or fold-rise HAI or NAI titers (p-values >0.40). For IIV, VE increased with increasing baseline NAI titer in those previously vaccinated, but VE decreased with increasing baseline NAI titer in those previously unvaccinated. In contrast, for LAIV, VE did not depend on previous vaccination or baseline HAI or NAI titer.Conclusions: Future efficacy trials should measure baseline and post-vaccination antibody titers in both vaccine and control/placebo recipients, enabling analyses to better elucidate correlates of vaccine- and natural-protection.Trial registration: ClinicalTrials.gov NCT00538512. October 1, 2007.

A computationally designed H5 antigen shows immunological breadth of coverage and protects against drifting avian strains

Since the first identification of the H5N1 Goose/Guangdong lineage in 1996, this highly pathogenic avian influenza virus has spread worldwide, becoming endemic in domestic poultry. Sporadic transmission to humans has raised concerns of a potential pandemic and underscores the need for a broad cross-protective influenza vaccine. Here, we tested our previously described methodology, termed Computationally Optimized Broadly Reactive Antigen (COBRA), to generate a novel hemagglutinin (HA) gene, termed COBRA-2, that was based on H5 HA sequences from 2005 to 2006. The COBRA-2 HA virus-like particle (VLP) vaccines were used to vaccinate chickens and the immune responses were compared to responses elicited by VLP’s expressing HA from A/whooper swan/Mongolia/244/2005 (WS/05), a representative 2005 vaccine virus from clade 2.2. To support this evaluation a hemagglutination inhibition (HAI) breadth panel was developed consisting of phylogenetically and antigenically diverse H5 strains in circulation from 2005 to 2006, as well as recent drift variants (2008 – 2014). We found that the COBRA-2 VLP vaccines elicited robust HAI titers against this entire breadth panel, whereas the VLP vaccine based upon the recommended WS/05 HA only elicited HAI responses against a subset of strains. Furthermore, while all vaccines protected chickens against challenge with the WS/05 virus, only the human COBRA-2 VLP vaccinated birds were protected (80%) against a recent drifted clade 2.3.2.1B, A/duck/Vietnam/NCVD-672/2011 (VN/11) virus. This is the first report to demonstrate seroprotective antibody responses against genetically diverse clades and sub-clades of H5 viruses and protective efficacy against a recent drifted variant using a globular head based design strategy.

Safety and immunogenicity of seasonal trivalent inactivated influenza vaccines in pregnant women

BackgroundIn the United States, seasonal inactivated influenza vaccine (IIV) is recommended for pregnant women; however, in early 2009, immunization rates were low, partly due to limited prospective data and concerns about vaccine safety. ObjectiveWe conducted a randomized study of two licensed seasonal trivalent IIVs (IIV3) to assess their safety and immunogenicity in pregnant women. Study DesignIn this prospective, randomized clinical study, 100 pregnant women, 18–39 years of age and ≥14 weeks gestation received a single intramuscular dose of 2008–2009 Fluzone® or Fluarix®. Injection site and systemic reactions were recorded for 7 days after vaccination and serious adverse events (SAEs) and pregnancy outcomes were documented. Serum samples collected before and 28 days after vaccination were tested for hemagglutination inhibition (HAI) antibody levels. ResultsThe majority of the injection site and systemic reactions were mild and self-limited after both vaccines. No fever ≥100 °F was reported. There were no vaccine-associated SAEs. Immune responses to influenza vaccine antigens were similar for the two study vaccines, with robust HAI responses against influenza A strains, and relatively lower responses for influenza B strains. ConclusionSeasonal inactivated influenza vaccines were well tolerated and immunogenic in pregnant women.ClinicalTrials.gov identifier NCT00905125.Synopsis: In this prospective clinical trial, we demonstrated that immunization with seasonal trivalent, inactivated influenza vaccine in the second and third trimester of pregnancy is immunogenic and safe.

In vivo cell-mediated immune, hemagglutination inhibition response, hematological and biochemical values in native vs. exotic chicken breeds.

Birds (364) of both sexes, 11-wk-old, belonging to 2 native (Brown Nicobari and Ghagus) breeds and 1 exotic breed (Dahlem Red) were evaluated for cell-mediated immune response (CMI) by phytohemagglutinin-P (PHA-P), hemagglutination inhibition (HI) assay against Newcastle disease virus (NDV) antigen (LaSota stock virus), flow cytometric analysis of CD8+ cytotoxic T lymphocytes (CTLs), and hematology and biochemical assays. The cutaneous basophil hypersensitivity response PHA-P% increase in wattle thickness (mm) was highest in Ghagus (431.14 ± 22.56) which differed significantly with that of Brown Nicobari (269.1 ± 22.66) and Dahlem Red (218.42 ± 22.30). Sex-wise observation showed that females are having significantly higher response than males. Hemagglutination inhibition test was performed to determine the serum antibodies against Newcastle disease (ND) virus. Brown Nicobari showed highest HI antibody titer than Ghagus and Dahlem Red to similar vaccination program after booster NDV dose. Flow cytometry assay revealed significantly higher CTLs proliferation in Brown Nicobari than Ghagus and Dahlem Red. Moreover, CTLs were found to be higher in control group than the treatment group. Other hematological parameters (103/μL) significant difference was found in white blood cell count between Dahlem Red (38.41 ± 1.03) with that of Brown Nicobari (35.28 ± 1.04) and Ghagus (34.57 ± 1.04) in treatment groups. Same trend was observed in the Lymphocyte treatment group. However, in Granulocyte treatment group, Brown Nicobari (11.04 ± 0.35) was found to be significantly different from Dahlem Red (8.68 ± 0.34) and Ghagus (9.27 ± 0.35). Correlations between body weight at 11 wk of age and CMI, HI, cytotoxic T cell were -0.093, 0.047, and -0.036, respectively. Egg weight was found to be positively correlated with that of chick weight. Serum biochemical values showed that Dahlem Red was having significantly higher creatinine levels compared to Ghagus. Triglycerides level was also significantly higher in Ghagus compared to Dahlem Red. No significant breed effect was observed for alkaline phosphate, aspartate transaminase, and alanine transaminase. Cholesterol and total serum protein levels were significantly higher in Dahlem Red compared to Brown Nicobari.

