Biology subjects

Alatrash, R.

Publications and source records attributed to Alatrash, R..

5 recordsLinked to original sources

bioRxiv2026

Age-dependent PD-1 induction restricts IL-2-driven effector T cell responses during La Crosse virus infection in mice

Age is a major determinant of disease severity following La Crosse virus (LACV) infection, yet the immunological mechanisms underlying heightened susceptibility in children remains poorly defined. Here, we show that acute LACV infection in weanling mice induces T cell dysfunction characterized by early PD-1 upregulation and impaired effector differentiation despite evidence of activation. This state is associated with reduced IL-2-dependent STAT5 signaling, indicating a failure to respond to available cytokine cues. Although regulatory T cells expand and exhibit elevated CD25 expression, their depletion increases IL-2 levels without restoring antiviral T cell responses or viral control. In contrast, PD-1 blockade partially restores T cell activation, and combined PD-1 blockade with CD25 targeting enables robust effector differentiation and improved viral control. These findings demonstrate that checkpoint signaling limits T cell responsiveness to IL-2, uncoupling activation from differentiation and driving age-dependent susceptibility to LACV infection.

immunology↗

bioRxiv2025

Pre-existing YFV-17D immunity mediates T cell cross-protection against DENV-2 infection

Widespread yellow fever virus (YFV) immunity in Sub-Saharan Africa may mitigate orthoflavivirus outbreaks. Here, we investigate whether pre-existing YFV-17D immunity confers cross-protection against dengue virus serotype 2 (DENV-2) in a murine model. IFNAR1-/- mice immunized with YFV-17D exhibited significantly reduced DENV-2 viremia, weight loss, and disease severity, with improved survival compared to YFV-naive controls. Mechanistic studies revealed that cross-protection was mediated by heterologous T cell responses rather than cross-neutralizing antibodies. Depletion of T cells in YFV-17D-immune mice prior to DENV-2 challenge resulted in increased viremia, weight loss, and disease severity, underscoring the protective role of YFV-17D-elicited T cell immunity. Furthermore, YFV-17D-specific T cells displayed cytotoxicity against DENV NS3- and NS5-pulsed cells, demonstrating their functional role in viral control. These findings highlight the critical contribution of heterologous T cell immunity in YFV-17D-mediated protection against DENV-2 and suggest that vaccines designed to elicit T cell responses could enhance cross-protection against orthoflavivirus infections.

immunology↗

bioRxiv2025

Immunodominant structural proteins Gc and N drive T cell-mediated protection against La Crosse virus

La Crosse virus (LACV) is a major cause of pediatric encephalitis in the U.S., primarily affecting children under 16 years. Despite severe morbidity and potential mortality risks, no vaccines or antivirals exist. Murine models recapitulate human susceptibility patterns, with weanling mice (3 weeks old) succumbing to disease while adults ([≥]8 weeks old) exhibit resistance. We characterized the T cell responses underlying this difference. Adult mice mounted robust CD4+ and CD8+ T cell responses by 6 days post-infection (dpi), with sustained IFN-{gamma}, granzyme B, IL-2, and TNF- production. These T cells expanded significantly and exhibited in vivo cytotoxicity against cells pulsed with LACV glycoprotein (Gc) and nucleocapsid (N) antigens. In contrast, weanlings showed weak T cell responses and 100% mortality by 7 dpi. Immunization with LFn-LACV-Gc and -N improved T cell cytotoxicity and survival in weanlings, highlighting their potential as vaccines. These findings inform strategies to mitigate LACV-induced encephalitis in children.

immunology↗

bioRxiv2025

Development of an RT-RPA assay for La Crosse virus detection provides insights into age-dependent neuroinvasion in mice

BackgroundLa Crosse virus (LACV) is a mosquito-borne arbovirus responsible for pediatric encephalitis in North America, predominantly affecting children under 16 years. Early and accurate diagnosis is critical to reducing morbidity in this vulnerable population. However, existing molecular and serological methods are limited in sensitivity, specificity, and accessibility. MethodsTo address these limitations, we developed a reverse transcription recombinase polymerase amplification (RT-RPA) assay for LACV detection. Primers targeting the divergent M segment of the LACV genome were designed and screened for optimal performance. The assays analytical sensitivity was evaluated through serial dilutions of LACV RNA prior to reverse transcription, while specificity was assessed using reverse transcribed RNA from related or geographically relevant arboviruses. We further adapted the RT-RPA test into a lateral flow assay (LFA) format for potential point-of-care use. Additionally, we employed a murine model to explore the age-dependent dynamics of LACV neuroinvasion and clearance, with the virus detected using RT-RPA and reverse transcription quantitative polymerase change reaction (RT-qPCR). ResultsPrimer screening identified an optimal primer pair that amplified LACV cDNA within 20 minutes at 39{degrees}C, with a limit of detection (LOD) of 100 copies. The assay demonstrated high specificity, with no amplification of related or other geographically relevant arboviruses. Integration of the RT-RPA test into an LFA format preserved the LOD and specificity, enabling visual detection via test strips. In the murine model, weanling mice exhibited LACV neuroinvasion as early as 4 days post-infection (dpi), with sustained detection between 5-7 dpi. In adult mice, neuroinvasion was first detected at 5 dpi, plateauing between 6-10 dpi, and cleared entirely by 20 dpi in surviving animals. ConclusionsThis study establishes the RT-RPA assay as an efficient, specific, and sensitive diagnostic platform for LACV, with potential for adaptation into field-deployable LFA tests. Moreover, our findings provide valuable insights into the age-dependent dynamics of LACV neuroinvasion and clearance, informing future diagnostic and therapeutic strategies.

microbiology↗

bioRxiv2024

Age-specific dynamics of neutralizing antibodies, cytokines, and chemokines in response to La Crosse virus infection in mice

La Crosse virus (LACV) is a primary cause of pediatric arboviral encephalitis in the United States, particularly affecting children aged 16 years or younger. This age-related susceptibility extends to murine models, where weanling mice (3 weeks old) succumb to LACV infection, while adults ([≥]6 weeks old) demonstrate resistance. Despite its clinical relevance, the host immune response to LACV is not fully understood. In this study, we investigated the roles of neutralizing antibodies (nAbs), cytokines, and chemokines in weanling and adult mice following infection with 5x105 plaque forming units (PFU) of LACV. We observed significant age-related differences in viral titers and survival. Weanling mice demonstrated early disease onset with elevated peripheral viremia, but passive transfer of adult serum, confirmed to have nAbs, to naive weanlings prior to infection completely rescued them from death. Cytokine and chemokine profiling revealed distinct kinetics and age-specific immune responses. Adult mice had increased Th1 cytokines, Th9/Th17/Th22/Treg cytokines, and many chemokines. In contrast, weanlings had higher Th2 cytokines, correlating with symptoms onset. Flow cytometry and intracellular cytokine staining further demonstrated that weanling mice produced higher levels of IL-4 by CD4+ and CD8+ T cells compared to adults, regardless of infection status. Conversely, LACV-infected adult mice had increased IFN-{gamma} production by CD8+ T cells compared to uninfected adults. Finally, adoptive transfer of splenocytes from immune adult mice to naive weanlings delayed neurological symptoms and improved survival, highlighting the protective role of immune adult cells against LACV. In conclusion, this study links nAbs and cytokine and chemokine responses to protective immunity in adult mice, contrasting with the pathogenesis seen in weanlings. These findings underscore the importance of further research into innate and adaptive immune mechanisms in LACV infection.

microbiology↗