henselaeand its recognition as the main causative agent of CSD, the induction of a delayed-type hypersensitivity reaction, a hallmark of CMI, was used to diagnose CSD clinically (14)

henselaeand its recognition as the main causative agent of CSD, the induction of a delayed-type hypersensitivity reaction, a hallmark of CMI, was used to diagnose CSD clinically (14). Cats are considered the natural host ofB. contamination, peaked at 8 weeks postinfection, and decreased thereafter. Gamma interferon, but not interleukin-4, was produced in vitro by spleen cells from infected animals upon stimulation withBartonellaantigens.Bartonella-specific IgG was detectable in serum of infected mice by 2 weeks, and the antibody GPR40 Activator 1 concentration peaked at 12 weeks postinfection. IgG2b was the GPR40 Activator 1 prominent isotype among theBartonella-specific serum IgG antibodies. These data indicate thatB. henselaeinduces cell-mediated immune responses with a Th1 phenotype in immunocompetent C57BL/6 mice. Clinical presentation of GPR40 Activator 1 infections caused byBartonella henselaeranges from a relatively moderate lymphadenopathy with few additional symptoms, seen in cat scrape disease (CSD) in immunocompetent patients, to life-threatening systemic disease in immunocompromised individuals, such as bacillary angiomatosis and peliosis (BAP) associated with bacteremia and fever (2). Little is known about the pathogenesis ofB. henselaeinfections and the induced immune responses, mainly because of the lack of a suitable animal model. Several observations point to a crucial role of cell-mediated immunity (CMI) in the pathogenesis and control ofB. henselaeinfections. In human immunodeficiency computer virus (HIV)-infected patients with AIDS, the clinical manifestations of disease are more severe than the moderate and self-limiting course of contamination in immunocompetent patients. Recently, Mohle-Boetani et al. (19) reported that HIV-infected individuals with CD4+T-cell counts of <50 l1are at highest risk for developing BAP and suggested than BAP be considered an AIDS-defining opportunistic contamination. Also,B. henselaehas been shown to induce granuloma formation in experimentally infected animals (9,22) and in lymph nodes, spleens, and livers of human patients suffering from CSD (8,12,13,27), indicating the induction of CMI in immunocompetent hosts. In addition, in the era prior to detection ofB. henselaeand its recognition as the main causative agent of CSD, the induction of a delayed-type hypersensitivity reaction, a hallmark of CMI, was used to diagnose CSD clinically (14). Cats are considered the natural host ofB. henselaeand source of contamination for humans. There are few reports on experimental contamination of cats withB. henselae; however, the course of disease in cats differs from that in humans, and the results for clinical manifestations and histopathological findings are conflicting (7,9,11,21,23), possibly as a result of using differentB. henselaestrains and/or different mechanisms of inoculation. In addition, characterization of the induced immune responses has been difficult because of limitations of immunological tools in feline models. In contrast, murine contamination models have been shown to be often advantageous for immunological studies (16). In the present study, we used a murine model ofB. henselaeinfection established in our laboratory (22) to investigate the immune GPR40 Activator 1 responses induced in the immunocompetent host. Following intraperitoneal (i.p.) contamination of C57BL/6 mice withB. henselae, the cellular and humoral immune responses were analyzed at multiple time points until 20 weeks postinfection (p.i.). Proliferative responses were studied in vitro by means of a splenocyte proliferation assay. The functions of different T-cell subsets were investigated by administration of monoclonal antibodies (MAbs) to CD4 and CD8 T cells in proliferation assays. In cytokine release studies, Th cells involved in CMI againstB. henselaewere further characterized. Humoral immune responses were studied by enzyme-linked immunoassay (ELISA) forBartonella-specific immunoglobulin G (IgG) antibodies, and the IgG isotypes were determined. In addition, development and alterations of granulomatous lesions in livers of infected mice were monitored histologically. The present study demonstrates that a virulentB. henselaestrain is usually capable of inducing a long-lived inflammation of the liver and strong Th1 type immune responses in immunocompetent C57BL/6 mice. == MATERIALS AND METHODS == == Bacteria. == B. henselaestrain Berlin-1, which was originally isolated from the cutaneous bacillary angiomatosis lesions of an HIV-infected patient (4), was used throughout this study. The primary isolate was inoculated in brucella broth supplemented with 250 mg of hemin/liter and 8% Fildes (24), produced to a log-phase culture, and stored in aliquots at 70C. To prepare the inocula for the infection, aliquots were thawed and produced again to log-phase cultures in supplemented brucella broth, washed twice with phosphate-buffered saline (PBS), and resuspended in PBS to obtain a final concentration of (2 1) 108CFU/ml. One aliquot was plated in 10-fold serial dilutions on Columbia agar with 5% human blood to determine the colony count, and the remaining bacteria were used for inoculation of animals within 1 h after preparation. == Mice. == Female C57BL/6 mice raised in our breeding facilities were used at the age of 10 to 13 weeks. Animals were kept under specific-pathogen-free conditions (positive-pressure cabinet). == Contamination of animals. == Animals were injected i.p. with 1 108to 2 108CFU Cspg2 ofB. henselaein a volume of 1 ml of PBS or with 1 ml of PBS as a.