Desenvolvimento de uma formulação vacinal experimental contendo peptídeos multi-sorotipo do vírus da dengue incluídos em partículas pseudovirais quiméricas (VLPs) do vírus da hepatite B, e teste em murinos

Abstract

Dengue is the most relevant arthropod-borne human viral infectious disease worldwide. Dengue virus (DENV) is responsible for 50 to 100 million cases per year of the disease and 500.000 cases of the most severe forms (sometimes life-threatening) of the disease. Despite the high impact in public health, prophylactic measures are still based in controlling the mosquito vector, without any specific treatment developed to date. A vaccine is thus a priority. One of the main obstacles for developing a vaccine against dengue is the co-existence of four viral serotypes (DENV-1, 2, 3 e 4), which do not cross-protect against each other and can even act as disease-enhancers in case of an infection by a different viral serotype. In this study we have tried to develop a multivalent vaccine candidate based in two highly-conserved peptides from the sequence of the E protein (target of the virus-neutralizing antibodies). These peptides were fused to the external loop of the hepatitis B virus core protein (HBcAg) in an attempt to generate hepatitits B viral-like particles (VLPs) that could intensify the anti-DENV immune responses. Bacteria-produced recombinant proteins (HBcAg-Pep1 e HBcAg-Pep2) were purified and administered in Montanide ISA720 adjuvant individually or together as immunogens for C57BL/6. After the first dose, both proteins were immunogenic, in particular HBcAg-Pep2. The second dose Boosted all immune responses, and groups that received HBcAg-Pep2 reached antibody titers of 1/102400, while HBcAg-Pep1 innoculated animals displayed titers of 1/12800. Regarding those animals that received HBcAg-Pep1+2 immunogens together, antibody titers reached 1/25600 and 1/1600 respectively for each immunogen. Those are promising results when considering the need of inducing high levels of antibodies to neutralize DENV. The key point now is to determine the levels of neutralizing antibodies that are present in those animals as well as their capacity to protect the animals against a challenge with live DENVs.