71 Physical and chemical house entry barriers to enhance odour-baited trapping for malaria control

Background: Odour-baited mosquito trapping is a promising new malaria intervention that lures, traps and kills mosquitoes. However, mosquitoes still bypass the trapping system and enter easily accessible African households through the open eaves. In this study, house screening and a spatial repellent were used as a physical and chemical house entry barrier to determine whether these interventions can protect people from malaria mosquitoes by decreasing mosquito house entry and simultaneously increasing odourbaited trapping efficacy. Methods: In an experimental greenhouse in Kenya, two semi-field experiments were conducted. In the first experiment, three physical house adjustment interventions were tested against using no intervention: house screening (block); odour-baited trapping (pull) and both interventions (block-pull). In the second experiment, three chemical interventions were tested against using no intervention: a cotton band around the eaves impregnated with the spatial mosquito repellant Delta-undecalactone (push); odourbaited trapping (pull) and both interventions (push-pull). The effects of interventions were evaluated by comparing mean trap catches of the odour-baited trap outside, and mean mosquito house entry. Results: In the first experiment (block-pull), the chance of a mosquito getting caught by an odour-baited trap more than doubled (OR=2.163) when complementing odour-baited trapping with house screening (P<0,001). All interventions significantly reduced mosquito house entry (p<0,001), with the strongest protective effect for the combined intervention of house screening and odour-baited trapping (OR=0.10). The interventions of the second experiment did not have a significant effect on odour-baited trap catches (p=0.584), nor mosquito house entry (p>0.172). Discussion: This study shows that house screening could be a valuable addition to odourbaited mosquito trapping for malaria control and confirmed the strong effect of house screening on mosquito house entry. In contrast to other studies, a chemical barrier of Delta-undecalactone did not improve the protection against malaria mosquitoes. However, push-pull strategies might still be a viable alternative to house screening, since the absence of an effect might have been caused by an interaction of the intervention with the experimental environment.

Design of trials for interrupting the transmission of endemic pathogens

Many interventions against infectious diseases have geographically diffuse effects. This leads to contamination between arms in cluster-randomized trials (CRTs). Pathogen elimination is the goal of many intervention programs against infectious agents, but contamination means that standard CRT designs and analyses do not provide inferences about the potential of interventions to interrupt pathogen transmission at maximum scale-up.; A generic model of disease transmission was used to simulate infections in stepped wedge cluster-randomized trials (SWCRTs) of a transmission-reducing intervention, where the intervention has spatially diffuse effects. Simulations of such trials were then used to examine the potential of such designs for providing generalizable causal inferences about the impact of such interventions, including measurements of the contamination effects. The simulations were applied to the geography of Rusinga Island, Lake Victoria, Kenya, the site of the SolarMal trial on the use of odor-baited mosquito traps to eliminate Plasmodium falciparum malaria. These were used to compare variants in the proposed SWCRT designs for the SolarMal trial.; Measures of contamination effects were found that could be assessed in the simulated trials. Inspired by analyses of trials of insecticide-treated nets against malaria when applied to the geography of the SolarMal trial, these measures were found to be robust to different variants of SWCRT design. Analyses of the likely extent of contamination effects supported the choice of cluster size for the trial.; The SWCRT is an appropriate design for trials that assess the feasibility of local elimination of a pathogen. The effects of incomplete coverage can be estimated by analyzing the extent of contamination between arms in such trials, and the estimates also support inferences about causality. The SolarMal example illustrates how generic transmission models incorporating spatial smoothing can be used to simulate such trials for a power calculation and optimization of cluster size and randomization strategies. The approach is applicable to a range of infectious diseases transmitted via environmental reservoirs or via arthropod vectors

Deep splicing plasticity of the human adenovirus type 5 transcriptome drives virus evolution

