Abstract
Recombinant human myelin basic protein (rhMBP) was previously produced in the milk of transgenic cows. Differences in molecular recognition of either hMBP or rhMBP by surface-immobilized anti-hMBP antibodies were demonstrated. This indicated differences in immunological response between rhMBP and hMBP. Here, the activity of free and controlled release rhMBP poly(ε-caprolactone) nanoparticles (NPs), as a therapeutic vaccine against multiple sclerosis (MS) was demonstrated in experimental autoimmune encephalomyelitis (EAE) animal model. Following optimization of nanoformulation, discrete spherical, rough-surfaced rhMBP NPs with high entrapment efficiency and controlled release pattern were obtained. Results indicated that rhMBP was loaded into and electrostatically adsorbed onto the surface of NPs. Subcutaneous administration of free or rhMBP NPs before EAE-induction reduced the average behavioral score in EAE mice and showed only mild histological alterations and preservation of myelin sheath, with rhMBP NPs showing increased protection. Moreover, analysis of inflammatory cytokines (IFN-γ and IL-10) in mice brains revealed that pretreatment with free or rhMBP NPs significantly protected against induced inflammation. In conclusion: i) rhMBP ameliorated EAE symptoms in EAE animal model, ii) nanoformulation significantly enhanced efficacy of rhMBP as a therapeutic vaccine and iii) clinical investigations are required to demonstrate the activity of rhMBP NPs as a therapeutic vaccine for MS.
Highlights
Results showed that all NPs were in the nanorange (Table 2) where the size of NPs enclosing human serum albumin (HSA) ranged from 208 ± 12 (F8) to 596 ± 25 nm (F6) with polydispersity index (PDI) ranging from 0.147 (F2) to 0.315 (F7)
In case of rhMBP, the EE% was surprisingly high, 99.9 ± 1.7% compared to only 32.5 ± 1.0% in case of HSA (F8) as shown in (Table 2)
Such significant difference could be attributed to: i) the smaller molecular weight (MW) of rhMBP when compared to HSA, ii) random coil structure of rhMBP when compared to the folded structure of HSA that resulted in exposure of the hydrophobic regions of rhMBP to the medium, more interaction with the hydrophobic PCL polymer and iii) the abundance of basic amino acid residues in rhMBP sequence that could lead to electrostatic attraction between the positively charged basic amino acids and the negatively charged PCL NPs
Summary
We aimed to i) control the release of rhMBP in a sustained pattern; according to the polymer biodegradation kinetics, ii) enhance the stability of the rhMBP; previously shown to be susceptible to degradation by various experimental conditions and iii) most importantly, deliver rhMBP across the BBB via encapsulation into the hydrophobic PCL NPs
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