Showing papers by "Myron S. Cohen published in 1994"

Multiple gonococcal opacity proteins are expressed during experimental urethral infection in the male.

Abstract: The opacity (Opa) proteins of Neisseria gonorrhoeae are a family of outer membrane proteins demonstrating phase and antigenic variation. N. gonorrhoeae strain FA0190 has 11 opa loci that encode at least 8 antigenically distinct Opa proteins. To determine if expression of one Opa protein or a subset of them is favored during gonococcal infection, we inoculated Opa-negative variants of strain FA1090 intraurethrally into male volunteers. The Opa phenotype of gonococci isolated from urine and urethral swab cultures from nine infected subjects was determined. Opa proteins were expressed in a large proportion of the reisolates from the infected subjects. Gonococci cultured from urine or urethral swab samples from six of the subjects were uniformly Opa positive, with the predominant Opa variants differing among subjects. Three different Opa proteins were represented as the predominant type in at least one subject each. In three subjects, there was more heterogeneity in Opa phenotype of the reisolates, including the presence of Opa-negative variants. An increase in the proportion of isolates expressing multiple Opa proteins occurred over time in most subjects. Passage of the inoculum in vitro did not result in similar changes in Opa expression. There was no detectable difference in infectivity of an Opa-negative variant and one expressing an Opa protein (OpaF) that was highly represented in reisolates from the original nine subjects. Reisolates from three infected volunteers inoculated with the OpaF variant showed continued expression of OpaF alone or in conjunction with other Opa proteins. These results demonstrate that there is strong selection for expression of one or more Opa proteins by strain FA1090 in vivo, but that no single protein is preferentially expressed during early infection in the male urethra.

Multiple gonococcal pilin antigenic variants are produced during experimental human infections.

Abstract: Gonococcal pilin variation is thought to allow immune evasion and change the adherence properties of the pilus. We have examined the process of pilin antigenic variation in human volunteers inoculated with strain FA1090. Our data show that pilin variation occurred throughout the process of infection, that at each time sampled after inoculation multiple pilin variants were present, and that later pilin variants appear to be recombinants between previously expressed genes and the silent storage pilin copies. Thus, during infection a large repertoire of proteins are available to the population to help avoid immune responses, to provide pili with varying functions, and to transmit to a new host.

Human Experimentation with Neisseria gonorrhoeae: Rationale, Methods, and Implications for the Biology of Infection and Vaccine Development

Abstract: Neisseria gonorrhoeae infection is limited to the human host. Experimental urethral infection in male volunteers was used to study different aspects of the infection. Urethral installation of a variety of gonococcal variants (10(4)-10(6)) led to infection in 27 subjects, who developed pyuria and shed bacteria in urine before urethritis developed 1-6 days after gonococcal inoculation. The incubation period was affected by the inoculation procedure and size of the inoculum. Subjects were treated with intramuscular ceftriaxone (250 mg) if urethritis developed or at 6 days after inoculation. Urine cultures became negative within several hours of therapy, and symptoms resolved within 1 day of therapy. Infected patients suffered no major complications. Experimental male urethral gonococcal infection provides a unique opportunity to understand the biology and immunology of gonococcal infection and is an efficient method to test gonococcal vaccine candidates.

Effects Of H2 O2-Producing Lactobacilli On Neisseria gonorrhoeae Growth and Activity

Abstract: In the vagina and endocervix, Neisseria gonorrhoeae must interact with complex microflora. Among these are lactobacilli, which may inhibit the growth of gonococci. Lactobacillus acidophilus, which produce H2O2 (LB+), and L. acidophilus and Lactobacillus casei, which do not produce H2O2 (LB-), were coincubated with catalase-positive and -deficient strains of N. gonorrhoeae. When the incubation medium was maintained at pH 7.3, neither LB+ nor LB- affected gonococcal growth. However, LB+ caused a significant increase in expression of gonococcal catalase, which could be offset by exposure of the bacteria to exogenous catalase. When coincubation medium was at lower pH (4.8-5.0), there was a significant decrease in gonococcal survival and catalase activity, which was only partly reversed by exogenous catalase. Lysates of LB+ also effectively inhibited gonococcal catalase. This inhibition was retained upon heating of the lysate to 100 degrees C for 15 min but was lost with proteinase K treatment. Thus, LB+ may inhibit growth of gonococci by acidification of the environment, secretion of H2O2, and production of protein inhibitors.

