Neutralization Fingerprinting Technology for Characterizing Polyclonal Antibody Responses to Dengue Vaccines

Dengue is a major public health threat. There are four serotypes of dengue virus (DENV), therefore efforts are focused on development of safe and effective tetravalent DENV vaccines. While neutralizing antibodies contribute to protective immunity, there are still important gaps in understanding of immune responses elicited by dengue infection and vaccination, including defining immune correlates of protection. To that end, here we present a computational modeling framework for evaluating the specificities of neutralizing antibodies elicited to tetravalent DENV vaccines, based on the concept of antibody-virus neutralization fingerprints. We developed and applied this framework to samples from clinical studies of TAK-003, a tetravalent vaccine candidate currently in phase 3 trials, to characterize the effect of prior dengue infection (baseline) on the specificities of vaccine-elicited antibody responses. Our results suggested a similarity of neutralizing antibody specificities in baseline-seronegative individuals. In contrast, amplification of pre-existing neutralizing antibody specificities was predicted for baseline-seropositive individuals, thus quantifying the role of immunologic imprinting in driving antibody responses to DENV vaccines. The analysis framework proposed here can apply to studies of sequential dengue infections and other tetravalent DENV vaccines and can contribute to understanding dengue immune correlates of protection to help guide further vaccine development and optimization.

Multi-Antigen Outer Membrane Vesicle Engineering to Develop Polyvalent Vaccines: The Staphylococcus aureus Case

Modification of surface antigens and differential expression of virulence factors are frequent strategies pathogens adopt to escape the host immune system. These escape mechanisms make pathogens a “moving target” for our immune system and represent a challenge for the development of vaccines, which require more than one antigen to be efficacious. Therefore, the availability of strategies, which simplify vaccine design, is highly desirable. Bacterial Outer Membrane Vesicles (OMVs) are a promising vaccine platform for their built-in adjuvanticity, ease of purification and flexibility to be engineered with foreign proteins. However, data on if and how OMVs can be engineered with multiple antigens is limited. In this work, we report a multi-antigen expression strategy based on the co-expression of two chimeras, each constituted by head-to-tail fusions of immunogenic proteins, in the same OMV-producing strain. We tested the strategy to develop a vaccine against Staphylococcus aureus, a Gram-positive human pathogen responsible for a large number of community and hospital-acquired diseases. Here we describe an OMV-based vaccine in which four S. aureus virulent factors, ClfAY338A, LukE, SpAKKAA and HlaH35L have been co-expressed in the same OMVs (CLSH-OMVsΔ60). The vaccine elicited antigen-specific antibodies with functional activity, as judged by their capacity to promote opsonophagocytosis and to inhibit Hla-mediated hemolysis, LukED-mediated leukocyte killing, and ClfA-mediated S. aureus binding to fibrinogen. Mice vaccinated with CLSH-OMVsΔ60 were robustly protected from S. aureus challenge in the skin, sepsis and kidney abscess models. This study not only describes a generalized approach to develop easy-to-produce and inexpensive multi-component vaccines, but also proposes a new tetravalent vaccine candidate ready to move to development.

636. A Phase I Study to Evaluate the Safety, Tolerability, and Immunogenicity of a Live, Attenuated, Quadrivalent Dengue Vaccine (V181)

