Malaria, caused by the protozoan Plasmodium, is a devastating disease with over 200 million new cases reported globally every year. Although immunization is arguably the best strategy to eliminate malaria, despite decades of research in this area we do not have an effective, clinically approved antimalarial vaccine. The current impetus in the field is to develop vaccines directed at the pre-erythrocytic developmental stages of Plasmodium, utilizing novel vaccination platforms. We here review the most promising pre-erythrocytic stage antimalarial vaccine candidates.
We assessed the feasibility of using a test, treat, track, test, and treat (5T) active surveillance strategy to identify and treat individuals with schistosomiasis in three very low-prevalence villages in Kafr El Sheikh Governorate, Egypt. Primary index cases (PICs) were identified using the point-of-care circulating cathodic antigen (POC-CCA) assay in schools, in rural health units (retesting individuals with positive Kato-Katz examinations over the previous 6 months), and at potential water transmission sites identified by PICs and field observations. Primary cases identified potential second-generation cases-people with whom they shared water activities-who were then tracked, tested, and treated if infected. Those sharing water activities with second-generation cases were also tested. The yield of PICs from the three venues were 128 of 3,576 schoolchildren (3.6%), 42 of 696 in rural health units (6.0%), and 83 of 1,156 at water contact sites (7.2%). There were 118 second- and 19 third-generation cases identified. Persons testing positive were treated with praziquantel. Of 388 persons treated, 368 (94.8%) had posttreatment POC-CCA tests 3-4 weeks after treatment, and 81.8% (301) became negative. The 67 persons remaining positive had negative results after a second treatment. Therefore, all those found positive, treated, and followed up were negative following one or two treatments. Analysis of efforts as expressed in person-hours indicates that 4,459 person-hours were required for these 5T activities, with nearly 65% of that time spent carrying out interviews, treatments, and evaluations following treatment. The 5T strategy appears feasible and acceptable as programs move toward elimination.
It all began with a simple phone call and now, more than a decade later, the Schistosomiasis Consortium for Operational Control and Evaluation (SCORE) is preparing to pass the baton to new groups of investigators working on understanding and controlling schistosomiasis. Under the direction of Dan Colley, a member of the Center for Tropical and Emerging Global Diseases and professor emeritus of microbiology at the University of Georgia, SCORE has advanced the scientific understanding of how to control schistosomiasis and has moved us closer to the elimination of this devastating and sometimes deadly disease.
In January 2008, Colley received a phone call from Dr. Julie Jacobson of the Bill & Melinda Gates Foundation (BMGF). She wanted Colley to lead a program on how best to control and move towards elimination of schistosomiasis. This program would not be your typical research program.
First, it would involve national Neglected Tropical Disease (NTD) programs, the World Health Organization (WHO), and others around the globe who were pursuing ways to control morbidity due to Schistosoma mansoni and S. haematobium and their transmission.
“While there were and are now many individual research programs in academia, governments and NGOs working on how to control and eliminate schistosomiasis, SCORE was somewhat different in its size and complexity, allowing it to mount large-scale studies and do so comparatively across different countries,” said Colley.
Second, the program would not focus on basic research, but the results of their research would be more directly applicable to improving national NTD control programs.
“Julie made it clear that the BMGF was not interested, at this time, in funding basic research on either anti-schistosomal drug development or anti-schistosomal vaccine development,” said Colley.
While there are several Schistosoma spp. that infect humans worldwide, this program would focus only on two species, S. mansoni and S. haematobium. Furthermore, they would focus primarily on interventions to control these infections in Africa.
With the parameters laid out and the definition of what constitutes operational research, Colley agreed to gather together a consortium of scientists and SCORE was born: their mission – to undertake operational research that could support National NTD managers in making decisions about how to best control and/or eliminate schistosomiasis in their countries.
“The vision was that research findings would be useful to the WHO in revising current and developing new guidelines on how best to control and move towards elimination of schistosomiasis,” said Colley.
Over the past decade, their mission has not changed but how they pursued that mission evolved as situations change., such as the increased availability of praziquantel, made possible through a donation of the drug by Merck, AG; a more realistic vision of the integration of NTD programs; and the desire of funders to move more quickly from control of morbidity to elimination of the disease.
Over the past decade, SCORE has pursued a number of field and laboratory-based projects in 9 African countries. Several of these studies were included in the categories of gaining control, sustaining control of schistosomiasis, or eliminating its transmission.
The control projects compared how best to deliver Mass Drug Administration (MDA) of praziquantel. Gaining control projects were focused on areas with high prevalence of infection and included research related to subtle morbidity, snail infection, and schistosome population genetics. Sustaining control project focused on areas with moderate prevalence as these areas had already achieved a level of control or simply had lower levels of prevalence.
