Involvement of the calcium-sensing receptor in human taste perception.

By human sensory analyses, we found that various extracellular calcium-sensing receptor (CaSR) agonists enhance sweet, salty, and umami tastes, although they have no taste themselves. These characteristics are known as "kokumi taste" and often appear in traditional Japanese cuisine. Although GSH is a typical kokumi taste substance (taste enhancer), its mode of action is poorly understood. Here, we demonstrate how the kokumi taste is enhanced by the CaSR, a close relative of the class C G-protein-coupled receptors T1R1, T1R2, and T1R3 (sweet and umami receptors). We identified a large number of CaSR agonist gamma-glutamyl peptides, including GSH (gamma-Glu-Cys-Gly) and gamma-Glu-Val-Gly, and showed that these peptides elicit the kokumi taste. Further analyses revealed that some known CaSR agonists such as Ca(2+), protamine, polylysine, L-histidine, and cinacalcet (a calcium-mimetic drug) also elicit the kokumi taste and that the CaSR-specific antagonist, NPS-2143, significantly suppresses the kokumi taste. This is the first report indicating a distinct function of the CaSR in human taste perception.

Mycobacterial codon optimization enhances antigen expression and virus-specific immune responses in recombinant Mycobacterium bovis bacille Calmette-Guérin expressing human immunodeficiency virus type 1 Gag.

Although its potential for vaccine development is already known, the introduction of recombinant human immunodeficiency virus (HIV) genes to Mycobacterium bovis bacille Calmette-Guérin (BCG) has thus far elicited only limited responses. In order to improve the expression levels, we optimized the codon usage of the HIV type 1 (HIV-1) p24 antigen gene of gag (p24 gag) and established a codon-optimized recombinant BCG (rBCG)-p24 Gag which expressed a 40-fold-higher level of p24 Gag than did that of nonoptimized rBCG-p24 Gag. Inoculation of mice with the codon-optimized rBCG-p24 Gag elicited effective immunity, as evidenced by virus-specific lymphocyte proliferation, gamma interferon ELISPOT cell induction, and antibody production. In contrast, inoculation of animals with the nonoptimized rBCG-p24 Gag induced only low levels of immune responses. Furthermore, a dose as small as 0.01 mg of the codon-optimized rBCG per animal proved capable of eliciting immune responses, suggesting that even low doses of a codon-optimized rBCG-based vaccine could effectively elicit HIV-1-specific immune responses.

Structural analysis of vaccinia virus DIs strain: application as a new replication-deficient viral vector.

DIs is a restrictive host range mutant of vaccinia virus strain DIE that grows well only in chick embryo fibroblast cells but is unable to grow in most mammalian cells. In this study, we identified one major deletion (15.4 kbp) which results in the loss of 19 putative open reading frames in the left end of the genome. We then established a system to express foreign genes by inserting them into the deleted region of DIs. We constructed rDIs to express the bacteriophage T7 polymerase (T7pol) gene and showed the expression in various mammalian cell lines by reporter luciferase gene expression under the T7 promoter. We also expressed the full-length human immunodeficiency virus (HIV)-1 NL432 gag gene. The expressed gag gene product induced high levels of cytotoxic T lymphocytes in immunized mice. These data suggest that DIs is useful as an efficient, transient replication-deficient viral vector.