In Vitro Cellular Activity Evaluation of the Nanoemulsion Vaccine Adjuvant Ophiopogonin D

Summary

The protocol presents detailed methods for evaluating whether the nanoemulsion ophiopogonin D adjuvant promotes effective cellular immune responses.

Abstract

As a principal ingredient of vaccines, adjuvants can directly induce or enhance the powerful, widespread, innate, and adaptive immune responses associated with antigens. Ophiopogonin D (OP-D), a purified component extracted from the plant Ophiopogon japonicus, has been found to be useful as a vaccine adjuvant. The problems of the low solubility and toxicity of OP-D can be effectively overcome by using a low-energy emulsification method to prepare nanoemulsion ophiopogonin D (NOD). In this article, a series of in vitro protocols for cellular activity evaluation are examined. The cytotoxic effects of L929 were determined using a cell counting kit-8 assay. Then, the secreted cytokine levels and corresponding immune cell numbers after the stimulation and culture of splenocytes from immunized mice were detected by ELISA and ELISpot methods. In addition, the antigen uptake ability in bone marrow-derived dendritic cells (BMDCs), which were isolated from C57BL/6 mice and matured after incubation with GM-CSF plus IL-4, was observed by laser scanning confocal microscopy (CLSM). Importantly, macrophage activation was confirmed by measuring the levels of IL-1β, IL-6, and tumor necrosis factor alpha (TNF-α) cytokines by ELISA kits after coculturing peritoneal macrophages (PMs) from blank mice with the adjuvant for 24 h. It is hoped that this protocol will provide other researchers with direct and effective experimental approaches to evaluate the cellular response efficacies of novel vaccine adjuvants.

Introduction

Vaccines are an important means of preventing and treating infectious and noncommunicable diseases. The appropriate addition of adjuvants and delivery vehicles to vaccine formulations is beneficial for enhancing the immunogenicity of antigens and generating long-lasting immune responses¹. In addition to the classical adjuvant alum (aluminum salt), there are six kinds of adjuvants for vaccines that are currently marketed: MF59^2,3, AS04³, AS03³, AS01³, CpG1018⁴, and Matrix-M^5<....

Protocol

All cell experiments were performed in a cell engineering laboratory equipped with basic operating rooms, buffer rooms, sterile culture rooms, and identification and analysis rooms. The working environment and conditions were free from microbial contamination and other harmful factors. The animal experiments were conducted based on the Guidelines for the Care and Use of Laboratory Animals and were approved by the Laboratory Animal Welfare and Ethics Committee of the Third Military Medical University.

1. Autoclaving and material preparation

1. Prepare the reagents and consumables, such as phosphate-buffered saline (....

Results

The cellular activity evaluation of the adjuvants OP-D and NOD was completed in vitro according to the protocol. L929 fibroblasts are a useful screening model for the in vitro toxicity testing of NOD (Figure 1). The quantification of inflammatory cytokine levels in the spleen can help researchers better understand the immune response (Figure 2). Monitoring CTLs with ELISpot is the gold standard for assessing antigen-specific T-cell immunity in .......

Discussion

Subunit vaccines provide excellent safety but poor immunogenicity. The main strategy to enhance the immunogenicity is to physically adsorb or couple antigens with adjuvants and incorporate them into the drug delivery systems to promote the uptake and presentation by DCs. Natural plant saponins such as quillaia saponin and its derivatives are highly toxic and are not suitable for the development of human vaccines¹⁷. Therefore, the study of the toxic effects of vaccines or adjuvants on cells is a ne.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
0.25% Trypsin-EDTA (1x)	GIBCO, USA	25200056
96-well filter plates	Millipore. Billerica, MA	CLS3922
AlPO4	General Chemical Company, USA	null
Automated Cell Counter	Countstar, China	IC1000
BALB/c mice and C57BL/6 mice	Beijing HFK Bioscience Co. Ltd	null
caprylic/capric triglyceride (GTCC)	Beijing Fengli Pharmaceutical Co. Ltd., Beijing, China	null
CCK-8 kits	Dojindo, Japan	CK04
Cell Counting Plate	Costar, Corning, USA	CO010101
Cell Sieve	biosharp, China	BS-70-CS
Centrifuge 5810 R	Eppendorf, Germany	5811000398
DAPI	Sigma-Aldrich, St. Louis, USA	D9542
DMEM basic(1x) medium	GIBCO, USA	C11885500BT
DSZ5000X Inverted Microscope	Nikon,Japan	DSZ5000X
EL-35 (Cremophor-35)	Mumbai, India	null
ELISpot classic	AID, Germany	ELR06
Fetal Bovine Serum	GIBCO, USA	10099141C
Full-function Microplate Reader	Thermo Fisher Scientific, USA	VL0000D2
GFP	Sigma-Aldrich, St. Louis, USA	P42212
Glutamax	Invitrogen, USA	35050061
Granulocyte Macrophage Colony-Stimulating Factor	GM-CSF, R&D Systems, USA	315-03
HEPES	Invitrogen, USA	15630106
HF 90/240 Incubator	Heal Force, Switzerland	null
IL-4	PeproTech, USA	042149
L929 cell line	FENGHUISHENGWU, China	NCTC clone 929 (RRID:CVCL_0462)
Laser Scanning Confocal Microscopy	Zeiss, Germany	LSM 980
MONTANE 85 PPI	SEPPIC, France	L12910
MONTANOX 80 PPI	SEPPIC, France	36372K
Mouse IFN-γ ELISA kit	Dakewe, China	1210002
Mouse IFN-γ precoated ELISPOT kit	Dakewe, China	DKW22-2000-096
Mouse IL-17A ELISA kit	Dakewe, China	1211702
Mouse IL-17A ELISpotPLUS Kit	ebiosciences, USA	3521-4HPW-2
Mouse IL-1β ELISA kit	Dakewe, China	1210122
Mouse IL-6 ELISA kit	Dakewe, China	1210602
Mouse TNF-α ELISA kit	Dakewe, China	1217202
Non-essential amino acids(100x)	Invitrogen, USA	11140050
Ophiopogonin-D	Chengdu Purui Technology Co. Ltd	945619-74-9
Penicillin-Streptomycin Solution	Invitrogen, USA	15070063
Phalloidin	Solarbio, China	CA1620
Phosphate Buffered Saline	ZSGB-BIO, China	ZLI-9062
Red Blood Cell Lysis Buffer	Solarbio, China	R1010
RPMI 1640 medium	Hyclone (Life Technology), USA	SH30809.01
Sodium pyruvate(100 mM)	Invitrogen, USA	11360070
Squalene	Sigma, USA	S3626
β- Mercaptoethanol	Invitrogen, USA	21985023