Comparative sequence analysis reveals regulation of genes in developing schistosomula of Schistosoma mansoni exposed to host portal serum

Therapeutic and vaccinomic potential of moonlighting proteins for the discovery and design of drugs and vaccines against schistosomiasis

Despite significant and coordinated efforts to combat schistosomiasis, such as providing clean water, sanitation, hygiene, and snail control, these strategies still fall short, as regions previously thought to be disease-free have shown active schistosomiasis transmission. Therefore, it is necessary to implement integrated control methods, emphasizing vaccine development for sustainable control of schistosomiasis. Vaccination has significantly contributed to global healthcare and has been the most economically friendly method for avoiding pathogenic infections. Over the years, different vaccine candidates for schistosomiasis have been investigated with varying degrees of success in clinical trials with many not proceeding past the early clinical phase. Recently, proteins have been mentioned as targets for drug discovery and vaccine development, especially those with multiple functions in schistosomes. Moonlighting proteins are a class of proteins that can perform several functions besides their known functions. This multifunctional property is believed to have been expressed through evolution, where the polypeptide chain gained the ability to perform other tasks without undergoing any structural changes. Since proteins have gained more traction as drug targets, multifunctional proteins have thus become attractive for discovering and developing novel drugs since the drug can target more than one function. Moonlighting proteins are promising drug and vaccine candidates for diseases such as schistosomiasis, since they aid in disease promotion in the human host. This manuscript elucidates vital moonlighting proteins used by schistosomes to drive their life cycle and to ensure their survival in the human host, which can be used to develop anti-schistosomal therapeutics and vaccinomics.

Schistosomiasis: Discovery of New Molecules for Disease Treatment and Vaccine Development

The parasite blood flukes belonging to the genus Schistosoma cause schistosomiasis. Among the Schistosoma species that infect humans, three stand out: Schistosoma japonicum (S. japonicum), which occurs in Asia, mainly in China and the Philippines; Schistosoma haematobium (S. haematobium), which occurs in Africa; and Schistosoma mansoni (S. mansoni), which occurs in Africa and South America and the center of Venezuela (Brazil). Research has shown that these species comprise strains that are resistant to Praziquantel (PZQ), the only drug of choice to fight the disease. Moreover, patients can be reinfected even after being treated with PZQ , and this drug does not act against young forms of the parasite. Therefore, several research groups have focused their studies on new molecules for disease treatment and vaccine development. This chapter will focus on (i) parasite resistance to PZQ , (ii) molecules that are currently being developed and tested as possible drugs against schistosomiasis, and (iii) candidates for vaccine development with a primary focus on clinical trials.

Long non-coding RNA levels can be modulated by 5-azacytidine in Schistosoma mansoni

Schistosoma mansoni is a flatworm that causes schistosomiasis, a neglected tropical disease that affects more than 200 million people worldwide. There is only one drug indicated for treatment, praziquantel, which may lead to parasite resistance emergence. The ribonucleoside analogue 5-azacytidine (5-AzaC) is an epigenetic drug that inhibits S. mansoni oviposition and ovarian development through interference with parasite transcription, translation and stem cell activities. Therefore, studying the downstream pathways affected by 5-AzaC in S. mansoni may contribute to the discovery of new drug targets. Long non-coding RNAs (lncRNAs) are transcripts longer than 200 nucleotides with low or no protein coding potential that have been involved in reproduction, stem cell maintenance and drug resistance. We have recently published a catalog of lncRNAs expressed in S. mansoni life-cycle stages, tissues and single cells. However, it remains largely unknown if lncRNAs are responsive to epigenetic drugs in parasites. Here, we show by RNA-Seq re-analyses that hundreds of lncRNAs are differentially expressed after in vitro 5-AzaC treatment of S. mansoni females, including intergenic, antisense and sense lncRNAs. Many of these lncRNAs belong to co-expression network modules related to male metabolism and are also differentially expressed in unpaired compared with paired females and ovaries. Half of these lncRNAs possess histone marks at their genomic loci, indicating regulation by histone modification. Among a selected set of 8 lncRNAs, half of them were validated by RT-qPCR as differentially expressed in females, and some of them also in males. Interestingly, these lncRNAs are also expressed in other life-cycle stages. This study demonstrates that many lncRNAs potentially involved with S. mansoni reproductive biology are modulated by 5-AzaC and sheds light on the relevance of exploring lncRNAs in response to drug treatments in parasites.

