Mycobacterial DNA gyrase: enzyme purification and characterization of supercoiling activity.

Putative structural genes encoding Mycobacterium bovis BCG gyrase A and gyrase B subunits were expressed in Escherichia coli under the control of a regulated promoter. Upon induction, high levels of proteins of M(r) 92,000 and 75,000 were generated. Purification and reconstitution of these proteins yielded an enzyme with bacterial DNA gyrase activity. DNA supercoiling activity of the mycobacterial enzyme required ATP, Mg2+, and spermidine. Like other bacterial DNA gyrases, the supercoiling activity of the mycobacterial enzyme was inhibited by low concentration of the classical gyrase B subunit inhibitors novobiocin and coumermycin. Older gyrase A subunit inhibitors, nalidixic and oxolinic acid, had no effect on the supercoiling activity at 400 to 800 micrograms/ml. However, in vitro assays to show the inhibition of supercoiling activity and stimulation of cleavable complex formation demonstrated that ciprofloxacin is a potent inhibitor of mycobacterial DNA gyrase. The availability of highly purified mycobacterial DNA gyrase could aid in future investigations of quinolone derivatives targeting Mycobacterium specifically.

Expression and characterization of the trans-activating protein Tax of human T-cell leukemia virus type I in Saccharomyces cerevisiae.

The trans-activator protein Tax of human T-cell leukemia virus type I (HTLV-I) stimulates transcription of the viral genome from the long terminal repeat. With a reporter HIS4TATA::lacZ fusion gene, the transcriptional activity of the Tax-responsive element in the long terminal repeat was tested in Saccharomyces cerevisiae. We found that fragments containing the 21-bp repeat of the HTLV-I enhancer stimulate synthesis of beta-galactosidase activity 15- to 20-fold. To test the ability of the Tax protein to trans activate the HTLV-I enhancer in yeast cells, the pX region of HTLV-I, encoding the Tax protein, was cloned under the control of the yeast GAL1 promoter. The expressed Tax protein is localized in the nucleus and associated with the yeast nuclear matrix fraction. In yeast cells that contained the integrated tax gene, two- to sixfold stimulation of expression from the HTLV-I enhancer was detected at the early stages of tax induction. This in vivo reconstitution system provides a new approach for examining the host factor(s), the signal transduction mechanism(s), and the role of nuclear architecture involved in Tax-mediated trans activation.

Premarital HIV-1 testing in New Jersey.

To answer questions related to the usefulness of premarital testing for human immunodeficiency virus type 1 (HIV-1), two "blinded" or "nonlinked" HIV-1 serosurveys were done in New Jersey, a state with a high incidence of AIDS, on blood specimens submitted for a premarital serologic test for syphilis. The first survey involved premarital blood specimens submitted to the New Jersey Department of Health laboratory for the year starting September 1987. The second survey involved premarital specimens submitted to five private or hospital clinical laboratories in the spring of 1989, of which approximately 1,000 consecutive premarital specimens from each laboratory were sent to the Department of Health laboratory for HIV-1 testing. Of 4,247 specimens tested in the 1987-1988 survey, 21 (0.49%) were positive for antibodies to HIV-1, while among 4,696 specimens in the 1989 survey, 29 (0.62%) were positive. When the survey results were weighted by the number of marriages by geographic regions of the state, the weighted premarital HIV-1 seroprevalence was 0.55% for the 1987-1988 survey and 0.62% for the 1989 survey. The male/female ratio of positive tests was 2.7:1 in 1987-1988 and 1.6:1 in 1989. Of the 8,943 specimens in both surveys, 5 (0.06%) gave an indeterminate immunoblot result, compared with 50 positive results. These percentages of premarital HIV-1 infections are much higher than earlier estimates and reports and are of the same magnitude as recently reported blinded premarital HIV-1 testing elsewhere. Results of this magnitude support a recommendation in New Jersey of voluntary HIV-1 counseling and testing for marriage applicants.

Antibody testing in Lyme disease. A comparison of results in four laboratories.

To evaluate the interlaboratory and intralaboratory agreement in the performance of Lyme disease serological testing, we sent serum specimens from 132 outdoor workers in New Jersey to as many as four independent laboratories. These included one state department of health laboratory, one large commercial laboratory, and two research laboratories. The measurement of agreement employed, the kappa statistic, ranged from .45 to .53 among the four laboratories and from .50 to .54 within the commercial laboratory. These values represent low levels of agreement. The data suggest that Lyme disease serological testing procedures should be standardized so that Lyme disease test results are more comparable between laboratories.

Inhibition of HIV replication by liposomal encapsulated amphotericin B.

This report shows the potential of using a liposomal encapsulated preparation of amphotericin B (a polyene macrolide antibiotic) for the in vitro inhibition of HIV. There was no significant difference between the effective doses of the free form of drug when compared to the liposomal encapsulated preparation in inhibiting the growth of HIV. Virus expression was suppressed at a concentration of 5-10 micrograms/ml of the drugs. The liposomal preparation showed greatly reduced cytotoxicity in experiments using cultures of murine leukocytes. These results show the potential usefulness of liposomal encapsulated drugs in the treatment of patients with AIDS or AIDS related complex.