Search

The need for improved diagnostic reagents to identify human long-term carriers of the zoonotic parasite Babesia microti is evidenced by numerous reported cases of transfusion-acquired infections. This report describes the identification and initial characterization of 27 clones representing seven genes or gene families that were isolated through serological expression cloning by using a technique that we specifically designed to screen for shed antigens. In this screen, sera from B. microti-infected SCID mice, putatively containing secreted or shed antigens from the parasites, were harvested and used to immunize syngeneic immunocompetent mice (BALB/c). After boosting, the sera from the BALB/c mice, containing antibodies against the immunodominant secreted antigens, were used to screen a B. microti genomic expression library. Analyses of the putative peptides encoded by the novel DNA sequences revealed characteristics indicating that these peptides might be secreted. Initial serological data obtained with recombinant proteins and a patient serum panel demonstrated that several of the proteins could be useful in developing diagnostic tests for detection of B. microti antibodies and antigens in serum.

Background: Tick-borne diseases, particularly babesiosis and ehrlichiosis, represent recently emerging infections. Despite an increased recognition of the threat tick-borne agents pose to blood safety, our understanding of the prevalence and transmissibility of these agents in blood donors is limited., Study Design and Methods: Babesia microti and Anaplasma phagocytophila (previously Ehrlichia sp.) seroprevalence was determined in random Connecticut and Wisconsin donors, and subsequently in Connecticut donors reporting tick bites. In the interim, a postcard survey regarding tick bites during the previous 6 months was sent to 6,000 random donors in six geographically distinct collection regions., Results: In total, 3 of 999 Wisconsin donors (0.3%) and 6 of 1,007 Connecticut donors (0.6%) had antibodies to B. microti. Of 992 donors tested for A. phagocytophila, 5 Wisconsin donors (0.5%) and 35 Connecticut donors (3.5%) were seropositive. A total of 2,482 donors (41.4%) completed the survey; 103 (4.1%) reported a tick bite. Of 848 Connecticut donors (0.4%) reporting tick bites, 3 had B. microti antibodies, while 8 (0.9%) had A. phagocytophila antibodies. These rates were not significantly different from control donors., Conclusion: Blood donors seropositive for B. microti and A. phagocytophila are present in Connecticut and Wisconsin. Donors readily recall previous tick bites, but self-reported bites are not reliable indicators of serologic status. The exposure of blood donors to tick-borne pathogens does suggest a need to better understand the transfusion transmission potential of these agents.

Background: Babesia microti is a tick-borne agent that is increasingly implicated in transfusion-acquired infection, especially in immunocompromised and elderly recipients. To develop a test that can detect antibody responses to B. microti, peptide epitopes identified in two serocomplementary B. microti-specific antigens were used in a prototype EIA., Study Design and Methods: A prototype peptide EIA was used to detect B. microti-specific antibodies in 15 sera taken before infection and 107 taken after infection from 59 individuals with known tick-borne infections previously confirmed by other methods. Three additional groups of samples were also tested: a proficiency panel of 18 sera positive for B. microti by IFA, 38 sera from blood donors confirmed positive by IFA, and 30 sera from random blood donors., Results: The combination peptide detected 98 out of 107 sera taken after infection that were IgG blot positive (4 equivocal). This included all 12 samples that were PCR positive and six sera from smear-negative patients that were confirmed positive by PCR, immunoblot, or IFA. Of the IgG blot-positive specimens that were equivocal (four specimens) or did not react (nine specimens) by EIA, most had low IFA titers consistent with previous exposure. In a second evaluation, 15 out of 15 Babesia IFA-positive sera and 3 out of 3 Babesia-Ehrlichia IFA-positive sera were positive, whereas sera from 30 random donors were negative. Finally, of 38 IFA-positive blood-donor samples, 35 were positive by peptide EIA. The three EIA-negative sera were Western blot negative., Conclusion: Reactivity of the B. microti-specific peptide EIA shows a high correlation with IFA, PCR, and B. microti immunoblot in confirmed B. microti cases. The peptide EIA may be the most suitable B. microti infection test for adaptation to the blood bank environment if testing for B. microti is required in the future.