Oral Supplementation with AHCC®, a Standardized Extract of Cultured Lentinula edodes Mycelia, Enhances Host Resistance against SARS-CoV-2 Infection

The coronavirus disease 2019 (COVID-19) pandemic has significantly impacted global public health safety and the economy. Multiple antiviral drugs have been developed, and some have received regulatory approval and/or authorization. The use of nutraceuticals can be beneficial for preventing and treating COVID-19 complications. AHCC is a standardized, cultured extract of an edible mushroom Lentinula edodes of the Basidiomycete family of fungi that is enriched in acylated α-1,4-glucans. Here, we evaluated the effects of the oral administration of AHCC on the host response to SARS-CoV-2 infection in two murine models, K18-hACE2 transgenic mice and immunocompetent BALB/c mice. Oral administration of AHCC every other day for one week before and one day post SARS-CoV-2 infection in both strains of mice decreased the viral load and attenuated inflammation in the lungs. AHCC treatment also significantly reduced SARS-CoV-2-induced lethality in the K18-hACE2 mice. AHCC administration enhanced the expansion of γδ T cells in the spleen and lungs before and after viral infection and promoted T helper 1-prone mucosal and systemic T cell responses in both models. In AHCC-fed BALB/c mice, SARS-CoV-2 specific IgG responses were also enhanced. In summary, AHCC supplementation enhances host resistance against mild and severe COVID-19 infection primarily via the promotion of innate and adaptive T cell immune responses in mice.