The role of antigenic stimulation and cytotoxic T cell activity in regulating the long-term immunopathogenesis of HIV: mechanisms and clinical implications

This paper develops a predictive mathematical model of cell infection, host immune response and viral replication that reproduces observed long-term trends in human immunodeficiency virus (HIV) pathogenesis. Cell activation induced by repeated exposure to many different antigens is proposed as the principal mechanism of providing target cells for HIV infection and, hence, of CD4+ T cell depletion, with regulation of the overall T cell pool size causing concomitant CD8 pool increases. The model correctly predicts the cross-patient variability in disease progression, the rate of which is found to depend on the efficacy of anti-HIV cytotoxic T lymphocyte responses, overall viral pathogenicity and random effects. The model also predicts a variety of responses to anti-viral therapy, including episodic residual viral replication and discordant responses and we find that such effects can be suppressed by increasing the potency of treatment.

Predictors of adherence to Copaxone therapy in individuals with relapsing-remitting multiple sclerosis

The purpose of this study was to evaluate psychological, biophysical, and sociodemographic variables as predictors of adherence to glatiramer acetate (Copaxone) therapy in individuals with relapsing-remitting multiple sclerosis (MS). Because Copaxone is a daily subcutaneous injection, individuals with MS are challenged by the daily routine of preparation and administration of this medication. Despite the challenges, some individuals with MS adhere to treatment with injectable medications with little or no difficulty, while others struggle to adhere to, and soon abandon, the daily task. It is important to identify predictors of adherence to Copaxone therapy so those at risk can be identified early and provided with individualized support at the onset of therapy. Potential participants were identified from the Consortium of Multiple Sclerosis Centers North American Research Committee on Multiple Sclerosis Patient Registry database (n = 600) and from the Shared Solutions MS patient support database (n = 600). Individuals who had taken or stopped taking Copaxone were specifically selected. Those taking multiple immunomodulating drugs or not able to complete the data collection instruments were excluded. Booklets containing four instruments (MS Self-Efficacy Control and Function Subscales, Rosenberg Self-Esteem Scale, Herth Hope Index [HHI], and Performance Scale) and sociodemographic data sheets were mailed to 1,200 individuals. Of the 594 who completed and returned booklets, 341 individuals had relapsing-remitting MS and met the inclusion criteria. There were 225 individuals in the adherent group and 116 in the nonadherent group. Logistic regression analysis revealed four significant predictors of adherence: self-efficacy (control), hope, perception that the doctor was the most supportive of the individual taking Copaxone, and no previous use of other immunomodulators. The higher the score on the MS Self-Efficacy Control Subscale and HHI, the more likely the individual will adhere to Copaxone therapy. The MS Self-Efficacy Control Subscale and HHI show promise of being useful predictors of adherence. Further testing is recommended. Physician support should be conveyed to all individuals starting and maintaining Copaxone therapy for MS. Greater support needs to be provided to those who have previously taken immunomodulating drugs.

Changing provider behavior: an overview of systematic reviews of interventions

BACKGROUND

Increasing recognition of the failure to translate research findings into practice has led to greater awareness of the importance of using active dissemination and implementation strategies. Although there is a growing body of research evidence about the effectiveness of different strategies, this is not easily accessible to policy makers and professionals.

OBJECTIVES

To identify, appraise, and synthesize systematic reviews of professional educational or quality assurance interventions to improve quality of care.

RESEARCH DESIGN

An overview was made of systematic reviews of professional behavior change interventions published between 1966 and 1998.

RESULTS

Forty-one reviews were identified covering a wide range of interventions and behaviors. In general, passive approaches are generally ineffective and unlikely to result in behavior change. Most other interventions are effective under some circumstances; none are effective under all circumstances. Promising approaches include educational outreach (for prescribing) and reminders. Multifaceted interventions targeting different barriers to change are more likely to be effective than single interventions.

CONCLUSIONS

Although the current evidence base is incomplete, it provides valuable insights into the likely effectiveness of different interventions. Future quality improvement or educational activities should be informed by the findings of systematic reviews of professional behavior change interventions.

