Structural and functional comparisons of salivary α-glucosidases from the mosquito vectors Aedes aegypti, Anopheles gambiae, and Culex quinquefasciatus

Mosquito vectors of medical importance both blood and sugar feed, and their saliva contains bioactive molecules that aid in both processes. Although it has been shown that the salivary glands of several mosquito species exhibit α-glucosidase activities, the specific enzymes responsible for sugar digestion remain understudied. We therefore expressed and purified three recombinant salivary α-glucosidases from the mosquito vectors Aedes aegypti, Anopheles gambiae, and Culex quinquefasciatus and compared their functions and structures. We found that all three enzymes were expressed in the salivary glands of their respective vectors and were secreted into the saliva. The proteins, as well as mosquito salivary gland extracts, exhibited α-glucosidase activity, and the recombinant enzymes displayed preference for sucrose compared to p-nitrophenyl-α-D-glucopyranoside. Finally, we solved the crystal structure of the Ae. aegypti α-glucosidase bound to two calcium ions at a 2.3 Ångstrom resolution. Molecular docking suggested that the Ae. aegypti α-glucosidase preferred di- or polysaccharides compared to monosaccharides, consistent with enzymatic activity assays. Comparing structural models between the three species revealed a high degree of similarity, suggesting similar functional properties. We conclude that the α-glucosidases studied herein are important enzymes for sugar digestion in three mosquito species.

Aedes aegypti D7 long salivary proteins modulate blood feeding and parasite infection

Mosquito saliva facilitates blood meal acquisition through pharmacologically active compounds that prevent host hemostasis and immune responses. Here, we generated two knockout (KO) mosquito lines by CRISPR/Cas9 to functionally characterize D7L1 and D7L2, two abundantly expressed salivary proteins from the yellow fever mosquito vector Aedes aegypti. The D7s bind and scavenge biogenic amines and eicosanoids involved in hemostasis at the bite site. The absence of D7 proteins in the salivary glands of KO mosquitoes was confirmed by mass spectrometry, enzyme-linked immunosorbent assay, and fluorescence microscopy of the salivary glands with specific antibodies. D7-KO mosquitoes had longer probing times than parental wildtypes. The differences in probing time were abolished when mutant mice resistant to inflammatory insults were used. These results confirmed the role of D7 proteins as leukotriene scavengers in vivo. We also investigated the role of D7 salivary proteins in Plasmodium gallinaceum infection and transmission. Both KO lines had significantly fewer oocysts per midgut. We hypothesize that the absence of D7 proteins in the midgut of KO mosquitoes might be responsible for creating a harsh environment for the parasite. The information generated by this work highlights the biological functionality of salivary gene products in blood feeding and pathogen infection. IMPORTANCE During blood feeding, mosquitoes inject saliva into the host skin, preventing hemostasis and inflammatory responses. D7 proteins are among the most abundant components of the saliva of blood-feeding arthropods. Aedes aegypti, the vector of yellow fever and dengue, expresses two D7 long-form salivary proteins: D7L1 and D7L2. These proteins bind and counteract hemostatic agonists such as biogenic amines and leukotrienes. D7L1 and D7L2 knockout mosquitoes showed prolonged probing times and carried significantly less Plasmodium gallinaceum oocysts per midgut than wild-type mosquitoes. We hypothesize that reingested D7s play a vital role in the midgut microenvironment with important consequences for pathogen infection and transmission.

Quantifying Fitness Costs in Transgenic Aedes aegypti Mosquitoes

Transgenic mosquitoes often display fitness costs compared to their wild-type counterparts. In this regard, fitness cost studies involve collecting life parameter data from genetically modified mosquitoes and comparing them to mosquitoes lacking transgenes from the same genetic background. This manuscript illustrates how to measure common life history traits in the mosquito Aedes aegypti, including fecundity, wing size and shape, fertility, sex ratio, viability, development times, male contribution, and adult longevity. These parameters were chosen because they reflect reproductive success, are simple to measure, and are commonly reported in the literature. The representative results quantify fitness costs associated with either a gene knock-out or a single insertion of a gene drive element. Standardizing how life parameter data are collected is important because such data may be used to compare the health of transgenic mosquitoes generated across studies or to model the transgene fixation rate in a simulated wild-type mosquito population. Although this protocol is specific for transgenic Aedes aegypti, the protocol may also be used for other mosquito species or other experimental treatment conditions, with the caveat that certain biological contexts may require special adaptations.

Guianensin, a Simulium guianense salivary protein, has broad anti-hemostatic and anti-inflammatory properties

Background

Salivary glands from blood-feeding arthropods secrete several molecules that inhibit mammalian hemostasis and facilitate blood feeding and pathogen transmission. The salivary functions from Simulium guianense, the main vector of Onchocerciasis in South America, remain largely understudied. Here, we have characterized a salivary protease inhibitor (Guianensin) from the blackfly Simulium guianense.

Materials and methods

A combination of bioinformatic and biophysical analyses, recombinant protein production, in vitro and in vivo experiments were utilized to characterize the molecula mechanism of action of Guianensin. Kinetics of Guianensin interaction with proteases involved in vertebrate inflammation and coagulation were carried out by surface plasmon resonance and isothermal titration calorimetry. Plasma recalcification and coagulometry and tail bleeding assays were performed to understand the role of Guianensin in coagulation.

Results

Guianensin was identified in the sialotranscriptome of adult S. guianense flies and belongs to the Kunitz domain of protease inhibitors. It targets various serine proteases involved in hemostasis and inflammation. Binding to these enzymes is highly specific to the catalytic site and is not detectable for their zymogens, the catalytic site-blocked human coagulation factor Xa (FXa), or thrombin. Accordingly, Guianensin significantly increased both PT (Prothrombin time) and aPTT (Activated partial thromboplastin time) in human plasma and consequently increased blood clotting time ex vivo. Guianensin also inhibited prothrombinase activity on endothelial cells. We show that Guianensin acts as a potent anti-inflammatory molecule on FXa-induced paw edema formation in mice.

Conclusion

The information generated by this work highlights the biological functionality of Guianensin as an antithrombotic and anti-inflammatory protein that may play significant roles in blood feeding and pathogen transmission.

