Search Results (228)

Alphaherpesviruses, including Herpes Simplex Virus 1 (HSV-1) and Pseudorabies Virus (PrV), establish lifelong latency in the nervous system and can cause recurrent disease. While latency has classically been attributed to peripheral sensory ganglia, accumulating evidence indicates that the central nervous system (CNS) may also serve as a site of long-term viral persistence and reactivation. Here, we investigated the CNS as a viral reservoir using the attenuated mutant PrV-∆UL21/US3∆kin, which preferentially targets mesiotemporal brain regions. Following intranasal inoculation, mice were analyzed at 11–14, 21, 28, 42, 105, and 190 days post-infection (dpi). To assess the reactivation potential, a subset of animals received cyclophosphamide/dexamethasone at 170 dpi. Viral transcripts were detected by RNAscope™ in situ hybridization and RT-qPCR targeting the lytic gene UL19 encoding the major capsid protein and the latency-associated transcript (LAT). Histopathology included hematoxylin and eosin staining and immunohistochemistry for CD3, Iba1, GFAP, cleaved caspase-3 and viral glycoprotein gB. UL19 RNA signals displayed marked regional and temporal heterogeneity, with prominent detection in mesiotemporal structures. In contrast, LAT RNA levels remained low overall, with a transient peak during the acute phase. RT-qPCR confirmed high UL19 and LAT transcript levels during early infection, while LAT transcription returned to baseline levels thereafter. Histopathology showed a transition from acute necrotizing meningoencephalitis to prolonged low-grade inflammation with glial activation and focal apoptosis. Notably, UL19 RNA signals strongly correlated with T-cell infiltration, particularly at 42 dpi. Together, these findings define regional and temporal patterns of long-term PrV transcriptional activity and associated neuropathology in the murine CNS. Full article

Background/Objectives: Naegleria fowleri is an opportunistic pathogen causing primary amoebic meningoencephalitis (PAM), a fatal neuroinflammatory disease with a high mortality rate of over 97%, in humans. Currently, there are no approved therapeutics for PAM, underscoring the urgent necessity of developing effective and safe drugs. This study aimed to evaluate the potential of ginsenosides Rb3 and Rc as alternative or supplementary drug candidates for PAM by assessing their anti-amoebic activities against N. fowleri. Methods: Anti-N. fowleri activities of ginsenosides Rb3 and Rc and their cytotoxicity to C6 glial cells were evaluated by cell viability assay. The underlying anti-amoebic mode of action of Rb3 and Rc was analyzed by a series of assays for apoptosis–necrosis, TUNEL, intracellular reactive oxygen species (ROS), mitochondrial dysfunction, ATP production, caspase-3, and autophagy. The expression profiles of apoptosis- and autophagy-related genes were also analyzed. Results: Rb3 and Rc effectively induced death of N. fowleri trophozoites with IC₅₀ values of 94.71 ± 1.63 μM and 126.99 ± 1.88 μM, respectively. However, Rb3 and Rc showed no significant cytotoxicities against C6 glial cells, suggesting their selective anti-N. fowleri activities. Typical apoptosis signals, such as apopxin staining and DNA fragmentation, were detected in amoebae upon treatment with Rb3 or Rc. These two ginsenosides enhanced ROS production and induced mitochondrial dysfunction in the amoebae. Enhanced caspase-3 activity and autophagy formation were also identified in amoebae treated with Rb3 or Rc. Conclusions: These results provide the first evidence that ginsenosides Rb3 and Rc induce apoptosis-like programmed cell death in N. fowleri, suggesting that they are potential candidates in developing novel therapeutic strategies against PAM. Full article

