R-ELISA: repeated use of antigen-coated plates for ELISA and its application for testing of antibodies to HIV and other pathogens.

In this paper we report on the evaluation of several procedures that allow for the repeated use of an antigen-coated, enzyme-linked immunosorbent assay (ELISA) plate for enzyme immunoassay (EIA). We have shown that antigen-coated ELISA plates that were incubated once with an aqueous solution containing 8 M urea, 2% sodium dodecyl sulfate and 2% mercaptoethanol, after an EIA, can be reused again for EIA without loss of antigenic capacity. Thus, in this procedure, after an EIA, the ELISA plates were washed once with the above solution and then in a buffer containing 20 mM Tris-HCl, pH 7.5, 0.1% Tween 20 and 500 mM NaCl. This washing protocol was shown to remove the primary antibody, enzyme-conjugated secondary antibody and substrate without removing the antigen from the ELISA plate microwells. Thus, an antigen-coated ELISA plate previously used for an assay could be reused. We tested this repeat ELISA (R-ELISA) procedure on high antigen-binding ELISA plates coated with two different plant virus proteins, a synthetic peptide, the p25/24 gag and the gp120 proteins of the human immuno-deficiency virus, or the staphylococcus enterotoxin protein. In each case tested, the procedure allowed for the repeated use of the same antigen-coated plates for EIA of the respective antibodies. This procedure should prove to be particularly valuable for mass screening of samples tested for HIV and other disease-causing agents.

A temporal study of the expression of the capsid, cytoplasmic inclusion and nuclear inclusion proteins of tobacco etch potyvirus in infected plants.

Young leaves of tobacco, systemically infected by tobacco etch potyvirus (TEV), were examined for the presence and distribution of four virus encoded proteins [capsid, cytoplasmic inclusion (CI) and two nuclear inclusion (NI) proteins] at various time periods after inoculation of expanded leaves of the plants. The analyses were carried out by ELISA and by immunogold electron microscopy of thin sections of the leaves. All four proteins were detected simultaneously in the systemic leaves for the first time on the fifth day after inoculation of the expanded leaves. All four proteins increased in concentration until the seventh day and then showed no further increase with the exception of the capsid protein which continued to accumulate. The CI protein was first detected in association with the plasmalemma/cell wall and was subsequently found mostly in the form of pinwheels in the cytoplasm. The two NI proteins were found at all times after infection within the nucleus, although small concentrations were detected in the cytoplasm. These experiments suggest that both the NIa and NIb proteins are transported into the nucleus immediately after synthesis. At the earliest time periods after infection, high concentrations of these proteins (NIa and NIb) were found in their non-inclusion form in the nucleolus. At 14 days after infection, both proteins were found only as inclusions in the nucleus. The capsid protein was found at all stages of infection only in the cytoplasm.

Radiation therapy and chemotherapy in malignant sweat gland tumors.

A case of a 62-year-old man with an incompletely resected recurrent adnexal skin tumor is reported. The patient had a complete resolution of tumor with external beam radiation therapy. The tumor metastasized to lung and pleura, and the patient's tumor nodules stabilized with methotrexate. The reported experience with radiation and chemotherapy for this tumor is reviewed and is then contrasted with the observations in this patient. Currently available radiation technics may be of value in managing patients with unresectable tumors.