Evaluation of Aedes aegypti Penetration, Probing, and Feeding Times on Mice

In mosquitoes, the intradermal search for vertebrate blood (probing time) corresponds to the time taken from initial insertion of the mouthparts in the skin until visualization of the initial engorgement of blood in the midgut. Probing time evaluation provides useful information on the ability of a mosquito to initiate successful blood feeding. In this protocol, we describe how to determine feeding parameters in Aedes aegypti, a widely distributed mosquito that transmits several deadly pathogens, including yellow fever, dengue, Zika, and Chikungunya viruses. We focus on the different steps of a blood feeding event, including penetration, probing, interprobing, and feeding time. Penetration time corresponds to the insertion of the stylets into the host skin and usually lasts <10 sec. Probing time or intradermal search for blood involves saliva secretion into the skin. Some researchers group penetration and probing time as the exploratory phase for blood. Feeding time is an active phase of blood ingestion and engorgement. Feeding parameters depend on mosquito behaviors and these measurements are visually taken by the investigator. We include a video that provides a close look at a mosquito feeding event in which penetration, probing, and feeding times can be observed. To record these experimental times, one must closely watch the mosquito feeding behavior including stylet penetration in the host skin, visualization of the first traces of blood in the midgut, engorgement of the midgut, and removal of stylets from the skin.

Evaluation of Aedes aegypti Feeding Status

Female mosquitoes need vertebrate blood for egg development. Evaluating mosquito behavior is essential for determining the ability of a mosquito to blood feed. Blood feeding experiments are often performed using artificial membrane feeders; however, such experiments do not represent realistic scenarios in which a mosquito injects saliva into the host to prevent host hemostatic responses. Vertebrate animal models are therefore more representative of a natural blood feeding event. Here, we describe a methodology to evaluate mosquito blood feeding success that can be used to compare blood feeding between mosquito groups-for instance, wild-type versus transgenic mosquitoes lacking salivary proteins or field-collected versus laboratory-reared mosquitoes. We also include a simple procedure to measure blood meal size, allowing for a more quantitative assessment of feeding status. The volume of ingested blood directly affects mosquito fecundity and fertility, important markers of fitness. The methods described herein can be used to evaluate transmission-blocking vaccines, insecticides, or fitness costs associated with transgenic mosquitoes.

Determination of Mosquito Probing and Feeding Time to Evaluate Mosquito Blood Feeding

Hematophagous arthropods are animals that feed on vertebrate blood for egg production. Mosquitoes must pierce the host skin, locate blood vessels, and extract blood without being noticed. Mosquito stylets lacerate host tissues, triggering the activation of the three branches of hemostasis, or stopping of blood flow: vasoconstriction, platelet aggregation, and coagulation. Mosquitoes inject saliva into the host skin during their intradermal search for blood (also called probing), and salivary proteins counteract hemostasis. Blood feeding dynamics have been traditionally described by observational studies, in which researchers using magnifying glasses watched mosquitoes in the act of blood feeding. These studies provided the foundation for protocols to evaluate mosquito blood feeding in a more quantitative manner. Here, we introduce mosquito blood feeding biology with a focus on the feeding steps, which include penetration, probing, and feeding. Understanding blood feeding dynamics is crucial for evaluating probing time and other relevant parameters derived from blood feeding, such as blood meal size, fecundity, and fertility. Other considerations, including the relationship between probing and pathogen transmission and novel technologies to address blood feeding, are also discussed.

Assessing single-locus CRISPR/Cas9-based gene drive variants in the mosquito Aedes aegypti via single-generation crosses and modeling

The yellow fever mosquito Aedes aegypti is a major vector of arthropod-borne viruses, including dengue, chikungunya, and Zika viruses. A novel approach to mitigate arboviral infections is to generate mosquitoes refractory to infection by overexpressing antiviral effector molecules. Such an approach requires a mechanism to spread these antiviral effectors through a population, for example, by using CRISPR/Cas9-based gene drive systems. Critical to the design of a single-locus autonomous gene drive is that the selected genomic locus is amenable to both gene drive and appropriate expression of the antiviral effector. In our study, we used reverse engineering to target 2 intergenic genomic loci, which had previously shown to be highly permissive for antiviral effector gene expression, and we further investigated the use of 3 promoters (nanos, β2-tubulin, or zpg) for Cas9 expression. We then quantified the accrual of insertions or deletions (indels) after single-generation crossings, measured maternal effects, and assessed fitness costs associated with various transgenic lines to model the rate of gene drive fixation. Overall, MGDrivE modeling suggested that when an autonomous gene drive is placed into an intergenic locus, the gene drive system will eventually be blocked by the accrual of gene drive blocking resistance alleles and ultimately be lost in the population. Moreover, while genomic locus and promoter selection were critically important for the initial establishment of the autonomous gene drive, it was the fitness of the gene drive line that most strongly influenced the persistence of the gene drive in the simulated population. As such, we propose that when autonomous CRISPR/Cas9-based gene drive systems are anchored in an intergenic locus, they temporarily result in a strong population replacement effect, but as gene drive-blocking indels accrue, the gene drive becomes exhausted due to the fixation of CRISPR resistance alleles.

A Simple Method for Immunohistochemistry and Imaging of Mosquito Salivary Glands

Immunohistochemistry is a valuable technique that provides information on protein localization and interactions in tissues. Mosquito salivary gland immunohistochemistry requires the meticulous dissection of a delicate tissue. The integrity of the salivary glands must be closely monitored throughout the entire process to prevent structural damage and loss of saliva. This protocol describes a series of simple steps to perform salivary gland immunohistochemistry including tissue dissection, permeabilization, immunostaining, mounting, and imaging by confocal microscopy.

Performing Immunohistochemistry in Mosquito Salivary Glands

Studying protein localization in mosquito salivary glands provides novel insights on the function and physiological relevance of salivary proteins and also provides an avenue to study interactions between mosquitoes and pathogens. Salivary proteins display compartmentalization. For example, proteins involved in blood feeding are stored in the medial and distal lateral lobes, whereas proteins related to sugar metabolism localize to the proximal portion of the lateral lobes. Immunohistochemistry assays use antibodies raised against recombinant salivary proteins to reveal the protein localization and interactions within the tissue. In this assay, permeabilization of the salivary glands allows the antibodies to enter the cells and bind their target proteins. The primary antibody-antigen complexes are later marked with fluorescently labeled secondary antibodies. Antibodies that recognize pathogen-specific proteins can also be incorporated in these assays, providing information about pathogen localization within the salivary glands or pathogen interactions with mosquito salivary proteins. Here, we introduce immunohistochemistry assays for use in mosquito salivary glands.