Background/Objectives: Primary amoebic meningoencephalitis (PAM) is a rare, fulminant, and often fatal central nervous system infection caused by the opportunistic free-living amoeba Naegleria fowleri. Although Naegleria species are widely present in freshwater and soil worldwide, human disease is associated specifically with pathogenic N. fowleri rather than the many nonpathogenic environmental species, and virulence may vary across N. fowleri isolates. This systematic review aimed to synthesize contemporary global data from 2000 to 2024 to identify recent trends in epidemiology, clinical presentation, diagnosis, treatment, and outcomes. Methods: A systematic literature search was conducted across PubMed, Scopus, and the Cochrane Library, identifying 58 eligible publications encompassing 66 individual cases. Results: Most reports originated from the United States, India, and China. The median patient age was 14 years, with 78% of cases occurring in males. Annual case reports increased from one per year (2000–2005) to over four per year (2020–2024), reflecting either a true rise in incidence or improved detection. Common presenting symptoms included fever, headache, and altered mental status. Diagnosis was confirmed via polymerase chain reaction (PCR) testing or post-mortem biopsy in nearly one-third of cases. Treatment regimens varied, with amphotericin B and miltefosine being the most frequently used agents. Overall mortality was 83%, with survival strongly associated with early initiation of combination therapy. Pediatric patients had a higher survival rate (22%) compared to adults (7.1%). Conclusions: The findings highlight the need for heightened clinical awareness, especially in the context of climate-driven ecological changes that may expand N. fowleri’s geographic range. This review underscores critical gaps in surveillance and diagnostics and emphasizes the importance of a One Health approach to addressing emerging threats like PAM. Further research into novel therapeutics, rapid diagnostics, and global case reporting systems is urgently needed. Full article

Devastating or nearly invariably fatal infections caused by free-living amoebae (FLA), including Acanthamoeba keratitis (AK), granulomatous amoebic encephalitis (GAE), and primary amoebic meningoencephalitis (PAM), remain a significant public health concern, driven by increasing case numbers, geographic expansion, and the lack of approved, effective, and safe treatments. Despite decades of research, no new drugs have been successfully approved, highlighting the severe limitations of de novo drug development for these infections, particularly for GAE and PAM, largely due to the challenges of conducting clinical trials for these rare and rapidly lethal diseases. In this context, drug repurposing represents a cost-effective and promising strategy to accelerate therapeutic advances and overcome key bottlenecks of conventional drug development. Accordingly, we conducted a systematic review of in vitro studies and animal models of AK, GAE, and PAM reported in indexed databases to identify promising drug repurposing candidates against FLA infections. After screening 23,624 records, 112 studies were included in the analysis. Overall, 2726 drugs and drug combinations, spanning 865 pharmacological classes and approved for 565 therapeutic indications, were assessed for their repurposing potential. Among these, 166 compounds showed substantial trophocidal activity (≥IC₅₀) at potentially translatable concentrations (≤10 µM), including six with additional cysticidal activity. In vitro, four compounds were active against Balamuthia mandrillaris, 44 against Acanthamoeba spp. (three cysticidal), and 115 against Naegleria spp. (three cysticidal). In in vivo studies, sulfadiazine and rifampicin were effective as preventive or early monotherapies for GAE. For AK, the combination of polyhexamethylene biguanide, neomycin, and atropine, as well as voriconazole and nitazoxanide monotherapies, showed the greatest promise. In PAM, azithromycin alone or in combination with amphotericin B emerged as the most promising therapeutic options. Further studies are required to advance the clinical translatability of these findings. To the best of our knowledge, this work provides the first comprehensive and integrated synthesis of repurposable drug candidates against FLA infections. Full article

Background/Objectives: Encephalitis and related acute encephalopathic syndromes represent severe neurological conditions with diverse etiologies and variable clinical outcomes. This study aimed to analyze nationwide hospitalization patterns for encephalitis-related diagnoses in Ecuador between 2018 and 2024. Methods: We used data from the Ecuadorian National Institute of Statistics and Census to estimate age-adjusted hospitalization and mortality rates according to ICD-10 codes. Binary and multinomial logistic regression models were employed to identify sociodemographic factors and diagnostic categories of encephalitis associated with hospitalization and in-hospital mortality. Results: A total of 1560 hospitalizations related to encephalitis-spectrum diagnoses were recorded, with an overall age-adjusted rate of 0.127 per 100,000 inhabitants and 6.0% in-hospital mortality. Unspecified encephalitis and encephalomyelitis were the most common diagnostic categories. Adolescents (10–19 years) were more frequently diagnosed with acute disseminated and bacterial meningoencephalitis, while patients aged ≥70 had higher odds of “other” encephalitis subtypes and the highest mortality risk (aOR = 0.265; 95% CI: 0.116–0.608). Indigenous individuals were more likely to be diagnosed with acute disseminated encephalitis, and Black individuals showed a higher risk for myelopathy associated with human T-cell lymphotropic virus type 1-associated myelopathy. Conclusions: Age and ethnicity significantly influence hospitalization due to encephalitis-related diagnoses in Ecuador. These findings provide epidemiological rates for a lower-middle–income country where the lack of precise diagnosis, age, and ethnicity contribute to the vulnerability of encephalitis. Full article

