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.     

A prime-boost concept using a T-cell epitope-driven DNA vaccine followed by a whole virus vaccine effectively protected pigs in the pandemic H1N1 pig challenge model

Influenza A virus (IAV) vaccines in pigs generally provide homosubtypic protection but fail to prevent heterologous infections. In this pilot study, the efficacy of an intradermal pDNA vaccine composed of conserved SLA class I and class II T cell epitopes (EPITOPE) against a homosubtypic challenge was compared to an intramuscular commercial inactivated whole virus vaccine (INACT) and a heterologous prime boost approach using both vaccines. Thirty-nine IAV-free, 3-week-old pigs were randomly assigned to one of five groups including NEG-CONTROL (unvaccinated, sham-challenged), INACT-INACT-IAV (vaccinated with FluSure XP® at 4 and 7 weeks, pH1N1 challenged), EPITOPE-INACT-IAV (vaccinated with PigMatrix EDV at 4 and FluSure XP® at 7 weeks, pH1N1 challenged), EPITOPE-EPITOPE-IAV (vaccinated with PigMatrix EDV at 4 and 7 weeks, pH1N1 challenged), and a POS-CONTROL group (unvaccinated, pH1N1 challenged). The challenge was done at 9 weeks of age and pigs were necropsied at day post challenge (dpc) 5. At the time of challenge, all INACT-INACT-IAV pigs, and by dpc 5 all EPITOPE-INACT-IAV pigs were IAV seropositive. IFNγ secreting cells, recognizing vaccine epitope-specific peptides and pH1N1 challenge virus were highest in the EPITOPE-INACT-IAV pigs at challenge. Macroscopic lung lesion scores were reduced in all EPITOPE-INACT-IAV pigs while INACT-INACT-IAV pigs exhibited a bimodal distribution of low and high scores akin to naïve challenged animals. No IAV antigen in lung tissues was detected at necropsy in the EPITOPE-INACT-IAV group, which was similar to naïve unchallenged pigs and different from all other challenged groups. Results suggest that the heterologous prime boost approach using an epitope-driven DNA vaccine followed by an inactivated vaccine was effective against a homosubtypic challenge, and further exploration of this vaccine approach as a practical control measure against heterosubtypic IAV infections is warranted.     

Inactivated influenza vaccine formulated with single-stranded RNA-based adjuvant confers mucosal immunity and cross-protection against influenza virus infection

Influenza vaccination is considered the most valuable means to prevent and control seasonal influenza infections, which causes various clinical symptoms, ranging from mild cough and fever to even death. Among various influenza vaccine types, the inactivated subunit type is known to provide improved safety with reduced reactogenicity. However, there are some drawbacks associated with inactivated subunit type vaccines, with the main ones being its low immunogenicity and the induction of Th2-biased immune responses. In this study, we investigated the role of a single-stranded RNA (ssRNA) derived from the intergenic region in the internal ribosome entry site of the Cricket paralysis virus as an adjuvant rather than the universal vaccine for a seasonal inactivated subunit influenza vaccine. The ssRNA adjuvant stimulated not only well-balanced cellular (indicated by IgG2a, IFN-γ, IL-2, and TNF-α) and humoral (indicated by IgG1 and IL-4) immune responses but also a mucosal immune response (indicated by IgA), a key protector against respiratory virus infections. It also increases the HI titer, the surrogate marker of influenza vaccine efficacy. Furthermore, ssRNA adjuvant confers cross-protective immune responses against heterologous influenza virus infection while promoting enhanced viral clearance. Moreover, ssRNA adjuvant increases the number of memory CD4⁺ and CD8⁺ T cells, which can be expected to induce long-term immune responses. Therefore, this ssRNA-adjuvanted seasonal inactivated subunit influenza vaccine might be the best influenza vaccine generating robust humoral and cellular immune responses and conferring cross-protective and long-term immunity.     

Immunogenicity and safety of a quadrivalent inactivated influenza vaccine in children 6–59 months of age: A phase 3, randomized,noninferiority study

Background

In the Southern Hemisphere 2010 influenza season, Seqirus’ split-virion, trivalent inactivated influenza vaccine was associated with increased reports of fevers and febrile reactions in young children. A staged clinical development program of a quadrivalent vaccine (Seqirus IIV4 [S-IIV4]; Afluria® Quadrivalent/Afluria Quad?/Afluria Tetra?), wherein each vaccine strain is split using a higher detergent concentration to reduce lipid content (considered the cause of the increased fevers and febrile reactions), is now complete.

