CD40LG and infection: Consistent with previous studies on seroconversion after infection or immunization with filovirus antigen [38,39,40], the serum IgM titre showed a relatively low level and peaked at the early timepoint (5 weeks after first immunization of antigen), and showed a tendency to decrease thereafter, while the serum IgG titre remained high throughout the observation period (Figure 4b, Supplementary Figure S5a).