Acta tropica最新文献

Background: Biting midges (Culicoides spp.) are vectors of diverse microbes such as viruses, bacteria, protozoa, and nematodes that cause diseases in both wild and domestic animals. Despite their ecological significance and role in disease transmission, the composition and underlying mechanisms shaping the gut microbiota of Culicoides remain poorly characterized.

Objectives: This study aimed to investigate the composition and functional profiles of the gut microbiota of adult Culicoides collected from three representative cities spanning tropical, subtropical, and temperate climate zones in China.

Methods: 16S high-throughput sequencing was used to study the microbial composition and function of Culicoides in the three regions. This study further incorporated six environmental factors and seven genetic diversity indices to explore their relationships with the microbial community.

Results: The findings revealed significant variations in the gut microbial composition, dominant species, and diversity of Culicoides across different climate zones. NoTable differences were observed in microbial functions related to insect growth, development, and oxidative stress, with Culicoides from the Sanya zone exhibiting a greater abundance of functions and participating in more signaling processes. Environmental factors and host genetic diversity across different habitats collectively shape the composition of the gut microbiota of Culicoides. Structural equation modeling (SEM) revealed that environmental factors exert predominantly direct selective effects on microbial community assembly, whereas host genetic diversity plays a critical indirect regulatory role. These environment-host-microbiota interactions exhibit significant spatial heterogeneity. In low-latitude regions (Sanya), environmental factors mainly manifest direct filtering effects, whereas in ecotone areas (Ruili), environmental pressures indirectly modulate microbial composition by altering host genetic adaptation.

Conclusions: Our findings revealed that Culicoides gut microbiomes exhibit distinct biogeographical divergence, characterized by environment-driven variations in microbial community structure and functional potential. Host genetic adaptation serves as a key mediator and synergistic modulator of these patterns. This tripartite environment-host-microbiome interaction demonstrates clear dependence on geographic gradient.

Toxoplasma gondii is an obligate intracellular protozoan parasite capable of infecting virtually all warm-blooded animals. The kynurenine pathway (KP), a key route of tryptophan catabolism, serves as a critical immunometabolic checkpoint in cancer, autoimmune disorders, and neurodegenerative diseases. Although the kynurenine monooxygenase (KMO)-derived metabolite quinolinic acid (QUIN) has well-documented antiviral effects, its role in antiparasitic immunity remains unexplored. Here, we identify KMO as a critical mediator of host defense against T. gondii. Upon infection, T. gondii significantly suppresses host KMO expression along with its downstream metabolites, including 3-hydroxykynurenine (3-HK) and QUIN. Functional studies in Vero cells demonstrate that KMO overexpression effectively restricts parasite proliferation, whereas RNA interference (RNAi)-mediated knockdown (KD) of KMO increases parasite burden. Collectively, these findings establish KMO as a non-canonical determinant of anti-T. gondii immunity and nominate KP potentiation as a therapeutic strategy for toxoplasmosis.

Acanthamoeba species are causative agents of the sight-threatening ocular disease, Acanthamoeba keratitis (AK). (‒)-Epicatechin (EC) has been reported to exhibit anti-amoebic activity against laboratory strains of A. castellanii and A. polyphaga, suggesting its potential as an AK drug alternative. However, its efficacy against clinical isolates of Acanthamoeba species and its feasibility as a treatment for AK have not yet been investigated. In this study, we analyzed the anti-amoebic activity of EC against Acanthamoeba clinical isolates and its synergistic effect with chlorhexidine (CHX) to validate its potential in developing or optimizing AK treatment regimes. The anti-amoebic activity of EC against trophozoites and cysts of 10 clinical isolates of Acanthamoeba species was analyzed. The synergistic anti-amoebic effect of EC and CHX was also investigated. EC exhibited anti-amoebic activity against clinical isolates of Acanthamoeba, but showed varying efficacy, with IC₅₀ values ranging from 43.24 to 271.30 µM against trophozoites. EC induced apoptosis-like programmed cell death in the trophozoites of these clinical isolates, and also had partial cysticidal activity. Co-treatment with EC and CHX exhibited prominent in vitro synergistic anti-amoebic activity against Acanthamoeba trophozoites and cysts, and co-treatment with EC and a subclinical dose of CHX (0.001 and 0.002%) revealed a dose-dependent anti-amoebic effect on both trophozoites and cysts equivalent to or greater than a clinical dose of CHX (0.02%). The promising anti-amoebic activity of EC against Acanthamoeba clinical isolates, along with the observed synergistic effect with CHX, highlights its potential as a drug candidate or an adjunctive treatment for AK.