Viral genomes have high gene densities and complex transcription strategies rendering transcriptome analysis through short-read RNA-seq approaches problematic. Adenovirus transcription and splicing is especially complex. We used long-read direct RNA sequencing to study adenovirus transcription and splicing during infection. This revealed a previously unappreciated complexity of alternative splicing and potential for secondary initiating codon usage. Moreover, we find that most viral transcripts tend to shorten polyadenylation lengths as infection progresses. Development of an open reading frame centric bioinformatics analysis pipeline provided a deeper quantitative and qualitative understanding of adenovirus’s genetic potential. Across the viral genome adenovirus makes multiple distinctly spliced transcripts that code for the same protein. Over 11,000 different splicing patterns were recorded across the viral genome, most occurring at low levels. This low-level use of alternative splicing patterns potentially enables the virus to maximise its coding potential over evolutionary timescales

Are null segregants new combinations of heritable material and should they be regulated?

Through genome editing and other techniques of gene technology, it is possible to create a class of organism called null segregants. These genetically modified organisms (GMOs) are products of gene technology but are argued to have no lingering vestige of the technology after the segregation of chromosomes or deletion of insertions. From that viewpoint regulations are redundant because any unique potential for the use of gene technology to cause harm has also been removed. We tackle this question of international interest by reviewing the early history of the purpose of gene technology regulation. The active ingredients of techniques used for guided mutagenesis, e.g., site-directed nucleases, such as CRISPR/Cas, are promoted for having a lower potential per reaction to create a hazard. However, others see this as a desirable industrial property of the reagents that will lead to genome editing being used more and nullifying the promised hazard mitigation. The contest between views revolves around whether regulations could alter the risks in the responsible use of gene technology. We conclude that gene technology, even when used to make null segregants, has characteristics that make regulation a reasonable option for mitigating potential harm. Those characteristics are that it allows people to create more harm faster, even if it creates benefits as well; the potential for harm increases with increased use of the technique, but safety does not; and regulations can control harm scaling.publishedVersio

Evaluating putative repellent 'push' and attractive 'pull' components for manipulating the odour orientation of host-seeking malaria vectors in the peri-domestic space

BACKGROUND: Novel malaria vector control approaches aim to combine tools for maximum protection. This study aimed to evaluate novel and re-evaluate existing putative repellent 'push' and attractive 'pull' components for manipulating the odour orientation of malaria vectors in the peri-domestic space. METHODS: Anopheles arabiensis outdoor human landing catches and trap comparisons were implemented in large semi-field systems to (i) test the efficacy of Citriodiol((R)) or transfluthrin-treated fabric strips positioned in house eave gaps as push components for preventing bites; (ii) understand the efficacy of MB5-baited Suna-traps in attracting vectors in the presence of a human being; (iii) assess 2-butanone as a CO2 replacement for trapping; (iv) determine the protection provided by a full push-pull set up. The air concentrations of the chemical constituents of the push-pull set-up were quantified. RESULTS: Microencapsulated Citriodiol((R)) eave strips did not provide outdoor protection against host-seeking An. arabiensis. Transfluthrin-treated strips reduced the odds of a mosquito landing on the human volunteer (OR 0.17; 95% CI 0.12-0.23). This impact was lower (OR 0.59; 95% CI 0.52-0.66) during the push-pull experiment, which was associated with low nighttime temperatures likely affecting the transfluthrin vaporisation. The MB5-baited Suna trap supplemented with CO2 attracted only a third of the released mosquitoes in the absence of a human being; however, with a human volunteer in the same system, the trap caught < 1% of all released mosquitoes. The volunteer consistently attracted over two-thirds of all mosquitoes released. This was the case in the absence ('pull' only) and in the presence of a spatial repellent ('push-pull'), indicating that in its current configuration the tested 'pull' does not provide a valuable addition to a spatial repellent. The chemical 2-butanone was ineffective in replacing CO2. Transfluthrin was detectable in the air space but with a strong linear reduction in concentrations over 5 m from release. The MB5 constituent chemicals were only irregularly detected, potentially suggesting insufficient release and concentration in the air for attraction. CONCLUSION: This step-by-step evaluation of the selected 'push' and 'pull' components led to a better understanding of their ability to affect host-seeking behaviours of the malaria vector An. arabiensis in the peri-domestic space and helps to gauge the impact such tools would have when used in the field for monitoring or control

