Faculty Bibliography

Obesity is associated with an increased colon cancer incidence, but underlying mechanisms remained unclear. Previous studies showed altered Natural killer (NK) cell functions in obese individuals. Therefore, we studied the impact of an impaired NK cell functionality on the increased colon cancer risk in obesity. In vitro investigations demonstrated a decreased IFN-γ secretion and cytotoxicity of human NK cells against colon tumor cells after NK cell preincubation with the adipokine leptin. In addition, leptin incubation decreased the expression of activating NK cell receptors. In animal studies, colon cancer growth was induced by injection of azoxymethane (AOM) in normal weight and diet-induced obese rats. Body weight and visceral fat mass were increased in obese animals compared to normal weight rats. AOM-treated obese rats showed an increased quantity, size, and weight of colon tumors compared to the normal weight tumor group. Immunohistochemical analyses demonstrated a decreased number of NK cells in spleen and liver in obesity. Additionally, the expression levels of activating NK cell receptors were lower in spleen and liver of obese rats. The results show for the first time that the decreased number and impaired NK cell function may be one cause for the higher colon cancer risk in obesity.

The sensitivity of a K39 ELISA (Leishmania IgG, Virion/Serion) for the detection of antibodies in patients with imported leishmaniasis was compared with an immunofluorescence assay (IFA), which was applied as "golden standard". The retrospective study comprised 93 IFA-positive or borderline sera from 42 patients with visceral (n = 16) or cutaneous (n = 26) leishmaniasis. Patients had acquired infection predominately in the Mediterranean area or the Middle East. The Leishmania species (Leishmania donovani/infantum, Leishmania tropica, Leishmania major) were identified by real-time PCR. The majority (94%) of first samples from patients with visceral leishmaniasis (VL) tested positive by K39 ELISA. Antibody levels ranged from low to very high (33.19-1990.00 U/ml; median 596.66 U/ml) but did not correlate with the respective IFA titers. High K39 ELISA values correlated with acute infection in immunocompetent individuals. K39 antibodies declined in all individuals after clinically successful therapy, but time to seronegativity varied considerably (51 weeks to >6 years). In patients with cutaneous leishmaniasis (CL), the sensitivity of the K39 ELISA was low (23%) compared to IFA (92% positive). Antibody levels ranged from low to medium (10.85-524.77 U/ml; median 19.77 U/ml). The highest antibody concentrations were seen in L. infantum-infected individuals. Summarizing, a high K39 ELISA value indicates active VL. The assay is, like IFA, not a measure for effective therapy but may support post-treatment monitoring. Low level positivity can indicate subclinical, previous or clinically cured VL or even CL. The K39 ELISA can supplement highly sensitive screening tests in the diagnosis and follow-up of imported leishmaniasis.

BACKGROUND:Aspergillus fumigatus is a common airborne fungal pathogen for humans. It frequently causes an invasive aspergillosis (IA) in immunocompromised patients with poor prognosis. Potent antifungal drugs are very expensive and cause serious adverse effects. Their correct application requires an early and specific diagnosis of IA, which is still not properly achievable. This work aims to a specific detection of A. fumigatus by immunofluorescence and the generation of recombinant antibodies for the detection of A. fumigatus by ELISA. RESULTS:The A. fumigatus antigen Crf2 was isolated from a human patient with proven IA. It is a novel variant of a group of surface proteins (Crf1, Asp f9, Asp f16) which belong to the glycosylhydrolase family. Single chain fragment variables (scFvs) were obtained by phage display from a human naive antibody gene library and an immune antibody gene library generated from a macaque immunized with recombinant Crf2. Two different selection strategies were performed and shown to influence the selection of scFvs recognizing the Crf2 antigen in its native conformation. Using these antibodies, Crf2 was localized in growing hyphae of A. fumigatus but not in spores. In addition, the antibodies allowed differentiation between A. fumigatus and related Aspergillus species or Candida albicans by immunofluorescence microscopy. The scFv antibody clones were further characterized for their affinity, the nature of their epitope, their serum stability and their detection limit of Crf2 in human serum. CONCLUSION/CONCLUSIONS:Crf2 and the corresponding recombinant antibodies offer a novel approach for the early diagnostics of IA caused by A. fumigatus.