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MBio May 2024The merozoite surface protein MSPDBL2 is a polymorphic antigen targeted by acquired immune responses, and normally expressed in only a minority of mature schizonts. The...
UNLABELLED
The merozoite surface protein MSPDBL2 is a polymorphic antigen targeted by acquired immune responses, and normally expressed in only a minority of mature schizonts. The potential relationship of MSPDBL2 to sexual commitment is examined, as variable transcript levels and proportions of MSPDBL2-positive mature schizonts in clinical isolates have previously correlated with levels of many sexual stage parasite gene transcripts, although not with the master regulator . It is demonstrated that conditional overexpression of the gametocyte development protein GDV1, which promotes sexual commitment, also substantially increases the proportion of MSPDBL2-positive schizonts in culture. Conversely, truncation of the gene is shown to prevent any expression of MSPDBL2. However, across diverse cultured lines, the variable proportions of MSPDBL2 positivity in schizonts do not correlate significantly with variable gametocyte conversion rates, indicating it is not involved in sexual commitment. Confirming this, examining a line with endogenous hemagglutinin-tagged AP2-G showed that the individual schizonts expressing MSPDBL2 are mostly different from those expressing AP2-G. Using a selection-linked integration system, modified lines were engineered to express an intact or disrupted version of MSPDBL2, showing the protein is not required for sexual commitment or early gametocyte development. Asexual parasite multiplication rates were also not affected by expression of either intact or disrupted MSPDBL2 in a majority of schizonts. Occurring alongside sexual commitment, the role of the discrete MSPDBL2-positive schizont subpopulation requires further investigation in natural infections where it is under immune selection.
IMPORTANCE
Malaria parasites in the blood are remarkably variable, able to switch antigenic targets so they may survive within humans who have already developed specific immune responses. This is one of the challenges in developing vaccines against malaria. MSPDBL2 is a target of naturally acquired immunity expressed in minority proportions of schizonts, the end stages of each 2-day replication cycle in red blood cells which contain merozoites prepared to invade new red blood cells. Results show that the proportion of schizonts expressing MSPDBL2 is positively controlled by the expression of the regulatory gametocyte development protein GDV1. It was previously known that expression of GDV1 leads to increased expression of AP2-G which causes parasites to switch to sexual development, so a surprising finding here is that MSPDBL2-positive parasites are mostly distinct from those that express AP2-G. This discrete antigenic subpopulation of mostly asexual parasites is regulated alongside sexually committed parasites, potentially enabling survival under stress conditions.
Topics: Plasmodium falciparum; Protozoan Proteins; Antigens, Protozoan; Schizonts; Humans; Malaria, Falciparum; Gene Expression Regulation; Erythrocytes
PubMed: 38530030
DOI: 10.1128/mbio.03140-23 -
EMBO Molecular Medicine Apr 2024Vaccination with infectious Plasmodium falciparum (Pf) sporozoites (SPZ) administered with antimalarial drugs (PfSPZ-CVac), confers superior sterilizing protection...
Vaccination with infectious Plasmodium falciparum (Pf) sporozoites (SPZ) administered with antimalarial drugs (PfSPZ-CVac), confers superior sterilizing protection against infection when compared to vaccination with replication-deficient, radiation-attenuated PfSPZ. However, the requirement for drug administration constitutes a major limitation for PfSPZ-CVac. To obviate this limitation, we generated late liver stage-arresting replication competent (LARC) parasites by deletion of the Mei2 and LINUP genes (mei2/linup or LARC2). We show that Plasmodium yoelii (Py) LARC2 sporozoites did not cause breakthrough blood stage infections and engendered durable sterilizing immunity against various infectious sporozoite challenges in diverse strains of mice. We next genetically engineered a PfLARC2 parasite strain that was devoid of extraneous DNA and produced cryopreserved PfSPZ-LARC2. PfSPZ-LARC2 liver stages replicated robustly in liver-humanized mice but displayed severe defects in late liver stage differentiation and did not form liver stage merozoites. This resulted in complete abrogation of parasite transition to viable blood stage infection. Therefore, PfSPZ-LARC2 is the next-generation vaccine strain expected to unite the safety profile of radiation-attenuated PfSPZ with the superior protective efficacy of PfSPZ-CVac.
Topics: Animals; Mice; Plasmodium falciparum; Malaria, Falciparum; Parasites; Gene Deletion; Malaria Vaccines; Vaccines, Attenuated; Sporozoites
PubMed: 38514791
DOI: 10.1038/s44321-024-00057-7 -
The Lancet. Microbe Jun 2024
Topics: Humans; Malaria Vaccines; Africa; Malaria; Vaccination; Infant
PubMed: 38513677
DOI: 10.1016/S2666-5247(24)00073-9 -
MBio Apr 2024Apicomplexa parasites cause major diseases such as toxoplasmosis and malaria that have major health and economic burdens. These unicellular pathogens are obligate...
