MANNAN-BINDING PROTEIN AND BOVINE CONGLUTININ MEDIATE ENHANCEMENT OF HERPES-SIMPLEX VIRUS TYPE-2 INFECTION IN MICE

A broad range of plant lectins have recently been shown to inhibit the infectivity of herpes simplex virus type 1 (HSV-1) in vitro. We decid ed to investigate the role of mammalian lectins in infection with herp es simplex virus. Two lectins, conglutinin and mannan-binding protein (also called mannose-binding protein, MBP), belonging to the collectin family of lectins, were examined. Four week-old BALB/c mice were inje cted subcutaneously with 100 mu g bovine conglutinin or 50 mu g human MBP 1 day before intravenous infection with 5 x 10(4) PFU of herpes si mplex virus type 2 (HSV-2). A three-fold increase in virus titre of th e liver was observed on day 3 of the infection in the mice pretreated with conglutinin or MBP, whereas no effect was seen on days 1 and 5. I n a standard plaque assay using Vero cells we were not able to demonst rate reproducibly either infection inhibition or infection enhancement , when virus was pre-incubated with differing concentrations of the co llectins. The concentrations used were similar to those used by us in vivo, and by others in in vitro experiments showing inhibition of the infectivity of HSV-1 with plant lectins. In an ELISA with HSV-2 antige ns captured on anti-HSV-2 antibodies, calcium-dependent and carbohydra te inhibitable binding of the collectins was observed. Our results ind icate that the effect of endogenous mammalian collectins in vivo may n ot be neutralization as suggested by the data using plant lectins. Ins tead, the previously described opsonizing activity of the mammalian co llectins may provide the virions with an alternative port of entry int o cells leading to infection enhancement.