Background Dengue (DENV) is a mosquito-borne virus with four serotypes causing substantial morbidity in tropical and subtropical areas worldwide. A dengue vaccine that can be given to both seronegative and seropositive populations remains an important unmet medical need. V181 is an investigational live, attenuated, quadrivalent dengue vaccine. Methods In this phase 1 double-blind, placebo-controlled study, the safety, tolerability, and immunogenicity of V181 in healthy adults were evaluated in two formulations: TV003 and TV005. TV005 has a 10-fold higher DENV2 component as compared to TV003. Two-hundred participants [~ 50% baseline flavivirus-experienced (BFE) and 50% baseline flavivirus-naive (BFN)] were randomized 2:2:1 to receive TV003, TV005, or placebo on Days 1 and 180. Immunogenicity against each of the four DENV serotypes was measured using a Virus Reduction Neutralization Test (VRNT60) after each vaccination and out to 1 year after the second dose. Results There were no discontinuations due to adverse events (AEs) or vaccine-related serious AEs. The most common AEs Days 1-28 after any TV003 or TV005 vaccination were rash, headache, fatigue, and myalgia. DENV VRNT60 seropositivity to 3 or 4 serotypes (i.e. tri-or tetravalent) was demonstrated in 92.6% of BFN TV003 participants, 74.2% of BFN TV005 participants, and 100% of the BFE participants at 6 months postdose 1 (PD1). Vaccine viremia, a measure of vaccine infectivity, was transiently detected from all four DENV types after the first dose of TV003 and TV005. Tri- or tetravalent vaccine-viremia was detected in 63.9 % and 25.6 % of BFN TV003 and TV005 participants, respectively, PD1. Compared to baseline, robust increases in VRNT60 GMTs were observed after the first dose of TV003 and TV005 in both flavivirus subgroups for all DENV serotypes and minimal increases were observed PD2. GMTs in the TV003 and TV005 BFE and BFN subgroups remained above the respective baselines and placebo at 1-year PD2. Conclusion Both formulations of V181 were generally well tolerated in healthy adults. Overall, viremia and immunogenicity were higher after TV003 as compared to TV005. These data support the continued development of the V181 TV003 formulation as a single-dose vaccine for the prevention of DENV disease. Disclosures Kevin Russell, MD, MTM&H, Merck & Co., Inc. (Employee, Shareholder) Richard E. Rupp, MD, Merck & Co., Inc. (Research Grant or Support) Clemente Diaz-Perez, MD, Merck & Co., Inc. (Research Grant or Support) Charles P. Andrews, MD, Merck & Co., Inc. (Research Grant or Support) Andrew W. Lee, MD, Merck & Co., Inc. (Employee, Shareholder) Tyler S. Finn, BA, Merck & Co., Inc. (Employee, Shareholder) Kara Cox, MS, Merck & Co., Inc. (Employee, Shareholder) Amy Falk Russell, MS, Merck & Co., Inc. (Employee, Shareholder) Margaret M. Schaller, BS, Merck & Co., Inc. (Employee, Shareholder) Jason C. Martin, PhD, Merck & Co., Inc. (Employee, Shareholder) Donna M. Hyatt, BA, Merck & Co., Inc. (Employee, Shareholder) Sabrina Gozlan-Kelner, MS, Merck & Co., Inc. (Employee, Shareholder) Androniki Bili, MD, MPH, Merck & Co., Inc. (Employee, Shareholder) Beth-Ann Coller, PhD, Merck & Co., Inc. (Employee, Shareholder)

Pre-vaccination Frequency of Circulatory Tfh is associated with Robust Immune Response to TV003 Dengue Vaccine

It has been estimated that more than 390 million people are infected with Dengue virus every year; around 96 millions of these infections result in clinical pathologies. To date, there is only one licensed viral vector-based Dengue virus vaccine CYD-TDV approved for use in dengue endemic areas. While initially approved for administration independent of serostatus, the current guidance only recommends the use of this vaccine for seropositive individuals. Therefore, there is a critical need for investigating the influence of Dengue virus serostatus and immunological mechanisms that influence vaccine outcome. Here, we provide comprehensive evaluation of sero-status and host immune factors that correlate with robust immune responses to a Dengue virus vector based tetravalent vaccine (TV003) in a Phase II clinical cohort of human participants. We observed that sero-positive individuals demonstrate a much stronger immune response to the TV003 vaccine. Our multi-layered immune profiling revealed that sero-positive subjects have increased baseline/pre-vaccination frequencies of circulating T follicular helper (cTfh) cells and the Tfh related chemokine CXCL13/BLC. Importantly, this baseline/pre-vaccination cTfh profile correlated with the vaccinees’ ability to launch neutralizing antibody response against all four sero-types of Dengue virus, an important endpoint for Dengue vaccine clinical trials. Overall, we provide novel insights into the favorable cTfh related immune status that persists in Dengue virus sero-positive individuals that correlate with their ability to mount robust vaccine specific immune responses. Such detailed interrogation of cTfh cell biology in the context of clinical vaccinology will help uncover mechanisms and targets for favorable immuno-modulatory agents.Author summaryDengue virus (DENV) is a worldwide threat that causes significant health and economic burden. Currently, there are several challenges in the development of a DENV vaccine including the existence of four different serotypes all; capable of causing disease and antibody dependent enhancement (ADE). For complete protection, a vaccine must be able to generate neutralizing antibodies against all 4 serotypes to avoid ADE. Currently, there is one licensed DENV vaccine, CYD-TDV (DENGVAXIATM). However, this vaccine is only efficacious in protecting against severe disease in DENV seropositive individuals therefore serostatus effect must be further studied for optimal vaccine design. A subset of CD4+ T cells called T-follicular helper (Tfh) cells have been well known to play a major role in aiding high affinity antibody production. Therefore, we chose to look at subsets of Tfh and the cytokines they produce in human blood that can serve as biomarkers for effective vaccine design. We found that DENV sero-positive participants had increased pre-vaccination frequencies of Tfh cells and higher levels of the Tfh related chemokine CXCL13/BLC that plays a role in directing antigen-specific responses. This pre-vaccination Tfh profile and CXCL13/BLC are then correlated positively with the vaccinees’ ability to produce neutralizing antibody against all four sero-types (breadth of the Response) of DENV, an important goal for all DENV vaccine trials.

