Producing physicochemical property consensus alphavirus protein antigens for broad spectrum vaccine design

There is a pressing need for new vaccines against alphaviruses, which can cause fatal encephalitis (Venezuelan equine encephalitis virus (VEEV) and others) and severe arthralgia (e.g. Chikungunya virus, CHIKV). These positive-strand RNA viruses are diverse and evolve rapidly, meaning that the sequence of any vaccine should cover multiple strains that may be quite different from any previous isolate. Here, consensus proteins were produced to represent the common physicochemical properties (PCPs) of the epitope rich, B domain of the E2 envelope protein. PCP-consensus proteins were based on multiple strains of VEEV (VEEV_con) and CHIKV (CHIKV_con) or the conserved PCPs of 24 different alphaviruses (AllAV_con). The AllAV_con was altered to include binding sites for neutralizing antibodies of both VEEV and CHIKV strains (Mosaik_con). All four designed proteins were produced solubly in E. coli and purified. They formed the β-strand core expected from experimental structures of this region of the wild type E2 proteins as indicated by circular dichroism (CD) spectra. Furthermore, the CHIKV_con protein bound to a structure dependent, CHIKV neutralizing monoclonal antibody. The AllAV_con and Mosaik_con proteins bound to polyclonal antibodies generated during natural infection with either VEEV or CHIKV, indicating they contained epitopes of both serotypes. The Mosaik_con antigen induced antibodies in rabbit sera that recognized both the VEEV_con and CHIKV_con spike proteins. These PCP-consensus antigens are promising starting points for novel, broad-spectrum alphavirus vaccines.