An agonist of human complement fragment C5a enhances vaccine immunity against Coccidioides infection

Abstract

Coccidioides is a fungal pathogen and causative agent of a human respiratory disease against which no clinical vaccine exists. In this study we evaluated a novel vaccine adjuvant referred to as EP67, which is a peptide agonist of the biologically active C-terminal region of human complement component C5a. The EP67 peptide was conjugated to live spores of an attenuated vaccine strain (ΔT) of C. posadasii. The non-conjugated ΔT vaccine provided partial protection to BALB/c mice against coccidioidomycosis. In this report we compared the protective efficacy of the ΔT-EP67 conjugate to the ΔT vaccine in BALB/c mice. Animals immunized subcutaneously with the ΔT-EP67 vaccine showed significant increase in survival and decrease in fungal burden over 75 days postchallenge. Increased pulmonary infiltration of dendritic cells and macrophages was observed on day 7 postchallenge but marked decrease in neutrophil numbers had occurred by 11 days. The reduced influx of neutrophils may have contributed to the observed reduction of inflammatory pathology. Mice immunized with the ΔT-EP67 vaccine also revealed enhanced expression of MHC II molecules on the surface of antigen presenting cells, and in vitro recall assays of immune splenocytes showed elevated Th1- and Th17-type cytokine production. The latter correlated with a marked increase in lung infiltration of IFN-γ- and IL-17-producing CD4+ T cells. Elevated expression of T-bet and RORc transcription factors in ΔT-EP67-vaccinated mice indicated the promotion of Th1 and Th17 cell differentiation. Higher titers of Coccidioides antigen-specific IgG1 and IgG2a were detected in mice immunized with the EP67- conjugated versus the non-conjugated vaccine. These combined results suggest that the EP67 adjuvant enhances protective efficacy of the live vaccine by augmentation of T-cell immunity, especially through Th1- and Th17-mediated responses to Coccidioides infection.

Complement C5a acts as molecular adjuvant in fish by enhancing antibody response to soluble antigen

“…Development of novel vaccines based on the use of complement molecules as adjuvant is currently under investigation in mammals [7,8]. In this regard, several complement activation fragments, such as C3d and C5a have been shown to enhance antibody and antigenspecific cytotoxic T lymphocyte (CTL) responses respectively thereby acting as molecular adjuvants [7,9].…”

Card9- and MyD88-Mediated Gamma Interferon and Nitric Oxide Production Is Essential for Resistance to Subcutaneous Coccidioides posadasii Infection

“…Tissue fixation and embedding procedures were performed as previously described (30), and tissue sections (5 m thick) were stained with hematoxylin and eosin (H&E) or Gomori methenamine silver stain (GMS) by standard procedures. Sections were examined using a Leica DMI6000 microscope equipped with an automated TurboScan stage (Objective Imaging, Ltd., Cambridge, United Kingdom), and microscope images of subcutaneous abscesses were acquired and analyzed using Surveyor software (Objective Imaging) as reported elsewhere (31).…”

Construction and Evaluation of a Novel Recombinant T Cell Epitope-Based Vaccine against Coccidioidomycosis

“…Nonvaccinated mice were immunized with adjuvant alone. Mice were sacrificed at 9 days postchallenge for determination of the fungal burden in their lungs and spleen as previously described (22,23). Survival studies of vaccinated versus nonvaccinated mice were conducted over 3 weeks postchallenge as previously reported (52).…”