Role In Parasite Survival Research Articles

Interaction of Chicken Heterophils and Eimeria tenella Results in Different Phenotypes of Heterophil Extracellular Traps (HETs)

Chicken coccidiosis causes annual losses exceeding GBP 10 billion globally. The most pathogenic species for domestic fowls including Eimeria tenella, E. acervulina, and E. maxima, can lead to gastrointestinal issues ranging from mild to fatal. In this study, stages of E. tenella and freshly isolated chicken heterophils were co-cultured for 180 min. These interactions were analyzed using live 3D holotomographic and confocal microscopy. We observed that E. tenella stages were entrapped by heterophils and heterophil extracellular traps (HETs). Notably, different HET phenotypes, specifically sprHETs and aggHETs, were induced regardless of the stage. Furthermore, the quantification of extracellular DNA release from co-cultures of heterophils and sporozoites (ratio 1:1) for 180 min demonstrated a significantly higher release (p = 0.04) compared to negative controls. In conclusion, research on the chicken innate immune system, particularly fowl-derived HETs, remains limited. More detailed investigations are needed, such as exploring the time-dependent triggering of HETs, to establish a standard incubation time for this pathogen defense mechanism. This will enhance our understanding of its role in parasite survival or death during HET confrontation.

Plasmodium falciparum heat shock proteins as antimalarial drug targets: An update.

Global efforts to eradicate malaria are threatened by multiple factors, particularly the emergence of antimalarial drug resistant strains of Plasmodium falciparum. Heat shock proteins (HSPs), particularly P. falciparum HSPs (PfHSPs), represent promising drug targets due to their essential roles in parasite survival and virulence across the various life cycle stages. Despite structural similarities between human and malarial HSPs posing challenges, there is substantial evidence for subtle differences that could be exploited for selective drug targeting. This review provides an update on the potential of targeting various PfHSP families (particularly PfHSP40, PfHSP70, and PfHSP90) and their interactions within PfHSP complexes as a strategy to develop new antimalarial drugs. In addition, the need for a deeper understanding of the role of HSP complexes at the host-parasite interface is highlighted, especially heterologous partnerships between human and malarial HSPs, as this opens novel opportunities for targeting protein-protein interactions crucial for malaria parasite survival and pathogenesis.

Real-time measurements of ATP dynamics via ATeams in Plasmodium falciparum reveal drug-class-specific response patterns.

Malaria tropica, caused by the parasite Plasmodium falciparum (P. falciparum), remains one of the greatest public health burdens for humankind. Due to its pivotal role in parasite survival, the energy metabolism of P. falciparum is an interesting target for drug design. To this end, analysis of the central metabolite adenosine triphosphate (ATP) is of great interest. So far, only cell-disruptive or intensiometric ATP assays have been available in this system, with various drawbacks for mechanistic interpretation and partly inconsistent results. To address this, we have established fluorescent probes, based on Förster resonance energy transfer (FRET) and known as ATeam, for use in blood-stage parasites. ATeams are capable of measuring MgATP2- levels in a ratiometric manner, thereby facilitating in cellulo measurements of ATP dynamics in real-time using fluorescence microscopy and plate reader detection and overcoming many of the obstacles of established ATP analysis methods. Additionally, we established a superfolder variant of the ratiometric pH sensor pHluorin (sfpHluorin) in P. falciparum to monitor pH homeostasis and control for pH fluctuations, which may affect ATeam measurements. We characterized recombinant ATeam and sfpHluorin protein in vitro and stably integrated the sensors into the genome of the P. falciparum NF54attB cell line. Using these new tools, we found distinct sensor response patterns caused by several different drug classes. Arylamino alcohols increased and redox cyclers decreased ATP; doxycycline caused first-cycle cytosol alkalization; and 4-aminoquinolines caused aberrant proteolysis. Our results open up a completely new perspective on drugs' mode of action, with possible implications for target identification and drug development.

Trypanosoma brucei Invariant Surface Glycoprotein 75 Is an Immunoglobulin Fc Receptor Inhibiting Complement Activation and Antibody-Mediated Cellular Phagocytosis.

