Aureobasidium pullulans is a species of black yeast known for its production of various biopolymers and bioactive compounds. In recent years, certain strains of A. pullulans (notably N-163 and AFO-202) have been studied for their ability to produce beta-glucans, which are polysaccharides recognized for their immunomodulatory properties. There is emerging scientific evidence suggesting that these beta-glucans may help support the immune system and potentially enhance antiviral defenses.

Some preclinical studies and a few small-scale human trials have explored the effects of A. pullulans-derived beta-glucans on immune function. These studies indicate that such beta-glucans can stimulate components of the innate immune system, such as macrophages and natural killer (NK) cells, which play roles in the body's response to viral infections. Additionally, a handful of pilot studies (primarily from Japan and India) have suggested possible benefits in reducing the severity or duration of viral infections like influenza and even in adjunctive support during COVID-19. However, these studies are limited by small sample sizes, lack of rigorous controls, and often focus on immune markers rather than direct antiviral outcomes.

There is not a robust tradition of using A. pullulans for viral infections, and the scientific evidence, while promising, is still preliminary and does not yet meet the standards of large randomized controlled trials. Thus, its use is best described as having early scientific support but with limited clinical validation at this time.