Molecular evidence for a kdr-like pyrethroid resistance mechanism in the malaria vector mosquito Anopheles stephensi

The mosquito Anopheles stephensi Liston (Diptera: Culicidae) is the urban vector of malaria in several countries of the Middle East and Indian subcontinent. Extensive use of residual insecticide spraying for malaria vector control has selected An. stephensi resistance to DDT, dieldrin, malathion and other organophosphates throughout much of its range and to pyrethroids in the Middle East. Metabolic resistance mechanisms and insensitivity to pyrethroids, so-called knockdown resistance (kdr), have previously been reported in An. stephensi. Here we provide molecular data supporting the hypothesis that a kdr-like pyrethroid-resistance mechanism is present in An. stephensi. We found that larvae of a pyrethroid-selected strain from Dubai (DUB-R) were 182-fold resistant to permethin, compared with a standard susceptible strain of An. stephensi. Activities of some enzymes likely to confer pyrethroid-resistance (i.e. esterases, monooxygenases and glutathione S-transferases) were significantly higher in the permethrin-resistant than in the susceptible strain, but the use of synergists--piperonyl butoxide (PBO) to inhibit monooxygenases and/or tribufos (DEF) to inhibit esterases--did not fully prevent resistance in larvae (permethrin LC50 reduced by only 51-68%), indicating the involvement of another mechanism. From both strains of An. stephensi, we obtained a 237-bp fragment of genomic DNA encoding segment 6 of domain II of the para type voltage-gated sodium channel, i.e. the putative kdr locus. By sequencing this 237 bp fragment, we identified one point mutation difference involving a single A-T base change encoding a leucine to phenylalanine amino acid substitution in the pyrethroid-resistant strain. This mutation appears to be homologous with those detected in An. gambiae and other insects with kdr-like resistance. A diagnostic polymerase chain reaction assay using nested primers was therefore designed to detect this mechanism in An. stephensi.     

Prolactin-induced expression of intercellular adhesion molecule-1 and the accumulation of monocytes/macrophages during regression of the rat corpus luteum

Intercellular adhesion molecule-1 (ICAM-1) is thought to facilitate the recruitment and migration of monocytes/macrophages to sites of inflammation. Here we investigated whether the luteolytic effect of prolactin in the hypophysectomized rat is associated with the expression of ICAM-1. In addition, we examined the effect of exogenous testosterone (or its potential conversion to estradiol endogenously) on the corpus luteum to address recent speculation that ovarian steroids might augment luteal regression. Immature, 30-day-old rats were ovulated with eCG and hCG and then hypophysectomized; this resulted in a single cohort of persistent corpora lutea. The rats were assigned randomly into four treatment groups: vehicle treatment without or with testosterone (VEH-T4, VEH+T4) and prolactin treatment without or with testosterone (PRL-T4, PRL+T4). Corpora lutea of control rats exhibited minimal ICAM-1 staining and contained relatively few monocytes/macrophages. In contrast, corpora lutea of prolactin-treated rats exhibited prominent ICAM-1 staining and contained numerous monocytes/macrophages. Testosterone did not overtly affect ICAM-1 staining, numbers of monocytes/macrophages, or concentrations of plasma progestins (progesterone and 20alpha-dihydroprogesterone) in either VEH or prolactin treatment groups; notwithstanding, luteal weights increased significantly in response to testosterone in VEH+T4 rats compared to VEH-T4 rats and prolactin-treated rats. We conclude that ICAM-1 expression and monocyte/macrophage accumulation are associated with prolactin-induced luteal regression in the rat and that these aspects are not influenced by testosterone.     

Human DNA polymerase kappa encircles DNA: implications for mismatch extension and lesion bypass

Human DNA polymerase kappa (Pol kappa) is a proficient extender of mispaired primer termini on undamaged DNAs and is implicated in the extension step of lesion bypass. We present here the structure of Pol kappa catalytic core in ternary complex with DNA and an incoming nucleotide. The structure reveals encirclement of the DNA by a unique "N-clasp" at the N terminus of Pol kappa, which augments the conventional right-handed grip on the DNA by the palm, fingers, and thumb domains and the PAD and provides additional thermodynamic stability. The structure also reveals an active-site cleft that is constrained by the close apposition of the N-clasp and the fingers domain, and therefore can accommodate only a single Watson-Crick base pair. Together, DNA encirclement and other structural features help explain Pol kappa's ability to extend mismatches and to promote replication through various minor groove DNA lesions, by extending from the nucleotide incorporated opposite the lesion by another polymerase.     

Effect of older age on treatment decisions and outcomes among patients with traumatic spinal cord injury

Background:

Older people are at increased risk of traumatic spinal cord injury from falls. We evaluated the impact of older age (≥ 70 yr) on treatment decisions and outcomes.

Methods:

We identified patients with traumatic spinal cord injury for whom consent and detailed data were available from among patients recruited (2004–2013) at any of the 31 acute care and rehabilitation hospitals participating in the Rick Hansen Spinal Cord Injury Registry. Patients were assessed by age group (< 70 v. ≥ 70 yr). The primary outcome was the rate of acute surgical treatment. We used bivariate and multivariate regression models to assess patient and injury-related factors associated with receiving surgical treatment and with the timing of surgery after arrival to a participating centre.

