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Published on: April 29, 2015
Encapsulation of the immune potentiators MPL and RC529 in PLG microparticles enhances their potency
Jina Kazzaz1, Manmohan Singh, Mildred Ugozzoli
1Chiron Vaccines Research, Chiron Corporation, Emeryville, CA 94608, USA. jina_kazzaz@chiron.com <jina_kazzaz@chiron.com>
Purpose:
Monophosphoryl lipid A (MPL) and the synthetic LPS mimetic RC529, encapsulated in poly(lactide-co-glycolide) (PLG) microparticles, were evaluated as immune potentiators in the presence of either HIV-1 gp120 protein or antigen from Neisseria meningitidis serotype B (Men B). The immunogenicity of these formulations was evaluated in mice and compared to CpG containing oligonucleotide. This work was done as part of an ongoing effort to enhance the potency of vaccine candidates against HIV and Men B.
Methods:
Microparticles were made by a solvent evaporation method. Blank microparticles as well as microparticles with encapsulated MPL or RC529 were made using the PLG polymer RG503 and the ionic surfactant Dioctylsulfosuccinate by the water-in-oil-in-water emulsion technique. Antigens from HIV-1 and Men B were adsorbed on the surface of these anionic microparticles and the final formulations characterized for protein loading, release, and integrity. The formulations were then tested in mice for their ability to elicit antibodies and bactericidal activity in comparison with CpG containing oligonucleotide.
Results:
We have found that adding soluble immune potentiators to Men B antigen formulated on PLG microparticles significantly enhanced the immune response to a level comparable to that obtained using CpG. In a separate study, we found that encapsulating MPL or RC529 in PLG microparticles further enhanced the response in comparison to soluble CpG, which is our control group. Similarly, adding soluble immune potentiators to gp120 antigen formulated on PLG microparticles resulted in a significant enhancement of the immune response. Moreover, delivering MPL or RC529 encapsulated in PLG microparticles with gp120 adsorbed on PLG microparticles, resulted in even further enhancement of serum titers over those obtained with soluble immune potentiators. These titers were comparable to or greater than those obtained with soluble CpG, the control group. This effect was observed for both antigens regardless of whether or not the immune potentiator and the antigen were used with the same or with separate particles. In conclusion, the advantages of encapsulating MPL and RC529 lie not only in the enhanced immune response they elicit, but also in the convenience of handling these relatively insoluble compounds, and flexibility in vaccine design. The fact that MPL and RC529 are readily soluble in methylene chloride used for the manufacturing of PLG microparticles makes it easy to avoid solubility issues. Moreover, formulating antigen and immune potentiator with the same particle offers an attractive approach to vaccine delivery.
Insights
Encapsulating immune potentiators like monophosphoryl lipid A (MPL) and RC529 in poly(lactide-co-glycolide) (PLG) microparticles significantly enhances vaccine responses against HIV and Men B. This formulation strategy offers improved immunogenicity and practical advantages for vaccine development.
Area of Science:
- Vaccinology
- Immunology
- Materials Science
Background:
- Developing potent vaccines against challenging pathogens like HIV-1 and Neisseria meningitidis serotype B (Men B) requires effective immune stimulation.
- Immune potentiators, such as monophosphoryl lipid A (MPL) and synthetic lipopolysaccharide (LPS) mimetics like RC529, are crucial for enhancing vaccine efficacy.
- Poly(lactide-co-glycolide) (PLG) microparticles offer a versatile platform for vaccine delivery, enabling controlled release and improved antigen presentation.
Purpose of the Study:
- To evaluate MPL and RC529, encapsulated in PLG microparticles, as immune potentiators for HIV-1 gp120 and Men B antigens.
- To compare the immunogenicity of these microparticle-based formulations with soluble immune potentiators and CpG oligonucleotides in a mouse model.
- To investigate the impact of co-formulating antigens and immune potentiators within the same PLG microparticles on overall immune response.
Main Methods:
- PLG microparticles were fabricated using a water-in-oil-in-water emulsion solvent evaporation technique with RG503 polymer and Dioctylsulfosuccinate surfactant.
- MPL or RC529 were encapsulated within PLG microparticles, or antigens (HIV-1 gp120, Men B) were adsorbed onto their surface.
- Formulations were characterized for protein loading, release kinetics, and integrity before being tested in mice for antibody induction and bactericidal activity.
Main Results:
- Both soluble MPL/RC529 and encapsulated MPL/RC529 in PLG microparticles significantly enhanced immune responses to Men B and gp120 antigens compared to antigen alone.
- Encapsulating MPL or RC529 within PLG microparticles resulted in superior immune responses compared to using soluble CpG as a control.
- Co-formulating gp120 antigen with MPL or RC529 encapsulated in PLG microparticles led to further enhanced serum titers, comparable to or exceeding those achieved with soluble CpG.
Conclusions:
- Encapsulating MPL and RC529 in PLG microparticles provides a potent strategy for enhancing vaccine immunogenicity against HIV and Men B.
- This formulation approach overcomes solubility challenges of immune potentiators and offers flexibility in vaccine design.
- Co-formulating antigens and immune potentiators on the same microparticle represents an attractive and effective vaccine delivery strategy.
