A comparative study of MHC Class-II HLA-DRbeta1*0401-Col II and HLA-DRbeta1*0101-HA complexes: a theoretical point of view

A study was performed on the HLA-DRbeta1*0401-collagen II peptide complex using the computation of electronic multipolar variables proposed by us previously. Furthermore, these results were compared with those obtained for the HLA-DRbeta1*0101-haemaglutinin peptide complex studied by us with the same tools, confirming that Pocket 1 for this new complex is also the most important pocket for the interaction between the presenting molecule and the presented peptide. The pocket hierarchy established for HLA-DRbeta1*0401 allele was P1 > P9 approximately P7 > P6 > P4, whilst a P1 > P4 > P9 approximately P7>P6 pocket hierarchy was found for HLA-DRbeta1*0101, showing how the relative importance of the pockets distinguishes the two alleles. There are high correlation levels with experimental results (when possible), again confirming the validity of using calculated values for electronic multipolar variables as a useful tool for studying interactions between immune system molecules and peptides.     

Independent origins of resistance or susceptibility of parasitic wasps to a defensive symbiont

Insect microbe associations are diverse, widespread, and influential. Among the fitness effects of microbes on their hosts, defense against natural enemies is increasingly recognized as ubiquitous, particularly among those associations involving heritable, yet facultative, bacteria. Protective mutualisms generate complex ecological and coevolutionary dynamics that are only beginning to be elucidated. These depend in part on the degree to which symbiont‐mediated protection exhibits specificity to one or more members of the natural enemy community. Recent findings in a well‐studied defensive mutualism system (i.e., aphids, bacteria, parasitoid wasps) reveal repeated instances of evolution of susceptibility or resistance to defensive bacteria by parasitoids. This study searched for similar patterns in an emerging model system for defensive mutualisms: the interaction of Drosophila, bacteria in the genus Spiroplasma, and wasps that parasitize larval stages of Drosophila. Previous work indicated that three divergent species of parasitic wasps are strongly inhibited by the presence of Spiroplasma in three divergent species of Drosophila, including D. melanogaster. The results of this study uncovered two additional wasp species that are susceptible to Spiroplasma and two that are unaffected by Spiroplasma, implying at least two instances of loss or gain of susceptibility to Spiroplasma among larval parasitoids of Drosophila.     

Domestic scorpion control with pyrethroid insecticides in Mexico

Scorpion stings cause more morbidity in Mexico than any other country, leading to about 100 deaths annually. In 1999, the State of Morelos reported nine deaths among 30663 cases of scorpion sting. To replace lindane used for scorpion control, field trials of pyrethroid pesticides were undertaken in Morelos during 1998-2000 at the village of Chalcatzingo (population initially with 2760 inhabitants and 530 houses). Pre-intervention surveys detected scorpions (Scorpiones: Buthidae) of two species in the majority of houses: Centruroides limpidus limpidus Karsch outnumbering Vaejovis mexicanus smithi Koch. Scorpion prevalence was assessed, pre- and post-spray, directly by searching (40 min/house) and by householder reports of sightings inside houses. Pre-intervention perceptions of scorpion abundance were similar for all areas, with sightings in 12-18% of houses, whereas daytime searches detected more infestations in eastern parts of the village (prevalence 17% indoors, 22% outdoors) than in other sectors (9% indoors, 14% outdoors). Pyrethroids were evaluated as residual treatments in separate sectors of Chalcatzingo, with almost complete coverage indoors and peridomestically, using the following four formulations: bifenthrin 10% wettable powder (WP) applied at 50mg a.i./m2, cyfluthrin 10% WP (Solfac 10 WP) at 44-55 mg a.i./m2, deltamethrin 2.5% suspension concentrate (Biothrin 25 SC) at 11 mg a.i./m2 and 5% WP (K-Othrine 50 WP) at 35 mg a.i./m2. Phase 1 compared bifenthrin 10 WP, Solfac 10 WP and Biothrin 25 SC sprayed in December 1998; phase 2 compared Solfac 10 WP and K-Othrine 50 WP sprayed in June and again in December 2000, with follow-up surveys of scorpions one month post-spray and subsequently. Scorpion prevalence was reduced by 64-77% peridomestically one month post-spray and by 83, 46 and 15% in houses sprayed with cyfluthrin WP, bifenthrin WP or deltamethrin SC, respectively. Householder reports of sighting scorpions indoors were 33-85% below pre-intervention levels. Cumulative effects of the three spray-rounds over 3 years reduced scorpion prevalence by approximately 60% in the deltamethrin WP re-sprayed area and by approximately 90% in the cyfluthrin WP re-sprayed area. Householder sightings also fell by 67 and 28% in the cyfluthrin and delta-methrin re-sprayed areas, respectively. Operational efficacy of these products against scorpions at the dosages applied was ranked as cyfluthrin WP > bifenthrin WP > deltamethrin SC > WP. Reported cases of scorpion sting intoxication fell by 17% during this study after having risen by approximately 40% over four previous years.     