Aedes aegypti sialokinin facilitates mosquito blood feeding and modulates host immunity and vascular biology

Saliva from mosquitoes contains vasodilators that antagonize vasoconstrictors produced at the bite site. Sialokinin is a vasodilator present in the saliva of Aedes aegypti. Here, we investigate its function and describe its mechanism of action during blood feeding. Sialokinin induces nitric oxide release similar to substance P. Sialokinin-KO mosquitoes produce lower blood perfusion than parental mosquitoes at the bite site during probing and have significantly longer probing times, which result in lower blood feeding success. In contrast, there is no difference in feeding between KO and parental mosquitoes when using artificial membrane feeders or mice that are treated with a substance P receptor antagonist, confirming that sialokinin interferes with host hemostasis via NK1R signaling. While sialokinin-KO saliva does not affect virus infection in vitro, it stimulates macrophages and inhibits leukocyte recruitment in vivo. This work highlights the biological functionality of salivary proteins in blood feeding.

Aedes aegypti Piwi4 Structural Features Are Necessary for RNA Binding and Nuclear Localization

The PIWI-interacting RNA (piRNA) pathway provides an RNA interference (RNAi) mechanism known from Drosophila studies to maintain the integrity of the germline genome by silencing transposable elements (TE). Aedes aegypti mosquitoes, which are the key vectors of several arthropod-borne viruses, exhibit an expanded repertoire of Piwi proteins involved in the piRNA pathway, suggesting functional divergence. Here, we investigate RNA-binding dynamics and subcellular localization of A. aegypti Piwi4 (AePiwi4), a Piwi protein involved in antiviral immunity and embryonic development, to better understand its function. We found that AePiwi4 PAZ (Piwi/Argonaute/Zwille), the domain that binds the 3′ ends of piRNAs, bound to mature (3′ 2′ O-methylated) and unmethylated RNAs with similar micromolar affinities (K_D = 1.7 ± 0.8 μM and K_D of 5.0 ± 2.2 μM, respectively; p = 0.05) in a sequence independent manner. Through site-directed mutagenesis studies, we identified highly conserved residues involved in RNA binding and found that subtle changes in the amino acids flanking the binding pocket across PAZ proteins have significant impacts on binding behaviors, likely by impacting the protein secondary structure. We also analyzed AePiwi4 subcellular localization in mosquito tissues. We found that the protein is both cytoplasmic and nuclear, and we identified an AePiwi4 nuclear localization signal (NLS) in the N-terminal region of the protein. Taken together, these studies provide insights on the dynamic role of AePiwi4 in RNAi and pave the way for future studies aimed at understanding Piwi interactions with diverse RNA populations.

Intrathoracic Inoculation of Zika Virus in Aedes aegypti

Aedes aegypti mosquitoes are the main vectors of many medically relevant arthropod-borne (arbo) viruses, including Zika (ZIKV), dengue (DENV), and yellow fever (YFV). Vector competence studies with Ae. aegypti often involve challenging mosquitoes with an artificial bloodmeal containing virus and later quantifying viral titer or infectious plaque-forming units (PFU) in various mosquito tissues at relevant time points post-infection. However, Ae. aegypti mosquitoes are known to exhibit midgut infection and escape barriers (MIB and MEB, respectively), which influence the prevalence and titer of a disseminated infection and can introduce unwanted variability into studies analyzing tissues such as the salivary glands. To surmount this challenge, we describe herein a protocol for the intrathoracic inoculation of ZIKV in Ae. aegypti. This method bypasses the midgut, which leads to a more rapid and higher proportion of disseminated infections in comparison to oral challenge, and mosquitoes become infected with a consistent dose of virus. Our protocol is advantageous for studies that need a large sample size of infected mosquitoes, need to bypass the midgut, or are analyzing salivary gland infection or escape barriers. Graphic abstract: Cartoon depiction of Aedes aegypti intrathoracic inoculation. Figure made with Biorender.com.

Paratransgenic manipulation of a tsetse microRNA alters the physiological homeostasis of the fly's midgut environment

Tsetse flies are vectors of parasitic African trypanosomes, the etiological agents of human and animal African trypanosomoses. Current disease control methods include fly-repelling pesticides, fly trapping, and chemotherapeutic treatment of infected people and animals. Inhibiting tsetse's ability to transmit trypanosomes by strengthening the fly's natural barriers can serve as an alternative approach to reduce disease. The peritrophic matrix (PM) is a chitinous and proteinaceous barrier that lines the insect midgut and serves as a protective barrier that inhibits infection with pathogens. African trypanosomes must cross tsetse's PM in order to establish an infection in the fly, and PM structural integrity negatively correlates with trypanosome infection outcomes. Bloodstream form trypanosomes shed variant surface glycoproteins (VSG) into tsetse's gut lumen early during the infection establishment, and free VSG molecules are internalized by the fly's PM-producing cardia. This process results in a reduction in the expression of a tsetse microRNA (miR275) and a sequential molecular cascade that compromises PM integrity. miRNAs are small non-coding RNAs that are critical in regulating many physiological processes. In the present study, we investigated the role(s) of tsetse miR275 by developing a paratransgenic expression system that employs tsetse's facultative bacterial endosymbiont, Sodalis glossinidius, to express tandem antagomir-275 repeats (or miR275 sponges). This system induces a constitutive, 40% reduction in miR275 transcript abundance in the fly's midgut and results in obstructed blood digestion (gut weights increased by 52%), a significant increase (p-value < 0.0001) in fly survival following infection with an entomopathogenic bacteria, and a 78% increase in trypanosome infection prevalence. RNA sequencing of cardia and midgut tissues from paratransgenic tsetse confirmed that miR275 regulates processes related to the expression of PM-associated proteins and digestive enzymes as well as genes that encode abundant secretory proteins. Our study demonstrates that paratransgenesis can be employed to study microRNA regulated pathways in arthropods that house symbiotic bacteria.