The original focus of the elimination research project was on Zanzibar and the elimination of S. haematobium. They hoped to inform effective strategies of moving an area of low infection prevalence to total elimination of schistosomiasis. In 2013, with supplemental funding, SCORE expanded its focus on elimination research to focus on S. mansoni in Africa. However, due to conflicts within the country where this research was implemented, SCORE and partners had to withdraw. Instead, SCORE identified another elimination priority on the impact of timed interventions on seasonally transmitted schistosomiasis. This research was conducted in Cote d’Ivoire in a large area with S. haematobium.
Another group of projects focused on tools needed to evaluate control and elimination efforts. They were able to field evaluate the point-of-care circulating cathodic antigen (POC-CCA) urine assay for its use as a mapping tool for S. mansoni infection in humans. They also conducted research and evaluation on highly sensitive and specific human diagnostic tests for schistosomiasis and developed and used tools for schistosome population genetics studies.
Keeping with their mission of supporting national NTD program managers in decision-making, SCORE provided critical information by analyzing and synthesizing existing data in a series of 7 Rapid Answers Projects. Each project resulted in a 2 page brochure providing essential information on a topic of interest to program managers. These brochures are available online at https://score.uga.edu/projects/rapid-answers-project/
And finally, in order to optimize the use of the data generated in these large studies, they collected and made them accessible to the scientific community and other stakeholders. SCORE worked with database programmers and statisticians at UGA to integrate the data from various study sites and conduct analyses of combined data, while providing them to all investigators by depositing them in an open database system, ClinEpiDB.
In July, the American Journal of Tropical Medicine and Hygiene published a supplement that summarizes many of the activities, lessons learned, and work that still needs to be done in 16 articles. This supplement is introduced with a guest editorial by N. Robert Bergquist.
Briefly the key findings and take away messages are summarized in Table 1 of the article “Contributions of the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) to Schistosomiasis Control and Eliminations: Key Findings and Messages for Future Goals, Thresholds, and Operational Research” (https://doi.org/10.4269/ajtmh.19-0787).
“The impact of SCORE’s findings and messages will depend on their uptake by the WHO/NTD schistosomiasis guidelines development group in the formulation of revised and new guidelines for the control and elimination of schistosomiasis, and then whether national NTD programs consider them worthy of adoption and implementation,” said Colley.
Some of the findings from SCORE are already being implemented, such as the use of the POC-CCA rapid cassette test for mapping S. mansoni prevalence in low-to-moderate areas of schistosomiasis. Other findings, such as the occurrence of persistent hotspots in large-scale MDA programs, are now being considered by other research groups and national NTD programs.
This isn’t really good-bye
SCORE was built on the foundation of a previously BMGF-funded program – the Schistosomiasis Control Initiative (SCI). The goal of SCI, which is now a private non-governmental organization, was to determine if preventive chemotherapy, as recommended by the WHO, could be implemented countrywide to control schistosomiasis.
“It was an ambitious undertaking that SCI accomplished in multiple African countries,” said Colley. “Now knowing that with the funding, persistence, and training, MDA countrywide could be done, the BMGF decided to fund a program to compare the frequency and platforms for MDA distribution.”
Of course, that program became SCORE. They took what SCI learned and asked additional questions about how best to conduct the preventive chemotherapy by MDA, and explore what tools were needed to do it better. Now that SCORE has fulfilled its mission, they are passing their findings and lessons learned, along with recommendations, to other groups. One of these, the recently established Global Schistosomiasis Alliance, which includes some of the same people involved with SCORE, has taken up the baton to help harmonize the continued fight to end schistosomiasis.
Chromatographic separation of the acetone extracts from the twigs and barks of Artocarpus lakoocha led to the isolation of the one new flavanone, lakoochanone (1), together with eleven known compounds (2-12). Lakoochanone (1) and moracin C (4) exhibited weak antiplasmodial activity against Plasmodium falciparum Dd2 with IC50 values of 36.7 and 33.9 µM, respectively. Moreover, moracin C (4) and sanggenofuran B (5) showed cytotoxic activity against A2780 cell line with the respective IC50 values of 15.0 and 57.1 µM. In addition, cyclocommunin (7) displayed strong antimycobacterial activity against Mycobacterium tuberculosis H37Ra with the minimum inhibitory concentration (MIC) value of 12.3 µM.
