BCG tuberculosis vaccine could curb COVID-19 infection

A recent study available on the pre-test server of bioRxiv revealed that vaccination with Bacillus Calmette-Guérin (commonly known as BCG) can limit infection with the SARS-CoV-2 coronavirus and could be used as a platform to establish early immunological actions that affect the outcome of coronavirus disease (COVID-19).

The clinical presentation and pathological actions seen in severe manifestations of COVID-19 are likely driven by a very strong and continuous natural immune response.. The severity of the disease correlates positively with the levels of inflammatory proteins called cytokines, but also with the activation of myeloid cells.

BCG is a live attenuated vaccine that has long been widely used for the prevention of tuberculosis in children and young children.. Its non-specific effects linked to epigenetic and metabolic reprogramming of the natural immune system are also recognized.

This is the reason why The administration of BCG was reviewed by the working group led by Kerry L. Hilligan, specialist in immunobiology of the Parasitic Diseases Laboratory belonging to the U.S. National Institute of Allergy and Infectious Diseases National Institutes of Health, as a potential prophylactic alternative in the prevention of SARS-CoV-2 infection.

On the other hand, Recent preclinical studies have shown that BCG can be used as an adjuvant to enhance vaccine-induced specific protection against SARS-CoV-2. This study systematically evaluated the effects of the previous BCG inoculation on the pathogenesis of SARS-CoV-2 in two experimental mouse models.

The former used mice that were very susceptible to the fatal infection because they expressed a transgene for the human ACE2 receptor. These mice also carry a certain viral predilection in their brains which can contribute to mortality.. The second model involved a challenge with a variant of SARS-CoV-2 alpha (B.1.1.7) that can infect non-transgenic animals.

After infection, the mice were followed by a researcher who did not know what type of viral inoculation each animal had had and whether they had indeed been infected. The blind analyst recorded daily weight changes and possible clinical signs of the disease.

An old known vaccine

Conclusion, Researchers have shown that intravenous administration of BCG can offer a truly high level of protection against SARS-CoV-2 in both models.. Specifically, the animals were protected against the lethal challenge, while BCG also reduced the viral loads of the alpha variant in the lungs of the mice of the second group.

“Additionally,” adds Hilligan, the lead author of the still pending review document, “the previous inoculation with intravenous BCG significantly reduced virus-associated lung pathology, inflammatory cell recruitment, as well as cell production. chemokines, which play a valuable role in the immune response. The distribution of the antigen was also limited in these mice ”.

Ultimately, the increased cytokine reactions caused by SARS-CoV-2, known as the storm, were also reduced, detecting a decrease in the inflammatory record. “Although intravenous administration of BCG is not currently acceptable clinical practice, the experimental concept that previous applications of BCG can trigger potent protection against death from COVID, which may aid in the design of other strategies for COVID19 prophylaxis. virus reactionexplains Hilligan.

This new breakthrough supports the idea of ​​several laboratories exploring the possibility that the BCG vaccine can be used alone or in synergy to reduce the severity of COVID-19 disease. Currently, there are about twenty randomized controlled clinical trials in the Netherlands, Australia, Germany, Greece, United States, Egypt, Colombia, Mexico, Brazil, South Africa, Denmark and in France, which continue to assess whether the BCG vaccine is in decline. the incidence and severity of COVID-19.

The importance of establishing age groups that could be protected against SARS-CoV2 infection through BCG vaccination, as well as the timing of vaccination prior to potential exposure to the virus, is evident, as this can determine whether the BCG vaccine It is effective. This represents a critical step in assessing the potential of BCG vaccination to protect the elderly against SARS-CoV-2 and other respiratory infectious agents..

However, more documentation is needed to specifically demonstrate the effects of BCG vaccination on COVID-19 morbidity and mortality in different settings.

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