Publications

Under different circumstances, natural killer T (NKT) cells can cause a T helper (Th) 1 or a Th2 polarization of immune responses. We show here, however, that mouse NKT cells with an invariant V alpha 14 rearrangement (V alpha 14i NKT cells) rapidly produce both IL-4 and IFN-gamma, and this pattern could not be altered by methods that polarize naive CD4+ T cells. Surprisingly, although cytokine protein was detected only after activation, resting V alpha 14i NKT cells contained IL-4 and IFN-gamma mRNAs. Despite this finding, in vivo priming of mice with the glycolipid antigen recognized by V alpha 14i NKT cells resulted in a more Th2-oriented response upon antigen re-exposure. The V alpha 14i NKT cells from primed mice retain the ability to produce IL-4 and IFN-gamma, but they are less effective at activating NK cells to produce IFN-gamma. Our data therefore indicate that V alpha 14i NKT cells have a relatively inflexible immediate cytokine response, but that changes in their ability to induce IFN-gamma secretion by NK cells may determine the extent to which they promote Th1 responses.

China is currently undergoing a serious HIV-1 epidemic in intravenous drug users, sex workers, and former plasma donors. Little is known, however, about HIV-1 risk in Chinese men who have sex with men. In this study of seroprevalence in such men in Beijing, we recorded 15 (3.1%, 95% CI 1.8-5.1) of 481 men infected with HIV-1. Overall, 238 (49%) of participants reported unprotected anal intercourse during the previous 6 months. HIV-1 seropositivity was independently associated with being older than 39 years and having had more than 20 male sexual partners. Most men older than 39 years had been married. Our findings suggest the potential for spread of HIV-1 between men who have sex with men and to their heterosexual partners.

Human chymase is a chymotryptic serine peptidase stored and secreted by mast cells. Compared with other chymotryptic enzymes, such as cathepsin G and chymotrypsin, it is much more slowly inhibited by serum serpins. Although chymase hydrolyzes several peptides and proteins in vitro, its target repertoire is limited compared with chymotrypsin because of selective interactions in an extended substrate-binding site. The best-known natural substrate, angiotensin I, is cleaved to generate vasoactive angiotensin II. Selectivity of angiotensin cleavage depends in major part on interactions involving substrate residues on the carboxyl-terminal (P1'-P2') side of the cleaved bond. To identify new targets based on interactions with residues on the aminoterminal (P4-P1) side of the site of hydrolysis, we profiled substrate preferences of recombinant human chymase using a combinatorial, fluorogenic peptide substrate library. Data base queries using the peptide (Arg-Glu-Thr-Tyr-X) generated from the most preferred amino acid at each subsite identify albumin as the sole, soluble, human extracellular protein containing this sequence. We validate the prediction that this site is chymase-susceptible by showing that chymase hydrolyzes albumin uniquely at the predicted location, with the resulting fragments remaining disulfide-linked. The site of hydrolysis is highly conserved in vertebrate albumins and is near predicted sites of metal cation binding, but nicking by chymase does not alter binding of Cu2+ or Zn2+. A synthetic peptidic inhibitor, diphenyl N alpha-benzoxycarbonyl-l-Arg-Glu-Thr-PheP-phosphonate, was designed from the preferred P4-P1 substrate sequence. This inhibitor is highly potent (IC50 3.8 nM) and 2,700- and 1,300-fold selective for chymase over cathepsin G and chymotrypsin, respectively. In summary, these findings reveal albumin to be a substrate for chymase and identify a potentially useful new chymase inhibitor.

Preclinical studies have linked corticosteroid secretion and levels with drug self-administration by animals. In a double-blind, cross-over study, subjective, physiological, and endocrine responses to intravenous doses of methamphetamine 0.5 mg/kg or placebo were assessed in eight methamphetamine-experienced subjects after three cortisol-modifying premedication conditions: augmenting cortisol level with oral hydrocortisone 50 mg, blocking cortisol response with the corticosteroid synthesis inhibitor metyrapone 1500 mg orally, or no premedication. Although the pharmacologic manipulations produced the expected hormonal changes, subjective response to the methamphetamine showed few differences. Diminishing cortisol response by pharmacologic blockade did not alter the pleasurable effects of methamphetamine. Hydrocortisone did increase self-reported 'bad drug effect' and decreased craving after saline placebo relative to the period following methamphetamine. Metyrapone was associated with significant premature ventricular complexes in two subjects during methamphetamine administration and may not be safe for those who use methamphetamine.