Use of generalized linear mixed models in the spatial analysis of small-area malaria incidence rates in Kwazulu Natal, South Africa

Spatial statistical analysis of 1994-1995 small-area malaria incidence rates in the population of the northernmost districts of KwaZulu Natal, South Africa, was undertaken to identify factors that might explain very strong heterogeneity in the rates. In this paper, the authors describe a method of adjusting the regression analysis results for strong spatial correlation in the rates by using generalized linear mixed models and variograms. The results of the spatially adjusted, multiple regression analysis showed that malaria incidence was significantly positively associated with higher winter rainfall and a higher average maximum temperature and was significantly negatively associated with increasing distance from water bodies. The statistical model was used to produce a map of predicted malaria incidence in the area, taking into account local variation from the model prediction if this variation was supported by the data. The predictor variables showed that even small differences in climate can have very marked effects on the intensity of malaria transmission, even in areas subject to malaria control for many years. The results of this study have important implications for malaria control programs in the area.

Viral dynamics and anti-viral pharmacodynamics: rethinking in vitro measures of drug potency

Most current assays used to quantitate the pharmacodynamic effect of anti-viral agents measure the net inhibitory effect of a drug on virus replication over several days in an in vitro cell culture. Such endpoint experiments give cumulative measures of inhibition that vary with the assay used and therefore provide suboptimal information on likely in vivo drug performance. We argue that instantaneous inhibition (proportion of cell infection prevented at a point in time) is a more robust pharmacodynamic measure, and propose techniques to estimate this quantity from endpoint data. Implications for the quantification of drug interactions are discussed.

Nonadherence with ACE inhibitors is common and can be detected in clinical practice by routine serum ACE activity

Our objective was to assess whether serum angiotensin-converting enzyme (ACE) activity during routine clinical practice accurately reflects patient adherence to ACE inhibitor treatment in chronic heart failure (CHF). During 1994-95, ACE was measured in 73 CHF patients who were routinely attending the heart failure clinic at Ninewells Hospital. At the same time, the Medicines Monitoring Unit collected data on whether and when prescriptions for ACE inhibitors were redeemed at community pharmacies, which enabled each patient's adherence over a prolonged period to be assessed. We then correlated whether an elevation in serum ACE was associated with poor adherence with ACE inhibitor treatment. In total, 18% of CHF patients appeared to exhibit less than 70% adherence with their ACE inhibitor treatment, with 34% exhibiting less than 85%adherence and 58% exhibiting less than 100% adherence. A serum ACE activity of more than 12 U/L gave 91% positive predictive accuracy that the patient was less than 100% adherent with his or her ACE inhibitor treatment. At the other extreme, a serum ACE less than 6.5 U/L gave 81% positive predictive accuracy that the patient was more than 85% adherent with ACE inhibitor treatment. Nonadherence with ACE inhibitor treatment, therefore, was found to be common in patients with CHF. The simple, inexpensive test of serum ACE activity can be used in CHF patients to identify many, although not all, nonadherent patients so that adherence-enhancing strategies can be targeted toward them. Further work is clearly required to explore the precise clinical utility of this promising test. (c)2001 by CHF, Inc.

Cloning, characterization, and functional studies of human and mouse glycoprotein VI: a platelet-specific collagen receptor from the immunoglobulin superfamily

Injuries to the vessel wall and subsequent exposure of collagen from the subendothelial matrix result in thrombus formation. In physiological conditions, the platelet plug limits blood loss. However, in pathologic conditions, such as rupture of atherosclerotic plaques, platelet-collagen interactions are associated with cardiovascular and cerebral vascular diseases. Platelet glycoprotein VI (GPVI) plays a crucial role in collagen-induced activation and aggregation of platelets, and people who are deficient in GPVI suffer from bleeding disorders. Based on the fact that GPVI is coupled to the Fc receptor (FcR)-gamma chain and thus should share homology with the FcR chains, the genes encoding human and mouse GPVI were identified. They belong to the immunoglobulin (Ig) superfamily and share 64% homology at the protein level. Functional evidence demonstrating the identity of the recombinant protein with GPVI was shown by binding to its natural ligand collagen; binding to convulxin (Cvx), a GPVI-specific ligand from snake venom; binding of anti-GPVI IgG isolated from a patient; and association to the FcR-gamma chain. The study also demonstrated that the soluble protein blocks Cvx and collagen-induced platelet aggregation and that GPVI expression is restricted to megakaryocytes and platelets. Finally, human GPVI was mapped to chromosome 19, long arm, region 1, band 3 (19q13), in the same region as multiple members of the Ig superfamily. This work offers the opportunity to explore the involvement of GPVI in thrombotic disease, to develop alternative antithrombotic compounds, and to characterize the mechanism involved in GPVI genetic deficiencies. (Blood. 2000;96:1798-1807)

Distribution of twelve linear extrachromosomal DNAs in natural isolates of Lyme disease spirochetes

