Antimicrobial and therapeutic effect of gold Nanoparticle-Aptamer conjugated antimicrobial peptide RW-BP100 in Brucella canis infected mice and RAW 264.7 cells.

Canine brucellosis is a common zoonosis worldwide, but treatment is challenging due to the stealthy and chronic infection caused by the bacterium Brucella (B.) canis. Antimicrobial peptides (AMPs) are promising candidates for combating drug-resistant microbes, and gold nanoparticle aptamer (AuNP-Apt) aids the delivery of peptides to mammalian cells. This study evaluated the therapeutic efficacy of AuNP-AptHis conjugated antimicrobial peptide RW-BP100His (AuNP-AptHis-RW-BP100His) against B. canis in murine macrophage RAW 264.7 cells and BALB/c mice. In vitro, a high concentration of RW-BP100His alone had a bactericidal effect. AuNP-AptHis-RW-BP100His inhibited intracellular bacterial replication and decreased nitric oxide (NO) production in RAW 264.7 cells infected with B. canis. The production of proinflammatory cytokines in RAW 264.7 cells was elevated after AuNP-AptHis-RW-BP100His treatment. In vivo, AuNP-AptHis-RW-BP100His treatment reduced bacterial burden and microgranulomas in the liver and spleen. CD4+, CD8+ T cells, and Th1 cytokines IFN-γ and TNF were elevated in the treated mice. The results indicate that the therapeutic mechanism of AuNP-AptHis-RW-BP100His is immunomodulation of the infected host to upregulate cell-mediated immunity for B. canis clearance. Therefore, it is a promising candidate to treat canine brucellosis as an alternative to conventional antibiotics.