Protection of White Leghorn chickens by recombinant fowlpox vector vaccine with an updated H5 insert against Mexican H5N2 avian influenza viruses

Despite decades of vaccination, surveillance, and biosecurity measures, H5N2 low pathogenicity avian influenza (LPAI) virus infections continue in Mexico and neighboring countries. One explanation for tenacity of H5N2 LPAI in Mexico is the antigenic divergence of circulating field viruses compared to licensed vaccines due to antigenic drift. Our phylogenetic analysis indicates that the H5N2 LPAI viruses circulating in Mexico and neighboring countries since 1994 have undergone antigenic drift away from vaccine seed strains. Here we evaluated the efficacy of a new recombinant fowlpox virus vector containing an updated H5 insert (rFPV-H5/2016), more relevant to the current strains circulating in Mexico. We tested the vaccine efficacy against a closely related subcluster 4 Mexican H5N2 LPAI (2010 H5/LP) virus and the historic H5N2 HPAI (1995 H5/HP) virus in White Leghorn chickens. The rFPV-H5/2016 vaccine provided hemagglutinin inhibition (HI) titers pre-challenge against viral antigens from both challenge viruses in almost 100% of the immunized birds, with no differences in number of birds seroconverting or HI titers among all tested doses (1.5, 2.0, and 3.1 log₁₀ mean tissue culture infectious doses/bird). The vaccine conferred 100% clinical protection and a significant decrease in oral and cloacal virus shedding from 1995 H5/HP virus challenged birds when compared to the sham controls at all tested doses. Virus shedding titers from vaccinated 2010 H5/LP virus challenged birds significantly decreased compared to sham birds especially at earlier time points. Our results confirm the efficacy of the new rFPV-H5/2016 against antigenic drift of LPAI virus in Mexico and suggest that this vaccine would be a good candidate, likely as a primer in a prime-boost vaccination program.     

Comparison of immunogenicity between candidate influenza A(H3N2) virus vaccine strains in Japan: A randomized controlled trial using a monovalent vaccine of A/Saitama/103/2014 (CEXP-002) and A/Hong Kong/4801/2014 (X-263)

BackgroundFor the 2017–18 influenza season, A/Saitama/103/2014 (CEXP-002) (Saitama strain) was antigenically more similar to prior circulating strains than A/Hong Kong/4801/2014 (X-263) (Hong Kong strain) in a ferret model and was selected as the A(H3N2) vaccine virus strain in Japan. However, the Saitama strain grew poorly, and the Japanese government switched to the Hong Kong strain, raising public concerns of poor effectiveness. To enhance understanding of the correlation between antigenicity in experimental models and immunogenicity, as a surrogate measure of vaccine effectiveness, in the human population, we compared the immunogenicity of specially-prepared single dose monovalent influenza A(H3N2) vaccines containing the Saitama or the Hong Kong strain.MethodsA randomized controlled trial of 100 healthy adults aged 20–64 years (n = 50/group) was conducted. Virus neutralization assay was performed on sera from days 0 (pre-vaccination) and 21 (post-vaccination). Geometric mean titer (GMT), mean fold rise (MFR), seroconversion proportion (SCP), and seroprotection proportion (SPP) were calculated for vaccine strains and a representative circulating A(H3N2) virus strain (A/Osaka/188/2017).ResultsFor the Hong Kong strain, post-vaccination GMT was significantly higher in the Hong Kong vaccine recipients (1:546 vs 1:260, p < 0.01), but MFR, SCP, and SPP were similar for both vaccine groups. For the Saitama strain, post-vaccination GMT (1:116 vs 1:61, p = 0.01) and SPP (86% vs 68%, p = 0.03) were significantly higher in the Hong Kong vaccine recipients, but MFR and SCP were similar for both vaccine groups. Against A/Osaka/188/2017, post-vaccination GMT and MFR were similar in both vaccine groups, but SCP (32% vs 4%, p < 0.01) and SPP (28% vs. 6%, p < 0.01) were significantly higher in the Hong Kong vaccine recipients.ConclusionThe Hong Kong vaccine induced better or equivalent immunogenicity in comparison to the Saitama vaccine. Our trial showed that antigenic similarity in experimental models does not necessarily correlate with immunogenicity in the human population.Clinical trial registration: UMIN000029293.     

