Human immunodeficiency virus and hepatitis--implications for operating room personnel

Solvent-accessible cysteines in human cystathionine beta-synthase: crucial role of cysteine 431 in S-adenosyl-L-methionine binding

Cystathionine beta-synthase (CBS) is a tetrameric heme protein that catalyzes the PLP-dependent condensation of serine and homocysteine to cystathionine. CBS occupies a crucial regulatory position between the methionine cycle and transsulfuration. Human CBS contains 11 cysteine residues that are highly conserved in mammals but completely absent in the yeast enzyme, which catalyzes an identical reaction, suggesting a possible regulatory role for some of these residues. In this report, we demonstrate that in both the presence and absence of the CBS allosteric regulator S-adenosyl-l-methionine (AdoMet), only C15 and C431 of human CBS are solvent accessible. Mutagenesis of C15 to serine did not affect catalysis or AdoMet activation but significantly reduced aggregation of the purified enzyme in vitro. Mutagenesis of C431 resulted in a constitutively activated form of CBS that could not be further activated by either AdoMet or thermal activation. We and others have previously reported a number of C-terminal CBS point mutations that result in a decreased or abolished response to AdoMet. In contrast to all of these previously investigated CBS mutants, the C431 mutant form of CBS was unable to bind AdoMet, indicating that either this residue is directly involved in AdoMet binding or its absence induces a conformational change that destroys the integrity of the binding site for this regulatory ligand.

Frequency of parenteral exposure and seroprevalence of HBV, HCV, and HIV among operation room personnel

A study was designed to determine the frequency of needle-stick injuries, immunization status for hepatitis B virus (HBV) and sero-prevalence of HBV, hepatitis C virus (HCV), and human immunodeficiency virus (HIV) infections among operation room personnel. Self-assessment questionnaires were completed and blood tested for HBsAg, anti-HBc (total), anti-HCV and anti-HIV. Of 114 operation room personnel studied, the majority (58.8%) reported more than four needle-stick injuries per year, 36.8% one to three needle-stick injuries per year, while 4.4% reported no needle-stick injury in the last five years. Thirty-six percent of personnel had received a complete course of hepatitis B vaccination. There was serological evidence of hepatitis HBV virus and/or HCV infections in 31% of the studied population. Four percent were reactive for HCV infection, 7.5% for HBsAg infection and 25.43% for anti-HBc (total); none was HIV positive. Eighty percent of the HCV positive and 55% of the anti-HBc (total) positive personnel had more than four needle-stick injuries per year in the last five years, while 75% HBsAg-reactive personnel had received one to three needle-stick injuries per year. This study indicates a need for continued efforts to minimize the risk of blood-borne infection by enhancing the compliance of operation room personnel with HBV vaccination and adherence to infection control measures.