The ongoing Ebola epidemic in West Africa has claimed
over eleven thousand livesand has highlighted our unpreparedness to
counter emerging viral epidemics. While two recombinant vaccines have shown
promising results in clinical trials, we have developed an alternate subunit vaccine
candidate that could be called upon in the event that problems are encountered
with regard to safety or protection efficacy. Our subunit vaccine candidate is
based on a soluble version of the recombinant Ebola
glycoprotein (GP) stabilized in its pre-fusion conformation. This protein is
recognized by the neutralizing
monoclonal antibody KZ52 and all three ZMapp antibodies (currently employed as
a therapeutic for clinical treatment), indicating both GP1/2 and glycan cap
domains are available and are presented in the desired conformation. Immunization
via NanopatchTM (NP) microneedle delivery and intradermal injection were
compared in C57 black mice. We assessed the antibody response elicited in
immunized mice against Ebola virus (Zaire strain) using facilities at CSIRO’s
Australian Animal Health Laboratories in Geelong (AAHL). Promising plaque
reduction neutralization titres (PRNT50 = 1/80 sera dilution) were demonstrated.
Furthermore, we have shown this vaccine is
thermostable, retaining significant antigenicity after extended incubation at
37°C, indicating this vaccine strategy may not
require cold chain delivery.
In addition, the absence of any replicative elements ensures that it is likely
to have a safer profile than live recombinant vaccines.