Murine typhus (also called flea-borne or endemic typhus) is an undifferentiated febrile illness caused by the bacterium Rickettsia typhi. The disease, transmitted by rat and cat fleas, is endemic to seaboard regions worldwide. Recently, murine typhus has reemerged as an increasingly recognized cause of febrile illness in the United States, especially in Texas and Southern California. In addition to fever, manifestations often include headache, malaise, myalgias, and a maculopapular rash in approximately half of cases. Although usually considered a mild illness, when untreated, symptoms can last up to 3 weeks. Severe manifestations such as pneumonitis, acute kidney injury, and meningoencephalitis may occur. Historically, death has occurred in 0.4%, but in Southern California, the case fatality rate has been recently recorded at 1.8%. As murine typhus has reemerged, there have been growing reports that this infection has triggered hemophagocytic lymphohistiocytosis, a life-threatening hyperinflammatory syndrome. We herein report two fatal cases of hemophagocytic lymphohistiocytosis secondary to murine typhus. Autopsy revealed typhus group rickettsial antigen in tissues via immunohistochemistry, along with hemophagocytosis. Interestingly, the classic vascular and perivascular histopathologic findings associated with disseminated rickettsial infection were absent. These findings highlight an aberrant inflammatory cascade leading to hemophagocytic lymphohistiocytosis. Full article

Background: Meningoencephalitis is a complex inflammatory condition of the CNS that can result in significant morbidity and mortality in critically ill adults. Accurate and timely neuromonitoring is essential for guiding management and improving outcomes. This study aimed to descriptively evaluate the prognostic value of early TCCD monitoring, particularly the pulsatility index, and its integration with conventional and perfusion MRI in patients with meningoencephalitis. Methods: We present an observational, retrospective, cohort study involving ten adult patients (median age 56 years, IQR 45.5–68.5; mean 55.9, range 35–76) with neurological syndromes caused by suspected or confirmed infectious meningoencephalitis. Etiologies included bacterial meningitis/meningoencephalitis (50%), viral meningoencephalitis (10%), neurotoxoplasmosis (10%), progressive multifocal leukoencephalopathy (10%), and undetermined origin (20%). Patients underwent TCCD and MRI within 24 h. In five cases, standard MRI sequences were acquired, while in the remaining five, perfusion imaging was performed using Arterial Spin Labelling (ASL). A favorable outcome was defined as survival with neurological recovery (Glasgow Outcome Scale > 5) at ICU discharge. Results: TCCD-derived PI provided valuable information on cerebral hemodynamics. PI values ≤ 1.25 were associated with favorable clinical outcomes and symmetrical MRI findings. Conversely, PI > 1.25 correlated with poor prognosis and often preceded MRI-detectable structural damage. When combined with ASL, PI mirrored the detected perfusion asymmetries and was associated with poor prognosis in fatal cases. Conclusions: Bedside TCCD can offer real-time assessment of cerebrovascular dynamics and, when integrated with conventional and ASL MRI, could enhance the understanding of pathophysiological processes in meningoencephalitis, supporting timely and informed decisions in neurocritical care. Full article

