Herpes simplex virus-infected cells disarm killer lymphocytes.

Abstract

Human endothelial cells or human foreskin fibroblasts infected with herpes simplex viruses (HSVs) potently inhibit the lytic activity of natural killer cells and interleukin 2-activated killer cells. The inhibition occurs after as little as 8 hr of viral infection and requires contact between effector cells and HSV-infected targets. Inhibition evidently stems from direct blockade of killer cell function because killer cells placed atop HSV-infected targets rapidly become incapable of lysing subsequently added HL-60 or K-562 cells. The impairment of killer cell function is prevented when protein glycosylation in HSV-infected cells is blocked with tunicamycin. These studies may be relevant for understanding the persistence of herpes simplex virus infections and, further, suggest a mechanism for failed immune surveillance. A particularly relevant instance in which the immune system fails to eliminate a viral pathogen is that of human infection with herpes simplex virus (HSV). NK cells are necessary to control HSV in humans (10) but, nevertheless, fail to eradicate the infection. While investigating the role of killer lymphocytes in the recognition and elimination of HSV-infected cells, we made the unexpected observation that cytolytic activity of NK cells and LAK cells is remarkably suppressed following their contact with HSV-infected target cells. This down-regulation of cytotoxic effectors by cells infected with a common virus not only suggests a mechanism for persistence of HSV infections but also may serve as a model, in general, of failed immune surveillance. METHODSCell Culture. Human foreskin fibroblasts were cultured in tissue culture medium (RPMI-1640 with 25 mM Hepes supplemented with 2 mM L-glutamine, 100 units of penicillin per ml, and 100 ,ug of streptomycin per ml) and 10% (vol/vol) fetal bovine serum. Human umbilical vein endothelium was prepared and cultured as described (11). K-562 and HL-60 cell lines were grown in suspension culture in the same medium as above. They were passaged as necessary to maintain the density below 106 cells per ml.Virus Infection. HSV type 1 (HSV-1), strain 17 syn+, and HSV type 2 (HSV-2), strain HG52, were propagated and titrated in rabbit skin cells as described (12). Virus stock was prepared at 107 plaque-forming units (pfu)/ml of tissue culture medium with 5% calf serum and stored at -700C in small aliquots. Confluent monolayers of target cells were infected with HSV by overlaying with 100 ,ul of virus stock per well and incubating for 1 hr at 350C (multiplicity of infection 10 pfu per target cell). After the infecting incubation, the spent virus stock was removed and monolayers were overlaid with their original medium and incubated for various times before exposing them to killer cells.In experiments comparing the effects of adenovirus, strain AD4, to those of HSV, A549 cells were used as targets (13,14). Viral infection of A549 cells was carried out as above.Killer Cells. NK activity was assayed in freshly isolated peripheral blood mononuclear cells. From 60...

Innate Immune Response of the Human Host to Exposure with Herpes Simplex Virus Type 1: In Vitro Control of the Virus Infection by Enhanced Natural Killer Activity via Interleukin-15 Induction

“…However, it seems that the virus has also evolved strategies to escape this host response. Virus-infected cells have been reported to become resistant to NK cell-mediated killing in the later phase of infection, probably by expressing certain viral glycoproteins on the surface (23).…”

CTL Are Inactivated by Herpes Simplex Virus-Infected Cells Expressing a Viral Protein Kinase

“…Furthermore, several HSV genes have been shown to inhibit CTL-induced apoptosis of HSV-infected target cells (20 -24). An alternative mechanism has been described, wherein HSV-infected cells were capable of inhibiting the lytic function of various immune effector cells (25)(26)(27). In these models, when effector cells were incubated with HSV-infected fibroblasts, they lost the ability to lyse subsequently added target cells.…”

Cell-Type-Specific Tyrosine Phosphorylation of the Herpes Simplex Virus Tegument Protein VP11/12 Encoded by Gene UL46

“…Second, also like other viruses, HSV produces several antiapoptotic gene products (3,6,15,19,26), which can protect infected cells from cytolysis by killer lymphocytes (4,7,20). Third, NK cells and CTL are functionally inactivated (or disarmed) following contact with HSV-infected fibroblasts or epithelial cells (8,40). Such inactivation requires direct contact between the infected cell and the killer lymphocyte (8,40,44) and abrogates the ability of the lymphocyte to kill other target cells.…”

“…Third, NK cells and CTL are functionally inactivated (or disarmed) following contact with HSV-infected fibroblasts or epithelial cells (8,40). Such inactivation requires direct contact between the infected cell and the killer lymphocyte (8,40,44) and abrogates the ability of the lymphocyte to kill other target cells. The mechanism of HSV-induced lymphocyte inactivation is of great interest but remains to be fully defined.…”