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

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.

Comparison of Commercial Enzyme-Linked Immunosorbent Assay and Immunofluorescence Assay for Diagnosis of Acute Rickettsia typhi Infections

Murine typhus is a tropical disease caused by Rickettsia typhi and is endemic in resource-limited settings such as Southeast Asian countries. Early diagnosis of R. typhi infection facilitates appropriate management and reduces the risk of severe disease. However, molecular detection of R. typhi in blood is insensitive due to low rickettsemia. Furthermore, the gold standard of sero-diagnosis by immunofluorescence assay (IFA) is cumbersome, subjective, impractical, and unavailable in many endemic areas. In an attempt to identify a practical diagnostic approach that can be applied in Indonesia, we evaluated the performance of commercial R. typhi IgM and IgG enzyme-linked immunosorbent assay (ELISA) and IFA using paired plasma from previously studied R. typhi PCR-positive cases and controls with other known infections. Sensitivity and specificity of combined ELISA IgM and IgG anti-R. typhi using paired specimens were excellent (95.0% and 98.3%, respectively), comparable to combined IFA IgM and IgG (97.5% and 100%, respectively); sensitivity of ELISA IgM from acute specimens only was poor (45.0%), but specificity was excellent (98.3%). IFA IgM was more sensitive (77.5%), but less specific (89.7%) for single specimens.

Clinical Significance of Anti-Ribosomal P Protein Antibodies in Patients with Lupus Nephritis

BACKGROUND

Systemic Lupus Erythematosus (SLE) is a chronic inflammatory disorder affecting multiple systems of the body. Clinical features show wide variations in patients with the different ethnic background. Renal involvement is a predictor of poor prognosis. Immunological workup is an integral part of SLE diagnostic criteria. Anti-ribosomal P Protein (anti-P) antibodies are highly specific for SLE. They may be present in Antinuclear Antibodies (ANA) negative SLE patients. Their role in Lupus Nephritis (LN) is under debate, some researchers found them associated with poor prognosis whereas others found favorable effect of these antibodies on renal disease.

OBJECTIVE

In this study, we investigated frequency of anti-P antibodies and the effect of these antibodies on renal functions in the LN patients.

METHODS

A total of 133 SLE patients were enrolled in this study. All patients had ANA in their sera. Anti-P antibodies along with other autoantibodies against extractable nuclear antigens (anti-Sm, anti- SS-A, anti-SS-B, anti-histones and anti-RNP) were detected by Immunoblot assay. Anti-dsDNA antibodies were detected by indirect Immunofluorescence Assay (IFA).

RESULTS

We found anti-P antibodies in 10.5% LN patients. Interestingly their presence in association with anti-dsDNA was associated with improved renal functions in comparison to those who had antidsDNA antibodies in isolation (serum creatinine: 1.3 ± 0.8 mg/dl vs. 3.0 ± 3.0; P= 0.091).

CONCLUSION

Anti-dsDNA antibodies are directly involved in renal pathology in SLE patients. As these antibodies are nephrotoxic, concomitant occurrence of anti-P antibodies seems to offer a shielding effect on renal functions, which was evident by normal serum creatinine levels. Therefore, anti-P antibodies may be considered as a good prognostic marker in these patients.