Objectives: Free-living amoeba Naegleria fowleri causes primary amoebic meningoencephalitis (PAM). While infection is rare, PAM’s fatality rate exceeds 97%. The recommended treatment includes combination therapy, which does not result in uniform survival. Thus, there is a critical unmet need for finding better therapy for PAM. Drug repurposing can expedite the discovery of effective treatment for PAM. Isavuconazonium is approved for the treatment of fungal infections. Given that isavuconazole is the major metabolite of isavuconazonium and isavuconazole penetrates into the brain with high efficiency, our objective was to determine the activity of both isavuconazonium and isavuconazole on N. fowleri trophozoites. Methods: To test the effect of both compounds, we determined their dose–responses against N. fowleri and two mammalian cells. To establish how fast the prodrug and the metabolite kill the trophozoites, we measured potency at different time points. Finally, we investigated the effect of combining isavuconazonium or isavuconazole with amphotericin B on both N. fowleri and mammalian cells. Results: Both isavuconazonium and the metabolite isavuconazole were active against multiple strains, with clinically relevant isavuconazole exhibiting potency ranging between 0.1 and 0.6 µM. They were less toxic on mammalian cells. Isavuconazonium and isavuconazole required 24 h to achieve nanomolar potency. Combination with amphotericin B was synergistic without eliciting toxicity on mammalian cells. Conclusions: Our findings, together with the use of intravenous and oral formulations of isavuconazonium to treat pediatric and adult patients, support further in vivo efficacy study of isavuconazonium for its potential use for the treatment of PAM. Full article

Background: Naegleria fowleri is a free-living amoeba that inhabits warm freshwater and causes primary amoebic meningoencephalitis (PAM), a rapidly fatal infection with >95% mortality. Due to the lack of early diagnosis and effective therapy, preventive vaccination represents a promising strategy. Methods: This study evaluated short- and long-term immune protection in BALB/c mice (20 mice per group) immunized intranasally with total N. fowleri extract co-administered with cholera toxin (CT). Mice were challenged with a lethal dose of trophozoites either 24 h (short-term) or three months (long-term) after the fourth immunization; the latter group received a booster 24 h before challenge. Serum and nasal washes were analyzed for IgA and IgG antibodies by immunoblot, and lymphocyte subsets from nasal-associated lymphoid tissue (NALT) and nasal passages (NPs) were characterized by flow cytometry. Results: Immunization conferred complete (100%) survival in the 24 h group and 60% protection in the 3-month group, whereas all control mice died. Immunoblotting showed that IgA and IgG antibodies recognized major N. fowleri antigens of 37, 45, 48 and 19, 37, and 100 kDa, respectively. Flow cytometry revealed increased activated and memory B lymphocytes, dendritic cells, and expression of CCR10, integrin α4β1, and FcγRIIB receptors, particularly in the 24 h group. Conclusions: Intranasal immunization with N. fowleri extract plus CT elicited both systemic and mucosal immune responses capable of short- and long-term protection. These findings highlight the potential of this immunization strategy as a foundation for developing effective vaccines against PAM. Full article

Background and Clinical Significance: Cerebral candidiasis (Candida albicans meningoencephalitis) is a rare but severe central nervous system (CNS) infection, usually associated with neurosurgical procedures or indwelling devices. Diagnosis is challenging due to frequent negativity of cerebrospinal fluid (CSF) cultures, and mortality remains high despite antifungal therapy. Case Presentation: We describe a 64-year-old woman who underwent retrosigmoid resection of a left vestibular schwannoma. The early postoperative course was complicated by fever, neurological deterioration, and hydrocephalus requiring external CSF drainage. Multiple lumbar punctures revealed inflammatory CSF profiles but persistently negative cultures. One month post-surgery, intraoperative samples from mastoid repair material grew Candida albicans, prompting antifungal therapy. Despite treatment, the patient experienced fluctuating neurological status and required multiple external ventricular drains. Three months after surgery, she clinically deteriorated and died. Autopsy showed diffuse meningeal thickening and purulent exudates at the brain base and posterior fossa. Histopathology confirmed chronic lympho-histiocytic meningitis with necrotizing foci containing Candida albicans. Conclusions: This case underscores the diagnostic and therapeutic challenges of post-neurosurgical Candida CNS infections. Repeatedly negative CSF cultures delayed diagnosis, emphasizing the value of ancillary tests such as β-d-glucan and molecular assays. Even with antifungal therapy, prognosis is poor. Autopsy remains essential for uncovering fatal healthcare-associated fungal infections and informing clinical vigilance and medico-legal assessment. Full article

