Identifying biomarkers of pollutant exposure in ocean sentinels: Characterisation and optimisation of B-esterases in plasma from loggerhead turtles undergoing rehabilitation

Sea turtles are frequently proposed as indicator species for assessing ocean health. To faciliate the use of these species as bioindicators requires the development of tools for rapidly and effectively assessing individual health. Here, we collected 104 blood samples from 69 loggerhead sea turtles, Caretta caretta, undergoing rehabilitation to determine the connection between health status, the activity of B-esterases, and other biochemical parameters. To determine the optimal assay protocol for B-esterases, we measured the activity and kinetics of cholinesterases-(ChEs) and carboxylesterases (CEs) using 3 and 5 commercial substrates, respectively, at different assay conditions. IC50 values for the activity of B-esterases were calculated within a concentration range for model pesticide inhibitors. Turtles' health status was determined via routine veterinary procedures. During rehabilitation (which was associated with improving health status), we observed a decrease in the activity of most enzymes (especially in acetylcholinesterase) alongside an increase in CE when using p-nitrophenyl acetate as a substrate. As such, it is possible that the activity rates of plasmatic B-esterases could serve as an indicator of health status. There is also high potential that B-esterases could be specifically sensitive to marine pollutants although to further validate this would require future studies to specifically correlate B-esterarse activities to pollutant concentrations in blood or excreta.

Amplification and Quantitation of Telomeric Extrachromosomal Circles

Telomeres are structures that cap the ends of linear chromosomes and play critical roles in maintaining genome integrity and establishing the replicative lifespan of cells. In stem and cancer cells, telomeres are actively elongated by either telomerase or the alternative lengthening of telomeres (ALT) pathway. This pathway is characterized by several hallmark features, including extrachromosomal C-rich circular DNAs that can be probed to assess ALT activity. These so-called C-circles are the product of ALT-associated DNA damage repair processes and simultaneously serve as potential templates for iterative telomere extension. This bifunctional nature makes C-circles highly sensitive and specific markers of ALT. Here, we describe a C-circle assay, adapted from previous reports, that enables the quantitation of C-circle abundance in mammalian cells subjected to a wide range of experimental perturbations. This protocol combines the Quick C-circle Preparation (QCP) method for DNA isolation with fluorometry-based DNA quantification, rolling circle amplification (RCA), and detection of C-circles using quantitative PCR. Moreover, the inclusion of internal standards with well-characterized telomere maintenance mechanisms (TMMs) allows for the reliable benchmarking of cells with unknown TMM status. Overall, our work builds upon existing protocols to create a generalizable workflow for in vitro C-circle quantitation and ascertainment of TMM identity.

The role of RNA processing and regulation in metastatic dormancy

Tumor dormancy is a major contributor to the lethality of metastatic disease, especially for cancer patients who develop metastases years-to-decades after initial diagnosis. Indeed, tumor cells can disseminate during early disease stages and persist in new microenvironments at distal sites for months, years, or even decades before initiating metastatic outgrowth. This delay between primary tumor remission and metastatic relapse is known as "dormancy," during which disseminated tumor cells (DTCs) acquire quiescent states in response to intrinsic (i.e., cellular) and extrinsic (i.e., microenvironmental) signals. Maintaining dormancy-associated phenotypes requires DTCs to activate transcriptional, translational, and post-translational mechanisms that engender cellular plasticity. RNA processing is emerging as an essential facet of cellular plasticity, particularly with respect to the initiation, maintenance, and reversal of dormancy-associated phenotypes. Moreover, dysregulated RNA processing, particularly that associated with alternative RNA splicing and expression of noncoding RNAs (ncRNAs), can occur in DTCs to mediate intrinsic and extrinsic metastatic dormancy. Here we review the pathophysiological impact of alternative RNA splicing and ncRNAs in promoting metastatic dormancy and disease recurrence in human cancers.

SLX4IP promotes RAP1 SUMOylation by PIAS1 to coordinate telomere maintenance through NF-κB and Notch signaling

The maintenance of telomere length supports repetitive cell division and therefore plays a central role in cancer development and progression. Telomeres are extended by either the enzyme telomerase or the alternative lengthening of telomeres (ALT) pathway. Here, we found that the telomere-associated protein SLX4IP dictates telomere proteome composition by recruiting and activating the E3 SUMO ligase PIAS1 to the SLX4 complex. PIAS1 SUMOylated the telomere-binding protein RAP1, which disrupted its interaction with the telomere-binding protein TRF2 and facilitated its nucleocytoplasmic shuttling. In the cytosol, RAP1 bound to IκB kinase (IKK), resulting in activation of the transcription factor NF-κB and its induction of Jagged-1 expression, which promoted Notch signaling and the institution of ALT. This axis could be targeted therapeutically in ALT-driven cancers and in tumor cells that develop resistance to antitelomerase therapies. Our results illuminate the mechanisms underlying SLX4IP-dependent telomere plasticity and demonstrate the role of telomere proteins in directly coordinating intracellular signaling and telomere maintenance dynamics.

Rehabilitated sea turtles tend to resume typical migratory behaviors: satellite tracking juvenile loggerhead, green, and Kemp’s ridley turtles in the northeastern USA

Wildlife rehabilitation programs are widely employed for many endangered marine species and can serve as engaging platforms for environmental outreach. However, their effectiveness at supporting populations in the wild depends on whether rescued animals can survive and reproduce after being released. Here, we assessed whether cold-stunned juvenile sea turtles resumed typical migratory and diving behaviors after rehabilitation. We deployed satellite transmitters onto 7 rehabilitated loggerhead turtles Caretta caretta, 12 green turtles Chelonia mydas, and 12 Kemp’s ridley turtles Lepidochelys kempii released around Long Island, New York, USA. Of these 31 turtles, 30 were tracked long enough to determine their migratory movements. The majority (83%) left Long Island before local waters dropped below 14°C and avoided being cold-stunned. Most individuals followed migratory routes previously reported for each of the 3 species, migrating to either coastal waters off the southeast USA or oceanic waters of the Gulf Stream. Rehabilitated turtles of each species also resumed typical diving patterns. Four of the remaining 5 turtles that did not migrate away from Long Island were likely cold-stunned again. Overall, most cold-stunned sea turtles tend to resume typical migratory and diving behavior post-rehabilitation.

Abstract 112: Telomere proteins coordinate intracellular signaling to control telomere maintenance mechanism selection and metastatic recurrence

The relationship between telomere homeostasis and the development of cancer remains incompletely understood. In breast cancer (BC), these knowledge gaps are magnified by the fact that distinct telomere maintenance mechanisms (TMMs) are utilized across different disease subtypes and stages of progression. Accordingly, we have found that TMM identity in BC possesses an inherent plasticity that portends important prognostic and therapeutic insight, events regulated in part by SLX4-interacting protein (SLX4IP). To better understand how SLX4IP regulates TMM identity in BC, we employed proteomics of isolated chromatin segments (PICh) to capture the telomere proteomes of BC cells harboring differential SLX4IP expression. These analyzes revealed that SLX4IP blocks recruitment of the shelterin protein telomere repeat-binding factor 2-interacting protein (TERF2IP, also known as RAP1) to telomeres. Moreover, telomeres lacking RAP1 were able to be extended via the homologous recombination-based Alternative Lengthening of Telomeres (ALT) pathway. Mechanistically, SLX4IP disrupted the interaction between RAP1 and telomere repeat-binding factor 2 (TRF2), which facilitated the nuclear export of RAP1 and its binding to and activation of the NF-κB regulatory kinase, IKKβ. Activated IKKβ phosphorylated both NF-κB and β-catenin, thereby coordinating a transcriptional network of genes that are essential in promoting ALT. Conversely, loss of SLX4IP yielded telomeric retention of RAP1 with concomitant diminution of IKKβ activity, resulting in β-catenin-dependent stimulation of telomerase. Notably, telomerase was sufficient to drive the metastatic outgrowth of cells that were previously reliant upon ALT independent of its ability to extend telomere DNA. These findings shed new light on the functions of SLX4IP and the myriad roles of telomere proteins in influencing TMM plasticity and disease progression.