First steps: Parent health behaviours related to children's foot health

Good foot health throughout childhood is important but remains poorly understood with few studies exploring this topic. The aim of this study was to define parents' knowledge, practices and health-related perceptions of children's feet. A qualitative design was adopted. Semi-structured, one-to-one interviews were carried out with parents of children aged five years and under, recruited from South East and North West of England. Interviews explored parents' views, beliefs and understanding of foot health in infancy and early childhood. Transcripts of the interviews were analysed using thematic analysis. Eighteen interviews were conducted. Seven themes were identified relating to (1) parents belief and knowledge about children's foot health; (2) how parents use and share foot health information; (3) activities for supporting foot health and development; (4) footwear choices, beliefs and influences; (5) the way they access health professionals; (6) the way they search for foot health information and (7) developing practice(s) to support parents. The study provides the first insight into how parents view foot health in early infancy and childhood. The findings highlight the key foot health beliefs important to parents, how they learn about and what influences their decision-making about caring for children's feet, the way parents receive and seek information, and how they access support for foot health concerns. The findings highlight the need for accurate, clear and consistent foot health messages, and the important role health professionals have in signposting parents towards reliable and informative sources on foot health.

Plasmodium falciparum evades immunity of anopheline mosquitoes by interacting with a Pfs47 midgut receptor

The surface protein Pfs47 allows Plasmodium falciparum parasites to survive and be transmitted by making them "undetectable" to the mosquito immune system. P. falciparum parasites express Pfs47 haplotypes compatible with their sympatric vectors, while those with incompatible haplotypes are eliminated by the mosquito. We proposed that Pfs47 serves as a "key" that mediates immune evasion by interacting with a mosquito receptor "the lock," which differs in evolutionarily divergent anopheline mosquitoes. Recombinant Pfs47 (rPfs47) was used to identify the mosquito Pfs47 receptor protein (P47Rec) using far-Western analysis. rPfs47 bound to a single 31-kDa band and the identity of this protein was determined by mass spectrometry. The mosquito P47Rec has two natterin-like domains and binds to Pfs47 with high affinity (17 to 32 nM). P47Rec is a highly conserved protein with submicrovillar localization in midgut cells. It has structural homology to a cytoskeleton-interacting protein and accumulates at the site of ookinete invasion. Silencing P47Rec expression reduced P. falciparum infection, indicating that the interaction of Pfs47 with the receptor is critical for parasite survival. The binding specificity of P47Rec from distant anophelines (Anopheles gambiae, Anopheles dirus, and Anopheles albimanus) with Pfs47-Africa (GB4) and Pfs47-South America (7G8) haplotypes was evaluated, and it is in agreement with the previously documented compatibility between P. falciparum parasites expressing different Pfs47 haplotypes and these three anopheline species. Our findings give further support to the role of Pfs47 in the adaptation of P. falciparum to different vectors.

Engineering a Virus-Like Particle as an Antigenic Platform for a Pfs47-Targeted Malaria Transmission-Blocking Vaccine

We recently characterized Pfs47, a protein expressed on the surface of sexual stages and ookinetes of Plasmodium falciparum, as a malaria transmission-blocking vaccine (TBV) target. Mice immunization induced antibodies that conferred strong transmission-reducing activity (TRA) at a concentration of 200 μg/mL. Here, we sought to optimize the Pfs47 vaccine to elicit higher titers of high-affinity antibodies, capable of inducing strong TRA at a lower concentration. We report the development and evaluation of a Pfs47-based virus-like particle (VLP) vaccine generated by conjugating our 58 amino acid Pfs47 antigen to Acinetobacter phage AP205-VLP using the SpyCatcher:SpyTag adaptor system. AP205-Pfs47 complexes (VLP-P47) formed particles of ~22 nm diameter that reacted with polyclonal anti-Pfs47 antibodies, indicating that the antigen was accessible on the surface of the particle. Mice immunized with VLP-P47 followed by a boost with Pfs47 monomer induced significantly higher antibody titers, with higher binding affinity to Pfs47, than mice that received two immunizations with either VLP-P47 (VLP-P47/VLP-P47) or the Pfs47 monomer (P47/P47). Purified IgG from VLP-P47/P47 mice had strong TRA (83-98%) at concentrations as low as 5 μg/mL. These results indicate that conjugating the Pfs47 antigen to AP205-VLP significantly enhanced antigenicity and confirm the potential of Pfs47 as a TBV candidate.

Work participation, mobility and foot symptoms in people with systemic lupus erythematosus: findings of a UK national survey

Objective

The aim of this study was to investigate whether foot and lower limb related symptoms were associated with work participation and poor mobility in people with Systemic Lupus Erythematosus (SLE).

Method

A quantitative, cross-sectional, self-reported survey design was utilised. People with SLE from six United Kingdom (UK) treatment centres and a national register were invited to complete a survey about lower limb and foot health, work participation and mobility. Data collected included work status and the prevalence of foot symptoms. The focus of the analyses was to explore potential associations between poor foot health work non-participation.

Results

In total, 182 useable surveys were returned. Seventy-nine respondents reported themselves as employed and 32 reported work non-participation. The remaining were retired due to age or reported work non-participation for other reasons. Work non-participation due to foot symptoms was significantly associated with difficulty walking (p = 0.024), past episodes of foot swelling (p = 0.041), and past episodes of foot ulceration (p = 0.018). There was a significant increase in foot disability scores amongst those not working (mean 18.13, 95% CI: 14.85–21.41) compared to those employed (mean 10.16, 95% CI: 8.11–12.21).

Conclusions

Twenty-nine% of people with SLE reported work non-participation because of lower limb or foot problems. Our results suggest that foot health and mobility may be important contributors to a persons’ ability to remain in work and should be considered as part of a clinical assessment.

A Comparison of the in Vitro and in Vivo Thrombogenic Activity of Factor IX Concentrates Using Stasis (Wessler) and Non-Stasis Rabbit Models

The thrombogenic effects of selected factor IX concentrates were evaluated in two rabbit models; the Wessler stasis model and a novel non-stasis model. Concentrates active in either the NAPTT or TGt50 in vitro tests of potential thrombogenicity, or both, caused thrombus formation in the Wessler technique and activation of the coagulation system in the non-stasis model. A concentrate with low activity in both in vitro tests did not have thrombogenic effects in vivo, at the chosen dose. Results in the non-stasis model suggested that the thrombogenic effects of factor IX concentrates may occur by at least two mechanisms. A concentrate prepared from platelet-rich plasma and a pyrogenic concentrate were also tested and found to have no thrombogenic effect in vivo.

