CpG ODN Combined with Gold Nanorods Enhances Immune Activation and Its Potential Mechanism

Background Immune escape of tumor cells is a common problem with tumor photothermal therapy utilizing gold nanorods (Au NRs). Whether CpG ODN, an immune adjuvant, can synergize with Au NRs to activate the immune response and its potential mechanism is not clear.Methods The effect of Au NRs combined with CpG ODN (Au NRs-C) on the activity of various immune-related cells, such as double-positive T cells, macrophages, NK cells, Th17, and Treg. The expression levels of various immune and inflammation-related factors, such as IL-1R1, IL-6, IL-17, and TNF-α were characterized. Transcriptome sequencing analysis was used to explore the potential immunomodulatory mechanisms of Au NRs-C. Whether immune activation was enhanced by antibody-functionalized Au NR upon binding to CpG ODN was assessed.Results Flow cytometry and ELISA analyses indicate that both Au NRs and CpG ODN increase pro-inflammatory cytokine levels and immune activation. However, Au NRs-C demonstrated superior immune activation potential. Furthermore, Au NRs stimulate the expression of Treg, while Au NRs-C significantly inhibit this effect. This suggests that the conjugation of CpG ODN with Au NRs not only greatly enhances the immune activation but also compensates for some of their deficiencies in eliciting immune responses. Transcriptome sequencing uncovered DEGs mainly localized to immune and pro-inflammatory cytokine pathways. PPI analysis identified six hub genes: FOXM1, HMOX1, UBE2C, E2F1, PECAM1, and FCGR3A. Moreover, CpG conjugation with antibody functionalization- Au NRs enhances immune stimulation.Conclusion Au NRs-C promotes immune activation by eliciting changes in the activity of immune-associated cells and expression of inflammatory factors through multiple pathways, such as MHC antigen presentation and Toll-like receptor-mediated immune processes.