We have analyzed a panel of independent North American isolates of the Lyme disease agent spirochete, Borrelia burgdorferi (sensu stricto), for the presence of linear plasmids with sequence similarities to the 12 linear plasmids present in the B. burgdorferi type strain, isolate B31. The frequency of similarities to probes from each of the 12 B31 plasmids varied from 13 to 100% in the strain panel examined, and these similarities usually reside on plasmids similar in size to the cognate B31 plasmid. Sequences similar to 5 of the 12 B31 plasmids were found in all of the isolates examined, and >66% of the panel members hybridized to probes from 4 other plasmids. Sequences similar to most of the B. burgdorferi B31 plasmid-derived DNA probes used were also found on linear plasmids in the related Eurasian Lyme agents Borrelia garinii and Borrelia afzelii; however, some of these plasmids had uniform but substantially different sizes from their B. burgdorferi counterparts.

Reduction of the HIV-1-infected T-cell reservoir by immune activation treatment is dose-dependent and restricted by the potency of antiretroviral drugs

BACKGROUND

Treatments combining T-cell activating agents and potent antiretroviral drugs have been proposed as a possible means of reducing the reservoir of long-lived HIV-1 infected quiescent CD4 T-cells.

OBJECTIVE

To analyse the effect of such therapies on HIV-1 dynamics and T-cell homeostasis.

DESIGN AND METHODS

A mathematical framework describing HIV-1 dynamics and T-cell homeostasis was developed. Three patients who were kept on a particularly potent course of highly active antiretroviral therapy (HAART) were treated with the anti-CD3 monoclonal antibody OKT3 and interleukin (IL)-2. Plasma HIV-RNA, and HIV-RNA and DNA in peripheral blood mononuclear cells and lymph node mononuclear cells were measured. These results and other published studies on the use of IL-2 alone were assessed using our mathematical framework.

RESULTS

We show that outcome of treatment is determined by the relative rates of depletion of the infected quiescent T-cell population by activation and of its replenishment through new infection. Which of these two processes dominates is critically dependent on both the potency of HAART and also the degree of T-cell activation induced. We demonstrate that high-level T-cell stimulation is likely to produce negative outcomes, both by failing to reduce viral reservoirs and by depleting the CD4 T-cell pool and disrupting CD4/CD8 T-cell homeostasis. In contrast, repeated low-level stimulation may both aid CD4 T-cell pool expansion and achieve a substantial reduction in the long-lived HIV-1 reservoir.

CONCLUSIONS

Our analysis suggests that although treatment that activates T-cells can reduce the long-lived HIV-1 reservoir, caution should be used as high-level stimulation may result in a negative outcome.

Effect of preventive home visits by a nurse on the outcomes of frail elderly people in the community: a randomized controlled trial

BACKGROUND

Timely recognition and prevention of health problems among elderly people have been shown to improve their health. In this randomized controlled trial the authors examined the impact of preventive home visits by a nurse compared with usual care on the outcomes of frail elderly people living in the community.

METHODS

A screening questionnaire identified eligible participants (those aged 70 years or more at risk of sudden deterioration in health). Those randomly assigned to the visiting nurse group were assessed and followed up in their homes for 14 months. The primary outcome measure was the combined rate of deaths and admissions to an institution, and the secondary outcome measure the rate of health services utilization, during the 14 months; these rates were determined through a medical chart audit by a research nurse who was blind to group allocation.

RESULTS

The questionnaire was mailed to 415 elderly people, of whom 369 (88.9%) responded. Of these, 198 (53.7%) were eligible, and 142 consented to participate and were randomly assigned to either the visiting nurse group (73) or the usual care group (69). The combined rate of deaths and admissions to an institution was 10.0% in the visiting nurse group and 5.8% in the usual care group (p = 0.52). The rate of health services utilization did not differ significantly between the 2 groups. Influenza and pneumonia vaccination rates were significantly higher in the visiting nurse group (90.1% and 81.9%) than in the usual care group (53.0% and 0%) (p < 0.001).

INTERPRETATION

The trial failed to show any effect of a visiting nurse other than vastly improved vaccination coverage.

Using a geographical information system to plan a malaria control programme in South Africa

INTRODUCTION

Sustainable control of malaria in sub-Saharan Africa is jeopardized by dwindling public health resources resulting from competing health priorities that include an overwhelming acquired immunodeficiency syndrome (AIDS) epidemic. In Mpumalanga province, South Africa, rational planning has historically been hampered by a case surveillance system for malaria that only provided estimates of risk at the magisterial district level (a subdivision of a province).