Citation Format: Nathaniel J. Robinson, Derek J. Taylor, William P. Schiemann. Telomere proteins coordinate intracellular signaling to control telomere maintenance mechanism selection and metastatic recurrence [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 112.

Epigenetic plasticity in metastatic dormancy: mechanisms and therapeutic implications

The overwhelming majority of cancer-associated morbidity and mortality can be ascribed to metastasis. Metastatic disease frequently presents in a delayed fashion following initial diagnosis and treatment, requiring that disseminated cancer cells (DCCs) spread early in tumor progression and persist in a dormant state at metastatic sites. To accomplish this feat, DCCs exhibit substantial phenotypic plasticity that is mediated by the epigenetic regulation of dormancy programs in response to intrinsic (i.e., cellular) and extrinsic (i.e., microenvironmental) cues. The epigenome is a dynamic landscape that encompasses transcriptional regulation via alteration of chromatin architecture, posttranscriptional RNA processing, and the diverse functions carried out by noncoding RNAs. Signals converging on DCCs are transduced through epigenetic effectors. Conversely, epigenetic regulation of gene expression controls the crosstalk between DCCs and cells of the metastatic niche, a phenomenon that is essential for the institution of dormant phenotypes. Importantly, epigenetic effectors can be targeted therapeutically, and the development of novel epigenetic therapies may provide new inroads to combating recurrent metastatic disease. Here we provide an overview of the dynamics of metastatic dormancy and summarize our current understanding of the intersections between dormancy and the epigenome, both mechanistically and therapeutically.

SLX4IP and telomere dynamics dictate breast cancer metastasis and therapeutic responsiveness

An unbiased genetic screen established SLX4IP as an essential driver of telomere maintenance mechanism identity, metastatic progression, and therapeutic response of breast cancers.

Metastasis is the leading cause of breast cancer-related death and poses a substantial clinical burden owing to a paucity of targeted treatment options. The clinical manifestations of metastasis occur years-to-decades after initial diagnosis and treatment because disseminated tumor cells readily evade detection and resist therapy, ultimately giving rise to recurrent disease. Using an unbiased genetic screen, we identified SLX4-interacting protein (SLX4IP) as a regulator of metastatic recurrence and established its relationship in governing telomere maintenance mechanisms (TMMs). Inactivation of SLX4IP suppressed alternative lengthening of telomeres (ALT), coinciding with activation of telomerase. Importantly, TMM selection dramatically influenced metastatic progression and survival of patients with genetically distinct breast cancer subtypes. Notably, pharmacologic and genetic modulation of TMMs elicited telomere-dependent cell death and prevented disease recurrence by disseminated tumor cells. This study illuminates SLX4IP as a potential predictive biomarker for breast cancer progression and metastatic relapse. SLX4IP expression correlates with TMM identity, which also carries prognostic value and informs treatment selection, thereby revealing new inroads into combating metastatic breast cancers.

Stem cells, immortality, and the evolution of metastatic properties in breast cancer: telomere maintenance mechanisms and metastatic evolution

Breast cancer is the most significant cause of cancer-related death in women around the world. The vast majority of breast cancer-associated mortality stems from metastasis, which remains an incurable disease state. Metastasis results from evolution of clones that possess the insidious properties required for dissemination and colonization of distant organs. These clonal populations are descended from breast cancer stem cells (CSCs), which are also responsible for their prolonged maintenance and continued evolution. Telomeres impose a lifespan on cells that can be extended when they are actively elongated, as occurs in CSCs. Thus, changes in telomere structure serve to promote the survival of CSCs and subsequent metastatic evolution. The selection of telomere maintenance mechanism (TMM) has important consequences not only for CSC survival and evolution, but also for their coordination of various signaling pathways that choreograph the metastatic cascade. Targeting the telomere maintenance machinery may therefore provide a boon to the treatment of metastatic breast cancer. Here we review the two major TMMs and the roles they play in the development of stem and metastatic breast cancer cells. We also highlight current and future approaches to targeting these mechanisms in clinical settings to alleviate metastatic breast cancers.

A non-natural nucleotide uses a specific pocket to selectively inhibit telomerase activity

Telomerase, a unique reverse transcriptase that specifically extends the ends of linear chromosomes, is up-regulated in the vast majority of cancer cells. Here, we show that an indole nucleotide analog, 5-methylcarboxyl-indolyl-2'-deoxyriboside 5'-triphosphate (5-MeCITP), functions as an inhibitor of telomerase activity. The crystal structure of 5-MeCITP bound to the Tribolium castaneum telomerase reverse transcriptase reveals an atypical interaction, in which the nucleobase is flipped in the active site. In this orientation, the methoxy group of 5-MeCITP extends out of the canonical active site to interact with a telomerase-specific hydrophobic pocket formed by motifs 1 and 2 in the fingers domain and T-motif in the RNA-binding domain of the telomerase reverse transcriptase. In vitro data show that 5-MeCITP inhibits telomerase with a similar potency as the clinically administered nucleoside analog reverse transcriptase inhibitor azidothymidine (AZT). In addition, cell-based studies show that treatment with the cell-permeable nucleoside counterpart of 5-MeCITP leads to telomere shortening in telomerase-positive cancer cells, while resulting in significantly lower cytotoxic effects in telomerase-negative cell lines when compared with AZT treatment.

Measuring the success of canine and feline preventative healthcare consultations: A systematic review

Preventative healthcare consultations account for a large proportion of the veterinary caseload. This novel study is the first to methodically review all literature on canine and feline preventative healthcare consultations. Previous research has found these consultations to be different from health problem consultations in terms of communication style and content. Identifying relevant evidence and previously validated methods of measuring the success of these consultations will be useful when implementing strategies for optimisation. The aim of this study was to identify and assess the quality of existing literature which describes and/or measures the success of preventative healthcare consultations. Database searches of CAB Abstracts and Medline were conducted to identify published literature. Google searches were then conducted to identify any additional published or grey literature. Results were systematically screened to determine whether the returned sources were about cats and/or dogs, whether they related to preventative healthcare, and whether they described and/or measured the success of preventative healthcare consultations. For primary research citations which only described preventative healthcare consultations, data were extracted on the aspects of the consultations described. For citations which additionally measured the success of the consultations, the measures used, sampling technique, key results and key weaknesses were also extracted. Of 17,538 citations identified in total during the database searches, a total of seven relevant primary research citations were identified. All of these citations described aspects of the preventative healthcare consultation, such as consultation length, health problems discussed, actions taken and communication style. Only one primary research citation measured success of the consultation, using veterinarian satisfaction to determine success. In addition, 30 narrative citations, including expert opinion pieces, textbooks, guidelines without transparent methodology and conference presentations were identified. Google searches identified 224 relevant narrative citations, and five of the seven primary research citations identified by the database searches, but did not identify any additional relevant primary research citations. The results suggest that, despite accounting for around a third of all consultations, there is relatively little evidence describing preventative healthcare consultations and only one measure of success has been described for these consultations. This presents potential challenges when implementing strategies to optimise these consultations, as measures which are useful and relevant to veterinary practice should first be identified. Identifying useful measures of success will allow future strategies designed to maximise the benefits of these consultations to be meaningfully assessed for efficacy.

