Inhibition of HIV-1 replication by a peptide dimerization inhibitor of HIV-1 protease

Peptides based on the amino (N) and carboxy (C)-terminal regions of human immunodeficiency virus type-1 (HIV-1) protease and on the C-terminus of p6* can inhibit HIV-1 protease activity by preventing dimerization. We developed a peptide dimerization inhibitor, P27, that included these domains and a cell permeable domain derived from HIV-1 Tat. P27 inhibited wild type (WT) and protease inhibitor (PI)-resistant HIV-1 protease (IC50: 0.23-0.32 microM). Kinetic and biochemical assays confirmed that P27 inhibits protease dimerization. Fluorescein-labeled peptide accumulated in MT-2 cells and protected acutely infected MT-2 cells from HIV-1-induced cytotoxicity (IC50: 5.1 microM). P27 also inhibited p24 accumulation from H9 and U937 cells chronically infected with WT or PI-resistant HIV-1. Immunoblot analysis on the supernatants and infected cells revealed a block in virus release by P27 rather than an inhibition of polyprotein processing. However, inhibition of p55 Gag processing by active-site inhibitors was enhanced when combined with P27, suggesting that P27 can affect protease function in maturing virions. Although P27 was rationally designed to block dimerization of the mature HIV-1 protease, the effects of P27 on HIV-1 replication may be related to partial inhibition of Gag-Pol processing leading to a disruption in virus release.     

去甲斑蝥素体外抗HIV-1作用研究

为从天然产物中获得与现有药物作用机制不同、结构新颖的有效抗HIV-1化合物, 在细胞培养系统 及体外无细胞复制酶系统中进行抗HIV-1药物筛选。结果发现, 去甲斑蝥素 (NCTD) 在传代和原代淋巴细胞培养系统内抑制HIV-1实验室传代病毒株的p24抗原, 在人外周血单核细胞培养系统内对临床分离的AZT敏感病毒株和耐药病毒株也有抑制作用, 半数抑制浓度为1.8～20.2 μmol·L⁻¹, 在MT-4细胞培养系统内与AZT合用的联合指数<0.3, 具有明显的协同抗HIV-1作用, 但在体外NCTD对HIV-1逆转录酶、整合酶和蛋白酶均无抑制作用。由于NCTD结构简单, 不同于现有结构类型的抗HIV-1药物, 如经修饰改造并优化, 可望获得高效低毒的新型抗HIV-1化合物。     

Inhibition of replication of primary HIV-1 isolates in huPBL-NOD/Scid mice by antibodies from HIV-1 infected patients

Although a limited number of HIV-infected patients have broadly neutralizing antibodies, it has not been examined whether these antibodies can protect against infection with primary virus in vivo. Here we screened the plasma of 23 HIV-1-infected patients for broadly neutralizing antibodies. Purified antibodies from subjects with broad and more narrow responses were administered to huPBL-NOD/Scid mice that were subsequently challenged with primary viruses of clade A, B and CRF01_AE. Although we observed a lack of correlation between the data from the in vitro neutralization assay and the results from the passive immunization experiments, we report for the first time that antibodies from HIV-infected persons can inhibit replication of primary virus isolates in an animal model.     

Inhibition of HIV-1 by fusion inhibitors

The envelope glycoprotein complex (Env) is responsible for entry of the human immunodeficiency virus type 1 (HIV-1) into cells by mediating attachment to target cells and subsequent membrane fusion. Env consists of three gp120 subunits that mediate receptor and co-receptor attachment and three gp41 subunits responsible for membrane fusion. Several steps of the entry process can serve as drug targets. Receptor antagonists prevent attachment of gp120 to the receptor or co-receptor and conformational changes within gp41 required for membrane fusion can be inhibited by fusion inhibitors. Enfuvirtide (T20, Fuzeon) is a peptide based on the gp41 sequence and is the only approved fusion inhibitor. It prevents membrane fusion by competitively binding to gp41 and blocking the formation of the post-fusion structure. New generations of T20-like peptides have been developed with improved potency and stability. Besides T20 and derivatives, other fusion inhibitors have been developed that target different domains of gp41. Here we discuss the development of fusion inhibitors, their mode of action and their potential for incorporation in future drug regimens.     

Inhibition of HIV-1 replication by the combined action of anti-gp41 single chain antibody and IL-16

HIV-1 replication is inhibited in T cells transfected with an anti-gp41 single chain antibody (ScFv) or IL-16. These two molecules target totally different events in the HIV-1 replication cycle. The present study shows that HIV-1 replication is inhibited to a substantially greater extent and for a longer duration in cells transfected with both anti-gp41 and IL-16 than with either molecule alone. It is concluded that anti-gp41 and IL-16 act in a synergistic fashion to inhibit HIV-1 replication.     

Inhibition of HIV-1 protease by a boron-modified polypeptide

Six boronated tetrapeptides with the carboxy moiety of phenylalanine replaced by dihydroxyboron were synthesized, and their activities against human immunodeficiency virus 1 (HIV-1) protease subsequently investigated. The sequences of these peptides were derived from HIV-1 protease substrates, which included the C-terminal part of the scissile bond (Phe-Pro) within the gag-pol polyprotein. Enzymatic studies showed that these compounds were competitive inhibitors of HIV-1 protease with K(i) values ranging from 5 to 18 microM when experiments were performed at high enzyme concentrations (above 5 x 10(-8) M); however, at low protease concentrations inhibition was due in part to an increase of the association constants of the protease subunits. Ac-Thr-Leu-Asn-PheB inhibited HIV-1 protease with a K(i) of 5 microM, whereas the non-boronated parental compound was inactive at concentrations up to 400 microM, which indicates the significance of boronation in enzyme inhibition. The boronated tetrapeptides were inhibitory to an HIV-1 protease variant that is resistant to several HIV-1 protease inhibitors. Finally, fluorescence analysis showed that the interactions between the boronated peptide Ac-Thr-Leu-Asn-PheB and HIV-1 protease resulted in a rapid decrease of fluorescence emission at 360 nm, which suggests the formation of a compound/enzyme complex. Boronated peptides may provide useful reagents for studying protease biochemistry and yield valuable information toward the development of protease dimerization inhibitors.     

