Comparison of dengue virus antigens in sera and peripheral blood mononuclear cells from dengue infected patients.

The presence of dengue virus antigens in acute sera and peripheral blood mononuclear cells (PBMC) from dengue infected patients were determined by a biotin-streptavidin enzyme-linked immunosorbent assay (BS-ELISA). The frequency of the antigens detected in PBMC was higher than that in sera (53.8% vs 18.9%). In comparison with sera, the detection rate in PBMC was greater than six times: 7 cases were positive only in sera whereas 44 cases were positive only in PBMC, p < 0.001. The presence of the antigens in the sera did not depend on the severity of the disease, i.e. dengue fever, dengue hemorrhagic fever (grades I and II) or dengue shock syndrome (grades III and IV). In contrast, the presence of the antigens in PBMC increased from 36.8% to 100% when the infection was more severe. The dengue virus antigens could be detected in the samples collected between day 2 and day 7 after onset of the disease with the highest rate of detection (68.8%) in PBMC collected on day 4. The data suggest the use of PBMC with access to the appropriate acute-phase specimen for detection of dengue virus antigens.

Characterization of two monoclonal antibodies against teguments of adult and schistosomula of Schistosoma japonicum.

Two monoclonal antibodies (McAbs) were produced from BALB/c mice hyperimmunized with tegumental extract of Schistosoma japonicum (Chinese strain). The two McAbs were characterized with regard to antibody isotype, antigen binding specificity and parasite stage specificity. One McAb, 8G9-5, was identified as IgM, whereas the other McAb, 9E7, was determined to be IgG2a. Immunoblotting assay indicated that McAb 8G9-5 binds strongly to the band of tegumental antigens of Mr 64 kDa but also binds weakly to other bands at 116, 105, 97, 54, 50, 47 and 45 kDa, whereas 9E7 McAb reacts specifically at Mr 54 kDa. Anatomical localization of the antigens in the adult worm by indirect immunofluorescence assay indicated that the target epitopes of McAb 8G9-5 are in the intra-tegumental structure, whereas the McAb 9E7 epitope is on the surface membrane. The two McAbs also react at similar sites within the teguments of schistosomula and lung worms.