Peri-articular histiocytic sarcoma and synovial cell sarcoma in Bernese Mountain dogs : a retrospective investigation of the prevalence of these tumours in association with previously diseased joints

C

Corpus Christi HTC

The human pancarcinoma-associated epithelial cell adhesion molecule (EpCAM) (EGP-2, CO17-1A) is a well-known target for carcinoma-directed immunotherapy. Mouse-derived mAbs directed to EpCAM have been used to treat colon carcinoma patients showing well-tolerable toxic side effects but limited antitumor effects. Humanized or fully human anti-EpCAM mAbs may induce stronger antitumor activity, but proved to produce severe pancreatitis upon use in patients. To evaluate treatment-associated effects before a clinical trial, we have generated a transgenic mouse tumor model that expresses human EpCAM similar to carcinoma patients. In this study, we use this model to study the in vivo behavior of two humanized and one mouse-derived anti-EpCAM mAb, i.e., MOC31-hFc, UBS54, and MOC31. The pharmacokinetics and tissue distribution of the fully human mAb UBS54 and the mouse-derived MOC31 were largely the same after injection in tumor-bearing transgenic mice, whereas the molecularly engineered, humanized MOC31-hFc behaved differently. Injection of UBS54 and MOC31 resulted in significant, dose-dependent uptake of mAb in EpCA.M-expressing normal and tumor tissues, accompanied by a drop in serum level, whereas injection of MOC31-hFc resulted in uptake in tumor tissue, limited uptake by normal tissues, and slow blood clearance. It is concluded that the EpCAM-transgenic mouse model provides valuable insights into the potential behavior of humanized antiEpCAM mAbs in patients. mAbs sharing the same epitope and isotype but constructed differently were shown to behave differently in the model, indicating that the design of mAbs is important for eventual success in in vivo application

Central role of complement in passive protection by human IgG1 and IgG2 anti-pneumococcal antibodies in mice

Streptococcus pneumoniae is an important cause of morbitity and mortality worldwide. Capsule-specific IgG1 and IgG2 Abs are induced upon vaccination with polysaccharide-based vaccines that mediate host protection. We compared the protective capacity of human recombinant serogroup 6-specific IgG1 and IgG2 Abs in mice deficient for either leukocyte FcR or complement factors. Human IgG1 was found to interact with mouse leukocyte FcR in vitro, whereas human IgG2 did not. Both subclasses induced complement activation, resulting in C3c deposition on pneumococcal surfaces. Passive immunization of C57BL/6 mice with either subclass before intranasal challenge with serotype 6A induced similar degrees of protection. FcgammaRI- and III-deficient mice, as well as the combined FcgammaRI, II, and III knockout mice, were protected by passive immunization, indicating FcR not to be essential for protection. C1q or C2/factor B knockout mice, however, were not protected by passive immunization. Passively immunized C2/factor B(-/-) mice displayed higher bacteremic load than C1q(-/-) mice, supporting an important protective role of the alternative complement pathway. Spleens from wild-type and C1q(-/-) mice showed hyperemia and thrombotic vessel occlusion, as a result of septicemic shock. Notably, thrombus formation was absent in spleens of C2/factor B(-/-) mice, suggesting that the alternative complement pathway contributes to shock-induced intravascular coagulation. These studies demonstrate complement to play a central role in Ab-mediated protection against pneumococcal infection in vivo, as well as in bacteremia-associated thrombotic complication

Author Correction: EMPReSS: standardized phenotype screens for functional annotation of the mouse genome

International audienceCorrection to: Nature Genetics, published online 1 November 2005.In the version of this article initially published, members of the Eumorphia Consortium appeared in the Supplementary Information but were not included in the main article. The full list of members appears below