Upstream-binding factor is sequestered into herpes simplex virus type 1 replication compartments

Previous reports have shown that adenovirus recruits nucleolar protein upstream-binding factor (UBF) into adenovirus DNA replication centres. Here, we report that despite having a different mode of viral DNA replication, herpes simplex virus type 1 (HSV-1) also recruits UBF into viral DNA replication centres. Moreover, as with adenovirus, enhanced green fluorescent protein-tagged fusion proteins of UBF inhibit viral DNA replication. We propose that UBF is recruited to the replication compartments to aid replication of HSV-1 DNA. In addition, this is a further example of the role of nucleolar components in viral life cycle

Heat Shock Protein 70 family members interact with Crimean-Congo hemorrhagic fever virus and Hazara virus nucleocapsid proteins and perform a functional role in the nairovirus replication cycle

The Nairovirus genus of the Bunyaviridae family contains serious human and animal pathogens classified within multiple serogroups and species. Of these serogroups, the Crimean-Congo hemorrhagic fever virus (CCHFV) serogroup comprises sole members CCHFV and Hazara virus (HAZV). CCHFV is an emerging zoonotic virus that causes often-fatal hemorrhagic fever in infected humans for which preventative or therapeutic strategies are not available. In contrast HAZV is non-pathogenic to humans, and thus represents an excellent model to study aspects of CCHFV biology under more accessible biological containment. The three RNA segments that form the nairovirus genome are encapsidated by the viral nucleocapsid protein (N) to form ribonucleoprotein (RNP) complexes that are substrates for RNA synthesis and packaging into virus particles. We used quantitative proteomics to identify cellular interaction partners of CCHFV N, and identified robust interactions with cellular chaperones. These interactions were validated using immunological methods, and the specific interaction between native CCHFV N and cellular chaperones of the HSP70 family was confirmed during live CCHFV infection. Using infectious HAZV we showed for the first time that the nairovirus N-HSP70 association was maintained within both infected cells and virus particles, where N is assembled as RNPs. Reduction of active HSP70 levels in cells using small molecule inhibitors significantly reduced HAZV titres, and a model for chaperone function in the context of high genetic variability is proposed. These results suggest chaperones of the HSP70 family are required for nairovirus replication and thus represent a genetically stable cellular therapeutic target for preventing nairovirus-mediated disease

A randomized, double-blind placebo-control study assessing the protective efficacy of an odour-based 'push-pull' malaria vector control strategy in reducing human-vector contact

Novel malaria vector control strategies targeting the odour-orientation of mosquitoes during host-seeking, such as 'attract-and-kill' or 'push-and-pull', have been suggested as complementary tools to indoor residual spraying and long-lasting insecticidal nets. These would be particularly beneficial if they can target vectors in the peri-domestic space where people are unprotected by traditional interventions. A randomized double-blind placebo-control study was implemented in western Kenya to evaluate: a 'push' intervention (spatial repellent) using transfluthrin-treated fabric strips positioned at open eave gaps of houses; a 'pull' intervention placing an odour-baited mosquito trap at a 5 m distance from a house; the combined 'push-pull' package; and the control where houses contained all elements but without active ingredients. Treatments were rotated through 12 houses in a randomized-block design. Outdoor biting was estimated using human landing catches, and indoor mosquito densities using light-traps. None of the interventions provided any protection from outdoor biting malaria vectors. The 'push' reduced indoor vector densities dominated by Anopheles funestus by around two thirds. The 'pull' device did not add any benefit. In the light of the high Anopheles arabiensis biting densities outdoors in the study location, the search for efficient outdoor protection and effective pull components needs to continue