Detection and biologic characterization of infectious HIV-1 in semen of seropositive men

Abstract: OBJECTIVE Factors that influence the infectivity of an individual and the impact of antiviral treatment on infectivity are not well defined. This study investigated the value of a sensitive method for detecting infectious HIV in semen for use as a marker for infectivity. DESIGN A cross-sectional study of infectious HIV in the semen of 33 HIV-positive men. METHODS A sensitive method for detecting infectious HIV in semen was used. The correlation of culture in semen with clinical and laboratory data was investigated. Biological phenotypes of isolates from blood and semen were tested using an MT-2 assay. RESULTS HIV cultures from seminal cells were positive in 18 patients (55%) and in one patient from seminal plasma. Higher recovery rates of HIV from semen correlated with a low CD4 count (80% in patients with a CD4 count > 100 x 10(6)/l versus 33% in patients with a CD4 count < 100 x 10(6) cells; P < 0.025) and symptomatic disease (78 versus 27% in asymptomatic patients; P < 0.01). Recovery of HIV from semen was independent of presence or absence of plasma viremia and the biological phenotype of blood isolates. Ten patients with syncytium-inducing (SI) isolates in their blood had positive semen cultures for HIV. Seven of the 10 patients had SI isolates recovered from their semen, whereas three had non-SI isolates only. CONCLUSION Data from partner studies show higher rates of HIV transmission for patients with low CD4 counts and symptomatic disease. The compatibility of epidemiologic data with our finding that significantly more HIV is recovered in semen from patients with advanced disease, suggests that HIV culture of semen samples may provide a useful surrogate marker to measure infectivity in clinical studies. Further studies are needed to define the inoculum required to transmit HIV and to study the impact of sexually transmitted diseases and HIV-1 phenotype on semen infectivity.

Molecular events in the activation of human neutrophils for microbial killing

Abstract: Human neutrophils provide protection from a variety of microbes; neutropenia or neutrophil dysfunction can both have serious clinical consequences. Effective microbial killing involves attachment to blood vessel walls, transmigration into tissues, chemotaxis, and phagocytosis. The molecular mechanisms by which neutrophils kill microbes have been extensively dissected. Each of the cellular processes is initiated in response to the occupancy of unique surface receptors. Receptor occupancy is translated into specific cellular activities via such signals as activation of calcium-mediated protein kinases and phosphorylation of critical proteins. After phagocytosis, the engulfed particle is subjected to killing mechanisms, which include reactive oxygen species, acid pH, and antimicrobial proteins. A thorough understanding of these molecular events may allow the modulation of neutrophil activity.

The Role of Lactoferrin as an Anti-Inflammatory Molecule

Abstract: The formation of hydroxyl radical via the iron catalyzed Haber-Weiss reaction has been implicated in phagocyte-mediated microbicidal activity and inflammatory tissue injury. The fact that neutrophils contain lactoferrin and mononuclear phagocytes have the capacity to acquire exogenous iron has suggested that iron bound to lactoferrin may influence the nature of free radical products generated by these cells. Over the years the iron-lactoferrin complex has been heralded as both a promoter and inhibitor of hydroxyl radical formation. This manuscript is intended to provide an overview of work performed to date related to this controversy and to present results of a number of preliminary studies which shed further light on the role of lactoferrin in inflammation.

STD/HIV control in Malawi and the search for affordable and effective urethritis therapy: a first field evaluation.