Factors influencing common diagnoses made during first-opinion small-animal consultations in the United Kingdom

It is currently unclear how frequently a diagnosis is made during small-animal consultations or how much of a role making a diagnosis plays in veterinary decision-making. Understanding more about the diagnostic process will help direct future research towards areas relevant to practicing veterinary surgeons. The aim of this study was to determine the frequency with which a diagnosis was made, classify the types of diagnosis made (and the factors influencing these) and determine which specific diagnoses were made for health problems discussed during small-animal consultations. Data were gathered during real-time direct observation of small-animal consultations in eight practices in the United Kingdom. Data collected included characteristics of the consultation (e.g. consultation type), patient (e.g. breed), and each problem discussed (e.g. new or pre-existing problem). Each problem discussed was classified into one of the following diagnosis types: definitive; working; presumed; open; previous. A three-level multivariable logistic-regression model was developed, with problem (Level 1) nested within patient (Level 2) nested within consulting veterinary surgeon (Level 3). Problems without a previous diagnosis, in cats and dogs only, were included in the model, which had a binary outcome variable of definitive diagnosis versus no definitive diagnosis. Data were recorded for 1901 animals presented, and data on diagnosis were gathered for 3192 health problems. Previous diagnoses were the most common diagnosis type (n=1116/3192; 35.0%), followed by open (n=868/3192; 27.2%) then definitive (n=660/3192; 20.7%). The variables remaining in the final model were patient age, problem history, consultation type, who raised the problem, and body system affected. New problems, problems in younger animals, and problems raised by the veterinary surgeon were more likely to result in a definitive diagnosis than pre-existing problems, problems in older animals, and problems raised by the owner. The most common diagnoses made were overweight/obese and periodontal disease (both n=210; 6.6%). Definitive diagnoses are rarely made during small-animal consultations, with much of the veterinary caseload involving management of ongoing problems or making decisions around new problems prior to a diagnosis being made. This needs to be taken into account when considering future research priorities, and it may be necessary to conduct research focused on the approach to common clinical presentations, rather than purely on the common diagnoses made. Examining how making a diagnosis affects the actions taken during the consultation may shed further light on the role of diagnosis in the clinical decision-making process.

Investigating preventive-medicine consultations in first-opinion small-animal practice in the United Kingdom using direct observation

Preventive-medicine consultations account for a large proportion of the veterinary caseload and previous research has suggested these consultations are fundamentally different from those in which the animal is presented for a specific health problem. There has been recent controversy around some aspects of preventive medicine for cats and dogs, and the full health benefits of the preventive-medicine consultation remain unclear. The aim of this study was to compare characteristics of the consultation and the problems discussed during the consultation between preventive-medicine consultations and other types of consultations. Data were gathered during direct observation of small-animal consultations in seven first-opinion practices in the United Kingdom. Data collected included type of clinical examination performed, patient signalment, and details of all problems discussed (including whether the problem was presenting or non-presenting, new or pre-existing, who had raised the problem, body system affected and whether an action was taken). A two-level multivariable logistic-regression model was developed, with canine and feline patients at Level 1 nested within consulting veterinary surgeons at Level 2, and a binary outcome variable of preventive-medicine consultation versus specific health-problem consultation. A total of 1807 patients were presented, of which 690 (38.2%) presented for a preventive-medicine consultation. Dogs were the most frequently presented species (n=1168; 64.6%) followed by cats (n=510; 28.2%), rabbits (n=86; 4.8%) and patients of other species (n=43; 2.4%). The five variables remaining in the multi-level model were whether multiple patients were presented, patient age, clinical examination type, weighing and number of problems discussed. Species, breed, sex, neutering status and practice did not remain in the final model. Many non-presenting problems, including both preventive-medicine problems and specific-health problems, were discussed and acted upon during all types of consultations. Dental and behavioural non-presenting problems were discussed more frequently during preventive-medicine consultations compared with specific health-problem consultations. Preventive-medicine consultations represent an opportunity for veterinary surgeons to discuss other aspects of preventive medicine, and to detect and manage new and ongoing health problems. A greater evidence base is needed to understand whether detecting and managing underlying disease during the preventive-medicine consultation has a positive impact on lifelong patient health and welfare.

Investigating common clinical presentations in first opinion small animal consultations using direct observation

Understanding more about the clinical presentations encountered in veterinary practice is vital in directing research towards areas relevant to practitioners. The aim of this study was to describe all problems discussed during a convenience sample of consultations using a direct observation method. A data collection tool was used to gather data by direct observation during small animal consultations at eight sentinel practices. Data were recorded for all presenting and non-presenting specific health problems discussed. A total of 1901 patients were presented with 3206 specific health problems discussed. Clinical presentation varied widely between species and between presenting and non-presenting problems. Skin lump, vomiting and inappetence were the most common clinical signs reported by the owner while overweight/obese, dental tartar and skin lump were the most common clinical examination findings. Skin was the most frequently affected body system overall followed by non-specific problems then the gastrointestinal system. Consultations are complex, with a diverse range of different clinical presentations seen. Considering the presenting problem only may give an inaccurate view of the veterinary caseload, as some common problems are rarely the reason for presentation. Understanding the common diagnoses made is the next step and will help to further focus questions for future research.

Capturing the complexity of first opinion small animal consultations using direct observation

Various different methods are currently being used to capture data from small animal consultations. The aim of this study was to develop a tool to record detailed data from consultations by direct observation. A second aim was to investigate the complexity of the consultation by examining the number of problems discussed per patient. A data collection tool was developed and used during direct observation of small animal consultations in eight practices. Data were recorded on consultation type, patient signalment and number of problems discussed. During 16 weeks of data collection, 1901 patients were presented. Up to eight problems were discussed for some patients; more problems were discussed during preventive medicine consultations than during first consultations (P<0.001) or revisits (P<0.001). Fewer problems were discussed for rabbits than cats (P<0.001) or dogs (P<0.001). Age was positively correlated with discussion of specific health problems and negatively correlated with discussion of preventive medicine. Consultations are complex with multiple problems frequently discussed, suggesting comorbidity may be common. Future research utilising practice data should consider how much of this complexity needs to be captured, and use appropriate methods accordingly. The findings here have implications for directing research and education as well as application in veterinary practice.