These studies justify the use of the NAPTT and TGt50 in vitro tests for the screening of factor IX concentrates prior to clinical use.

Antibody targeting of a specific region of Pfs47 blocks Plasmodium falciparum malaria transmission

Transmission-blocking vaccines are based on eliciting antibody responses in the vertebrate host that disrupt parasite development in the mosquito vector and prevent malaria transmission. The surface protein Pfs47 is present in Plasmodium falciparum gametocytes and female gametes. The potential of Pfs47 as a vaccine target was evaluated. Soluble full-length recombinant protein, consisting of three domains, was expressed in E. coli as a thioredoxin fusion (T-Pfs47). The protein was immunogenic, and polyclonal and monoclonal antibodies (mAb) were obtained, but they did not confer transmission blocking activity (TBA). All fourteen mAb targeted either domains 1 or 3, but not domain 2 (D2), and immune reactivity to D2 was also very low in polyclonal mouse IgG after T-Pfs47 immunization. Disruption of the predicted disulfide bond in D2, by replacing cysteines for alanines (C230A and C260A), allowed expression of recombinant D2 protein in E. coli. A combination of mAbs targeting D2, and deletion proteins from this domain, allowed us to map a central 52 amino acid (aa) region where antibody binding confers strong TBA (78-99%). This 52 aa antigen is immunogenic and well conserved, with only seven haplotypes world-wide that share 96-98% identity. Neither human complement nor the mosquito complement-like system are required for the observed TBA. A dramatic reduction in ookinete numbers and ookinete-specific transcripts was observed, suggesting that the antibodies are interacting with female gametocytes and preventing fertilization.

National profile of foot orthotic provision in the United Kingdom, part 2: podiatrist, orthotist and physiotherapy practices

Background

A national survey recently provided the first description of foot orthotic provision in the United Kingdom. This article aims to profile and compare the foot orthoses practice of podiatrists, orthotists and physiotherapists within the current provision.

Method

Quantitative data were collected from podiatrists, orthotists and physiotherapists via an online questionnaire. The topics, questions and answers were developed through a series of pilot phases. The professions were targeted through electronic and printed materials advertising the survey. Data were captured over a 10 month period in 2016. Differences between professions were investigated using Chi squared and Fischer’s exact tests, and regression analysis was used to predict the likelihood of each aspect of practice in each of the three professions.

Results

Responses from 357 podiatrists, 93 orthotists and 49 physiotherapists were included in the analysis. The results reveal statistically significant differences in employment and clinical arrangements, the clinical populations treated, and the nature and volume of foot orthoses caseload.

Conclusion

Podiatrists, orthotists and physiotherapists provide foot orthoses to important clinical populations in both a prevention and treatment capacity. Their working context, scope of practice and mix of clinical caseload differs significantly, although there are areas of overlap. Addressing variations in practice could align this collective workforce to national allied health policy.

Electronic supplementary material

The online version of this article (10.1186/s13047-018-0250-9) contains supplementary material, which is available to authorized users.

Patients’ experiences of lupus-related foot problems: a qualitative investigation

Background

Systemic lupus erythematosus (SLE) can present with a variety of symptoms. Previous research has shown there is a high prevalence of lower limb and foot problems in patients with SLE associated with the musculoskeletal, vascular and neurological changes. Furthermore, there is a high prevalence of infections affecting the feet and a range of common skin and nail problems. However, it is not known how these foot problems impact upon people’s lives. Therefore, we aimed to explore this using a qualitative approach.

Method

Following ethical approval, 12 participants were recruited who had a diagnosis of SLE, current and/or past experience of foot problems and were over 18 years in age. Following consent, interviews were carried out with an interpretivist phenomenological approach to both data collection and analysis.

Results

Seven themes provide insight into: foot problems and symptoms; the impact of these foot problems and symptoms on activities; disclosure and diagnosis of foot problems; treatment of foot problems and symptoms; perceived barriers to professional footcare; unanswered questions about feet and footcare; and identification of the need for professional footcare and footcare advice.

Conclusion

These participants tend to “self-treat” rather than disclose that they may need professional footcare. A lack of focus upon foot health within a medical consultation is attributed to the participant’s belief that it is not within the doctor’s role, even though it is noted to contribute to reduced daily activity. There is a need for feet to be included as a part of patient monitoring and for foot health management to be made accessible for people with SLE.

National profile of foot orthotic provision in the United Kingdom, part 1: practitioners and scope of practice

Background

Foot orthoses have been advocated in the management of a wide range of clinical foot and lower limb problems and are within the scope of podiatry, orthotic and physiotherapy practice. Previous reports into the provision of orthoses have consistently identified significant issues with services and devices, but data were never specific to foot orthoses. The aim of this first of a series of papers was to report the first ever national multi professional profile of foot orthosis provision in the United Kingdom.

Methods

Quantitative and qualitative data were collected from podiatrists, orthotists and physiotherapists via an online questionnaire. The topics, questions and answers were developed through a series of pilot phases. The professions were targeted through electronic and printed materials. Data were captured over a 10 month period in 2016.

Results

A total of 499 responses were included in analysis, including 357 podiatrists, 93 orthotists and 49 physiotherapists. The results reveal wide ranging practices across podiatrists, orthotists and physiotherapists, provision of orthoses through different health care departments (uni and multidisciplinary), for different health conditions (acute and chronic), and involving different types of orthoses (prefabricated and customised).

Conclusion

Foot orthoses in the United Kingdom are provided in areas of well recognised health and rehabilitation priorities. A wide range of orthotic devices and practices are employed and different professions provide foot orthoses in different ways.

Electronic supplementary material

The online version of this article (doi:10.1186/s13047-017-0215-4) contains supplementary material, which is available to authorized users.

