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Biomedical subjects

J T Stapleton

Publications and source records attributed to J T Stapleton.

53 records · Page 3Linked to original sources
PubMed1991

Hepatitis A virus attachment to cultured cell lines.

Identification of a hepatitis A virus (HAV) receptor is important for understanding HAV tissue tropism and replication sites and in the design of vaccines and antiviral therapy. The attachment of HAV to cultured cell lines was evaluated: Calcium-dependent specific attachment of four HAV strains to permissive cells occurred, whereas binding to nonpermissive cells did not. Investigation of HAV antigenic variant strains (neutralization escape mutants) demonstrated identical attachment properties with neutralization-susceptible strains, suggesting that the immunodominant neutralization antigenic site of HAV is not directly involved in cell attachment. Unlike foot-and-mouth-disease virus, a related picornavirus, RGD peptides (arginine-glycine-aspartic acid) were unable to interfere with HAV attachment. These studies demonstrate that HAV has a calcium-dependent receptor on cultured cell lines and suggest that the HAV binding region does not involve an RGD sequence or the HAV immunodominant neutralization site.

Amino Acid Sequence↗
PubMed1991

The hepatitis A virus polyprotein expressed by a recombinant vaccinia virus undergoes proteolytic processing and assembly into viruslike particles.

Hepatitis A virus (HAV) contains a single-stranded, plus-sense RNA genome with a single long open reading frame encoding a polyprotein of approximately 250 kDa. Viral structural proteins are generated by posttranslational proteolytic processing of this polyprotein. We constructed recombinant vaccinia viruses which expressed the HAV polyprotein (rV-ORF) and the P1 structural region (rV-P1). rV-ORF-infected cell lysates demonstrated that the polyprotein was cleaved into immunoreactive 29- and 33-kDa proteins which comigrated with HAV capsid proteins VP0 and VP1. The rV-P1 construct produced a 90-kDa protein which showed no evidence of posttranslational processing. Solid-phase radioimmunoassays with human polyclonal anti-HAV sera and with murine or human neutralizing monoclonal anti-HAV antibodies recognized the rV-ORF-infected cell lysates. Sucrose density gradients of rV-ORF-infected cell lysates contained peaks of HAV antigen with sedimentation coefficients of approximately 70S and 15S, similar to those of HAV empty capsids and pentamers. Immune electron microscopy also demonstrated the presence of viruslike particles in rV-ORF-infected cell lysates. Thus, the HAV polyprotein expressed by a recombinant vaccinia virus demonstrated posttranslational processing into mature capsid proteins which assembled into antigenic viruslike particles.

Base Sequence↗
PubMed1991

Physicians' effectiveness in assessing risk for human immunodeficiency virus infection.

An American Medical Association committee recently recommended that physicians routinely screen patients for behaviors that put patients at risk for human immunodeficiency virus infection, yet there is evidence that this screening does not occur routinely. Faculty, fellows, and residents at a teaching hospital in a midwestern state with a low prevalence of acquired immunodeficiency syndrome were surveyed regarding their experience in screening for human immunodeficiency virus, their training related to substance abuse and human sexuality, and their confidence and ease in addressing such topics with their patients. Results indicated that only 11% routinely screened patients for high-risk behaviors. While most physicians had received training in human sexuality, most had not received training in substance abuse screening. Those trained felt more confident in addressing substance abuse and human sexuality and felt more comfortable in caring for patients known to be infected with human immunodeficiency virus. A concerted effort to encourage human immunodeficiency virus risk assessment by physicians is needed. This should include training opportunities in screening and counseling patients about sexual activities and substance abuse.

Acquired Immunodeficiency Syndrome↗
PubMed1990

In vivo replication and reversion to wild type of a neutralization-resistant antigenic variant of hepatitis A virus.

Six seronegative owl monkeys were intravenously inoculated with an antigenic variant (S18) of hepatitis A virus that is highly adapted to growth in cell culture and resists neutralization by monoclonal antibodies due to replacement of aspartic acid 70 of capsid protein VP3 with histidine. Each developed hepatitis 22-33 days after inoculation. Virus in feces, serum, and liver was quantified by radioimmunofocus assay. Viremia developed 7-11 days after inoculation, in parallel with fecal shedding of virus, and persisted for a mean of 20.5 days. Although the antigenic variant was recovered from feces or liver of three animals, virus in liver at the time of enzyme elevations was predominantly wild-type antigenic phenotype. Virus was not recovered from liver 96 days after challenge. These studies further define virologic events in hepatitis A and show that in vivo replication of an antigenic variant was restricted compared with that of wild-type virus.

Animals↗
PubMed1989

A randomized, placebo-controlled trial of oral acyclovir for the prevention of cytomegalovirus disease in recipients of renal allografts.

