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Filarial infections (lymphatic filariasis and onchocerciasis) are amongst the major neglected tropical diseases, and together account for more than 120 million infections in tropical and subtropical regions. The gold-standard technique for the diagnosis of filariases relies on the detection of microfilariae (mf) either in blood smears (lymphatic filariasis) or in skin biopsies (onchocerciasis). The secretion of extracellular RNAs (exRNAs) by parasitic nematodes has opened new avenues for the development of novel biomarkers for helminthiases, including filariasis. However, rather little is known about the origin and regulation of these RNAs inside the nematodes. One outstanding question is whether the secretion of small RNAs is distinct across the developmental stages of parasitic nematodes. Similarly, it is not clear whether the secretion of miRNAs is affected by treatment with anthelminthic chemotherapy or their potential as biomarkers for infection. Litomosoides sigmodontis is a murine filarial nematode closely related to filarial nematodes of medical and veterinary importance, including Onchocerca spp. and Brugia spp. L. sigmodontis has been extensively used to decipher multiple aspects of filarial biology, including parasite development, vaccine, and host-pathogen interactions. Therefore, we decided to use this model to address fundamental questions regarding the secretion of small RNAs and their biomarker potential. Our in vitro studies demonstrate that some extracellular miRNAs are enriched in a sexand stage-specific manner in the Excretion/Secretion (ES) products from early larval and adult stages from the rodent filarial nematode Litomosoides sigmodontis. Moreover, our data demonstrates that the gravid adult female worms secrete a plethora of miRNAs enriched in the secretome of this developmental stage when compared to adult males or mf. Further characterization studies show that the miRNAs are likely to be secreted in association with extracellular vesicles (EVs), as previously reported for other parasitic nematodes, including the human pathogen Brugia malayi. Interestingly, Ivermectin, which is typically used to treat filarial infections, does not have consistent effects on the secretion of miRNAs by gravid adult female worms in vitro, requiring further in vivo experiments to determine the effect of IVM on detection of extracellular parasite-derived miRNAs. In vivo experiments, using murine models of infection with L. sigmodontis (gerbils and BALB/c mice), as well as human samples from patients infected with Onchocerca volvulus and cattle infected with Onchocerca ochengi, demonstrated the presence of filarial-derived miRNAs, including female-specific miRNA markers, in biofluids from infected hosts. Further statistical analysis showed that two parasite-derived miRNAs, miR-71 and miR-100d, can significantly discriminate infected animals from naïve controls with high sensitivity/specificity (> 80%/100%). The results presented in this PhD thesis provide an initial framework to understand the secretion of small RNAs throughout nematode development, the potential interactions between anthelminthic chemotherapy and small RNA trafficking and secretion, as well as the use of parasite-derived miRNAs for the development of a new generation of biomarkers for filarial infections.

Brugia malayi is one of three species of nematode known to cause lymphatic filariasis (LF) in humans. LF infects over 120 million people, causing debilitating disease. Various global programs have been launched in the past 20 years to eliminate LF. These programs have greatly scaled up the resources and efforts allocated to halting the transmission and reducing disease burden. Only a few drugs are used to treat LF, and resistance is thus a devastating possibility. Research aimed at identifying new drug targets could therefore prove essential in elimination of LF. Genetic manipulation of B. malayi has been limited to transient transfections. A transfection system allowing for stable integration of transgenic sequences into the nuclear genome of this parasite would enable more robust studies that could lead to identification of novel drug targets and vaccine candidates. The piggyBac (pB) transposon system has been successfully applied to develop a stable transfection system in a variety of species. This system involves two plasmids, a helper and a donor. The donor plasmid contains the target DNA and a selectable marker flanked by specific inverted terminal repeat (ITR) regions. The helper plasmid expresses the pB transposase that will catalyze the precise integration of any DNA report tools necessary to adapt the pB system in B. malayi. Three versions of the donor plasmid were constructed, each containing a Gaussia Luciferase (GLuc) selectable marker but differing only by the fluorescent protein expressed. The construct containing a YFP gene was used to transfect embryos via biolistics to test whether YFP and GLuc are expressed.

