Mahidol University's Institutional Repository
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Recent Submissions
Multiple orthoflaviviruses secrete sfRNA in mosquito saliva to promote transmission by inhibiting MDA5-mediated early interferon response
(2026-08-29) Serrato-Pomar I.; Medkour H.; Belleville L.; Jintana K.; Pruvost L.; Schneider N.; Tavadia M.; Zoladek J.; Rachenne F.; Roux Z.; Narpon Q.; Rey-Cadilhac F.; Rossi S.; French S.; Modahl C.; Ginibre C.; Scheid B.; Sornjai W.; Miot E.F.; Smith D.R.; Hamel R.; Medianikov O.; Missé D.; Nisole S.; Pompon J.; Serrato-Pomar I.; Mahidol University
Numerous orthoflaviviruses transmitted through the bites of different mosquito species infect more than 500 million people annually. Skin infection at the bite site represents a critical and conserved step in transmission and a deeper understanding of this process will promote the design of broad-spectrum interventions. Here, we identify and characterize a transmission-enhancing viral factor in mosquito saliva that is shared across orthoflaviviruses. Saliva from West Nile virus-infected Culex and Zika virus-infected Aedes contains a viral non-coding RNA, subgenomic flaviviral RNA (sfRNA), within lipid vesicles distinct from virions. Higher concentration of sfRNA in infectious saliva positively correlates with infection intensity in human cells and skin explants. Early sfRNA delivery into transmission-relevant skin cell types and human skin explant demonstrate that sfRNA is responsible for the infection enhancement. Co-inoculation of sfRNA in a mouse model of transmission enhanced skin infection and worsened disease severity, supporting the role of salivary sfRNA as a transmission-enhancer. Mechanistically, salivary sfRNA attenuates early interferon response in human skin cells and skin explants by disrupting MDA5 signaling. Our results, derived from two distinct orthoflaviviruses and supported by prior studies, establish salivary sfRNA as a pan-orthoflavivirus transmission-enhancing factor driven by a conserved viral non-coding RNA.
Impact of Specific Pattern Mutations on Plaque Formation and Attenuation Properties of Dengue Virus Serotype 3
(2026-01-01) Sun-Arlee P.; Punyahathaikul S.; Rodpai E.; Ketsuwan K.; Wanlayaporn D.; Ruangdachsuwan S.; Komaikul J.; Jaimipuk T.; Juntarapornchai S.; Boonarkart C.; Jongkaewwattana A.; Yoksan S.; Auewarakul P.; Masrinoul P.; Sun-Arlee P.; Mahidol University
Dengue fever is a major public health problem in several countries, including Thailand. The development of an effective dengue vaccine against all four serotypes is important for controlling the disease. An attenuated dengue-3 vaccine candidate, namely, DENV3-MBU-1, was derived from full-length cDNA-assembled segments based on the sequence of a prototype DENV3 vaccine candidate originating from the DENV3 strain 16562, which was passaged 30 times in primary green monkey kidney cells and four times in primary dog kidney cells. Compared to the parental DENV3-16562 sequence, this DENV3-MBU-1 contains seven nonsynonymous mutations in the premembrane (prM), envelope (E), and nonstructural proteins (NS2A, NS3, NS4). In this study, we aimed to characterize the mutations contributing to attenuation by generating different DENV3 mutants and evaluating their properties, including plaque formation and neurovirulence in mice. The DENV3-MBU-1 mutants, in which the NS proteins were reverted to those of the parental virus, exhibited an altered phenotype, manifested by changes in plaque size and virulence, resembling that of the parental virus. This suggests the important role of the NS segment in attenuation. Interestingly, the mutants of DENV3-MBU-1, in which only the structural proteins, but not the NS proteins were altered, showed changes in phenotype toward increased plaque size and neurovirulence. This suggests that attenuation may be influenced by specific combinations of mutations rather than single-point mutations. These findings, along with the attenuated DENV3 viruses generated, provide useful information for the development of a dengue vaccine.