Excess risk of hip fractures attributable to the use of antidepressants in five European countries and the USA

SUMMARY

The association between antidepressant use and hip fracture remains unclear. We conducted a systematic review to estimate Population Attributable Risks (PAR) for France, Germany, Italy, Spain, UK, and the USA. We report a heterogeneous prevalence of antidepressant use and related PARs, both lowest for Italy and highest for the USA.

INTRODUCTION

Antidepressant use has been associated with an increased hip fracture risk in observational studies. However, the potential contribution of antidepressant consumption on the population rate of hip fractures has not been described. Our aim was to estimate the impact of the use of different classes of antidepressants on the rate of hip fracture at a population-level in France, Germany, Italy, Spain, the UK, and the USA.

METHODS

We conducted a systematic literature review to estimate the pooled relative risk (RR) of hip fracture according to use of antidepressants. Prevalence rates of antidepressant use (Pe) in 2009 were calculated for each country using the The Intercontinental Medical Statistics database and three public databases from Denmark, the Netherlands, and Norway. Both the RR and Pe were used to calculate PAR of hip fractures associated with antidepressant use.

RESULTS

The literature review showed an increased risk of hip fractures in antidepressant users (RR, 1.7; 95 % confidence interval (CI), 1.5-2.0). Rates of antidepressant use showed considerable differences between countries, ranging from 4.4 % (Italy) to 11.2 % (USA) in the year 2009. The estimated PAR of antidepressants on hip fracture rates were 3.0 % (95 % CI, 2.0-4.1; Italy), 3.1 % (95 % CI, 2.1-4.3; Germany), 3.8 % (95 % CI, 2.6-5.3; France), 4.8 % (95 % CI, 3.3-6.5; Spain), 4.9 % (95 % CI, 3.4-6.8; UK), and 7.2 % (95 % CI, 5.0-9.9; USA). PARs differed for different types of antidepressants, with highest attributable risks for selective serotonin reuptake inhibitors.

CONCLUSIONS

These findings suggest that the potential contribution of antidepressant use to the population rate of hip fractures in the five large EU countries and the USA varies between 3 and 7 %.

Survey of the UK veterinary profession: common species and conditions nominated by veterinarians in practice

The practice of evidence-based veterinary medicine involves the utilisation of scientific evidence for clinical decision making. To enable this, research topics pertinent to clinical practice need to be identified, and veterinary clinicians are best placed to do this. The main aim of this study was to describe the veterinary population, the common species and conditions veterinary clinicians nominated they saw in practice and how much information clinicians perceived was available in the literature for these. A questionnaire was distributed to all Royal College of Veterinary Surgeons registered veterinarians agreeing to be contacted for research purposes (n=14,532). A useable response rate of 33 per cent (4842/14,532) was achieved. The most commonly seen species reported by vets were dogs, cats and rabbits followed by equines and cattle. Overall, skin conditions were most commonly mentioned for small animals, musculoskeletal conditions for equines and reproduction conditions for production animals. Veterinary clinicians perceived there was a higher level of information available in the literature for conditions in dogs, cattle and equines and lower levels for rabbits and guinea pigs. The results from this study can be used to help define the research needs of the profession to aid the incorporation of evidence in veterinary practice.

Sexual behaviour and condom use among individuals with a history of symptomatic genital herpes

OBJECTIVES

This study describes the differences in sexual behaviour in individuals with genital herpes (GH) during "symptomatic" and "asymptomatic" periods of the disease.

METHODS

A cross sectional questionnaire was undertaken by 1193 individuals attending clinics between 1998 and 2001. All participants in this analysis were in heterosexual, monogamous partnerships, self identified with a history of symptomatic GH and with confirmed HSV-2 infection.

RESULTS

Sexual activity reported during asymptomatic v symptomatic periods of GH was 98% v 40% (p<0.001), 76% v 29% (p<0.001), and 25% v 11% (p<0.001) for vaginal, oral, and anal intercourse, respectively, while "always" condom use during asymptomatic and symptomatic periods was 20% v 35% (p<0.001), 2% v 7% (p<0.001), and 10% v 15% (p = 0.131), respectively. The proportion of individuals who either abstained from vaginal intercourse or "always" used condoms was 21% v 74% (p<0.001), for asymptomatic v symptomatic periods. Multivariable analyses indicated that factors associated with engaging in intercourse during symptomatic periods of GH included current intrauterine device use (adjusted odds ratio (aOR) = 2.96, 95% confidence interval (CI) = 1.46 to 6.02); living in Latin America (aOR = 2.16, CI = 1.19 to 3.91) or Europe (aOR = 1.67, CI = 1.21 to 2.28), compared with North America; previous sexually transmitted disease (aOR = 1.42, CI = 1.08 to 1.89); a higher number of sexual acts per month (aOR = 1.09, CI = 1.06 to 1.11); and a higher number of GH recurrences per year (aOR = 1.08, CI = 1.03 to 1.12).

CONCLUSIONS

These data indicate that the majority of people with GH either abstained from intercourse or "always" used condoms during symptomatic periods of GH. However, condom use was relatively low during asymptomatic periods in comparison with symptomatic periods. These results highlight that further education on GH prevention is warranted, particularly for symptomatic periods.

Adolescent sexuality and the HIV epidemic in Yaoundé, Cameroon

Adolescents are the focus of many interventions that aim to prevent HIV transmission. In order for these interventions to be effective, it is essential to understand adolescents' sexual behaviour. Using data collected in Yaoundé, Cameroon, in 1997, the study analysed risk exposure and HIV prevalence among 426 men and 510 women aged 15-24. Although risky behaviours seem to be more prevalent among young men, their HIV prevalence remains under 1%. In contrast, HIV prevalence is high among young women (7.5%), even those who report having had few sexual partners. Mixing patterns among sexual partners, and especially the age difference between men and women, do not seem to be sufficient to explain the large male-female discrepancy in HIV prevalence that is evident in these data. The results are therefore probably due to a greater susceptibility to infection of young women than men. This study highlights the necessity of reinforcing prevention campaigns among youth and fighting the obstacles that continue to impede the use of condoms in this population.

Performance of focus ELISA tests for herpes simplex virus type 1 (HSV-1) and HSV-2 antibodies among women in ten diverse geographical locations

To determine the sensitivity and specificity of Focus HerpeSelect ELISAs, sera or plasma samples from women aged 18-55 years were collected in ten cities from eight countries and tested by HerpeSelect HSV-1 ELISA (Focus-HSV-1) and by HerpeSelect HSV-2 ELISA (Focus-HSV-2). Sera with Focus-HSV-2-positive results were retested; 94% of the 3617 samples retested were positive. A subset of sera from each site was then selected, based on the HSV-2 results, and tested by Western blot (WB). The sensitivity and specificity were determined with samples from ten sites (n = 967) for Focus-HSV-1 and from seven sites (n = 675) for Focus-HSV-2. Focus-HSV-1 and WB results were concordant (both negative or both positive) for 97% of samples, with 99% sensitivity and 77% specificity. Specimens from Songkla, Thailand had 84% concordance with WB results for HSV-1, while three other sites had 100% concordance. Concordance of Focus-HSV-2 and WB was 92%, with 97% sensitivity and 89% specificity. Ibadan, Nigeria had 78% concordance. Focus-HSV-2 sensitivity and specificity in sites other than Ibadan were 97% and 93%, respectively. Raising the positive cut-off index value for HSV-2 from 1.1 to 3.5 yielded a sensitivity of 90% and a specificity of 96%. A sensitivity of 90% and a specificity of 98% were achieved for sites other than Nigeria with the higher cut-off. In summary, the sensitivity and specificity of the Focus-HSV-1 and Focus-HSV-2 tests varied by site. Performance data generated in one area may not be applicable to other populations.