Lathosterol oxidase (LSO) catalyzes the formation of the C-5–C-6 double bond in the synthesis of various types of sterols in mammals, fungi, plants, and protozoa. In Leishmania parasites, mutations in LSO or other sterol biosynthetic genes are associated with amphotericin B resistance. To investigate the biological roles of sterol C-5–C-6 desaturation, we generated an LSO-null mutant line (lso−) in Leishmania major, the causative agent for cutaneous leishmaniasis. lso− parasites lacked the ergostane-based sterols commonly found in wild-type L. major and instead accumulated equivalent sterol species without the C-5–C-6 double bond. These mutant parasites were replicative in culture and displayed heightened resistance to amphotericin B. However, they survived poorly after reaching the maximal density and were highly vulnerable to the membrane-disrupting detergent Triton X-100. In addition, lso− mutants showed defects in regulating intracellular pH and were hypersensitive to acidic conditions. They also had potential alterations in the carbohydrate composition of lipophosphoglycan, a membrane-bound virulence factor in Leishmania. All these defects in lso− were corrected upon the restoration of LSO expression. Together, these findings suggest that the C-5–C-6 double bond is vital for the structure of the sterol core, and while the loss of LSO can lead to amphotericin B resistance, it also makes Leishmania parasites vulnerable to biologically relevant stress.
IMPORTANCE Sterols are essential membrane components in eukaryotes, and sterol synthesis inhibitors can have potent effects against pathogenic fungi and trypanosomatids. Understanding the roles of sterols will facilitate the development of new drugs and counter drug resistance. LSO is required for the formation of the C-5–C-6 double bond in the sterol core structure in mammals, fungi, protozoans, plants, and algae. Functions of this C-5–C-6 double bond are not well understood. In this study, we generated and characterized a lathosterol oxidase-null mutant in Leishmania major. Our data suggest that LSO is vital for the structure and membrane-stabilizing functions of leishmanial sterols. In addition, our results imply that while mutations in lathosterol oxidase can confer resistance to amphotericin B, an important antifungal and antiprotozoal agent, the alteration in sterol structure leads to significant defects in stress response that could be exploited for drug development.
Yu Ning, Cheryl Frankfater, Fong-Fu Hsu, Rodrigo P Soares, Camila A Cardoso, Paula M Nogueira, Noelia Marina Lander, Roberto Docampo, Kai Zhang. mSphere. 2020 Jul 1;5(4):e00380-20. doi: 10.1128/mSphere.00380-20.
Myocytes express low levels of MHC class I (MHC I), perhaps influencing the ability of CD8+ T cells to efficiently detect and destroy pathogens that invade muscle. Trypanosoma cruzi infects many cell types but preferentially persists in muscle, and we asked if this tissue-dependent persistence was linked to MHC expression. Inducible enhancement of skeletal muscle MHC I in mice during the first 20 d of T. cruzi infection resulted in enhanced CD8-dependent reduction of parasite load. However, continued overexpression of MHC I beyond 30 d ultimately led to a collapse of systemic parasite control associated with immune exhaustion, which was reversible in part by blocking PD-1:PD-L1 interactions. These studies demonstrate a surprisingly strong and systemically dominant effect of skeletal muscle MHC expression on maintaining T cell function and pathogen control and argue that the normally low MHC I expression in skeletal muscle is host protective by allowing for pathogen control while preventing immune exhaustion.
The Antarctic sponge Dendrilla antarctica is rich in defensive terpenoids with promising antimicrobial potential. Investigation of this demosponge has resulted in the generation of a small chemical library containing diterpenoid secondary metabolites with bioactivity in an infectious disease screening campaign focused on Leishmania donovani, Plasmodium falciparum, and methicillin-resistant Staphylococcus aureus (MRSA) biofilm. In total, eleven natural products were isolated, including three new compounds designated dendrillins B-D (10–12). Chemical modification of abundant natural products led to three semisynthetic derivatives (13–15), which were also screened. Several compounds showed potency against the leishmaniasis parasite, with the natural products tetrahydroaplysulphurin-1 (4) and dendrillin B (10), as well as the semisynthetic triol 15, displaying single-digit micromolar activity and low mammalian cytotoxicity. Triol 15 displayed the best profile against the liver-stage malaria parasites, while membranolide (5) and dendrillin C (11) were strong hits against MRSA biofilm cultures.
Alexandre Bory, Andrew J Shilling, Jessie Allen, Ala Azhari, Alison Roth, Lindsey N Shaw, Dennis E Kyle, John H Adams, Charles D Amsler, James B McClintock, Bill J Baker. Mar Drugs. 2020 Jun 23;18(6):E327. doi: 10.3390/md18060327.
Introduction. In a pilot study, we showed that intermittent administration of benznidazole in chronic Chagas disease patients resulted in a low rate of treatment suspension and therapeutic failure, as assessed by qPCR at the end of treatment. Herein, a three-year post-treatment follow-up study of the same cohort of patients is presented.
Methods. The treatment scheme consisted of 12 doses of benznidazole at 5 mg/kg/day in two daily doses every 5 days. Parasite load, T. cruzi-specific antibodies and serum chemokine levels were measured prior to treatment and after a median follow-up of 36 months post-treatment by kDNA and SatDNA qPCR methods, conventional serological techniques and a Luminex-based assay with recombinant T. cruzi protein, and a cytometric bead array, respectively.
