Stimulation of cholesterol efflux inhibits herpesvirus nuclear egress

Cholesterol in herpesvirus envelopes and host membranes supports membrane fusion during virus entry. However, relatively little is known about how cholesterol affects other aspects of the viral replication cycle. Here, using an infection model focused on reactivation from latency, we demonstrate that depleting intracellular cholesterol inhibits the production of infectious Kaposi's sarcoma-associated herpesvirus (KSHV) virions. Treatment of latently infected cells with the liver X receptor α (LXRα) agonist 22(R)-hydroxycholesterol (22OH) increased expression of sterol response genes, including the cholesterol efflux pump ATP binding cassette subfamily A member 1 (ABCA1), and triggered lytic reactivation and sharp reductions in the levels of intracellular cholesterol. Using a proteomics approach, by late stages of replication, we observed diminished viral protein accumulation and significant alterations in host protein expression, including proteins regulating the cell cycle and innate immune responses. Cholesterol poor conditions led to the accumulation of defective capsids in the nucleus and a reduction in viral particles accessing the cytoplasm. This effect on viral egress suggested functional defects in the conserved herpesvirus nuclear egress complex (NEC), comprised of two viral proteins that accumulate at the inner nuclear membrane and facilitate primary envelopment. We investigated the effects of 22OH on herpes simplex virus (HSV) replication and NEC protein trafficking. We found that 22OH inhibited HSV1 and HSV2 replication and spread in plaque reduction assays and impaired recruitment of NEC proteins UL31 and UL34 to the nuclear periphery. Taken together, these findings indicate that cholesterol efflux inhibits herpesvirus replication by interfering with nuclear egress.