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. 2018 Jul 5;3(3):74.
doi: 10.3390/tropicalmed3030074.

Serological Cross-Reactivity among Orientia tsutsugamushi Serotypes but Not with Rickettsia japonica in Japan

Eiichiro Sando  1   2   3 , Koya Ariyoshi  4   5 , Hiromi Fujita  6
Affiliations

Serological Cross-Reactivity among Orientia tsutsugamushi Serotypes but Not with Rickettsia japonica in Japan

Eiichiro Sando et al. Trop Med Infect Dis. .

Erratum in

Abstract

The rickettsial diseases Japanese spotted fever (JSF) and scrub typhus (ST) are caused by Rickettsia japonica and Orientia tsutsugamushi, respectively. The diseases share clinical symptoms, such as fever, rash, and eschar. However, there are no systematical investigations of the serological cross-reactivity between R. japonica and O. tsutsugamushi. Also, the serological cross-reactivity among O. tsutsugamushi serotypes is still unclear. We analyzed 1406 cases tested by indirect immunoperoxidase assay using seven rickettsial antigens-one R. japonica and six O. tsutsugamushi serotypes-between 2003 and 2016 at two reference centers in Japan. Of these, 167 JSF and 190 ST cases were serologically diagnosed. None of the ST cases had a significant increase in IgM titers against R. japonica. Six JSF cases showed IgG titers of ≥40 against O. tsutsugamushi, but no IgG titer showed a significant elevation in the convalescent phase sample. We observed a substantial degree of cross-reactivity between O. tsutsugamushi serotypes. Cross-reactivity was significant among Karp, Hirano/Kuroki, and Kato types and between Gilliam and Irie/Kawasaki types in IgM, while the Shimokoshi type was less cross-reactive than the others. In conclusion, there is no serological cross-reaction between R. japonica and O. tsutsugamushi. The cross-reactivity among O.tsutsugamushi varies depending on serotypes.

Keywords: Japanese spotted fever; Orientia tsutsugamushi; Rickettsia japonica; scrub typhus; tsutsugamushi disease.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Serology results of cases of IgM/IgG against R. japonica and O. tsutsugamushi. The titer of IgM/IgG against R. japonica and the maximum titer of 6 serotypes against O. tsutsugamushi in Japanese spotted fever (a) and scrub typhus (b) are shown in acute and convalescent-phase samples. Abbreviations: Irie, Irie/Kawasaki; Hirano, Hirano/Kuroki.
Figure 1
Figure 1
Serology results of cases of IgM/IgG against R. japonica and O. tsutsugamushi. The titer of IgM/IgG against R. japonica and the maximum titer of 6 serotypes against O. tsutsugamushi in Japanese spotted fever (a) and scrub typhus (b) are shown in acute and convalescent-phase samples. Abbreviations: Irie, Irie/Kawasaki; Hirano, Hirano/Kuroki.
Figure 2
Figure 2
Spearman’s rank correlation coefficients between each O. tsutsugamushi serotype. The correlation coefficients in IgM (a) and IgG (b) samples were calculated using titers when a diagnosis of scrub typhus was made (n = 190): paired samples, n = 138; single sample, n = 52. Abbreviations: Irie, Irie/Kawasaki; Hirano, Hirano/Kuroki.
Figure 2
Figure 2
Spearman’s rank correlation coefficients between each O. tsutsugamushi serotype. The correlation coefficients in IgM (a) and IgG (b) samples were calculated using titers when a diagnosis of scrub typhus was made (n = 190): paired samples, n = 138; single sample, n = 52. Abbreviations: Irie, Irie/Kawasaki; Hirano, Hirano/Kuroki.
Figure 3
Figure 3
The number of cases serologically diagnosed as Japanese spotted fever or scrub typhus (serotypes) in each Japanese region at the reference centers. Abbreviation: JSF, Japanese spotted fever; ST, scrub typhus; Gl, Gilliam; Kr, Karp; Kt, Kato; Ir, Irie/Kawasaki; Hr, Hirano/Kuroki; Sh, Shimokoshi; NT, nontypeable; Ohara Institution, Ohara Research Laboratory, Ohara General Hospital; Mahara Institution, Mahara Institute of Medical Acarology.
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