Various subspecies of the unicellular parasite Trypanosoma brucei cause sleeping sickness, a neglected tropical disease affecting millions of individuals and domestic animals. Immune evasion mechanisms play a pivotal role in parasite survival within the host and enable the parasite to establish a chronic infection. In particular, the rapid switching of variant surface glycoproteins covering a large proportion of the parasite's surface enables the parasite to avoid clearance by the adaptive immune system of the host. In this article, we present the crystal structure and discover an immune-evasive function of the extracellular region of the T. brucei invariant surface gp75 (ISG75). Structural analysis determined that the ISG75 ectodomain is organized as a globular head domain and a long slender coiled-coil domain. Subsequent ligand screening and binding analysis determined that the head domain of ISG75 confers interaction with the Fc region of all subclasses of human IgG. Importantly, the ISG75-IgG interaction strongly inhibits both activation of the classical complement pathway and Ab-dependent cellular phagocytosis by competing with C1q and host cell FcγR CD32. Our data reveal a novel immune evasion mechanism of T. brucei, with ISG75 able to inactivate the activities of Abs recognizing the parasite surface proteins.

Structural analysis of Plasmodium falciparum ookinete surface antigen Pfs28 relevant for malaria vaccine design

Pfs28 is a Plasmodium falciparum malaria transmission-blocking vaccine candidate that is anchored to the parasite surface through a C-terminal glycosylphosphatidylinositol (GPI) moiety, and plays a role in parasite survival in the mosquito midgut. Pfs28 contains epidermal growth factor (EGF)-like domains and is part of a family of sexual stage malaria proteins that includes the related vaccine antigen Pfs25. The lack of structural definition of Pfs28 and the immune response to this candidate has limited further malaria vaccine development for this antigen. Here, we present the crystal structure of Pfs28, examine its conservation with P. vivax Pvs28, and evaluate the cross-reactivity of Pfs28 to antibodies that recognize Pfs25. Pfs28 is comprised of four EGF-like domains stabilized by ten disulfide bridges with an overall architecture that highly resembles Pfs25. Despite the high sequence and structural similarity between these antigens, no cross reactivity of Pfs28 to anti-Pfs25 monoclonal antibodies could be demonstrated.

Structural Basis of Parasitic HSP90 ATPase Inhibition by Small Molecules.

Protozoan parasites are responsible for several harmful and widespread human diseases that cause high morbidity and mortality. Currently available treatments have serious limitations due to poor efficiency, strong adverse effects, and high cost. Hence, the identification of new targets and the development of specific drug therapies against parasitic diseases are urgent needs. Heat shock protein 90 (HSP90) is an ATP-dependent molecular chaperone that plays a key role in parasite survival during the various differentiation stages, spread over the vector insect and the human host, which they undergo during their life cycle. The N-terminal domain (NTD) of HSP90, containing the main determinants for ATPase activity, represents the most druggable domain for inhibitor targeting. The molecules investigated on parasite HSP90 are mainly developed from known inhibitors of the human counterpart, and they have strong limitations due to selectivity issues, accounting for the high conservation of the ATP-binding site between the parasite and human proteins. The current review highlights the recent structural progress made to support the rational design of new molecules able to effectively block the chaperone activity of parasite HSP90.

Expression of the Fab enzymes (Fab I and Fab Z) from Plasmodium falciparum after exposure to Artemisia afra plant extracts and drugs screening.

The emergence and spread of drug resistance of the malaria parasite to the main treatment emphasize the need to develop new antimalarial drugs. In this context, the fatty acid biosynthesis (FAS_II) pathway of the malaria parasite is one of the ideal targets due to its crucial role in parasite survival. In this study, we report the expression and the affinity binding of Fab_I and Fab_Z after exposure to the parasite with different extracts of the Artemisia afra. The parasites were exposed for 2days to different extracts. Gene expression was done to determine the level of expression of the fab enzymes after treatments. A GCMS was run to determine the different compounds of the plant extracts, followed by a virtual screening between the fab enzymes and the active compounds using Pyrex. The results showed different expression patterns of the Fab enzymes. Fab_I expression was downregulated in the W2 and D6 strains by the ethanolic extract but was increased by Hexane and DCM extracts. A different expression pattern was observed for Fab_Z. It was all upregulated except in the D6 strain when exposed to the ethanolic and hexane extracts. Virtual screening showed an affinity with many compounds. Hits compounds with high binding energy were detected. 11alphaHydroxyprogesterone and Aspidospermidin-17-ol were found to have high binding energy with Fab_I respectively (-10.7kcal/mol; -10.2kcal/mol). Fab_Z shows also high affinity with 11alpha-Hydroxyprogesterone (-10kcal/mol) and Thiourea (-8.4kcal/mol). This study shows the potential of A. afra to be used as a new source of novel antimalarial compounds.