The prevalence of self-reported lower limb and foot health problems experienced by participants with systemic lupus erythematosus: Results of a UK national survey

Objective The main aim of this survey was to determine the frequency of self-reported lower limb or foot and ankle complications experienced by participants with systemic lupus erythematosus (SLE). A secondary aim was to determine the frequency of treatments that have been received or that participants with SLE may like to receive if offered. Method A quantitative, cross-sectional, self-reported survey design was utilized. The developed survey was checked for face and content validity prior to patient partner cognitive debriefing in order to ensure usability, understanding of the process of completion and of the questions posed. The full protocol for survey development has been published previously. Results This is the first comprehensive national UK survey of lower limb and foot health problems reported by participants with SLE. A high prevalence of vascular, dermatological and musculoskeletal complications was reported by survey respondents. Additionally, whilst the relative prevalence of sensory loss was low, a quarter of people reported having had a fall related to changes in foot sensation demonstrating a previously unknown rate and cause of falls. Conclusion Complications related to vascular, dermatological and musculoskeletal health are identified as particularly prevalent in participants with SLE. Further, there is a suggestion that the provision of interventions to maintain lower limb health is highly varied and lacks national standardization, despite there being a strong indication of participant reported need. The findings of this work can be used to inform care guideline development in addition to identifying areas for future research.

Health literacy and pap testing in insured women

Several studies have found a link between health literacy and participation in cancer screening. Most, however, have relied on self-report to determine screening status. Further, until now, health literacy measures have assessed print literacy only. The purpose of this study was to examine the relationship between participation in cervical cancer screening (Papanicolaou [Pap] testing) and two forms of health literacy-reading and listening. A demographically diverse sample was recruited from a pool of insured women in Georgia, Massachusetts, Hawaii, and Colorado between June 2009 and April 2010. Health literacy was assessed using the Cancer Message Literacy Test-Listening and the Cancer Message Literacy Test-Reading. Adherence to cervical cancer screening was ascertained through electronic administrative data on Pap test utilization. The relationship between health literacy and adherence to evidence-based recommendations for Pap testing was examined using multivariate logistic regression models. Data from 527 women aged 40 to 65 were analyzed and are reported here. Of these 527 women, 397 (75 %) were up to date with Pap testing. Higher health literacy scores for listening but not reading predicted being up to date. The fact that health literacy listening was associated with screening behavior even in this insured population suggests that it has independent effects beyond those of access to care. Patients who have difficulty understanding spoken recommendations about cancer screening may be at risk for underutilizing screening as a result.

'Focus on feet'--the effects of systemic lupus erythematosus: a narrative review of the literature

BACKGROUND

The manifestations of systemic lupus erythematosus (SLE) vary between individuals, from the severe and life-threatening renal and central nervous system involvement, to the involvement of skin, musculoskeletal and vascular system, and the complications of infection influencing the quality of life. However, as specific manifestations affecting the lower limb are perceived as receiving little focus, the purpose of this narrative literature review is to identify the specific factors associated with SLE that may have implications for lower limb and foot morbidity.

METHOD

A structured search of databases was conducted. The inclusion was restricted to publications in the English language, those that specifically investigate the feet as affected with SLE. No restriction on year of publication was imposed to reduce publication bias and to capture as many publication in relation to feet.

RESULTS

Eleven papers fulfilled the inclusion criteria. There were seven additional papers that made observations related to the articular or vascular complications of the feet. This narrative review provides some information on how SLE affects the lower limb and foot in relation to the musculoskeletal and vascular systems. However, there is a lack of literature that specifically focuses on all the manifestations of SLE and the complications associated with its management.

DISCUSSION

There are indications that SLE affects lower limb and foot morbidity but the scale of these problems is unclear and this is partly because of the absence of research and the lack of a 'gold standard' framework for the assessment of the lower limb and foot. In addition to clinical foot health assessment, ultrasonography may be a useful alternative to plain film radiography or magnetic resonance imaging (MRI) in capturing the extent of articular and extra-articular manifestations. Further, the Ankle Brachial Pressure Index (ABPI) may be useful in identifying those with atherosclerosis and ischaemia.

CONCLUSION

There are indications that SLE affects lower limb and foot morbidity but the scale of these problems and effective management of them is unclear. Therefore, further research is warranted in order to better understand the impact of SLE on the foot and lower limb and its impact on quality of life.

The burden of unscheduled health care for asthma in Latin America

OBJECTIVES

To determine the level and cost of unscheduled health care resource use in adults and children across all asthma symptom severities in Latin America.

METHODS

The level and cost of health care resource use were analysed for 2074 patients with asthma included in the Asthma Insights and Reality in Latin America (AIRLA) survey from 10 Latin American countries. Health care resource use was multiplied by country-specific unit costs to estimate average per-patient annual costs. Patients were classified as adults (> or = 16 years) or children (<16 years), with disease severity categorized using a symptom severity index.

RESULTS

Persistent asthma symptoms were experienced by 53.1% of patients (50.1% of children and 54.6% of adults). In the year preceding the survey, 57.1% of patients required unscheduled health care resource use and 45.1% reported at least 1 emergency hospital contact. The percentage of patients reporting unscheduled health care resource use was greatest amongst those with severe persistent symptoms (71.9%) but it was also high in those with mild intermittent symptoms (45.7%). An average of 73.2% of annual costs of asthma-related health care for the 10 countries was due to unscheduled health care. Expenditure on unscheduled care was greatest amongst both adults and children with severe persistent asthma symptoms (US $558 and US $769, respectively). Adults and children with mild intermittent symptoms also incurred considerable unscheduled costs (US $204 and US $215, respectively).

CONCLUSIONS

Poorly controlled asthma imposes a considerable cost burden driven by unscheduled health care resource use in Latin America. Treatments to control asthma and reduce the need for unscheduled health care could reduce this cost in both adults and children.

Cell-penetrating-peptide-mediated siRNA lung delivery

The therapeutic application of siRNA (short interfering RNA) shows promise as an alternative approach to small-molecule inhibitors for the treatment of human disease. However, the major obstacle to its use has been the difficulty in delivering these large anionic molecules in vivo. A potential approach to solving this problem is the chemical conjugation of siRNA to the cationic CPPs (cell-penetrating peptides), Tat-(48–60) (transactivator of transcription) and penetratin, which have been shown previously to mediate protein and peptide delivery in a host of animal models. In this transaction, we review recent studies on the utility of siRNA for the investigation of protein function in the airways/lung. We show that, despite previous studies showing the utility of cationic CPPs in vitro, conjugation of siRNA to Tat-(48–60) and penetratin failed to increase residual siRNA-mediated knockdown of p38 MAPK (mitogen-activated protein kinase) (MAPK14) mRNA in mouse lung in vivo. Significantly, we will also discuss potential non-specific actions and the induction of immunological responses by CPPs and their conjugates and how this might limit their application for siRNA-mediated delivery in vivo.

