Immunogenicity of Novel Consensus-based DNA Vaccines Against Chikungunya Virus

Chikungunya virus (CHIKV) is an emerging arbovirus and is an important human pathogen. Infection of humans by CHIKV can cause a syndrome characterized by fever, headache, rash, nausea, vomiting, myalgia, arthralgia and occasionally neurological manifestations such as acute limb weakness. It is also associated with a fatal haemorrhagic condition. CHIKV is geographically distributed from Africa through Southeast Asia and South America, and its transmission to humans is mainly through the Aedes aegypti species mosquitoes. The frequency of recent epidemics in the Indian Ocean and La Reunion islands suggests that a new vector perhaps is carrying the virus, as A. aegypti are not found there. In fact, a relative the Asian tiger mosquito, Aedes albopictus, may be the culprit which has raised concerns in the world health community regarding the potential for a CHIK virus pandemic. Accordingly steps should be taken to develop methods for the control of CHIKV. Unfortunately, currently there is no specific treatment for Chikungunya virus and there is no vaccine currently available. Here we present data of a novel consensus-based approach to vaccine design for CHIKV, employing a DNA vaccine strategy. The vaccine cassette was designed based on CHIKV capsid- and envelope-specific consensus sequences with several modifications, including codon optimization, RNA optimization, the addition of a Kozak sequence, and a substituted immunoglobulin E leader sequence. The expression of capsid, envelope E1 and E1 was evaluated using T7-coupled transcription/translation and immunoblot analysis. A recently developed, adaptive constant-current electroporation technique was used to immunize C57BL/6 mice with an intramuscular injection of plasmid coding for the CHIK-Capsid, E1 and E2. Analysis of cellular immune responses, including epitope mapping, demonstrates that electroporation of these constructs induces both potent and broad cellular immunity. In addition, antibody ELISAs demonstrate that these synthetic immunogens are capable of inducing high titer antibodies capable of recognizing native antigen. Taken together, these data support further study of the use of consensus CHIK antigens in a potential vaccine cocktail.