HIV protease inhibitor nelfinavir is a potent drug candidate against echinococcosis by targeting Ddi1-like protein.

SummaryBackgroundAlveolar echinococcosis (AE), which is caused by larval Echinococcus multilocularis, is one of the world's most dangerous neglected diseases. Currently, no fully effective treatments are available to cure this disease.MethodsIn vitro protoscolicidal assay along with in vivo murine models was applied in repurposing drugs against AE. Genome-wide identification and homology-based modeling were used for predicting drug targets. RNAi, enzyme assay, and RNA-Seq analyses were utilized for investigating the roles in parasite survival and validations for the drug target.FindingsWe identified nelfinavir as the most effective HIV protease inhibitor against larval E. multilocularis. Once-daily oral administration of nelfinavir for 28 days resulted in a remarkable reduction in parasite infection in either immune-competent or immunocompromised mice. E. multilocularis DNA damage-inducible 1 protein (EmuDdi1) is predicted as a target candidate for nelfinavir. We proved that EmuDdi1 is essential for parasite survival and protein excretion and acts as a functionally active protease for this helminth. We found nelfinavir is able to inhibit the proteolytic activity of recombinant EmuDdi1 and block the EmuDdi1-related pathways for protein export. With other evidence of drug efficacy comparison, our results suggest that inhibition of EmuDdi1 is a mechanism by which this HIV proteinase inhibitor mediates its antiparasitic action on echinococcosis.InterpretationThis study demonstrates that nelfinavir is a promising candidate for treating echinococcosis. This drug repurposing study proves that the widely prescribed drug for AIDS treatment is potent in combating E. multilocularis infection and thus provides valuable insights into the development of single-drug therapy for highly prevalent co-infection between HIV and helminth diseases.FundingThis work was supported by the National Natural Science Foundation of China (31802179), the Natural Science Foundation of Gansu Province, China (No. 21JR7RA027), and the State Key Laboratory of Veterinary Etiological Biology (No. SKLVEB2021YQRC01).

Structure of the Pf12 and Pf41 heterodimeric complex of Plasmodium falciparum 6-cysteine proteins.

During the different stages of the Plasmodium life cycle, surface-associated proteins establish key interactions with the host and play critical roles in parasite survival. The 6-cysteine (6-cys) protein family is one of the most abundant surface antigens and expressed throughout the Plasmodium falciparum life cycle. This protein family is conserved across Plasmodium species and plays critical roles in parasite transmission, evasion of the host immune response and host cell invasion. Several 6-cys proteins are present on the parasite surface as hetero-complexes but it is not known how two 6-cys proteins interact together. Here, we present a crystal structure of Pf12 bound to Pf41 at 2.85 Å resolution, two P. falciparum proteins usually found on the parasite surface of late schizonts and merozoites. Our structure revealed two critical interfaces required for complex formation with important implications on how different 6-cysteine proteins may interact with each other. Using structure-function analyses, we identified important residues for Pf12-Pf41 complex formation. In addition, we generated 16 nanobodies against Pf12 and Pf41 and showed that several Pf12-specific nanobodies inhibit Pf12-Pf41 complex formation. Using X-ray crystallography, we were able to describe the structural mechanism of an inhibitory nanobody in blocking Pf12-Pf41 complex formation. Future studies using these inhibitory nanobodies will be useful to determine the functional role of these two 6-cys proteins in malaria parasites.

