Existence of phenol oxidase in the argasid tick Ornithodoros moubata

Phenol oxidase (PO, EC 1.10.3.1) activity was detected in the hemolymph of the fourth instar nymphs of the argasid tick, Ornithodoros moubata, with peak levels corresponding to the days before the majority of the nymphs had molted, suggestive of a protective role of PO during the ecdysial phase. Higher PO activity was detected in plasma relative to the hemolymph and was negligible in hemocytes. The concentration of the hemolymph and plasma assayed clearly influenced the level of PO activity, and was significantly reduced ( P<0.005) after treatment with 1-phenyl-2 thiourea, a specific PO inhibitor. This is the first report of the existence of PO in the hemolymph and plasma of a soft tick species. The regulation of PO activity and its precise role in soft tick immunity, particularly during the ecdysial phase, are interesting and need to be examined further.     

Roles of the Maltese cross form in the development of parasitemia and protection against Babesia microti infection in mice

Babesia microti, a hemoprotozoan parasite of rodents, is also important as a zoonotic agent of human babesiosis. The Maltese cross form, which consists of four masses in an erythrocyte, is characteristic of the developmental stage of B. microti. Monoclonal antibody (MAb) 2-1E, which specifically recognizes the Maltese cross form of B. microti, has been described previously. In the present study, we examined the roles of the Maltese cross form during the infectious course of B. microti in mice. The number of the Maltese cross form increased in the peripheral blood of infected mice prior to the peak of parasitemia. With confocal laser scanning microscopy, MAb 2-1E was found to be reactive with the ring form, with the parasites undergoing transformation to the Maltese cross form and subsequent division, and also with extracellular merozoites. Furthermore, the Maltese cross form-related antigen (MRA) gene was isolated from a B. microti cDNA library by immunoscreening with MAb 2-1E, and the nucleotide sequence was determined. Genomic analyses indicated that the MRA gene exists as a single-copy gene in B. microti. Immunization of mice with recombinant MRA induced significant protective immunity against B. microti infection. These findings indicate that the Maltese cross form plays important roles in both the development of parasitemia and the protective response against the infection.     

Study of the biological activities of toxic shock syndrome toxin-1: II. Induction of the proliferative response and the interleukin 2 production by T cells from human peripheral blood mononuclear cells stimulated with the toxin

Toxic shock syndrome toxin-1 (TSST-1) is an exotoxin produced by Staphylococcus aureus isolated from patients with toxic shock syndrome. We investigated the proliferative response of human lymphocytes and their interleukin 2 (IL-2) production after stimulation with TSST-1 in vitro. Human cord blood mononuclear cells (HCBM) and human peripheral blood mononuclear cells (HPBM) could proliferate with TSST-1 stimulation. T cell-depleted HPBM showed only a marginal response to this toxin. A IL-2-like factor with a molecular weight of 15-18 kD was obtained from the supernatants of TSST-1-stimulated HPBM cultures. The factor was absorbed by CTLL-2 cells but not by T cell-depleted murine spleen cells, indicating that it is IL-2. HPBM are very sensitive to TSST-1: a low concentration of TSST-1 (0.01 ng/ml in 36 h stimulation) and a short period of stimulation (8 h at 10 ng/ml of the toxin) were fully effective for HPBM to produce substantial amounts of IL-2. Removal of T cells abrogated the TSST-1-induced IL-2 production by HPBM. Reconstituted cell cultures of nylon wool column-passed T cells and macrophages produced IL-2 by TSST-1 stimulation and, furthermore, the accessory activity of the macrophages could be partially replaced by a macrophage-derived factor containing interleukin 1. These findings indicate that T cells require macrophages or IL-1 for TSST-1-induced production of IL-2. The roles of lymphokines, including IL-2, in the development of this illness are discussed.     

Immunopathological activities of extracellular products of Streptococcus mitis, particularly a superantigenic fraction.

Previously, we prepared extracellular products, fractions F-1 and F-2 of Streptococcus mitis 108, an isolate from the tooth surface of an infant, and showed that F-1 exhibited inflammatory cytokine-inducing activities. In the present study, we present evidence that fraction F-2 induced human T-cell proliferation in the presence of irradiated human peripheral blood mononuclear cells and selectively activated T cells bearing V beta 2 and V beta 5.1 in the T-cell receptor. F-1, on the other hand, stimulated human gingival fibroblasts to support the T-cell proliferation in the same way as human gamma interferon or Prevotella intermedia lipopolysaccharide (LPS). Fraction F-1 also primed gingival fibroblasts to support the production of interleukin-2 and gamma interferon by the T cells upon stimulation with F-2. Human gingival fibroblasts stimulated with fraction F-1, like those stimulated by P. intermedia LPS and human gamma interferon, exhibited human leukocyte antigen (HLA)-DR mRNA expression and cell surface HLA-DR molecules as detected by enzyme-linked immunosorbent assay. An anti-HLA-DR monoclonal antibody inhibited T-cell proliferation in response to F-2, probably through inactivating the accessory function of HLA-DR-bearing fibroblasts. T cells activated with F-2 in the presence of irradiated peripheral blood mononuclear cells exhibited definite cytotoxic effects against fibroblasts and squamous carcinoma cells originating from human oral tissues. These findings are strongly suggestive of an association of extracellular products of viridans streptococci with pathogenesis of oral mucosal diseases, particularly those disorders in gingiva which are accompanied by heavy infiltration of T cells.     