Target product profile for a dengue pre-vaccination screening test

With increasing geographic spread, frequency, and magnitude of outbreaks, dengue continues to pose a major public health threat worldwide. Dengvaxia, a dengue live-attenuated tetravalent vaccine, was licensed in 2015, but post hoc analyses of long-term data showed serostatus-dependent vaccine performance with an excess risk of hospitalized and severe dengue in seronegative vaccine recipients. The World Health Organization (WHO) recommended that only persons with evidence of past dengue infection should receive the vaccine. A test for pre-vaccination screening for dengue serostatus is needed. To develop the target product profile (TPP) for a dengue pre-vaccination screening test, face-to-face consultative meetings were organized with follow-up regional consultations. A technical working group was formed to develop consensus on a reference test against which candidate pre-vaccination screening tests could be compared. The group also reviewed current diagnostic landscape and the need to accelerate the evaluation, regulatory approval, and policy development of tests that can identify seropositive individuals and maximize public health impact of vaccination while avoiding the risk of hospitalization in dengue-naive individuals. Pre-vaccination screening strategies will benefit from rapid diagnostic tests (RDTs) that are affordable, sensitive, and specific and can be used at the point of care (POC). The TPP described the minimum and ideal characteristics of a dengue pre-vaccination screening RDT with an emphasis on high specificity. The group also made suggestions for accelerating access to these RDTs through streamlining regulatory approval and policy development. Risk and benefit based on what can be achieved with RDTs meeting minimal and optimal characteristics in the TPP across a range of seroprevalences were defined. The final choice of RDTs in each country will depend on the performance of the RDT, dengue seroprevalence in the target population, tolerance of risk, and cost-effectiveness.

Vaccination services and incomplete vaccine coverage for children: a comparative spatial analysis of the BRISA cohorts, São Luís (Maranhão State) and Ribeirão Preto (São Paulo State), Brazil

We analyzed the spatial relation between incomplete vaccine coverage for children and the distance from vaccination services. This was a cross-sectional study of children from 13 to 35 months of age from the cities of São Luís (Maranhão State) and Ribeirão Preto (São Paulo State), Brazil, and from basic health units (UBS, in Portuguese). The sample consisted of 2,744 children from São Luís and 3,325 from Ribeirão Preto. Data about incomplete vaccine coverage for children were obtained from the BRISA birth cohorts. Data about the quality of UBS vaccination services were obtained from the first cycle of the Brazilian National Program for Improvement of Access and Quality of Basic Care (PMAQ-AB, in Portuguese). For the spatial analysis, we determined the distance between the residence of the children (with and without a complete vaccine calendar) and the vaccination services of the UBS (classified according to number of structural items). Incomplete vaccine coverage was more pronounced in São Luís, with greater percentages for human rotavirus and triple viral vaccines, with the latter being the least available. In Ribeirão Preto, incomplete BCG vaccine coverage was more pronounced, with the tetravalent vaccine being the least available. Children from the two cities showed similarities: most of them had adult mothers with 9 to 11 years of schooling and did not reside with siblings in the household. They also showed differences: in São Luís, most mothers belonged to the economic class C, while in Ribeirão Preto they belong to the A and B classes. In the two cities with different socioeconomic conditions, complete vaccine coverage seemed not to depend on the location or quality of the vaccination service. Although São Luís showed a better structure of the services, incomplete vaccine coverage was higher compared to Ribeirão Preto.

Meningitis in Brazil and its regions: a reflection on vaccination coverage in the last decade

Introduction: Meningitis is a potentially fatal disease. Vaccines play a fundamental role in its prevention, so it is important to reflect on the vaccination coverage (VC) performed in Brazil and in its regions. Objectives: To analyze the VC of meningitis in Brazil and regions in the last decade. Design and setting: Ecological study carried out in Brazil. Methods: Data were collected in the Information System of the National Immunization Program from the Computer Department of the Unified Health System between 2011 and 2020. The variables analyzed were: region, capitals and immunizers, which are Meningococcus C, Pneumococcal, Haemophilus influenzae b and Tetravalente. Evaluation by the Research Ethics Committee was waived because it is public data. Results: During this period, the national VC against meningitis was 86.8%, with 19.8% of reduction when comparing 2011 and 2020. The South had the highest VC (91.0%), followed by the MidWest (90.2%), Southeast (88.7%), Northeast (85.0%) and North (76.6%), while the Southeast suffered the greatest reduction (24.0%) and the North the smallest (9.6%). The capitals had a total VC of 83.7%. The vaccines meningococcus C and pneumococcal had higher levels of total VC (92.9% and 90.4%, respectively), while their booster doses had VC of 85.4% and 83.3%, respectively. The tetravalent vaccine had a rate of 77.0%. Conclusions: Except for the North, Brazilian regions have obtained adequate VCs in the last decade, but these rates have been decreasing. It is urgent to strengthen the national vaccination plan in the country, especially in the North.

