Phenotypic adaptation to temperature in the mosquito vector, Aedes aegypti.

Most models exploring the effects of climate change on mosquito-borne disease ignore thermal adaptation. However, if local adaptation leads to changes in mosquito thermal responses, "one size fits all" models could fail to capture current variation between populations and future adaptive responses to changes in temperature. Here, we assess phenotypic adaptation to temperature in Aedes aegypti, the primary vector of dengue, Zika, and chikungunya viruses. First, to explore whether there is any difference in existing thermal response of mosquitoes between populations, we used a thermal knockdown assay to examine five populations of Ae. aegypti collected from climatically diverse locations in Mexico, together with a long-standing laboratory strain. We identified significant phenotypic variation in thermal tolerance between populations. Next, to explore whether such variation can be generated by differences in temperature, we conducted an experimental passage study by establishing six replicate lines from a single field-derived population of Ae. aegypti from Mexico, maintaining half at 27°C and the other half at 31°C. After 10 generations, we found a significant difference in mosquito performance, with the lines maintained under elevated temperatures showing greater thermal tolerance. Moreover, these differences in thermal tolerance translated to shifts in the thermal performance curves for multiple life-history traits, leading to differences in overall fitness. Together, these novel findings provide compelling evidence that Ae. aegypti populations can and do differ in thermal response, suggesting that simplified thermal performance models might be insufficient for predicting the effects of climate on vector-borne disease transmission.

Humidity - The overlooked variable in the thermal biology of mosquito-borne disease.

Vector-borne diseases cause significant financial and human loss, with billions of dollars spent on control. Arthropod vectors experience a complex suite of environmental factors that affect fitness, population growth and species interactions across multiple spatial and temporal scales. Temperature and water availability are two of the most important abiotic variables influencing their distributions and abundances. While extensive research on temperature exists, the influence of humidity on vector and pathogen parameters affecting disease dynamics are less understood. Humidity is often underemphasized, and when considered, is often treated as independent of temperature even though desiccation likely contributes to declines in trait performance at warmer temperatures. This Perspectives explores how humidity shapes the thermal performance of mosquito-borne pathogen transmission. We summarize what is known about its effects and propose a conceptual model for how temperature and humidity interact to shape the range of temperatures across which mosquitoes persist and achieve high transmission potential. We discuss how failing to account for these interactions hinders efforts to forecast transmission dynamics and respond to epidemics of mosquito-borne infections. We outline future research areas that will ground the effects of humidity on the thermal biology of pathogen transmission in a theoretical and empirical framework to improve spatial and temporal prediction of vector-borne pathogen transmission.

Diversification of JAZ-MYC signaling function in immune metabolism.

Jasmonate (JA) re-programs metabolism to confer resistance to diverse environmental threats. Jasmonate stimulates the degradation of JASMONATE ZIM-DOMAIN (JAZ) proteins that repress the activity of MYC transcription factors. In Arabidopsis thaliana, MYC and JAZ are encoded by 4 and 13 genes, respectively. The extent to which expansion of the MYC and JAZ families has contributed to functional diversification of JA responses is not well understood. Here, we investigated the role of MYC and JAZ paralogs in controlling the production of defense compounds derived from aromatic amino acids (AAAs). Analysis of loss-of-function and dominant myc mutations identified MYC3 and MYC4 as the major regulators of JA-induced tryptophan metabolism. We developed a JAZ family-based, forward genetics approach to screen randomized jaz polymutants for allelic combinations that enhance tryptophan biosynthetic capacity. We found that mutants defective in all members (JAZ1/2/5/6) of JAZ group I over-accumulate AAA-derived defense compounds, constitutively express marker genes for the JA-ethylene branch of immunity and are more resistant to necrotrophic pathogens but not insect herbivores. In defining JAZ and MYC paralogs that regulate the production of amino-acid-derived defense compounds, our results provide insight into the specificity of JA signaling in immunity.

Mapping current and future thermal limits to suitability for malaria transmission by the invasive mosquito Anopheles stephensi.

