In exploring the immunologic causes of chronic neutropenia, we identified a persistent neutrophil-specific antibody with NA2 specificity in the blood of a nontransfused two-year-old girl with severe neutropenia. No such antibody was detected in the maternal blood. The antibody was first studied and identified when the patient was 11 months old, but she had had clinical manifestations since the age of one month. After a trial of steroid therapy, a marked but temporary reduction in the antibody titer occurred, accompanied by the rise of the neutrophils to normal level. Neutropenia reoccurred, however, when the antibody titer began to rise, despite continuation of steroid therapy. This transient response allowed the patient's neutrophils to become available and identified as NA2-positive. Although the cause of this disorder remains obscure, the data presented indicate that the anti-NA2 autoantibody is responsible for the neutropenia observed.

A rapid manual Polybrene test for detection of red blood cell antibodies have been devised which uses standard laboratory equipment. Red blood cells are incubated with the test sera in a low ionic medium at room temperature for one minute. Polybrene, a quaternary ammonium polymer, is then introduced to cause nonspecific red blood cell aggregation. The test tubes are centrifuged, the cell free supernatant fluid decanted, and the Polybrene effect on the cells is neutralized by adding a dilute sodium citrate-glucose solution. The hemagglutination results are evaluated macroscopically and microscopically. The entire procedure is completed in less than three minutes. In the Rh system, the test is 10--160-fold more sensitive than the antiglobulin reaction. In other systems tested, except for the Kell, a high sensitivity is achieved. The sensitivity for the Kell system is markedly increased, however, by performing a supplementary antiglobulin reaction on the sensitized, Polybrene-treated, red blood cells. The antiglobulin reagent used for this purpose should lack anti-C4 and anti-C3 activities. Sensitivity for cold reactive antibodies is augmented by cooling the cells for 30 seconds before citrate-glucose reagent is added.

Cell type-specific gene delivery will be essential for in vivo display scAs against the human her2neu cell surface progene therapy. Our laboratory has previously developed tein, was injected. Cells were recovered from the peritoretroviral vector particles, derived from spleen necrosis neum, subjected to antibiotic selection, and tested for the virus, SNV, which display the antigen-binding site of an expression of a lacZ gene transduced by the retroviral vecantibody on the viral surface. Such particles infected only tor. We found that human target cells, which express her2-human cells in vitro, which expressed a receptor recogneu, were infected in vivo. However, neither human cells nized by the antibody. To test cell type-specific gene delivthat do not express her2neu, nor normal mouse cells were ery in vivo, a mouse model system has been developed.infected by such viral particles. These data give proof of Antibiotic resistant human target and non-target cells were principle that retroviral vector-mediated, cell type-specific injected into the peritoneum of SCID mice. Subsequently, gene delivery can be obtained in vivo. a vector solution containing 10 6 infectious particles, which

No abstract

The successful application of human gene therapy protocols on a broad clinical basis will depend on the availability of in vivo cell-type-specific gene delivery systems. We have developed retroviral vector particles, derived from spleen necrosis virus (SNV), that display the antigen binding site of an antibody on the viral surface. Using retroviral vectors derived from SNV that displayed single-chain antibodies (scAs) directed against a carcinoembryonic antigen-cross-reacting cell surface protein, we have shown that an efficient, cell-type-specific gene delivery can be obtained. In this study, we tested whether other scAs displayed on SNV vector particles can also lead to cell-type-specific gene delivery. We displayed the following scAs on the retroviral surface: one directed against the human cell surface antigen Her2neu, which belongs to the epidermal growth factor receptor family; one directed against the stem cell-specific antigen CD34; and one directed against the transferrin receptor, which is expressed on liver cells and various other tissues. We show that retroviral vectors displaying these scAs are competent for infection in human cells which express the antigen recognized by the scA. Infectivity was cell type specific, and titers above 105 CFU per ml of tissue culture supernatant medium were obtained. The density of the antigen on the target cell surface does not influence virus titers in vitro. Our data indicate that the SNV vector system is well suited for the development of a large variety of cell-type-specific targeting vectors.