A novel leishmanial copper P-type ATPase plays a vital role in parasite infection and intracellular survival

Copper (Cu) is essential for all life forms; however, in excess, it becomes toxic. Toxic properties of Cu are known to be utilized by host species against various pathogenic invasions. Leishmania, in both free-living and intracellular forms, exhibits appreciable tolerance toward Cu stress. While determining the mechanism of Cu-stress evasion employed by Leishmania, we identified and characterized a hitherto unknown Cu-ATPase in Leishmania major and established its role in parasite survival in host macrophages. This novel L. major Cu-ATPase, LmATP7, exhibits homology with its orthologs at multiple motifs. In promastigotes, LmATP7 primarily localized at the plasma membrane. We also show that LmATP7 exhibits Cu-dependent expression patterns and complements Cu transport in a Cu-ATPase-deficient yeast strain. Promastigotes overexpressing LmATP7 exhibited higher survival upon Cu stress, indicating efficacious Cu export compared with Wt and heterozygous LmATP7 knockout parasites. We further explored macrophage–Leishmania interactions with respect to Cu stress. We found that Leishmania infection triggers upregulation of major mammalian Cu exporter, ATP7A, in macrophages, and trafficking of ATP7A from the trans-Golgi network to endolysosomes in macrophages harboring amastigotes. Simultaneously, in Leishmania, we observed a multifold increase in LmATP7 transcripts as the promastigote becomes established in macrophages and morphs to the amastigote form. Finally, overexpressing LmATP7 in parasites increases amastigote survivability within macrophages, whereas knocking it down reduces survivability drastically. Mice injected in their footpads with an LmATP7-overexpressing strain showed significantly larger lesions and higher amastigote loads as compared with controls and knockouts. These data establish the role of LmATP7 in parasite infectivity and intramacrophagic survivability.

Hypoxic and nitrosative stress conditions modulate expression of myoglobin genes in a carcinogenic hepatobiliary trematode, Clonorchis sinensis.

Despite recent evidence suggesting that adult trematodes require oxygen for the generation of bioenergy and eggshells, information on the molecular mechanism by which the parasites acquire oxygen remains largely elusive. In this study, the structural and expressional features of globin genes identified in Clonorchis sinensis, a carcinogenic trematode parasite that invades the hypoxic biliary tracts of mammalian hosts, were investigated to gain insight into the molecules that enable oxygen metabolism. The number of globin paralogs substantially differed among parasitic platyhelminths, ranging from one to five genes, and the C. sinensis genome encoded at least five globin genes. The expression of these Clonorchis genes, named CsMb (CsMb1—CsMb3), CsNgb, and CsGbX, according to their preferential similarity patterns toward respective globin subfamilies, exponentially increased in the worms coinciding with their sexual maturation, after being downregulated in early juveniles compared to those in metacercariae. The CsMb1 protein was detected throughout the parenchymal region of adult worms as well as in excretory-secretory products, whereas the other proteins were localized exclusively in the sexual organs and intrauterine eggs. Stimuli generated by exogenous oxygen, nitric oxide (NO), and nitrite as well as co-incubation with human cholangiocytes variously affected globin gene expression in live C. sinensis adults. Together with the specific histological distributions, these hypoxia-induced patterns may suggest that oxygen molecules transported by CsMb1 from host environments are provided to cells in the parenchyma and intrauterine eggs/sex organs of the worms for energy metabolism and/or, more importantly, eggshell formation by CsMb1 and CsMb3, respectively. Other globin homologs are likely to perform non-respiratory functions. Based on the responsive expression profile against nitrosative stress, an oxygenated form of secreted CsMb1 is suggested to play a pivotal role in parasite survival by scavenging NO generated by host immune cells via its NO dioxygenase activity.

Trypanosoma brucei Tim50 Plays Critical role in Parasite survival in mammalian hosts

Trypanosoma brucei, the infectious agent for African trypanosomiasis, undergoes various developmental processes during its digenetic life cyclethat includes a major alteration in mitochondrial activities. It is known that changes in mitochondrial functions is critical for the parasite to adapt in different environmental conditions, however, the communication mechanism between this single organelle with the rest of the cell is not clear in T. brucei. Mitochondrial inner membrane protein translocase, TbTim50, have a pair of characteristic DXDX(T/V) phosphatase signature motifs. Here we showed that the recombinant TbTim50, specifically binds with Phosphatidic acid (PA). We have also demonstrated that, TbTim50 possesses a protein phosphatase activity and also able to hydrolyze phosphatidic acid (PA). This is suggesting that TbTim50 likely possesses both protein and lipid phosphatase activities. TbTim50 knockdown (KD) decreased the levels of cardiolipin in comparison to control. Cardiolipin is known to play important roles in various mitochondrial functions. RT-PCR analysis also showed that TbTim50 KD increased expression of multiple genes specific for the stumpy form, a non-dividing differentiated bloodstream form of T. brucei. Importantly, we observed that TbTim50 depleted parasites were unable to establish infection in mice and rats. These results indicates that TbTim50 is essential for overall mitochondrial functions and play a critical role in parasite infectivity in animals.

