Basic Immunology
Preparation and immune-enhancing effects of monophosphoryl lipid A pH-sensitive liposome
Cui Wenyu, Quan Wenjing, Li Jilai, Hou Yibo, Xu Jing, Zhang Yuntao
Published 2022-09-30
Cite as Chin J Microbiol Immunol, 2022, 42(9): 699-704. DOI: 10.3760/cma.j.cn112309-20220302-00066
Abstract
ObjectiveTo prepare pH-sensitive liposomes to avoid the degradation of monophosphoryl lipid A (MPLA) by lysosomes.
MethodsUsing DOPE and CHEMS as carrier materials, pH-sensitive liposomes were prepared by thin-film dispersion method. Particle sizes and Zeta potential of the liposomes were detected by dynamic light scattering. The morphological features of pH-sensitive liposomes under different pH conditions were observed by transmission electron microscopy. Flow cytometry was performed to detect the phagocytosis of liposomes by THP-1 and DC2.4 cells. Confocal laser microscopy was used to observed the colocalization of liposomes and lysosomes. BALB/c mice were immunized with hepatitis B surface antigen (HBsAg) using MPLA pH-sensitive liposome as an adjuvant. The levels of serum anti-HBs were quantitatively detected by ELISA. IFN-γ and IL-2 spot forming cells (SFCs) in mouse splenic lymphocytes were detected by ELISPOT.
ResultsThe pH-sensitive liposomes were constructed with an average particle size of (90.90±1.13) nm, polydispersity index (PDI) of 0.076±0.013 and Zeta potential of (-27.900±0.666) mV. As the pH value of the solution decreased, the particle size increased significantly and the liposomes presented irregular shapes, indicating the pH-sensitive features. The phagocytosis rates by THP-1 cells and DC2.4 cells were 10.40% and 12.40% for pH-sensitive fluorescent liposomes, and 1.09% and 0.28% for fluorescent liposomes. Confocal laser microscopy revealed that pH-sensitive fluorescent liposomes were phagocytosed by THP-1 cells and existed in the cytoplasm, while fluorescent liposomes existed in lysosomes. Compared with MPLA liposomes, MPLA pH-sensitive liposomes could significantly improve the cellular immune response in mice. The levels of IFN-γ and IL-2 SFCs in the MPLA pH-sensitive liposome group were significantly higher than those in the MPLA liposome group (P<0.01) and the non-adjuvant group (P<0.001).
ConclusionsThe pH-sensitive liposome delivery system could improve the utilization of MPLA as an adjuvant.
Key words:
pH-sensitive liposome; Monophosphoryl lipid A; Adjuvant
Contributor Information
Cui Wenyu
The Third Laboratory, National Vaccine and Serum Institute, Beijing 101111, China
Quan Wenjing
Center for Clinical Medicine, China National Biotec Group Co., Ltd., Beijing 100024, China
Li Jilai
The Third Laboratory, National Vaccine and Serum Institute, Beijing 101111, China
Hou Yibo
The Third Laboratory, National Vaccine and Serum Institute, Beijing 101111, China
Xu Jing
The Third Laboratory, National Vaccine and Serum Institute, Beijing 101111, China
Zhang Yuntao
Center for Clinical Medicine, China National Biotec Group Co., Ltd., Beijing 100024, China
