Parasites & Vectors最新文献

Lymphatic filariasis (LF) is a debilitating and stigmatizing disease. In Brazil, the disease has been the target of control and elimination strategies for more than 25 years. Recently, the country received the certificate of elimination of LF as a public health problem. In this post-elimination moment, the question arises: what now? Given the possibility of emergence and reemergence of the disease, it is important that epidemiological surveillance measures are reviewed and applied effectively.

Background: The mitochondrion is proposed as an ideal target organelle for the control of apicomplexan parasites, whose integrity depends on well-controlled protein import, folding, and turnover. The ubiquitin-like domain-containing C-terminal domain phosphatase 1 (UBLCP1) was found to be associated with the mitochondrial integrity in Toxoplasma gondii. However, little is known about the roles and mechanisms of UBLCP1 in this apicomplexan parasite.

Methods: The subcellular localization of UBLCP1 in the tachyzoites of T. gondii was determined by an indirect immunofluorescence assay. The roles of UBLCP1 in the growth, cell cycle, and division of T. gondii were assessed by knocking out this molecule in the tachyzoites. Comparative phosphoproteomics between the UBLCP1-deficient and wild-type tachyzoites were performed to understand the roles of UBLCP1 in T. gondii. The virulence of UBLCP1-deficient tachyzoites of T. gondii was tested in mice.

Results: UBLCP1 is expressed in the nucleus and cytoplasm of T. gondii tachyzoites. Tachyzoites lacking UBLCP1 exhibit collapsed mitochondrion, decreased mitochondrial membrane potential, and compromised growth and proliferation in vitro. Proteins involved in protein turnover and intracellular trafficking have been found differentially phosphorylated in the UBLCP1-deficient tachyzoites compared with the control. Deletion of UBLCP1 also shows that this phosphatase is essential for the propagation and virulence of T. gondii tachyzoites. Mice immunized with UBLCP1-deficient T. gondii tachyzoites survived challenges with the virulent PRU or VEG strain.

Conclusions: UBLCP1 is required for the mitochondrial integrity and essential in the lytic cycle (e.g., host cell invasion and parasite replication) in vitro and the pathogenicity of this parasite in vivo. UBLCP1 is a candidate target for a vaccine or a drug for toxoplasmosis in animals.

Background: Asymptomatic infections by Anaplasma spp. and the basis of the immune response during these infections have not yet been established. This study investigated the inflammatory cytokine responses during Anaplasma spp. infection in school children and the effect of co-infection with Plasmodium spp. and helminths.

Methods: Blood and stool samples were taken from children aged 5 to 17 years. Parasitological diagnosis was carried out by RDT and microscopy, while microscopy and PCR were used to diagnose infection by Anaplasma spp. Plasma was used for cytokine assays using the ELISA technique.

Results: A total of 219 children were included in the present study, of whom 205 were infected with Anaplasma spp. and 14 were uninfected. Levels of IL-6, IL-22 and TGF-β were lower not only in children mono-infected with Anaplasma spp. but also in those co-infected with Anaplasma spp. and Plasmodium spp., Anaplasma spp. and helminths, and Anaplasma spp., Plasmodium spp. and helminths compared to controls. However, higher levels of IL-6 and IL-22 were observed in children mono-infected with Anaplasma spp. compared to those co-infected with Anaplasma spp. and helminths. The latter group also had lower levels of IL-6, IL-22, TGF-β and IL-10 than children co-infected with Anaplasma spp. and Plasmodium spp. In addition, children co-infected with Anaplasma spp. and helminths had also lower TGF-β and IL-10 levels than children co-infected with Anaplasma spp., Plasmodium spp. and helminths. An increase of IFN-γ and IL-10 were observed in children co-infected with Anaplasma spp. and Plasmodium spp. compared to those mono-infected with Anaplasma spp. Finally, the results showed that febrile children infected with Anaplasma spp. had higher levels of IFN-γ and lower levels of TGF-β than afebrile children.

Conclusions: These results suggest that infection with Anaplasma spp. downregulates cytokines including IL-6, IL-22 and TGF-β and that co-infection with Plasmodium spp. might have a protective effect on the host, while co-infection with helminths might have a negative effect.

Background: We evaluated various membranes for blood-feeding in nine sand fly species from different genera and subgenera. Most of these species are vectors of human-pathogenic Leishmania, whereas Sergentomyia minuta is a herpetophilic sand fly species and a proven vector of Leishmania (Sauroleishmania) tarentolae.

Methods: Female sand flies were offered blood through a range of membranes (chicken, reptilian, and frog skin; synthetic collagen; pig intestine; and duck foot webbing). Two feeding systems (glass feeder, Hemotek) and different blood sources (human, ovine, avian, and reptilian) were used. Feeding trials were conducted under varying thermal and light conditions to determine the optimal parameters.