Targeting sterol alpha-14 demethylase of Leishmania donovani to fight against leishmaniasis.

Leishmaniasis is a neglected tropical disease caused by the protozoan parasite Leishmania. It is endemic in more than 89 different countries worldwide. Sterol alpha-14 demethylase (LdSDM), a sterol biosynthetic pathway enzyme in Leishmania donovani, plays an essential role in parasite survival and proliferation. Here, we used a drug repurposing approach to virtually screen the library of the Food and Drug Administration (FDA)-approved drugs against LdSDM to identify the potential lead-drug against leishmaniasis. Zafirlukast and avodart showed the best binding with LdSDM. Zafirlukast was tested for in vitro antileishmanial assay, but no significant effect on L. donovani promastigotes was observed even at higher concentrations. On the other hand, avodart profoundly inhibited parasite growth at relatively lower concentrations. Further, avodart showed a significant decrease in the number of intra-macrophagic amastigotes. Avodart-induced reactive oxygen species (ROS) in the parasites in a dose-dependent manner. ROS induced by avodart led to the induction of apoptosis-like cell death in the parasites as observed through annexin V/PI staining. Here, for the first time,we reported the antileishmanial activity and its possible mechanism of action of FDA-approved drug, avodart, establishing a nice example of the drug-repurposing approach. Our study suggested the possible use of avodart as an effective antileishmanial agent after further detailed validations.

Predictive Global Models of Cruzain Inhibitors with Large Chemical Coverage.

Chagas disease affects 8–11 million people worldwide, most of them living in Latin America. Moreover, migratory phenomena have spread the infection beyond endemic areas. Efforts for the development of new pharmacological therapies are paramount as the pharmacological profile of the two marketed drugs currently available, nifurtimox and benznidazole, needs to be improved. Cruzain, a parasitic cysteine protease, is one of the most attractive biological targets due to its roles in parasite survival and immune evasion. In this work, we compiled and curated a database of diverse cruzain inhibitors previously reported in the literature. From this data set, quantitative structure–activity relationship (QSAR) models for the prediction of their pIC50 values were generated using k-nearest neighbors and random forest algorithms. Local and global models were calculated and compared. The statistical parameters for internal and external validation indicate a significant predictability, with qloo2 values around 0.66 and 0.61 and external R2 coefficients of 0.725 and 0.766. The applicability domain is quantitatively defined, according to QSAR good practices, using the leverage and similarity methods. The models described in this work are readily available in a Python script for the discovery of novel cruzain inhibitors.

Exploration of Plasmodium vivax merozoite surface proteins 1 and 7 genetic diversity in Brazilian Amazon and Rio de Janeiro Atlantic Forest.