Health status impairment and costs associated with COPD exacerbation managed in hospital

Exacerbations of chronic obstructive pulmonary disease (COPD) have serious health consequences for patients and are strongly associated with unscheduled healthcare resource use. This study used a preference-based quality of life measure questionnaire (EQ-5D) to evaluate the impact of exacerbation on health status and utility during a patient's admission to hospital and short-term follow-up. Costs of admission were calculated. In total, 149 patients consented to take part in the study representing 222 admissions to hospital. At admission patients reported high levels of problems for all dimensions of the EQ-5D. Mean utility (-0.077) and Visual Analogue Scale (25.9) values indicated great impairment, with 61% of patients having a negative utility value representing a health state equivalent to 'worse than death' at admission. Many problems were still reported at discharge. By 3 months follow-up patients had deteriorated, with percentages of patients reporting problems in mobility (98%) and usual activity (88%) almost back up to admission levels. Health status and utility values were similar regardless of lung function at admission and at discharge. Approximately half of the patients in each category had a negative utility value at admission representing a health state 'worse than death', with similar levels of improvement by discharge. The mean cost of an admission was 2130.34 pounds (SD 1326.09) with only a mean of 110.37 pounds(5%) because of medication. No differences were noted by lung function category. In conclusion, all COPD patients requiring admission for an exacerbation suffer a serious deterioration in health status which, although improves during admission, notably deteriorates by 3 months postdischarge.

A clinical trial of specialist footwear for patients with rheumatoid arthritis

OBJECTIVES

The structural and functional changes in the RA foot often affect the patient's gait and mobility, impacting on the patient's quality of life. Successful management of these foot pathologies and resultant problems can involve the provision of specialist therapeutic footwear. The aim of the study was to evaluate the value of a new footwear design based on patients' opinions compared with a traditional footwear design.

METHOD

A total of 80 patients with RA of 5 yrs or more duration, foot deformity, difficulty in being able to obtain suitable retail footwear and self-reported foot pain were recruited. Patients were randomly assigned to either an intervention group (new design) or the control group (traditional design). Patients completed two specific health-related quality of life scales (Foot Health Status Questionnaire and the Foot Function Index) at baseline and after 12 weeks.

RESULTS

Only 36 patients completed the trial. Ten refused the footwear outright and 34 withdrew from the study after the footwear was supplied, due to either non-footwear related problems or reasons related to the footwear. Both the specific health-related quality of life scales demonstrated significant improvement from baseline to week 12 with the intervention group (P < 0.05). There was no significant difference in both specific health-related quality of life scales after week 12 with the traditional group (P > 0.05).

CONCLUSIONS

Improvement in pain and patient satisfaction with the new design of footwear for patients with RA over the traditional design indicates the importance of patient involvement in the design process and throughout the process of supplying and monitoring the footwear. The fact that the new-design shoe was based on patients' involvement in the design process in a previous study may be the most important factor in its success. In order to meet the clinical goals of this footwear the patients need to wear them, and to achieve this the patients' requirements need to be acknowledged.

Are outcomes the same with all dry powder inhalers?

Most clinicians and patients would intuitively say that the inhaler device used influences the outcome achieved in asthma. However, it is important to have objective evidence to support or refute this view. Systematic reviews have suggested that there is no difference in clinical effectiveness between dry powder inhalers and metered-dose inhalers. However, the studies included in the review were randomised clinical trials and not studies based on real-life clinical practice. In the real world, the efficacy of products as determined in a specified and well-monitored population is only one aspect of product performance--patient characteristics and behaviour are critical. Observational studies in real-world primary care settings suggest that the choice of inhaler device has an important impact on asthma outcomes. The IMS Mediplus database has now been used to compare outcomes among patients receiving initial maintenance therapy with beclometasone dipropionate administered via different dry powder inhalers. Patients using the DISKHALER dry powder inhaler used significantly less short-acting beta(2)-agonist than those using the ROTAHALER dry powder inhaler. This suggests a difference in the level of asthma control with the different devices, even when the same chemical entity is delivered. Real-world studies suggest, therefore, that outcomes are not always the same with all dry powder inhalers. This indicates the need for further studies to investigate the impact of inhaler device choice and the impact of switching between devices.

Patient perceptions of stock footwear design features

Patients with diseases which impact on foot health, for example diabetes and rheumatoid arthritis, are known to have some benefit from prescribed stock footwear with regards to clinical outcomes. Achieving this is not just about getting the footwear designed and fitted to meet the clinical needs, but it also requires that the patient wears the shoes. This means meeting the non-clinical needs or criteria of patients. The aim of this study was to compare perceptions of the same footwear between patients with diabetes and patients with rheumatoid arthritis (RA) with regard to specific design features. Fifty-four patients with RA and 40 patients with diabetes who required prescription footwear were asked to identify issues of importance, and to assess the features of five different pairs of stock footwear using a Likert scale scoring form. There was a difference between the RA and the diabetes groups with regards their overall requirements from the footwear with comfort being a priority in RA and style a priority for diabetes. Both groups rated the same footwear as overall best from the selection, but the scores suggest that there were features with the 'best' shoe which were not acceptable suggesting that even the 'best' shoe was a compromise This possibly indicates that existing footwear ranges do not meet all the patients' requirements. Patients have different perceptions with regard to what is important to them in terms of footwear with regards to the specific features of the footwear and one of the influences appears to be the underlying systemic disease. Patient-based criteria may be an important consideration in the design of the footwear.

