Serological responses to Ehrlichia equi, Ehrlichia chaffeensis, and Borrelia burgdorferi in patients from New York State

Abstract

Serological testing at the New York State Department of Health for human granulocytic ehrlichiosis in the residents of Westchester County, N.Y., was performed with specimens from 176 patients by the indirect fluorescent-antibody (IFA) technique with Ehrlichia equi MRK-infected neutrophils. To understand whether human monocytotropic ehrlichiosis also occurs in this northeastern geographic region, specimens were also tested for antibodies to Ehrlichia chaffeensis Arkansas. Screening tests and immunoblots for Lyme disease (Borrelia burgdorferi infection) were also performed. Thirty-two patients had antibodies only to E. equi and 21 patients had antibodies to both E. equi and E. chaffeensis, whereas 12 patients had only E. chaffeensis antibodies by the IFA technique. The remaining patients did not have antibodies to either ehrlichia. Eighteen serum samples from 13 of these patients were coded and sent to the Ehrlichia Research Laboratory (Baltimore, Md.) for repeat analysis by the IFA test and for E. equi and E. chaffeensis immunoblots. Immunoblot analysis for E. equi in samples with positive IFA test results confirmed the results for eight of the nine specimens. Immunoblot analyses for E. chaffeensis were negative for all 18 serum samples. Borrelia-reactive antibodies were found in sera both from patients with granulocytic ehrlichiosis and from patients with monocytotropic ehrlichiosis from New York State. Our results suggest that E. equi antigen is an appropriate substrate for identifying human granulocytic ehrlichiosis. E. chaffeensis antigen lacks appropriate sensitivity to serve as a surrogate substrate for the detection of human granulocytic ehrlichiosis and should be used solely for the diagnosis of human monocytotropic ehrlichiosis. Heat shock proteins may, in some cases, cause cross-reactivity between B. burgdorferi and ehrlichiae.

Seroprevalence of Ehrlichia canis, Ehrlichia equi, and Ehrlichia risticii in Sick Dogs from North Carolina and Virginia

“…Therefore, sole recognition of 28-kDa antigens may reflect sample collection during acute infection or the diminished antibody response expected with immunogenic recovery or after therapeutic elimination of the organism. 33 Failure of E chaffeensis-reactive sera, obtained from 2 dogs infected experimentally with E chaffeensis, to recognize the 28-kDa E canis antigens by WI was unexpected and may indicate that strain variation contributes to differences in serologic cross-reactivity among isolates within a genogroup when the source of antigen is obtained from different geographic regions. Although it is impractical to test sera derived from dogs with all known infectious diseases, without such testing it is impossible to rule out cross-reactivity to E canis 28-kDa immunodominant antigens.…”

“…28 Similarly, detection of the 44-kDa E equi antigen was proposed as being diagnostically useful after testing E equi antisera from humans. 33 Recognition of the 44-kDa antigen in conjunction with other distinct proteins of 80, 105, and 120 kDa was proposed as a criterion when sera from dogs naturally infected with E equi were tested against a strain Ehrlichia that causes human granulocytic ehrlichiosis in the northeastern USA. 18 In an earlier study, 13-, 16-, 23-, 25-, and 45-kDa proteins were detected when E equi antisera from dogs was reacted with E equi antigen.…”

“…These sera recognized E equi antigens in the exact same pattern as E equi control sera (31,32,34,35,39, 40, 42-44 triplet, and 55 kDa), suggesting that these 2 sera were from dogs exposed to E equi. Collectively, serologic and molecular data indicate that although E equi exposure presumably is infrequent, the potential for infection in horses, dogs, 2,18 cats, 34 and, potentially, humans 33,35 (E equi is generally accepted as the cause of human granulocytic ehrlichiosis) exists in the southeastern USA.…”

Human Exposure to Anaplasma phagocytophilum in Portugal

“…Antibodies against A. phagocytophilum were detected by indirect immunofluorescence (IFA) and Western blot (WB) assays, as described previously. 3,4 A. phagocytophilum Webster and Ehrlichia chaffeensis Arkansas strains were used as antigen. E. chaffeensis cross-reactivity was evaluated in seropositive samples.…”

“…The criteria for seropositivity were IFA titer ≥80 and WB reactivity with bands between 42-49 kDa for A. phagocytophilum and between 23-30 kDa for E. chaffeensis. 3,4 Confirmed A. phagocytophilum exposure was defined as a fourfold higher IFA titer to specific antigen than to E. chaffeensis or when IFA and WB were positive. Possible exposure was defined as a single IFA titer of ≥80 or less than fourfold titer difference between specific antigen and E. chaffeensis, and no specific WB bands.…”