ANXA5 and infection: All three isolates were then used to infect the same 10 cell lines at a multiplicity of infection (m.o.i.)of 1 and the susceptibility of each cell line to the virus was quantified by flow cytometry using an anti-alphavirus monoclonal antibody in parallel with determination of the induction of apoptosis also by flow cytometry after staining cells with FITC-conjugated Annexin V and propidium iodide.