A Community-Based Study of Factors Associated with Continuing Transmission of Lymphatic Filariasis in Leogane,Haiti

Seven rounds of mass drug administration (MDA) have been administered in Leogane, Haiti, an area hyperendemic for lymphatic filariasis (LF). Sentinel site surveys showed that the prevalence of microfilaremia was reduced to <1% from levels as high as 15.5%, suggesting that transmission had been reduced. A separate 30-cluster survey of 2- to 4-year-old children was conducted to determine if MDA interrupted transmission. Antigen and antifilarial antibody prevalence were 14.3% and 19.7%, respectively. Follow-up surveys were done in 6 villages, including those selected for the cluster survey, to assess risk factors related to continued LF transmission and to pinpoint hotspots of transmission. One hundred houses were mapped in each village using GPS-enabled PDAs, and then 30 houses and 10 alternates were chosen for testing. All individuals in selected houses were asked to participate in a short survey about participation in MDA, history of residence in Leogane and general knowledge of LF. Survey teams returned to the houses at night to collect blood for antigen testing, microfilaremia and Bm14 antibody testing and collected mosquitoes from these communities in parallel. Antigen prevalence was highly variable among the 6 villages, with the highest being 38.2% (Dampus) and the lowest being 2.9% (Corail Lemaire); overall antigen prevalence was 18.5%. Initial cluster surveys of 2- to 4-year-old children were not related to community antigen prevalence. Nearest neighbor analysis found evidence of clustering of infection suggesting that LF infection was focal in distribution. Antigen prevalence among individuals who were systematically noncompliant with the MDAs, i.e. they had never participated, was significantly higher than among compliant individuals (p<0.05). A logistic regression model found that of the factors examined for association with infection, only noncompliance was significantly associated with infection. Thus, continuing transmission of LF seems to be linked to rates of systematic noncompliance.     

A blueprint for success: integration of neglected tropical disease control programmes

The rapid expansion of chemotherapy-based control programmes for neglected tropical diseases has been catalysed by funding from the Bill and Melinda Gates Foundation, donations of several drugs from pharmaceutical manufacturers, and the reduced price of the drug praziquantel. Focussing on lymphatic filariasis, schistosomiasis and soil-transmitted helminthiasis, we review here the progress made to date with the implementation and integration of large-scale control programmes. Unresolved issues include a means for rapid identification of communities at highest risk of co-morbidity, cost-effective approaches for integrating the technical interventions into setting-specific packages, and determination of the most appropriate and sustainable delivery systems.     

PCR and Mosquito dissection as tools to monitor filarial infection levels following mass treatment

BACKGROUND: Entomological methods may provide important tools for monitoring the progress of lymphatic filariasis elimination programs. In this study, we compared dissection of the vector, Culex quinquefasciatus, with the polymerase chain reaction (PCR) to assess filarial infection levels in mosquitoes in the context of a lymphatic filariasis elimination program in Leogane, Haiti. METHODS: Mosquitoes were collected using gravid traps located in 4 sentinel communities with Wuchereria bancrofti microfilaria prevalence that ranged from 0.8% to 15.9%. Captured mosquitoes were divided between dissection, to enumerate W. bancrofti larvae (L1, L2, L3) and desiccation for later analysis by PCR. PCR was conducted on DNA extracts from pooled mosquitoes (1-15 pooled females) utilizing a competitive PCR system with primers specific for the Ssp I repeat. PCR products were analyzed with a hybridization ELISA using probes specific for a control sequence and the Ssp I repeat. RESULTS: The prevalence of mosquito infection with W. bancrofti ranged from 0%-3.66% by dissection (L1-L3) and point estimates of infection prevalence, as assayed by PCR, ranged from 0.25% - 9.16%. Following mass treatment, W. bancrofti infection prevalence dropped significantly as determined by PCR and dissection in 2 of the 4 sentinel sites (Leogane and Barrier Jeudi, P = 0.04 and P = 0.005, respectively). Although transmission declined in the other two sites, larval recoveries were low and these changes were not statistically significant. DISCUSSION: Our results suggest that a single round of mass treatment can have an impact on transmission of lymphatic filariasis. The use of entomologic methods as a tool to monitor filariasis programs and the statistical limitations of mosquito trapping are discussed.     

