Orientia tsutsugamushi Recombinant Antigen (TSA56) for Scrub Typhus IgM/IgG Rapid Test LFA & ELISA IVD Development
Scrub typhus is an acute febrile illness caused by Orientia tsutsugamushi — an obligate intracellular gram-negative bacterium in the order Rickettsiales, family Rickettsiaceae. The disease is transmitted to humans through the bite of infected larval mites (chiggers), primarily of the genus Leptotrombidium. The geographic range of scrub typhus encompasses the "tsutsugamushi triangle" — a vast area of approximately 13 million km² including South Asia (India, Bangladesh, Sri Lanka, Nepal, Pakistan), Southeast Asia (Thailand, Vietnam, Myanmar, Indonesia, Malaysia, Philippines, Laos, Cambodia), East Asia (China, Japan, South Korea, Taiwan), and Pacific islands (Australia, Papua New Guinea). Within this region, approximately 1 billion people are at risk of scrub typhus, and the WHO estimates over 1 million cases occur annually. Scrub typhus is now recognized as one of the most common causes of undifferentiated acute febrile illness in South and Southeast Asia — with studies estimating 20–30% of febrile patients admitted to hospitals in highly endemic areas testing positive for scrub typhus.
The clinical presentation of scrub typhus — acute high fever (39–41°C), headache, myalgia, lymphadenopathy, and characteristic eschar (necrotic skin lesion at the site of chigger bite) — overlaps substantially with dengue fever, malaria, leptospirosis, typhoid fever, and other tropical infections. This clinical indistinguishability makes rapid laboratory diagnosis essential for appropriate clinical management. Untreated scrub typhus has case fatality rates of 0–30% depending on the infecting O. tsutsugamushi strain; early treatment with doxycycline or azithromycin (usually within 24 hours of diagnosis) dramatically reduces mortality and disease duration. The eschar — present in only 30–60% of cases depending on geographic location — is the most specific clinical finding but is frequently missed, particularly on dark skin or in difficult-to-examine body areas.
O. tsutsugamushi pathogenesis involves obligate intracellular replication within endothelial cells and macrophages — causing vasculitis that underlies the systemic organ involvement (meningoencephalitis, myocarditis, acute respiratory distress syndrome, acute kidney injury) seen in severe scrub typhus. The 56-kDa type-specific antigen (TSA56) is the immunodominant outer membrane protein of O. tsutsugamushi, constituting approximately 25% of total outer membrane protein content. TSA56 elicits strong IgM and IgG antibody responses in infected patients, making it the primary antigen for scrub typhus serological rapid diagnostic tests. Sekbio's scrub typhus recombinant antigen — produced by recombinant expression of TSA56 protein — provides a safe (no BSL-3 containment required), scalable, and consistent antigen source for LFA and ELISA scrub typhus IgM/IgG detection test development, avoiding the hazardous native antigen production from live O. tsutsugamushi cultures.
Recombinant O. tsutsugamushi TSA56 antigen for scrub typhus LFA IgM/IgG rapid test development and ELISA serology kit manufacturing.
| Product | Pathogen | Antigen Type | Expression | Application | Storage |
|---|---|---|---|---|---|
| Scrub Typhus Recombinant Antigen | Orientia tsutsugamushi | 56-kDa TSA (TSA56) | Recombinant | LFA / ELISA coating antigen (IgM/IgG detection) | −20°C |
Contact info@sekbio.com for antigen specification sheet (MW, purity, concentration, strain coverage), MOQ, pricing, and OEM supply terms for scrub typhus rapid test development.
Recombinant TSA56 antigen for safe, scalable scrub typhus IgM/IgG rapid test development targeting 1 billion at-risk individuals across the tsutsugamushi triangle.
Native O. tsutsugamushi antigen production requires BSL-3 (Biosafety Level 3) containment facilities, as live O. tsutsugamushi is classified as a potential bioterrorism agent (Category B) and poses significant infection risk to laboratory personnel. This BSL-3 requirement creates substantial barriers for most IVD manufacturers seeking to develop scrub typhus diagnostic tests. Sekbio's recombinant TSA56 antigen is produced by heterologous expression in safe host systems (E. coli or insect cells), completely eliminating the live pathogen risk. Recombinant production allows standard manufacturing under ISO 13485 conditions without BSL-3 infrastructure — dramatically lowering the barrier to entry for scrub typhus rapid test development and enabling scalable production volumes for commercial kit manufacturing.
O. tsutsugamushi TSA56 shows 40–80% amino acid sequence diversity across strains — the primary challenge for scrub typhus diagnostic test sensitivity across geographically diverse endemic regions. Sekbio's recombinant antigen is designed for broad multi-strain coverage, incorporating sequences from clinically relevant strains circulating in target markets: Karp (dominant in Southeast Asia and Australia), Gilliam and Kato (Japan), Boryong (South Korea and China), TA716 (Taiwan). Multi-strain coverage is essential for achieving consistent diagnostic sensitivity across India, Thailand, Vietnam, South Korea, China, and other markets where different O. tsutsugamushi genotypes predominate. Contact info@sekbio.com for strain coverage data and geographic sensitivity validation information.