METHODS

To better map control programme activities to their geographical location, the malaria notification system was overhauled and a geographical information system implemented. The introduction of a simplified notification form used only for malaria and a carefully monitored notification system provided the good quality data necessary to support an effective geographical information system.

RESULTS

The geographical information system displays data on malaria cases at a village or town level and has proved valuable in stratifying malaria risk within those magisterial districts at highest risk, Barberton and Nkomazi. The conspicuous west-to-east gradient, in which the risk rises sharply towards the Mozambican border (relative risk = 4.12, 95% confidence interval = 3.88-4.46 when the malaria risk within 5 km of the border was compared with the remaining areas in these two districts), allowed development of a targeted approach to control.

DISCUSSION

The geographical information system for malaria was enormously valuable in enabling malaria risk at town and village level to be shown. Matching malaria control measures to specific strata of endemic malaria has provided the opportunity for more efficient malaria control in Mpumalanga province.

Antigen-driven CD4+ T cell and HIV-1 dynamics: residual viral replication under highly active antiretroviral therapy

Antigen-induced stimulation of the immune system can generate heterogeneity in CD4+ T cell division rates capable of explaining the temporal patterns seen in the decay of HIV-1 plasma RNA levels during highly active antiretroviral therapy. Posttreatment increases in peripheral CD4+ T cell counts are consistent with a mathematical model in which host cell redistribution between lymph nodes and peripheral blood is a function of viral burden. Model fits to patient data suggest that, although therapy reduces HIV replication below replacement levels, substantial residual replication continues. This residual replication has important consequences for long-term therapy and the evolution of drug resistance and represents a challenge for future treatment strategies.

Nonadherence with angiotensin-converting enzyme inhibitor therapy: a comparison of different ways of measuring it in patients with chronic heart failure

OBJECTIVES

This study was designed to compare different proposed methods of assessing adherence with angiotensin-converting enzyme (ACE) inhibitor (ACEI) therapy in chronic heart failure.

BACKGROUND

The use of ACEIs in chronic heart failure gives us a unique opportunity to assess a patient's adherence by measuring whether the expected biochemical effect of an ACEI is present in the patient's bloodstream. In fact, there are several different ways of assessing ACE in vivo: these are serum ACE activity itself, plasma N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP), urine AcSDKP, plasma angiotensin I (AI), plasma angiotensin II (AII), or the AII/AI ratio.

METHODS

Patients with chronic heart failure (n = 39) were randomized to regimens of ACEI nonadherence for one week, ACEI adherence for one week or two versions of partial adherence for one week, after which the above six tests were performed.

RESULTS

All six tests significantly distinguished between full nonadherence for one week and full or partial adherence. Only plasma AcSDKP produced a significantly different result between partial adherence and either full adherence or full nonadherence for one week. In terms of their ability to distinguish full nonadherence from full adherence, plasma AcSDKP was 89% sensitive and 100% specific with an area under its ROC of 0.95. Corresponding figures for urine AcSDKP were 92%, 97% and 0.95 and for serum ACE they were 86%, 95% and 0.90.

CONCLUSIONS

All six tests distinguished full nonadherence from all other forms of adherence. The rank order of performance was plasma AcSDKP, urine AcSDKP, serum ACE, AII/AI ratio and plasma AII followed by plasma AI.

Non-adherence with ACE inhibitor treatment is common in heart failure and can be detected by routine serum ACE activity assays

OBJECTIVE

To assess whether serum angiotensin converting enzyme (ACE) activity during routine clinical practice accurately reflects patient adherence to ACE inhibitor treatment for chronic heart failure (CHF).

DESIGN

Retrospective assessment of ACE inhibitor adherence and serum ACE activity measurements.

SETTING

Teaching hospital outpatient department

PATIENTS AND INTERVENTIONS

During 1994-95, serum ACE was measured in 73 CHF patients who were routinely attending the heart failure clinic at Ninewells Hospital. At the same time, the medicines monitoring unit collected data on whether and when prescriptions for ACE inhibitors were redeemed at community pharmacies, which enabled each patient's adherence over a prolonged period to be assessed.

MAIN OUTCOME MEASURES

Routine collected serum ACE measurements were correlated with measured adherence with ACE inhibitor treatment.