Results: Among the 4950 female S. minuta tested, only a negligible fraction took a blood meal: 2% of the females fed on avian blood, and 0.2% of the females fed on human blood. In eight other species, the chicken membrane was generally more effective than synthetic membranes or pig intestines. For example, Phlebotomus duboscqi refused synthetic membranes, while Lutzomyia longipalpis and P. perniciosus avoided both synthetic membranes and pig intestines. The most effective membrane was duck foot webbing, with four species feeding more readily through it than through the chicken membrane. Additionally, applying coagulated blood plasma to the outer surface of chicken or synthetic membranes significantly increased feeding rates.

Conclusions: Female S. minuta did not reliably feed on blood through the tested membranes, preventing laboratory infection experiments from confirming their vector competence for human-pathogenic Leishmania. However, for future experimental infections of other sand fly species, duck foot webbing has emerged as an effective membrane, and the application of blood plasma to the exterior of membranes may increase the feeding rates.

Background: Malaria is caused by Plasmodium spp. and is a prevalent parasitic disease worldwide. To evade detection by the immune system, by switching variant gene expression, the malaria parasite continually establishes new patterns displaying a single variant erythrocyte surface antigen. The distinct surface molecules encoded by clonally variant gene families include var, rif, stevor, Pfmc-2tm, and surfins. However, the mechanism behind the exclusive expression of a single member of the variant gene family is still not clear. This study aims to describe the molecular process of variant gene switching from the perspective of the epitranscriptome, specifically by characterizing the role of the Plasmodium falciparum RNA m5C methyltransferase NSUN3.

Methods: A conditional gene knockdown approach was adopted by incorporating the glucosamine-inducible glmS ribozyme sequence into the 3' untranslated region (UTR) of the pfnsun3 gene. A transgenic parasite line PfNSUN3-Ty1-Ribo was generated using CRISPR-Cas9 methods. The knockdown effect in the transgenic parasite was measured by a growth curve assay and western blot analysis. The transcriptome changes influenced by PfNUSN3 knockdown were detected by RNA sequencing (RNA-seq), and the direct RNA transcripts regulated by PfNUSN3 were validated by RNA immunoprecipitation and high-throughput sequencing (RIP-seq).

Results: Growth curve analysis revealed that conditional knockdown of PfNSUN3 interfered with parasite growth. The parasitemia of the PfNSUN3 knockdown line showed a significant decline at the third round of the life cycle compared with the control line. The knockdown of PfNSUN3 altered the global transcriptome. RNA-seq analysis showed that at the ring-stage depletion of PfNSUN3 silenced almost all var genes, as well as the guanine/cytosine (GC)-rich non-coding RNA (ncRNA) ruf6 family. RNA RIP-seq arrays revealed that PfNSUN3 directly interacted with several var genes.

Conclusions: Our findings demonstrate a vital role of PfNSUN3 in the process of the mutually exclusive expression of variant genes, and contribute to a better understanding of the complex mechanism of epigenetic regulation of gene expression in P. falciparum.

Background: Simparica Trio^® (Zoetis), an orally administered combination product for dogs containing sarolaner, moxidectin and pyrantel pamoate, was evaluated against Haemaphysalis longicornis, a tick species originally native to Asia but now found on multiple continents, including North America.

Methods: Two groups of eight dogs each were ranked based on pretreatment tick counts and then allocated through randomization to treatment on Day 0 with a single dose of either placebo or Simparica Trio at the minimum label dose of 1.2 mg/kg sarolaner, 24 µg/kg moxidectin and 5 mg/kg pyrantel (as pamoate salt). Dogs were infested with 50 viable adult H. longicornis on Days -2, 5, 12, 19, 26 and 33. Tick counts were conducted for all dogs 48 h after treatment and subsequent re-infestations.

Results: Simparica Trio was 98.9% effective in treating existing H. longicornis infestation when considering live attached (feeding) ticks. Efficacy remained > 98% in preventing re-infestation for at least 35 days, and the geometric mean live attached tick counts for Simparica Trio-treated dogs were significantly lower than for placebo-treated dogs (P < 0.0001) at all timepoints assessed in the study. Dogs treated with Simparica Trio also had significantly lower (P < 0.0001) geometric mean total live (attached and free) tick counts than placebo-treated dogs at all times. No adverse events were reported for any dogs throughout the duration of the study.

Conclusions: A single administration of Simparica Trio at minimum label dose was efficacious in treating and controlling adult H. longicornis in dogs for more than one month.