BACKGROUND: Anopheles stephensi is a malaria-transmitting mosquito that has recently expanded from its primary range in Asia and the Middle East, to locations in Africa. This species is a competent vector of both Plasmodium falciparum and Plasmodium vivax malaria. Perhaps most alarming, the characteristics of An. stephensi, such as container breeding and anthropophily, make it particularly adept at exploiting built environments in areas with no prior history of malaria risk. METHODS: In this paper, global maps of thermal transmission suitability and people at risk (PAR) for malaria transmission by An. stephensi were created, under current and future climate. Temperature-dependent transmission suitability thresholds derived from recently published species-specific thermal curves were used to threshold gridded, monthly mean temperatures under current and future climatic conditions. These temperature driven transmission models were coupled with gridded population data for 2020 and 2050, under climate-matched scenarios for future outcomes, to compare with baseline predictions for 2020 populations. RESULTS: Using the Global Burden of Disease regions approach revealed that heterogenous regional increases and decreases in risk did not mask the overall pattern of massive increases of PAR for malaria transmission suitability with An. stephensi presence. General patterns of poleward expansion for thermal suitability were seen for both P. falciparum and P. vivax transmission potential. CONCLUSIONS: Understanding the potential suitability for An. stephensi transmission in a changing climate provides a key tool for planning, given an ongoing invasion and expansion of the vector. Anticipating the potential impact of onward expansion to transmission suitable areas, and the size of population at risk under future climate scenarios, and where they occur, can serve as a large-scale call for attention, planning, and monitoring.

Incorporating end-users' voices into the development of an implant for HIV prevention: a discrete choice experiment in South Africa and Zimbabwe.

BACKGROUND: Input from end-users during preclinical phases can support market fit for new HIV prevention technologies. With several long-acting pre-exposure prophylaxis (PrEP) implants in development, we aimed to understand young women's preferences for PrEP implants to inform optimal design. METHODS: We developed a discrete choice experiment and surveyed 800 young women in Harare, Zimbabwe and Tshwane, South Africa between September-November 2020. Women aged 18-30 years who were nulliparous, postpartum, or exchanged sex for money, goods or shelter in prior year were eligible; quotas were set for each subgroup. The DCE asked participants to choose between two hypothetical implants for HIV prevention in a series of nine questions. Implants were described by: size, number of rods and insertion sites, duration (6-months, 1-year, 2-years), flexibility, and biodegradability. Random-parameters logit models estimated preference weights. RESULTS: Median age was 24 years (interquartile range 21-27). By design, 36% had used contraceptive implants. Duration of protection was most important feature, with strong preference for a 2-year over 6-month implant. In Zimbabwe, the number of rods/insertion sites was second most important and half as important as duration. Nonetheless, to achieve an implant lasting 2-years, 74% were estimated to accept two rods, one in each arm. In South Africa, preference was for longer, flexible implants that required removal, although each of these attributes were one-third as important as duration. On average, biodegradability and size did not influence Zimbabwean women's choices. Contraceptive implant experience and parity did not influence relative importance of attributes. CONCLUSIONS: While duration of protection was a prominent attribute shaping women's choices for PrEP implants, other characteristics related to discreetness were relevant. Optimizing for longest dosing while also ensuring minimal detection of implant placement seemed most attractive to potential users.

Intracellular islatravir pharmacology differs between species in an in vitro model: implications for preclinical study design.

BACKGROUND: Islatravir (4'-ethynyl-2-fluoro-2'-deoxyadenosine; EFdA) is a first-in-class nucleoside reverse transcriptase translocation inhibitor (NRTTI) being investigated for HIV treatment and prevention. EFdA is intracellularly phosphorylated to EFdA-triphosphate (EFdA-tp), a competitive substrate of deoxyadenosine-triphosphate (dATP). Thus, translating safety and efficacy findings from preclinical studies relies on the assumption that EFdA's intracellular pharmacology can be extrapolated across species. OBJECTIVES: We investigated how EFdA is phosphorylated across animal species commonly used for preclinical models in drug development to identify those that most closely matched humans. METHODS: PBMCs were isolated from whole blood of six species (human, rhesus macaque non-human primate (rmNHP), rat, minipig, dog, and rabbit) using Ficoll separation and counted on a haemocytometer by Trypan blue staining. One million live cells were cultured in media supplemented with 10 U/mL human IL-2, 10% FBS and 1% antibiotics and treated with 0, 17, 170, and 1700 nM EFdA (n = 3 replicates per concentration). After 24 h, representative cell counts were derived from untreated control wells (as above), cells were washed in PBS, and lysed with 70:30 methanol:water. EFdA-tp and dATP concentrations were quantified by HPLC-MS/MS and normalized to the representative live cell counts for each species. RESULTS: When compared to human values, EFdA-tp concentrations for each EFdA treatment concentration were lower in all species (rmNHP 1.5-2.1-fold, rat 4.5-15-fold, minipig 37-71-fold, dog and rabbit >100-fold). Additionally, rmNHP and dog PBMCs exhibited significantly higher (7-10-fold; P < 0.001) dATP when compared with human PBMCs. CONCLUSIONS: Given intracellular pharmacology differences, these preclinical models may be a conservative estimate of EFdA's intracellular pharmacokinetics and efficacy in humans.

