Proteomics was used to identify a protein encoded by ORF 3a in a SARS-associated coronavirus (SARS-CoV). Immuno-blotting revealed that interchain disulfide bonds might be formed between this protein and the spike protein. ELISA indicated that sera from SARS patients have significant positive reactions with synthesized peptides derived from the 3a protein. These results are concordant with that of a spike protein-derived peptide. A tendency exists for co-mutation between the 3a protein and the spike protein of SARS-CoV isolates, suggesting that the function of the 3a protein correlates with the spike protein. Taken together, the 3a protein might be tightly correlated to the spike protein in the SARS-CoV functions. The 3a protein may serve as a new clinical marker or drug target for SARS treatment.

The effect of monoethylphosphate (MEP, commercial available or synthesized) together with IL-2 on the selective proliferation of human Υ δ T cells in vitro from peripheral blood mononuclear cells (PBMC) of healthy donors and of cancer patients was investigated. The Υ δ T cells were stimulated by MEP to proliferate in a dose-dependent manner. The effect of synthesized MEP was 10 times greater than that of commercial MEP. When the PBMCs of healthy donors were cultured for 25 d in the medium containing different concentrations of MEP, the total cell number increased about 1000-3000 fold; and the ratio of Υ δ T cells reached to 70-80%. The selective expansion of Υ δ T cells depended on the synergic action of MEP and IL-2. The bulk cultured Υ δ T cells exhibited obvious cytotoxic activities against allogenic tumor cell lines (SQ-5, K562 and Daudi) and autologous tumor cells. The culture system described here not only offers a simple method for obtaining a large number of Υ δ T cells which may become a new effector in the adoptive immunotherapy, but also provides a useful model for the further studies of the structure and function of Υ δ T cells in vitro .