Community Research and Development Information Service - CORDIS

FP7

PLACMALVAC Report Summary

Project ID: 304815
Funded under: FP7-HEALTH
Country: Denmark

Periodic Report Summary 2 - PLACMALVAC (Clinical development of a VAR2CSA-based placental malaria vaccine)

Project Context and Objectives:
Project context
The most deadly form of malaria is caused by the parasite Plasmodium falciparum, which is transmitted to humans by infected mosquitoes. Infection leads to different disease syndromes, at least partially as a result of the expression of parasite-derived antigens on the surface of infected erythrocytes and the subsequent adherence to the vascular lining. One such syndrome is placental malaria. Approximately 25 million pregnancies are at risk of placental malaria infections in sub-Saharan Africa each year. In endemic areas the prevalence of infected placentas is high; one out of four pregnant women living in high-transmission areas is estimated to have placental infection at delivery. A vaccine preventing placental malaria will reduce mortality and morbidity for the new-born and can co-exist with a general malaria vaccine, and act in synergy with other malaria control measures such as insecticide-treated nets (ITNs) and intermittent preventive treatment during pregnancy (IPTp), reducing the disease burden originating from malaria.
The adherence to the vascular lining is mediated by a family of proteins called Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1), encoded by var genes, of which there are about 60 in each genome. Naturally acquired protective antibodies block the binding between infected red blood cells and receptors on vascular endothelium. A specific PfEMP1, VAR2CSA, has been identified as the parasite protein responsible for the binding of infected erythrocytes in placenta. Studies have since shown that parasites isolated from infected placentas express VAR2CSA in high quantities, and that this gene family is relatively conserved. Only women who have had placental malaria have substantial levels of protective antibodies against the VAR2CSA protein and the levels of antibodies are acquired as a function of their parity. Furthermore, women who have acquired VAR2CSA-specific antibodies give birth to healthier babies that are on average 450 g heavier than those born from women without these protective antibodies. As the interaction between the parasite protein VAR2CSA and chondroitin sulphate A (CSA) in the human placenta is a key element in the pathogenesis of placental malaria, a vaccine should elicit immunoglobulin that block this interaction. Therefore the aim of the PAMVAC is to protect foetus and mother against the adverse effects of placental malaria during pregnancy by interfering with infected erythrocyte binding to CSA in placental tissue.

Project Objectives
The objectives of the PlacMalVac FP7 project is the clinical development of a VAR2CSA based vaccine against placental malaria, including the production and pre-clinical testing of the vaccine, a first in man phase Ia and Ib clinical trial, as well as preparation for a phase II trial.

