A Novel Bromodomain Inhibitor XQ2 Reactivates HIV-1 Latent Reservoirs And Its Mechanism

BACKGROUNDDue to the attack to human CD4+ T lymphocytes by human immunodeficiency virus(HIV),AIDS(acquired immunodeficiency syndrome)mainly represents severe immune system damage.Highly active antiretroviral therapy(HAART)is a cooperative treatment using three or more antiviral drugs,which has significantly improved the quality of life and the prognosis of patients.However,due to the existence of HIV latency in patients,HIV infection cannot be completely cured.The"shock and kill" strategy refers to the reactivation of latent HIV through latency reversing agents(LRAs),and then combined with HAART antiviral drugs to kill the reactivated virus,thereby completely curing HIV or achieving the " HIV fuctional cure".Unfortunately,there is currently no LRAs in the clinic.An ideal LRA should be completely clear or reduce the latent reservoir with low cytotoxicity.Therefore,the development of novel HIV latency reversing agents with high efficiency and low toxicity is a hotspot in the HIV prevention field.OBJECTIVEResveratrol is a polyphenolic compound derived from a variety of plants.It has been reported that resveratrol has latent reactivation activity,but its clinical use is hindered due to its susceptibility to oxidation and side effects.In the current study,we designed a series of compounds according to the chemical structure of resveratrol.Among them,a novel compound XQ2 has a significant effect on HIV-1 latency reversal with low cytotoxicity.It provides a research idea to develop a new type of latency reversing agents.METHODS1.We verify the reactivation activity of XQ2 in different latently infected cell lines of HIV-1(J-Lat A2,J-Lat 10.6 and ACH2 cells)via flow cytometry,ELISA and real-time PCR.And the cell viability of XQ2 was analyzed by MTT assay.Moreover,the effects of XQ2 on T cell activation surface markers and host HIV-1 related receptor expression were evaluated by Flow cytometry.2.We analyze the synergistic reactivation of XQ2 with other latent reversing agents(SAHA,Prostratin and JQ1)by flow cytometry and ELISA.The antiviral activity of cART drugs was detected by luciferase assay.3.The mechanism of XQ2 were evaluated by Western Blot,protein overexpression and co-immunoprecipitation.RESULTS1.XQ2 enhances HIV transcription in latently infected cell lines in a dose-and time-dependent manner.Compared with JQ1 or resveratrol,it represents less cytotoxicity to latent cells and PBMCs,and does not trigger a gloal T cell activation and does not reduce host receptor and co-receptor expression.2.XQ2 has synergistic effects with SAHA and Prostratin.The reactivating virus generated by XQ2 can be significantly inhibited by cART drugs.3.XQ2 has a weak effect on promoting histone acetylation and a strong effect on promoting the P-TEFb pathway.Protein overexpression,docking and co-immunoprecipitation results indicate that XQ2 can combinate to BET bromodomain and inhibit the binding of BRD4 on the P-TEFb pathway lead to promote HIV transcriptional activation.This reactivation may be related to HIV-1 Tat protein and HSF1.CONCLUSIONA derivative of resveratrol,XQ2,has reactivation activity and low cytotoxicity.It does not cause T cell activation with a stable chemical structure.Its mechanism of reactivation may be promote transcription initiation by the P-TEFb pathway,binding to BRD4 and inhibiting combination of BRD4 protein and P-TEFb.XQ2 can synergize to SAHA and Prostratin.Therefore,XQ2 is expected to be developed into a novel BET inhibitor with high-efficiency and low-toxicity,which can be used in combination with other latency reversing agents and antiviral drugs to provide research ideas and theoretical support of a complete cure or "functional cure" for HIV.