Structural requirements of carbohydrates to bind Agaricus bisporus lectin

Galbeta1-3GalNAc (T-disaccharide) and related molecules were assayed to describe the structural requirements of carbohydrates to bind Agaricus bisporus lectin (ABL). Results provide insight into the most relevant regions of T-disaccharide involved in the binding of ABL. It was found that monosaccharides bind ABL weakly indicating a more extended carbohydrate-binding site as compared to those involvedin the T- disaccharide specific lectins such as jacalin and peanut agglutinin. Lacto-N-biose (Galbeta1-3GlcNAc) unlike T-disaccharide, is unable to inhibit the ABL interaction, thus showing the great importance of the position of the axial C-4 hydroxyl group of GalNAc in T-disaccharide. This finding could explain the inhibitory ability of Galbeta1-6GlcNAc and lactose because C-4 and C-3 hydroxyl groups of reducing Glc, respectively, occupy a similar position as reported by conformational analysis. From the comparison of different glycolipids bearing terminal T-disaccharide bound to different linkages, it can be seen than ABL binding is even more impaired by an adjacent C-6 residual position than by the anomeric influence of T-disaccharide. Furthermore, the addition of beta-GlcNAc to the terminal T-disaccharide in C-3 position of Gal does not affect the ABL binding whereas if an anionic group such as glucuronic acid is added to C-3, the binding is partially affected. These findings demonstrate that ABL holds a particular binding nature different from that of other T-disaccharide specific lectins.      

脂多糖通过补体途径诱导小鼠产生白三烯B4

目的:研究脂多糖(LPS)对人血清中补体系统的激活及在小鼠模型中诱导产生白三烯B4(LTB4)。方法:LPS包被ELISA板,利用血清中补体C4、C3沉积实验检测补体成分被LPS活化的情况,通过尾静脉注射小鼠LPS后不同时间点ELISA定量检测LTB4,评价补体系统的活化和炎症因子的产生。结果与结论:血清系统ELISA检测发现LPS可以激活补体系统,且以凝集素途径为主;动物实验中LTB4被LPS诱导后1～3 h达到峰值,之后回落。C1INH对血清补体活化和动物模型中LTB4的产生均有显著抑制。     

Recombinant antigen-based antibody assays for the diagnosis and surveillance of lymphatic filariasis - a multicenter trial

The development of antifilarial antibody responses is a characteristic feature of infection with filarial parasites. It should be possible to exploit this fact to develop tools to monitor the progress of the global program to eliminate lymphatic filariasis (LF); however, assays based on parasite extracts suffer from a number of limitations, including the paucity of parasite material, the difficulty of assay standardization and problems with assay specificity. In principle, assays based on recombinant filarial antigens should address these limitations and provide useful tools for diagnosis and surveillance of LF. The present multicenter study was designed to compare the performance of antibody assays for filariasis based on recombinant antigens Bm14, WbSXP, and BmR1. Coded serum specimens were distributed to five participating laboratories where assays for each antigen were conducted in parallel. Assays based on Bm14, WbSXP, or BmR1 demonstrated good sensitivity (>90%) for field use and none of the assays demonstrated reactivity with specimens from persons with non-filarial helminth infections. Limitations of the assays are discussed. Well-designed field studies are now needed to assess sampling methodology and the application of antibody testing to the monitoring and surveillance of LF elimination programs.     

Changes in Antibody Levels during and following an Episode of Acute Adenolymphangitis (ADL) among Lymphedema Patients in Léogane,Haiti

Introduction

Episodes of acute adenolymphangitis (ADL) are often the first clinical sign of lymphatic filariasis (LF). They are often accompanied by swelling of the affected limb, inflammation, fever, and general malaise and lead to the progression of lymphedema. Although ADL episodes have been studied for a century or more, questions still remain as to their etiology. We quantified antibody levels to pathogens that potentially contribute to ADL episodes during and after an episode among lymphedema patients in Léogâne, Haiti. We estimated the proportion of ADL episodes hypothesized to be attributed to specific pathogens.

Methods

We measured antibody levels to specific pathogens during and following an ADL episode among 41 lymphedema patients enrolled in a cohort study in Léogâne, Haiti. We calculated the absolute and relative changes in antibody levels between the ADL and convalescent time points. We calculated the proportion of episodes that demonstrated a two-fold increase in antibody level for several bacterial, fungal, and filarial pathogens.

Results

Our results showed the greatest proportion of two-fold changes in antibody levels for the carbohydrate antigen Streptococcus group A, followed by IgG2 responses to a soluble filarial antigen (BpG2), Streptococcal Pyrogenic Exotoxin B, and an antigen for the fungal pathogen Candida. When comparing the median antibody level during the ADL episode to the median antibody level at the convalescent time point, only the antigens for Pseudomonas species (P-value = 0.0351) and Streptolysin O (P-value = 0.0074) showed a significant result.