Concurrent validity and precision of the thumb disability examination (TDX) in first carpometacarpal osteoarthritis.

STUDY DESIGN: A descriptive psychometric study of precision and concurrent validity of the Thumb Disability Examination (TDX). INTRODUCTION: Thumb carpometacarpal osteoarthritis (CMC OA) is a painful joint condition impacting the functionality of the hand. Therapists use patient-reported outcome measures to evaluate change in disability and symptomology in response to interventions. The TDX is the only condition-specific outcome measure for persons with thumb CMC OA. Its responsiveness, test-retest reliability and concurrent validity with the DASH are published, yet it's precision and concurrent validity with a hand-region-specific tool has not yet been established. PURPOSE OF THE STUDY: We aimed to determine the precision and concurrent validity of the TDX with a region-specific outcome measure in people with thumb CMC OA. METHODS: Sixteen individuals with a medical diagnosis of CMC OA or a positive pressure-shear test completed the TDX across two visits and the Brief Michigan Hand Questionnaire (bMHQ) at the initial visit. The second visit was 7 to 21 days after the first. Self-administration of the TDX and bMHQ were observed by a licensed occupational therapist. RESULTS: Across total and subscale scores of the TDX, standard error of measurement (SEM) values are used to indicate the precision of tool and demonstrate how confident a user can be that change in score exceeds the error inherent to the tool. Minimal detectable change percentage (MDC%) values for the TDX are acceptable (<30%). The TDX demonstrated high concurrent validity with the bMHQ (rs = -0.733; P = .001). DISCUSSION: Precision of the TDX is acceptable and the concurrent validity of the TDX with a commonly used region-specific scale is high. The study was limited by a small, demographically homogeneous sample due to difficulty in recruitment. CONCLUSIONS: The TDX is a precise and valid outcome measure for individuals having a clinical diagnosis or indications of having thumb CMC OA.

Warming temperatures could expose more than 1.3 billion new people to Zika virus risk by 2050.

In the aftermath of the 2015 pandemic of Zika virus (ZIKV), concerns over links between climate change and emerging arboviruses have become more pressing. Given the potential that much of the world might remain at risk from the virus, we used a previously established temperature-dependent transmission model for ZIKV to project climate change impacts on transmission suitability risk by mid-century (a generation into the future). Based on these model predictions, in the worst-case scenario, over 1.3 billion new people could face suitable transmission temperatures for ZIKV by 2050. The next generation will face substantially increased ZIKV transmission temperature suitability in North America and Europe, where naïve populations might be particularly vulnerable. Mitigating climate change even to moderate emissions scenarios could significantly reduce global expansion of climates suitable for ZIKV transmission, potentially protecting around 200 million people. Given these suitability risk projections, we suggest an increased priority on research establishing the immune history of vulnerable populations, modeling when and where the next ZIKV outbreak might occur, evaluating the efficacy of conventional and novel intervention measures, and increasing surveillance efforts to prevent further expansion of ZIKV.

Effects of Polymer Blending on the Performance of a Subcutaneous Biodegradable Implant for HIV Pre-Exposure Prophylaxis (PrEP).

Long-acting (LA) HIV pre-exposure prophylaxis (PrEP) can mitigate challenges of adhering to daily or on-demand regimens of antiretrovirals (ARVs). We are developing a subcutaneous implant comprising polycaprolactone (PCL) for sustained delivery of ARVs for PrEP. Here we use tenofovir alafenamide (TAF) as a model drug. Previously, we demonstrated that the release rates of drugs are controlled by the implant surface area and wall thickness, and the molecular weight (MW) of PCL. Here, we further advance the implant design and tailor the release rates of TAF and the mechanical integrity of the implant through unique polymer blend formulations. In vitro release of TAF from the implant exhibited zero-order release kinetics for ~120 days. TAF release rates were readily controlled via the MW of the polymer blend, with PCL formulations of higher MW releasing the drug faster than implants with lower MW PCL. Use of polymer MW to tune drug release rates is partly explained by PCL crystallinity, as higher PCL crystalline material is often associated with a slower release rate. Moreover, results showed the ability to tailor mechanical properties via PCL blends. Blending PCL offers an effective approach for tuning the ARV release rates, implant duration, and integrity, and ultimately the biodegradation profiles of the implant.

Thermal biology of mosquito-borne disease.

