A soluble and heat-resistant form of hantavirus nucleocapsid protein for the serodiagnosis of HFRS

Abstract

Hemorrhagic fever with renal syndrome (HFRS) is a rodent-borne viral zoonosis characterized by fever, hemorrhagic manifestations, and renal disorder. The causative agent of HFRS has been identified as a hantavirus. Hantavirus nucleocapsid proteins have recently been shown to be immunodominant antigens in HFRS, inducing an early and long-lasting immune response, and their amino termini are sensitive tools for the detection of specific antibodies in HFRS patient sera. Previous work has demonstrated that the introduction of the acidic tail of α-synuclein (ATS) into heat-labile proteins protects them from heat-induced aggregation. In this study, the ATS peptide was introduced into the N-terminal antigenic portion of the nucleocapsid proteins (amino acid residues 1–70) of the Hantaan virus (HTNV-ΔN) and Seoul virus (SEOV-ΔN). The recombinant ATS–HTNV-ΔN and ATS–SEOV-ΔN fusion proteins were heat-resistant, and the proteins purified by heat treatment were immunoreactive to sera from patients with HFRS. Compared with sera from patients with leptospirosis and scrub typhus, sera from patients with HFRS showed much higher reactivity in ATS–HTNV-ΔN- or ATS–SEOV-ΔN-based IgG ELISAs. Immunoblotting analysis revealed that only sera from patients with HFRS specifically recognized the ATS–HTNV-ΔN and ATS–SEOV-ΔN, indicating that the ATS–HTNV-ΔN and ATS–SEOV-ΔN were highly purified species without any other immunoreactive proteins as contaminants. These data demonstrate that the ATS–HTNV-ΔN and ATS–SEOV-ΔN fusion proteins offer a safe and inexpensive source of pure and specific antigen for large-scale diagnosis and seroepidemiological studies of HFRS, and that ATS-fusion technology can also be utilized to solubilize other antigens that could be used for large-scale diagnosis and seroepidemiological studies of other diseases.