Applications:The invention offers a novel method to screen anti-flavivirus antibodies in blood for neutralizing and replication-enhancing antibodies using Fc gamma R transformed macrophages. Although this invention is immediately applicable to dengue virus infection, in principle it is applicable to any viral pathogen whose replication may be enhanced by antibodies.Advantages:The invention offers simplicity and the prospect of an automated, high through-put alternative to both conventional virus plaque neutralization and immune enhancement assay. The method will offer a standardized format to replace current laborious methods to measure protective neutralizing and potentially undesirable immune-enhancing antibodies stimulated by natural infection or by candidate and established viral vaccine.