Identification of Babesia microti-specific immunodominant epitopes and development of a peptide EIA for detection of antibodies in serum.
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.


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.


CONCLUSIONS
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.
Houghton
Raymond L
RL
Department of Antigen Discovery, Corixa Corporation, Seattle, Washington 98104, USA. houghton@corixa.com
Homer
Mary J
MJ
Reynolds
Lisa D
LD
Sleath
Paul R
PR
Lodes
Michael J
MJ
Berardi
Victor
V
Leiby
David A
DA
Persing
David H
DH
D000595:Amino Acid Sequence; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood* / Q000276:immunology; D000918:Antibody Specificity; D000953:Antigens, Protozoan / Q000032:analysis / Q000276:immunology*; D041001:Babesia microti / Q000276:immunology*; D001404:Babesiosis / Q000097:blood* / Q000175:diagnosis; D001771:Blood Banks; D001782:Blood Donors; D004797:Enzyme-Linked Immunosorbent Assay; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D015151:Immunoblotting; D016056:Immunodominant Epitopes / Q000032:analysis / Q000276:immunology*; D007124:Immunoenzyme Techniques; D007074:Immunoglobulin G / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D008403:Mass Screening; D008969:Molecular Sequence Data; D018512:Parasitemia / Q000097:blood* / Q000175:diagnosis; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000276:immunology
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D016056:Immunodominant Epitopes; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D011994:Recombinant Proteins