Cytomegalovirus is a major viral pathogen in patients who undergo renal transplantation, and cytomegalovirus disease is difficult to treat. We therefore conducted a randomized, placebo-controlled, double-blind trial of acyclovir for the prevention of cytomegalovirus disease in recipients of renal allografts from cadavers. Acyclovir was given orally in doses of 800 to 3200 mg per day, according to the patients' estimated level of renal function. Patients took the first dose of either acyclovir or placebo six hours before transplantation and continued to take the assigned medication for 12 weeks. Of 118 patients enrolled in the study, 104 completed at least 30 days on the study medication and were included in our analysis of the results. During the first year after transplantation, 4 of 53 patients (7.5 percent) in the acyclovir group had symptomatic cytomegalovirus disease, as compared with 15 of 51 (29 percent) in the placebo group (P = 0.002). There was a single case of cytomegalovirus pneumonia in the acyclovir group, as compared with nine in the placebo group. The greatest prophylactic benefit of acyclovir was observed among seronegative patients who had received a kidney from a seropositive donor; only one of six such patients in the acyclovir group had cytomegalovirus disease, as compared with all seven in the placebo group. Acyclovir decreased the incidence of documented cytomegalovirus infection (with or without symptomatic disease) to 36 percent from 61 percent among the patients who received the placebo (P = 0.011). Among the patients who received acyclovir, the rates of recovery of virus from the blood and urine were significantly reduced, but the rate of viral shedding from the pharynx was not significantly different from that in the placebo group. There were no differences between the groups in the frequency of adverse events or in the rate of survival of either grafts or patients. We conclude that the oral administration of acyclovir, beginning before the transplantation of a renal allograft from a cadaver, reduces the rate of cytomegalovirus infection and disease without affecting the survival rate of either grafts or patients.

Acyclovir↗
PubMed1988

Long-term acyclovir suppression of frequently recurring genital herpes simplex virus infection. A multicenter double-blind trial.

Normal adults with six or more episodes of genital herpes in the previous year were enrolled in a one-year, multicenter, double-blind trial comparing placebo with 400 mg of acyclovir administered orally twice daily. Patients with episodes during the study were offered 200 mg of acyclovir administered orally five times daily for five days; this allowed comparison of suppressive and episodic treatment. After one year, 227 (44%) of 519 patients receiving suppressive treatment and seven (2%) of 431 receiving placebo (episodic) treatment remained free of recurrences, and the mean numbers of recurrences per year were 1.8 and 11.4, respectively. Among 67 patients who had received suppressive therapy for one year, the mean duration of lesions in the first episode following the discontinuation of treatment was 9.3 days compared with 7.3 days among 45 patients who had received episodic therapy for one year. Treatment was well tolerated, and no changes were noted in the in vitro susceptibility to acyclovir of herpes simplex virus cultured during or after the one-year trial. Continuous or episodic oral acyclovir therapy for one year remained safe and effective.

Acyclovir↗
PubMed1988

Identification of an immunodominant antigenic site involving the capsid protein VP3 of hepatitis A virus.

Hepatitis A virus, an hepatotropic picornavirus, is a common cause of acute hepatitis in man for which there is no available vaccine. Competitive binding studies carried out in solid phase suggest that neutralizing monoclonal antibodies to hepatitis A virus recognize a limited number of epitopes on the capsid surface, although the polypeptide locations of these epitopes are not well defined. Neutralization-escape mutants, selected for resistance to monoclonal antibodies, demonstrate broad cross-resistance to other monoclonal antibodies. Sequencing of virion RNA from several of these mutants demonstrated that replacement of aspartic acid residue 70 of capsid protein VP3 (residue 3070) with histidine or alanine confers resistance to neutralization by monoclonal antibody K2-4F2 and prevents binding of this antibody and other antibodies with similar solid-phase competition profiles. These results indicate that residue 3070 contributes to an immunodominant antigenic site. Mutation at residue 102 of VP1 (residue 1102) confers partial resistance against antibody B5-B3 and several other antibodies but does not prevent antibody attachment. Both VP3 and VP1 sites align closely in the linear peptide sequences with sites of neutralization-escape mutations in poliovirus and human rhinovirus, suggesting conservation of structure among these diverse picornaviruses. However, because partial neutralization resistance to several monoclonal antibodies (2D2, 3E1, and B5-B3) was associated with mutation at either residue 3070 or residue 1102, these sites appear more closely related functionally in hepatitis A virus than in these other picornaviruses.

Alanine↗
PubMed1988

In vitro assay to demonstrate high-level erythromycin resistance of a clinical isolate of Treponema pallidum.

We have previously demonstrated that cells of Treponema pallidum freshly extracted from infected rabbit testes can be intrinsically radiolabeled with [35 S]methionine to very high specific activities. In this study we used the inhibition of [35 S]methionine incorporation into trichloroacetic acid-precipitable protein in vitro as an assay to test the susceptibilities of three different pathogenic treponemal strains to various antibiotics. In general, the results correlated very well with the known efficacies of these antibiotics in treating human patients with syphilis. One of the strains tested, however, a clinical isolate of T. pallidum designated street strain 14, was found to exhibit high-level resistance to erythromycin and a closely related macrolide, roxithromycin (RU 965). Street strain 14 was originally isolated from a human patient with active secondary syphilis who failed to respond to erythromycin therapy. Thus, our results indicate that an erythromycin-resistant strain of T. pallidum can be responsible for erythromycin treatment failure. In addition, street strain 14 treponemes were found to be generally less susceptible by this assay to a variety of antibiotics than were treponemes of the T. pallidum Nichols strain. These findings suggest that the outer envelope of street strain 14 treponemes may be generally less permeable to antibiotics than is that of Nichols strain treponemes.

