A molecular epidemiological study of var gene diversity to characterize the reservoir of Plasmodium falciparum in humans in Africa

Background

The reservoir of Plasmodium infection in humans has traditionally been defined by blood slide positivity. This study was designed to characterize the local reservoir of infection in relation to the diverse var genes that encode the major surface antigen of Plasmodium falciparum blood stages and underlie the parasite''s ability to establish chronic infection and transmit from human to mosquito.

Methodology/Principal Findings

We investigated the molecular epidemiology of the var multigene family at local sites in Gabon, Senegal and Kenya which differ in parasite prevalence and transmission intensity. 1839 distinct var gene types were defined by sequencing DBLα domains in the three sites. Only 76 (4.1%) var types were found in more than one population indicating spatial heterogeneity in var types across the African continent. The majority of var types appeared only once in the population sample. Non-parametric statistical estimators predict in each population at minimum five to seven thousand distinct var types. Similar diversity of var types was seen in sites with different parasite prevalences.

Conclusions/Significance

Var population genomics provides new insights into the epidemiology of P. falciparum in Africa where malaria has never been conquered. In particular, we have described the extensive reservoir of infection in local African sites and discovered a unique var population structure that can facilitate superinfection through minimal overlap in var repertoires among parasite genomes. Our findings show that var typing as a molecular surveillance system defines the extent of genetic complexity in the reservoir of infection to complement measures of malaria prevalence. The observed small scale spatial diversity of var genes suggests that var genetics could greatly inform current malaria mapping approaches and predict complex malaria population dynamics due to the import of var types to areas where no widespread pre-existing immunity in the population exists.     

Assessing the effectiveness of a community intervention for monkeypox prevention in the Congo basin

Background

In areas where health resources are limited, community participation in the recognition and reporting of disease hazards is critical for the identification of outbreaks. This is particularly true for zoonotic diseases such as monkeypox that principally affect people living in remote areas with few health services. Here we report the findings of an evaluation measuring the effectiveness of a film-based community outreach program designed to improve the understanding of monkeypox symptoms, transmission and prevention, by residents of the Republic of the Congo (ROC) who are at risk for disease acquisition.

Methodology/Principal Findings

During 90 days, monkeypox outreach was conducted for ∼23,860 people in northern ROC. Two hundred seventy-one attendees (selected via a structured sample) were interviewed before and after participating in a small-group outreach session. The proportion of interviewees demonstrating monkeypox-specific knowledge before and after was compared. Significant gains were measured in areas of disease recognition, transmission, and mitigation of risk. The ability to recognize at least one disease symptom and a willingness to take a family member with monkeypox to the hospital increased from 49 and 45% to 95 and 87%, respectively (p<0.001, both). Willingness to deter behaviors associated with zoonotic risk, such as eating the carcass of a primate found dead in the forest, remained fundamentally unchanged however, suggesting additional messaging may be needed.

Conclusions/Significance

These results suggest that our current program of film-based educational activities is effective in improving disease-specific knowledge and may encourage individuals to seek out the advice of health workers when monkeypox is suspected.     

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.     

Comparison of Water,Oils and Emulsifiable Adjuvant Oils as Formulating Agents for <Emphasis Type="Italic">Metarhizium Anisopliae</Emphasis> for Use in Control of <Emphasis Type="Italic">Boophilus Microplus</Emphasis>

Studies were conducted to identify oil-based formulating agents (paraffinic oil, palm oil and emulsifiable adjuvant oils (EAOs)) for Metarhizium anisopliae that were superior to water with simple surfactants using a germination test and a bioassay against Boophilus microplus. Germination of conidia in all formulations, except 10% coconut EAO, produced more than 68% germination at 24 h and nearly 100% at 48 h. Coconut oil (average survival time (AST)=4.6±0.28 days) and 10% liquid paraffin EAO (AST=4.4±0.15 days) enhanced the pathogenicity of M. anisopliae to B. microplus relative to water (AST=8.4±0.42 days). M. anisopliae in 10% liquid paraffin EAO was the most effective formulation having a moderately high germination after 24 h and a low AST as well as a high AST in the control. In the second experiment, germination of conidia in 2% liquid paraffin EAO and 2% Cropspray was higher than in 2% Codacide oil at 24 h, however, all treatments reached 100% germination after 48 h. The ASTs of the EAO based M. anisopliae formulations (Average AST=6.4±0.54 days) were similar but lower that the ASTs of the controls (Average AST=9.6±0.28 days).     