Scrub typhus rapid tests can detect either IgM alone (early acute infection, detectable from day 7–10 post-symptom onset) or combined IgM+IgG (broader diagnostic window covering both acute and late-presenting patients). Combined IgM+IgG rapid tests — using Sekbio's TSA56 antigen coated on two parallel test lines (IgM line with anti-human IgM capture; IgG line with anti-human IgG capture), or on a single test line with a secondary anti-human IgG + anti-human IgM mixture — provide coverage from day 7 of illness through months after infection. This dual-detection format is preferred for clinical use, where patients present at variable disease stages. Sekbio's recombinant TSA56 antigen supports both LFA IgM-only and combined IgM+IgG test strip designs. Contact info@sekbio.com for LFA coating optimization protocols.
In tertiary hospitals and rural health centers across South and Southeast Asia, scrub typhus accounts for 20–30% of acute febrile illness cases in endemic seasons. Every febrile patient presenting to a healthcare facility in the tsutsugamushi triangle is a potential scrub typhus case. Rapid IgM/IgG detection tests using Sekbio's TSA56 antigen enable same-consultation diagnosis — allowing physicians to prescribe doxycycline or azithromycin immediately, reducing clinical severity, hospitalization duration, and mortality risk. The clinical application spans primary care settings in rural India, district hospitals in Thailand and Vietnam, emergency departments in South Korean urban centers, and military medicine deployments in scrub typhus-endemic training areas. This broad, high-prevalence clinical application creates substantial commercial demand for scrub typhus rapid test kits.
Sekbio's scrub typhus recombinant antigen is produced at ELISA-grade purity, suitable for both: LFA membrane coating — direct nitrocellulose striping of purified TSA56 recombinant protein (typically at 0.5–2 mg/ml) for the IgM and/or IgG detection test lines in lateral flow strip format; ELISA plate coating — adsorption of purified TSA56 to microplate wells (typically 1–5 μg/ml) for indirect ELISA scrub typhus serology kit development for laboratory use. Supporting both formats from a single antigen source simplifies IVD product line development — enabling manufacturers to create both a rapid field test (LFA) and a quantitative laboratory assay (ELISA) from the same raw material supply and qualification data. Contact our team for antigen purity, MW, and functional performance specifications.
Sekbio's ISO 13485-certified manufacturing provides quality-documented recombinant antigen supply for scrub typhus rapid test OEM partners. Primary markets: India (500,000–1 million annual cases; major commercial diagnostic market), Thailand (hospital-based clinical diagnosis), Vietnam (national disease control program), South Korea (mandatory inclusion in febrile illness panel), China (Shandong, Fujian, Guangdong provinces). Secondary markets: military medicine in US, UK, and Australian armed forces deployed in scrub typhus-endemic regions. Contact info@sekbio.com for OEM supply agreement terms, antigen characterization data for regulatory submissions, and technical development support for scrub typhus rapid test development. Visit our Products page for the complete infectious disease diagnostic portfolio.
Recombinant TSA56 for acute febrile illness differential diagnosis, outbreak surveillance, military medicine, and scrub typhus endemic area clinical diagnostics.
Scrub typhus is a major cause of undifferentiated acute febrile illness in South and Southeast Asia — frequently misdiagnosed as dengue, malaria, or typhoid in the absence of laboratory confirmation. The eschar (pathognomonic skin lesion) is absent in 40–70% of cases. Misdiagnosis leads to inappropriate treatment (NSAIDs for presumed dengue, antimalarials for presumed malaria) and potentially fatal delays in doxycycline initiation. Rapid IgM/IgG tests built on Sekbio's TSA56 antigen enable scrub typhus to be included in point-of-care fever panel differential diagnosis — alongside malaria RDT and dengue NS1/IgM/IgG rapid tests — in frontline healthcare settings. In India alone, an estimated 500,000–1 million scrub typhus cases occur annually, making it a major commercial diagnostic opportunity for Asian IVD manufacturers developing fever panel rapid tests.
Scrub typhus outbreaks occur in new geographic areas as land use patterns change — bringing human populations into contact with chigger-infested scrub vegetation (secondary growth vegetation in cleared forest areas, riverbanks, agricultural fields). Outbreak investigation requires rapid case confirmation: scrub typhus IgM/IgG rapid tests using Sekbio's antigen enable field-based case confirmation at the outbreak site without laboratory infrastructure. India's National Center for Disease Control (NCDC) and state health departments investigate multiple scrub typhus outbreaks annually in Himachal Pradesh, Uttarakhand, Jammu & Kashmir, and northeastern states. Thailand's Bureau of Epidemiology monitors scrub typhus clusters in rural agricultural areas. Rapid tests for outbreak investigation require high sensitivity (to detect all true cases) and specificity (to avoid unnecessary chemoprophylaxis of false-positive contacts). Contact our team for high-sensitivity antigen formulation options.