Benralizumab does not impair antibody response to seasonal influenza vaccination in adolescent and young adult patients with moderate to severe asthma: results from the Phase IIIb ALIZE trial.

Background and objectivesBenralizumab is a humanized, afucosylated monoclonal antibody against the IL-5Rα. Initial monthly followed by every-other-month injections result in rapid and nearly complete eosinophil depletion. We evaluated whether three doses of benralizumab modifies antibody response to seasonal influenza vaccination for adolescent/young adult patients with moderate to severe asthma.MethodsALIZE (NCT02814643) was a Phase IIIb randomized controlled trial of patients aged 12–21 years receiving medium- to high-dosage inhaled corticosteroids/long-acting β2-agonists. Patients received benralizumab 30 mg or placebo at Weeks 0, 4, and 8, plus tetravalent influenza vaccination at Week 8. At Week 12, strain-specific antibody responses following vaccination were assessed for four influenza antigens by hemagglutination inhibition (HAI) and microneutralization (MN) assays.ResultsA total of 103 patients were randomized and received benralizumab (n=51) or placebo (n=52). There were no consistent differences in HAI or MN antibody responses at Week 12 between patients receiving benralizumab or placebo. HAI geometric mean fold rises (GMFRs) for all influenza strains tested were 3.3–4.2 for benralizumab vs 3.4–3.9 for placebo; MN GMFRs were 2.8–5.1 for benralizumab vs 3.2–4.4 for placebo. A ≥4-fold rise in HAI from Weeks 8 to 12 occurred in 44.0%–56.0% and 30.6%–49.0% of patients receiving benralizumab and placebo, respectively. At Week 12, 78.0%–100% vs 79.6%–100% of patients receiving benralizumab and placebo, respectively, achieved a ≥40 HAI antibody titer. There were no significant safety findings.ConclusionBenralizumab did not impair the antibody response to seasonal virus vaccination in adolescents and young adult patients with moderate to severe asthma.

Safety and immunogenicity of a seasonal trivalent inactivated split influenza vaccine: a phase I randomized clinical trial in healthy Serbian adults

ABSTRACTThis study was a phase I double-blind, randomized, placebo-controlled trial to evaluate the safety and immunogenicity of a Serbian-produced seasonal trivalent split, inactivated influenza vaccine in healthy adults. The vaccine was manufactured in eggs by the Torlak Institute of Virology, Vaccines and Sera, Belgrade, Serbia and contained A/H1N1, A/H3N2 and B viruses. The clinical trial took place at the Clinical Center of Serbia in Belgrade. Sixty healthy volunteers, aged 18–45 years, were enrolled in the trial. On the day of immunization, volunteers were randomly assigned to receive either a single dose of the trivalent seasonal influenza vaccine (15 μg of hemagglutinin per strain) or placebo (phosphate-buffered saline). Subjects were monitored for adverse events through a clinical history and physical examination, and blood was taken for testing at screening and on day 8 to assess vaccine safety. Serum samples obtained before and 21 days after immunization were tested for influenza antibody titers using hemagglutination-inhibition (HAI) and microneutralization (MN) tests. No serious adverse events were reported. Pain and tenderness at the injection site were the most commonly reported symptoms in both vaccine and placebo groups. Overall, serum HAI responses of fourfold or greater magnitude were observed to H1, H3, and B antigen in 80%, 75%, and 70% of subjects, respectively. Seroprotection rates as measured by HAI were also high (100%, 100% and 86.67%, respectively, for H1, H3 and B). Thus, Torlak's seasonal trivalent influenza vaccine was not associated with adverse events, was well-tolerated and immunogenic. It should be further evaluated in clinical trials to provide sufficient safety and immunogenicity data for licensing in Serbia.

The effect of frailty on HAI response to influenza vaccine among community-dwelling adults ≥ 50 years of age

ABSTRACTThe immune response to vaccine antigens is less robust in older adults because of changes in the aging immune system. Frailty, the multi-dimensional syndrome marked by losses in function and physiological reserve, is increasingly prevalent with advancing age. Frailty accelerates this immunosenescence but the consequence of frailty on immune response specific to influenza vaccine among older adults, is mixed. An observational, prospective study of 114 adults was conducted in the fall of 2013 to assess the association of physical frailty with immune response to standard dose influenza vaccine in community-dwelling adults ≥ 50 years of age. Participants were stratified by age (<65 years and ≥65 years), and vaccine strain (Influenza A/H1N1, A/H3N2 and B) was analyzed separately adjusting for body mass index (BMI) and baseline log2 hemagglutination inhibition (HAI) titers. Overall, immune responses were lower among those ≥65 years of age than those <65 years. Among those ≥65 years there were no significant differences between frail and non-frail individuals in seroprotection or seroconversion for any influenza strain. Frail individuals <65 years of age compared with non-frail individuals were more likely to be seroprotected and to seroconvert post vaccination. Linear regression models show the same pattern of significant differences between frail and non-frail for those <65 years but no significant differences between frailty groups for those ≥65 years. Additional research may elucidate the reasons for the differences observed between younger frail and non-frail adults.