Molecular recognition of DNA base pairs by the formamido/pyrrole and formamido/imidazole pairings in stacked polyamides

Polyamides containing an N-terminal formamido (f) group bind to the minor groove of DNA as staggered, antiparallel dimers in a sequence-specific manner. The formamido group increases the affinity and binding site size, and it promotes the molecules to stack in a staggered fashion thereby pairing itself with either a pyrrole (Py) or an imidazole (Im). There has not been a systematic study on the DNA recognition properties of the f/Py and f/Im terminal pairings. These pairings were analyzed here in the context of f-ImPyPy, f-ImPyIm, f-PyPyPy and f-PyPyIm, which contain the central pairing modes, –ImPy– and –PyPy–. The specificity of these triamides towards symmetrical recognition sites allowed for the f/Py and f/Im terminal pairings to be directly compared by SPR, CD and ΔT_M experiments. The f/Py pairing, when placed next to the –ImPy– or –PyPy– central pairings, prefers A/T and T/A base pairs to G/C base pairs, suggesting that f/Py has similar DNA recognition specificity to Py/Py. With –ImPy– central pairings, f/Im prefers C/G base pairs (>10 times) to the other Watson–Crick base pairs; therefore, f/Im behaves like the Py/Im pair. However, the f/Im pairing is not selective for the C/G base pair when placed next to the –PyPy– central pairings.     

Inducing late phase of infarct protection in skeletal muscle by remote preconditioning: efficacy and mechanism

We have previously demonstrated that remote ischemic preconditioning (IPC) by instigation of three cycles of 10-min occlusion/reperfusion in a hindlimb of the pig elicits an early phase of infarct protection in local and distant skeletal muscles subjected to 4 h of ischemia immediately after remote IPC. The aim of this project was to test our hypothesis that hindlimb remote IPC also induces a late phase of infarct protection in skeletal muscle and that K(ATP) channels play a pivotal role in the trigger and mediator mechanisms. We observed that pig bilateral latissimus dorsi (LD) muscle flaps sustained 46 +/- 2% infarction when subjected to 4 h of ischemia/48 h of reperfusion. The late phase of infarct protection appeared at 24 h and lasted up to 72 h after hindlimb remote IPC. The LD muscle infarction was reduced to 28 +/- 3, 26 +/- 1, 23 +/- 2, 24 +/- 2 and 24 +/- 4% at 24, 28, 36, 48 and 72 h after remote IPC, respectively (P < 0.05; n = 8). In subsequent studies, hindlimb remote IPC or intravenous injection of the sarcolemmal K(ATP) (sK(ATP)) channel opener P-1075 (2 microg/kg) at 24 h before 4 h of sustained ischemia (i.e., late preconditioning) reduced muscle infarction from 43 +/- 4% (ischemic control) to 24 +/- 2 and 19 +/- 3%, respectively (P < 0.05, n = 8). Intravenous injection of the sK(ATP) channel inhibitor HMR 1098 (6 mg/kg) or the nonspecific K(ATP) channel inhibitor glibenclamide (Glib; 1 mg/kg) at 10 min before remote IPC completely blocked the infarct- protective effect of remote IPC in LD muscle flaps subjected to 4 h of sustained ischemia at 24 h after remote IPC. Intravenous bolus injection of the mitochondrial K(ATP) (mK(ATP)) channel inhibitor 5-hydroxydecanoate (5-HD; 5 mg/kg) immediately before remote IPC and 30-min intravenous infusion of 5-HD (5 mg/kg) during remote IPC did not affect the infarct-protective effect of remote IPC in LD muscle flaps. However, intravenous Glib or 5-HD, but not HMR 1098, given 24 h after remote IPC completely blocked the late infarct-protective effect of remote IPC in LD muscle flaps. None of these drug treatments affected the infarct size of control LD muscle flaps. The late phase of infarct protection was associated with a higher (P < 0.05) muscle content of ATP at the end of 4 h of ischemia and 1.5 h of reperfusion and a lower (P < 0.05) neutrophilic activity at the end of 1.5 h of reperfusion compared with the time-matched control. In conclusion, these findings support our hypothesis that hindlimb remote IPC induces an uninterrupted long (48 h) late phase of infarct protection, and sK(ATP) and mK(ATP) channels play a central role in the trigger and mediator mechanism, respectively.     