Unscheduled healthcare resource use among asthma patients receiving low-dose inhaled corticosteroids maintenance treatment

This survey describes asthma control and unscheduled healthcare resource use (HCRU) among patients receiving low-dose inhaled corticosteroids (ICS) alone in five European countries and the USA. Physicians and patients completed forms collecting data on asthma symptoms, sudden increase in chest/respiratory symptoms, asthma-related HCRU, quality of life (QoL) and drug therapy. Fifty-seven per cent of patients on low-dose ICS alone had physician-rated moderate or severe asthma. Only 13% of patients receiving low-dose ICS alone achieved asthma control; 36% reported nocturnal wakening and 22% reported unscheduled healthcare services in the past year. Gender, symptom frequency, episodes of sudden increase in chest/respiratory symptoms and impaired QoL were all related to unscheduled healthcare resource utilisation. Many patients receiving low-dose ICS alone do not have adequate asthma control. Some patient characteristics were found to be significantly different, but not exclusive, between unscheduled healthcare resource users and non-users.

Enhanced immunopathology induced by very virulent infectious bursal disease virus

Immunohistochemical and flow cytometric analyses of the bursa, spleen and thymus following infection with the very virulent infectious bursal disease virus (vvIBDV) strain UK661 revealed discrete differences from classical virulent infectious bursal disease virus strains. Bu-1+, immunoglobulin (Ig)M+ and IgG+ cells were all depleted from the bursa, spleen and thymus, suggesting loss of both immature and mature B lymphocytes. Small numbers of Bu-1+ cells repopulated the bursa 14 days post-infection but few of these expressed IgM or IgG. A transient increase in macrophages at 3 to 5 days post-infection was followed by a later influx of CD4+ and CD8+ T cells into the bursa. Loss of cortical thymocytes during the acute phase of infection suggested disruption of the T-cell system. The results showed that vvIBDV strain UK661 caused earlier and more severe pathology than classical virulent strains of infectious bursal disease virus. The marked influx of T cells into the infected bursa indicates that cell-mediated immunity is likely to be important in the clearance of vvIBDV.

Nutritional changes among premenopausal women undertaking a soya based dietary intervention study in Hawaii

BACKGROUND

We conducted a 2-year nutritional intervention among premenopausal women. The goal was to incorporate two daily servings of soya into the regular diet. This report describes the dietary modifications and assesses their nutritional adequacy with regard to major nutrients.

METHODS

In this analysis of 100 intervention and 106 control subjects, women completed a validated food-frequency questionnaire at baseline; throughout the study, they participated in at least three unannounced 24-h recalls.

RESULTS

At randomization, both groups were similar in age and body weight, reported low soya intake, and did not differ by intake of major nutrients and foods. According to the 24-h recalls, women in the intervention group consumed nearly two servings of soya per day, while the control women remained at 0.2 servings. In comparison with the control group, the intervention group consumed fewer dairy products, primarily milk, but also less meat, nuts and seeds. As a result of the dietary modification, the intervention women consumed less-saturated fat and cholesterol and more protein, dietary fibre, calcium and vitamins than the control group.

CONCLUSION

These results suggest that women in the intervention group improved the overall quality of their diet by adding two servings of soya per day.

Mammographic densities in a one-year isoflavone intervention

The estrogenic and antiestrogenic effects of isoflavones, phytoestrogens contained in soy foods, have been proposed as mechanisms for the possible involvement of soy products in the development of breast cancer. We investigated the hypothesis that isoflavones reduce mammographic density, a predictor of breast cancer risk. We conducted a double-blind randomized trial in premenopausal women who received a daily 100 mg isoflavone supplement or a placebo over 12 months. Compliance with the study regimen was confirmed by urinary isoflavones and tablet counts. We used a computer-assisted method to measure mammographic density and paired t-tests to assess changes in mammographic characteristics from baseline to follow-up mammogram. Complete sets of mammograms were available for 30 women. The two groups differed by age and mammographic density at baseline, but were similar in body weight and nutritional intakes. We detected no significant changes either in the size of the dense areas or in the per cent densities. A non-significant decrease in breast area among intervention group subjects was probably the result of methodological issues in comparing mammograms taken under different conditions. In conclusion, our findings do not support the hypothesis that isoflavones decrease mammographic density during a one-year intervention. Although this exploratory study had limited power, it appears that isoflavones do not exert an estrogenic effect similar to hormone replacement therapy on mammographic density.

Knowledge of HIV/AIDS transmission and screening in United States blood donors

BACKGROUND

Increased knowledge of HIV transmission and behavioral and test screening may encourage high-risk blood donors to self-defer.

STUDY DESIGN AND METHODS

Knowledge of HIV transmission and screening and the association with demographics, screening test reactivity, and unreported deferrable risks (UDRs) was assessed by a 1998 anonymous mail survey sent to 92,581 blood donors, of whom 57 percent responded. Groups were compared by using weighted chi-square tests and logistic regression analysis.

RESULTS

Four percent of the donors thought that it was very likely or somewhat likely for a person to contract HIV from donating blood, and 20 percent perceived a similar risk from blood transfusion. Only 60 percent of the donors knew that the available screening tests may not detect a recent infection. Thirty-seven percent either did not know or felt it was acceptable to donate blood to obtain HIV testing. Those most likely to answer knowledge questions incorrectly were more likely to have a higher prevalence of test reactivity or UDRs and to be <or=25 years old, members of a minority, less educated, non-US-born, or first-time donors.

CONCLUSION

Innovative ways to increase donor understanding of the implications of risk behaviors and the limitations of current screening procedures should be developed. They might prevent high-risk individuals from donating blood.

What do patients attending HIV and GUM outpatient clinics want from service providers? Results from a large-scale consultation exercise in west London

Our objectives were to understand patient demographic profiles, experiences of care and opinions about services. A questionnaire survey of 202 HIV patients and 389 genitourinary medicine (GUM) outpatients attending clinics during one week in 1999 was undertaken at a clinical directorate of HIV/GUM in west London. HIV and GUM patients differed by age (over 30: 84% vs 39%), sex (male: 88% vs 51%), and attendance (attended 6+ times: 55% vs 14%). Most indicated that they were satisfied with the general standard of care (97% HIV patients vs 95% GUM patients). Several clinic features were rated essential. When indicating reasons they might leave in the future, HIV patients were more likely to select leading edge care factors, such as lack of up-to-date treatment (54%). More GUM patients selected factors relating to convenience, such as waiting times (58%). In conclusion, most HIV and GUM patients were satisfied with their care, but differing experiences and opinions need to be addressed when planning services.