BCG Vaccination Modulates Long-Term TNF-α and sCD40L in COVID-19: An Exploratory Longitudinal Study.

Area of Science:

• Immunology
• Infectious Diseases
• Vaccinology

Background:

• Bacillus Calmette-Guérin (BCG) vaccination is known for non-specific immunomodulatory effects via trained immunity.
• This trained immunity may influence inflammatory responses in COVID-19.
• Tumor necrosis factor-alpha (TNF-α) and soluble CD40 ligand (sCD40L) are critical inflammatory and pro-thrombotic mediators in COVID-19 pathogenesis.

Purpose of the Study:

• To investigate the impact of BCG vaccination on inflammatory mediators in mild COVID-19.
• To assess the modulation of TNF-α and sCD40L levels following BCG administration in COVID-19 patients.

Main Methods:

• A randomized, placebo-controlled trial (BATTLE trial) involving young, healthy adults with mild COVID-19.
• Intradermal BCG vaccination or placebo administered during the acute infection phase.
• Plasma TNF-α and sCD40L levels measured at days 7, 45, and 6 months post-intervention.

Main Results:

• BCG recipients showed elevated TNF-α and sCD40L at day 7 compared to placebo.
• Placebo group exhibited a transient decline in TNF-α by day 45.
• BCG group demonstrated sustained reduction in TNF-α and sCD40L from day 45 to 6 months.

Conclusions:

• BCG vaccination induces durable modulation of TNF-α and sCD40L in mild COVID-19, aligning with trained immunity principles.
• This immune modulation may promote faster inflammation resolution and reduce inflammatory complication risks.
• Further large-scale, diverse controlled trials are necessary to validate findings and clinical implications.