Partial Characterization of Two Cathepsin D Family Aspartic Peptidases of Clonorchis sinensis

Cathepsin D (CatD, EC 3.4.23.5) is a member belonging to the subfamily of aspartic endopeptidases, which are classified into the MEROPS clan AA, family A1. Helminth parasites express a large set of different peptidases that play pivotal roles in parasite biology and pathophysiology. However, CatD is less well known than the other classes of peptidases in terms of biochemical properties and biological functions. In this study, we identified 2 novel CatDs (CsCatD1 and CsCatD2) of Clonorchis sinensis and partially characterized their properties. Both CsCatDs represent typical enzymes sharing amino acid residues and motifs that are tightly conserved in the CatD superfamily of proteins. Both CsCatDs showed similar patterns of expression in different developmental stages of C. sinensis, but CsCatD2 was also expressed in metacercariae. CsCatD2 was mainly expressed in the intestines and eggs of C. sinensis. Sera obtained from rats experimentally infected with C. sinensis reacted with recombinant CsCatD2 beginning 2 weeks after infection and the antibody titers were gradually increased by maturation of the parasite. Structural analysis of CsCatD2 revealed a bilobed enzyme structure consisting of 2 antiparallel β-sheet domains packed against each other forming a homodimeric structure. These results suggested a plausible biological role of CsCatD2 in the nutrition and reproduction of parasite and its potential utility as a serodiagnostic antigen in clonorchiasis.

Multi-Epitope Fusion Protein Eg mefAg-1 as a Serodiagnostic Candidate for Cystic Echinococcosis in Sheep

Cystic echinococcosis (CE) in sheep is a hazardous zoonotic parasitic disease that is caused by Echinococcus granulosus (Eg). At present, serological test is an important diagnostic method for Eg infection in domestic animals. Here, a fusion protein Eg mefAg-1 harboring 8 dominant B-cell epitopes of Eg such as antigen B, tetraspanin 1, tetraspanin 6, reticulon and Eg95 was produced in E. coli and evaluated for CE in sheep by indirect ELISA. Eg mefAg-1 showed in ELISA a high sensitivity (93.41%) and specificity (99.31%), with a coincidence rate of 97.02%. Overall, it is suggested that the Eg mefAg-1 could be a potential antigen candidate for CE serodiagnosis in sheep.

Mycobacterial heparin-binding haemagglutinin adhesion-induced interferon & antibody for detection of tuberculosis.

Background & objectives: Mycobacterial heparin-binding haemagglutinin adhesin (HBHA) plays an important role in humoral and cellular immune response and is a potential diagnostic tool for tuberculosis (TB) serodiagnosis. This study was carried out to assess the usefulness of HBHA in TB clinics for differential diagnosis of pulmonary and extra-pulmonary TB (PTB, EPTB). Methods: In this study, 165 outpatients and 133 healthy volunteers were included to investigate the role of HBHA in TB diagnosis including the serodiagnostic tests and the interferon-γ release assays (IGRAs). The healthy volunteers were all without BCG vaccination including 73 subjects with purified protein derivative (PPD) (-) and 60 ones with PPD (+) (that is P-B- and P+B-). Of all the 165 outpatients 77 were PTB and 88 were EPTB. HBHA protein was used for serodiagnostic tests and IGRAs in peripheral blood mononuclear cells. Results: HBHA-specific antibody levels in the serum of healthy subjects were significantly different from the patients with PTB or EPTB (P<0.05). HBHA specific antibody levels in PTB patients could differentiate from EPTB with limited sensitivity (77.08%; 95%CI, 62.69 to 87.97%) and specificity (87.50%; 95%CI, 74.75 to 95.27%). IFN-γ levels in the healthy (P+B- and P-B-) groups were significantly different (P<0.01) with a detection sensitivity of 84.8% (95%CI, 68.54 to 93.02%) and specificity of 80.7% (95%CI, 65.22 to 92.62%). The PTB and EPTB subjects showed no difference in IFN-γ production. Interpretation & conclusions: HBHA serodiagnostic test with IGRAs had the limited potential for use as auxiliary tools for the differential diagnosis of PTB and EPTB, since both methods showed low sensitivity and specificity.

Efficacy of the Merozoite Surface Protein 1 of Plasmodium Vivax as an Antigen for ELISA to Diagnose Malaria

Malaria is still a major health problem in Thailand and its incidence is currently rising in Korea. To identify a useful antigen for the diagnosis of malaria patients, a cDNA expression library from malaria parasites was constructed and screened out immunologically. One clone was selected in view of its predominant reactivity with the patient sera. The recombinant malaria parasite antigen (Pv30) with 27 kDa as a C-terminal His-tag fusion protein that was produced in Escherichia coli was identified through immunoblot analysis. The deduced amino acid sequence had the sequence homology with the merozoite surface protein 1 (MSP1) genes of Plasmodium falciparum and P. yoelii, each by 41% and 42%, respectively. Measurement of serum IgG and IgM antibody to Pv30 by enzyme-linked immunosorbent assay (ELISA) was evaluated as a serodiagnostic test for malaria patients in Thailand (endemic area) and Korea (recently reemerging area). The sensitivity of P. vivax, P. falciparum, and P. malariae was 96.3% (26 /27), 90.6% (29/32), and 100% (6/6), respectively, and the specificity was 63.5% (40/63) in Thailand samples. The sensitivity of P. vivax was 98.8% (88/89), and the specificity was 96.6% (86/89) in Korean samples. Pv30 appears to be a good and reliable recombinant antigen for serodiagonosis of malaria in a nonendemic area.