Comparison of agar-gel precipitin responses among strains of fowl adenovirus using antigens prepared from chorioallantoic membranes and chicken kidney cell cultures.

Agar-gel precipitin responses obtained for serologically different strains of fowl adenovirus (FAV) in tests using antigens prepared from FAV-infected chorioallantoic membranes (CAM antigen) and chicken kidney cell cultures (CKC antigen) were compared. Findings showed that both types of antigens exhibited less sensitivity to heterologous than to homologous antisera and that quantitative differences in sensitivity were present between serotypes. CAM antigens were more sensitive than CKC antigens to heterologous antisera. Polyvalent CAM antigens containing 2 or 3 antigens increased sensitivity in testing of field serum samples, resulting in a higher rate of detection.

Limunectin. A phosphocholine-binding protein from Limulus amebocytes with adhesion-promoting properties.

A protein that binds to and precipitates with pneumococcal C-polysaccharide and a phosphocholine (PC) derivative of bovine serum albumin has been affinity purified from Limulus amebocytes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis reveals that the isolated protein consists of a single polypeptide chain of approximately 50 kDa. It is an intracellular protein localized in the secretory granules of amebocytes according to immunogold staining. Although it shares the PC-binding property with C-reactive protein isolated from Limulus and other animal species, it differs from C-reactive protein in that the latter binds to PC only in the presence of Ca2+, whereas the newly isolated protein binds to PC in a Ca(2+)-independent manner. In this respect, the newly isolated PC-binding protein resembles the antibodies to PC of mouse myelomas. The gene coding for this protein has been isolated. The gene sequence predicts a protein of 54 kDa with an unusual structural feature: it consists almost entirely of 10 contiguous segments, 45 amino acids in length, with extensive homology. Some limited sequence homologies were found between the 54-kDa protein and segments of vitronectin, gelatinase, and collagenase. It binds to bacterial cells, fixed amebocytes, and a number of extracellular matrix molecules. Due to its structural and some functional similarities to other adhesion molecules, the Limulus 54-kDa protein was named "Limunectin."