Abstract: OBJECTIVES--To evaluate gonococcal (GU) and nongonococcal urethritis (NGU), chlamydia antigen, and serostatus for syphilis and human immunodeficiency virus (HIV) among males attending a Malawian STD clinic with complaints of urethral discharge and/or dysuria. To collect demographic and behavioural data and to determine the effectiveness of five treatments for urethritis. METHODS--Urethritis was diagnosed using microscopy and culture for Neisseria gonorrhoeae. Sera were screened with rapid plasma reagin (RPR) and if reactive, with microhaemagglutination for Treponema pallidum (MHA-TP). HIV antibodies and chlamydia antigen were detected using enzyme immunoassay. Patients were randomised for treatment, cure was assessed 8-10 days later. RESULTS--At enrolment, GU was diagnosed in 415 (80.3%) and NGU in 59 (11.2%) of 517 males. Chlamydia antigen was found in 26 (5.2%) of 497 specimens tested. Syphilis seropositivity rate (RPR and MHA-TP reactive) was 10.7%. Overall HIV seroprevalence was 44.2%; 71.7% of men with reactive syphilis serology were HIV(+) compared with 40.9% of syphilis seronegatives (OR: 3.6, p < 0.001). Trimethoprim 320 mg/sulphamethoxazole 1600 mg by mouth for 2 days (TMPSMX), or the combination of amoxicillin 3 gm, probenicid 1 gm, and clavulanate 125 mg by mouth once (APC), failed to cure gonorrhoea effectively. Amoxicillin 3 gm, probenicid 1 gm, and clavulanate 125 mg, by mouth once with doxycycline 100 mg BID for 7 days (APC-D), gentamicin 240 mg IM once (GENT), ciprofloxacin 250 mg by mouth once (CIPRO) cured 92.9% to 95% of gonorrhoea. APC-D treatment did not generate less NGU at follow-up. HIV serostatus did not affect cure of urethritis. CONCLUSION--All patients presenting with urethritis should be treated syndromically using a simple algorithm and screened for syphilis seroreactivity for appropriate treatment and counselling.

A new deal in HIV prevention: lessons from the global approach.