Results:

Of the 1440 patients included in our study cohort, 167 (11.6%) were 70 years or older at the time of injury. Older patients were more likely than younger patients to be injured by falling (83.1% v. 37.4%; p < 0.001), to have a cervical injury (78.0% v. 61.6%; p = 0.001), to have less severe injuries on admission (American Spinal Injury Association Impairment Scale grade C or D: 70.5% v. 46.9%; p < 0.001), to have a longer stay in an acute care hospital (median 35 v. 28 d; p < 0.005) and to have a higher in-hospital mortality (4.2% v. 0.6%; p < 0.001). Multivariate analysis did not show that age of 70 years or more at injury was associated with a decreased likelihood of surgical treatment (adjusted odds ratio [OR] 0.48, 95% confidence interval [CI] 0.22–1.07). An unplanned sensitivity analysis with different age thresholds showed that a threshold of 65 years was associated with a decreased chance of surgical treatment (OR 0.39, 95% CI 0.19–0.80). Older patients who underwent surgical treatment had a significantly longer wait time from admission to surgery than younger patients (37 v. 19 h; p < 0.001).

Interpretation:

We found chronological age to be a factor influencing treatment decisions but not at the 70-year age threshold that we had hypothesized. Older patients waited longer for surgery and had a substantially higher in-hospital mortality despite having less severe injuries than younger patients. Further research into the link between treatment delays and outcomes among older patients could inform surgical guideline development.Globally there has been an epidemiologic shift in the age of patients who sustain a traumatic spinal cord injury.^1–3 Although most people who have traumatic spinal cord injuries are 16–30 years old, there has been a progressive increase in the number who are over 70. The average age at injury has increased from 29 to 40 years.⁴ By 2032, patients over 70 are predicted to account for most patients with new traumatic spinal cord injuries.⁵ This change is attributed in part to aging baby boomers. It is unknown whether the management and outcomes of these older patients differ compared with younger patients.Older patients typically have more comorbid conditions, including cardiovascular disease, respiratory disorders, cerebrovascular disease and dementia, which are thought to increase their risk of perioperative adverse events.⁶ The use of anticoagulants for cardiac and cerebrovascular indications can delay timely surgical interventions. Older patients are also at increased risk of postoperative and medication-related adverse events, such as delirium.⁷ As a direct consequence of this perceived risk of perioperative adverse events and ambiguity about the optimal treatment for spinal cord injury in older patients, surgeons may deliberate for some time before making a clear therapeutic decision, they may choose nonoperative treatment,⁸ or they may delay the surgical treatment in an effort to optimize the patient’s condition medically.Given the increasing incidence of traumatic spinal cord injury in older adults, and the potential for differences in treatment among older and younger patients, we evaluated the impact of age on treatment decisions and outcomes among patients with traumatic spinal cord injury. We hypothesized that surgical management would differ at an age threshold of 70 years.     

Integrated dataset of screening hits against multiple neglected disease pathogens

New chemical entities are desperately needed that overcome the limitations of existing drugs for neglected diseases. Screening a diverse library of 10,000 drug-like compounds against 7 neglected disease pathogens resulted in an integrated dataset of 744 hits. We discuss the prioritization of these hits for each pathogen and the strong correlation observed between compounds active against more than two pathogens and mammalian cell toxicity. Our work suggests that the efficiency of early drug discovery for neglected diseases can be enhanced through a collaborative, multi-pathogen approach.     

Population differentiation and Wolbachia phylogeny in mosquitoes of the Aedes scutellaris group

Mosquito species of the Aedes (Stegomyia) scutellaris (Walker) group (Diptera: Culicidae) are distributed across many islands of the South Pacific and include major regional vectors of filariasis, such as Aedes polynesiensis (Marks). Analysis of populations of Ae. polynesiensis at the extremes of its range, from Fiji and from Moorea, French Polynesia, using the rDNA ITS2 (internal transcribed spacer 2) region and six microsatellite markers showed considerable genetic differentiation between them (F(ST) = 0.298-0.357). Phylogenetic analysis of the Wolbachia endosymbionts in three members of the complex revealed that based on the wsp gene they are all very similar and belong to the Mel subgroup of the A clade, closely related to the Wolbachia strain present in the gall wasp Callyrhytis glandium (Giraud) (Hymenoptera: Cynipidae). By contrast they are only distantly related to the A-clade Wolbachia in Aedes albopictus (Skuse), a species closely allied to the Ae. scutellaris group. There was very low differentiation between the Wolbachia in the Moorea and Fiji populations of Ae. polynesiensis.     

Protective efficacy of a recombinant plague vaccine when co-administered with another sub-unit or live attenuated vaccine

Vaccines against bioterrorism agents offer the prospect of providing high levels of protection against airborne pathogens. However, the diversity of the bioterrorism threat means that it may be necessary to use several vaccines simultaneously. In this study we have investigated whether there are changes to the protective immune response to a recombinant sub-unit plague vaccine when it is co-administered with other sub-unit or live attenuated vaccines. Our results indicate that the co-administration of these vaccines did not influence the protection afforded by the plague vaccine. However, the co-administration of the plague sub-unit vaccine with a live vaccine resulted in markedly increased levels of IgG2a subclass antibodies, and markedly reduced levels of IgG1 subclass antibodies, to the plague sub-unit vaccine. This finding might have implications when considering the co-administration of other vaccine combinations.     

Malaria and urbanization in sub-Saharan Africa

There are already 40 cities in Africa with over 1 million inhabitants and the United Nations Environmental Programme estimates that by 2025 over 800 million people will live in urban areas. Recognizing that malaria control can improve the health of the vulnerable and remove a major obstacle to their economic development, the Malaria Knowledge Programme of the Liverpool School of Tropical Medicine and the Systemwide Initiative on Malaria and Agriculture convened a multi-sectoral technical consultation on urban malaria in Pretoria, South Africa from 2nd to 4th December, 2004. The aim of the meeting was to identify strategies for the assessment and control of urban malaria. This commentary reflects the discussions held during the meeting and aims to inform researchers and policy makers of the potential for containing and reversing the emerging problem of urban malaria.