Preparation of a nanovaccine against Brucella melitensis M16 based on PLGA nanoparticles and oligopolysaccharide antigen

Figures & data

Figure 1. The conjugation mechanism of PLGA NPs with OPS antigen.

Figure 2. (a) Zeta potential of PLGA nanoparticle and PLGA-OPS conjugate. (b) Size distribution PLGA nanoparticles and OPS–PLGA conjugate.

Figure 3. FTIR spectra of (a) PLGA nanoparticles and (b) OPS–PLGA conjugate. The increase in OH group in the PLGA nanoparticles was shown with a red oval.

Figure 4. Atomic force microscope images of (a) PLGA nanoparticles surface, (b) three-dimensional image of PLGA nanoparticles, (c) OPS–PLGA conjugate surface and (d) three-dimensional image of OPS–PLGA conjugate.

Figure 5. Distribution and kinetics of antibody titres. The IgA (a), IgM (b), IgG (c), IgG1 (d), IgG2a (e), IgG2b (f), IgG3 (g) show the results of serum antibody production against B. melitensis. The values are the average of three replicates (±SD). Different letters represent the meaningful of differences in level p < .001.

Figure 6. The percentage of bacteria killed in each serum dilution.

Table 1. Opsonophagocytosis activity of test groups.

Group (n = 5)	Antigen injection^a	Opsonophagocytic activity mean unit numbers (CFU/Well)^b	Percentage of inhibition of OPK activity (%)^c
1	OPS–PLGA	126 ± 14	71
2	OPS	239 ± 19	45
3	PLGA	380 ± 37
4	PBS	436 ± 48

^aInjectable antigens in each group. ^bAverage bacterial count in each group in dilution 1:32 ± 1. ^cPercentage of inhibitory of the opsonophagocytic activity of the antigen receptor groups compared to the control group.

Table 2. Level of protection against B. melitensis infection induced by OPS–PLGA conjugate and OPS immunization.

Group (n = 5)	Antigen injection	Log10 units of Brucella in spleen	Unit of protection
		4 weeks
1	OPS–PLGA	4.46 ± 0.09	2.1
2	OPS	5.13 ± 0.08	1.43
3	PLGA	6.32 ± 0.14
4	PBS	6.56 ± 0.12