Respiratory infections are among the leading causes of morbidity and mortality worldwide, especially among children, the elderly, and immunocompromised individuals. To address the limitations of the existing diagnostic tools and improve testing efficiency, we developed, optimized and tested in-house targeted next-generation sequencing assay capable of simultaneously detecting 32 groups of viruses and 13 bacteria commonly associated with respiratory infections. Using NGS-PrimerPlex, we designed a total of 117 primer pairs-at least two per pathogen-targeting different genomic regions. These primers were divided into three multiplex PCR reactions and evaluated both in silico for specificity and coverage, and in vitro via monoplex PCR with positive controls and polyacrylamide gel electrophoresis. We systematically optimized key variables including primer (15-260 nM) and dNTP (0.1-1.6 mM) concentrations, PCR cycle number (20-35), annealing temperature (57-62°C), ramp rate (0.2-4°C/s), and reverse transcription protocols. The assay was validated using 120 complementary DNA (cDNA) samples from patients at Speransky Children's Hospital #9 in Moscow, Russia, previously tested with a commercial multiplex PCR respiratory virus panel. The NGS assay showed complete concordance with the PCR results in 60% of positive samples, increasing to 74% when samples with Cq values above 29 were excluded. Additionally, the NGS assay detected target pathogens in 13 PCR-negative samples and identified other respiratory pathogens not included in the commercial panel in 47 PCR-negative samples. Overall, the assay identified at least one target pathogen in 86 of 120 samples, demonstrating its potential for comprehensive respiratory pathogen detection, surveillance, and clinical diagnostics. Our findings offer a robust foundation for future development of targeted NGS-based assays.

Although the current therapeutic regimens for acute toxoplasmosis, most commonly a combination of pyrimethamine and sulfadiazine, are still considered the standard of care, they are associated with numerous drawbacks, such as bone marrow suppression, and hepatotoxicity. Given these challenges, there is an urgent need to explore and find safer and more effective therapeutic alternatives. Acetazolamide has been widely used in clinical practice for non-infectious illnesses. Lately, increasing attention has been directed toward its repurposing as an antiparasitic agent. Thirty-six mice were infected with Toxoplasma gondii (RH strain) tachyzoites, and divided into three groups: non-treated group, Acetazolamide-treated group and Septrin- treated group. In the present study, the anti - Toxoplasma efficacy of Acetazolamide was assessed in comparison to Septrin using parasitological, ultrastructural, biochemical, immunological, and histopathological studies. Treatment with Acetazolamide significantly prolonged the mice's survival time and reduced tachyzoites count with percentages of reduction of 83.12% and 79.84 % in the peritoneal fluids and hepatic impression smears, respectively. Furthermore, Acetazolamide has dramatically altered the ultrastructure of the tachyzoites, decreased the liver and kidney malondialdehyde levels and suppressed serum cytokines (tumor necrosis factor alpha and interleukin-1β). Histopathological examination of hepatic and renal tissue sections showed amelioration of parenchymal inflammation and scanty parasite. In conclusion, Acetazolamide demonstrated a significant promise as a therapeutic agent for combating acute murine toxoplasmosis with anti-inflammatory and antioxidant effects.