Estimating epidemiological parameters from experiments in vector access to host plants, the method of matching gradients.

Estimation of pathogenic life-history values, for instance the duration a pathogen is retained in an insect vector (i.e., retention period) is of particular importance for understanding plant disease epidemiology. How can we extract values for these epidemiological parameters from conventional small-scale laboratory experiments in which transmission success is measured in relation to durations of vector access to host plants? We provide a solution to this problem by deriving formulae for the empirical curves that these experiments produce, called access period response curves (i.e., transmission success vs access period). We do this by writing simple equations for the fundamental life-cycle components of insect vectors in the laboratory. We then infer values of epidemiological parameters by matching the theoretical and empirical gradients of access period response curves. Using the example of Cassava brown streak virus (CBSV), which has emerged in sub-Saharan Africa and now threatens regional food security, we illustrate the method of matching gradients. We show how applying the method to published data produces a new understanding of CBSV through the inference of retention period, acquisition period and inoculation period parameters. We found that CBSV is retained for a far shorter duration in its insect vector (Bemisia tabaci whitefly) than had previously been assumed. Our results shed light on a number of critical factors that may be responsible for the transition of CBSV from sub- to super-threshold R0 in sub-Saharan Africa. The method is applicable to plant pathogens in general, to supply epidemiological parameter estimates that are crucial for practical management of epidemics and prediction of pandemic risk

Has the phasing out of stavudine in accordance with changes in WHO guidelines led to a decrease in single-drug substitutions in first-line antiretroviral therapy for HIV in sub-Saharan Africa?

This version is the Accepted Manuscript and is published in final edited form as: AIDS. 2017 January 02; 31(1): 147–157. doi:10.1097/QAD.0000000000001307OBJECTIVE: We assessed the relationship between phasing out stavudine in first-line antiretroviral therapy (ART) in accordance with WHO 2010 policy and single-drug substitutions (SDS) (substituting the nucleoside reverse transcriptase inhibitor in first-line ART) in sub-Saharan Africa. DESIGN: Prospective cohort analysis (International epidemiological Databases to Evaluate AIDS-Multiregional) including ART-naive, HIV-infected patients aged at least 16 years, initiating ART between January 2005 and December 2012. Before April 2010 (July 2007 in Zambia) national guidelines called for patients to initiate stavudine-based or zidovudine-based regimen, whereas thereafter tenofovir or zidovudine replaced stavudine in first-line ART. METHODS: We evaluated the frequency of stavudine use and SDS by calendar year 2004-2014. Competing risk regression was used to assess the association between nucleoside reverse transcriptase inhibitor use and SDS in the first 24 months on ART. RESULTS: In all, 33 441 (8.9%; 95% confience interval 8.7-8.9%) SDS occurred among 377 656 patients in the first 24 months on ART, close to 40% of which were amongst patients on stavudine. The decrease in SDS corresponded with the phasing out of stavudine. Competing risks regression models showed that patients on tenofovir were 20-95% less likely to require a SDS than patients on stavudine, whereas patients on zidovudine had a 75-85% decrease in the hazards of SDS when compared to stavudine. CONCLUSION: The decline in SDS in the first 24 months on treatment appears to be associated with phasing out stavudine for zidovudine or tenofovir in first-line ART in our study. Further efforts to decrease the cost of tenofovir and zidovudine for use in this setting is warranted to substitute all patients still receiving stavudine

Role of viral and bacterial pathogens in causing pneumonia among Western Australian children: A case-control study protocol