Heat shock protein 70 (Hsp70) in Schistosoma mansoni and its role in decreased adult worm sensitivity to praziquantel

Schistosoma mansoni is the most common species causing schistosomiasis. It has a complex life cycle involving a vertebrate definitive host and a snail intermediate host of the genus Biomphalaria. Each stage encounters a plethora of environmental stresses specially heat stress. Another sort of stress arises from repeated exposure of the parasite to praziquantel (PZQ), the only drug used for treatment, which leads to the development of resistance in the fields and the labs. Heat shock protein 70 (Hsp70) is found in different developmental stages of S. mansoni. It is immunogenic and regulate cercarial invasion besides its chaperone function. In the Biomphalaria/S. mansoni interaction, epigenetic modulations of the Hsp70 gene underscore the susceptibility phenotype of the snail. Hsp70 is up-regulated in adult S. mansoni with decreased sensitivity to PZQ. This could be due to the induction of oxidative and endoplasmic reticulum stress, induction of apoptosis, exposure to the stressful drug pressure and increase influx of calcium ions. Up-regulation of Hsp70 might help the worm to survive the schistosomicidal effect of the drug mainly by dealing with misfolded proteins, inhibition of apoptosis, induction of autophagy, up-regulation of the P-glycoprotein transporter and attenuation of the signalling from G protein coupled receptors.

The role of the liver in the migration of parasites of global significance

Many parasites migrate through different tissues during their life-cycle, possibly with the aim to enhance their fitness. This is true for species of three parasite genera of global importance, Ascaris, Schistosoma and Plasmodium, which cause significant global morbidity and mortality. Interestingly, these parasites all incorporate the liver in their life-cycle. The liver has a special immune status being able to preferentially induce tolerance over immunity. This function may be exploited by parasites to evade host immunity, with Plasmodium spp. in particular using this organ for its multiplication. However, hepatic larval attrition occurs in both ascariasis and schistosomiasis. A better understanding of the molecular mechanisms involved in hepatic infection could be useful in developing novel vaccines and therapies for these parasites.

Effects of the Environment on Developmental Plasticity and Infection Success of Schistosoma Parasites - An Epigenetic Perspective

Evidence of how environmental cues affect the phenotypes of, and compatibility between Schistosoma mansoni and their hosts come from studies in environmental parasitology and research on host diet and chemotherapeutic treatment. Schistosomes deal with a multitude of signals from the water environment as well as cues that come from their hosts, particularly in response to molecules that serve to recognize and destroy them, i.e., those molecules that arise from their hosts' immune systems. These interactions shape, not only the parasite's morphology, metabolism and behavior in the short-term, but also their infection success and development into different stage-specific phenotypes later in their life cycle, through the modification of the parasite's inheritance system. Developmental phenotypic plasticity of S. mansoni is based on epigenetic mechanisms which are also sensitive to environmental cues, but are poorly understood. Here, we argue that specific cues from the environment could lead to changes in parasite development and infectivity, and consequently, environmental signals that come from environmental control measures could be used to influence S. mansoni dynamics and transmission. This approach poses a challenge since epigenetic modification can lead to unexpected and undesired outcomes. However, we suggest that a better understanding of how environmental cues are interpreted by epigenome during schistosome development and host interactions could potentially be applied to control parasite's virulence. We review evidence about the role of environmental cues on the phenotype of S. mansoni and the compatibility between this parasite and its intermediate and definitive hosts.