Early diagnosis of scrub typhus with a rapid flow assay using recombinant major outer membrane protein antigen (r56) of Orientia tsutsugamushi.
(9/261)
The variable 56-kDa major outer membrane protein of Orientia tsutsugamushi is the immunodominant antigen in human scrub typhus infections. We developed a rapid immunochromatographic flow assay (RFA) for the detection of immunoglobulin M (IgM) and IgG antibodies to O. tsutsugamushi. The RFA employs a truncated recombinant 56-kDa protein from the Karp strain as the antigen. The performance of the RFA was evaluated with a panel of 321 sera (serial bleedings of 85 individuals suspected of scrub typhus) which were collected in the Pescadore Islands, Taiwan, from 1976 to 1977. Among these 85 individuals, IgM tests were negative for 7 cases by both RFA and indirect fluorescence assay (IFA) using Karp whole-cell antigen. In 29 cases specific responses were detected by the RFA earlier than by IFA, 44 cases had the same detection time, and 5 cases were detected earlier by IFA than by RFA. For IgG responses, 4 individuals were negative with both methods, 37 cases exhibited earlier detection by RFA than IFA, 42 cases were detected at the same time, and 2 cases were detected earlier by IFA than by RFA. The sensitivities of RFA detection of antibody in sera from confirmed cases were 74 and 86% for IgM and IgG, respectively. When IgM and IgG results were combined, the sensitivity was 89%. A panel of 78 individual sera collected from patients with no evidence of scrub typhus was used to evaluate the specificity of the RFA. The specificities of the RFA were 99% for IgM and 97% for IgG. The sensitivities of IFA were 53 and 73% for IgM and IgG, respectively, and were 78% when the results of IgM and IgG were combined. The RFA test was significantly better than the IFA test for the early detection of antibody to scrub typhus in primary infections, while both tests were equally sensitive with reinfected individuals. (+info)
Intracellular localization of Rickettsia tsutsugamushi in polymorphonuclear leukocytes.
(10/261)
Rickettsia tsutsugamushi (Gilliam strain) was serially propagated in BHK-21 cell cultures and incubated with guinea pig peritoneal polymorphonuclear leukocytes to study the ultrastructural features of rickettsial uptake and entry into the leukocytes. Significant numbers of rickettsiae were phagocytized selectively by these leukocytes within 30 min. About one-half of these rickettsiae remained sequestered in phagosomes but the other one-half were free from the phagosome and localized directly in the polymorphonuclear leukocyte cytoplasm. Various stages of rickettsial release from the phagosomes were observed. Once free within the polymorphonuclear leukocyte cytoplasm, the rickettsiae were preferentially localized in the glycogen-packed areas which are devoid of lysosomes and other cytoplasmic organelles. This study indicates that rickettsiae phagocytized by polymorphonuclear leukocytes can escape from the phagosome into the cytoplasm. (+info)
Identification of the target cells of Orientia tsutsugamushi in human cases of scrub typhus.
(11/261)
Orientia tsutsugamushi is the etiologic agent of scrub typhus, a chigger-borne zoonosis that is a highly prevalent, life-threatening illness of greatest public health importance in tropical Asia and the islands of the western Pacific Ocean. The target cell of this bacterium is poorly defined in humans. In this study, O. tsutsugamushi were identified by immunohistochemistry using a rabbit polyclonal antibody raised against O. tsutsugamushi Karp strain in paraffin-embedded archived autopsy tissues of three patients with clinical suspicion of scrub typhus who died during World War II and the Vietnam War. Rickettsiae were located in endothelial cells in all of the organs evaluated, namely heart, lung, brain, kidney, pancreas, and skin, and within cardiac muscle cells and in macrophages located in liver and spleen. Electron microscopy confirmed the location of rickettsiae in endothelium and cardiac myocytes. (+info)
Gamma-irradiated scrub typhus immunogens: broad-spectrum immunity with combinations of rickettsial strains.
