Isotype-specific resistance against tolerance induction in SJL mice

Age-related changes in antibody response of SJL mice were examined in terms of isotype expression after treatment with immunogen or with immunogen, preceded by the molecule in normally tolerogenic form. We report here that tolerance induction and resistance to down regulation are isotype specific. Tolerance can be induced in terms of all detectable isotypes at the age of 5 weeks. In older SJL mice, tolerance to the carrier is found in IgM antibody, whereas there is resistance against down regulation in terms of IgG2a and IgG2b isotypes, and sensitization in terms of IgG3, IgG1, and IgA antibody. Furthermore, the degree of down regulation is determinant dependent. This was observed when older SJL mice, pretreated with the carrier in a normally tolerogenic form, were immunized with haptenated carrier and tested for their response to hapten and carrier determinants. In this case, IgA antibody shows tolerance to the hapten and sensitization by carrier determinants.     

Vanucizumab mode of action: Serial biomarkers in plasma,tumor, and skin-wound-healing biopsies

Vanucizumab is a novel bispecific antibody inhibiting vascular endothelial growth factor (VEGF-A) and angiopoietin-2 (Ang-2) that demonstrated safety and anti-tumor activity in part I of a phase I study of 42 patients with advanced solid tumors. Part II evaluated the pharmacodynamic effects of vanucizumab 30 or 15 mg/kg every 2 weeks in 32 patients. Serial plasma samples, paired tumor, and skin-wound-healing biopsies were taken over 29 days to evaluate angiogenic markers. Vanucizumab was associated with marked post-infusion reductions in circulating unbound VEGF-A and Ang-2. By day 29, tumor samples revealed mean reductions in density of microvessels (−32.2%), proliferating vessels (−47.9%) and Ang-2 positive vessels (−62.5%). Skin biopsies showed a mean reduction in density of microvessels (−49.0%) and proliferating vessels (−25.7%). Gene expression profiling of tumor samples implied recruitment and potential activation of lymphocytes. Biopsies were safely conducted. Vanucizumab demonstrated a consistent biological effect on vascular-related biomarkers, confirming proof of concept. Skin-wound-healing biopsies were a valuable surrogate for studying angiogenesis-related mechanisms.     

Chemical modification of ribonuclease A with 4-arsono-2-nitrofluorobenzene

4-Arsono-2-nitrofluorobenzene reacts selectively at the anion binding site of bovine pancreatic ribonuclease A. The major derivative is the inactive 41-(4-arsono-2-nitrophenyl) ribonuclease A (45% yield). Additional products are 1-alpha-(4-arsono-2-nitrophenyl) ribonuclease A (11% yield) which is enzymatically active and the disubstituted, inactive 1,41-bis-(4-arsono-2-nitrophenyl) ribonuclease A (25% yield). 2' (3')-O-Bromoacetyluridine reacts with 41-(4-arsono-2-nitrophenyl) ribonuclease A exclusively at the histidine-12 residue at a rate which is approximately one-fourth the rate observed with the unmodified enzyme. Saturation kinetics are observed and the dissociation constant for the protein-inhibitor complex is 0.096 +/- 0.023 M. The first-order unimolecular decomposition constant for complex breakdown is 8.9 +/- 2.9 X 10(-4) s-1. 2'-Bromoacetamido-2'-deoxyuridine reacts with 41-(4-arsono-2-nitrophenyl) ribonuclease A 25 times more slowly than 2'(3')-O-bromoacetyluridine. Bromoacetate reacts with 41-(4-arsono-2-nitrophenyl) ribonuclease A predominantly at the histidine-119 residue at a rate 45 times less than that found for the unmodified enzyme. The results of the alkylation studies imply that the dianionic arsonate does not occupy the phosphate binding site in the enzyme but is sufficiently proximate to account for a decrease in bromoacetate binding as well as a reduction in the nucleophilic reactivity of histidine-12 and -119. All these effects may be accounted for in terms of a local electrostatic perturbation of the active site region by the arsononitrophenyl group.     

Dietary titanium and infant growth

Dietary titanium as TiO²⁺ improved animal growth during infancy while inhibiting the metabolism of intestinal bacteria. TiO²⁺ was also found capable of inhibiting human cytomegalovirus in tissue culture. These and other findings indicate TiO²⁺ improves infant growth by acting as an anti-bacterial and antiviral agent. The behavior of TiO²⁺ stands in contrast to that of TiO₂, which is inert.