The acyl-CoA synthetase ACS1 allows neutral lipid metabolism and extracellular motility in through relocation via its peroxisomal targeting sequence (PTS) under low nutrient conditions.
Apicomplexa parasites cause major diseases such as toxoplasmosis and malaria that have major health and economic burdens. These unicellular pathogens are obligate intracellular parasites that heavily depend on lipid metabolism for the survival within their hosts. Their lipid synthesis relies on an essential combination of fatty acids (FAs) obtained from both synthesis and scavenging from the host. The constant flux of scavenged FA needs to be channeled toward parasite lipid storage, and these FA storages are timely mobilized during parasite division. In eukaryotes, the utilization of FA relies on their obligate metabolic activation mediated by acyl-co-enzyme A (CoA) synthases (ACSs), which catalyze the thioesterification of FA to a CoA. Besides the essential functions of FA for parasite survival, the presence and roles of ACS are yet to be determined in Apicomplexa. Here, we identified ACS1 as a cytosolic ACS that is involved in FA mobilization in the parasite specifically during low host nutrient conditions, especially in extracellular stages where it adopts a different localization. Heterologous complementation of yeast ACS mutants confirmed ACS1 as being an Acyl-CoA synthetase of the bubble gum family that is most likely involved in β-oxidation processes. We further demonstrate that ACS1 is critical for gliding motility of extracellular parasite facing low nutrient conditions, by relocating to peroxisomal-like area.IMPORTANCE, causing human toxoplasmosis, is an Apicomplexa parasite and model within this phylum that hosts major infectious agents, such as spp., responsible for malaria. The diseases caused by apicomplexans are responsible for major social and economic burdens affecting hundreds of millions of people, like toxoplasmosis chronically present in about one-third of the world's population. Lack of efficient vaccines, rapid emergence of resistance to existing treatments, and toxic side effects of current treatments all argue for the urgent need to develop new therapeutic tools to combat these diseases. Understanding the key metabolic pathways sustaining host-intracellular parasite interactions is pivotal to develop new efficient ways to kill these parasites. Current consensus supports parasite lipid synthesis and trafficking as pertinent target for novel treatments. Many processes of this essential lipid metabolism in the parasite are not fully understood. The capacity for the parasites to sense and metabolically adapt to the host physiological conditions has only recently been unraveled. Our results clearly indicate the role of acyl-co-enzyme A (CoA) synthetases for the essential metabolic activation of fatty acid (FA) used to maintain parasite propagation and survival. The significance of our research is (i) the identification of seven of these enzymes that localize at different cellular areas in parasites; (ii) using lipidomic approaches, we show that ACS1 mobilizes FA under low host nutrient content; (iii) yeast complementation showed that acyl-CoA synthase 1 (ACS1) is an ACS that is likely involved in peroxisomal β-oxidation; (iv) the importance of the peroxisomal targeting sequence for correct localization of ACS1 to a peroxisomal-like compartment in extracellular parasites; and lastly, (v) that ACS1 has a crucial role in energy production and extracellular parasite motility.
Topics: Humans; Toxoplasma; Lipid Metabolism; Saccharomyces cerevisiae; Toxoplasmosis; Fatty Acids; Nutrients; Malaria; Protozoan Proteins
PubMed: 38501871
DOI: 10.1128/mbio.00427-24 -
Frontiers in Cellular and Infection... 2024Chagas' is a neglected disease caused by the eukaryotic kinetoplastid parasite, Currently, approximately 8 million people are infected worldwide, most of whom are in...
Chagas' is a neglected disease caused by the eukaryotic kinetoplastid parasite, Currently, approximately 8 million people are infected worldwide, most of whom are in the chronic phase of the disease, which involves cardiac, digestive, or neurologic manifestations. There is an urgent need for a vaccine because treatments are only effective in the initial phase of infection, which is generally underdiagnosed. The selection and combination of antigens, adjuvants, and delivery platforms for vaccine formulations should be designed to trigger mixed humoral and cellular immune responses, considering that has a complex life cycle with both intracellular and bloodstream circulating parasite stages in vertebrate hosts. Here, we report the effectiveness of vaccination with a -specific protein family (TcTASV), employing both recombinant proteins with aluminum hydroxide and a recombinant baculovirus displaying a TcTASV antigen at the capsid. Vaccination stimulated immunological responses by producing lytic antibodies and antigen-specific CD4+ and CD8+ IFNɣ secreting lymphocytes. More than 90% of vaccinated animals survived after lethal challenges with , whereas all control mice died before 30 days post-infection. Vaccination also induced a strong decrease in chronic tissue parasitism and generated immunological memory that allowed vaccinated and infected animals to control both the reactivation of the infection after immunosuppression and a second challenge with . Interestingly, inoculation with baculovirus partially protected the mice against . In brief, we demonstrated for the first time that the combination of the baculovirus platform and the TcTASV family provides effective protection against i, which is a promising vaccine for Chagas disease.
