Original Article
Poly(lactic acid)–poly(ethylene glycol) nanoparticles provide sustained delivery of a Chlamydia trachomatis recombinant MOMP peptide and potentiate systemic adaptive immune responses in mice

https://doi.org/10.1016/j.nano.2014.02.009Get rights and content

Abstract

PLA–PEG [poly(lactic acid)–poly (ethylene glycol)], a biodegradable copolymer, is underexploited for vaccine delivery although it exhibits enhanced biocompatibility and slow release immune-potentiating properties. We document here successful encapsulation of M278, a Chlamydia trachomatis MOMP (major outer-membrane protein) peptide, within PLA–PEG nanoparticles by size (~ 73-100 nm), zeta potential (− 16 mV), smooth morphology, encapsulation efficiency (~ 60%), slow release pattern, and non-toxicity to macrophages. Immunization of mice with encapsulated M278 elicited higher M278-specific T-cell cytokines [Th1 (IFN-γ, IL-2), Th17 (IL-17)] and antibodies [Th1 (IgG2a), Th2 (IgG1, IgG2b)] compared to bare M278. Encapsulated-M278 mouse serum inhibited Chlamydia infectivity of macrophages, with a concomitant transcriptional down-regulation of MOMP, its cognate TLR2 and CD80 co-stimulatory molecule. Collectively, encapsulated M278 potentiated crucial adaptive immune responses, which are required by a vaccine candidate for protective immunity against Chlamydia. Our data highlight PLA–PEG's potential for vaccines, which resides in its slow release and potentiating effects to bolster immune responses.

From the Clinical Editor

This study highlights the potential of a PLA-PEG-based nanoparticle formulation containing a major outer membrane protein of chlamydia trachomatis in inducing a sustained enhanced immune response, paving the way to the development of a vaccination strategy against this infection.

Graphical Abstract

Nanoencapsulation of M278, a Chlamydia trachomatis recombinant MOMP (major outer-membrane protein) peptide within PLA–PEG copolymer (PLA–PEG–M278) provided its slow release that potentiated immune responses in BALB/c mice by sustained antigen presentation. Compared to bare M278, enhanced adaptive immune responses were triggered by encapsulated M278 in mice including specific T-cell cytokines and isotype antibodies, along with in vitro serum-mediated inhibition of Chlamydia infectivity of macrophages.

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Section snippets

Fabrication of nanoparticles

Recombinant MOMP-278 (M278) was cloned as previously reported15 and encapsulated in PLA–PEG nanoparticles using a modified water/oil/water double emulsion evaporation technique16, 17 and then lyophilized in the presence of 5% trehalose (as a stabilizer) to obtain encapsulated M278 (PLA–PEG–M278). Phosphate-buffered saline (PBS) was similarly encapsulated in PLA–PEG to serve as a negative control (PLA–PEG–PBS). All lyophilized nanoparticles were stored at − 80 °C in a sealed container until used.

Scanning electron microscopy (SEM) and transmission electron microscopy (TEM)

Physiochemical properties of nanoparticles

SEM and TEM microscopy techniques were employed to assess the morphology and size of nanoparticles. By SEM analysis, PLA–PEG–PBS appeared to be coagulated particles and in the conformation of what is referred to as PEGylated “brush” with rough outer surface23 (Figure 2, A). Magnification of this brush structure within PLA–PEG–M278 revealed a Web-like matrix that contained grape-like structures dispersed throughout (Figure 2, B). Additionally, TEM images of PLA–PEG–PBS (Figure 2, C) and

Discussion

Problems associated with conventional adjuvants for vaccines are protein denaturation and low bioavailability in vivo.25 PLA–PEG offers an attractive alternative to conventional adjuvants as a vaccine-delivery system because it can augment the immunogenicity of proteins by providing their controlled slow release to the immune system.1, 2, 26 Moreover, PLA–PEG can enhance the protein loading capacity, reduce its burst effect, prevent degradation, and increase the circulation time and

Acknowledgments

Special thanks go to Yvonne Williams, Lashaundria Lucas, Juwana Smith Henderson and Maiya Moore for their excellent administrative assistance; Eva Dennis for the graphical abstract, and Michael Miller, Auburn University, for assistance with SEM and TEM imaging.

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    All authors declare no conflict of interest related to the submitted manuscript.

    Financial support: This research was supported by National Science Foundation-CREST (HRD-1241701), NSF-HBCU-UP (HRD-1135863) and National Institutes of Health-MBRS-RISE (1R25GM106995-01) grants.

    An abstract of this manuscript was presented at the TechConnect World Conference, May 11-16, 2013, Washington, DC, and at the 113th American Society for Microbiology General Meeting, May 18-21, 2013, Denver, CO.

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