Seroepidemiological study of herpes simplex virus types 1 and 2 in Brazil, Estonia, India, Morocco, and Sri Lanka

BACKGROUND

The association between herpes simplex virus type 2 (HSV-2) and human immunodeficiency virus (HIV) and the development of HSV vaccines have increased interest in the study of HSV epidemiology.

OBJECTIVES

To estimate the age and sex specific seroprevalence of HSV-1 and HSV-2 infections in selected populations in Brazil, Estonia, India, Morocco, and Sri Lanka.

METHODS

Serum samples were collected from various populations including children, antenatal clinic attenders, blood donors, hospital inpatients, and HIV sentinel surveillance groups. STD clinic attenders were enrolled in Sri Lanka, male military personnel in Morocco. Sera were tested using a common algorithm by type specific HSV-1 and HSV-2 antibody assay.

RESULTS

13,986 samples were tested, 45.0% from adult females, 32.7% from adult males, and 22.3% from children. The prevalence of HSV-1 varied by site ranging from 78.5%-93.6% in adult males and from 75.5%-97.8% in adult females. In all countries HSV-1 seroprevalence increased significantly with age (p<0.001) in both men and women. The prevalence of HSV-2 infection varied between sites. Brazil had the highest age specific rates of infection for both men and women, followed by Sri Lanka for men and Estonia for women, the lowest rates being found in Estonia for men and India for women. In all countries, HSV-2 seroprevalence increased significantly with age (p<0.01) and adult females had higher rates of infection than adult males by age of infection.

CONCLUSIONS

HSV-1 and HSV-2 seroprevalence was consistently higher in women than men, particularly for HSV-2. Population based data on HSV-1 and HSV-2 will be useful for designing potential HSV-2 vaccination strategies and for focusing prevention efforts for HSV-1 and HSV-2 infection.

Herpes simplex virus type 2 and heterosexual spread of human immunodeficiency virus infection in developing countries: hypotheses and research priorities

Herpes simplex virus type 2 (HSV-2) infection is almost always sexually transmitted, and causes genital ulceration. Significant progress in our understanding of HSV infection has occurred over the last decade, in part related to the development of accurate and sensitive laboratory tests to study HSV-2. The application of PCR and type-specific serology to individual cases and in population-based studies has enabled the identification of a potentially important role for HSV-2 infection as a cofactor in the sexual transmission of HIV. This is a particular issue in developing countries. This review describes the epidemiology of HSV-2 infection in the HIV era, the hypotheses regarding HSV-HIV interactions, and research priorities for the developing world.

Microbial metallothioneins

Bacterial metallothioneins bind, sequester and buffer excess intracellular zinc. At present, the vast majority of the available experimental data relate to cyanobacterial metallothionein, SmtA, from Synechococcus PCC 7942. SmtA is required for normal resistance to zinc and smtA-mediated zinc resistance has been used as a selectable marker. The imidazole groups of histidine residues, in addition to the thiol groups of cysteine residues, co-ordinate zinc in bacterial metallothioneins. The structure of bacterial metallothionein must facilitate some discrimination between 'adventitious' and 'adventageous' zinc-binding sites such that under excess zinc conditions metal is predominantly scavenged from the former. It remains unclear whether or not bacterial metallothionein also acts as a zinc store that supplies zinc-requiring proteins or if under some conditions it deactivates a subset of proteins via zinc removal. Expression of smtA is induced in response to elevated concentrations of zinc via the action of SmtB. SmtB has some sequence similarity to the arsenic responsive repressor ArsR and genes encoding related proteins are present in many bacterial genomes. Metal perception by SmtB differs from ArsR. The latter contains a characteristic Cys-Val-Cys motif associated with a DNA-binding helix-turn-helix (the ArsR motif), while the former contains metal-binding motifs associated with a carboxyl-terminal alpha-helix that forms the interface between SmtB dimers (the SmtB motif). Some SmtB-ArsR family proteins, including the zinc sensor ZiaR from the cyanobacterium Synechocystis PCC 6803, have the metal-sensory motifs of both SmtB and ArsR. The mechanisms of action, and the features that allow discrimination between different metal ions by these sensors, are discussed.

A metallothionein containing a zinc finger within a four-metal cluster protects a bacterium from zinc toxicity

Zinc is essential for many cellular processes, including DNA synthesis, transcription, and translation, but excess can be toxic. A zinc-induced gene, smtA, is required for normal zinc-tolerance in the cyanobacterium Synechococcus PCC 7942. Here we report that the protein SmtA contains a cleft lined with Cys-sulfur and His-imidazole ligands that binds four zinc ions in a Zn(4)Cys(9)His(2) cluster. The thiolate sulfurs of five Cys ligands provide bridges between the two ZnCys(4) and two ZnCys(3)His sites, giving two fused six-membered rings with distorted boat conformations. The inorganic core strongly resembles the Zn(4)Cys(11) cluster of mammalian metallothionein, despite different amino acid sequences, a different linear order of the ligands, and presence of histidine ligands. Also, SmtA contains elements of secondary structure not found in metallothioneins. One of the two Cys(4)-coordinated zinc ions in SmtA readily exchanges with exogenous metal ((111)Cd), whereas the other is inert. The thiolate sulfur ligands bound to zinc in this site are buried within the protein. Regions of beta-strand and alpha-helix surround the inert site to form a zinc finger resembling the zinc fingers in GATA and LIM-domain proteins. Eukaryotic zinc fingers interact specifically with other proteins or DNA and an analogous interaction can therefore be anticipated for prokaryotic zinc fingers. SmtA now provides structural proof for the existence of zinc fingers in prokaryotes, and sequences related to the zinc finger motif can be identified in several bacterial genomes.

Ecological and individual level analysis of risk factors for HIV infection in four urban populations in sub-Saharan Africa with different levels of HIV infection

OBJECTIVE

To identify factors that could explain differences in rate of spread of HIV between different regions in sub-Saharan Africa.

DESIGN

Cross-sectional study.

METHODS

The study took place in two cities with a relatively low HIV prevalence (Cotonou, Benin and Yaoundé, Cameroon), and two cities with a high HIV prevalence (Kisumu, Kenya and Ndola, Zambia). In each of these cities, a representative sample was taken of about 1000 men and 1000 women aged 15-49 years. Consenting men and women were interviewed about their socio-demographic background and sexual behaviour; and were tested for HIV, herpes simplex virus type 2 (HSV-2), syphilis, Chlamydia trachomatis and Neisseria gonorrhoea infection, and (women only) Trichomonas vaginalis. Analysis of risk factors for HIV infection was carried out for each city and each sex separately. Adjusted odds ratios (aOR) were obtained by multivariate logistic regression.

