A novel, helminth‐derived immunostimulant enhances human recall responses to hepatitis C virus and tetanus toxoid and is dependent on CD56+ cells for its action
We have described previously an immunostimulant derived from Onchocerca volvulus, the helminth parasite that causes onchocerciasis. Recombinant O. volvulus activation‐associated secreted protein‐1 (rOv‐ASP‐1) was a potent adjuvant for antibody and cellular responses to protein, polypeptide and small peptide antigens. Our aims were to determine whether rOv‐ASP‐1 is immunostimulatory for human peripheral blood mononuclear cells (PBMC) and, if so, whether it could augment cellular responses against human pathogen antigens in vitro. Cytokines from rOv‐ASP‐1‐stimulated human PBMC were measured by a fluorescence activated cell sorter‐based multiplex assay. Recall responses of normal healthy donor (NHD) and chronic hepatitis C virus (c‐HCV)‐infected patient PBMC to tetanus toxoid (TT) or HCV core (HCVco) antigen, respectively, were measured by interferon‐γ enzyme‐linked immunospot assays. Interferon‐γ was the predominant cytokine induced by rOv‐ASP‐1. 77·3% of NHD anti‐TT and 88·9% of c‐HCV anti‐HCVco responses were enhanced by rOv‐ASP‐1. The immunostimulant effect was dependent upon contact between CD56+ and CD56‐ fractions of PBMC. We have described a helminth‐derived protein that can act as an immunostimulant for human recall responses in vitro to TT and, perhaps more importantly, HCV antigens in patients with chronic HCV infection. Our longer‐term goal would be to boost anti‐viral responses in chronic infections such as HCV.