Introduction: Pneumonia is the leading cause of childhood morbidity and mortality globally. Introduction of the conjugate Haemophilus influenzae B and multivalent pneumococcal vaccines in developed countries including Australia has significantly reduced the overall burden of bacterial pneumonia. With the availability of molecular diagnostics, viruses are frequently detected in children with pneumonia either as primary pathogens or predispose to secondary bacterial infection. Many respiratory pathogens that are known to cause pneumonia are also identified in asymptomatic children, so the true contribution of these pathogens to childhood community-acquired pneumonia (CAP) remains unclear. Since the introduction of pneumococcal vaccines, very few comprehensive studies from developed countries have attempted to determine the bacterial and viral aetiology of pneumonia. We aim to determine the contribution of bacteria and viruses to childhood CAP to inform further development of effective diagnosis, treatment and preventive strategies. Methods and analysis: We are conducting a prospective case-control study (PneumoWA) where cases are children with radiologically confirmed pneumonia admitted to Princess Margaret Hospital for Children (PMH) and controls are healthy children identified from PMH outpatient clinics and from local community immunisation clinics. The case-control ratio is 1:1 with 250 children to be recruited in each arm. Nasopharyngeal swabs are collected from both cases and controls to detect the presence of viruses and bacteria by PCR; pathogen load will be assessed by quantitative PCR. The prevalence of pathogens detected in cases and controls will be compared, the OR of detection and population attributable fraction to CAP for each pathogen will be determined; relationships between pathogen load and disease status and severity will be explored. Ethics and dissemination: This study has been approved by the human research ethics committees of PMH, Perth, Australia (PMH HREC REF 2014117EP). Findings will be disseminated at research conferences and in peer-reviewed journals

Lumbar Puncture-Related Knowledge, Attitudes, and Practices among Patients, Caregivers, Doctors, and Nurses in Zambia.

Lumbar puncture (LP) is underused for neuroinfectious disease diagnosis in Zambia, but reasons for poor uptake remain speculative. This cross-sectional study assessed LP knowledge, attitudes, and practices among patients/caregivers and healthcare workers (HCWs) and predictors of LP completion. Patients with suspected central nervous system infection, caregivers, and HCWs at the University Teaching Hospitals in 2016 were eligible. Questions adapted from the existing literature were used for a LP knowledge score. Predictors of knowledge scores were assessed independently for patients/caregivers and HCWs. Predictors of LP completion were assessed using multivariable logistic regression. Among 123 patients/caregivers, LP knowledge was poor. Pediatric caregivers were more likely than adult patients/caregivers to report LP could be replaced by neuroimaging (90% versus 78%, P < 0.001) and cause paralysis (57% versus 39%, P = 0.01). There were no significant predictors of the knowledge score among patients/caregivers. Among HCWs, 28% said LP makes patients clinically worse, and 60% reported it could cause paralysis. The increased knowledge score was associated with greater wealth (P = 0.03) and personally knowing someone who underwent LP (P < 0.001). Lumbar puncture was completed on 67/112 (57%) patients and was associated with an increased knowledge score (OR: 1.62 [95% CI: 1.19-2.23]). Pediatric patients (OR: 0.18 [95% CI: 0.07-0.47]) and those with a fear of paralysis (OR 0.29 [95% CI: 0.11-0.77]) were less likely to undergo LP. Improving LP-related knowledge may improve uptake. Healthcare workers sense of LP risk may also play a role in encouraging/discouraging use

\u27I need time to start antiretroviral therapy\u27: Understanding reasons for delayed ART initiation among people diagnosed with HIV in Lusaka, Zambia

INTRODUCTION: Rapid antiretroviral therapy (ART) initiation can improve patient outcomes such as viral suppression and prevent new infections. However, not everyone who can start ART does so immediately. METHODS: We conducted a qualitative study to inform interventions supporting rapid initiation in the \u27Test and Start\u27 era. We purposively sampled 20 adult patients living with HIV and a previous gap in care from ten health facilities in Lusaka, Zambia for interviews. We inductively analysed transcripts using a thematic, narrative approach. In their narratives, seven participants discussed delaying ART initiation. RESULTS: Drawing on messages gleaned from facility-based counselling and community information, many cited greater fear of rapid sickness or death due to imperfect adherence or treatment side effects than negative health consequences due to delayed initiation. Participants described needing time to \u27prepare\u27 their minds for a lifetime treatment commitment. Concerns about inadvertent HIV status disclosure during drug collection discouraged immediate initiation, as did feeling healthy, and worries about the impact of ART initiation on relationship dynamics. CONCLUSION: Findings suggest that counselling messages should accurately communicate treatment risks, without perpetuating fear-based narratives about HIV. Identifying and managing patient-specific concerns and reasons for the \u27need for time\u27 may be important for supporting individuals to rapidly accept lifelong treatment.Key messagesFear-based adherence messaging in health facilities about the dangers of missing a treatment dose or changing the time when ART is taken contributes to Zambian patients\u27 refusals of immediate ART initiationResponsive health systems that balance a stated need for time to accept one\u27s diagnosis and prepare to embark on a lifelong treatment plan with interventions to identify and manage patient-specific treatment related fears and concerns may support more rapid ART initiationPerceived social stigma around HIV continues to be a significant challenge for treatment initiation

