Hydroxypropyl-Beta-Cyclodextrin (HPBCD) inhibits SARS-CoV-2 replication by modulating intracellular lipid dynamics

A multi-year scientific collaboration between Brasilian and American scientists from Federal University at Rio de Janeiro, Brazil, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD, USA and Department of Internal Medicine, Meharry Medical College, Nashville, TN, USA has led to significant improvements of understanding details of molecular working mechanism of antiviral efficacy of Hydroxypropyl-Beta-Cyclodextrin (HPBCD) against SARS-CoV-2. This theme remains timely even after introduction of COVID-19 vaccination. The SARS-CoV-2 infection has emerged as one of the most significant pandemics of the 21st century, infecting over 700 million people and resulting in more than 7 million deaths globally (1). Although the widespread implementation of vaccines has significantly reduced severe cases and mortality, the virus continues to circulate and can still cause severe disease, especially among unvaccinated individuals and those with comorbidities (2)

Bruno Braz Bezerra et al in a recent paper (3) investigated the molecular mechanisms underlying HPBCD antiviral activity against SARS-CoV-2 in vitro. Treatment of Vero cells with HPBCD was found to alter intracellular compartmentalization, as indicated by the redistribution of early endosome markers. Also, HPBCD treatment prior to SARS-CoV-2 inoculation promoted an accumulation of nucleocapsid protein at early time points after infection. Infected cells pretreated with HPBCD exhibited reduced cholesterol and lipid droplets content, potentially hampering the formation of new double-membrane vesicles. Consistently, viral replication complexes were scarcely detected in treated cells, which displayed disformed vesicle-like structures and lacked membrane-associated virus particles. Notably, HPBCD also reduced viral replication when administered after virus adsorption, although with lower efficacy, indicating interference with potentially multiple stages of the SARSCoV-2 life cycle. These findings suggest that HPBCD effectively impairs SARS-CoV-2 biosynthesis through multiple mechanisms with minimal cytotoxicity, supporting its potential as a promising antiviral candidate.

Important to mention that the same research group previously showed that HPBCD reduced the infectivity of distinct SARS-CoV-2 lineages, and inhibited virus replication in multiple host cells (4). The antiviral effect of HPBCD was more pronounced when the cells were treated prior to virus attachment, although post-adsorption treatment also reduced viral replication, to a lesser extent, suggesting that HPBCD affects distinct steps of virus biosynthesis.

The authors of present publication further investigated the mechanisms of HPBCD activity, particularly those in connection with the actual lipid content and organization. It was demonstrated that HPBCD altered the distribution of ACE2 and early endosome markers in intracellular compartments, suggesting disruption of early endosomal trafficking. (Author’s note: Is’nt it similar to the working mechanism of HPBCD described for treatment of Nieman-Pick type C disease?)

SARS-CoV-2-infected cells treated with HP-BCD showed early accumulation of the nucleocapsid protein (note: it is a protein which packages the positive-sense RNA genome of coronaviruses to form ribonucleoprotein structures enclosed within the viral capsid), and reduced levels of cholesterol along with a notable reduction in double-stranded RNA formation. HPBCD-treated cells also exhibited disrupted or deformed vesicle-like structures, with no evidence of membrane-associated virus formation, in contrast to the well-defined virus-containing membranous structures observed in untreated infected cells. These findings suggest that HPBCD impact intracellular organization of cholesterol and lipid bodies-dependent structures, thereby hampering SARS-CoV-2 replication. (See Figure below)

Figure. Cholesterol replenishment restores viral replication. Vero E6 cells were treated with 20 mM HPBCD incubated with or without cholesterol-loaded HPBCD. Cells were then washed and infected with SARS-CoV-2, Panels A, and B) The cellular cholesterol content was assessed prior to infection by filipin staining and confocal microscopy (Panel A), or by Amplex Red assay in cell lysates (Panel B). Panel C shows the viral genomic and subgenomic RNA levels which correlated to the actual viral infection. (note that BCD here stands for HPBCD)

Highlights of this article findings:

• HP-BCD impacts cellular ACE2 distribution and early SARS-CoV-2 replication.
• HP-BCD alters cholesterol and lipid droplets content and organization.
• HP-BCD impairs viral compartments formation in SARS-CoV-2-infected cells.
• HP-BCD affects both early and late stages of SARS-CoV-2 replication.
• HP-BCD inhibition of SARS-CoV-2 is partially reversed by cholesterol replenishment.

References:

1. WHO COVID-19 Dashboard. In:〈https://data.who.int/dashboards/covid19/cases〉
2. R.A. Evans et al. Impact of COVID-19 on immunocompromised populations during the omicron era: insights from the observational population-based INFORM study Lancet Reg. Health Eur., 35 (2023), Article 100747. https://doi.org/10.1016/j.lanepe.2023.100747
3. Bruno Braz Bezerra et al. Hydroxypropyl-Beta-Cyclodextrin (HP-BCD) inhibits SARS-CoV-2 replication by modulating intracellular lipid dynamics and preventing viral replication complex formation. Biomedicine & Pharmacotherapy 191 (2025) 118465. https://doi.org/10.1016/j.biopha.2025.118465
4. Bruno Brazezerra et al. Hydroxypropyl-beta-cyclodextrin (HP-BCD) inhibits SARS-CoV-2 replication and virus-induced inflammatory cytokines. Antivir. Res, 205 (2022),105373. https://doi.org/10.1016/j.antiviral.2022

Author of this blog is pleased to read among the authors of references 3. and 4., Dr. James Hildreth, an internationally recognized virologist, immunologist, who pioneered the cyclodextrin-assisted prevention and treatment of envelop virus infections. Dr. Hildreth is the 12th president and chief executive officer of Meharry Medical College, and he is considered one of the most influential HIV researchers in the world. (see: Rice, Valerie Montgomery; Payne, Kermit G. (2014).” Scientific Hero: Dr. James E. K. Hildreth”. Journal of Health Care for the Poor and Underserved. 24 (4A): 1–3. doi:10.1353/hpu.2014.0004..)