Preparation of antibodies directed to the Babesia ovata- or Theileria sergenti-parasitized erythrocytes

Molecular survey of Babesia microti, Ehrlichia species and Candidatus neoehrlichia mikurensis in wild rodents from Shimane Prefecture, Japan

A significant number of patients are diagnosed with "fevers of unknown origin" (FUO) in Shimane Prefecture in Japan where tick-borne diseases are endemic. We conducted molecular surveys for Babesia microti, Ehrlichia species, and Candidatus Neoehrlichia mikurensis in 62 FUO cases and 62 wild rodents from Shimane Prefecture, Japan. PCR using primers specific for the Babesia 18S small-subunit rRNA (rDNA) gene and Anaplasmataceae groESL amplified products from 45% (28/62) and 25.8% (16/62) of captured mice, respectively. Of the 28 18S rDNA PCR positives, 23 and five samples were positive for Hobetsu- and Kobe-type B. microti, respectively. In contrast, of the 16 groESL PCR positives, eight, one and seven samples were positive for Ehrlichia muris, Ehrlichia sp. HF565 and Candidatus N. mikurensis, respectively. Inoculation of selected blood samples into Golden Syrian hamsters indicated the presence of Hobetsu- and Kobe-type B. microti in four and one sample, respectively. Isolation of the latter strain was considered important as previous studies suggested that the distribution of this type was so far confined to Awaji Island in Hyogo Prefecture, where the first case of transfusion-associated human babesiosis originated. DNA samples from 62 FUO human cases tested negative for B. microti 18S rDNA gene, Anaplasmataceae groESL gene, Rickettsia japonica 17K genus-common antigen gene and Orientia tsutsugamushi 56K antigen gene by PCRs. We also conducted seroepidemiological surveys on 62 human sera collected in Shimane Prefecture from the FUO patients who were suspected of carrying tick-borne diseases. However, indirect immunofluorescent antibody tests using B. microti- and E. muris-infected cells detected IgG against E. muris in only a single positive sample. This study demonstrates the presence of several potentially important tick-borne pathogens in Shimane Prefecture and suggests the need for further study on the causative agents of FUOs.

Identification of a piroplasm protein of Theileria orientalis that binds to bovine erythrocyte band 3

Theileria orientalis infects cattle and causes various disease symptoms, including anaemia and icterus. The erythrocytic stages are responsible for these symptoms but the molecular events involved in these stages have not yet been fully elucidated. In this study, we identified a T. orientalis cDNA that encodes a polypeptide related to identity to the microneme-rhoptry protein of Theileria parva. Analysis of its recombinant product (ToMRP) by indirect fluorescent-antibody test revealed that it is specifically expressed at the early erythrocytic stage after invasion. This expression disappears during the intermediate stages of intra-erythrocytic development. Its expression then reappears at the late stages after the parasite has divided by binary fission into diad or tetrad forms and before these forms are released from the host erythrocyte. In vitro erythrocyte binding assays showed that ToMRP associates with the Triton X-insoluble fraction of erythrocytes membrane but not with intact erythrocytes. Cosedimentation and Western blot analyses revealed that ToMRP binds to band 3, a membrane component of bovine erythrocytes. These observations suggest that ToMRP may be involved in the parasite's egress from and/or invasion into the host erythrocytes by interacting with a protein in the membrane skeleton of the erythrocyte and thereby modifying the structure and function of the cell.

Accelerated Binding of Autoantibody to Red Blood Cells with Increasing Anaemia in Cattle Experimentally Infected with Theileria sergenti

Anaemia is the most important clinical manifestation in cattle infected with Theileria sergenti. In order to determine the mechanism of red blood cells (RBC) destruction in anaemic cattle, we studied the binding of autoantibody (IgG) to RBC during the development of anaemia in T. sergenti infection. The low levels of IgG-bound RBC before the development of anaemia were triggered in proportion with the progression of anaemia and parasitaemia. Our results suggest an accelerated destruction of RBC in anaemic cattle by IgG-dependent phagocytosis.