Sequential production of IFN-alpha and immune-specific IFN-gamma by human mononuclear leukocytes exposed to herpes simplex virus

Abstract

Both viral-induced interferon (IFN-alpha) and immune interferon (IFN-gamma) were produced in cultures of human peripheral mononuclear leukocytes (PML) exposed to ultraviolet (UV) light-inactivated herpes simplex virus (HSV). Comparable IFN titers (100 to 300 U) were present in supernatant media from PML of HSV-seropositive and -seronegative donors maintained for 2 days in culture. This "early" IFN was not immunologically specific and had the characteristics of IFN-alpha. In contrast, PML from 20 of 21 (95%) seropositive donors, but only 2 of 22 (9%) seronegative subjects, produced IFN in day-5 cultures that had been washed on day 2 followed by the addition of fresh media without UV-HSV (p < 0.0001). In addition,the geometric mean IFN titer of 35 U present in media from day 5 cultures of seropositive donors was significantly higher (p < 0.0001) than those from seronegative subjects (<10 IFN U). This "late" IFN was defined as immunologically specific by virtue of its being present almost exclusively in PML cultures from seropositive donors. Late-appearing, HSV-induced, immunospecific IFN-gamma had antigenic characteristics of both viral-induced IFN-aand mitogen-induced IFN-gamma. A considerable degree of overlapping sensitivity to anti-IFN-alpha and anti-IFN-gamma antibody existed in late IFN, but was not seen in standard, control specimens. The latter finding suggests that the possible existence of an IFN of antigenic character intermediate to IFN-alpha and IFN-gamma. Late IFN was not induced in PML cultures by UV-inactivated Newcastle disease virus (NDV). NDV did, however, induce high titers of early IFN-alpha in PML cultures of both HSV-seropositive and HSV-seronegative donors. HSV-stimulated lymphocyte blastic transformation occurred only in cultures of seropositive individuals, whereas none occurred in response to NDV. Delayed appearance of antiviral activity with the characteristics of IFN-gamma in HSV-stimulated PML cultures is a sensitive and specific measure of the human immune IFN response. Sequential synthesis of IFN-alpha and IFN-gamma in individual PML cultures provides an opportunity to examine regulation of IFN production in response to virus with intrinsic IFN-inducing properties.