Mosquito-borne diseases cause a major burden of disease worldwide. The vital rates of these ectothermic vectors and parasites respond strongly and nonlinearly to temperature and therefore to climate change. Here, we review how trait-based approaches can synthesise and mechanistically predict the temperature dependence of transmission across vectors, pathogens, and environments. We present 11 pathogens transmitted by 15 different mosquito species - including globally important diseases like malaria, dengue, and Zika - synthesised from previously published studies. Transmission varied strongly and unimodally with temperature, peaking at 23-29ºC and declining to zero below 9-23ºC and above 32-38ºC. Different traits restricted transmission at low versus high temperatures, and temperature effects on transmission varied by both mosquito and parasite species. Temperate pathogens exhibit broader thermal ranges and cooler thermal minima and optima than tropical pathogens. Among tropical pathogens, malaria and Ross River virus had lower thermal optima (25-26ºC) while dengue and Zika viruses had the highest (29ºC) thermal optima. We expect warming to increase transmission below thermal optima but decrease transmission above optima. Key directions for future work include linking mechanistic models to field transmission, combining temperature effects with control measures, incorporating trait variation and temperature variation, and investigating climate adaptation and migration.

Bioenergetic theory predicts infection dynamics of human schistosomes in intermediate host snails across ecological gradients.

Epidemiological dynamics depend on the traits of hosts and parasites, but hosts and parasites are heterogeneous entities that exist in dynamic environments. Resource availability is a particularly dynamic and potent environmental driver of within-host infection dynamics (temporal patterns of growth, reproduction, parasite production and survival). We developed, parameterised and validated a model for resource-explicit infection dynamics by incorporating a parasitism module into dynamic energy budget theory. The model mechanistically explained the dynamic multivariate responses of the human parasite Schistosoma mansoni and its intermediate host snail to variation in resources and host density. At the population level, feedbacks mediated by resource competition could create a unimodal relationship between snail density and human risk of exposure to schistosomes. Consequently, weak snail control could backfire if reductions in snail density release remaining hosts from resource competition. If resource competition is strong and relevant to schistosome production in nature, it could inform control strategies.

Diversity in growth patterns among strains of the lethal fungal pathogen Batrachochytrium dendrobatidis across extended thermal optima.

The thermal sensitivities of organisms regulate a wide range of ecological interactions, including host-parasite dynamics. The effect of temperature on disease ecology can be remarkably complex in disease systems where the hosts are ectothermic and where thermal conditions constrain pathogen reproductive rates. Amphibian chytridiomycosis, caused by the pathogen Batrachochytrium dendrobatidis (Bd), is a lethal fungal disease that is influenced by temperature. However, recent temperature studies have produced contradictory findings, suggesting that our current understanding of thermal effects on Bd may be incomplete. We investigated how temperature affects three different Bd strains to evaluate diversity in thermal responses. We quantified growth across the entire thermal range of Bd, and beyond the known thermal limits (T max and T min). Our results show that all Bd strains remained viable and grew following 24 h freeze (-12 °C) and heat shock (28 °C) treatments. Additionally, we found that two Bd strains had higher logistic growth rates (r) and carrying capacities (K) at the upper and lower extremities of the temperature range, and especially in low temperature conditions (2-3 °C). In contrast, a third strain exhibited relatively lower growth rates and carrying capacities at these same thermal extremes. Overall, our results suggest that there is considerable variation among Bd strains in thermal tolerance, and they establish a new thermal sensitivity profile for Bd. More generally, our findings point toward important questions concerning the mechanisms that dictate fungal thermal tolerances and temperature-dependent pathogenesis in other fungal disease systems.

Hunting, food subsidies, and mesopredator release: the dynamics of crop-raiding baboons in a managed landscape.

The establishment of protected areas or parks has become an important tool for wildlife conservation. However, frequent occurrences of human-wildlife conflict at the edges of these parks can undermine their conservation goals. Many African protected areas have experienced concurrent declines of apex predators alongside increases in both baboon abundance and the density of humans living near the park boundary. Baboons then take excursions outside of the park to raid crops for food, conflicting with the human population. We model the interactions of mesopredators (baboons), apex predators, and shared prey in the park to analyze how four components affect the proportion of time that mesopredators choose to crop-raid: (1) the presence of apex predators; (2) nutritional quality of the crops; (3) mesopredator "shyness" about leaving the park; and (4) human hunting of mesopredators. We predict that the presence of apex predators in the park is the most effective method for controlling mesopredator abundance, and hence significantly reduces their impact on crops. Human hunting of mesopredators is less effective as it only occurs during crop-raiding excursions. Furthermore, making crops less attractive, for instance by planting crops further from the park boundary or farming less nutritional crops, can reduce the amount of time mesopredators crop-raid.