The mosquito Aedes polynesiensis, a member of the Aedes scutellaris complex, is the main vector in the South Pacific region of the Wuchereria bancrofti parasite, the causative agent of lymphatic filariasis (LF), and is also a major nuisance biter. Decades of Mass Drug treatment (MDA) have not been successful in elimination LF. Two non-vector species in the Ae. scutellaris complex were introgressed with Ae. polynesiensis to attempt to obtain lines that would produce cytoplasmic incompatibility (CI) with wild populations and/or LF-refractoriness. Despite selection of progeny from Brugia-challenged, non-infective females at each backcross, no refractory line was acquired. However, three lines from crosses between aposymbiotic Ae. polynesiensis and Ae. riversi displayed CI and male mating competiveness suitable for the purpose of population suppression using the incompatible insect technique (IIT). A population study was conducted of potential release sites and the evaluation of monitoring tools for Ae. polynesiensis on Moorea and Tetiaroa, French Polynesia. There was no evidence of active migration between selected islets on the atoll of Tetiaroa, suggesting it is a suitable site for field releases of CI males. The BioGents Sentinel trap was shown to be an efficient and convenient trap suitable for Ae. polynesiensis monitoring. The effects of temperature and larval density on life-table parameters relevant to IIT were examined, including: larval survivorship, developmental time to pupation, male to female ratio, male pupae yield, male size and adult male survival. These findings were used to design and conduct a 14-week field experiment testing CI male strain against an isolated population, using optimized rearing conditions. Approximately 8000 males were released weekly on motu Onetahi, Tetiaroa atoll. Significant sterility was induced by Wolbachia in the targeted female population, supporting the development and scale-up of this approach toward Ae. polynesiensis nuisance and LF transmission reduction.

