Kinetics and Magnitude of Antibody Responses against the Conserved 47-Kilodalton Antigen and the Variable 56-Kilodalton Antigen in Scrub Typhus Patients

Chen, Huawei; Zhang, Zhiwen; Huber, Erin; Mutumanje, Elissa; Chao, Chien‐Chung; Ching, Wei‐Mei

doi:10.1128/cvi.00017-11

Cited by 30 publications

(27 citation statements)

References 29 publications

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“…Previously, it was suggested that the 47-kDa protein, an HtrA homolog of O. tsutsugamushi, might be a useful antigen if combined with TSA56 for serological diagnosis (8,15). However, specific antibody titers against the 47-kDa antigen in human patients are relatively low during the acute phase of infection (8), which might be due to antibody cross-reaction with human serine protease or HtrAs of other bacteria (7). We also consistently observed relatively low levels of specific antibody responses against the 47-kDa antigen in our human patients (Fig.…”

Section: Discussionmentioning

confidence: 99%

Detection of Antibodies against Orientia tsutsugamushi Sca Proteins in Scrub Typhus Patients and Genetic Variation of sca Genes of Different Strains

Kim

Choi

et al. 2012

Clin Vaccine Immunol

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ABSTRACTScrub typhus, caused byOrientia tsutsugamushiinfection, is one of the main causes of acute febrile illness in the Asian-Pacific region. Although early diagnosis and immediate antibiotic treatment are critical for reducing disease severity and mortality, current diagnostic methods using serological and molecular approaches have some limitations in sensitivity and applicability in clinical laboratories. In this study, we identified and characterizedO. tsutsugamushisurface cell antigen (sca) family genes encoding autotransporter proteins in order to test them as novel diagnostic targets. We evaluated antibody responses against the Sca proteins in scrub typhus patient sera and examined the genetic diversity of these genes in different strains after PCR amplification. Specific antibody responses against ScaA and ScaC were observed in patients with high indirect immunofluorescence assay titers (≥1:640), whereas specific responses against ScaB and ScaE were relatively low. Genetic analysis using genomic DNAs revealed thescagenes to be quite variable among the different strains. In contrast toscaA,scaC, andscaD, which were detected in all of the tested strains,scaBandscaEwere amplified differentially from the different strains, suggesting a differential presence of the genes in the genomes. Among the members of the gene family, the sequence ofscaCis the most highly conserved between the different strains, and the size ofscaDis the most variable due to the presence of different numbers of internal repeat sequences. These results suggest that thescagenes ofO. tsutsugamushimay be valuable targets for use in combination with classical assay methods for scrub typhus diagnosis.

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Section: Discussionmentioning

confidence: 99%

Detection of Antibodies against Orientia tsutsugamushi Sca Proteins in Scrub Typhus Patients and Genetic Variation of sca Genes of Different Strains

Kim

Choi

et al. 2012

Clin Vaccine Immunol

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“…The sensitivity and specificity of this assay, which were calculated from confirmed and non-scrub typhus patients, were 86.5% (95% CI: 74.2 to 94.4) and 100% (95% CI: 97.3 to 100), respectively. In addition, using real-time PCR and IFA results, we identified five patients with secondary infection characterized by a high IgG titer with a relatively low IgM titer (12). Among these patients, four exhibited a high (Ն1:3,200) IgG titer, with or without an apparent 4-fold increase; a relatively low IgM titer (Յ1: 400); and positive PCR results.…”