Assessing Scleral Contact Lens Satisfaction in a Keratoconus Population.

PURPOSE: To assess perceived comfort and related experiences of adapted keratoconic scleral contact lens (17-18.2 mm) wearers with a history of wearing other contact lens modalities and to compare these subjective clinical effects with previous experiences. METHODS: Twenty-four keratocones were recruited, signed an informed consent approved by the University Internal Review Board, and were asked to complete a survey and a dry eye questionnaire. RESULTS: Previous lens wearing experience included soft, piggy back, and hybrid lenses but predominantly was corneal gas permeable. An overwhelming majority strongly preferred the comfort and vision with the scleral contact lenses. This cohort of keratoconus patients were on average dry eye suspects according to a dry eye questionnaire but contained individuals with either normal or significantly dry eye scores. However, patients stated that they experienced less dryness with their scleral lenses, but slightly more than half of these patients experienced, at least occasionally, midday fogging. CONCLUSIONS: The scleral contact lenses are extremely well accepted by keratoconic patients because of comfort and vision these devices provide. For many patients, they offer further relief from dryness symptoms. However, midday fogging remains a limitation for many wearers.

Understanding uncertainty in temperature effects on vector-borne disease: a Bayesian approach.

Extrinsic environmental factors influence the distribution and population dynamics of many organisms, including insects that are of concern for human health and agriculture. This is particularly true for vector-borne infectious diseases like malaria, which is a major source of morbidity and mortality in humans. Understanding the mechanistic links between environment and population processes for these diseases is key to predicting the consequences of climate change on transmission and for developing effective interventions. An important measure of the intensity of disease transmission is the reproductive number R0. However, understanding the mechanisms linking R0 and temperature, an environmental factor driving disease risk, can be challenging because the data available for parameterization are often poor. To address this, we show how a Bayesian approach can help identify critical uncertainties in components of R0 and how this uncertainty is propagated into the estimate of R0. Most notably, we find that different parameters dominate the uncertainty at different temperature regimes: bite rate from 15 degrees C to 25 degrees C; fecundity across all temperatures, but especially approximately 25-32 degrees C; mortality from 20 degrees C to 30 degrees C; parasite development rate at degrees 15-16 degrees C and again at approximately 33-35 degrees C. Focusing empirical studies on these parameters and corresponding temperature ranges would be the most efficient way to improve estimates of R0. While we focus on malaria, our methods apply to improving process-based models more generally, including epidemiological, physiological niche, and species distribution models.

Elastomeric negative acoustic contrast particles for capture, acoustophoretic transport, and confinement of cells in microfluidic systems.

We present a particle-based method for the immunospecific capture and confinement of cells using acoustic radiation forces. Ultrasonic standing waves in microfluidic systems have previously been used for the continuous focusing of cells in rapid screening and sorting applications. In aqueous fluids, cells typically exhibit positive acoustic contrast and are thus forced toward the pressure nodes of a standing wave. Conversely, elastomeric particles exhibit negative acoustic contrast and travel toward the pressure antinodes. We have developed a class of elastomeric particles that are synthesized in bulk using a simple nucleation and growth process, providing precise control over their size and functional properties. We demonstrate that the biofunctionalization of these particles can allow the capture and transport of cells to the pressure antinodes solely via acoustic radiation forces, which may enable new acoustics-based cell handling techniques such as the washing, labeling, and sorting of cells with minimal preparatory steps.

Influence of environmental, geographic, socio-demographic, and epidemiological factors on presence of malaria at the community level in two continents.

The interactions of environmental, geographic, socio-demographic, and epidemiological factors in shaping mosquito-borne disease transmission dynamics are complex and changeable, influencing the abundance and distribution of vectors and the pathogens they transmit. In this study, 27 years of cross-sectional malaria survey data (1990-2017) were used to examine the effects of these factors on Plasmodium falciparum and Plasmodium vivax malaria presence at the community level in Africa and Asia. Monthly long-term, open-source data for each factor were compiled and analyzed using generalized linear models and classification and regression trees. Both temperature and precipitation exhibited unimodal relationships with malaria, with a positive effect up to a point after which a negative effect was observed as temperature and precipitation increased. Overall decline in malaria from 2000 to 2012 was well captured by the models, as was the resurgence after that. The models also indicated higher malaria in regions with lower economic and development indicators. Malaria is driven by a combination of environmental, geographic, socioeconomic, and epidemiological factors, and in this study, we demonstrated two approaches to capturing this complexity of drivers within models. Identifying these key drivers, and describing their associations with malaria, provides key information to inform planning and prevention strategies and interventions to reduce malaria burden.