An immunodominant haptenic epitope of carbamazepine detected in serum from patients given long-term treatment with carbamazepine without allergic reaction

An anticarbamazepine antibody was detected in the serum of a patient with severe carbamazepine-induced serum sickness. We found that the patient's T cells and IgG antibody recognized an epitope which appeared in subjects showing an allergic reaction, as well as that in subjects who showed no allergic reaction, after long-term carbamazepine therapy. These results show that an anti-carbamazepine immune response does not occur in the majority of subjects who undergo long-term carbamazepine therapy without developing allergic symptoms, although the immunodominant haptenic epitope of carbamazepine is present in their sera.     

Purification and characterization of Staphylococcus aureus FRI 1169 and 587 toxic shock syndrome exotoxins.

An exotoxin was purified from a toxic shock toxin (TST)-producing Staphylococcus aureus strain, FRI 1169, and another exotoxin was purified from a pyrogenic exotoxin C (PEC)-producing S. aureus strain, 587. Both strains had been isolated from toxic-shock syndrome patients. The two exotoxins were purified by the same method of ion-exchange chromatography, chromatofocusing, and gel filtration. After purification, those exotoxins gave a line of identity against an anti-TST serum and also were immunologically similar to TST in a double-diffusion test. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis, each exotoxin gave a single band with a relative mobility identical to that of the other. Their molecular weights (24,000), isoelectric points (7.0), amino acid compositions, and NH2-terminal amino acid sequences (the first four residues) were identical. Both produced fever and enhanced host susceptibility to lethal endotoxin shock in rabbits, comparable with PEC. These findings show that the two exotoxins are the same protein, which is assumed to be TST. When injected into rabbits, the culture supernatant of strain 587 showed biological activity like that described above, whereas the culture supernatant neutralized with anti-TST immunoglobulin did not. This showed that PEC-producing strain 587 does not produce any toxin with these biological activities in rabbits except TST.     

Inhibitory effect of antiserum to surface antigen P50 of Babesia gibsoni on growth of parasites in severe combined immunodeficiency mice given canine red blood cells

The inhibitory effect of an antiserum to surface protein P50 of Babesia gibsoni on the growth of the parasite was determined with severe combined immunodeficiency mice given canine red blood cells. The antiserum to the recombinant P50 protein significantly inhibited the parasite growth, indicating that P50 might be a useful vaccine candidate.     

Cloning of a Novel Babesia equi Gene Encoding a 158-Kilodalton Protein Useful for Serological Diagnosis

In this study, we characterized a Babesia equi Be158 gene obtained by immunoscreening a B. equi cDNA expression phage library with B. equi-infected horse serum. The Be158 gene consists of an open reading frame of 3,510 nucleotides. The recombinant Be158 gene product was produced in Escherichia coli and used for the immunization of mice. In Western blot analysis, mouse immune serum against the Be158 gene product recognized 75- and 158-kDa proteins from the lysate of B. equi-infected erythrocytes. In an indirect fluorescent-antibody test with the mouse immune serum, the Be158 antigen appeared in the cytoplasm of Maltese cross-forming parasites (which consist of four merozoites) and was located mainly in the extraerythrocytic merozoite body. When the recombinant Be158 gene product was used in an enzyme-linked immunosorbent assay as a serological antigen, it was found to react to B. equi-infected horse sera, indicating that the Be158 gene product is useful as a serologically diagnostic antigen for B. equi infection.     

Expression of Babesia equi merozoite antigen 1 in insect cells by recombinant baculovirus and evaluation of its diagnostic potential in an enzyme-linked immunosorbent assay

The gene encoding the entire Babesia equi merozoite antigen 1 (EMA-1) was inserted into a baculovirus transfer vector, and a recombinant virus expressing EMA-1 was isolated. The expressed EMA-1 was transported to the surface of infected insect cells, as judged by an indirect fluorescent-antibody test (IFAT). The expressed EMA-1 was also secreted into the supernatant of a cell culture infected with recombinant baculovirus. Both intracellular and extracellular EMA-1 reacted with a specific antibody in Western blots. The expressed EMA-1 had an apparent molecular mass of 34 kDa that was identical to that of native EMA-1. The secreted EMA-1 was used as an antigen in an enzyme-linked immunosorbent assay (ELISA). The ELISA differentiated B. equi-infected horse sera from Babesia caballi-infected horse sera or normal horse sera. The ELISA was more sensitive than the complement fixation test and IFAT. These results demonstrated that the recombinant EMA-1 expressed in insect cells might be a useful diagnostic reagent for detection of antibodies to B. equi.