Plasmodium vivax merozoite surface proteins (PvMSP) 1 and 7 are considered vaccine targets. Genetic diversity knowledge is crucial to assess their potential as immunogens and to provide insights about population structure in different epidemiological contexts. Here, we investigate the variability of pvmsp-142, pvmsp-7E, and pvmsp-7F genes in 227 samples from the Brazilian Amazon (BA) and Rio de Janeiro Atlantic Forest (AF). pvmsp-142 has 63 polymorphisms - 57 nonsynonymous - generating a nucleotide diversity of π=0.009 in AF, and π=0.018 in BA. In pvmsp-7E, 134 polymorphisms - 103 nonsynonymous - generate the nucleotide diversity of π=0.027 in AF, and π=0.042 in BA. The pvmsp-7F has only two SNPs - A610G and A1054T -, with nucleotide diversity of π=0.0004 in AF, and π=0.0007 in BA. The haplotype diversity of pvmsp-142, pvmsp-7E, and pvmsp-7F genes is 0.997, 1.00, and 0.649, respectively. None of the pvmsp-142 or pvmsp-7E sequences are identical to the Salvador 1 strain's sequence. Conversely, most of pvmsp-7F sequences (94/48%) are identical to Sal-1. We evaluated eight B-cell epitopes in pvmsp-7E, four of them showed higher nucleotide diversity compared to pvmsp-7E's epitopes. Positive selection was detected in pvmsp-142, pvmsp-7E central region, and pvmsp-7F with Tajima's D. In pvmsp-7E, the significant nucleotide and haplotype diversities with low genetic differentiation, could be indicative of balancing selection. The genetic differentiation of pvmsp-142 (0.315) and pvmsp-7F (0.354) genes between AF and BA regions is significant, which is not the case for pvmsp-7E (0.193). We conclude that pvmsp-142 and pvmsp-7E have great genetic diversity even in AF region, an enclosure area with deficient transmission levels of P. vivax zoonotic malaria. In both Brazilian regions, pvmsp-119, pvmsp-7E, and pvmsp-7F are conserved, most likely due to their roles in parasite survival, and could be considered potential targets for a "blood-stage vaccine".

Identification of Schistosoma japonicum GSK3β interacting partners by yeast two-hybrid screening and its role in parasite survival.

Schistosoma is the causative agent of schistosomiasis, a common infectious disease distributed worldwide. Our previous phosphoproteomic analysis suggested that glycogen synthase kinase 3 (GSK3), a conserved protein kinase in eukaryotes, is likely involved in protein phosphorylation of Schistosoma japonicum. Here, we aimed to identify the interacting partners of S. japonicum GSK3β (SjGSK3β) and to evaluate its role in parasite survival. Toward these ends, we determined the transcription levels of SjGSK3β at different developmental stages and identified its interacting partners of SjGSK3β by screening a yeast two-hybrid S. japonicum cDNA library. We further used RNA interference (RNAi) to inhibit the expression of SjGSK3β in adult worms in vitro and examined the resultant changes in transcription of its putative interacting proteins and in worm viability compared with those of control worms. Reverse transcription-quantitative polymerase chain analysis indicated that SjGSK3β is expressed throughout the life cycle of S. japonicum, with higher expression levels detected in the eggs and relatively higher expression level found in male worms than in female worms. By screening the yeast two-hybrid library, eight proteins were identified as potentially interacting with SjGSK3β including cell division cycle 37 homolog (Cdc37), 14-3-3 protein, tegument antigen (I(H)A), V-ATPase proteolipid subunit, myosin alkali light chain 1, and three proteins without recognized functional domains. In addition, SjGSK3β RNAi reduced the SjGSK3β gene transcript level, leading to a significant decrease in kinase activity, cell viability, and worm survival. Collectively, these findings suggested that SjGSK3β may interact with its partner proteins to influence worm survival by regulating kinase activity.

Regulation of Translation in the Protozoan Parasite Leishmania.

Leishmaniasis represents a serious health problem worldwide and drug resistance is a growing concern. Leishmania parasites use unusual mechanisms to control their gene expression. In contrast to many other species, they do not have transcriptional regulation. The lack of transcriptional control is mainly compensated by post-transcriptional mechanisms, including tight translational control and regulation of mRNA stability/translatability by RNA-binding proteins. Modulation of translation plays a major role in parasite survival and adaptation to dramatically different environments during change of host; however, our knowledge of fine molecular mechanisms of translation in Leishmania remains limited. Here, we review the current progress in our understanding of how changes in the translational machinery promote parasite differentiation during transmission from a sand fly to a mammalian host, and discuss how translational reprogramming can contribute to the development of drug resistance.