RESULTS

In total, 18% of CHF patients appeared to exhibit < 70% adherence with their ACE inhibitor treatment with 34% exhibiting less than 85% adherence and 58% exhibiting < 100% adherence. A serum ACE activity of > 12 u/l gave 91% positive predictive accuracy that the patient was < 100% adherent with their ACE inhibitor treatment. At the other extreme, a serum ACE < 6.5 u/l gave 81% positive predictive accuracy that the patient was > 85% adherent with ACE inhibitor treatment.

CONCLUSIONS

Non-adherence with ACE inhibitor treatment was found to be common in patients with CHF. The simple, inexpensive test of serum ACE activity can be used in CHF patients to identify many, although not all, non-adherent patients so that adherence enhancing strategies can be targeted towards them. Further work is clearly required to explore the precise clinical use of this promising test.

A survey of general practitioners in north-east Scotland on practice-based counselling services

OBJECTIVE

Practice-based counselors have become very numerous in primary care and we sought to elicit the views of general practitioners in north-east Scotland about the present situation and possible developments in practice-based counselling services.

DESIGN AND SUBJECTS

A questionnaire was mailed to the 352 general practitioners working in the area covered by Grampian Health Board.

RESULTS

There was a 74% response rate: 46% of respondents had access to a practice-based counsellor and of those who did not, two-thirds wanted to acquire one. Larger practices and fundholding practices were more likely to have practice-based counsellors. There was a lack of knowledge about the medico-legal situation when referrals to counsellors were made. Seventy-nine per cent of respondents thought that the need/demand for counselling would increase during the next decade, and a majority considered provision of counselling through mental health teams, with local co-ordination of accreditation, training and supervision, to be desirable.

CONCLUSION

Since the efficacy of counselling for mental health problems in primary care has not been established, and provision of counselling in primary care settings continues to increase, there is a need to mount coherent and appropriate research studies. There also appears to be a need for greater integration between primary care and mental health services to generate rational provision of practice-based counselling.

Identification of a vibrio cholerae RTX toxin gene cluster that is tightly linked to the cholera toxin prophage

We identify and characterize a gene cluster in El Tor Vibrio cholerae that encodes a cytotoxic activity for HEp-2 cells in vitro. This gene cluster contains four genes and is physically linked to the cholera toxin (CTX) element in the V. cholerae genome. We demonstrate by using insertional mutagenesis that this gene cluster is required for the cytotoxic activity. The toxin, RtxA, resembles members of the RTX (repeats in toxin) toxin family in that it contains a GD-rich repeated motif. Like other RTX toxins, its activity depends on an activator, RtxC, and an associated ABC transporter system, RtxB and RtxD. In V. cholerae strains of the classical biotype, a deletion within the gene cluster removes rtxC and eliminates cytotoxic activity. Other strains, including those of the current cholera pandemic, contain a functional gene cluster and display cytotoxic activity. Thus, the RTX gene cluster in El Tor O1 and O139 strains might have contributed significantly to their emergence. Furthermore, the RTX toxin of V. cholerae may be associated with residual adverse properties displayed by certain live, attenuated cholera vaccines.

The experience of transition for a daughter caregiver of a stroke survivor

The purpose of this study was to describe the experience of transition for a daughter caregiver of a stroke survivor. A phenomenologic, longitudinal case study of a woman in her late twenties provided the means by which the lived experience of transition could be studied and understood. The eleven unstructured, audiotaped interviews took place approximately every two weeks over a six and a half month period. They began six weeks after her mother's stroke and lasted until three months after her mother returned home, when life became more organized and predictable for a time. The interviews were transcribed verbatim and analyzed according to a modified version of Colaizzi's descriptive phenomenologic methodology. Since there was a temporal consideration, a time-ordered matrix was used to identify themes over time. The themes that emerged over time included: (a) changing relationships, (b) becoming a caregiver then stepping back, (c) enduring emotional turbulence, (d) taking one day at a time and (e) struggling to hang onto hope. Integration of the themes provided an exhaustive description. The experience of transition was a process that involved disruptions in close relations and daily living. The connection to a network of relationships changed to disconnection, and the fabric of interrelated lives began to unravel. The many sensations experienced were different and conflicting, revealing a rapidly changing perception of the world. An unknown future threatened to become overwhelming. Focusing on the present helped to quell the turbulent sensations experienced. An unknown future temporarily provided the opportunity to hope that daily life could once again become familiar and comfortable. The extent and object of hope changed over time. A pattern of chaos exemplified the process of transition. The passage of time revealed that life as it was known before the transition had changed. A new way of being in the world was experienced.