Allele effects in MHC-peptide interactions: a theoretical analysis of HLA-DRbeta1*0101-HA and HLA-DRbeta1*0401-HA complexes

HLA-DRbeta1*0101-HA and HLA-DRbeta1*0401-HA complexes are studied and compared by means of their computationally derived multipolar moments and electrostatic potentials. Changes in electrostatic potential are associated with definite pocket interaction profiles. Thus, Pocket 1 projects itself as an anchoring pocket for both complexes, in accordance with experimental results. While Pocket 4 has an anchoring profile in the HLA-DRbeta1*0101 allele, it presents itself as modulating pocket-peptide interactions in HLA-DRbeta1*0401. Pockets 6 and 7 both strongly contribute to allele specificity, with Pocket 7 being very important for HLA-DRbeta1*0401-HA. Pocket 9 acts as a "double purpose" interaction site for both alleles. It both projects itself as an anchoring pocket as well as modulating pocket-peptide interactions.     

Distribution of domestic triatominae and stratification of Chagas Disease transmission in Oaxaca, Mexico

Mexico has 18 species of Triatomine bugs (Hemiptera: Reduviidae) reported to be vectors of Trypanosoma cruzi. Chagas Disease is widespread in Mexico, with up to 3.5% seropositivity of human transfusion blood. The State of Oaxaca has the longest history of endemic Chagas Disease, based on acute and chronic case reports, and of entomological surveys in the country. However, the State health care services need more information on current risks of vector transmission. In order to identify and characterize areas of transmission in Oaxaca and to stratify the vector potential, the distribution of domestic Triatominae was surveyed during 1996-98 in collaboration with the primary health care services and local communities. Villages were studied in 11% of 570 municipalities in Oaxaca. Eight triatomine species were found in domestic and peri-domestic habitats: Triatoma barberi Usinger, T. bolivari Carcavallo et al., T. dimidiata (Latreille), T. mazzottii Usinger, T. nitida Usinger, T. pallidipennis (Stal), T. phyllosoma (Burmeister) and Rhodnius prolixus Stal. For each triatomine species in Oaxaca, the range of distribution and habitat characteristics are described. Habitat partitioning, principally based on altitude and mean annual precipitation, limited the overlap of distribution between species. Relatively consistent altitude of human settlements facilitates the dispersion of individual species within microregions. Entomological indices of house infestation were used to estimate that approximately 50% of the human population (1,874,320 inhabitants) would be at risk of vector transmission, with a minimum of 134,320 infected people and 40,280 chronic cases of Chagas Disease currently in Oaxaca.     

Risk factors associated with house infestation by the Chagas disease vector Triatoma pallidipennis in Cuernavaca metropolitan area, Mexico