Enterostatin decreases postprandial pancreatic UCP2 mRNA levels and increases plasma insulin and amylin

This study investigated the chronic effect of enterostatin on body weight and some of the associated changes in postprandial metabolism. Rats were adapted to 6 h of food access/day and a choice of low-fat and high-fat (HF) food and then given enterostatin or vehicle by an intraperitoneally implanted minipump delivering 160 nmol enterostatin/h continuously over a 5-day infusion period. Enterostatin resulted in a slight but significant reduction of HF intake and body weight. After the last 6-h food access period, enterostatin-treated animals had lower plasma triglyceride and free fatty acid but higher plasma glucose and lactate levels than control animals. Enterostatin infusion resulted in increased uncoupling protein-2 (UCP2) expression in various tissues, including epididymal fat and liver. UCP2 was reduced in the pancreas of enterostatin-treated animals, and this was associated with increased plasma levels of insulin and amylin. Whether these two hormones are involved in the observed decreased food intake due to enterostatin remains to be determined. As lipid metabolism appeared to be altered by enterostatin, we measured peroxisome proliferator-activated receptor (PPAR) expression in tissues and observed that PPARalpha, -beta, -gamma1, and -gamma2 expression were modified by enterostatin in epididymal fat, pancreas, and liver. This further links altered lipid metabolism with body weight loss. Our data suggest that alterations in UCP2 and PPARgamma2 play a role in the control of insulin and amylin release from the pancreas. This implies that enterostatin changes lipid and carbohydrate metabolic pathways in addition to its effects on food intake and energy expenditure.     

Under pressure: stromal fibroblasts change their ways

In this issue of Cell, Hill et al. (2005) demonstrate in a mouse model of prostate cancer that the tumor cells can initiate and promote expansion of stromal fibroblasts that lack the tumor-suppressor protein p53 through a paracrine mechanism. This results in selection of highly proliferative fibroblasts associated with the carcinoma that further promote tumor progression.     

Matrix metalloproteinase-2 (MMP-2) expression and regulation by tumor necrosis factor alpha (TNFalpha) in the bovine corpus luteum

Angiogenesis and tissue remodeling events in the corpus luteum (CL) are mediated by matrix metalloproteinases (MMPs). We have recently reported the cloning of bovine membrane-type 1 metalloproteinase (MT1-MMP) and have shown that active MT1-MMP is correlated to MMP-2 activity in the CL during the estrous cycle. Given the important role that MMP-2 plays in neovascularization, we became interested in understanding the role of this enzyme in the CL, a system in which angiogenesis is exquisitely regulated in the course of its lifespan. The aims of the present study were to clone bovine MMP-2 cDNA, to investigate its temporal and spatial expression in three stages of CL during the estrous cycle and to study its regulation by TNFalpha, a key cytokine regulator of CL physiology. Bovine MMP-2 cDNA was isolated from a UNI-ZAP II bovine capillary endothelial cell cDNA library and sequenced. This gene encoded a protein of 662 amino acids. Luteal tissues were collected from non-lactating dairy cows on days 4, 10, and 16 of the estrous cycle. Northern and Western blotting revealed that the levels of MMP-2 mRNA (3.1 kb) and immunoreactive pro-MMP-2 protein (68 kDa) did not differ (P > 0.05) in any age of CL examined. In addition to large luteal cells, MMP2 was localized to endothelial cells in all ages of CL by immunohistochemistry. Studies using in vitro luteal cell cultures showed that MMP-2 mRNA, protein expression and activity was upregulated by TNFalpha in a dose- and time-dependent manner. The present study suggests that MMP-2 is predominantly produced by large luteal cells and endothelial cells, and that it plays an essential role in luteal remodeling and angiogenesis. These data also suggest that cytokines such as TNFalpha may modulate these processes by regulating MMP-2 expression.