Background: Visceral leishmaniasis (VL) is the most lethal form of leishmaniasis. In terms of anti-leishmanial vaccines, favorable immune responses are Th1 responses that primarily produce interferon gamma (IFN-γ) and activate macrophages for leishmanicidal effects. The selection of IFN-γ-inducing epitopes in silico may reduce the steps of pre-clinical evaluation and increase the certainty of the better-designed vaccine. Wolbachia surface protein (WSP) derived from Wolbachia bacteria that have been reported to reside in sandflies can trigger TLR2 and TLR4 activation to favor Th1 immune responses, which may serve as a potential adjuvant candidate for the Leishmania vaccine. Therefore, in this study, helper T lymphocyte epitopes that may induce favorable immune responses were identified, and WSP was served as an adjuvant to design a novel multi-epitope vaccine candidate.

Methods: Leishmania hemoglobin receptor (HbR), kinetoplastid membrane protein-11 (KMP-11), glycoprotein of 63 kDa (Gp63), thiol-specific antioxidant antigen (TSA), and sterol 24-c-methyltransferase (SMT) were analyzed by immunoinformatics to screen helper T lymphocyte and cytotoxic T lymphocyte epitopes. The antigenicity, toxicity, allergenicity, and IFN-γ-inducing epitope potential of T epitopes were predicted. The immune simulation was performed to calculate IFN-γ/interleukin (IL)-10 ratios to predict the immune responses induced by the helper T lymphocyte epitopes. Molecular docking and molecular dynamics simulations were carried out to analyze the interactions and stability of the docked complexes. The immune simulation of a multi-epitope vaccine candidate was carried out to predict its immunogenicity.

Results: Some helper T lymphocyte epitopes that were predicted with the potential of inducing Th1 responses and cytotoxic T lymphocyte epitopes were selected to develop a novel multi-epitope vaccine candidate with WSP as an adjuvant. It was found in molecular docking and interaction analysis that TLR2 and TLR4 can recognize WSP, supporting the potential of adjuvant for the Leishmania vaccine. The results from immune simulation demonstrated that the multi-epitope vaccine candidate induced obvious cytokine (IFN-γ, IL-12, and IL-2) secretion and Th1 as well as memory T cell production, similar to that of Leish-111f.

Conclusions: Our vaccine candidate may interact with TLR2 and TLR4 and exhibit good immunogenicity, favoring Leishmania clearance. Our strategy provides a novel multi-epitope vaccine candidate and references for other vaccine developments.

Background: Although the contribution of greenspace to dengue transmission has been reported, the complex role of greenspace morphology remains unclear. We aimed to investigate the relationship between greenspace morphology and dengue in China and to explore the interaction with urbanization and built environment characteristics.

Methods: Dengue data at the township level were collected from five provinces in southern China during 2017-2020. Metrics of greenspace morphology, including percentage, mean area, fragmentation, shape, aggregation, and connectedness, were calculated to quantify its structural characteristics. A negative binomial regression model combined with principal component analysis was conducted to assess the relationship between greenspace morphology and dengue. The modification effects of urbanization and built environment characteristics were evaluated using an interaction term in the model.

Results: Per-interquartile range increase in total percentage, mean area, area-weighted mean shape index, and aggregation index of greenspace were associated with 1.78 (95% confidence interval [CI] 1.57-2.01), 1.14 (1.10-1.20), 1.17 (1.06-1.29), and 1.18 (1.11-1.26) incidence rate ratios of dengue, respectively, while edge density was negatively related to the risk of dengue. In areas with high gross domestic product per capita and population size, the impact of greenspace morphology on the incidence of dengue was more pronounced. By contrast, the influence of greenspace morphology on dengue risk was diminished in regions characterized by higher urban isolation and fragmentation.

Conclusions: Greenspace morphology had a bidirectional impact on the risk of dengue, with urbanization and built environment characteristics exerting diverse modification effects. Our study highlights the importance of a rational greenspace layout to prevent the spread of dengue.

The Pacific Island Health Officers' Association, the World Health Organization, and the Pacific Community co-organized the launch of the Pacific Vector Network (PVN) to address challenges posed by mosquito-borne diseases, including dengue fever, Zika virus disease, chikungunya, malaria, and lymphatic filariasis. The PVN was created as a new initiative under the Pacific Public Health Surveillance Network (PPHSN). This launch was a critical step in the build-up to PVN as a full-service network of PPHSN in the coming years. The Pacific Island Countries and areas (PIC)-led network comprises vector management leadership, officers, and technical partners dedicated to supporting information-sharing to promote evidence-based collective action and innovation. The setup of a Technical Working Body to ensure governance and to steer forward the work of the network was a key deliverable. This manuscript describes the proceedings and discussions of PIC representatives and several regional partners at the inaugural PVN meeting held 5-7 June 2023 in Hawai'i, USA.