Introduction and Background of the Project

Introduction

The Dengue virus poses one of the most serious public health problems worldwide and the incidence of dengue infection has risen¹. Currently, 50% of the world’s population are at risk of dengue infection and nearly 50-100 million dengue infections occur every year in over 100 countries. The highly prevalent dengue virus is transmitted by the bites of mosquitoes that carry them.  Symptoms include flu-like fever and in certain cases, severe dengue hemorrhagic fever, which is a potentially lethal complication. 

The threat of dengue virus impacts not only residents of these regions, travelers to these areas, but can also inflict considerable economic losses through lost worker, business productivity and tourism revenues. 

There is no specific treatment for dengue. The prevailing methods to fight dengue virus infections including wearing personal protective clothing, use of mosquito nets, and insecticides. There are concerns over the efficacy of insecticides as mosquitos can develop resistance to them limiting their long-term practical use². 

Several dengue virus vaccines are currently under research and development. The most advanced one, Dengvaxia®, which is commercially available in limited countries provides partial protection against a specific serotype of dengue virus³.  Therefore, a more efficacious vaccine is urgently needed to combat dengue virus infections.

Project objective

Collaboration Partners, VLP Therapeutics, Japan’s National Institute of Infectious Diseases (NIID) and Institute of Tropical Medicine at Nagasaki University (ITM Nagasaki University), have developed a novel working vaccine to protect all forms of the dengue viruses (DENV 1-4).  Our goal is to develop a safe and much more effective vaccine. Most other dengue vaccine candidates are manufactured from weakened forms of the actual dengue virus, in which the virus can replicate in the body and induce adverse reactions. Our dengue vaccine is developed using a novel virus-like particle (VLP) technology, in which the vaccine does not replicate due to the lack of viral genomic RNA, resulting in a safer vaccine. VLP technology, a next generation vaccine platform, has a proven track record of safety and long-lasting efficacy^4,5. Our dengue vaccine would also be convenient to administer, globally available at any health clinic and require just a few doses over a short period of time.

Project design

We have developed four individual vaccines against each of the four dengue virus forms.

With critical design modifications to the VLP technology base, we developed our unique DENV 1-4 vaccines.  We have established the potency and efficacy of DENV 1-4 individual vaccines in mice. We will now test them in combinations, in mice, to determine which dose mixtures result in a balanced output of protective antibodies against all four DENVs.  We will subsequently test each for safety and efficacy in important human-relevant animal models.  Finally, we will also assess DENV 1-4 in vaccine combinations for safety and efficacy in these non-human primate models. 

How can your partnership (project) address global health challenges?

We believe our unique, next generation VLP vaccine technology can address the clear gap in effective therapeutics that are needed to protect against widespread DENV 1-4.  Current dengue control measures are inadequate, as the morbidity and mortality rates remain unacceptably high. 

Our preliminary data demonstrate that our VLP DENV 1-4 vaccines hold the promise of providing (1) strong efficacious protection, (2) convenient, short vaccine schedule of two doses over one month (versus three doses over 12 months required by the only commercially available vaccine). 

Moreover, our VLP technology platform is quickly adaptable: as viruses are known to mutate, developing resistance to therapeutics and insecticides, we can rapidly develop new vaccines to combat their changed states.

What sort of innovation are you bringing in your project?

Our VLP vaccine is a next-generation vaccine has high safety and effective profiles. We introduced amino acid mutations in DENV E to make it very stable based on structural design approaches to successfully create all four serotypes of VLP-based vaccines.

Therefore, the main novelty of our project rests with our powerful VLP vaccine platform: 

(1) Strong safety profile due to its non-replicating nature (limited to no adverse reactions due to the absence of use of weakened viral forms like most dengue vaccine candidates)

(2) Highly effective immune responses, since the vaccine resembles the appearance of the real virus. Its unique structure allows antigens resembling the virus to be exposed to our immune system.    

(3) A favorable consequence of stimulating high antibody production is the need for a few immunizations and a much shorter vaccination schedule.

(4) The flexible platform permits us to make rapid, consistent modifications enabling us to develop new vaccines, in short time, in the face of viral mutations or emerging new threats.

The project’s ultimate goal is to create a safe and effective DENV 1-4 vaccine that can be efficiently administered to safeguard people against DENV infections.

Role and Responsibility of Each Partner

The project will leverage complementary strengths from each Collaboration Partner at VLP Therapeutics, Japan’s NIID, and ITM Nagasaki University to conduct the project studies.  The parties will be responsible for completing specific studies as follows:

(1) VLP Therapeutics, as the designated grantee, will assume overall administrative supervisory role in this project, coordinating communication among all three parties.  VLP Therapeutics will also manufacture DENV 1-4 vaccines and test their safety and efficacy as vaccine combinatorial mixtures in mice. 

