Transfusion-Acquired, Autochthonous Human Babesiosis in Japan: Isolation of Babesia microti -Like Parasites with hu-RBC-SCID Mice

Abstract

We have isolated piroplasms from a patient who developed the first case of human babesiosis in Japan by using NOD/shi-scidmice whose circulating erythrocytes (RBCs) had been replaced with human RBCs (hu-RBC-SCID mice). Following inoculation of the patient's blood specimen into hu-RBC-SCID mice, parasites proliferated within the human RBCs in the mice, resulting in a high level of parasitemia. Parasite DNA was prepared from blood samples of the patient and the mice, and the nuclear small-subunit rRNA gene (rDNA) was amplified and sequenced. Both DNA samples gave rise to identical sequences which showed the highest degree of homology (99.2%) with the Babesia microti rDNA. Because the patient had received a blood transfusion before the onset of babesiosis, we investigated the eight donors who were involved. Their archived blood samples were analyzed for specific antibody and parasite DNA; only a single donor was found to be positive by both tests, and the parasite rDNA sequence from the donor coincided with that derived from the patient. The donor's serum exhibited a high antibody titer against the isolate from the patient, whereas it exhibited only a weak cross-reaction against B. microti strains isolated in the United States. We conclude that the first Japanese babesiosis case occurred due to a blood transfusion and that the etiological agent is an indigenous Japanese parasite which may be a geographical variant of B. microti. Our results also demonstrated the usefulness of hu-RBC-SCID mice for isolation of parasites from humans and for maintenance of the parasite infectivity for human RBCs.

Transfusion-transmitted infections

“…Nevertheless, individuals returning to the U.S. from combat zones in Iraq are currently deferred for one year. Aside from parasites, other tick-borne agents such as the two bacteria Anaplasma phagocytophilum and Rickettsia rickettsii have been rarely found in blood products although most TT tick-borne infections have been largely confined to the Northeastern U.S. and one case of TT babesia infection in Japan [116,117].…”

Analysis of antigen‐antibody cross‐reactivity among lineages and sublineages of Babesia microti parasites using human babesiosis specimens

“…Previous studies reported that serum samples from an individual infected with a Kobe lineage organism showed strong reactivity to the Kobe lineage, but weak reactivity to the US and Hobetsu lineages. 17,21 Taken together, these observations indicate that B. microti antibody reacted specifically to homologous antigens among the sublineages of B. microti. Indirect immunofluorescence assay is a method used generally for antibody detection in human babesiosis around the world.…”

“…14 Kobe524 (Kobe lineage) was isolated from a blood sample of a TTB patient in Japan. 17,24 Ho234 (Hobetsu lineage) was isolated from a rodent in Japan. 21 The lineages and sublineages of the US lineage of the B. microti strains used were previously determined by phylogenetic analysis based on the sequences of B. microti 18S rRNA, b-tubulin, and CCTeta genes.…”

“…Besides those of the US lineage, cases of human babesiosis caused by the B. microti Kobe and Munich lineages have been reported in Japan and Spain, respectively. 17,18 Infection with various members of the B. microti group including US, Kobe, Munich, Hobetsu, B. microti-like (squirrel), and B. microti-like (macaque) have been observed in various animals, including rodents and nonhuman primates. [19][20][21][22] Any of these B. microti-group parasites might have the potential to cause babesiosis in humans.…”

“…19 However, it has been reported that the antigenicity of B. microti differs among its lineages. 17,21,24 Furthermore, animal sera have also shown low crossreactivity even among the sublineages in the US lineage. 14,25 These results suggest that the reactivity of antibodies for strict specificity among the B. microti group could be a concern in developing effective serologic detection methods for human babesiosis.…”