RESULTS

The prevalence of HIV infection in sexually active men was 3.9% in Cotonou, 4.4% in Yaoundé, 21.1% in Kisumu, and 25.4% in Ndola. For women, the corresponding figures were 4.0, 8.4, 31.6 and 35.1%. High-risk sexual behaviour was not more common in the high HIV prevalence cities than in the low HIV prevalence cities, but HSV-2 infection and lack of circumcision were consistently more prevalent in the high HIV prevalence cities than in the low HIV prevalence cities. In multivariate analysis, the association between HIV infection and sexual behavioural factors was variable across the four cities. Syphilis was associated with HIV infection in Ndola in men [aOR = 2.7, 95% confidence interval (CI) = 1.5-4.91 and in women (aOR = 1.7, 95% CI = 1.1-2.6). HSV-2 infection was strongly associated with HIV infection in all four cities and in both sexes (aOR ranging between 4.4 and 8.0). Circumcision had a strong protective effect against the acquisition of HIV by men in Kisumu (aOR = 0.25, 95% CI = 0.12-0.52). In Ndola, no association was found between circumcision and HIV infection but sample sizes were too small to fully adjust for confounding.

CONCLUSION

The strong association between HIV and HSV-2 and male circumcision, and the distribution of the risk factors, led us to conclude that differences in efficiency of HIV transmission as mediated by biological factors outweigh differences in sexual behaviour in explaining the variation in rate of spread of HIV between the four cities.

The epidemiology of gonorrhoea, chlamydial infection and syphilis in four African cities

OBJECTIVES

To compare the epidemiology of gonorrhoea, chlamydial infection and syphilis in four cities in sub-Saharan Africa; two with a high prevalence of HIV infection (Kisumu, Kenya and Ndola, Zambia), and two with a relatively low HIV prevalence (Cotonou, Benin and Yaoundé, Cameroon).

DESIGN

Cross-sectional study, using standardized methods, including a standardized questionnaire and standardized laboratory tests, in four cities in sub-Saharan Africa.

METHODS

In each city, a random sample of about 2000 adults aged 15-49 years was taken. Consenting men and women were interviewed about their socio-demographic characteristics and their sexual behaviour, and were tested for HIV, syphilis, herpes simplex virus type 2 (HSV-2), gonorrhoea, chlamydial infection, and (women only) Trichomonas vaginalis infection. Risk factor analyses were carried out for chlamydial infection and syphilis seroreactivity.

RESULTS

The prevalence of gonorrhoea ranged between 0% in men in Kisumu and 2.7% in women in Yaoundé. Men and women in Yaoundé had the highest prevalence of chlamydial infection (5.9 and 9.4%, respectively). In the other cities, the prevalence of chlamydial infection ranged between 1.3% in women in Cotonou and 4.5% in women in Kisumu. In Ndola, the prevalence of syphilis seroreactivity was over 10% in both men and women; it was around 6% in Yaoundé, 3-4% in Kisumu, and 1-2% in Cotonou. Chlamydial infection was associated with rate of partner change for both men and women, and with young age for women. At the population level, the prevalence of chlamydial infection correlated well with reported rates of partner change. Positive syphilis serology was associated with rate of partner change and with HSV-2 infection. The latter association could be due to biological interaction between syphilis and HSV-2 or to residual confounding by sexual behaviour. At the population level, there was no correlation between prevalence of syphilis seroreactivity and reported rates of partner change.

CONCLUSION

Differences in prevalence of chlamydial infection could be explained by differences in reported sexual behaviour, but the variations in prevalence of syphilis seroreactivity remained unexplained. More research is needed to better understand the epidemiology of sexually transmitted infections in Africa.

Multicentre study on factors determining differences in rate of spread of HIV in sub-Saharan Africa: methods and prevalence of HIV infection

OBJECTIVE

The objective of this study was to explore whether the differences in rate of spread of HIV in different regions in sub-Saharan Africa could be explained by differences in sexual behaviour and/or factors influencing the probability of HIV transmission during sexual intercourse.

METHODS

A cross-sectional, population-based study was conducted in two cities with a high HIV prevalence (Kisumu in Kenya and Ndola in Zambia) and two cities with a relatively low HIV prevalence (Cotonou in Benin and Yaoundé in Cameroon). In each of these cities, approximately 1000 men and 1000 women, aged 15-49 years, were randomly selected from the general population. Consenting men and women were interviewed and were tested for HIV, syphilis, herpes simplex virus type 2 (HSV-2), gonorrhoea, chlamydial infection and trichomoniasis (the latter for women only). In addition, a survey was conducted on a random sample of 300 sex workers in each city. The research instruments, including the questionnaires and the laboratory procedures, were standardized to permit comparison of results.

RESULTS

The numbers of men interviewed were 1021 in Cotonou, 973 in Yaoundé, 829 in Kisumu, and 720 in Ndola. The corresponding figures for women were 1095, 1116, 1060 and 1130. In Yaoundé, Kisumu and Ndola, the response rates for men were lower than for women due to failure to make contact with eligible men. The proportion of eligible women who were interviewed was 86% in Yaoundé, and 89% in Kisumu and Ndola. In Yaoundé, 76% of eligible men were interviewed, along with 82% in Kisumu and 75% in Ndola. The prevalence of HIV infection in men was 3.3% in Cotonou, 4.1% in Yaoundé, 19.8% in Kisumu and 23.2% in Ndola. For women, the respective figures were 3.4, 7.8, 30.1 and 31.9%. The prevalence of HIV infection among women aged 15-19 years was 23.0% in Kisumu and 15.4% in Ndola. Among women in Kisumu who had their sexual debut 5 years before the interview, the prevalence of HIV infection was 46%; in Ndola, it was 59%. Among sex workers, the prevalence of HIV infection was 57.5% in Cotonou, 34.4% in Yaoundé, 74.7% in Kisumu and 68.7% in Ndola.

CONCLUSIONS

The HIV prevalence rates in the general population confirmed our preliminary assessment of the level of HIV infection in the four cities, which was based on estimates of HIV prevalence from sentinel surveillance among pregnant women. The very high prevalence of HIV infection among young women in Kisumu and Ndola calls for urgent intervention.

The epidemiology of HSV-2 infection and its association with HIV infection in four urban African populations

OBJECTIVES

To estimate age- and sex-specific herpes simplex virus type-2 (HSV-2) prevalence in urban African adult populations and to identify factors associated with infection.

DESIGN AND METHODS

Cross-sectional, population-based samples of about 2000 adults interviewed in each of the following cities: Cotonou, Benin; Yaoundé, Cameroon; Kisumu, Kenya and Ndola, Zambia. Consenting study participants were tested for HIV, HSV-2 and other sexually transmitted infections.

RESULTS

HSV-2 prevalence was over 50% among women and over 25% among men in Yaoundé, Kisumu and Ndola, with notably high rates of infection among young women in Kisumu and Ndola (39% and 23%, respectively, among women aged 15-19 years). The prevalence in Cotonou was lower (30% in women and 12% in men). Multivariate analysis showed that HSV-2 prevalence was significantly associated with older age, ever being married, and number of lifetime sexual partners, in almost all cities and both sexes. There was also a strong, consistent association with HIV infection. Among women, the adjusted odds ratios for the association between HSV-2 and HIV infections ranged from 4.0 [95% confidence interval (CI) = 2.0-8.0] in Kisumu to 5.5 (95% CI = 1.7-18) in Yaoundé, and those among men ranged from 4.6 (95% CI = 2.7-7.7) in Ndola to 7.9 (95% CI = 4.1-15) in Kisumu.

