Palmitic acid analogs exhibit nanomolar binding affinity for the HIV-1 CD4 receptor and nanomolar inhibition of gp120-to-CD4 fusion

Hexadecanoic acid analogs as potential CviR-mediated quorum sensing inhibitors in Chromobacterium violaceum: an in silico study

Chromobacterium violaceum is a Gram-negative, rod-shaped and opportunistic human pathogen. C. violaceum is resistant to various antibiotics due to the production of quorum sensing (QS)-controlled virulence factor and biofilm formation. Hence, we need to find alternative strategies to overcome the antimicrobial resistance and biofilm formation in Gram-negative bacteria. QS is a mechanism in which bacteria's ability to regulate the virulence factors and biofilm formations leads to disease progression. Previously, hexadecanoic acid was identified as a CviR-mediated quorum-sensing inhibitor. In this study, we aimed to discover potential analogs of hexadecanoic acid as a CviR-mediated quorum-sensing inhibitor against C. violaceum by using ADME/T prediction, density functional theory, molecular docking, molecular dynamics and free energy binding calculations. ADME/T properties predicted for analogs were acceptable for human oral absorption and feasibility. The highest occupied molecular orbitals and lowest unoccupied molecular orbitals gap energies predicted and found oleic acid with -0.3748 energies. Docosatrienoic acid exhibited the highest binding affinity -8.15 Kcal/mol and strong and stable interactions with the amino acid residues on the active site of the CviR protein. These compounds on MD simulations for 100 ns show strong hydrogen-bonding interactions with the protein and remain stable inside the active site. Our results suggest hexadecanoic acid analogs could serve as anti-QS and anti-biofilm molecules for treating C. violaceum infections. However, further validation and investigation of these inhibitors against CviR are needed to claim their candidacy for clinical trials.

A comprehensive review on targeting cluster of differentiation: An attractive strategy for inhibiting viruses through host proteins

Viral infections continue to pose a significant global public health threat. Targeting host proteins, such as cluster of differentiation (CD) macromolecules, may offer a promising alternative approach to developing antiviral treatments. CDs are cell-surface biological macromolecules mainly expressed on leukocytes that viruses can use to enter cells, thereby evading immune detection and promoting their replication. The manipulation of CDs by viruses may represent an effective and clever means of survival through the prolonged co-evolution of hosts and viruses. Targeting of CDs is anticipated to hinder the invasion of related viruses, modulate the body's immune system, and diminish the incidence of subsequent inflammation. They have become crucial for biomedical diagnosis, and some have been used as valuable tools for resisting viral infections. However, a summary of the structures and functions of CDs involved in viral infection is currently lacking. The development of drugs targeting these biological macromolecules is restricted both in terms of their availability and the number of compounds currently identified. This review provides a comprehensive analysis of the critical role of CD proteins in virus invasion and a list of relevant targeted antiviral agents, which will serve as a valuable reference for future research in this field.

Antitumor effect of algae silver nanoparticles on human triple negative breast cancer cells

In recent years, metallic nanoparticles have gained increasing attention due to their prospective applications in the field of nanomedicine, with increasing research into their use in cancer therapy. In this current research, we investigated the effect of green synthesized Silver Nanoparticles (AgNPs) capped with Noctiluca scintillans algae extract. The phytochemicals present in the shell of AgNPs were identified using GC-MS. Different compounds with anticancer activity such as n-hexadecanoic acid, beta-sitosterol, stigmasterol and palmitic acid were detected among others. The effects of Algae-AgNPs synthesized were tested on MDA-MB-231 human breast cancer cells and HaCat human keratinocyte normal cells. Cell viability assay revealed a time and dose-dependent effect against breast cancer cells with a less potent effect against normal cells. The cell viability reduction is not attributed to a cytotoxic nor an antiproliferative effect of the Algae-AgNPs as attested by LDH release and BrdU incorporation. Algae-AgNPs exhibited an exceptional ability to specifically induce apoptosis in cancer cells and not normal cells. The observed effects are not attributed to the AgNPs, as demonstrated by the lack of impact of the Starch-AgNPs (used as a negative control) on cell survival and apoptosis. In addition to that, we show that Algae-AgNPs significantly reduced tumor cell migration by downregulation of matrix metalloprotease-9 levels. In vivo, the breast cancer xenograft model showed a significant reduction of tumor growth in mice treated with Algae-AgNPs. These findings highlight the promising potential of the green synthesized AgNPs as a safe targeted therapy for cancer treatment.