Lymphatic filariasis is a highly impact disease because it can impair workers and make difficult their social life. Early diagnosis is very important for efficacy of the treatment. The aim of this study was to establish, in a defined population, the prevalence of Wuchereria bancrofti, the causative agent of lymphatic filariasis, using rapid immunochromatographic card test and thick blood smears; compare the immunochromatographic test with the thick blood smear parasitological method, and evaluate different parasitological techniques. Inhabitants of lymphatic filariasis endemic area were examined in Maceió, Alagoas State, Northeasth Brazil (at the edge of a channel - Reginaldo Canal - that crosses the city sectors Feitosa, Jacintinho and Pitanguinha). The examination of 3,000 children between 5 and 10 years old by immunochromatographic test revealed 10 (0,33%) antigen-positive, and of 411 individuals older than 10 years of age only one (0,24%) was antigen-positive. By thick blood smear method, in the same endemic area, among 5,261 children examined between 5 and 10 years old 4 (0,076%) microfilaremic were detected, and 25 (0.13%) from 19,875 individuals older than 10 years of age were found to be microfilaraemic. The parasite antigen assay using rapid immunochromatographic for diagnosis made possible to carry out tests during daytime, in opposition of the traditional thick blood smears method. Comparing the results from immunochromatographic test and thick smears, a increased ability for parasite detection by the immunological method was observed when children between 5-10 years old were examined, being odds relative 4.4 (I.C. 95% = 1.3 - 16.6). However, with individuals older than 10 years of age, no significant difference on parasites detection ability between these techniques was observed. All antigen-positive individuals by immunochromatographic test were examined by membrane blood filtration and none of them were microfilaraemic. Positive individuals by immunochromatographic test and thick blood smears were also positive when submitted to the enzyme-linked immunosorbent assay. The enzyme-linked immunosorbent assay was better than immunochromatographic test in detected W. bancrofti antigen. From the results of immunochromatographic test with children between 5 and 10 years old (age group preconized by WHO to verify active transmission of lymphatic filariasis) it was possible to show a very low prevalence of parasitism in the delimited area, meaning that in a short time Maceió can be free from lymphatic filariasis transmission / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A filariose linfática é uma doença de grande impacto, pois pode incapacitar seus portadores para o trabalho e dificultar seu convívio social, sendo de grande importância o diagnóstico ainda na fase inicial para que o tratamento seja eficaz. O objetivo do presente trabalho foi identificar em população definida, a prevalência de Wuchereria bancrofti, causadora de filariose linfática, utilizando testes de imunocromatografia rápida em cartão e gota espessa de sangue; comparar a imunocromatografia rápida frente ao método parasitológico da gota espessa de sangue, e avaliar diferentes técnicas parasitológicas. Foram examinados moradores da região endêmica de filariose linfática, definida anteriormente em Maceió, AL (parte dos bairros centrais e contíguos Feitosa, Jacintinho e Pitanguinha, ao longo do canal do Reginaldo). Através da imunocromatografia rápida foram avaliadas 3.000 crianças com idade entre 5-10 anos, sendo 10 (0,33%) antígeno-positivo; e entre 411 indivíduos > 10 anos examinados, apenas um (0,24%) foi antígeno-positivo. Através da gota espessa de sangue e na mesma área endêmica, foram examinadas 5.261 crianças com idade entre 5-10 anos, sendo 4 (0,076%) microfilarêmicas, e examinados 19.875 indivíduos > 10 anos, sendo 25 (0,13%) microfilarêmicos. A utilização de imunocromatografia rápida como forma de diagnóstico, através da pesquisa de antígenos do parasito, possibilitou a realização dos exames em horários matutino e vespertino, fato que se opõe ao método tradicional através de gota espessa. Fazendo-se uma comparação entre os resultados obtidos pela imunocromatografia rápida com os da gota espessa pode-se observar uma maior capacidade de detecção dos parasitados pelo método imunológico quando avaliadas crianças de 5-10 anos de idade sendo a odds relativa igual a 4,4 (I.C. 95% = 1,3 16,6); já em indivíduos com > 10 anos não houve diferença significativa na capacidade de detecção de parasitados entre essas técnicas. Todos os indivíduos antígeno-positivo pela imunocromatografia rápida foram submetidos a exames pela filtração de sangue em membrana e nenhum foi microfilarêmico. Os indivíduos positivos através da imunocromatografia e da gota espessa de sangue, foram submetidos ao teste imunoenzimático, sendo todos positivos por essa última técnica. A técnica imunoenzimática mostrou igual capacidade na detecção de antígenos circulantes de W. bancrofti quando comparada com a imunocromatografia rápida. Através dos exames realizados, utilizando a imunocromatografia rápida na faixa etária de 5 a 10 anos (idade preconizada pela OMS para verificação de transmissão ativa da filariose linfática), foi detectada uma prevalência muito baixa da parasitose na área demarcada, mostrando que em pouco tempo a cidade de Maceió-AL poderá estar livre da transmissão da filariose linfática

Filariasis and onchocerciasis are debilitating diseases affecting 120 million people globally. The massive socio-economic impact of these diseases energized the international community to declare a goal of eliminating filariasis 2020. This resulted in a dramatic increase in the efforts to eliminate filariasis and onchocerciasis, employing a strategy of mass drug administration (MDA). However, these programs rely upon the small arsenal of drugs. This leaves these programs vulnerable to failure in the face of developing resistance and local intolerance to the current drug regimens. Thus, new drugs against these infections are critically needed. A homologue of the ecdysone receptor (EcR), a master regulator of development in insects, has been identified in B. malayi. The potential of the EcR as a drug target has been underscored by work in the agricultural industry, where insecticides targeting the ecdysone developmental pathway are effective and non-toxic to non-target species. As the EcR is absent in humans, it represents an attractive potential chemotherapeutic target. The first study investigates the hypothesis that the ecdysone receptor controls the embryogenesis and molting in the filarial parasite. In-vitro embryogram and in-vivo phenotypic studies were conducted to delineate the effect of 20-hydroxyecdysone on the Brugia malayi parasites. The results suggest that the hormone accelerates embryogenesis and causes precocious molts, resulting in the death of the parasite. Further, transcriptomic and proteomic analysis of the ecdysone treated worms provided evidence that the up-regulated genes participate in embryogenesis. Based upon the validation of the ecdysone receptor as a potential drug target, subsequent studies focused on the development of a drug discovery model to screen for agonists and antagonists of the B. malayi ecdysone receptor. A stable cell line was created to aid the high throughput screening to rapidly identity agonist and antagonist compounds. A total of 7 agonists and 2 antagonists were identified. A homology model of the BmEcR ligand-binding domain was created as an alternate method for virtual screening of small molecules as well as to study the ligand-receptor interactions. The hits identified with the assay were docked in the active site of the BmEcR homology model providing an excellent correspondence of data between the molecular assay and the virtual screening method.

