Biology subjects

Upasani, V.

Publications and source records attributed to Upasani, V..

4 recordsLinked to original sources

bioRxiv2026

A TLR2-associated entry pathway promotes productive dengue virus serotype 2 infection and inflammatory responses in classical monocytes

Severe dengue is characterized by systemic inflammation and vascular leakage. Recent evidence indicates that Toll-like receptor 2 (TLR2) supports early steps of dengue virus (DENV) infection in monocytes, whereas intracellular viral RNA sensing drives much of the subsequent inflammatory response. However, whether this entry-associated function of TLR2 differs among human monocyte subsets remains unknown. Here, we investigated how the TLR2 axis regulates DENV serotype 2 (DENV2) infection and inflammatory output in purified primary human monocytes and sorted monocyte subsets. Blocking TLR2 at the cell surface or targeting its intracellular TIR domain reduced virus-cell association, productive infection, and the release of inflammatory and antiviral mediators. Among TLR2-associated receptors, CD14 and, to a lesser extent, CD36 contributed to efficient infection, whereas TLR1, TLR6, and TLR10 were dispensable under the conditions tested. Notably, TLR2 blockade reduced viral production and cytokine release in CD16- classical monocytes but not in pooled CD16+ monocytes, identifying a subset-specific dependence on the TLR2 axis. TLR3 contributed to inflammatory and antiviral responses without affecting viral replication, consistent with post-entry recognition of viral RNA. Finally, blocking the TLR2 axis during monocyte infection prevented the loss of endothelial barrier integrity induced by monocyte-derived soluble mediators. Together, these findings identify a TLR2-associated entry route that preferentially supports productive DENV2 infection in classical monocytes and thereby enables RNA-sensor-dependent inflammatory responses that compromise endothelial function.

microbiology↗

bioRxiv2026

Single-cell transcriptomics resolves the developmental transitions from schizont to invasive extracellular merozoite to ring-stage Plasmodium falciparum parasites

The progression from mature schizonts to newly formed ring-stage parasites represents one of the largest developmental transitions in the Plasmodium falciparum intraerythrocytic developmental cycle (IDC), encompassing parasite egress, erythrocyte invasion, and productive infection of the new host cell. While the transcriptional programs required for egress and invasion are well-documented, less is known about how the parasite prepares for intracellular survival inside the newly invaded erythrocyte. Here, we used single-cell RNA sequencing based on PIPseq chemistry to construct a transcriptional atlas spanning late schizogony, extracellular merozoites, and early ring-stage development. We show that schizogony is characterized by sequential waves of invasion gene expression that closely parallel secretory organelle biogenesis and are associated with cooperative regulation by ApiAP2 transcription factors. Immediately prior to egress, parasites shift from expression of invasion genes to genes required for establishing the intracellular host-parasite interface, including the parasitophorous vacuole and digestive vacuole. Extracellular merozoites separate into transcriptionally distinct invasive and non-invasive populations. Together, these findings provide high temporal resolution of late schizont development, reveal priming for intracellular survival prior to egress, and highlight the short lifespan of invasive merozoites and the resulting challenges of studying this elusive stage of the IDC.

microbiology↗

bioRxiv2022

TLR2 axis on peripheral blood mononuclear cells regulates inflammatory responses to circulating, non-infectious immature dengue virus particles

Severe dengue virus (DENV) infection is characterized by exacerbated inflammatory responses that lead to endothelial dysfunction and plasma leakage. We have recently demonstrated that Toll-like receptor 2 (TLR2) on blood monocytes senses DENV infection leading to endothelial activation. Here, we report that non-infectious immature DENV particles, which are released in large numbers by DENV-infected cells, drive endothelial activation via the TLR2 axis. We show that fully immature DENV particles induce a rapid, within 6 hours post-infection, inflammatory response in PBMCs. Furthermore, pharmacological blocking of TLR2/TLR6/CD14 and/or NF-kB prior to exposure of PBMCs to immature DENV reduces the initial production of inter alia TNF- and IL-1{beta} by monocytes and prevents endothelial activation. However, prolonged TLR2 block induces TNF- production and leads to exacerbated endothelial activation, indicating that TLR2-mediated responses play an important role not only in the initiation but also the resolution of inflammation. Altogether, these data indicate that the maturation status of the virus has the potential to influence the kinetics and extent of inflammatory responses during DENV infection. Author SummarySevere dengue virus (DENV) infection is characterized by endothelial dysfunction leading to vascular permeability and plasma leakage. This is thought to be mediated by the exacerbated production of inflammatory mediators from cells of the innate immune system. We have previously demonstrated that Toll-like receptor 2 (TLR2), a pattern recognition receptor present on the surface of human monocytes, can sense DENV infection leading to the activation of the endothelium. Importantly, a large proportion of DENV particles is immature and are not readily infectious. Here we aimed to elucidate if and how these non-infectious immature DENV particles contribute to systemic inflammation. We evaluated if monocytes sense immature DENV and found that sensing of immature DENV induced early inflammatory responses in PBMCs. Pharmacological inhibition of TLR2/TLR6/CD14 and/or NF-{kappa}B prior to exposure to immature DENV demonstrates that this is the pathway leading to the early production inflammatory mediators and endothelial activation. However, prolonged inhibition of TLR2 induced the production of TNF- and the subsequent activation of the endothelium, suggesting that TLR2-mediated responses play an important tole during both, initiation and resolution of inflammation. We propose that the maturation status of DENV in the human host can influence the extent and kinetics of the inflammatory responses during DENV infection.

immunology↗

bioRxiv2021

Differential levels of IFNα subtypes in autoimmunity and viral infection

Type I interferons are essential for host response to viral infections, while dysregulation of their response can result in autoinflammation or autoimmunity. Among IFN (alpha) responses, 13 subtypes exist that signal through the same receptor, but have been reported to have different effector functions. However, the lack of available tools for discriminating these closely related subtypes, in particular at the protein level, has restricted the study of their differential roles in disease. We developed a digital ELISA with specificity and high sensitivity for the IFN2 subtype. Application of this assay, in parallel with our previously described pan-IFN assay, allowed us to study different IFN protein responses following cellular stimulation and in diverse patient cohorts. We observed different ratios of IFN protein responses between viral infection and autoimmune patients. This analysis also revealed a small percentage of autoimmune patients with high IFN2 protein measurements but low pan-IFN measurements. Correlation with an ISG score and functional activity showed that in this small sub group of patients, IFN2 protein measurements did not reflect its biological activity. This unusual phenotype was partly explained by the presence of anti-IFN auto-antibodies in a subset of autoimmune patients. This study reports ultrasensitive assays for the study of IFN proteins in patient samples and highlights the insights that can be obtained from the use of multiple phenotypic readouts in translational and clinical studies.

immunology↗