Highly pathogenic avian influenza (HPAI) H5N1 clade 2.3.4.4b viruses spread efficiently via migratory wild birds and increasingly infect mammals. The leopard cat (Prionailurus bengalensis) is an endangered mesopredator in South Korea that frequents wetland–forest ecotones and overlaps with wild waterbirds, placing it at risk of exposure. We describe a fatal HPAI H5N1 infection in a free-ranging leopard cat detected through national wildlife surveillance during a period of widespread H5N1 activity in wild birds along the East Asian–Australasian Flyway. The animal showed acute neurological and respiratory signs and died shortly after rescue. H5 viral RNA was detected by RT-qPCR in all examined tissues, with the highest load in the brain, and infectious virus was isolated from the brain, bronchoalveolar lavage fluid, and nasal swab. Pathology revealed acute serofibrinous pneumonia, severe nonsuppurative meningoencephalitis, necrotizing vasculitis with thrombosis, and necrotizing enteritis with secondary mesenteritis. Immunohistochemistry demonstrated abundant viral antigen in nasal and olfactory epithelium, olfactory bulb, neurons, endothelial cells, and bronchial and bronchiolar epithelium, supporting combined olfactory and hematogenous dissemination. This clinicopathological description expands the spectrum of HPAI-associated lesions in felids and underscores the value of wild carnivores as bioindicators of avian influenza spillover in a One Health context. Full article

Coxsackievirus B3 (CVB3) is a picornavirus that causes systemic inflammatory diseases including myocarditis, pericarditis, pancreatitis, and meningoencephalitis. We have previously reported that CVB3 induces mitochondrial fission and mitophagy while inhibiting lysosomal degradation by blocking autophagosome-lysosome fusion. This promotes the release of virus-laden mitophagosomes from host cells as infectious extracellular vesicles (EVs), enabling non-lytic viral egress. Transient receptor potential vanilloid 1 (TRPV1), a heat and capsaicin-sensitive cation channel, regulates mitochondrial dynamics by inducing mitochondrial membrane depolarization and fission. In this study, we found that TRPV1 activation by capsaicin dramatically enhances CVB3 egress from host cells via EVs. Released EVs revealed increased levels of viral capsid protein VP1, mitochondrial protein TOM70, and fission protein phospho-DRP1. Moreover, these EVs were enriched in heat shock protein HSP70, suggesting its role in facilitating infectious EV release from cells. Furthermore, TRPV1 inhibition with capsazepine and SB-366791 significantly reduced viral infection in vitro. Our in vivo studies also found that SB-366791 significantly mitigates pancreatic damage and reduces viral titers in a mouse model of CVB3 pancreatitis. Given the lack of understanding regarding factors that contribute to diverse clinical manifestations of CVB3, our study highlights capsaicin and TRPV1 as potential exacerbating factors that facilitate CVB3 dissemination via mitophagy-derived EVs. Full article

Background/Objectives: Edwardsiella tarda is a rare Gram-negative pathogen that uncommonly infects humans. Neonatal infections are extremely rare but often severe, with a high incidence of central nervous system (CNS) complications. Case presentation: We report a term neonate born via spontaneous vaginal delivery who developed systemic signs of infection within 18 h of life. Blood and cerebrospinal fluid (CSF) cultures grew Edwardsiella tarda. CSF analysis revealed severe meningoencephalitis. Maternal stool culture was also positive for E. tarda, suggesting vertical transmission. Despite initial systemic antibiotic therapy with ampicillin, gentamicin, and ceftriaxone, neuroimaging revealed progressive multifocal brain abscesses. The infant underwent a series of neurosurgical procedures, including bilateral drainage of abscesses, Rickham reservoir placement and ventriculoperitoneal shunting. A revised antibiotic regimen, including systemic meropenem and trimethoprim-sulfamethoxazole plus intrathecal gentamicin, was administered. At six months, the infant showed mild motor delay with lower limb hypertonia and was under close neurosurgical and developmental follow-up. Methods: We conducted a literature review of 12 published neonatal E. tarda infections, including our case. Results: Most infected infants presented within 72 h of life and exhibited CNS involvement. Mortality was 25%, and 44% of survivors experienced long-term neurologic sequelae. Conclusions: Edwardsiella tarda infection in neonates is rare but potentially devastating. Early suspicion, culture confirmation, aggressive antibiotic therapy, and multidisciplinary care, including neurosurgical management, are essential for improving outcomes. Full article

