A simple and rapid method for detection of serum IgM antibodies to the rubella virus hemagglutinin

Serum IgM antibodies directed against the rubella virus hemagglutinin can be detected without prior serum fractionation. In the first step of a newly developed method, chick erythrocytes were sensitized with a subhemagglutinating dose of rubella hemagglutinin. Next, the sensitized erythrocytes were mixed with patient serum, allowing specific antibodies to react with the fixed antigens. Finally, rabbit antibodies to human IgM were used to create bridges between IgM molecules on different blood cells. The visible result was an easily read hemagglutination with sera which contain specific rubella IgM antibodies. The procedure is very simple and rapid to perform. At least 20 sera can be examined in approximately 2 h. No sophisticated instruments are needed.We have tentatively called the new method rubella anti-IgM hemagglutination (HA). Rubella antiIgM HA was more sensitive than the standard density gradient centrifugation/hemagglutination inhibition technique, but the correlation between the methods was good. Non-specific inhibitors of hemagglutination or rheumatoid factors did not seem to interfere with the specificity of the new method, and competition for antigenic sites between antibodies from the IgG/IgA and IgM classes did not seem to represent a serious, practical problem.     

Receptor-Specific Targeting with Liposomes <Emphasis Type="BoldItalic">In Vitro</Emphasis> Based on Sterol-PEG<Subscript>1300</Subscript> Anchors

Purpose  The challenge in developing liposomes to be used in active drug targeting is to design a method that can be used for modifying liposomal membranes that is applicable for a number of different specific ligands. In this study, the post insertion technique was used with activated sterol-PEG₁₃₀₀ anchors and was evaluated with regard to its effectiveness in active targeting in vitro. The key advantage of these anchors is that the insertion step into the liposomal membrane takes place at room temperature and is very fast. Materials and Methods  For in vitro experiments, neuroblastoma cell lines overexpressing GD2 antigen on their surface as a target structure were chosen. This allowed the use of anti-GD2 antibodies coupled to the liposomal surface for testing of specific binding. These modified liposomes were labelled with rhodamine-PE and their cellular association was analyzed by flow cytometry. Results  It was shown that the activated sterol-PEG₁₃₀₀ anchors allow specific and significant interactions of the modified liposomes with GD2 positive cells. Conclusion  Coupling using sterol-PEG₁₃₀₀ anchors is both simple and rapid. It is reproducible and applicable for all ligands bearing amino groups. This method demonstrates the advantage of a ready-to-use system for the modification of pre-formed liposomes with different ligands. M. Gantert and F. Lewrick contributed equally to this publication.