The preclinical testing of a formaldehyde inactivated Ross River virus vaccine designed for use in humans

Ross River virus was grown in industrial facilities in vaccine-certified Vero cells in the absence of serum, inactivated using standard formalin-inactivation protocols, treated with Benzonase to digest host cell DNA and purified on a sucrose gradient. Mice given two subcutaneous injections of 0.625 mu g of this vaccine or two doses of 0. 156 mu g vaccine with aluminium hydroxide adjuvant failed to develop a detectable viraemia after intravenous challenge with 10(6) TCID50 of the prototype strain of Ross River virus (T48). Guinea pigs immunised with one or two 10 mu g doses of vaccine with adjuvant also failed to develop a detectable viraemia following a similar challenge. The levels of neutralising antibody (neutralisation index 1.9-3.1) in the mice protected against challenge with 10(6) TCID(50)Ross River virus were similar to those in 16 former epidemic polyarthritis patients (1. 1-3.5) who had not experienced a second clinical infection with Ross River virus in the 20 years following their initial infection. (c) 2007 Elsevier Ltd. All rights reserved.