Despite the many efforts made by the scientific community in the development of vaccine candidates
against dengue virus (DENV), no vaccine has been licensed up to date. Although the immunopathogenesis associated to the disease is a key factor to take into account by vaccine developers, the lack
of animal models that reproduce the clinical signs of the disease has hampered the vaccine progress.
Non-human primates support viral replication, but they are very expensive and do not show signs of
disease. Immunocompromised mice develop viremia and some signs of the disease; however, they are
not valuable for vaccine testing. Nowadays, immunocompetent mice are the most used model to evaluate
the immunogenicity of vaccine candidates. These animals are resistant to DENV infection; therefore, the
intracranial inoculation with neuroadapted virus, which provokes viral encephalitis, represents an alternative to evaluate the protective capacity of vaccine candidates. Previous results have demonstrated the
crucial role of cellular immune response in the protection induced by the virus and vaccine candidates
in this mouse encephalitis model. However, in the present work we are proposing that the magnitude
of the cell-mediated immunity and the inflammatory response generated by the vaccine can modulate
the survival rate after viral challenge. We observed that the intracranial challenge of naïve mice with
DENV-2 induces the recruitment of immune cells that contribute to the reduction of viral load, but does
not increase the survival rate. On the contrary, animals treated with cyclophosphamide, an immunosuppressive drug that affects proliferating lymphocytes, had a higher viral load but a better survival rate than
untreated animals. These results suggest that the immune system is playing an immunopathogenic role
in this model and the survival rate may not be a suitable endpoint in the evaluation of vaccine candidates
based on antigens that induce a strong cellular immune response.