Carbosilane dendrons with fatty acids at the core as a new potential microbicide against HSV-2/HIV-1 co-infection

Herpes simplex virus type 2 (HSV-2) and human immunodeficiency virus type 1 (HIV-1) represent the two most frequent sexually transmitted infections (STI) worldwide. Epidemiological studies suggest that HSV-2 increases the risk of HIV-1 acquisition approximately 3-fold mainly due to the clinical and immunological manifestations. In the absence of vaccines against both STI, the development of new preventive strategies has become essential for further studies. We performed the screening of six novel polyanionic carbosilane dendrons to elucidate their potential activity against HSV-2/HIV-1 co-infection and their mechanism of action. These new nanoparticles are carbosilane branched dendrons from first to third generation, with palmitic or hexanoic fatty acids as the core and capped with sulfonate groups, named G1_d-STE2Hx, G2_d-STE4Hx, G3_d-STE8Hx, G1_d-STE2Pm, G2_d-STE4Pm and G3_d-STE8Pm. G3_d-STE8Hx and G3_d-STE8Pm carbosilane branched dendrons showed high viability. These dendrons also showed a great broad-spectrum antiviral activity, as well as a suitable efficacy against HIV-1 even if the mucosal disruption occurs as a consequence of HSV-2 infection. Our results exert high inhibition against HSV-2 and HIV-1 by blocking the entry of both viruses with the median effective concentration EC₅₀ values in the nanomolar range. Additionally, G3_d-STE8Hx and G3_d-STE8Pm retained their anti-HSV-2/HIV-1 activity at different pH values. G3_d-STE8Hx and G3_d-STE8Pm dendrons may be potential candidates as dual-acting microbicides against HSV-2/HIV-1 co-infection.

Development of potent and long-acting HIV-1 fusion inhibitors

BACKGROUND

T20 (enfuvirtide) is the first approved HIV entry inhibitor and currently the only viral fusion inhibitor, but its low efficacy and genetic barrier to resistance significantly limit its application, calling for a next-generation drug.

DESIGN

On the basis of the M-T hook structure, we recently developed a short-peptide named HP23, which mainly targets the deep pocket site of gp41 and possesses highly potent antiviral activity. To improve the pharmaceutical properties of a peptide-based inhibitor, we modified HP23 by different classes of lipids including fatty acid, cholesterol, and sphingolipids. To avoid the potential problem of oxidation, the methionine residue in the M-T hook sequence of HP23 was replaced with leucine.

METHODS

Peptides were synthesized and their anti-HIV activity and biophysical properties were determined.

RESULTS

A group of lipopeptides were generated with greatly improved anti-HIV activity. Promisingly, a fatty acid-conjugated lipopeptide named LP-11 showed potent and broad inhibitory activity against diverse primary HIV-1 isolates and clinically drug-resistant mutants, and it had dramatically increased ex-vivo antiviral activity and extended half-life. Also, LP-11 displayed highly enhanced α-helicity and thermal stability, and it was physically stable under high temperature and humidity.

CONCLUSION

LP-11 has high potentials for clinical development and it can serve as an ideal tool for exploring the mechanisms of HIV-1 fusion and inhibition.

Evaluation of potential genotoxicity of HIV entry inhibitors derived from natural sources