Animals↗
PubMed1988

Cure of mucormycosis in a renal transplant patient receiving ciclosporin with maintenance of immunosuppression.

Rhinocerebral mucormycosis in renal transplant recipients is associated with high mortality and allograft rejection. We report the first case of successful treatment of mucormycosis in a renal transplant recipient receiving ciclosporin and corticosteroids with maintenance of renal function. It is postulated that the relatively specific immunosuppression caused by ciclosporin, together with aggressive medical and surgical intervention, may enable the cure of this life-threatening fungal infection without loss of donor kidney function.

Adult↗
PubMed1987

Neutralization escape mutants define a dominant immunogenic neutralization site on hepatitis A virus.

Hepatitis A virus is an hepatotrophic human picornavirus which demonstrates little antigenic variability. To topologically map immunogenic sites on hepatitis A virus which elicit neutralizing antibodies, eight neutralizing monoclonal antibodies were evaluated in competition immunoassays employing radiolabeled monoclonal antibodies and HM-175 virus. Whereas two antibodies (K3-4C8 and K3-2F2) bound to intimately overlapping epitopes, the epitope bound by a third antibody (B5-B3) was distinctly different as evidenced by a lack of competition between antibodies for binding to the virus. The other five antibodies variably blocked the binding of both K3-4C8-K3-2F2 and B5-B3, suggesting that these epitopes are closely spaced and perhaps part of a single neutralization immunogenic site. Several combinations of monoclonal antibodies blocked the binding of polyclonal human convalescent antibody by greater than 96%, indicating that the neutralization epitopes bound by these antibodies are immunodominant in humans. Spontaneously arising HM-175 mutants were selected for resistance to monoclonal antibody-mediated neutralization. Fourteen clonally isolated mutants demonstrated substantial resistance to multiple monoclonal antibodies, including K3-4C8-K3-2F2 and B5-B3. In addition, 13 mutants demonstrated a 10-fold or greater reduction in neutraliztion mediated by polyclonal human antibody. Neutralization resistance was associated with reduced antibody binding. These results suggest that hepatitis A virus may differ from poliovirus in possessing a single, dominant neutralization immunogenic site and therefore may be a better candidate for synthetic peptide or antiidiotype vaccine development.

Animals↗
PubMed1985

Neutralizing antibody to hepatitis A virus in immune serum globulin and in the sera of human recipients of immune serum globulin.

We determined the titer of neutralizing antibody to hepatitis A virus in five lots of immune serum globulin and in the sera of human recipients of immune globulin using a new and sensitive procedure, the radioimmunofocus inhibition assay. The neutralizing antibody titer of four immune globulin lots ranged from 1:170,000 to 1:406,000, and was approximately 100-fold the antibody titer determined by radioimmunoassay. The neutralizing antibody titer of a Bureau of Biologics reference immunoglobulin was 1:794,000. Sera collected from 18 healthy men who had undergone prophylaxis with immune globulin (0.02 ml/kg body wt) were negative when tested by radioimmunoassay. However, 2 of 18 sera collected before administration of immune globulin and sera from all 18 men collected 3 and 55 days later contained detectable neutralizing antibody. The measurement of neutralizing antibody should prove useful for standardizing passive immunoprophylaxis against hepatitis A as well as for evaluating the potential efficacy of new hepatitis A virus vaccines.

Antibodies, Viral↗
PubMed1983

Hypoglycemic coma due to disopyramide toxicity.

Disopyramide (Norpace) is a widely used, generally well tolerated antiarrhythmic agent. We have described an 82-year-old patient with non-insulin-dependent diabetes mellitus and renal insufficiency who had hypoglycemic coma and obstructive uropathy due to disopyramide therapy.

Aged↗
PubMedDate not supplied

Potential for development of antibiotic resistance in pathogenic treponemes.

Penicillin has been widely used for many years for the treatment of yaws and other human treponematoses without the emergence of penicillin-resistant treponemal strains. However, experience with various bacterial pathogens serves to emphasize that resistance to penicillin and other antibiotics can suddenly appear after decades of exquisite sensitivity. The finding of plasmid DNA in at least one strain of Treponema pallidum, the reporting of several instances in which antibiotic treatment of syphilis has failed, and the demonstration that a recent clinical isolate of T. pallidum is resistant to erythromycin indicate that the pathogenic treponemes do have the potential to develop antibiotic resistance. Although it is impossible to predict when antibiotic resistance might become a significant problem in dealing with infections caused by these organisms, the vigorous pursuit of alternatives to antibiotic therapy for the control of human treponematoses seems prudent.

Anti-Bacterial Agents↗