Discrepant Prevalence and Incidence of Leishmania Infection between Two Neighboring Villages in Central Mali Based on Leishmanin Skin Test Surveys

Apart from a single report, the last publication of cutaneous leishmaniasis (CL) in Mali dates back more than 20 years. The absence of information on the current status of CL in Mali led us to conduct a cohort study in Kemena and Sougoula, two villages in Central Mali from which cases of CL have been recently diagnosed by Mali''s reference dermatology center in Bamako. In May 2006, we determined the baseline prevalence of Leishmania infection in the two villages using the leishmanin skin test (LST). LST-negative individuals were then re-tested over two consecutive years to estimate the annual incidence of Leishmania infection. The prevalence of Leishmania infection was significantly higher in Kemena than in Sougoula (45.4% vs. 19.9%; OR: 3.36, CI: 2.66–4.18). The annual incidence of Leishmania infection was also significantly higher in Kemena (18.5% and 17% for 2007 and 2008, respectively) than in Sougoula (5.7% for both years). These data demonstrate that the risk of Leishmania infection was stable in both villages and confirm the initial observation of a significantly higher risk of infection in Kemena (OR: 3.78; CI: 2.45–6.18 in 2007; and OR: 3.36; CI: 1.95–5.8 in 2008; P<0.005). The absence of spatial clustering of LST-positive individuals in both villages indicated that transmission may be occurring anywhere within the villages. Although Kemena and Sougoula are only 5 km apart and share epidemiologic characteristics such as stable transmission and random distribution of LST-positive individuals, they differ markedly in the prevalence and annual incidence of Leishmania infection. Here we establish ongoing transmission of Leishmania in Kemena and Sougoula, Central Mali, and are currently investigating the underlying factors that may be responsible for the discrepant infection rates we observed between them.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00344084","term_id":"NCT00344084"}}NCT00344084     

Leishmania donovani lipophosphoglycan blocks NADPH oxidase assembly at the phagosome membrane

Phagocytosis of Leishmania donovani promastigotes is characterized by an inhibition of phagolysosome biogenesis mediated by the surface glycolipid lipophosphoglycan (LPG). However, the consequences of this inhibition on macrophage function remain to be determined. In this study, we investigated the impact of LPG-mediated phagosome remodelling on the assembly and function of the NADPH oxidase complex. Phagocytosis of both wild-type and LPG-defective L. donovani promastigotes triggered the release of similar levels of superoxide. However, wild-type promastigotes, but not LPG-defective mutants, inhibited generation of superoxide at the phagosome. Confocal microscopy imaging revealed that the membrane component gp91(phox) and the Rho-family GTPase Rac1 were present on phagosomes containing either wild-type or LPG-defective promastigotes. In contrast, the NADPH oxidase cytosolic components p47(phox) and p67(phox) were excluded from phagosomes in a LPG-dependent fashion. This inhibition is not the consequence of a general defect in the initiation of the NADPH oxidase activation process because both wild-type and LPG-defective promastigotes induced p47(phox) phosphorylation and the formation of complexes containing p47(phox) and p67(phox). Thus, by remodelling their intracellular habitat, L. donovani promastigotes prevent the assembly of a functional phagosomal NADPH oxidase complex, thereby evading an important host innate defence mechanism.     

Structures and structure-activity relationships of three mitogenic and complement fixing pectic arabinogalactans from the malian antiulcer plants Cochlospermum tinctorium A. Rich and Vernonia kotschyana Sch. Bip. ex Walp

Structures of three pectic arabinogalactans, one from Vernonia kotschyana (Vk2a) and two from Cochlospermum tinctorium (Ct50A1 and Ct50A2), and their complement fixation and induction of B cell proliferation in vitro were compared. The polysaccharide Vk2a expressed potent biological activity in both assays compared with Ct50A1 and Ct50A2. Vk2a possessed a very high molecular weight (1150 +/- 20 kDa) compared with Ct50A1 and Ct50A2 which both showed a polydisperse nature with the highest molecular weight polymers in each fraction estimated at approximately 105 kDa (Ct1a) and 640 +/- 100 kDa (Ct2a), respectively. The HMW polymers showed complement fixation in the same range as the native fractions. The arabinogalactan II content was low in Vk2a (2%) compared with that in Ct50A1 (23%) and Ct50A2 (12%). The high molecular weight polymers were subjected to digestion with a beta-d-(1, 3)-galactanase-rich fraction from Driselase, oligomers were isolated by HPAEC, and their finer structures were determined by MALDI- and ES-qoToF-MS, linkage, and monosaccharide composition analyses. Vk2a consists of both a galacturonan core and a rhamnogalacturonan core rich in neutral side chains. The backbones of both Ct-polysaccharides consist mainly of RG-I regions with numerous neutral side chains dominated by galactosyl residues, whereas the homogalacturonan regions seem to be small. Differences in the chain lengths of the 6-linked galacto-oligosaccharides attached to the 3-linked galactan core could not be related to the differences in the potencies of the biological activities observed.     

A capillary gas chromatography/mass spectrometric method for the quantification of hydroxysteroids in human plasma

A specific and sensitive methodology for the quantitative determination of hydroxysteroids dehydroepiandrosterone and pregnenolone and their main metabolites in human plasma is described. Hydroxysteroids were extracted using methanol and steroids were further separated by reverse-phase high-performance liquid chromatography, allowing for minimization of the possible chromatographic interferences. Eluted fractions were collected, pooled, and analyzed by gas chromatography-mass spectrometry as trimethylsilyl ether derivatives. The quantification was performed with single-ion monitoring of the highly abundant m/z 129 or m/z 358 fragments. The combination of the chromatographic characteristics to the specific fragments ensured the selectivity and specificity of the method. Under these conditions the method was linear (typical R2 is superior to 0.98 for all hydroxysteroids studied) over the concentration range of 2 x 10(-9) to 10(-6)M with good precision and accuracy.     

