An automated time-of-drug-addition assay to routinely determine the mode of action of HIV-1 inhibitors

Discovery of L15 as a novel Vif PROTAC degrader with antiviral activity against HIV-1

Viral infectivity factor (Vif) has been recognized as a new therapeutic target for human immunodeficiency virus-1 (HIV-1) infected patients. In our previous work, we have synthesized a novel class of Vif inhibitors with 2-amino-N-(5-hydroxy-2-methoxyphenyl)-6-((4-nitrophenyl)thio)benzamide scaffold, which show obvious activity in HIV-1 infected cells and are also effective against drug-resistant strains. Proteolytic targeting chimera (PROTAC) utilizes the ubiquitin-proteasome system to degrade target proteins, which is well established in the field of cancer, but the antiviral PROTAC molecules are rarely reported. In order to explore the effectiveness of PROTAC in the antiviral area, we designed and synthesized a series of degrader of HIV-1 Vif based on 2-amino-N-(5-hydroxy-2-methoxyphenyl)-6-((4-nitrophenyl)thio)benzamide scaffold. Among them, L15 can degrade Vif protein obviously in a dose-dependent manner and shows certain antivirus activity. Meanwhile, molecular dynamics simulation indicated that the ternary complex formed by L15, Vif, and E3 ligase adopted a reasonable binding mode and maintained a stable interaction. This provided a molecular basis and prerequisite for the selective degradation of the Vif protein by L15. This study reports the HIV-1 Vif PROTAC for the first time and represents the proof-of-concept of PROTACs-based antiviral drug discovery in the field of HIV/ acquired immune deficiency syndrome (AIDS).

Tetrandrine (TET) inhibits African swine fever virus entry into cells by blocking the PI3K/Akt pathway

African Swine Fever Virus (ASFV) infection causes an acute and highly contagious disease in swine, resulting in significant economic losses and societal harm worldwide. Currently, there are no effective vaccines or antiviral drugs available for ASFV. Tetrandrine (TET) is extracted from the traditional Chinese herb Stephania tetrandrae, possesses diverse biological functions such as anti-inflammatory, anti-tumor, and antiviral activities. The study comprehensively evaluated the anti-ASFV effect of TET and validated it through biological assays. The dose-dependent inhibition of TET against ASFV was confirmed and a novel mechanism of TET's anti-ASFV activity was elucidated. TET effectively inhibits ASFV during internalization by blocking macropinocytosis through the inhibition of the PI3K/Akt pathway. The specific inhibitor LY294002, targeting the PI3K/Akt pathway, exhibits similar antiviral activity against ASFV as TET. Furthermore, the inhibitory effect of TET against other viruses such as Lumpy Skin Disease Virus (LSDV) and Porcine Epidemic Diarrhea Virus (PEDV) was also identified. Our findings suggest that TET effectively inhibits ASFV and reveal the potential for broad-spectrum antiviral drugs targeting the PI3K/Akt pathway.

Cutting edge strategies for screening of novel anti-HIV drug candidates against HIV infection: A concise overview of cell based assays

The advent of Highly Active Antiretroviral Therapy has majorly contributed towards reducing the morbidity and mortality associated with HIV infected people, thus improving the quality of their life. Still, the eradication of HIV infection has not been achieved due to some important limitations such as non-adherence to therapy, cellular toxicity, restricted bioavailability of antiretroviral drugs and emergence of drug resistant viruses. Moreover, persistence of latent HIV-reservoirs even under antiviral-drug pressure is the major obstacle in HIV cure. Currently used antiretrovirals can suppress the viral replication in activated CD4⁺ cells, however, it has been observed that the available antiretroviral therapy appears inadequate to reduce latent reservoirs established in resting memory CD4⁺ T cells. Therefore, for eradication or reduction of latent reservoirs many immunotherapeutic and pharmacologic approaches including latency reversing agents are being studied constantly. Additionally, promising therapeutic strategies including discovery of novel drugs and drug targets are continuously being explored. Therefore, preclinical testing has become an important step of drug development process, continuously demanding innovative, but less time consuming evaluation strategies. Present review attempts to gather and line-up the information on existing cell-based methodologies applied for assessing drug candidates for their antiretroviral potential. Further, we intend to outline the advanced and reliable cell based methodologies that would expedite the process of discovery and development of antiretrovirals.