Project Results:
Main results and achievements
Production and preclinical testing: The antigen is a complex 350 kDa protein consisting of seven domains. One smaller sub-unit of the antigen (ID1-ID2a) has been selected as the PAMVAC vaccine antigen based on the ability to induce immunoglobulin in animal models that are able to inhibit parasite adhesion to CSA. The inhibition is remarkable high against the homologous parasite strain but the antibodies are also cross-inhibitory, inhibiting adhesion of heterologous parasites strains. As the primary endpoint of the clinical trial is safety, the first choice of adjuvant was aluminium hydroxide due to the safety profile. As the vaccine efficacy eventually will rely on the ability to mount a high titre of antibodies and preferable a sustainable immunological memory response, a more potent second choice of adjuvants are two formulations of monophosphoryl lipid A (MPL) analogue glucopyranosyl lipid adjuvant (GLA); a stable oil emulsion (SE) and a liposome saponin (LSQ) in collaboration with the Infectious Disease Research Institute (IDRI), Seattle, US. After the sub-units of VAR2CSA to include in the vaccine had been selected the His and V5 tags that were used in preclinical research were removed and stable transfected S2 cell clones produced. The cell-clone that was developed into the research cell bank was selected on the basis of highest yield. The up-stream production refinement consisted of investigating several process parameters, such as media, temperature, harvest-time and production additives. The final criterion for refinements to the production process was robustness of expression. The downstream process was developed in parallel to the upstream development and determined to consist of a two-step chromatographic column purification developed to optimize purity and yield. The processes were transferred to a Contract Manufacturing Organisation (CMO) and consistency runs as well as up scaling was achieved successfully. A virus validation study was developed and determined to be performed on the engineering batch. The methods to monitor protein quality and stability were developed and verified, the final set of methods were chosen to consist of size exclusion HPLC, identity western blot, host cell protein western blot, reduced SDS-PAGE, non-reduced SDS-PAGE, OD280, free SH groups, glycan profile, endotoxin levels, residual DNA content and bio burden. The master cell bank was released in September 2014 and the testing included identity, sterility, mycoplasma, Spiro plasma, adventitious virus, bovine virus, porcine virus, circo virus, reverse transcriptase activity and human cell infectivity. Early during the development process the Swedish Medical Product Agency was approached for scientific advice on the processes and testing, and a kick off meeting with representatives from the Paul Erhlich Institute (PEI) in Germany was helpful prior to initiation of the engineering batch for the GMP batch. The engineering batch was performed in late September 2014 after which the GMP batch was released in March 2015. The toxicological safety study was performed as a repeat dose study in rabbit using the engineering batch was released in April 2015. The conclusion was that all regiments were well tolerated. Stability data on the API at 4º and -20º celcius has now been collected for one year and the PAMVAC vaccine is stable under these storage conditions.
The clinical trial outline: The Phase I study was determined to be a staggered, two-centre, dose-escalation trial. The trial will be conducted in two stages. One in Germany (first in man and dose escalation) and one in a malaria-endemic area in the target group (randomized, controlled, dose-finding). The first in man administration and dose escalation from 20 to 50 μg per injection of PAMVAC, adjuvanted with Alhydrogel or GLA-SE or GLA-LSQ will be done in healthy, malaria-naive adults in Germany. In the second stage, PAMVAC will be administered to healthy, malaria-exposed nulligravid women in Benin at doses of 50 and 100 μg, adjuvanted with Alhydrogel or GLA-SE. In the second stage, one group will receive placebo (physiological saline). Allocation to placebo, PAMVAC + Alhydrogel or PAMVAC + GLA-SE or PAMVAC + GLA-LSQ either 50 or 100 μg will be randomised (and open-label in Germany / double-blinded in Benin). All participants will receive three intramuscular injections in four-week intervals. Each dose-escalation is conditional on a positive safety assessment by the independent safety monitoring board (ISMB) and sponsor approval. One individual receiving each PAMVAC formulation will serve as sentinel. The sentinel will be injected one day before the rest of the group. Primary endpoints: Number of adverse events (Grade 1–3 and serious adverse events) possibly, likely and definitely related to vaccination formulation. Secondary: Area under the curve of anti-PAMVAC antibody concentration. Exploratory: Concentration of serum required to inhibit fifty per cent (IC50) of homologous and heterologous parasite strain infected erythrocytes binding to CSA; Concentration of PAMVAC-specific IgG1, IgG2, IgG3, and IgG4 concentration one month after last immunization; B-cell phenotyping; Fraction of PAMVAC-specific memory B-cells; Concentration of cytokines following ex vivo stimulation of peripheral blood mononuclear cells with PAMVAC. The investigational sites in Benin and Tübingen, as well as the facilities at the sponsor were subjected to assessment with favourable outcomes. The construction of the clinical trial site in Cotonou, Benin was initiated and completed in 2015.
Preparation for Phase II: Cohort studies: 275 nulligravidae have been included. Over the 11 months of the follow-up of this cohort, we observed 73 pregnancies. The main result is that women's fecundity in this region is higher than expected. In addition, the rate of non-inclusion or exclusion was very low. The monitoring of primigravidae' cohort was more complex than anticipated, and resulted in high and unexpected attrition (about 50%). However, the number of blood samples is likely to be sufficient to achieve reliable immunological findings for the preparation of Phase II. Anthropological survey: The interpretations of the purpose of the study have greatly hindered the progress of the project. The inadequacy of the information given to the participants in connection with the aims of the study could be involved, including raising suspicions and rumors leading to clustered refusals within the community. The investigation is ongoing to clarify the causes of mistrust on the part of the general population, families and women who participated in the study. Parasitology: The prevalence of P. falciparum infection is high among the nulligravid women recruited at base line (45%). This prevalence increases to reach 55% in the first trimester of pregnancy in primigravidae before falling to 16% after the initiation of IPTp. PAMVAC (ID1-DBL2x-ID2) variants expressed by placental parasites clustered in distinct phylogenetic clades while significant within-group diversity was detected. Signatures of selection detected that ID1-DBL2x-ID2 is primarily under balancing selection, confirming its role as an important epitope. Humoral immunity: The level of total IgG against the ID1-ID2 antigen was determined by ELISA among STOPPAM women at inclusion, at each of the 3 consecutive antenatal visits, and at delivery. The results highlighted a protective role of elevated plasma levels of specific IgG to ID1-ID2 on the risk of low birth weight. Among the PLACMALVAC cohorts, current major observations are that IgG specific to ID1-ID2 are found in a quater of nulligravid women before the onset of pregnancy, higher than expected. The seroprevalence of the IgG significantly increases during pregnancy in up to nearly 60% of women, then decline to basic levels one month after delivery. Cellular immunity: A preliminary analysis of data from 3 sequential samples taken during pregnancy from a sub-set of 12 primigravid women showed consistentcy in terms of the frequency of memory B cells detected with previously published data.