Structure-immunomodulating activity relationships of a pectic arabinogalactan from Vernonia kotschyana Sch. Bip. ex Walp

Structure and immunological characteristics of the pectic arabinogalactan Vk2a (previously reported as Vk100A2a) from the roots of Vernonia kotschyana Sch. Bip. ex Walp. were investigated after enzymatic digestion of the galacturonan moiety and the side chains of the rhamnogalacturonan structure of Vk2a. endo-alpha-D-(1-->4)-Polygalacturonase digestion released the high molecular weight 'hairy region' (Vk2a-HR) and oligogalacturonides. Vk2a-HR consisted of GalA (4-linked) and Rha (2- or 2,4-linked) in a 1:1 ratio, with 60% of Rha branched at C-4. The Rha located in the rhamnogalacturonan core was branched randomly by Gal units. Vk2a-HR was rich in neutral sugars such as Araf 5- (12.2%) and 3,5-substituted (12.8%) and terminally- (14.1%) linked and Gal 4- (13.0%), 3- (0.9%), 6- (2.2%) and 3,6- (1.1%) substituted. Arabinans with chain lengths up to 11 units were identified. Araf residues were attached to C-3 of alpha-L-(1-->5)-Araf chains and to C-4 of Gal residues. Single Gal units and chains of beta-D-(1-->6)-linked galacto di- to penta-saccharides were attached to a beta-D-(1-->3)-galactan core. All the enzyme resistant fractions expressed potent complement fixation and induction of B-cell mitogenic activity, and the present study indicates that there may be several and possibly structurally different active sites involved in the bioactivity of Vk2a. The bioactive sites may be located both in the more peripheral parts of the molecule but also in the inner core of the 'hairy region' or in larger enzyme-resistant chains.     

Leader sequences downstream of the primer binding site are important for efficient replication of simian immunodeficiency virus

Simian immunodeficiency virus (SIV) infection of macaques is remarkably similar to that of human immunodeficiency virus type 1 (HIV-1) in humans, and the SIV-macaque system is a good model for AIDS research. We have constructed an SIV proviral DNA clone that is deleted of 97 nucleotides (nt), i.e., construct SD, at positions (+322 to +418) immediately downstream of the primer binding site (PBS) of SIVmac239. When this construct was transfected into COS-7 cells, the resultant viral progeny were severely impaired with regard to their ability to replicate in C8166 cells. Further deletion analysis showed that a virus termed SD1, containing a deletion of 23 nt (+322 to +344), was able to replicate with wild-type kinetics, while viruses containing deletions of 21 nt (+398 to +418) (construct SD2) or 53 nt (+345 to +397) (construct SD3) displayed diminished capacity in this regard. Both the SD2 and SD3 viruses were also impaired with regard to ability to package viral RNA, while SD1 viruses were not. The SD and SD3 constructs did not revert to increased replication ability in C8166 cells over 6 months in culture. In contrast, long-term passage of the SD2 mutated virus resulted in a restoration of replication capacity, due to the appearance of four separate point mutations. Two of these substitutions were located in leader sequences of viral RNA within the PBS and the dimerization initiation site (DIS), while the other two were located within two distinct Gag proteins, i.e., CA and p6. The biological relevance of three of these point mutations was confirmed by site-directed mutagenesis studies that showed that SD2 viruses containing each of these substitutions had regained a significant degree of viral replication capacity. Thus, leader sequences downstream of the PBS, especially the U5-leader stem and the DIS stem-loop, are important for SIV replication and for packaging of the viral genome.     

Rapid urban malaria appraisal (RUMA) I: Epidemiology of urban malaria in Ouagadougou

Background

There is a low incidence of malaria in Iquitos, Peru, suburbs detected by passive case-detection. This low incidence might be attributable to infections clustered in some households/regions and/or undetected asymptomatic infections.

Methods

Passive case-detection (PCD) during the malaria season (February-July) and an active case-detection (ACD) community-wide survey (March) surveyed 1,907 persons. Each month, April-July, 100-metre at-risk zones were defined by location of Plasmodium falciparum infections in the previous month. Longitudinal ACD and PCD (ACP+PCD) occurred within at-risk zones, where 137 houses (573 persons) were randomly selected as sentinels, each with one month of weekly active sampling. Entomological captures were conducted in the sentinel houses.

Results

The PCD incidence was 0.03 P. falciparum and 0.22 Plasmodium vivax infections/person/malaria-season. However, the ACD+PCD prevalence was 0.13 and 0.39, respectively. One explanation for this 4.33 and 1.77-fold increase, respectively, was infection clustering within at-risk zones and contiguous households. Clustering makes PCD, generalized to the entire population, artificially low. Another attributable-factor was that only 41% and 24% of the P. falciparum and P. vivax infections were associated with fever and 80% of the asymptomatic infections had low-density or absent parasitaemias the following week. After accounting for asymptomatic infections, a 2.6-fold increase in ACD+PCD versus PCD was attributable to clustered transmission in at-risk zones.

Conclusion

Even in low transmission, there are frequent highly-clustered asymptomatic infections, making PCD an inadequate measure of incidence. These findings support a strategy of concentrating ACD and insecticide campaigns in houses adjacent to houses were malaria was detected one month prior.