Immunogenicity and safety of MF59-adjuvanted quadrivalent influenza vaccine versus standard and alternate B strain MF59-adjuvanted trivalent influenza vaccines in older adults

ObjectiveEvaluate whether adjuvanted quadrivalent influenza vaccine (aQIV) elicits a noninferior immune response compared with a licensed adjuvanted trivalent influenza vaccine (aTIV-1; Fluad™) and aTIV-2 containing an alternate B strain, examine whether aQIV had immunological superiority for the B strain absent from aTIV comparators, and evaluate reactogenicity and safety among adults ≥65 years.MethodsIn a multicenter, double-blind, randomized controlled trial, adults ≥65 years were randomized 2:1:1 to vaccination with aQIV (n = 889), aTIV-1 (n = 445), or aTIV-2 (n = 444) during the 2017-2018 influenza season. Immunogenicity was assessed by hemagglutination inhibition (HI) assay conducted on serum samples collected before vaccination and 21 days after vaccination for homologous influenza strains.ResultsaQIV met non-inferiority criteria for geometric mean titer ratios (GMT ratios) and seroconversion rate (SCR) differences against aTIV. The upper bounds of the 2-sided 95% confidence interval (CI) for GMT ratios were <1.5 for all 4 strains (A/H1N1 = 1.27, A/H3N2 = 1.09, B-Yamagata = 1.08, B-Victoria = 1.08). The upper bounds of the 95% CI of the SCR differences were <10% for all 4 strains (A/H1N1 = 7.76%, A/H3N2 = 4.96%, B-Yamagata = 3.27%, B-Victoria = 2.55%). aQIV also met superiority criteria (upper bound of 95% CI for GMT ratios <1 and SCR differences <0) for B strain absent from aTIV comparators (B-Yamagata GMT ratio = 0.70, SCR difference = −8.81%; B-Victoria GMT ratio = 0.78, SCR difference = −8.11%). aQIV and aTIV vaccines were immunogenic and well-tolerated. The immunological benefit of aQIV was also demonstrated in age subgroups 65–74 years, 75–84 years, and ≥85 years and in those with high comorbidity risk scores. Reactogenicity profiles were generally comparable.ConclusionaQIV induces a similar immune response as the licensed aTIV vaccine against homologous influenza strains and has a comparable reactogenicity and safety profile. Superior immunogenicity against the additional B strain was observed, indicating that aQIV could provide a broader protection than aTIV against influenza in older adults (NCT03314662).     

分枝杆菌肝素结合血凝素研究进展

结核病是由分枝杆菌感染引起的世界范围内流行的人畜共患病。肝素结合血凝素(heparin-binding adhesin,HBHA)是分枝杆菌表达的一种蛋白质,致病性分枝杆菌的HBHA蛋白具有黏附上皮细胞、扩散感染范围等功能。其发挥黏附功能的C端结构域能够刺激机体产生有效的Th1细胞免疫反应;HBHA特异的黏膜免疫反应能够提供一定的保护效果。这提示HBHA具有制作为疫苗的潜力。而且,HBHA蛋白在活动性结核病患者和潜伏感染者中引发的免疫反应存在差异,这使其可以成为新的诊断抗原。此外,在细胞水平上,HBHA可以利用补体系统进入巨噬细胞,促使巨噬细胞向M1极化,同时能够逃避自噬并诱发线粒体损伤和内质网应激介导功能,这为结核病的致病机制提供了更多的解释。HBHA与宿主之间相互作用认识的积累,可以为HBHA的应用性研究提供依据。     

Memory B Cells that Cross-React with Group 1 and Group 2 Influenza A Viruses Are Abundant in Adult Human Repertoires

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Increasing FIM2/3 antigen-content improves efficacy of Bordetella pertussis vaccines in mice in vivo without altering vaccine-induced human reactogenicity biomarkers in vitro

Current acellular-pertussis (aP) vaccines appear inadequate for long-term pertussis control because of short-lived efficacy and the increasing prevalence of pertactin-negative isolates which may negatively impact vaccine efficacy. In this study, we added fimbriae (FIM)2 and FIM3 protein to licensed 2-, 3- or 5-component aP vaccines (Pentavac®, Boostrix®, Adacel®, respectively) to assess whether an aP vaccine with enhanced FIM content demonstrates enhanced efficacy. Vaccine-induced protection was assessed in an intranasal mouse challenge model. In addition, potential reactogenicity was measured by biomarkers in a human whole blood assay (WBA) in vitro and benchmarked the responses against licensed whole cell pertussis (wP) and aP vaccines including Easyfive®, Pentavac® and Pentacel®. The results show that commercial vaccines demonstrated reduced efficacy against pertactin-negative versus pertactin-positive strains. However, addition of higher amounts of FIM2/3 to aP vaccines reduced lung colonization and increased vaccine efficacy against a pertactin-negative strain in a dose-dependent manner. Improvements in efficacy were similar for FIM2 and FIM3-expressing strains. Increasing the amount of FIM2/3 proteins in aP formulations did not alter vaccine-induced biomarkers of potential reactogenicity including prostaglandin E₂, cytokines and chemokines in human newborn cord and adult peripheral blood tested in vitro. These results suggest that increasing the quantity of FIM proteins in current pertussis vaccine formulations may further enhance vaccine efficacy against B. pertussis infection without increasing the reactogenicity of the vaccine.