BCG Vaccine-Induced Trained Immunity and COVID-19: Protective or Bystander?
Received 2 January 2021
Accepted for publication 24 February 2021
Published 23 March 2021 Volume 2021:14 Pages 1169—1184
Checked for plagiarism Yes
Review by Single anonymous peer review
Peer reviewer comments 2
Editor who approved publication: Professor Suresh Antony
Gopala Koneru,1 Gaber El-Saber Batiha,2 Abdelazeem M Algammal,3 Mahmoud Mabrok,4,5 Sara Magdy,6 Shrouk Sayed,6 Mai E AbuElmagd,6 Reham Elnemr,6 Mahmoud M Saad,6 Noura H Abd Ellah,7 Amal Hosni,8 Khalid Muhammad,9,* Helal F Hetta10,11,*
1Department of Medicine, Division of Gastroenterology and Hepatology, Rutger New Jersey Medical School, Rutgers University, New Brunswick, NJ, 07103, USA; 2Department of Pharmacology and Therapeutics, Faculty of Veterinary Medicines, Damanhour University, Damanhur, 22511, Egypt; 3Department of Bacteriology, Immunology, and Mycology, Faculty of Veterinary Medicine, Suez Canal University, Ismailia, 41522, Egypt; 4Department of Fish Diseases and Management, Faculty of Veterinary Medicine, Suez Canal University, Ismailia, 41522, Egypt; 5Fish Infectious Diseases Research Unit (FID RU), Department of Veterinary Microbiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, 10330, Thailand; 6Faculty of Medicine, Assiut University, Assiut, 71515, Egypt; 7Department of Pharmaceutics, Faculty of Pharmacy, Assiut University, Assiut, 71526, Egypt; 8Department of Clinical Pathology, Faculty of Medicine, Assiut University, Assiut, Egypt; 9Department of Biology, College of Science, United Arab Emirates University, Al Ain, United Arab Emirates; 10Department of Medical Microbiology and Immunology, Faculty of Medicine, Assiut University, Assiut, Egypt; 11Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA
*These authors contributed equally to this work
Correspondence: Khalid Muhammad; Helal F Hetta Email [email protected]; [email protected]
Abstract: In late 2019, a new virulent coronavirus (CoV) emerged in Wuhan, China and was named as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). This virus spread rapidly, causing the coronavirus disease-2019 (COVID-19) pandemic. Bacillus Calmette–Guérin (BCG) is a live attenuated tuberculosis (TB) vaccine, associated with induction of non-specific cross-protection against unrelated infections. This protection is a memory-like response in innate immune cells (trained immunity), which is caused by epigenetic reprogramming via histone modification in the regulatory elements of specific genes in monocytes. COVID-19 related epidemiological studies showed an inverse relationship between national BCG vaccination policies and COVID-19 incidence and death, suggesting that BCG may induce trained immunity that could confer some protection against SARS-CoV-2. As this pandemic has put most of Earth’s population under quarantine, repurposing of the old, well-characterized BCG may ensure some protection against COVID-19. This review focuses on BCG-related cross-protection and acquisition of trained immunity, as well as the correlation between BCG vaccination and COVID-19 incidence and mortality.
Keywords: COVID-19, BCG vaccine, coronavirus, trained immunity, tuberculosis
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