Gray foxes (Urocyon cinereoargenteus) as a potential reservoir of a Bartonella clarridgeiae-like bacterium and domestic dogs as part of a sentinel system for surveillance of zoonotic arthropod-borne pathogens in northern California

Two species of Bartonella, a novel Bartonella clarridgeiae-like bacterium and B. vinsonii subsp. berkhoffii, were isolated from rural dogs and gray foxes in northern California. A novel B. clarridgeiae-like species was isolated from 3 (1.7%) of 182 dogs and 22 (42%) of 53 gray foxes, while B. vinsonii subsp. berkhoffii was isolated from 1 dog (0.5%) and 5 gray foxes (9.4%). PCR and DNA sequence analyses of the citrate synthase (gltA) gene and the 16S-23S intergenic spacer region suggested that strains infecting dogs and gray foxes were identical. Fifty-four dogs (29%) and 48 gray foxes (89%) had reciprocal titers of antibodies against Bartonella spp. of > or =64. The high prevalence of bacteremia and seroreactivity to Bartonella spp. in gray foxes suggests that they may act as a reservoir species for the B. clarridgeiae-like species in this region. Domestic dogs were also tested for other arthropod-borne infectious agents. Fifty-one dogs (28%) were positive for Dirofilaria immitis antigen, seventy-four (40%) were seroreactive to Anaplasma phagocytophilum, and five (2.7%) were seropositive for Yersinia pestis. Fourteen dogs (7.6%) were PCR positive for A. phagocytophilum. Polytomous logistic regression models were used to assess the association of Bartonella antibody titer categories with potential risk factors and the presence of other vector-borne agents in domestic dogs. Older dogs were more likely to be seroreactive to Bartonella spp. There was no association between the exposure of dogs to Bartonella and the exposure of dogs to A. phagocytophilum in this study.     

Characterization and quantitation of the circulating forms of serum transferrin receptor using domain-specific antibodies

To characterize the nature of the immunoreactive transferrin receptor in human serum, antisera were developed to peptide sequences of the extracellular domain of human transferrin receptor between amino acids 107 and 120 and the intracellular domain between amino acids 40 and 54. Antisera against the extracellular domain exhibited reactivity against both purified intact receptor and immunopurified circulating receptor, whereas antisera against the intracellular domain reacted only with intact receptor. Using competitive binding enzyme-linked immunosorbent assays, transferrin receptor in ultracentrifuged sera from normal subjects and patients with sickle cell anemia could be detected with antisera against the extracellular but not the intracellular domain. When the pellet obtained by ultracentrifugation of these sera was assayed after solubilization in 1% teric (polyoxyethylene-9-lauryl ether), only 0.6% of total serum receptor was detected in normal subjects and 3.8% in subjects with sickle cell disease. Roughly equal amounts of this pelleted immunoactivity were detected with antibodies against the extracellular and intracellular domains. These results indicate that less than 1% of transferrin receptor in normal human sera is intact receptor consistent with an exosomal origin and that virtually all circulating transferrin receptor is in the form of a truncated extracellular domain.