Antibody dependent enhancement of frog virus 3 infection

Here we show that anti-FV3 serum present at the time of FV3 infection enhances infectivity of the virus in two non-immune teleost cell lines. We found that antibody dependent enhancement of FV3 was dependent on the Fc portion of anti-FV3 antibodies but not related to complement. Furthermore, the presence of anti-FV3 serum during an FV3 infection in a non-immune mammalian cell line resulted in neutralization of the virus. Our results suggest that a cell surface receptor specific to teleost cell lines is responsible for the enhancement.This report represents the first evidence of antibody dependent enhancement in iridoviruses. The data suggests that anti-FV3 serum can either neutralize or enhance viral infection and that enhancement is related to a novel antibody dependent enhancement pathway found in teleosts that is Fc dependent.Following a viral infection an immune response is elicited by the host, which includes both an innate and adaptive response. During the adaptive immune response, antibodies are produced that are designed to recognize and neutralize a pathogen. Typically, viral antibodies neutralize a virus by preventing the attachment of specific cell surface receptors with viral glycoproteins, while also activating the complement system. However, not all antibodies serve to reduce infectivity. Antibody dependent enhancement (ADE) occurs when viral antibodies enhance infectivity of a virus by promoting the attachment of viral particles to cells. Virus specific antibodies bind to viral particles to form complexes that can bypass normal routes of viral attachment and entry. The virus+antibody complex allows for increased viral entry or infection of cells that would not normally become infected. Virus+antibody complexes therefore result in a more efficient infection than with virus alone.There are several mechanisms of how ADE can occur. The most common mechanism of ADE is Fc receptor (FcR)-dependent [1]. In FcR-dependent ADE the virus+antibody complex binds to