(2) NIID will conduct dose optimization studies, and measure the duration in which the antibodies remain in circulation in macaque monkey models and investigate the protective efficacy of the VLP DENV 1-4 vaccines in a maramoset monkey model, an established challenge model.   These non-human models are important to test in as their immune system are close representatives of the human system. 

(3) ITM Nagasaki University will measure the levels of DENV1-4 protective antibodies that are produced in mice and monkeys and investigate the protective efficacy of the VLP DENV 1-4 vaccines in a maramoset monkey model.  ITM is the one of the top research institutes for tropical infectious diseases and has strong research environment, experiences and resources to handle dengue viruses.

Others (including references if necessary)

1. http://apps.who.int/iris/bitstream/10665/75303/1/9789241504034_eng.pdf?ua=1

2. http://www.who.int/denguecontrol/control_strategies/en/

3. Capeding, M. R. et al. Clinical efficacy and safety of a novel tetravalent dengue vaccine in healthy children in Asia: a phase 3, randomised, observer-masked, placebo-controlled trial. Lancet 384, 1358-1365, doi:10.1016/S0140-6736(14)61060-6 (2014).

4. Harper, D. M. et al. Sustained efficacy up to 4.5 years of a bivalent L1 virus-like particle vaccine against human papillomavirus types 16 and 18: follow-up from a randomised control trial. Lancet 367, 1247-1255, doi:10.1016/S0140-6736(06)68439-0 (2006).

5. Mao, C. et al. Efficacy of human papillomavirus-16 vaccine to prevent cervical intraepithelial neoplasia: a randomized controlled trial. Obstet Gynecol 107, 18-27, doi:10.1097/01.AOG.0000192397.41191.fb (2006).

Final Report

1.  Project objective

Dengue is one of the most serious public health problems worldwide. There is no effective vaccine. Therefore, there is an urgent need for next-generation vaccines. VLP vaccines have shown to be safe and highly immunogenic because they mimic the conformation of the authentic virus but lack their genome. VLP can be administered to all populations including the most vulnerable population of infants and young children; populations who aren’t addressed by live-attenuated vaccines currently under development. The objective of this project is to conduct preclinical studies on our novel VLP vaccine leading to future clinical trials and potential commercialization.

2. Project design

We evaluated immune responses in mice and monkeys immunized with three different dose of our tetravalent dengue VLP vaccine to provide information about product safety, neutralizing antibody titer, duration of immunogenicity, antibody-dependent enhancement (ADE) activities and an understanding of the minimally effective dose for future clinical studies. We also evaluated protective efficacy of our vaccine in a dengue challenge model using marmosets to protect against dengue for all four serotypes. Finally, to define the mechanism of protection, we investigated whether or not immune IgG could protect against lethal challenge in a passive transfer animal model using AG129 immunodeficient mice.

3. Results, lessons learned

VLP Therapeutics partnered with Japan’s National Institute of Infectious Disease (NIID) and Nagasaki University. With support from the GHIT Fund, the collaboration team designed a tetravalent dengue vaccine and conducted preclinical studies .

The team evaluated the novel tetravalent VLP vaccine in mice and in two nonhuman primate species: cynomolgus macaque and marmosets. Immunogenicity was evaluated in mice and cynomolgus macaques and protective efficacy was evaluated in a most sensitive dengue challenge model using marmosets.

Our findings indicated that mice immunized with our VLP vaccine induced high neutralizing antibodies against all four serotypes. We found that the cynomolgus monkeys immunized with  three different doses showed high neutralizing antibody titers against all four serotypes and the neutralizing antibody titers were maintained for up to one year when the experiment terminated. . The marmosets immunized with the vaccine controlled challenges against all four dengue serotypes. To define the mechanism of protection, we administered purified immune-globulin from the immunized monkeys to an mice model using AG129 immunodeficient mice. The mice then received a lethal dengue challenge from which they were completely protected. In contrast, all mice that received purified IgG from control monkeys showed severe infection and died. These results indicate that humoral immune responses induced by our tetravalent VLPs are potent and confer protection against dengue infection.

Another critical safety issue with dengue vaccines is ADE. Our VLP vaccine is designed to reduce ADE. ADE was not observed with our novel tetravalent VLP dengue vaccine at the low dilution of sera (1:10) from the all the immunized cynomolgus monkeys for up to 1 year.

Based on these studies, we confirmed that our novel tetravalent VLP dengue vaccine is highly immunogenic with a strong safety profile. We expect this vaccine would be appropriate for all populations including infants and young children. This project’s ultimate goal is to create a safe and effective multi-valent dengue virus vaccine that can efficiently be administered to protect people against dengue virus infection. Based on these promising results, we will plan to manufacture this dengue vaccine to conduct clinical trials.