Results. At the end of follow-up, 14 of 17 (82%) patients had negative qPCR findings, whereas three of 17 (18%) had detectable nonquantifiable findings by at least one of the qPCR techniques. A decline in parasite-specific antibodies at 12 months post-treatment was confirmed by conventional serological tests and the Luminex assays. Monocyte chemoattractant protein-1 (MCP-1) levels increased after treatment, whereas monokine induced by gamma interferon (MIG) levels decreased. New post-treatment electrocardiographic abnormalities were observed in only one patient who had cardiomyopathy prior to treatment.
Conclusions. Altogether, these data strengthen our previous findings by showing that the intermittent administration of benznidazole results in a low rate of treatment suspension, with comparable treatment efficacy to that of a daily dose of 5mg/kg for 60 days.
María Gabriela Álvarez, Juan Carlos Ramírez, Graciela Bertocchi, Marisa Fernández, Yolanda Hernández, Bruno Lococo, Constanza Lopez-Albizu, Alejandro Schijman, Carolina Cura, Marcelo Abril, Susana Laucella, Rick L Tarleton, María Ailen Natale, Melisa Castro Eiro, Sergio Sosa-Estani, Rodolfo Viotti. Antimicrob Agents Chemother. 2020 Jun 22;AAC.00439-20. doi: 10.1128/AAC.00439-20.
The sciaenid Spotted Seatrout (Cynoscion nebulosus) are infected by blood flukes (Cardicola spp.). A 2 year survey in estuaries of South Carolina, USA, showed that adult flukes and granulomas occurred throughout the year but their prevalence was highest in summer (61% and 84%, respectively), indicating an unusually high level of infection for wild fish. Granulomas remained after adult flukes could no longer be found. PCR-Restriction Fragment Length Polymorphism (RFLP) of a subsample of specimens allowed identification of Cardicola laruei as the only species infecting these seatrout during the period of study. Mean intensity of infection by flukes was higher in female seatrout, suggesting endocrine and/or immune system involvement. The prevalence of granulomas declined sharply in winter, indicating possible mortality of infected seatrout as this species is known to be cold-sensitive. Granulomas were studied using histology, immunohistochemistry, and transmission electron microscopy. Eggs were encapsulated by an inner core of dark epithelioid cells, and an outer core of large epithelioid cells undergoing epithelialization. Fibrosis was observed around granulomas and some granulomas detached from the surrounding damaged myocardium. Numerous inflammatory cells appeared mobilized around granulomas and pathology could be severe, in some cases showing grossly visible blister-like extrusions scattered in the damaged epicardium. At the gross level, some granulomas possessing eggs with live miracidia were observed at the surface of the epicardium. These findings suggest that granulomas carrying both dead and live eggs can clear the fish heart by host-mediated transport through the myocardium, as is known to occur in related human Schistosoma infections.
Eric J. McElroy, Barbara Nowak, Kristina M. Hill-Spanik, Willard O. Granath, Vincent A. Connors, Jim Driver, C. Jonathan Tucker, Dennis E. Kyle, Isaurede Buron. Int J Parasitol. 2020 Jun 19;S0020-7519(20)30148-X. doi: 10.1016/j.ijpara.2020.03.016.
We conducted maximum dose bioassays of insecticide for the control of diamondback moth (DBM), Plutella xylostella (Linnaeus), in cole crops, from 2016 to 2019 at several commercial locations in Georgia and Florida. The nominal maximum dose was defined as the highest labeled rate of an insecticide at the beginning of the survey in the equivalent of 935 liters/ha dilution. The results indicated low insecticide efficacy for high labeled rates of the following insecticides by common name (Insecticide Resistance Action Committee group number in parentheses). Our 4-yr survey identified very low levels of DBM larval control (<47%) by lambda-cyhalothrin (3), methoxyfenozide (18), pyriproxyfen (7C), novaluron (15), bifenthrin (3), chlorantraniliprole (28), indoxacarb (22A), and methomyl (1A). The best products for DBM control (>74%) listed in decreasing average levels of efficacy were naled (1B), cyclaniliprole (28), tolfenpyrad (21A), emamectin benzoate (6), and cyantraniliprole (28). Intermediate levels of control (61-71%) were obtained with Bacillus thuringiensis subspecies aizawai (11A), Bacillus thuringiensis, subsp. kurstaki, strain ABTS-351 (11A), and spinetoram (5). This rapid bioassay provided the grower with a ranking of insecticide efficacy for the control the DBM population for that farm site. These data allowed growers to make an informed decision on control quickly and plan for resistance management rotations for DBM that season.