A new sesquiterpene lactone from Salvia plebeia.

A new eudesmanolide, 1α-acetoxy-8α,9ß-dihydroxy-2-oxo-eudesman-3,7(11)-dien-8,12-olide (2), together with a known eudesmanolide, 1α-acetoxy-8α-hydroxy-2-oxo-eudesman-3,7(11)-dien-8,12-olide (1), and a known flavone, 4',5,7-trihydroxy-6-methoxyflavone (3), was isolated from the plant of Salvia plebeia. Three compounds were structurally elucidated by spectroscopic and chemical methods.

Macrolactonization catalyzed by the terminal thioesterase domain of the nonribosomal peptide synthetase responsible for lichenysin biosynthesis.

The excised terminal thioesterase of the lichenysin nonribosomal peptide synthetase was found to be a highly efficient and versatile enzyme. Its activity strictly requires the R configuration of the beta-hydroxy fatty acid and the side chains of aspartate-5 and isoleucine-7, but tolerates changes in five other residues of the substrate. Characterization of this enzyme facilitates future effort to engineer the lichenysin synthetase for biotechnological applications.

B-cell responses in patients who have recovered from severe acute respiratory syndrome target a dominant site in the S2 domain of the surface spike glycoprotein.

Severe acute respiratory syndrome (SARS) is a recently emerged infectious disease caused by a novel strain of coronavirus. Examination of the immune responses of patients who have recovered from SARS should provide important information for design of a safe and effective vaccine. We determined the continuous viral epitopes targeted by antibodies in plasma samples from convalescent SARS patients through biopanning with a vast M13 phage display dodecapeptide library. These epitopes converged to very short peptide fragments, one on each of the structural proteins spike and nucleocapsid and the nonstructural proteins 3a, 9b, and nsp 3. Immunoassays found that most of the patients who had recovered from SARS developed complementary antibodies to the epitope-rich region on the spike S2 protein, indicating that this is an immunodominant site on the viral envelope comprising the spike, matrix, and small envelope glycoproteins. These S2-targeting antibodies were shown to effectively neutralize the coronavirus, indicating that they provided protective immunity to help the patients recover from the viral infection. These results suggest that the SARS coronavirus might have an antigenic profile distinct from those of other human or animal coronaviruses. Due to the tested safety and protective effects of the convalescent-phase serological antibodies, identification of their complementary antigens may enable the design of an epitope-based vaccine to prevent potential antibody-mediated immunopathology.