Complement-Mediated Neutralization of Dengue Virus Requires Mannose-Binding Lectin

Avirutnan, Panisadee; Hauhart, Richard E.; Marovich, Mary A.; Garred, Peter; Atkinson, John P.; Diamond, Michael S.

MBL, a key pattern recognition plasma protein of the complement system, restricts pathogen infection by several mechanisms, including direct opsonization, activation of the lectin complement pathway, regulation of cytokine production, and amplification of Vero cell-derived DENV-2 was preincubated with 10% (vol/vol) serum from donor 2 in the absence or presence of an increasing percentage of fresh (E) or heat-inactivated (F) serum from donor 1, with or without 1 M mannose. Neutralization was calculated based on the reduction of the number of plaques in a given condition compared to the value for heat-inactivated serum from donor 2. Error bars indicate SEM for 3 to 6 independent experiments performed in duplicate. Values that are statistically significant different are indicated by asterisks and brackets as follows: **, P Ͻ 0.01; ***, P Ͻ 0.001. adaptive immunity (14) . Prior studies established that MBL controls WNV infection in mice by binding N-linked glycans on viral structural proteins and activating the lectin pathway of complement (25, 34) . The results of our studies here show that MBL also restricts infection by DENV, a related flavivirus. Human MBL inhibited infection of all DENV serotypes by both complementdependent and complement-independent mechanisms. MBLmediated neutralization of DENV, however, was more efficient with virus generated in insect cells compared to virus generated in mammalian cells. Finally, the concentration of MBL in human serum, which varies among individuals due to common genetic polymorphisms in the human MBL2 gene (15), directly impacted neutralization of DENV.