Conclusion

Although our results are limited by the lack of a control group and few antibody responses, they provide some evidence for infection with Streptococcus A as a potential contributing factor to ADL episodes. Our results add to the current evidence and illustrate the importance of determining the causal role of bacterial and fungal pathogens and immunological antifilarial response in ADL episodes.     

Serological Measures of Malaria Transmission in Haiti: Comparison of Longitudinal and Cross-Sectional Methods

Background

Efforts to monitor malaria transmission increasingly use cross-sectional surveys to estimate transmission intensity from seroprevalence data using malarial antibodies. To date, seroconversion rates estimated from cross-sectional surveys have not been compared to rates estimated in prospective cohorts. Our objective was to compare seroconversion rates estimated in a prospective cohort with those from a cross-sectional survey in a low-transmission population.

Methods and Findings

The analysis included two studies from Haiti: a prospective cohort of 142 children ages ≤11 years followed for up to 9 years, and a concurrent cross-sectional survey of 383 individuals ages 0–90 years old. From all individuals, we analyzed 1,154 blood spot specimens for the malaria antibody MSP-1₁₉ using a multiplex bead antigen assay. We classified individuals as positive for malaria using a cutoff derived from the mean plus 3 standard deviations in antibody responses from a negative control set of unexposed individuals. We estimated prospective seroconversion rates from the longitudinal cohort based on 13 incident seroconversions among 646 person-years at risk. We also estimated seroconversion rates from the cross-sectional survey using a reversible catalytic model fit with maximum likelihood. We found the two approaches provided consistent results: the seroconversion rate for ages ≤11 years was 0.020 (0.010, 0.032) estimated prospectively versus 0.023 (0.001, 0.052) in the cross-sectional survey.

Conclusions

The estimation of seroconversion rates using cross-sectional data is a widespread and generalizable problem for many infectious diseases that can be measured using antibody titers. The consistency between these two estimates lends credibility to model-based estimates of malaria seroconversion rates using cross-sectional surveys. This study also demonstrates the utility of including malaria antibody measures in multiplex assays alongside targets for vaccine coverage and other neglected tropical diseases, which together could comprise an integrated, large-scale serological surveillance platform.     

氨氯地平联合依那普利治疗原发性高血压的临床疗效及对患者左心室肥厚的影响

摘要目的：探讨氨氯地平联合依那普利治疗原发性高血压的临床效果,观察联合用药对左心室肥厚的影响。方法：选择本院收治的原发性高血压患者92例,随机分为观察组和对照组,各46例,对照组给予苯磺酸左旋氨氯地平5mg,1次／d,口服;观察组在对照组基础上加用马来酸依那普利10mg,2次／d,口服,疗程均为24周。观察两组治疗前后血压变化,应用超声心动图测量两组左心室厚度变化。结果：治疗后,观察组总有效率为91_3％;对照组总有效率为73．9％,观察组总有效率高于对照组（P〈0．05）。治疗前两组心率、血压比较无统计学差异（P〉0．05）,治疗后两组血压均明显降低,观察组收缩压、舒张压明显低于对照组（P〈O．05）;观察组心率明显低于对照组（P〈0．01）。治疗前两组左心室舒张末期室间隔厚度（Leaventricularend—diastolicventricularseptalthickness,IVST）、左心室后壁厚度（1eftventricularposteriorwallthickness,U,PwT）和左室射血分数（Leftventricularejectionfxaction,LVEF）比较无统计学差异（P〉0．05）;治疗后观察组IVST、L、,PwT明显低于对照组,LVEF明显高于对照组（P〈0．05）。结论：氨氯地平联合依那普利治疗原发性高血压能有效扭转左心室肥厚,降压效果较单独应用氨氯地平更佳。     

重组人MASP2蛋白在大肠杆菌中的表达和纯化

目的:获得酶原形式的重组人甘露聚糖结合凝集素相关丝氨酸蛋白酶2(MASP2)。方法:在大肠杆菌中诱导表达重组人MASP2全长蛋白,包涵体裂解后,经复性、透析、浓缩、考马斯亮蓝染色、SDS-PAGE及Western印迹,鉴定纯化结果及酶活性。结果:复性后的MASP2蛋白经考马斯亮蓝染色未见杂带。自激活实验表明,当MASP2浓度在1μmool/L以下时,无论在4℃还是37℃,都能较稳定地保持酶原形式;蛋白浓度为3.5μmool/L时只能在4℃保持稳定,37℃发生自激活;蛋白浓度达到12μmool/L后,在4℃时已不能稳定存在。结论:获得了较纯的重组人MASP2蛋白,且具有自激活活性。