(12/261)
Scrub typhus immunogens were prepared from Rickettsia tsutsugamushi strains Karp, Kato, Gilliam, Kostival, and Buie by exposing frozen infected yolk sac suspensions to 300 krad of gamma radiation. Mouse protection tests showed that each of the irradiated immunogens protected C3H/HeDub mice against high challenge levels of Karp and Gilliam, but that none of these single-strain immunogens were capable of protecting against all five of the challenge strains. Broad-spectrum protection was achieved by using combinations of three strains of irradiated rickettsiae in a vaccination regimen of three injections at 5-day intervals. A comparison of vaccination efficacy employing three such combinations (Karp-Gilliam-Kato, Karp-Kostival-Kato, and Buie-Kostival-Kato) indicated that both sequential administration of strains on successive vaccination days and multiple injections of trivalent mixtures produced protective responses superior to those obtained with single-strain immunogens. Trivalent mixtures of rickettsiae exhibited a striking synergistic effect on the immune response of C3H/HeDub mice and elicited a protective response against Kato challenge that could not be obtained with any single-strain immunogen. Mice vaccinated with the trivalent Karp-Gilliam-Kato immunogen resisted challenge with more than 10(3) 50% mouse lethal doses of Karp and Gilliam for 12 months, and were resistant to similar levels of challenge with Kato and Buie for 6 months. (+info)
Passive transfer of scrub typhus plasma to patients with AIDS: a descriptive clinical study.
(13/261)
We examined the HIV-inhibitory effects previously found to be associated with scrub typhus infection. Individual 500 ml units of plasma from donors with mild scrub typhus were safety-tested, subjected to virucidal heat treatment, and administered to 10 HIV-1-infected recipients who were not receiving antiretroviral drugs. HIV-1 copy number fell three-fold or more in two recipients, and virus burden was reduced for 8 weeks in 70% (7/10) of recipients of a single plasma infusion, compared with the mean of three pre-infusion measurements. Scrub typhus donor plasma inhibited HIV-1 in vitro compared with normal human plasma and media controls. In the clearest in vivo response, reduction in viral load was accompanied by clinical improvement, a switchback from the syncytia-inducing to the non-syncytia-inducing phenotype, and decreases in CD8 cells and IL-6 levels. Scrub typhus infections can generate heat-stable, transferable plasma factors that exert prolonged anti-HIV effects. Whether variability in the results is due to different scrub typhus infections, different HIV infections or different individual responses, is unclear. (+info)
Orientia tsutsugamushi in peripheral white blood cells of patients with acute scrub typhus.
(14/261)
Scrub typhus, caused by Orientia tsutsugamushi, is an acute illness that occurs in many parts of Asia. Clinical manifestations range from inapparent to organ failure. Organisms disseminate from the skin to target organs, suggesting that they may enter the peripheral circulation. Here, peripheral blood cell smears from patients with acute scrub typhus were obtained before treatment and for 2 days after treatment and reacted with antibodies specific for O. tsutsugamushi. White blood cells from 3 of 7 patients with acute scrub typhus stained positively for O. tsutsugamushi. Cells containing O. tsutsugamushi were mononuclear and were detected on each day of sampling. The presence of O. tsutsugamushi in peripheral white blood cells of patients with acute scrub typhus is a new finding with clinical and pathogenic implications. (+info)
Natural foci of tsutsugamushi disease in the Nan Peng Lie Islands in China.
(15/261)
OBJECTIVE: To investigate natural foci of tsutsugamushi disease whose incidence has increased in the Nan Peng Lie Islands in China, an area where this disease has not been previously recorded. METHODS: We recorded the natural foci and isolated Orientia tsutsugamushi (O. tsutsugamushi) organism. We also studied prevention measures. RESULTS: These islands had the natural foci of a south subtropical zone. The main host and vector were Rattus norvegicus and Leptotrombidium deliens (L. deliens), respectively. The seasonal quantity trends of Rattus norvegicus and Leptotrombidium deliens were consistent with the incidence of human infection. Thirty-five strains of O. tsutsugamushi were isolated from Rattus norvegicus and L. deliense. The identification of 7 strains showed that most strains were Karp. Seroepidemiology showed a high prevalence of antibody against O. tsatsugamushi among local people. After prevention measures were used, the incidence was decreased. CONCLUSION: This was the first successful confirmation that the Nan Peng Lie Islands were natural foci of tsutsugamushi disease. (+info)
Successful diagnosis using scab for PCR specimen in Tsutsugamushi disease.
(16/261)
We treated a case of Tsutsugamushi disease diagnosed by polymerase chain reaction (PCR) using a scab specimen at the bite site of trombiculid mites. Otherwise the diagnosis could not be confirmed by serum antibody test nor the PCR test of blood. The genome of Rickettsia tsutsugamushi was detected and identified as the Kawasaki serotype strain. An attempt to extract the genome from the scab has not been reported, thus our data suggest that the scab is a useful specimen to confirm the diagnosis of Tsutsugamushi disease. (+info)