Synergistic effect of human leukocyte interferon and nonoxynol 9 against herpes simplex virus type 2

The nonionic surfactant nonoxynol 9 (NP9), in combination with human alpha interferon, synergistically reduced the titer of herpes simplex virus type 2 (HSV-2) in vitro. The degree of synergy was highest at an interferon concentration of 10(3) IU/ml and an NP9 dilution of 1:1,500. We postulate that NP9 inactivates extracellular HSV-2, whereas interferon inhibits HSV-2 replication at the intracellular level.