FIG 6 .

MBL neutralizes insect cell-derived DENV serotypes 1, 3, and 4. (A) C6/36 cell-derived DENV-1, -3, and -4 were preincubated with 2% (vol/vol) wild-type mouse serum in the presence or absence of mannan (100 µg/ml). The virus was added to Vero cells, and infectivity was determined 48 hours (for DENV-1 and -4) or 60 hours (for DENV-3) later by a focus-forming assay. Neutralization was calculated based on reduction of the number of foci in a given condition compared to the value in heat-inactivated (HI) serum. Error bars indicate SEM for 5 or 6 independent experiments performed in duplicate. (B) C6/36 cell-derived DENV-1, -3, and -4 were incubated with purified human MBL (3 µg/ml) in the presence or absence of mannan (100 µg/ml) prior to addition to a monolayer of Vero cells. Data are presented as percent neutralization (percent reduction of the number of foci compared to the value in buffer alone) in a given condition. Error bars indicate SEM for 5 independent experiments performed in duplicate. (C) C6/36 cell-derived DENV-1, -3, and -4 were preincubated with 10% (vol/vol) naïve human serum (donor 1 or donor 2) in the absence or presence of 1 M mannose or 1.36 µg/ml purified human MBL. Neutralization was calculated based on reduction of the number of foci compared to the value in heat-inactivated (HI) serum. Error bars indicate SEM for 5 independent experiments performed in duplicate. Values that are significantly different are indicated by brackets and asterisks as follows: *, P < 0.05; **, P < 0.01; ***, P < 0.001.