Lymphatic filariasis (LF) is an incapacitating disease caused by three filarial nematodes belonging to the family Onchocercidae, namely Brugia timori, Wuchereria bancrofti and Brugia timori. An estimated 90% of lymphatic filariasis cases globally are caused by Wuchereria bancrofti. To evaluate the success of the Global Program to eliminate Lymphatic Filariasis it is essential to monitor the frequency of larval infection in the mosquito vector. Molecular methods to detect Wuchereria bancrofti DNA in mosquitoes have been in existence since 1996. However these methods have not been widely adopted due to the high cost associated with them and the inability of these assays to distinguish between immature and infectious stages in the mosquito vector. The overall aim of this project was to modify, as previously described in literature, the Laney real time PCR assay to permit it to be used in an end point Reverse Transcriptase (RT)-PCR ELISA format. The endpoint PCR-ELISA uses inexpensive conventional thermocyclers and inexpensive reagents and probes. To accomplish this overall goal the specific objectives were to produce a positive control RNAs for Wb-cut-1.2 L3 specific RT-PCR and Wb-TPH RT-PCR that detects any stage of the parasite, and to adapt the detection of both transcripts to a PCR-ELISA format. Positive RNA controls were prepared and purified using template cDNA made available through FR3, subsequent development and optimization of the RT PCR ELISA was achieved through the adaptation of the Onchocerca volvulus O150 PCR ELISA protocol. We found a 16-fold difference in the limit of detection between the ELISA assay and conventional end point RT-PCR when we did a 2-fold dilution series of PCR products for both Wb-Cut-1.2 and Wb-TPH. This indicates that our assay was 16 times more sensitive than the use of regular agarose gel electrophoresis to analyze PCR products. The limit of detection with ELISA and gel analysis were comparable when a 10-fold dilution series of the positive control RNA template was done. The RT-PCR ELISA takes a day to complete and up to three 96 well plates a day can be processed compared to the limited number of samples that can be analyzed by gel electrophoresis a day. It is anticipated that our assay will be used in the molecular xenomonitoring of Wuchereria bancrofti providing earlier time-point assessments of LF infection in endemic areas. In areas that were once endemic, our diagnostic tool will play a pivotal role in monitoring LF resurgence.

archives@tulane.edu / 1 / Kimberly Michelle Koporc

Previous studies have indicated that the promoters of the human filarial parasite Brugia malayi are unusual in that they do not exhibit the CAAT or TATAA sequences usually found in the core domains of promoters of most eukaryotic organisms. Analysis of the promoters of the ribosomal proteins showed that the region flanking the splice leader (SL) addition site plays an important role in transcription and may function as the core promoter domain in B. malayi. To test the hypothesis that the SL addition domain is the most important essential region of the ribosomal protein promoters, the SL addition site of the BmRPL13 gene was replaced with the SL addition domains from other ribosomal protein genes from B. malayi. The promoter activity of the replacement constructs were tested using a transient transfection dual luciferase assay. Promoter activity with RPL13 replacement constructs was correlated with that seen in the wild type promoters, suggesting that roughly 80% of the variations seen in promoter activity among ribosomal protein promoters is due to variation in the SL core promoter domain.