Potential Impact:
The potential impact
Global health impact: A vaccine against malaria in pregnancy addresses an urgent global health challenge that has proven very difficult to roll back. The treatment and prevention of placental malaria is currently pursued through the use of anti-malarial drugs and bed nets. The malaria drugs available to the market are compromised due to increasing drug resistance. In addition, in areas with stable transmission, placental malaria is predominantly sub-clinical. Hence, many pregnant women are not aware of being infected and do not seek treatment. In many instances these silent infections have serious clinical consequences for the foetus. Ideally placental malaria is best controlled through a vaccine. At the moment there are no placental malaria vaccines on the market or in clinical development. Several non-placental malaria vaccine candidates are in development but none of these are likely to be effective against placental malaria.
The highest coverage for a vaccine would be achieved by targeting girls below the age of five years who are already part of the World Health Organization (WHO) Expanded Programme on Immunization (EPI) currently reaching >70% of the target population. This would however, require that life-long protection can be achieved by vaccination during early childhood. If this duration of protection cannot be achieved, the target group will necessarily be adolescent girls, who are currently the targeted population for a Human Papilloma Virus (HPV) vaccine through the Program for Cervical Cancer Prevention. Targeting infants via the EPI gives a target population in sub-Saharan Africa of 15 million infant girls annually. The target population in South-East (SE) Asia would be 22.5 million infant girls. Vaccinating 11-12 year old girls, as for the HPV vaccine target population gives 10 and 20 million girls annually in Africa and SE Asia. In addition there would be a catch-up population, consisting of those women of child-bearing age, who have not received the vaccine. This group would consist of some 316 million girls/women aged up to 25 in Africa, and some 600-800 million in endemic areas of SE Asia. A pregnancy malaria vaccine can co-exist with a general malaria vaccine and will act in synergy with other malaria control measures such as ITNs and IPTp in reducing the total health and disease burden originating from malaria. The proposed work program will be the first vaccine program addressing the urgent need of tools against malaria in pregnant women. A successful vaccine will have enormous impact on women and child health in endemic countries.
Indirect vaccine development impact: A VAR2CSA vaccine will be the first vaccine targeting the pathogenic cyto-adhesion of P. falciparum malaria parasites. The work proposed in this application will have a broad impact on the general development of PfEMP1 based cyto-adhesion blocking vaccines, which is an area that has been and is being extensively supported by the EU. It will potential lead the way for development of compounds that can be used against cyto-adherent malaria parasites in children causing severe syndromes like for example cerebral malaria.
Impact on capacity building: The project is a close collaboration between scientists in Benin and in Europe. During the project we will transfer knowhow from Europe and exchange research personnel. In PlacMalVac we will do a phase Ib arm of the phase I clinical trial for the first time in Benin and prepare this site for a phase II clinical trial. This will have impact on other activities at UAC and will build up capacity for testing of other vaccines at this field site.
SME impact: ExpreS2ion strives to become a leading provider of solutions for cost effective production of complex antigens. This project will serve as an independent verification of ExpreS2ion’s ability to deliver on complex vaccine projects and it will drive the company’s development of the necessary infrastructure. The project will enable ExpreS2ion to optimize its technology for increased product yields at lower cost. This will greatly strengthen ExpreS2ion’s competitive position in its core market of vaccine production. As part of this project ExpreS2ion will expand its facilities to include a fully equipped downstream purification laboratory. Downstream capabilities are an integral part of vaccine process development and would therefore strengthen and expand ExpreS2ion. Strong ties to CMOs form a central part of ExpreS2ion’s expansion strategy, which requires the building of a CMO network capable of helping ExpreS2ion offer a complete vaccine production solution as well as creating co-marketing opportunities. Process transfer and management of the outsourced GMP manufacturing will further strengthen ExpreS2ion’s business model of offering a complete vaccine production solution through collaboration with CMOs. The selected CMO will also gain deep experience in using ExpreS2ion’s technology, thereby creating the opportunity for effective co-marketing and collaboration on future projects.
European and International added value: The research will lead to enhancement of already established networks of collaboration between centres of scientific excellence in EU Member States and partner institutions in low income countries. Development of a VAR2CSA vaccine has been a European priority for years and the major milestone of testing the vaccine in humans is now within reach. The project will emphasize the role of the EU as the world leading capacity within blood stage malaria vaccine development. The proposed project will have a high added value for all partners. In particular UCPH will benefit from a close collaboration with UAC and IRD in our research to develop malaria vaccine for children. Parallel activities will explore the possibilities in using the Expres2 platform to produce other malaria vaccine candidates from partner institutions – to the benefit of both the SME and the University partners.

List of Websites:
http://cmp.ku.dk/collaborations/placmalvac/

Contact

Tine Mathiesen, (Head of Department)
Tel.: +45 35320478
Fax: +45 35324612
E-mail
Record Number: 189665 / Last updated on: 2016-10-13
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