Section: Resultsmentioning

confidence: 99%

Use of Multiplex Real-Time PCR To Diagnose Scrub Typhus

et al. 2017

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Scrub typhus, caused by Orientia tsutsugamushi, is a common cause of acute undifferentiated febrile illness in the Asia-Pacific region. However, its nonspecific clinical manifestation often prevents early diagnosis. We propose the use of PCR and serologic tests as diagnostic tools. Here, we developed a multiplex real-time PCR assay using hydrolysis (TaqMan) probes targeting O. tsutsugamushi 47-kDa, groEL, and human interferon beta (IFN-␤ gene) genes to improve early diagnosis of scrub typhus. The amplification efficiency was higher than 94%, and the lower detection limit was 10 copies per reaction. We used a human gene as an internal DNA quality and quantity control. To determine the sensitivity of this PCR assay, we selected patients with confirmed scrub typhus who exhibited a clear 4-fold increase in the level of IgG and/or IgM. The PCR assay result was positive in 45 of 52 patients, indicating a sensitivity of 86.5% (95% confidence interval [CI]: 74.2 to 94.4). The PCR assessment was negative for all 136 non-scrub typhus patients, indicating a specificity of 100% (95% CI: 97.3 to 100). In addition, this test helped diagnose patients with inconclusive immunofluorescence assay (IFA) results and using single blood samples. In conclusion, the real-time PCR assay proposed here is sensitive and specific in diagnosing scrub typhus. Combining PCR and serologic tests will improve the diagnosis of scrub typhus among patients presenting with acute febrile illness.KEYWORDS Orientia tsutsugamushi, real-time PCR, scrub typhus S crub typhus is a mite-borne infectious disease caused by the obligate intracellular bacterium Orientia tsutsugamushi. A characteristic feature of the disease is patients presenting nonspecific symptoms, including fever, headache, myalgia, cough, and abdominal pain, which cannot be differentiated from symptoms of other systemic infections. The presence of eschar can help diagnose this illness; however, it is found only in some patients (1). Although the clinical course of scrub typhus is usually mild and self-limiting, delaying the treatment in severe cases can lead to complications such as renal failure, myocarditis, meningoencephalitis, and death (2). Since scrub typhus is one of the most common causes of acute undifferentiated febrile illness (AUFI) in areas of endemicity (3, 4), an early, definite diagnosis is essential for providing appropriate treatment and gathering accurate epidemiological data.Scrub typhus diagnosis mainly relies on serologic tests, particularly the indirect immunofluorescence assay (IFA), whereby the illness is identified by a 4-fold increase in antibody titers in paired sera (5, 6) and/or a positive IgM titer in a single serum sample (7,8). However, these serologic tests require paired serum samples and good technician expertise, and even then they often return false negatives during the early phase of disease. In addition, reinfection by different O. tsutsugamushi strains is not uncommon in areas of endemicity and reinfected patients may sometimes

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“…ELISA was performed as previously described [61]. The cutoff was determined by using the mean of the sham group plus 1.745 times the standard deviation for the 95% confidence interval [62].…”

Section: Recombinant Protein Antigen Based Elisa For Antibody Detectionmentioning

confidence: 99%

Temporal analysis of mRNA expression profiles in Orientia infected C3HeB/FeJ mouse

et al. 2020

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Background: Scrub typhus causes up to 35% mortality if left untreated. One billion people living in the endemic regions are at risk. In spite of its heavy disease burden in some of the most populated areas in the world, there is no vaccine available. Although the disease can be effectively treated by proper antibiotics, timely and accurate diagnosis remains a challenge. Orientia tsutsugamushi infects a variety of mammalian cells in vitro and replicates in the cytoplasm of the infected cells. Microarray analysis has been used extensively to study host-pathogen interactions in in vitro models to understand pathogenesis. However there is a lack of in vivo studies. Results: In this study, C3HeB/FeJ (C3H) mice were infected by O. tsutsugamushi via the intraperitoneal route and monitored gene expression at 10 different time points post infection. We observed two distinct types of expression profiles in the genes that we analyzed. There are two valleys (4-18 h and 2-4 days) with low number of differentially expressed genes (DEG) with three peaks with high number of DEG at 2 h, 1-day and 7-day post infection. Further analysis revealed that pathways like complement and coagulation cascade, and blood clotting cascade pathways showed significant global changes throughout entire time course. Real time quantitative Polymerase Chain Reaction (RT-qPCR) confirmed the change of expression for genes involved in complement and coagulation cascade. These results suggested dynamic regulation of the complement and coagulation cascades throughout most of the time post infection while some other specific pathways, such as fatty acid metabolism and tryptophan metabolism, are turned on or off at certain times post infection. Conclusions: The findings highlight the complex interconnection among all different biological pathways. It is conceivable that specific pathways such as cell growth control and cell development in the host are affected by Orientia in the initial phase of infection for Orientia to grow intracellularly. Once Orientia is replicating successfully inside the host as infection progresses, the infection could activate pathways involved in cellular immune responses to defend for host cell survival and try to eliminate the pathogen.

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Kinetics and Magnitude of Antibody Responses against the Conserved 47-Kilodalton Antigen and the Variable 56-Kilodalton Antigen in Scrub Typhus Patients

Cited by 30 publications

References 29 publications

Detection of Antibodies against Orientia tsutsugamushi Sca Proteins in Scrub Typhus Patients and Genetic Variation of sca Genes of Different Strains

Detection of Antibodies against Orientia tsutsugamushi Sca Proteins in Scrub Typhus Patients and Genetic Variation of sca Genes of Different Strains

Use of Multiplex Real-Time PCR To Diagnose Scrub Typhus

Temporal analysis of mRNA expression profiles in Orientia infected C3HeB/FeJ mouse

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