A novel lipid nanoparticle adjuvant significantly enhances B cell and T cell responses to sub-unit vaccine antigens

📖 Top 20% JournalNov 12, 2015Vaccine

New fat-based particle boosts B cell and T cell responses to subunit vaccines

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Abstract

Lipid nanoparticles significantly enhanced immune responses to hepatitis B virus surface antigen and ovalbumin in mouse models.

Immunization with lipid nanoparticles and a synthetic TLR9 agonist improved total B-cell responses to tested antigens.
Responses to lipid nanoparticles were comparable to traditional vaccine adjuvants like aluminum-based adjuvant and MPL.
The combination of lipid nanoparticles with the TLR9 agonist elicited a stronger Th1-type immune response than the agonist alone.
Lipid nanoparticles enhanced antigen-specific CD4(+) and CD8(+) T cell responses, indicating a robust cell-mediated immune reaction.
Higher frequencies of multi-functional CD8(+) T cells producing cytokines were observed with lipid nanoparticles compared to unadjuvanted vaccines.

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Sub-unit vaccines are primarily designed to include antigens required to elicit protective immune responses and to be safer than whole-inactivated or live-attenuated vaccines. But their purity and inability to self-adjuvant often result in weaker immunogenicity. Emerging evidence suggests that bio-engineered nanoparticles can be used as immunomodulatory adjuvants. Therefore, in this study we explored the potential of novel Merck-proprietary lipid nanoparticle (LNP) formulations to enhance immune responses to sub-unit viral antigens. Immunization of BALB/c and C57BL/6 mice revealed that LNPs alone or in combination with a synthetic TLR9 agonist, immune-modulatory oligonucleotides, IMO-2125 (IMO), significantly enhanced immune responses to hepatitis B virus surface antigen (HBsAg) and ovalbumin (OVA). LNPs enhanced total B-cell responses to both antigens tested, to levels comparable to known vaccine adjuvants including aluminum based adjuvant, IMO alone and a TLR4 agonist, 3-O-deactytaled monophosphoryl lipid A (MPL). Investigation of the quality of B-cell responses demonstrated that the combination of LNP with IMO agonist elicited a stronger Th1-type response (based on the IgG2a:IgG1 ratio) than levels achieved with IMO alone. Furthermore, the LNP adjuvant significantly enhanced antigen specific cell-mediated immune responses. In ELISPOT assays, depletion of specific subsets of T cells revealed that the LNPs elicited potent antigen-specific CD4(+) and CD8(+)T cell responses. Intracellular FACS analyses revealed that LNP and LNP+IMO formulated antigens led to higher frequency of antigen-specific IFNγ(+)TNFα(+)IL-2(+), multi-functional CD8(+)T cell responses, than unadjuvanted vaccine or vaccine with IMO only. Overall, our results demonstrate that lipid nanoparticles can serve as future sub-unit vaccine adjuvants to boost both B-cell and T-cell responses in vivo, and that addition of IMO can be used to manipulate the quality of immune responses.

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