Kinetics of Serological Response in Patients with Severe Fever with Thrombocytopenia Syndrome

Abstract

Severe fever with thrombocytopenia syndrome (SFTS) is caused by SFTS virus (SFTSV). We investigated the detailed kinetics of serologic response in patients with SFTS. Twenty-eight patients aged ≥18 years were enrolled between July 2015 and October 2018. SFTS was confirmed by detecting SFTSV RNA in their plasma using reverse transcription polymerase chain reaction. SFTSV-specific IgG and IgM were measured using immunofluorescence assay (IFA) and enzyme-linked immunosorbent assay (ELISA). We found that SFTSV-specific IgG was detected at days 5–9 after symptom onset, and its titer was rising during the course of disease. SFTSV-specific IgM titer peaked at around week 2–3 from symptom onset. The SFTSV-specific seropositive rates for days 5–9, 10–14, 15–19, and 20–24 from symptom onset using IFA and ELISA were 63%, 76%, 90%, and 100%, and 58%, 86%, 100%, and 100%, respectively, for IgG, whereas they were 32%, 62%, 80%, and 100%, and 53%, 62%, 70%, and 100%, respectively, for IgM. The delayed IgM response could be attributed to the low sensitivity of SFTSV-specific IgM IFA or ELISA and/or impaired immune responses. The IgM test using IFA or ELISA that we used in this study is, therefore, insufficient for the early diagnosis of SFTS.

Multisystem inflammatory syndrome in adults after acute coronavirus disease 2019 in a Japanese woman: A case report

“…Lastly, the results of serologic testing of paired samples, including convalescent sera taken nearly 1 month after symptom onset, showed low IgG and IgM titers for SFTS virus. In SFTS patients diagnosed by RT-PCR including immunocompromised patients, the seropositive rates for IgG or IgM reached 100% two or three weeks after symptom onset [ 12 ].…”

Serological Evidence of Severe Fever with Thrombocytopenia Syndrome Virus and IgM Positivity Were Identified in Healthy Residents in Vietnam

“…Serological testing for the presence of anti-SFTSV IgM and IgG was performed using IFA assay as previously described [ 2 , 6 ].…”

“…The major clinical symptoms of severe fever with thrombocytopenia syndrome (SFTS) are acute and high fever (temperatures of 38 °C or more), thrombocytopenia (platelet count < 100,000/mm 3 ), leucopenia, elevated levels of serum hepatic enzymes, gastrointestinal symptoms and multiorgan failure, with a 16.2 to 30% mortality rate, and effective antiviral therapy for SFTS virus (SFTSV) has not been available [ 1 , 4 , 5 , 6 ].…”

Clinical Update of Severe Fever with Thrombocytopenia Syndrome

“…IFA or an enzyme-linked immunosorbent assay (ELISA) are effective diagnostic methods for detecting viral-specific IgM and IgG in the serum 7 days after the onset of the disease; SFTS is diagnosed upon detection of IgM antibodies, observation of IgG antibody seroconversion, or at least a four-fold increase in antibody titer [ 64 ]. However, the IFA sensitivities for IgM and IgG detection within 2 weeks after the onset of symptoms are 32–62% and 63–76%, respectively; the IFA sensitivities of ELISA are 53–62% and 58–86%, respectively [ 85 ]. Therefore, IFA or ELISA may be insufficient for early SFTS diagnosis.…”