CONCLUSIONS

HSV-2 infection is highly prevalent in these populations, even at young ages, and is strongly associated with HIV at an individual level. At a population level, HSV-2 prevalence was highest in Kisumu and Ndola, the cities with the highest HIV rates, although rates were also high among women in Yaoundé, where there are high rates of partner change but relatively little HIV infection. The high prevalence of both infections among young people underlines the need for education and counselling among adolescents.

The epidemiology of trichomoniasis in women in four African cities

OBJECTIVES

To describe the epidemiology of Trichomonas vaginalis infection and its association with HIV infection, in women in four African cities with different levels of HIV infection.

DESIGN

Cross-sectional study, using standardized methods, including a standardized questionnaire and standardized laboratory tests, in four cities in sub-Saharan Africa: two with a high prevalence of HIV infection (Kisumu, Kenya and Ndola, Zambia), and two with a relatively low prevalence of HIV (Cotonou, Benin and Yaoundé, Cameroon).

METHODS

In each city, a random sample of about 2000 adults aged 15-49 years was taken. Consenting men and women were interviewed about their socio-demographic characteristics and their sexual behaviour, and were tested for HIV, syphilis, herpes simplex virus type 2 (HSV-2), gonorrhoea, chlamydial infection, and (women only) T. vaginalis infection. Risk factor analyses were carried out for trichomoniasis for each city separately. Multivariate analysis, however, was only possible for Yaoundé, Kisumu and Ndola.

RESULTS

The prevalence of trichomoniasis was significantly higher in the high HIV prevalence cities (29.3% in Kisumu and 34.3% in Ndola) than in Cotonou (3.2%) and Yaoundé (17.6%). Risk of trichomoniasis was increased in women who reported more lifetime sex partners. HIV infection was an independent risk factor for trichomonas infection in Yaoundé [adjusted odds ratio (OR) = 1.8, 95% confidence interval (CI) = 0.9-3.7] and Kisumu (adjusted OR = 1.7, 95% CI = 1.1-2.7), but not in Ndola. A striking finding was the high prevalence (40%) of trichomonas infection in women in Ndola who denied that they had ever had sex.

CONCLUSION

Trichomoniasis may have played a role in the spread of HIV in sub-Saharan Africa and may be one of the factors explaining the differences in levels of HIV infection between different regions in Africa. The differences in prevalence of trichomoniasis between the four cities remain unexplained, but we lack data on the epidemiology of trichomoniasis in men. More research is required on the interaction between trichomoniasis and HIV infection, the epidemiology of trichomoniasis in men, and trichomonas infections in women who deny sexual activity.

Two Menkes-type atpases supply copper for photosynthesis in Synechocystis PCC 6803

Synechocystis PCC 6803 contains four genes encoding polypeptides with sequence features of CPx-type ATPases, two of which are now designated pacS and ctaA. We show that CtaA and PacS (but not the related transporters, ZiaA or CoaT) facilitate switching to the use of copper (in plastocyanin) as an alternative to iron (in cytochrome c(6)) for the carriage of electrons within the thylakoid lumen. Disruption of pacS reduced copper tolerance but enhanced silver tolerance, and pacS-mediated restoration of copper tolerance was used to select transformants. Disruption of ctaA caused no change in copper tolerance but reduced the amount of copper cell(-1). In cultures supplemented with 0.2 microm copper, photooxidation of cytochrome c(6) (PetJ) was depressed in wild-type cells but remained elevated in both Synechocystis PCC 6803(ctaA) and Synechocystis PCC 6803(pacS). Conversely, plastocyanin transcripts (petE) were less abundant in both mutants at this [copper]. Synechocystis PCC 6803(ctaA) and Synechocystis PCC 6803(pacS) showed increased iron dependence with impaired growth in deferoxamine mesylate (iron chelator)-containing media. Double mutants also deficient in cytochrome c(6), Synechocystis PCC 6803(petJ,ctaA) and Synechocystis PCC 6803(petJ,pacS), were viable, but the former had increased copper dependence with severely impaired growth in the presence of bathocuproinedisulfonic acid (copper chelator). Analogous transporters are likely to supply copper to plastocyanin in chloroplasts.

Epidemiology in the pharmaceutical industry: a perspective for infectious diseases

As access to observational data and databases expands so does the need for epidemiologists in industry. As an example, in the U.K. arm of the Department of Epidemiology at GlaxoWellcome Research and Development, the number of PhD-trained epidemiologists increased from zero in 1996 to eight in 1999. Their remit is often broad, including designing and co-ordinating, pharmacoepidemiologic research, studies of risk factors for disease and disease progression and pregnancy registries. Where appropriate, existing data sources, such as research databases, are employed for studies. Otherwise, primary data collection is pursued using standard methodology, for example, cross-sectional, case-control and cohort studies. This paper describes a structure for epidemiologic research in the pharmaceutical industry, the role of the industry epidemiologist and the scope of epidemiological studies. Two examples of observational studies of HSV-2/HIV interactions are given, and implications for research agendas discussed. The pharmaceutical industry is becoming increasingly committed to epidemiological research, and research agendas often involve extensive collaboration with leading external academic and public health groups.

HIV infection in Poland (1985-96)

Reported numbers of HIV infections have provided an indication of the order of magnitude of the size of the HIV epidemic in Poland, and how it has evolved in time. To the end of 1996, most documented infections had been observed among intravenous drug users (IDUs, n=2, 933/3,470) and, to a lesser extent, men who have sex with men (MSM, 289/3,470). Reported infections among non-IDU prostitutes and other non-IDU heterosexuals remained low. In this paper we describe surveillance systems and epidemiologic data in Poland from 1985 to 1996 for AIDS cases, HIV infections and other STDs. We also discuss the contributions of different vulnerable groups. Finally we discuss factors influencing the past spread of HIV infection and the potential for future spread, and propose recommendations for surveillance and research.

Type of partnership and heterosexual spread of HIV infection in rural Uganda: results from simulation modelling

The objective was to estimate the likely percentage of HIV infections that may be attributable to one-off partnerships (such as those between female sex workers and their clients) and longer-term partnerships in rural Uganda. This was addressed by the application of a microsimulation model (SimulAIDS) of the transmission dynamics of HIV infection, drawing on data from a population cohort of 10,000 in rural Uganda. For a scenario reproducing documented characteristics of the study population in 1990, when adult HIV prevalence was 9%, and during subsequent follow up (1990-1994), when adult HIV incidence was 8 per 1000 person-years, the percentage of HIV infections in men (women) attributed to one-off partnerships decreased from 96% (26%) during 1980 to 67% (8%) in 1989 and 22% (5%) in 1994. Reducing HIV transmission between one-off partners early in an HIV epidemic may substantially limit the potential for the spread of HIV infection. At a later phase, prevention must also focus on control of transmission between longer-term HIV-discordant partners.

