Anti-collagen type II IgG titers in DBA/1 mice immunized with mimivirus proteins. Levels of serum IgG measured by ELISA against endogenous mouse collagen type II (CII) in mice immunized with PBS (Neg), bovine collagen type II (BovCII), mimivirus proteins (MV), marseillevirus proteins (MsV), or recombinant L71 protein (L71). Data represent three independent experiments with 10 to 21 mice per group. Horizontal bars show means ± standard errors of the means (*, P < 0.01).