Exosomes Derived from Stem Cells from Human Exfoliated Deciduous Teeth Attenuate Glycation-Induced Oxidative Stress and Cytotoxicity in Neuronal Cells
(2026-01-01) Surangkul D.; Atipimonpat A.; Saephu M.; Jongtep P.; Sangburan W.; Chiangjong W.; Sritanaudomchai H.; Surangkul D.; Mahidol University
Objectives Advanced glycation end products (AGEs) induce oxidative stress and cellular injury through excessive reactive oxygen species (ROS), contributing to aging- and diabetes-related degenerative conditions. Exosomes derived from stem cells from human exfoliated deciduous teeth (SHED) exhibit regenerative and cytoprotective properties. This study aimed to investigate the effects of SHED-derived exosomes on AGE-induced oxidative stress and cytotoxicity in neuronal cells. Materials and Methods Exosomes were isolated from SHED-serum-free conditioned medium by differential ultracentrifugation and characterized using transmission electron microscopy, nanoparticle tracking analysis, and Western blotting for CD81, TSG101, and HSP70. Uptake of PKH26-labeled exosomes by SK-N-SH neuroblastoma cells was evaluated using confocal microscopy. AGEs were generated by incubating bovine serum albumin with glucose and confirmed by fluorescence analysis. Cell viability and intracellular ROS levels were assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and 2′,7′-dichlorodihydrofluorescein diacetate (DCHF-DA) assays, respectively. Proteomic analysis was performed to identify proteins associated with cytoprotective activity. Statistical Analysis Data were presented as mean ± standard deviation from triplicate experiments. Statistical analysis was performed using one-way analysis of variance followed by appropriate post hoc tests. A p -value of < 0.05 was considered statistically significant. Results SHED-derived exosomes exhibited a typical cup-shaped morphology with sizes ranging from 37 to 200 nm and expressed canonical exosomal markers. SK-N-SH cells efficiently internalized SHED-derived exosomes. AGE treatment induced dose-dependent cytotoxicity (IC50 = 5.24 mg/mL) and significantly increased intracellular ROS levels. Treatment with SHED-derived exosomes at 30 to 50 μg/mL significantly improved cell viability, whereas 20 μg/mL significantly reduced AGE-induced ROS accumulation (p < 0.05). Proteomic analysis identified proteins associated with oxidative stress response, cellular repair, and cell survival pathways. Conclusion Exosomes derived from SHED attenuated AGE-induced oxidative stress and cytotoxicity in neuronal cells. These findings suggest the potential application of SHED-derived exosomes as a cell-free approach for oxidative stress-related cellular injury.
A mixed-methods study of community dog management and rabies awareness in Thailand
(2026-12-01) Thichumpa W.; Wiratsudakul A.; Pan-ngum W.; Rawson T.; Hauck K.D.; Garske T.; Thichumpa W.; Mahidol University
Rabies elimination requires coordinated interventions across the human-animal-environment interface, yet sustained progress is often hindered by systemic gaps between dog population management, community engagement, and governance. This study investigated community perceptions and challenges related to rabies prevention and control across high-endemic areas in Thailand. Using a mixed-methods design, secondary provincial quantitative data were integrated with qualitative thematic analysis from 57 stakeholders in high endemic areas, including public health officials, policymakers, NGOs, animal-welfare liaisons, and community members. The findings indicated standard rabies awareness, 98.2% of participants demonstrated good preventive practices, recognized post-exposure prophylaxis (PEP) as essential, and 68.4% possessed good knowledge. Although most supported dog sterilization (59.6%) and vaccination (63.2%), only 19.3% perceived existing control campaigns as effective. Main challenges included constrained operational resources (57.9%) and limited local government budgets (40.4%). Free-roaming community dogs were prevalent, with 54.4% of participants identifying abandonment as the primary driver of population growth. Informal feeding networks provided localized care for community dogs. While public willingness to fund management was relatively low (33.3% willing to pay; 19.3% supporting co-payment), reflecting an expectation of local authority responsibility. Qualitatively, unclear boundaries between public health mandates and animal welfare legal frameworks added complexity to rabies outbreak response and sometimes introduced institutional challenges among local government and non-governmental sectors. Nevertheless, stakeholders strongly supported sustained sterilization and intersectoral collaboration. Addressing policy-practice gaps, stabilizing financing, and integrating community social dynamics into formal One Health governance are crucial for achieving sustainable rabies elimination.
Sex estimation from sacrum osteometrics: Distinguishing intrinsic morphological signal from algorithm-driven accuracy using machine learning
(2026-11-01) Iamsaard S.; Aorachon P.; Soonsawad P.; Bunpuang J.; Busaban F.; Poodendaen C.; Wongwad N.; Duangchit S.; Iamsaard S.; Mahidol University
Background/objectives Sex estimation is a fundamental step in constructing the biological profile of unidentified skeletal remains, and the sacrum, although less studied than the os coxae, offers a potentially useful complementary source of evidence. This study aimed to estimate sex from the sacrum and to evaluate whether the resulting classification accuracy reflects a genuine morphological signal or largely depends on the flexibility of the classification method. Materials and methods Seven sacral osteometric parameters were measured in 300 dry sacra from Northeastern Thailand, comprising 150 males and 150 females. Discriminant function analysis, support vector machine, and random forest were applied to the six parameters showing significant sex differences and evaluated using leave-one-out cross-validation. K-means and TwoStep clustering, performed without reference to sex, were compared with documented sex. Results Six of seven parameters differed significantly between sexes. The three supervised classifiers achieved comparable accuracy, ranging from 87.3 to 90.0 percent, with no statistically significant differences among them. K-means and TwoStep clustering achieved 81.3 and 73.7 percent concordance with documented sex respectively, both above chance but below supervised accuracy. The antero-posterior diameter of sacral segment 1 and the vertical length of the auricular surface were the strongest contributors to classification. Conclusion Sacral sexual dimorphism reflects a genuine but incomplete natural structure, with part of the supervised models' accuracy depending on training with sex labels. The sacrum may serve as a useful complementary element in multi-element forensic sex estimation.