Vaccination is a main measure for protecting chickens against Marek's disease,while it is not able to suppress the infection,proliferation,transmission,and virulence enhancement on Marek's disease virus.Inhibiting the proliferation of Marek's disease virus in chicken is therefore an im-portant option for enhancing defense effectiveness.In this study,a compound,DUBs-IN-1,was found to inhibit the activity of MDV049,a protease encoded by Marek's disease virus,via screening a protease inhibitor library using MDV049 as target and ubiquitin probe.Molecular docking re-vealed that DUBs-IN-1 can interact with the residues which formed the catalytic pocket of MDV049,blocking the interaction between Ub substrate and the catalytic center of MDV049,then suppress the activity of MDV049 with competitive inhibition.Using the CPE model,it was found that DUBs-IN-1 at the concentration of 0.35 and 0.70 μmol/L significantly inhibited the CPE in-duced by Marek's disease virus in CEF cells.Quantitative analysis revealed that DUBs-IN-1 inhibi-ted the proliferation of Marek's disease virus in CEF cells(P＜0.01).Furthermore,it was found that the administration of 80 and 150 pg/(kg·d)of DUBs-IN-1 in chicken infected by Marek's disease virus significantly inhibited the proliferation of MDV in T cells(P＜0.01).In summary,this study demonstrated that the compound DUBs-IN-1 is able to inhibit the proliferation of Marek's disease virus in chicken cells,laying a theoretical and practical foundation for further de-velopment of the drugs against Marek's disease virus.

Metastasis and resistance are main causes to affect the outcome of the current anticancer therapies. Heat shock protein 90 (Hsp90) as an ATP-dependent molecular chaperone takes important role in the tumor metastasis and resistance. Targeting Hsp90 and downregulating its expression show promising in inhibiting tumor metastasis and resistance. In this study, a redox-responsive dual-drug nanocarrier was constructed for the effective delivery of a commonly used chemotherapeutic drug PTX, and a COA-modified 4-arm PEG polymer (4PSC) was synthesized. COA, an active component in oleanolic acid that exerts strong antitumor activity by downregulating Hsp90 expression, was used as a structural and functional element to endow 4PSC with redox responsiveness and Hsp90 inhibitory activity. Our results showed that 4PSC/PTX nanomicelles efficiently delivered PTX and COA to tumor locations without inducing systemic toxicity. By blocking the Hsp90 signaling pathway, 4PSC significantly enhanced the antitumor effect of PTX, inhibiting tumor proliferation and invasiveness as well as chemotherapy-induced resistance in vitro. Remarkable results were further confirmed in vivo with two preclinical tumor models. These findings demonstrate that the COA-modified 4PSC drug delivery nanosystem provides a potential platform for enhancing the efficacy of chemotherapies.