Central nervous system (CNS) cryptococcosis caused by Cryptococcus neoformans is a severe opportunistic infection that primarily affects individuals with impaired cellular immunity. Although the classic presentation includes headache, fever, and meningeal signs, chronically immunosuppressed patients may develop atypical neuropsychiatric manifestations, leading to diagnostic delays. We report the case of a 53-year-old man with rheumatoid arthritis (RA) receiving long-term prednisolone and etanercept therapy, who presented with a 7-day history of depressive mood, anhedonia, social withdrawal, irritability, and progressive confusion. Neurological examination revealed disorientation without focal deficits. Brain imaging showed only mild cortical atrophy, and cerebrospinal fluid (CSF) analysis revealed lymphocytic pleocytosis, low glucose, and elevated protein levels. Multiplex PCR (FilmArray^®) of CSF identified Cryptococcus neoformans, CSF positive to C. neoformans. The patient was treated with liposomal amphotericin B followed by fluconazole, resulting in gradual improvement of both neurological and psychiatric symptoms. This case highlights an unusual presentation of CNS cryptococcosis in a non-HIV immunosuppressed patient with RA, emphasizing that acute psychiatric or cognitive changes can be the predominant manifestation. Clinicians should consider fungal infections in the differential diagnosis of acute neuropsychiatric symptoms in patients receiving chronic corticosteroid and biologic therapy. Early recognition and molecular diagnosis can facilitate timely antifungal treatment, potentially improving prognosis and reducing morbidity associated with delayed therapy. This report underscores the importance of awareness of atypical presentations of opportunistic infections in immunosuppressed populations. Full article

Background/Objectives: Varicellovirus bovinealpha1 and Varicellovirus bovinealpha5 (BoAHV-1 and BoAHV-5), respectively, are widely distributed pathogens that cause distinct clinical conditions in cattle including infectious bovine rhinotracheitis, infectious pustular vulvovaginitis/balanoposthitis, and meningoencephalitis. Due to the establishment of viral latency, controlling these infections is challenging, and vaccination remains the most effective strategy. In this study, vaccine candidates targeting both BoAHV-1 and BoAHV-5 were developed. Methods: A synthetic gene encoding immunodominant epitopes from the gB and gD proteins and tegument phosphoprotein of BoAHV-1 and BoAHV-5 was designed to produce a multi-epitope recombinant antigen, expressed both in a prokaryotic system (RecBoAHV) and by a modified vaccinia Ankara (MVA-BoAHV) viral vector. The binding affinity of MHC-I to bovine leukocyte antigens (BoLA) was predicted using the NetMHCpan tool (version 4.1). The immunogenicity of the vaccine candidates was evaluated in rabbit and mouse models, using prime-boost immunization protocols. Sera from bovines naturally infected with BoAHV-1 and/or BoAHV-5 were used to evaluate the chimeric protein antigenicity. Immune responses were assessed by indirect ELISA and Western blot. Results: The recombinant multi-epitope protein was effectively recognized by IgG and IgM antibodies in sera from cattle naturally infected with BoAHV-1 or BoAHV-5, confirming the antigenic specificity. Both RecBoAHV and MVA-RecBoAHV induced strong and specific humoral immune responses in rabbits following a homologous prime-boost regimen. In mice, both homologous and heterologous prime-boost protocols revealed robust immunogenicity, particularly after the second booster dose. Conclusions: These findings highlight the immunogenic potential of the RecBoAHV multi-epitope vaccine candidates for controlling BoAHV-1 and BoAHV-5 infections. Further characterization of these vaccine formulations is currently underway in bovine, the target specie. Full article