Topics: Humans; Animals; Mice; Parasites; Baculoviridae; Antigens, Protozoan; Chagas Disease; Trypanosoma cruzi; Vaccination; Vaccines; Protozoan Vaccines
PubMed: 38481660
DOI: 10.3389/fcimb.2024.1297321 -
Microbial Biotechnology Mar 2024Chicken coccidiosis is an intestinal disease caused by the parasite Eimeria, which severely damages the growth of chickens and causes significant economic losses in the...
Chicken coccidiosis is an intestinal disease caused by the parasite Eimeria, which severely damages the growth of chickens and causes significant economic losses in the poultry industry. Improvement of the immune protective effect of antigens to develop high efficiency subunit vaccines is one of the hotspots in coccidiosis research. Sporozoite-specific surface antigen 1 (SAG1) of Eimeria tenella (E. tenella) is a well-known protective antigen and is one of the main target antigens for the development of subunit, DNA and vector vaccines. However, the production and immunoprotective effects of SAG1 need to be further improved. Here, we report that both SAG1 from E. tenella and its fusion protein with the xylanase XynCDBFV-SAG1 are recombinant expressed and produced in Pichia pastoris (P. pastoris). The substantial expression quantity of fusion protein XynCDBFV-SAG1 is achieved through fermentation in a 15-L bioreactor, reaching up to about 2 g/L. Moreover, chickens immunized with the fusion protein induced higher protective immunity as evidenced by a significant reduction in the shedding of oocysts after E. tenella challenge infection compared with immunized with recombinant SAG1. Our results indicate that the xylanase enhances the immunogenicity of subunit antigens and has the potential for developing novel molecular adjuvants. The high expression level of fusion protein XynCDBFV-SAG1 in P. pastoris holds promise for the development of effective recombinant anti-coccidial subunit vaccine.
Topics: Animals; Eimeria tenella; Chickens; Antigens, Surface; Antigens, Protozoan; Coccidiosis; Recombinant Proteins; Vaccines, Synthetic; Saccharomycetales
PubMed: 38478376
DOI: 10.1111/1751-7915.14447 -
BMC Medicine Mar 2024Ensuring that malaria vaccines deliver maximum public health impact is non-trivial. Drawing on current research, this article examines hurdles that malaria immunization...
Ensuring that malaria vaccines deliver maximum public health impact is non-trivial. Drawing on current research, this article examines hurdles that malaria immunization may face to reach high-risk children and explores the policy implications. The analysis finds health system related risks with the potential to reduce the ability of malaria vaccines to provide equitable protection. Deployment of effective frameworks to tackle these risks so as to strengthen within-country equity and progress tracking should be entangled with the deployment of the vaccines. To capture more comprehensively disease- and system-related risks to child health and survival, vaccine allocation criteria should expand their data and indicator breadth. Factoring molecular, clinical, and epidemiological features of antimalarial drug resistance into vaccine allocation frameworks is critical to effectively reflect current and future risks to malaria control interventions. It is proposed that approximately 6-15 children would need to be vaccinated to prevent a malaria adverse outcome. Vaccine purchasing and delivery costs may overwhelm endemic countries' health systems given the sizeable number needed to vaccinate, the population of at-risk children, and limited government financing of the health sector. Innovations in health financing are pivotal to ensuring the cost-effectiveness and sustainability of immunization programs aiming to attain and maintain universal and equitable protection.