Structural, molecular, functional and immunological characterization of Wuchereria bancrofti-galectin

Galectins regulate growth and differentiation of immune cells and inflammation through their carbohydrate-binding function in humans, while also play a role in parasite survival. This study focused on the galectin of lymphatic filarial parasite Wuchereria bancrofti (Wb-Gal). The multiple sequence alignment with other galectins showed that the Wb-Gal belonged to galactoside binding lectin family, particularly tandem repeat type galectin-9. A homology model of Wb-Gal was developed in the I-TASser server using high similarity 3D structures with a quality score of 89.5. Molecular docking and dynamics studies revealed that the CCRD and NCRD of Wb-Gal bind with galactose and lactose. Further, Wb-Gal was cloned into the pET28 vector, expressed in E. coli Rosetta strain and purified by affinity chromatography. In the hemagglutination assays, the rWb-Gal bound to lactose, galactose, and glucose. Indirect Enzyme-Linked Immunosorbent Assay (ELISA) using different clinical filarial sera showed that the IgG and IgM response was against Wb-Gal x very high in all filarial clinical groups, whereas the IgA and IgG2 response was minimum to negligible. There was an enhanced response of IgG1 and IgG4 antibodies in Microfilaremics (MF) cases compared to Chronic Pathology (CP) and Endemic Normal (EN) individuals. Interestingly, the IgE response was comparatively higher in EN than MF and CP. These studies show that Wb-Gal is a member of the lectin family of proteins binding to different carbohydrates and may have an important role in the pathophysiology of filarial infection which needs to be investigated in greater detail.

Antigenic properties of dense granule antigen 12 protein using bioinformatics tools in order to improve vaccine design against Toxoplasma gondii.

PurposeToxoplasma gondii is an opportunistic parasite infecting all warm-blooded animals including humans. The dense granule antigens (GRAs) play an important role in parasite survival and virulence and in forming the parasitophorous vacuole. Identification of protein characteristics increases our knowledge about them and leads to develop the vaccine and diagnostic studies.Materials and MethodsThis paper gave a comprehensive definition of the important aspects of GRA12 protein, including physico-chemical features, a transmembrane domain, subcellular position, secondary and tertiary structure, potential epitopes of B-cells and T-cells, and other important features of this protein using different and reliable bioinformatics methods to determine potential epitopes for designing of a high-efficient vaccine.ResultsThe findings showed that GRA12 protein had 53 potential post-translational modification sites. Also, only one transmembrane domain was recognized for this protein. The secondary structure of GRA12 protein comprises 35.55% alpha-helix, 19.50% extended strand, and 44.95% random coil. Moreover, several potential B- and T-cell epitopes were identified for GRA12. Based on the results of the Ramachandran plot, 79.26% of amino acid residues were located in favored, 11.85% in allowed and 8.89% in outlier regions. Furthermore, the results of the antigenicity and allergenicity assessment noted that GRA12 is immunogenic and non-allergenic.ConclusionThis research provided important basic and conceptual data on GRA12 to develop an effective vaccine against acute and chronic toxoplasmosis for further in vivo investigations. More studies are required on vaccine development using the GRA12 alone or combined with other antigens in the future.

Sm16, A Schistosoma mansoni Immunomodulatory Protein, Fails to Elicit a Protective Immune Response and Does Not Have an Essential Role in Parasite Survival in the Definitive Host.

Sm16 is an immunomodulatory protein that seems to play a key role in the suppression of the cutaneous inflammatory response during Schistosoma mansoni penetration of the skin of definitive hosts. Therefore, Sm16 represents a potential target for protective immune responses induced by vaccination. In this work, we generated the recombinant protein rSm16 and produced polyclonal antibodies against this protein to evaluate its expression during different parasite life-cycle stages and its location on the surface of the parasite. In addition, we analyzed the immune responses elicited by immunization with rSm16 using two different vaccine formulations, as well as its ability to induce protection in Balb/c mice. In order to explore the biological function of Sm16 during the course of experimental infection, RNA interference was also employed. Our results demonstrated that Sm16 is expressed in cercaria and schistosomula and is located in the schistosomula surface. Despite humoral and cellular immune responses triggered by vaccination using rSm16 associated with either Freund's or alum adjuvants, immunized mice presented no reduction in either parasite burden or parasite egg laying. Knockdown of Sm16 gene expression in schistosomula resulted in decreased parasite size in vitro but had no effect on parasite survival or egg production in vivo. Thus, our findings demonstrate that although the vaccine formulations used in this study succeeded in activating immune responses, these failed to promote parasite elimination. Finally, we have shown that Sm16 is not vital for parasite survival in the definitive host and hence may not represent a suitable target for vaccine development.