Tuberculosis & COVID-19 Pandemic

Tuberculosis & COVID-19 Pandemic

Corona-viruses are a large family of viruses that usually cause mild to moderate upper-respiratory tract illnesses, like the common cold, in people. There are hundreds of corona-viruses, most of which circulate among animals including pigs, camels, bats, and cats. Sometimes those viruses jump to humans—called a spillover event—and can cause disease. After a Pandemic outbreak from china, The disease is now called COVID-19. 

The virus has caused a widespread outbreak of disease similar to SARS throughout China, with exported cases occurring in 183 other countries, including India. 

Ultrastructure of  COVID-19

But, you need not suffer from this evil COVID-19, else we can say, you will not get affected with COVID-19 at all if you had vaccinated with Bacillus Calmette-Guerin (BCG) (Vaccine for Tuberculosis)

Yes! Sam Behar, and his colleague at the Department of Microbiology, University of Massachusetts Medical School, US. Recently published a peer-reviewed paper and show that “ BCG stimulates general immune response” called Trained Immunity. This results in faster response to infections that could reduce the severity of disease and lead to faster recovery.

BCG —(Bacillus Calmette-Guerin) developed in 1921 in France Epidemiological data, however, showed it could be effective against the novel coronavirus (SARS-CoV2). This vaccine is composed of a live, weakened strain of the bacterium Mycobacterium Bovis, related to tuberculosis (TB) pathogen Mycobacterium tuberculosis.

Trained Immunity

How Vaccines Works ...

when you are attacked by a microbe, the innate immune system started doing his duty.

Monocytes - types of white blood cells — penetrate the infected tissue, convert to macrophages and provide the first line of defense.

But Vaccines, on the other hand, lead to the development of the acquired immune system in the human body. This works slowly and focuses specifically on certain invaders.

BCG vaccination has been shown to produce positive “heterologous” or non-specific immune effects leading to improved response against other non-mycobacterial pathogens. For instance, BCG vaccinated mice infected with the virus were protected by increased IFN-Y production from CD4+ cell. 

This phenomenon is called Trained immunity and is proposed to be caused by metabolic and epigenetic changes leading to the promotion of genetic regions encoding for pro-inflammatory cytokines.

Multiplication of COVID-19 in alveoli cells. 

BCG vaccination significantly increases the secretion of pro-inflammatory cytokines, specifically, IL-1B, which has been shown to play a vital role in antiviral immunity. 

The correlation between the beginning of universal BCG vaccination and the protection against COVID-19 suggests that

BCG might confer long-lasting protection against the current strain of coronavirus. 

However, randomized controlled trials using BCG are required to determine how fast an immune response develops that protects against COVID-19. BCG is generally innocuous with the main side effect of the development of inflammation at the site of injection so care should be taken when applying these possible interventions for COVID-19.

I'm trying to understand the molecular mechanism behind this, and, once I'm clear with it, I'll share it with you.

Understood this relation? Got any doubt? anything wrong in my explanation? Kindly comment and I would try to reply or correct as soon as possible.

Disclaimer: I wrote this article based on my understanding after reading a paper. There may be mistakes. If you find any, kindly let me know with your valuable comments.

References :

• Kristensen, I., Aaby, P. & Jensen, H. Routine vaccinations and child survival: Follow up study in Guinea-Bissau, West Africa. Br. Med. J. 321, 1435–1439 (2000).
• Zwerling, A. et al. The BCG world atlas: A database of global BCG vaccination policies and practices. PLoS Med. 8, (2011).
• Zhou, F. et al. Articles Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China : a retrospective cohort study. Lancet 6736, 1–9 (2020).
• Japan was expecting a coronavirus explosion. Where is it? | The Japan Times. Available at: https://www.japantimes.co.jp/news/2020/03/20/national/coronavirus-explosion expected-japan/#.XnllWahKjIU. (Accessed: 23rd March 2020)
• Development and expectation of the tuberculosis service system in China. Available at: http://www.zgflzz.cn/EN/Y2012/V34/I9/557. (Accessed: 24th March 2020)
• Komine-Aizawa, S. et al. Influence of advanced age on Mycobacterium Bovis BCG vaccination in guinea pigs iatrogenically infected with Mycobacterium tuberculosis. Clin. Vaccine Immunol. 17, 1500–1506 (2010).
• Moorlag, S. J. C. F. M., Arts, R. J. W., van Crevel, R. & Netea, M. G. Non-specific effects of BCG vaccine on viral infections. Clinical Microbiology and Infection 25, 1473–1478 (2019).
• Horwitz, M. A., Harth, G., Dillon, B. J. & Masleša-Galić, S. Commonly administered BCG strains including an evolutionarily early strain and evolutionarily late strains of disparate genealogy induce comparable protective immunity against tuberculosis. Vaccine 27, 441– 445 (2009).
• Fact Sheets | Infection Control & Prevention | Fact Sheet - BCG Vaccine | TB | CDC. Available at: https://www.cdc.gov/tb/publications/factsheets/prevention/bcg.htm. (Accessed: 23rd March 2020)