Topics: Child; Humans; Infant; Malaria Vaccines; Malaria, Falciparum; Malaria; Immunization; Vaccination
PubMed: 38475775
DOI: 10.1186/s12916-024-03321-2 -
Poultry Science May 2024This study compared 2 herbal anticoccidiosis drugs (water-soluble and feed-additive drugs) with monensin coccidiostat, toltrazuril (TTZ, anticoccidiosis drug), and... (Comparative Study)
Comparative Study
This study compared 2 herbal anticoccidiosis drugs (water-soluble and feed-additive drugs) with monensin coccidiostat, toltrazuril (TTZ, anticoccidiosis drug), and Livacox Q (anticoccidiosis vaccine) in terms of their effects on the prevention and treatment of coccidiosis in broilers. In this study, 280 Ross 308 broiler chickens (a mix of both genders) were used in a completely randomized design with 7 treatments and 5 replications each including 8 chickens per replicate. On d 21 of rearing, all experimental groups, except for the negative control group (NC), were challenged with a mixed suspension of common strains of Eimeria, and the intended indices were assessed, including performance indices, number of oocysts per gram (OPG) of feces, intestinal injuries, and the total number of intestinal bacteria. In addition, the NC and the group receiving the monensin had greater body weight gain (BWG) (P < 0.05). At the end of week 6, the monensin group had the highest feed intake (FI), while the water soluble medicine treatment resulted in the lowest feed intake (P < 0.05). Regarding the lesion scores on day 28, the highest and lowest rates of jejunal injuries were observed in the positive control group (PC), the monensin and vaccine group respectively. The rate of oocysts excretion (oocysts per gram of feces = OPG) on different days was higher in the PC group, and the use of monensin could further reduce excretion compared to the other groups (P > 0.05). Based on a comparison of the population of lactic acid bacteria between the NC and both medicinal plant treated groups, the use of these products could increase the population of these types of bacteria. Moreover, the population of Escherichia coli was less considerable in the NC and herbal powder groups (P < 0.05). Overall, similar to commercial medicines, the herbal medicines used in this project can be effective in the prevention and treatment of coccidiosis and can improve profitability in broiler rearing centers by improving intestinal health.
Topics: Animals; Coccidiosis; Chickens; Coccidiostats; Poultry Diseases; Triazines; Animal Feed; Male; Protozoan Vaccines; Eimeria; Female; Diet; Random Allocation; Dietary Supplements
PubMed: 38471232
DOI: 10.1016/j.psj.2024.103596 -
Frontiers in Cellular and Infection... 2024, the most widespread human malaria parasite, and , an emerging that infects humans, are the phylogenetically closest malarial species that infect humans, which may...
, the most widespread human malaria parasite, and , an emerging that infects humans, are the phylogenetically closest malarial species that infect humans, which may induce cross-species reactivity across most co-endemic areas in Southeast Asia. The thrombospondin-related anonymous protein (TRAP) family is indispensable for motility and host cell invasion in the growth and development of parasites. The merozoite-specific TRAP (MTRAP), expressed in blood-stage merozoites, is supposed to be essential for human erythrocyte invasion. We aimed to characterize MTRAPs in blood-stage and parasites and ascertain their cross-species immunoreactivity. Recombinant and MTRAPs of full-length ectodomains were expressed in a mammalian expression system. The MTRAP-specific immunoglobulin G, obtained from immune animals, was used in an immunofluorescence assay for subcellular localization and invasion inhibitory activity in blood-stage parasites was determined. The cross-species humoral immune responses were analyzed in the sera of patients with or infections. The MTRAPs of (PvMTRAP) and (PkMTRAP) were localized on the rhoptry body of merozoites in blood-stage parasites. Both anti-PvMTRAP and anti-PkMTRAP antibodies inhibited erythrocyte invasion of blood-stage parasites. The humoral immune response to PvMTRAP showed high immunogenicity, longevity, and cross-species immunoreactivity with . MTRAPs are promising candidates for development of vaccines and therapeutics against vivax and knowlesi malaria.
Topics: Animals; Humans; Plasmodium vivax; Parasites; Merozoites; Thrombospondins; Plasmodium; Malaria; Malaria, Vivax; Protozoan Proteins; Mammals
PubMed: 38465236
DOI: 10.3389/fcimb.2024.1354880 -
Nature Communications Mar 2024Malaria-causing Plasmodium parasites first replicate as liver stages (LS), which then seed symptomatic blood stage (BS) infection. Emerging evidence suggests that these...
Malaria-causing Plasmodium parasites first replicate as liver stages (LS), which then seed symptomatic blood stage (BS) infection. Emerging evidence suggests that these stages impact each other via perturbation of host responses, and this influences the outcome of natural infection. We sought to understand whether the parasite stage interplay would affect live-attenuated whole parasite vaccination, since the efficacy of whole parasite vaccines strongly correlates with their extend of development in the liver. We thus investigated the impact of BS infection on LS development of genetically attenuated and wildtype parasites in female rodent malaria models and observed that for both, LS infection suffered severe suppression during concurrent BS infection. Strikingly and in contrast to previously published studies, we find that the BS-induced iron-regulating hormone hepcidin is not mediating suppression of LS development. Instead, we demonstrate that BS-induced host interferons are the main mediators of LS developmental suppression. The type of interferon involved depended on the BS-causing parasite species. Our study provides important mechanistic insights into the BS-mediated suppression of LS development. This has direct implications for understanding the outcomes of live-attenuated Plasmodium parasite vaccination in malaria-endemic areas and might impact the epidemiology of natural malaria infection.
Topics: Female; Humans; Malaria Vaccines; Hepcidins; Malaria; Plasmodium; Liver; Liver Diseases
PubMed: 38453916
DOI: 10.1038/s41467-024-46270-3