Abstract: We have now entered the second decade of the human immunodeficiency virus (HIV) pandemic. Medical science has responded to this new disease with remarkable dissection of the HIV virus and equally detailed descriptions of the clinical evolution of opportunistic infections and neoplasms in patients with the acquired immunodeficiency syndrome (AIDS). An entire industry has developed to address and improve strategies for the management of patients with HIV disease. Much of the funding for HIV research in the United States has focused on the development of vaccines [1] and antiviral therapy [2]. In essence, it was (and might still be) hoped that our technology can generate a magic bullet to end the AIDS epidemic. Although critically important, this approach has had no immediate effect on the spread of AIDS. An aggressive HIV prevention campaign was politically difficult, if not impossible, to initiate in the United States throughout the 1980s. Prevention of HIV requires detailed knowledge of who is at the greatest risk for disease; however, infected patients were threatened with loss of livelihood, health insurance, personal safety, and social support [3]. This social and political climate slowed our understanding of the spread of HIV and the scope of the epidemic. Although an HIV prevention campaign requires an effort to change sexual behavior, such a campaign would probably have offended and alienated some American voters. Efforts to promote condom education and use were frustrated at every level. Regardless of the clear-cut role of intravenous drug use in the HIV epidemic, drug rehabilitation programs were not expanded, and needle exchange programs were not federally funded. As a result of these and other problems, the public health community found itself constrained in its efforts to prevent HIV disease. These latter problems were summarized by Dr. Donald Francis in his farewell address to the Centers for Disease Control and Prevention [4] and dramatized by the book and movie And the Band Played On. Finally, the prevention of sexually transmitted diseases (STDs), which are now recognized to facilitate transmission of HIV, was not given high priority. Indeed, during the 1980s, the incidence and prevalence of all the treatable bacterial STDs (gonorrhea, chlamydial infection, syphilis, chancroid) and herpes simplex virus type 2 infection increased. By default, HIV control in the United States evolved to focus on the screening of blood donors and HIV testing and counseling. Most other countries (both industrialized and developing) have implemented more comprehensive HIV control programs. These are best exemplified in developing countries by the World Health Organization's Global Program on AIDS and the U.S. Agency for International Development's AIDS Control and Prevention Program, which is coordinated by Family Health International in more than 30 countries. The Clinton administration is likely to support a comprehensive HIV prevention plan for the United States as well as programs similar to those advocated by the Global Program on AIDS and the U.S. Agency for International Development. Our purpose is to describe these programs and to suggest some fundamental changes in addressing the STD problem in the United States. The Global Program on AIDS and the U.S. Agency for International Development strategies are designed to prevent sexual transmission of HIV with minimal dependence on technology and resources. The programs focus on three linked components: condom promotion and distribution, change in sexual behavior (delaying onset of intercourse by adolescents, avoidance of high-risk sexual practices, and partner number reduction), and control of those STDs that appear to facilitate the transmission of HIV [5]. Mathematical models of the AIDS pandemic strongly suggest that only concomitant implementation of these three strategies will maximally reduce the spread of HIV [6]. Accordingly, each of these goals deserves further discussion. Condoms can help to reduce the spread of STDs, including HIV infection [7]. However, condom distribution has evoked concern about the message sent by their availability [8]. It has been argued that the very act of making condoms available endorses promiscuous sex, especially for less mature (and potentially more easily confused) adolescents. This notion contrasts with data suggesting that sex education can reduce risky behavior in some adolescent populations [9]. Sexual behavior is complex and poorly understood. Experiments designed to better understand ways to change sexual behavior are in progress, and the results are critically important to the war on AIDS. The sexual behavior of a population can probably be changed only very slowly. Further, all Americans do not share the same risk for STD and HIV infection [10]. The continued spread of many STDs is dependent on high-risk groups whose sexual behaviors appear to allow at least some of these diseases to flourish [11]. Different groups can be expected to respond differently to new information and to efforts to change behavior. Campaigns against HIV and STDs are now becoming more focused on high-risk groups, although such targeting has stimulated serious controversy [12]. Available data strongly suggest that STDs that cause skin ulcers (genital herpes, syphilis, and chancroid) or mucosal inflammation (gonorrhea, chlamydial infection, and trichomoniasis) greatly facilitate HIV transmission [5, 13]. This finding is now popularly referred to as epidemiologic synergy [5]. Prevention of these classic STDs has become a high priority. Unfortunately, in developing countries, drugs to treat STDs are often not available. In the United States, STD care is tremendously hindered by inadequate staffing and overcrowding of public health clinics, where STD care has traditionally been delivered, and the lack of STD education for health care workers in the private sector. How did we get where we are? More than 30 years ago Surgeon General Thomas Parran helped to develop a U.S. public health infrastructure that shifted STD care and control to the public sector. These public health measures, combined with the use of effective antibiotics, led to a dramatic decrease in STDs. In 1954 the American Journal of Syphilis, Gonorrhoeae, and Venereal Diseases ceased publication after four successful decades, as a direct result of reduced interest. of physicians and medical students [14]. Changes in the 1950s led to at least two generations of physicians with little experience in STD treatment, risk assessment, or the public health aspects of STD case management. A 1982 survey of 127 medical schools in the United States and Canada showed that 87 offered no clinical teaching about STDs to students, and 96 offered no such training for residents [15]. We now anticipate the inception of a stronger and more comprehensive U.S. AIDS prevention program. This program offers a unique opportunity for practicing physicians. Given the movement toward managed care and preventive health care services, it appears likely that physicians in the private sector will play a greater role in the management of patients with STDs. Treatment of STDs must be comprehensive, and physicians will require more experience in treating STDs as well as strategies to work effectively with the public sector. The physician who recognizes one STD must look for others; he or she must treat partners and counsel the patient. Who will provide the education for the proper management of STDs? Medical schools are under tremendous pressure to teach their students how to manage primary care problems in outpatient settings [16]. Sexually transmitted disease clinics have a high volume of outpatients with interesting and important problems. We have had excellent experience with students and residents who choose to work in our STD clinics and who evaluate this experience very positively. Even before the AIDS epidemic began, several expert panels recommended that medical schools establish affiliations with STD treatment facilities so that medical students and physicians in training would have the opportunity for supervised clinical experience treating STDs [15]. This education is even more imperative now; it will be essential to enable private sector physicians to play a leading role in the new and improved war on STDs and HIV.

Variation in hydrogen peroxide sensitivity between different strains of Neisseria gonorrhoeae is dependent on factors in addition to catalase activity

Abstract: Catalase, which catalyzes the reduction of hydrogen peroxide to oxygen and water, is considered the primary defense of Neisseria gonorrhoeae against exogenous hydrogen peroxide. Recent reports have demonstrated drastically different sensitivities of the organism to hydrogen peroxide ranging from greater than 80% survival after challenge with 30 mM hydrogen peroxide to less than 0.001% survival after challenge with 10 mM hydrogen peroxide. In this study, we have examined the hydrogen peroxide sensitivities of six clinical gonococcal isolates. The study demonstrates that the variations in gonococcal hydrogen peroxide sensitivities previously reported can be attributed to (i) differences in experimental methods employed or (ii) variation among different gonococcal strains. All of the gonococcal isolates examined generated similar concentrations of catalase, implying that the differences in the H2O2 sensitivity observed may depend on factors in addition to catalase.