SARS-CoV-2 infects human primary cytotrophoblasts mainly through a non-canonical entry route
et al., Molecular Human Reproduction, doi:10.1093/molehr/gaag015, Feb 2026
HCQ for COVID-19
1st treatment shown to reduce risk in
March 2020, now with p < 0.00000000001 from 423 studies, used in 59 countries.
No treatment is 100% effective. Protocols
combine treatments.
6,400+ studies for
210+ treatments. c19early.org
|
In vitro study showing that human primary cytotrophoblasts are permissive to SARS-CoV-2 infection, with potential implications for antiviral treatment during pregnancy. Authors tested primary villous cytotrophoblasts isolated from term placentas and found they support complete viral replication cycles for the ancestral SARS-CoV-2 strain, with viral entry occurring predominantly through a non-canonical endosomal pathway. Authors found that chloroquine phosphate, which blocks endosomal acidification, reduced viral production by 96-100% in primary cells, while camostat mesylate (TMPRSS2 inhibitor) had minimal effect, confirming predominant endosomal entry.
39 preclinical studies support the efficacy of HCQ for COVID-19:
1.
Shang et al., Identification of Cathepsin L as the molecular target of hydroxychloroquine with chemical proteomics, Molecular & Cellular Proteomics, doi:10.1016/j.mcpro.2025.101314.
2.
González-Paz et al., Biophysical Analysis of Potential Inhibitors of SARS-CoV-2 Cell Recognition and Their Effect on Viral Dynamics in Different Cell Types: A Computational Prediction from In Vitro Experimental Data, ACS Omega, doi:10.1021/acsomega.3c06968.
3.
Alkafaas et al., A study on the effect of natural products against the transmission of B.1.1.529 Omicron, Virology Journal, doi:10.1186/s12985-023-02160-6.
4.
Guimarães Silva et al., Are Non-Structural Proteins From SARS-CoV-2 the Target of Hydroxychloroquine? An in Silico Study, ACTA MEDICA IRANICA, doi:10.18502/acta.v61i2.12533.
5.
Nguyen et al., The Potential of Ameliorating COVID-19 and Sequelae From Andrographis paniculata via Bioinformatics, Bioinformatics and Biology Insights, doi:10.1177/11779322221149622.
7.
Yadav et al., Repurposing the Combination Drug of Favipiravir, Hydroxychloroquine and Oseltamivir as a Potential Inhibitor Against SARS-CoV-2: A Computational Study, Research Square, doi:10.21203/rs.3.rs-628277/v1.
8.
Hussein et al., Molecular Docking Identification for the efficacy of Some Zinc Complexes with Chloroquine and Hydroxychloroquine against Main Protease of COVID-19, Journal of Molecular Structure, doi:10.1016/j.molstruc.2021.129979.
9.
Baildya et al., Inhibitory capacity of Chloroquine against SARS-COV-2 by effective binding with Angiotensin converting enzyme-2 receptor: An insight from molecular docking and MD-simulation studies, Journal of Molecular Structure, doi:10.1016/j.molstruc.2021.129891.
10.
Noureddine et al., Quantum chemical studies on molecular structure, AIM, ELF, RDG and antiviral activities of hybrid hydroxychloroquine in the treatment of COVID-19: molecular docking and DFT calculations, Journal of King Saud University - Science, doi:10.1016/j.jksus.2020.101334.
11.
Tarek et al., Pharmacokinetic Basis of the Hydroxychloroquine Response in COVID-19: Implications for Therapy and Prevention, European Journal of Drug Metabolism and Pharmacokinetics, doi:10.1007/s13318-020-00640-6.
12.
Rowland Yeo et al., Impact of Disease on Plasma and Lung Exposure of Chloroquine, Hydroxychloroquine and Azithromycin: Application of PBPK Modeling, Clinical Pharmacology & Therapeutics, doi:10.1002/cpt.1955.
13.
Hitti et al., Hydroxychloroquine attenuates double-stranded RNA-stimulated hyper-phosphorylation of tristetraprolin/ZFP36 and AU-rich mRNA stabilization, Immunology, doi:10.1111/imm.13835.
14.
Yan et al., Super-resolution imaging reveals the mechanism of endosomal acidification inhibitors against SARS-CoV-2 infection, ChemBioChem, doi:10.1002/cbic.202400404.
15.
Mohd Abd Razak et al., In Vitro Anti-SARS-CoV-2 Activities of Curcumin and Selected Phenolic Compounds, Natural Product Communications, doi:10.1177/1934578X231188861.
16.
Alsmadi et al., The In Vitro, In Vivo, and PBPK Evaluation of a Novel Lung-Targeted Cardiac-Safe Hydroxychloroquine Inhalation Aerogel, AAPS PharmSciTech, doi:10.1208/s12249-023-02627-3.
17.
Wen et al., Cholinergic α7 nAChR signaling suppresses SARS-CoV-2 infection and inflammation in lung epithelial cells, Journal of Molecular Cell Biology, doi:10.1093/jmcb/mjad048.
18.
Kamga Kapchoup et al., In vitro effect of hydroxychloroquine on pluripotent stem cells and their cardiomyocytes derivatives, Frontiers in Pharmacology, doi:10.3389/fphar.2023.1128382.
19.
Milan Bonotto et al., Cathepsin inhibitors nitroxoline and its derivatives inhibit SARS-CoV-2 infection, Antiviral Research, doi:10.1016/j.antiviral.2023.105655.
20.
