IgG2 antibodies against a clinical grade Plasmodium falciparum CSP vaccine antigen associate with protection against transgenic sporozoite challenge in mice

PLoS One. 2014 Oct 24;9(10):e111020. doi: 10.1371/journal.pone.0111020. eCollection 2014.

Abstract

The availability of a highly purified and well characterized circumsporozoite protein (CSP) is essential to improve upon the partial success of recombinant CSP-based malaria vaccine candidates. Soluble, near full-length, Plasmodium falciparum CSP vaccine antigen (CS/D) was produced in E. coli under bio-production conditions that comply with current Good Manufacturing Practices (cGMP). A mouse immunogenicity study was conducted using a stable oil-in-water emulsion (SE) of CS/D in combination with the Toll-Like Receptor 4 (TLR4) agonist Glucopyranosyl Lipid A (GLA/SE), or one of two TLR7/8 agonists: R848 (un-conjugated) or 3M-051 (covalently conjugated). Compared to Alum and SE, GLA/SE induced higher CS/D specific antibody response in Balb/c mice. Subclass analysis showed higher IgG2:IgG1 ratio of GLA/SE induced antibodies as compared to Alum and SE. TLR synergy was not observed when soluble R848 was mixed with GLA/SE. Antibody response of 3M051 formulations in Balb/c was similar to GLA/SE, except for the higher IgG2:IgG1 ratio and a trend towards higher T cell responses in 3M051 containing groups. However, no synergistic enhancement of antibody and T cell response was evident when 3M051 conjugate was mixed with GLA/SE. In C57Bl/6 mice, CS/D adjuvanted with 3M051/SE or GLA/SE induced higher CSP repeat specific titers compared to SE. While, 3M051 induced antibodies had high IgG2c:IgG1 ratio, GLA/SE promoted high levels of both IgG1 and IgG2c. GLA/SE also induced more potent T-cell responses compared to SE in two independent C57/BL6 vaccination studies, suggesting a balanced and productive T(H1)/T(H2) response. GLA and 3M-051 similarly enhanced the protective efficacy of CS/D against challenge with a transgenic P. berghei parasite and most importantly, high levels of cytophilic IgG2 antibodies were associated with protection in this model. Our data indicated that the cGMP-grade, soluble CS/D antigen combined with the TLR4-containing adjuvant GLA/SE warrants further evaluation for protective responses in humans.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Antibodies, Monoclonal / immunology
  • Antibodies, Protozoan / immunology*
  • Antigens, Protozoan / immunology*
  • B-Lymphocytes / immunology
  • B7-2 Antigen / metabolism
  • Dose-Response Relationship, Immunologic
  • Enzyme-Linked Immunosorbent Assay
  • Immunity
  • Immunoglobulin G / immunology*
  • Ligands
  • Malaria Vaccines / immunology*
  • Malaria, Falciparum / immunology
  • Malaria, Falciparum / prevention & control*
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Plasmodium falciparum / immunology*
  • Protozoan Proteins / immunology*
  • Sporozoites / immunology*
  • Toll-Like Receptors / agonists
  • Vaccination

Substances

  • Antibodies, Monoclonal
  • Antibodies, Protozoan
  • Antigens, Protozoan
  • B7-2 Antigen
  • Immunoglobulin G
  • Ligands
  • Malaria Vaccines
  • Protozoan Proteins
  • Toll-Like Receptors
  • circumsporozoite protein, Protozoan

Grants and funding

Funding for this work was provided by the US Army and the United States Agency for International Development Malaria Vaccine Program. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.