Abstract. Chagas disease caused by infection with Trypanosoma cruzi Chagas (Kinetoplastida: Trypanosomatidae) is widespread in Mexico, transmitted by various triatomine bugs (Hemiptera: Reduviidae). The only domestic vector in Cuernavaca (population 650 000) is Triatoma pallidipennis (Ståhl) with T. cruzi seroprevalence ranging from 1% to 9% in the resident human population. We surveyed possible risk factors for T. pallidipennis infestation at Cuernavaca (altitude 1200–2200 m) on south-western slopes of the Sierra Madre Occidental. This metropolitan area (with five administrative counties) has rapid urbanization, forested environs and proliferation of ‘weekend housing’ for visitors from Mexico City, 60 km to the north. To assess factors associated with T. pallidipennis infestation, we first stratified Cuernavaca by altitude and by socio-economic status of population catchment units (PCUs). Within each PCU, one to three blocks were chosen for cluster sampling (three houses/block) and information about Chagas disease was distributed. After obtaining signed consent from householders, representative houses were routinely and opportunistically inspected for T. pallidipennis and surveyed for demographic, economic, physical and other potential risk factors. Of the 1129 houses assessed, T. pallidipennis was found in 4.1% (range 3.0–6.8% per county) and the T. cruzi infection rate was ∼50% in bugs. Rates of house infestation in poor PCUs were double those in higher socio-economic strata (odds ratio 2.12, confidence interval 1.03–4.3), with >4-fold greater crowding index of T. pallidipennis. The bug density index was inversely correlated with PCU altitude and socio-economic category (altitude of homes being associated with prosperity), while the bug colonization index (presence of nymphs indicating breeding) did not vary significantly across the PCU categories, but did vary according to altitude. Multivariate regression analysis showed that the most significant risk factors associated with T. pallidipennis infestation were lower altitude (linked with lower socio-economic status), garden area >80 m², dogs at liberty to enter the house, occurrence of squirrels and opossums around the house, presence of pigs in the surrounding area and having at least one of the adjacent lots empty (unconstructed). Householders who had received information about Chagas disease comprised 33% from infested houses (14/42) but only 15% from non-infested houses (148/984). Hence, the awareness of Chagas disease was significantly associated with having a bug-free house (P < 0.01). When shown specimens of T. pallidipennis, the proportions of householders who recognized them were 78% from infested houses but only 29% of those with uninfested houses. Given the low infestation rates and the high capacity of the population to act appropriately once they have received information regarding this disease and its vector, relevant health education is expected to have a significant impact on triatomine control in this metropolitan area.     

Evaluation of a pelleted diet for larval mass-rearing of Anastrepha ludens and Anastrepha obliqua

Most artificial diets used for mass-rearing of fruit fly larvae involve the purchase and independent weighing of each ingredient of the formulation, followed by mixing and diet preparation process. A ready-to-use formulation would avoid this time-consuming task and simplify the preparation procedure, leading to a more standardized diet. In this work, we compared life-history traits and survival and developmental parameters of Anastrepha ludens Loew and Anastrepha obliqua (Macquart) (Diptera: Tephritidae) reared on two formulations of an artificial diet. Two experiments were performed; first, a conventional non-pelleted diet was compared to a newly developed pelleted diet, which was mixed with water before being given to the larvae. The second experiment consisted of a comparison between the pelleted diet which was stirred in a mixer with water and dissolved preservatives and a pelleted diet which was only soaked in water with dissolved preservatives. We found that the pelleted diet allowed the mass-rearing of A. ludens and A. obliqua. Moreover, feeding larvae with pelleted diet led to increased weight of the larva by 7.4 and 11.8%, and of the pupa by 9.5 and 16.7% for A. ludens and A. obliqua, respectively, compared to conventional diet. For process evaluation, the number of activities, handling time, reception, storage, and larval diet preparation were recorded. The pelleted diet only needed soaking in water containing preservatives, thereby simplifying the mass-rearing process and saving time, space, and labour. Pelletizing is a versatile technology that can be adjusted for better physicochemical quality and reduced microbiological risk. This diet should be of particular interest for the mass-rearing process in ‘sterile insect technique’ applications.     

A second locus for familial high myopia maps to chromosome 12q.

Myopia, or nearsightedness, is the most common eye disorder worldwide. "Pathologic" high myopia, or myopia of <=-6.00 diopters, predisposes individuals to retinal detachment, macular degeneration, cataract, or glaucoma. A locus for autosomal dominant pathologic high myopia has been mapped to 18p11.31. We now report significant linkage of high myopia to a second locus at the 12q21-23 region in a large German/Italian family. The family had no clinical evidence of connective-tissue abnormalities or glaucoma. The average age at diagnosis of myopia was 5.9 years. The average spherical-component refractive error for the affected individuals was -9.47 diopters. Markers flanking or intragenic to the genes for the 18p locus, Stickler syndromes type I and II (12q13.1-q13.3 and 6p21.3), Marfan syndrome (15q21.1), and juvenile glaucoma (chromosome 1q21-q31) showed no linkage to the myopia in this family. The maximum LOD score with two-point linkage analysis in this pedigree was 3.85 at a recombination fraction of .0010, for markers D12S1706 and D12S327. Recombination events identified markers D12S1684 and D12S1605 as flanking markers that define a 30.1-cM interval on chromosome 12q21-23, for the second myopia gene. These results confirm genetic heterogeneity of myopia. The identification of this gene may provide insight into the pathophysiology of myopia and eye development.