Inhibition of HIV-2 protease by HIV-1 protease inhibitors in clinical use

Over the past 10 years, protease inhibitors have been a key component in antiretroviral therapies for HIV/AIDS. While the vast majority of HIV/AIDS cases in the world are due to HIV-1, HIV-2 infection must also be addressed. HIV-2 is endemic to Western Africa, and has also appeared in European countries such as Portugal, Spain, and Estonia. Current protease inhibitors have not been optimized for treatment of HIV-2 infection; therefore, it is important to assess the effectiveness of currently FDA-approved protease inhibitors against the HIV-2 protease, which shares only 50% sequence identity with the HIV-1 protease. Kinetic inhibition assays were performed to measure the inhibition constants (K(i)) of the HIV-1 protease inhibitors indinavir, nelfinavir, saquinavir, ritonavir, amprenavir, lopinavir, atazanavir, tipranavir, and darunavir against the HIV-2 protease. Lopinavir, saquinavir, tipranavir, and darunavir exhibit the highest potency with K(i) values of 0.7, 0.6, 0.45, and 0.17 nm, respectively. These K(i) values are 84, 2, 24, and 17 times weaker than the corresponding values against the HIV-1 protease. In general, inhibitors show K(i) ratios ranging between 2 and 80 for the HIV-2 and HIV-1 proteases. The relative drop in potency is proportional to the affinity of the inhibitor against the HIV-1 protease and is related to specific structural characteristics of the inhibitors. In particular, the potency drop is high when the maximum cap size of the inhibitors consists of very few atoms. Caps are groups located at the periphery of the molecule that are added to core structures to increase the specificity of the inhibitor to its target. The caps positioned on the HIV-1 protease inhibitors affect selectivity through interactions with distinct regions of the binding pocket. The flexibility and adaptability imparted by the higher number of rotatable bonds in large caps enables an inhibitor to accommodate changes in binding pocket geometry between HIV-1 and HIV-2 protease.     

应用假病毒技术研究HIV-1复制抑制剂

建立以HIV-1复制为靶点的细胞水平假病毒药理筛选模型，并运用该模型筛选化合物库中随机选取的化合物。细胞水平的HIV-1假病毒药理筛选模型是应用水泡性口膜炎病毒的外壳糖蛋白(vesicular stomatitis virus glycoprotein，VSV-G)包装HIV-1核心建立的，简称VSVG/HIV模型。细胞被VSVG/HIV感染后，病毒携带的报告基因的表达水平(荧光素酶活性或GFP阳性细胞比例)反映了HIV-1的复制水平。对HIV-1复制有抑制作用的化合物应用VSVG/MLV模型对其特异性地进一步检测。被感染细胞中报告基因的表达水平与病毒稀释度呈显著的剂量依赖效应。阳性药物齐多夫定(zidovudine，AZT)、拉米夫定(lamivudine，3TC)、去羟基苷(didanosine，DDI)可剂量依赖性地抑制HIV-1的复制，其IC₅₀分别为48.5 nmol·L^-1、 0.13 μmol·L^-1和1.73 μmol·L^-1，与文献报道一致。在随机筛选的500个化合物中有3个化合物可以抑制HIV-1的复制，IC₅₀分别为1.92、 5.38和3.39 μmol·L^-1，而对MLV的复制无影响。VSVG/HIV假病毒系统是一种安全、有效的针对HIV-1复制的药理筛选模型。当将此模型与VSVG/MLV模型联合使用时，可判断化合物作用的特异性。实验表明：3个化合物，2-甲硫基-5-(4-甲基苯并)酰胺基-1,3,4-噻二唑(化合物A)、N-(3-羟基苯基)-2-(4-异丁基苯基)丙酰胺(化合物B)和N-(4-甲基吡啶基)-4-甲基苯磺酰胺(化合物C)可以特异性抑制HIV-1的复制。     

Inhibition of HBV replication by theophylline

We have suggested recently that ATM-Rad3-Related (ATR) DNA damage signaling pathway, which responds to single-strand breaks in DNA, was activated in response to HBV infection. ATR knockdown cells showed decreased HBV DNA yields, implying HBV infection and replication activate and exploit the activated DNA damage response. Host cell proteins may constitute an attractive target for anti-HBV-1 therapeutics, since development of drug resistance against compounds targeting these cellular cofactor proteins is unlikely. In this study, we show that one of the clinically used compounds of ATR and ataxia telangiectasia-mutated (ATM) kinases inhibitor, theophylline (Tp), significantly reduced the yield of HBV DNA, HBsAg and HBeAg in HepG2215 cell culture system, furthermore, Tp could also suppress serum HBV DNA and HBsAg levels in the HBV-transgenic mice. Consistent with this result, immunohistology also showed reduced intensity of HBsAg staining on livers from Tp-treatment group. Taken together, these data indicated the feasibility of therapeutic approaches that target host cell proteins by inhibiting a cellular gene that was required for HBV replication and provided a potential approach for the prevention and treatment of HBV infection.