AIDS is a global pandemic that has seen the development of novel and effective treatments to improve the quality of life of those infected and reduction of spread of the disease. Palmitic Acid (PA), which we identified and isolated from Sargassum fusiforme, is a naturally occurring fatty acid that specifically inhibits HIV entry by binding to a novel pocket on the CD4 receptor. We also identified a structural analogue, 2-bromopalmitate (2-BP), as a more effective HIV entry inhibitor with a 20-fold increase in efficacy. We have used the structure-activity relationship (SAR) of 2-BP as a platform to identify new small chemical molecules that fit into the various identified active sites in an effort to identify more potent CD4 entry inhibitors. To validate further drug development, we tested the PA and 2-BP scaffold molecules for genotoxic potential. The FDA and International Conference on Harmonisation (ICH) recommends using a standardized 3-test battery for testing compound genotoxicity consisting of the bacterial reverse mutation assay, mouse lymphoma assay, and rat micronucleus assay. PA and 2-BP and their metabolites tested negative in all three genotoxicty tests. 2-BP is the first derivative of PA to undergo pre-clinical screening, which will enable us to now test multiple simultaneous small chemical structures based on activity in scaffold modeling across the dimension of pre-clinical testing to enable transition to human testing.

Amphipathic properties of HIV-1 gp41 fusion inhibitors

Small molecule inhibition of HIV fusion has been an elusive goal, despite years of effort by both pharmaceutical and academic laboratories. In this review, we will discuss the amphipathic properties of both peptide and small molecule inhibitors of gp41-mediated fusion. Many of the peptides and small molecules that have been developed target a large hydrophobic pocket situated within the grooves of the coiled coil, a potential hotspot for inhibiting the trimer of hairpin formation that accompanies fusion. Peptide studies reveal molecular properties required for effective inhibition, including elongated structure and lipophilic or amphiphilic nature. The characteristics of peptides that bind in this pocket provide features that should be considered in small molecule development. Additionally, a novel site for small molecule inhibition of fusion has recently been suggested, involving residues of the loop and fusion peptide. We will review the small molecule structures that have been developed, evidence pointing to their mechanism of action and strategies towards improving their affinity. The data points to the need for a strongly amphiphilic character of the inhibitors, possibly as a means to mediate the membrane - protein interaction that occurs in gp41 in addition to the protein - protein interaction that accompanies the fusion-activating conformational transition.

Inhibition of HIV-1 infection in ex vivo cervical tissue model of human vagina by palmitic acid; implications for a microbicide development

Background

Approximately 80% of all new HIV-1 infections are acquired through sexual contact. Currently, there is no clinically approved microbicide, indicating a clear and urgent therapeutic need. We recently reported that palmitic acid (PA) is a novel and specific inhibitor of HIV-1 fusion and entry. Mechanistically, PA inhibits HIV-1 infection by binding to a novel pocket on the CD4 receptor and blocks efficient gp120-to-CD4 attachment. Here, we wanted to assess the ability of PA to inhibit HIV-1 infection in cervical tissue ex vivo model of human vagina, and determine its effect on Lactobacillus (L) species of probiotic vaginal flora.

Principal Findings

Our results show that treatment with 100–200 µM PA inhibited HIV-1 infection in cervical tissue by up to 50%, and this treatment was not toxic to the tissue or to L. crispatus and jensenii species of vaginal flora. In vitro, in a cell free system that is independent of in vivo cell associated CD4 receptor; we determined inhibition constant (Ki) to be ∼2.53 µM.

Significance

These results demonstrate utility of PA as a model molecule for further preclinical development of a safe and potent HIV-1 entry microbicide inhibitor.

Synthesis and biological evaluation of fatty acyl ester derivatives of 2',3'-didehydro-2',3'-dideoxythymidine

A number of 5'-O-fatty acyl derivatives of 2',3'-didehydro-2',3'-dideoxythymidine (stavudine, d4T) were synthesized and evaluated for anti-HIV activities against cell-free and cell-associated virus, cellular cytotoxicity, and cellular uptake studies. The conjugates were found to be more potent than d4T. Among these conjugates, 5'-O-12-azidododecanoyl derivative of d4T (2), displaying EC(50) = 3.1-22.4 μM, showed 4- to 9-fold higher activities than d4T against cell-free and cell-associated virus. Cellular uptake studies were conducted on CCRF-CEM cell line using 5(6)-carboxyfluorescein derivatives of d4T attached through β-alanine (9) or 12-aminododecanoic acid (10) as linkers. The fluorescein-substituted analog of d4T with long chain length (10) showed 12- to 15-fold higher cellular uptake profile than the corresponding analog with short chain length (9). These studies reveal that conjugation of fatty acids to d4T enhances the cellular uptake and anti-HIV activity of stavudine.