Development of Human Vectored Brucellosis Vaccine Formulation: Assessment of Safety and Protectiveness of Influenza Viral Vectors Expressing Brucella Immunodominant Proteins in Mice and Guinea Pigs

In this paper, we first used recombinant influenza viral vector (rIVV) subtype H5N1 expressing from the open reading frame of NS1 80 and NS1 124 amino acids of Brucella outer membrane proteins (Omp) 16 and 19, ribosomal L7/L12, and Cu-Zn superoxide dismutase (SOD) proteins to develop a human brucellosis vaccine. We made 18 combinations of IVVs in mono-, bi-, and tetravalent vaccine formulations and tested them on mice to select the safest and most effective vaccine samples. Then, the most effective vaccine candidates were further tested on guinea pigs. Safety of the rIVV-based vaccine candidate was evaluated by a mouse weight-gain test. Mice and guinea pigs were challenged with the virulent strain B. melitensis 16M. The protective effect of the rIVV-based vaccine candidate was assessed by quantitation of Brucella colonization in tissues and organs of challenged animals. All vaccine formulations were safe in mice. Tested vaccine formulations, as well as the commercial B. melitensis Rev.1 vaccine, have been found to protect mice from B. melitensis 16M infection within the range of 1.6 to 2.97 log10 units ( P < 0.05 ). Tetravalent vaccine formulations from the position of NS1 80 amino acids ( 0.2 ± 0.4 ), as well as the commercial B. melitensis Rev.1 vaccine ( 1.2 ± 2.6 ), have been found to protect guinea pigs from B. melitensis 16M infection at a significant level ( P < 0.05 ). Thus, tetravalent vaccine formulation Flu-NS1-80-Omp16+Flu-NS1-80-L7/L12+Flu-NS1-80-Omp19+Flu-NS1-80-SOD was chosen as a potential vaccine candidate for further development of an effective human vaccine against brucellosis. These results show a promising future for the development of a safe human vaccine against brucellosis based on rIVVs.

Dengue Vector Control in Malaysia- Challenges and Recent Advances

Dengue is a serious mosquito borne disease common in tropical and sub-tropical countries including Malaysia. There is at present a lack of specific treatment and an effective tetravalent vaccine against dengue. The control of dengue depends solely on the suppression of the two most important vectors namely, Aedes aegypti and Ae albopictus. Despite intensive and extensive control efforts by health agencies, the disease continues to spread. This paper updates various innovations on control of dengue vectors. Gene-based sterile insect technique using the RIDL technology for both Aedes aegypti & Ae albopictus control has now been actively researched and field trials are pursued to evaluate the effectiveness of the technology. The release of Wolbachia-infected Ae aegypti is another dengue control innovation. The infected mosquito cannot support development of dengue virus and has shorter life span. Other innovations include: auto-dissemination of insect control agents using ovitrap, autocidal adult and larva trap, outdoor residual spraying, insecticidal paint and biocontrol agent. In other innovation, outbreak prediction capability is enhanced by developing model based on environmental data and analysis utilising neural network.

Description of Influenza B in seasonal epidemic in Cantabria during the beginning of the pandemia due to SARS-CoV-2

Introduction. Co-circulation of the two Influenza B lineages hinders forecast of strain to include in trivalent vaccine. Autonomous Communities such as Cantabria continue without supplying tetravalent vaccine. The aim of this study was to analyse epidemiological characteristics of influenza type B in Cantabria (2019-2020 season) as well as to establish the predominant lineage and its relation to the recommended vaccine. Methods. Retrospective study whereby flu diagnosis and lineage analysis were determined by RT-PCR. Results. All samples belonged to the Victoria lineage. Most prevalent viral co-infection was due to SARS-CoV-2. The population affected by influenza B was mainly paediatric and non-vaccinated patients more frequently required hospital admittance. Conclusions. Influenza type B has a higher incidence in the paediatric population and type A affects more the adult population. Only 28.8% of patients with Influenza B that presented with some underlying condition or risk factor were vaccinated. This shows the need to increase coverage with tetravalent vaccines in order to reduce the burden of disease associated with the Influenza B virus.