Scrub typhus poses a significant threat to military personnel deployed in scrub typhus-endemic training areas and operational environments. Historical military scrub typhus outbreaks caused substantial morbidity during World War II (Pacific theater), the Korean War, and Vietnam War. Modern armed forces deployed in Asia-Pacific training exercises and operational theaters face ongoing scrub typhus risk. US military (Pacific Command), UK armed forces, Australian Defence Force, Republic of Korea Army, and Indian Army all require point-of-care scrub typhus diagnostic capability. IVD manufacturers can develop military-specification scrub typhus rapid tests using Sekbio's TSA56 antigen — optimized for field use without cold chain, at wide temperature ranges, and with minimal equipment requirements. Military procurement represents a high-value, specification-driven market for scrub typhus rapid test kit development.
Hospital clinical microbiology and infectious disease reference laboratories require quantitative or semi-quantitative scrub typhus serology testing for diagnostic confirmation of rapid test-positive cases, seroepidemiological surveys measuring scrub typhus exposure prevalence in populations, vaccine clinical trial serology (anti-TSA56 antibody titer measurement as immunogenicity endpoint), and research studies characterizing immune responses to O. tsutsugamushi infection. ELISA kits built on Sekbio's recombinant TSA56 antigen support both indirect IgM/IgG ELISA (patient antibody detection) and antibody avidity ELISA (distinguishing acute from past infection based on IgG avidity maturation). ELISA format provides quantitative optical density data unavailable from qualitative LFA strips. Contact info@sekbio.com to discuss ELISA-grade antigen formulations and coating optimization for 96-well plate ELISA kit manufacturing.
Technical and commercial questions from IVD R&D engineers developing scrub typhus rapid diagnostic tests for the Asia-Pacific market.
Scrub typhus is an acute, potentially fatal febrile illness caused by Orientia tsutsugamushi, transmitted by infected larval mites (chiggers). Endemic across the "tsutsugamushi triangle" — South Asia, Southeast Asia, East Asia, and Pacific islands — scrub typhus causes over 1 million cases annually with approximately 1 billion people at risk. Case fatality in untreated disease reaches 30%; early doxycycline treatment is curative. Clinically indistinguishable from dengue, malaria, and typhoid without laboratory testing. Scrub typhus is now recognized as the most common rickettsial disease globally and a leading cause of undifferentiated fever in South and Southeast Asian hospitals.
TSA56 (56-kDa type-specific antigen) is the immunodominant outer membrane protein of O. tsutsugamushi, constituting ~25% of total outer membrane protein. It elicits strong IgM and IgG antibody responses in infected patients (IgM detectable from day 7–10 post-onset; IgG from day 10–14). TSA56 is the antigen used in all commercial scrub typhus rapid tests (InBios, Biopanda, Standard Diagnostics). Sekbio's recombinant TSA56 provides a safe (no BSL-3 required), scalable, and consistent alternative to native O. tsutsugamushi antigen for IVD kit development.
Lateral Flow Assay (LFA): TSA56 antigen is immobilized on nitrocellulose membrane test line(s). Patient IgM and/or IgG antibodies (from serum or whole blood) bind the antigen; secondary anti-human IgM/IgG-colloidal gold conjugate generates the visible test line. Results in 15–20 minutes. ELISA: TSA56 coats plate wells; indirect IgM/IgG ELISA with anti-human IgM/IgG-HRP readout. The same antigen supports both formats. Contact info@sekbio.com for membrane striping concentrations, ELISA coating optimization, and LFA development technical support.
O. tsutsugamushi TSA56 shows 40–80% sequence diversity across strains. Sekbio's antigen is designed for broad multi-strain coverage targeting strains prevalent in key Asian markets: Karp (Southeast Asia, Australia — dominant worldwide), Boryong (South Korea, China), TA716 (Taiwan), Gilliam (Japan). Perfect cross-strain sensitivity is not achievable with a single strain antigen; multi-strain or mosaic antigen formulations provide the broadest coverage. Contact info@sekbio.com for strain-specific sensitivity data and antigen formulation options optimized for your target geographic markets.
Standard sample type: serum or plasma (for highest antibody concentration and lowest matrix interference in LFA). Whole blood (fingerstick or venipuncture with lysis buffer): accepted in most commercial scrub typhus rapid tests, allowing point-of-care use without centrifuge. Sample volume: typically 5–10 μL serum/plasma or 20–30 μL whole blood. IgM is detectable from approximately day 7–10 post-fever onset. Testing before day 7 may yield false-negative results; repeat testing 5–7 days later if clinical suspicion remains high. Combined IgM+IgG tests provide broader diagnostic window for late presenters (week 2+ of illness).
Contact info@sekbio.com for scrub typhus recombinant antigen MOQ, concentration, purity data, format (lyophilized or liquid), pricing, and OEM supply terms. Sekbio's ISO 13485 certification supports regulatory documentation for CE marking, NMPA, KFDA (South Korea), CDSCO (India), and other Asian regulatory submissions. We serve IVD manufacturers developing scrub typhus rapid tests for the Indian, Southeast Asian, South Korean, and Chinese markets — as well as global manufacturers developing test kits for military medicine and expedition medicine applications.
Request scrub typhus recombinant antigen (TSA56) specification sheet, or discuss OEM supply for LFA and ELISA scrub typhus IVD kit development.