Cobalt-dependent transcriptional switching by a dual-effector MerR-like protein regulates a cobalt-exporting variant CPx-type ATPase

CoaR associates with and confers cobalt-dependent activation of the coaT operator-promoter. A CoaR mutant (Ser-Asn-Ser) in a carboxyl-terminal Cys-His-Cys motif bound the coaT operator-promoter but did not activate expression in response to cobalt, implicating thiolate and/or imidazole ligands at these residues in an allosteric cobalt binding site. Deletion of 1 or 2 nucleotides from between near consensus, but with aberrant (20 base pairs) spacing, -10 and -35 elements enhanced expression from the coaT operator-promoter but abolished activation by cobalt-CoaR. It is inferred that cobalt effects a transition in CoaR that underwinds the coaT operator-promoter to realign promoter elements. In the absence of cobalt, CoaR represses expression (approximately 50%). CoaR is a fusion of ancestral MerR (mercury-responsive transcriptional activator)- and precorrin isomerase (enzyme of vitamin B(12) biosynthesis)-related sequences. Expression from the coaT operator-promoter was enhanced in a partial mutant of cbiE (encoding an enzyme preceding precorrin isomerase in B(12) biosynthesis), revealing that this pathway "inhibits" coaT expression. Disruption of coaT reduced cobalt tolerance and increased cytoplasmic (57)Co accumulation. coaT-mediated restoration of cobalt tolerance has been used as a selectable marker.

A ferric-chelate reductase for iron uptake from soils

Iron deficiency afflicts more than three billion people worldwide, and plants are the principal source of iron in most diets. Low availability of iron often limits plant growth because iron forms insoluble ferric oxides, leaving only a small, organically complexed fraction in soil solutions. The enzyme ferric-chelate reductase is required for most plants to acquire soluble iron. Here we report the isolation of the FRO2 gene, which is expressed in iron-deficient roots of Arabidopsis. FRO2 belongs to a superfamily of flavocytochromes that transport electrons across membranes. It possesses intramembranous binding sites for haem and cytoplasmic binding sites for nucleotide cofactors that donate and transfer electrons. We show that FRO2 is allelic to the frd1 mutations that impair the activity of ferric-chelate reductase. There is a nonsense mutation within the first exon of FRO2 in frd1-1 and a missense mutation within FRO2 in frd1-3. Introduction of functional FRO2 complements the frd1-1 phenotype in transgenic plants. The isolation of FRO2 has implications for the generation of crops with improved nutritional quality and increased growth in iron-deficient soils.

Current estimates of and future projections for adult deaths attributed to HIV infection in Zimbabwe

OBJECTIVE

Estimates of HIV prevalence in 1995 among all adults in Zimbabwe range between about 18% and 24%. The objective of this study was to estimate, for Zimbabwe, the impact of HIV infection on adult mortality, by age and gender, between 1995 and the year 2000.

METHODS

For this analysis, we used 1992 census data to estimate the number of non-HIV-related deaths, and a short-term projection model to estimate the number of deaths attributed to HIV infection in 1995 and the year 2000.

RESULTS

It was estimated that between 52% and 60% of all adult deaths in 1995 were attributed to HIV infection, and between 69% and 76% in both males and females in the group between 20 and 39 years of age. The estimated adult mortality rate per 1000 increased from 9.8 in 1987 (based on census data) to between 20.6 and 24.3 in 1995. For the year 2000, it was projected that between 66% and 73% of all adult deaths would be attributed to HIV infection, and between 81% and 86% in those aged 20 to 39 years. The estimated adult mortality rate in the year 2000 increased to between 29.1/1000 and 36.6/1000. Even if all transmission was assumed to cease after 1995, it was projected that >60% of adult deaths would be attributed to HIV in the year 2000. Adult population growth is projected to decrease to between 0.3% and 1.0% in the year 2000.

CONCLUSION

Results suggest that the impact of HIV infection on mortality in Zimbabwe is already severe and will continue to increase. Efforts to reduce numbers of new HIV infections today will serve to reduce the future burden of mortality, particularly in the longer term.

Coordination of Zn2+ (and Cd2+) by prokaryotic metallothionein. Involvement of his-imidazole

In mammalian metallothionein Zn2+ is exclusively coordinated to Cys-thiolate to form clusters in which the metal is thermodynamically stable but also kinetically labile. By contrast, little is known about coordination to prokaryotic metallothionein, SmtA. 3 nmol of Zn2+ nmol-1 SmtA were displaced by 8 nmol of p-(hydroxymercuri)phenylsulfonate implicating eight of the nine Cys in the coordination of three metal ions. None of the Zn2+ associated with SmtA was accessible to 4-(2-pyridylazo)resorcinol prior to the addition of p-(hydroxymercuri)phenylsulfonate. An unusual feature of SmtA is the presence of three His residues, and we have investigated whether these contribute to metal coordination. Less Zn2+ was associated with purified SmtA(H40R/H49R/H55R), in which all three His residues were substituted with Arg, and approximately one equivalent of Zn2+ was immediately accessible to 4-(2-pyridylazo)resorcinol. Following incubation of SmtA with 111Cd, three 111Cd resonances were detected, two in a range expected for CdS4 and the third indicative of either CdNS3 or CdN2S2 coordination. Two-dimensional TOCSY 1H NMR and 111Cd-edited 1H NMR showed two His residues bound to 111Cd, confirming CdN2S2 coordination. The pH of half-dissociation of Zn2+ increased from 4.05 for SmtA to 5.37 for SmtA(H40R/H49R/H55R). Equivalent values for single His mutants SmtA(H40R), SmtA(H49R), and SmtA(H55R) were 4.62, 4.48, and 3.81, respectively, revealing that conversion of His40 or His49 to Arg impairs Zn2+ binding at the CdN2S2 and CdS4 sites. Only approximately two equivalents of Zn2+ were associated with purified SmtA(H49R). The appearance of a fourth 111Cd resonance at lower pH suggests that an alternative CdN2S2 site also exists.

An SmtB-like repressor from Synechocystis PCC 6803 regulates a zinc exporter

ORF slr0798, now designated ziaA, from Synechocystis PCC 6803 encodes a polypeptide with sequence features of heavy metal transporting P-type ATPases. Increased Zn2+ tolerance and reduced 65Zn accumulation was observed in Synechococcus PCC 7942, strain R2-PIM8(smt), containing ziaA and upstream regulatory sequences, compared with control cells. Conversely, reduced Zn2+ tolerance was observed following disruption of ziaA in Synechocystis PCC 6803, and ziaA-mediated restoration of Zn2+ tolerance has subsequently been used as a selectable marker for transformation. Nucleotide sequences upstream of ziaA, fused to a promoterless lacZ gene, conferred Zn2+-dependent beta-galactosidase activity when introduced into R2-PIM8(smt). The product of ORF sll0792, designated ZiaR, is a Zn2+-responsive repressor of ziaA transcription. Reporter gene constructs lacking ziaR conferred elevated Zn2+-independent expression from the ziaA operator-promoter in R2-PIM8(smt). Gel retardation assays detected ZiaR-dependent complexes forming with the zia operator-promoter and ZiaR-DNA binding was enhanced by treatment with a metal-chelator in vitro. Two mutants of ZiaR (C71S/C73S and H116R) bound to, and repressed expression from, the ziaA operator-promoter but were unable to sense Zn2+. Metal coordination to His-imidazole and Cys-thiolate ligands at these residues of ZiaR is thus implicated in Zn2+-perception by Synechocystis PCC 6803.