Miao et al., SIM imaging resolves endocytosis of SARS-CoV-2 spike RBD in living cells, Cell Chemical Biology, doi:10.1016/j.chembiol.2023.02.001.
21.
Yuan et al., Hydroxychloroquine blocks SARS-CoV-2 entry into the endocytic pathway in mammalian cell culture, Communications Biology, doi:10.1038/s42003-022-03841-8.
22.
Faísca et al., Enhanced In Vitro Antiviral Activity of Hydroxychloroquine Ionic Liquids against SARS-CoV-2, Pharmaceutics, doi:10.3390/pharmaceutics14040877.
23.
Delandre et al., Antiviral Activity of Repurposing Ivermectin against a Panel of 30 Clinical SARS-CoV-2 Strains Belonging to 14 Variants, Pharmaceuticals, doi:10.3390/ph15040445.
24.
Purwati et al., An in vitro study of dual drug combinations of anti-viral agents, antibiotics, and/or hydroxychloroquine against the SARS-CoV-2 virus isolated from hospitalized patients in Surabaya, Indonesia, PLOS One, doi:10.1371/journal.pone.0252302.
25.
Zhang et al., SARS-CoV-2 spike protein dictates syncytium-mediated lymphocyte elimination, Cell Death & Differentiation, doi:10.1038/s41418-021-00782-3.
26.
Dang et al., Structural basis of anti-SARS-CoV-2 activity of hydroxychloroquine: specific binding to NTD/CTD and disruption of LLPS of N protein, bioRxiv, doi:10.1101/2021.03.16.435741.
27.
Shang (B) et al., Inhibitors of endosomal acidification suppress SARS-CoV-2 replication and relieve viral pneumonia in hACE2 transgenic mice, Virology Journal, doi:10.1186/s12985-021-01515-1.
28.
Wang et al., Chloroquine and hydroxychloroquine as ACE2 blockers to inhibit viropexis of 2019-nCoV Spike pseudotyped virus, Phytomedicine, doi:10.1016/j.phymed.2020.153333.
29.
Sheaff, R., A New Model of SARS-CoV-2 Infection Based on (Hydroxy)Chloroquine Activity, bioRxiv, doi:10.1101/2020.08.02.232892.
30.
Ou et al., Hydroxychloroquine-mediated inhibition of SARS-CoV-2 entry is attenuated by TMPRSS2, PLOS Pathogens, doi:10.1371/journal.ppat.1009212.
31.
Andreani et al., In vitro testing of combined hydroxychloroquine and azithromycin on SARS-CoV-2 shows synergistic effect, Microbial Pathogenesis, doi:10.1016/j.micpath.2020.104228.
32.
Clementi et al., Combined Prophylactic and Therapeutic Use Maximizes Hydroxychloroquine Anti-SARS-CoV-2 Effects in vitro, Front. Microbiol., 10 July 2020, doi:10.3389/fmicb.2020.01704.
33.
Liu et al., Hydroxychloroquine, a less toxic derivative of chloroquine, is effective in inhibiting SARS-CoV-2 infection in vitro, Cell Discovery 6, 16 (2020), doi:10.1038/s41421-020-0156-0.
34.
Yao et al., In Vitro Antiviral Activity and Projection of Optimized Dosing Design of Hydroxychloroquine for the Treatment of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), Clin. Infect. Dis., 2020 Mar 9, doi:10.1093/cid/ciaa237.
Pinatel et al., 26 Feb 2026, Canada, peer-reviewed, 9 authors.
Contact: cathy.vaillancourt@inrs.ca, laurent.chatel-chaix@inrs.ca.
In vitro studies are an important part of preclinical research, however results may be very different in vivo.
SARS-CoV-2 infects human primary cytotrophoblasts mainly through a noncanonical entry route
doi:10.1093/molehr/gaag015/8500690
Since the beginning of the COVID-19 pandemic, vulnerable populations such as pregnant persons have been at higher risk of severe symptoms and poor outcomes. Although reports of SARS-CoV-2 vertical transmission remain rare, several studies showed that maternal infection during pregnancy can induce histomorphological and inflammatory alterations in the placenta. However, the permissiveness of human trophoblasts to various variants of the virus remains poorly characterized. In this study, human primary villous cytotrophoblasts isolated from term placentas, along with trophoblastic cell lines BeWo, JEG-3, and HIPEC-65 were infected with the ancestral SARS-CoV-2 strain, which disseminated worldwide in early 2020. Permissiveness was assessed with quantitative RT-PCR, immunostaining of viral protein Nucleocapsid, and plaque assays. To investigate viral entry routes, cells were treated with Camostat mesylate (an inhibitor of the co-entry factor TMPRSS2) or chloroquine phosphate (an endosomal entry inhibitor) and viral fitness was assessed by plaque assays. Primary villous cytotrophoblasts and JEG-3 cells were also tested for infection with three pre-omicron SARS-CoV-2 variants of concern. Our results show that primary villous cytotrophoblasts are permissive to all tested SARS-CoV-2 strains in vitro. Infection with the ancestral SARS-CoV-2 strain relies mainly on a non-canonical endosomal entry pathway. Notably, JEG-3 cells represent an appropriate and convenient model for studying trophoblast infection by SARS-CoV-2, as they exhibit high permissiveness to the ancestral strain, and the SARS-CoV-2 entry pathway is similar to that in villous cytotrophoblasts. Overall, this study reveals that the cytotrophoblastic permissiveness to SARS-CoV-2 depends on the viral genetic nature and provides new insights into its entry route in human trophoblasts.
Authors' roles
Conflict of interest The authors declare no conflict of interests.
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DOI record:
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