The rP43 did not react with sera from laboratory-raised dogs, suggesting that the positive reactions with rP43 from these suspect canine ehrlichiosis cases were specific. macrophages (15) and establishes persistent infections in the vertebrate host (8). The disease caused by is characterized by three stages: the acute stage, which Boldenone Undecylenate lasts 2 to 4 weeks; the subclinical stage, in which dogs can remain persistently infected for years without exhibiting clinical signs; and ultimately the chronic phase, at which for many dogs the disease becomes progressively worse due to bone marrow hypoplasia and the prognosis is less favorable (21). Treating the disease in the acute phase is important for the best prognosis, but clinical presentation of canine ehrlichiosis is nonspecific, making diagnosis difficult. Hematologic abnormalities such as leukopenia and thrombocytopenia often provide useful evidence of canine ehrlichiosis and are important factors in the initial diagnosis (21). Diagnosis of canine ehrlichiosis by serologic methods such as the indirect fluorescent antibody (IFA) test has become the standard testing method due to its simplicity, reliability, and Boldenone Undecylenate cost-effectiveness Rabbit polyclonal to F10 (21). However, shortcomings of the IFA test are the inability to make a species-specific diagnosis due to antigenic cross-reactivity with other closely related species that infect dogs (and were reported to be more sensitive than cell culture isolation, but this method requires specialized training and expensive equipment (11). Isolation of the organism is time-consuming, and only a few laboratories have been consistently successful with this method. Furthermore, additional tests to characterize the isolate are required to define a specific etiology using this method. Serologically cross-reactive antigens shared between and have been reported. Some of the major serologically cross-reactive proteins exhibit molecular masses of 28 to 30 kDa (2, 18), and it is now known that these proteins are encoded by homologous multigene families (16, 17). There are 21 and 5 homologous, but nonidentical, genes that have been identified and sequenced in and Boldenone Undecylenate and was an insensitive tool for diagnosing cases of human monocytotropic ehrlichiosis (HME) (27). The underlying reason appears to be the variability of the P28 protein among different strains of (29). Conversely, the P28 genes identified in are conserved among geographically dispersed strains in the United States (12, 13), and rP28 has proven to be useful for the diagnosis of canine ehrlichiosis (16). Other homologous immunoreactive proteins, including the glycoproteins P140 in and the P120 in has correlated well with the IFA test for the serodiagnosis of HME, and preliminary studies with the rP140 of suggest that it may be a sensitive and reliable immunodiagnostic antigen (27, 28). In this study we have cloned a new highly immunoreactive protein gene of 1 1,170 bp, which encodes a protein with a predicted molecular mass of 42.6 kDa (P43). The gene was not detected in DNA, and antibodies against the P43 did not react with antigen as determined by the IFA test. We compared previously described immunoreactive rP28 and rP140 proteins with the rP43 protein for the serodiagnosis of canine ehrlichiosis and found the rP43 and rP28 to be sensitive and reliable for the serologic diagnosis of infections in dogs and humans. The rP43-based assay or a molecular diagnostic assay using the gene would be especially useful for epidemiologic and clinical studies to examine specific ehrlichial diseases in dogs. MATERIALS AND METHODS Ehrlichiae and purification. Jake strain was isolated by Edward Breitschwerdt and Michael Levy (College of Veterinary Medicine, North Carolina State University, Raleigh, N.C.). The.