The Medicinal Chemistry of 5-HT6 Receptor Ligands with a Focus on Arylsulfonyltryptamine Analogs

Arylsulfonyl analogs of aminopyrimidines (e.g. Ro 04-6790; 2), aminopyridines (e.g. Ro 63-0563; 3), 1-phenylpiperazines (e.g. SB-271046; 4), and tryptamines (e.g. MS-245; 5) were described as the first examples of selective 5-HT6 receptor antagonists only ten years ago. Today, hundreds of compounds of seemingly diverse structure have been reported. The early antagonists featured an arylsulfonyl group leading to the widespread assumption that an arylsulfonyl moiety might be critical for binding and antagonist action. With respect to the arylsulfonyltryptamines, it seems that neither the “arylsulfonyl” nor the “tryptamine” portion of these compounds is essential for binding or for antagonist action, and some such derivatives even display agonist action. The present review describes many of the currently available 5-HT6 receptor ligands and, unlike prior reviews, provides a narrative of the thinking (where possible) that led to their design, synthesis, and evaluation. The arylsulfonyltryptamines are also used as the structural basis of attempts to relate various structure-types to one another to afford a better understanding of the overall structural requirements for 5-HT6 receptor binding

Multi-stakeholder consensus on a target product profile for an HIV cure

Developing a cure for HIV is a global priority. Target product profiles are a tool commonly used throughout the drug development process to align interested parties around a clear set of goals or requirements for a potential product. Three distinct therapeutic modalities (combination therapies, ex-vivo gene therapy, and in-vivo gene therapy) for a target product profile for an HIV cure were identified. Using a process of expert face-to-face consultation and an online Delphi consultation, we found a high degree of agreement regarding the criteria for the optimum target product profile. Although the minimum attributes for a cure were debated, the broad consensus was that an acceptable cure need not be as safe and effective as optimally delivered antiretroviral therapy. An intervention that successfully cured a reasonable fraction of adults would be sufficient to advance to the clinic. These target product profiles will require further discussion and ongoing revisions as the field matures

Multi-stakeholder consensus on a target product profile for an HIV cure

Developing a cure for HIV is a global priority. Target product profiles are a tool commonly used throughout the drug development process to align interested parties around a clear set of goals or requirements for a potential product. Three distinct therapeutic modalities (combination therapies, ex-vivo gene therapy, and in-vivo gene therapy) for a target product profile for an HIV cure were identified. Using a process of expert face-to-face consultation and an online Delphi consultation, we found a high degree of agreement regarding the criteria for the optimum target product profile. Although the minimum attributes for a cure were debated, the broad consensus was that an acceptable cure need not be as safe and effective as optimally delivered antiretroviral therapy. An intervention that successfully cured a reasonable fraction of adults would be sufficient to advance to the clinic. These target product profiles will require further discussion and ongoing revisions as the field matures

The case for an HIV cure and how to get there

In light of the increasing global burden of new HIV infections, growing financial requirements, and shifting funding landscape, the global health community must accelerate the development and delivery of an HIV cure to complement existing prevention modalities. An effective curative intervention could prevent new infections, overcome the limitations of antiretroviral treatment, combat stigma and discrimination, and provide a sustainable financial solution for pandemic control. We propose steps to plan for an HIV cure now, including defining a target product profile and establishing the HIV Cure Africa Acceleration Partnership (HCAAP), a multidisciplinary public-private partnership that will catalyse and promote HIV cure research through diverse stakeholder engagement. HCAAP will convene stakeholders, including people living with HIV, at an early stage to accelerate the design, social acceptability, and rapid adoption of HIV-cure products