Axial Chiral Binaphthoquinone and Perylenequinones from the Stromata of Hypocrella bambusae Are SARS-CoV-2 Entry Inhibitors

A new axial chiral binaphtoquinone, hypocrellone (1), and a new perylenequinone, hypomycin F (2), were isolated from the stromata of Hypocrella bambusae, together with five known compounds, 3-7. The structures of 1 and 2 were assigned by spectroscopic and HRESIMS data analyses. The axial chirality of 1 was determined by electronic circular dichroism data analysis, and the absolute configurations of 2 and 3 were determined by X-ray crystallography. The axial chirality of 7 was determined by UV-induced photooxidation from 4. Compounds 1, 4, and 5 showed inhibitory activity against pseudotyped SARS-CoV-2 infection in 293T-ACE2 cells with IC₅₀ values of 0.17, 0.038, and 0.12 μM. Compounds 4 and 5 were also active against live SARS-CoV-2 infection with EC₅₀ values of 0.22 and 0.21 μM, respectively. Further cell-cell fusion assays, surface plasmon resonance assays, and molecular docking studies revealed that 4 and 5 could bind with the receptor-binding domain of SARS-CoV-2 S protein to prevent its interaction with human angiotensin-converting enzyme II receptor. Our results revealed that 4 and 5 are potential SARS-CoV-2 entry inhibitors.

P2X1 Selective Antagonists Block HIV-1 Infection through Inhibition of Envelope Conformation-Dependent Fusion

Purinergic receptors are well-established modulators of inflammatory processes, primarily through detection of extracellular nucleotides that are released by dying or infected cells. Emerging literature has demonstrated that inhibition of these inflammatory receptors can block HIV-1 productive infection and HIV-1-associated inflammation. The specificity of receptor type and mechanism of interaction has not yet been determined. Here, we characterize the inhibitory activity of P2X1 receptor antagonists, NF279 and NF449, in cell lines, primary cells, and a variety of HIV-1 envelope (Env) clades. NF279 and NF449 blocked productive infection at the level of viral membrane fusion, with a range of inhibitory activities against different HIV-1 Env isolates. A mutant virus carrying a truncation deletion of the C-terminal tail of HIV-1 Env glycoprotein 41 (gp41) showed reduced sensitivity to P2X1 antagonists, indicating that the sensitivity of inhibition by these molecules may be modulated by Env conformation. In contrast, a P2X7 antagonist, A438079, had a limited effect on productive infection and fusion. NF279 and NF449 interfered with the ability of the gp120 variable regions 1 and 2 (V1V2)-targeted broadly neutralizing antibody PG9 to block productive infection, suggesting that these drugs may antagonize HIV-1 Env at gp120 V1V2 to block viral membrane fusion. Our observations indicate that P2X1 antagonism can inhibit HIV-1 replication at the level of viral membrane fusion through interaction with Env. Future studies will probe the nature of these compounds in inhibiting HIV-1 fusion and the development of small molecules to block HIV-1 entry via this mechanism.IMPORTANCE While effective treatment can lower the severe morbidity and mortality associated with HIV-1 infection, patients infected with HIV-1 suffer from significantly higher rates of noncommunicable comorbidities associated with chronic inflammation. Emerging literature suggests a key role for P2X1 receptors in mediating this chronic inflammation, but the mechanism is still unknown. Here, we demonstrate that HIV-1 infection is reduced by P2X1 receptor antagonism. This inhibition is mediated by interference with HIV-1 Env and can impact a variety of viral clades. These observations highlight the importance of P2X1 antagonists as potential novel therapeutics that could serve to block a variety of different viral clades with additional benefits for their anti-inflammatory properties.