Paraprobiotic derived from Bacillus velezensis GV1 improves immune response and gut microbiota composition in cyclophosphamide-treated immunosuppressed mice

Abstract

Paraprobiotics that benefit human health have the capacity to modulate innate and adaptive immune systems. In this study, we prepared the paraprobiotic from <i>Bacillus velezensis</i> GV1 using the heat-killing method and investigated its effects on immunity and gut microbiota <i>in vitro</i> and <i>in vivo</i>. The morphology of inactivated strain GV1 was observed using scanning electron microscopy. Treatment with GV1 promoted nitric oxide production and augmented cytokine (IL-6, IL-1β, and TNF-α) expression and secretion in RAW 264.7 macrophages. Moreover, the strain GV1 could alleviate cyclophosphamide monohydrate (CTX)-induced immunosuppression by reversing spleen damage and restoring the immune organ index, as well as by increasing the expression of immune-related cytokines (TNF-α, IL-1β, IFN-γ, and IL-2) in the spleen and thymus, respectively. Furthermore, GV1 treatment dramatically healed the CTX-damaged colon and regulated gut microbiota by increasing the relative abundance of beneficial bacterial families (<i>Lactobacillaceae</i>, <i>Akkermansiaceae</i>, and <i>Coriobacteriaceae</i>) and decreasing that of harmful bacterial families (<i>Desulfovibrionaceae</i>, <i>Erysipelotrichaceae</i>, and <i>Staphylococcaceae</i>). Thus, the heat-killed GV1 can be considered a potential immunoregulatory agent for use as a functional food or immune-enhancing medicine.