INTERNATIONAL CENTRE FOR GENETIC ENGINEERING AND BIOTECHNOLOGY
An international organisation dedicated to advances research and training in molecular
biology and biotechnology, with a special regard to the needs of the developing world
AREA Science Park, Padriciano, 99, 34149 Trieste, Italy - Tel.: +39-040-37571 Fax: +39-040-226555 www.icgeb.org
Priority number: RM2013A000458
PCT application number
PCT/IB2014/063588
Priority date 5.08.2013
Anti-Dengue virus genetic vaccine based on
the envelope protein ectodomains
Inventors: Oscar Burrone, Marco Bestagno, Monica Poggianella
Summary: the present invention refers to the field of biotechnology for anti-viral vaccine development.
In particular, the invention discloses a technique for the development of a genetic vaccine, effective
against the four known serotypes of Dengue virus.
Background of the invention: Dengue is a mosquito-borne infection representing one of the most
important infective agents in tropical and subtropical countries, causing a broad spectrum of symptoms,
from mild acute fever to severe hemorrhagic fever and fatal disease. The incidence of Dengue has
grown dramatically in recent decades. According to the WHO, over 2.5 billion people – over 40% of the
world's population – are now at risk from Dengue and current estimates indicate that there may be 50–
100 million dengue infections worldwide every year.
The virus is characterised by the existence of four distinct infective serotypes (DENV-1, -2, -3 and -4)
with very poor cross-protection among them. Sequential infection with viruses of different serotypes
increases the risk of developing severe disease as a consequence of enhanced infectivity mediated by
the presence of cross-reactive antibodies directed against non-neutralising epitopes, a mechanism
known as antibody-dependent enhancement (ADE). To date, neither a fully functional tetravalent
vaccine, nor an effective antiviral therapy is available. The development of an efficient vaccine for
Dengue virus, able to induce neutralising antibody responses for all four serotypes, represents a crucial
challenge.
Description of the invention: the viral E protein of the virus envelope, which is associated with viral
protein M, represents the target for neutralising antibodies. Protein E consists of three different and
discrete structural domains of which domain III (DIII) is the main one involved in eliciting neutralising
antibody responses to Dengue virus. The invention consists in the development of a genetic-based
vaccine where constructs encoding DIII, derived from all 4 serotypes, are engineered to induce the
synthesis of molecules with efficient immunogenic properties.
For a genetic vaccine aimed at inducing strong antibody responses, it is essential that the encoded
antigen protein is efficiently produced and secreted from the cells that have uptaken the construct.
Availability of soluble antigen is crucial to activate B cells for antibody production. When expressed
alone, DIIIs are inefficiently produced and secreted from mammalian cells. In our invention, each DIII
domain has been fused to an exogenous domain that allows very high expression and secretion levels
from mammalian cells for all four serotypes. In addition, the design of the antigen is dimeric, further
increasing activation and uptake by B cells. The novel genetic constructs, when administered to mice
through gene-gun delivery (the preferred intra-dermal delivery of plasmid DNA), induce long-lasting and
high-titre antibody responses. These antibodies are directed towards conformational epitopes, a typical
characteristic of DNA-based immunisations. All four genetic constructs are able to induce, either alone
or in different combinations, strong neutralising antibody responses.
Applications/Suggested use: the design of the genetic constructs of the present invention offers the
possibility to develop an effective and broad anti-Dengue virus vaccine covering all four serotypes.
So far, validation of the system has been achieved in mice, an animal model of immunisation.
Alternative delivery techniques can also be implemented.
Contact info: Dr. Oscar Burrone, [email protected]; Dr. Marco Bestagno,
[email protected], tel.: +39-040-375-7314/7311