Biology subjects

Gonzales, C.

Publications and source records attributed to Gonzales, C..

3 recordsLinked to original sources

bioRxiv2023

Differential cellular immune responses against Orientia tsutsugamushi Karp and Gilliam strains following acute infection in mice

Scrub typhus is the leading source of febrile illness in endemic countries due to infection with Orientia tsutsugamushi (Ot), a seriously understudied intracellular bacterium. Pulmonary complications in patients are common and can develop into life threatening conditions. The diverse antigenicity of Ot genotypes and inter-strain differences seem to be connected to varied virulence and clinical outcomes; however, detailed studies of strain-related pulmonary immune responses in human patients or experimental animals are lacking. In this study, we used two clinically prevalent bacterial strains, Karp and Gilliam, and revealed cellular immune responses in inflamed lungs and potential biomarkers of disease severity. We found that outbred CD-1 mice were highly susceptible to both Karp and Gilliam strains; however, C57BL/6 (B6) mice were susceptible to Karp, but resistant to Gilliam (with self-limiting infection), corresponding to their tissue bacterial burdens and lung pathological changes. Multicolor flow cytometric analyses of perfused B6 mouse lungs revealed robust and sustained influx and activation of innate immune cells (monocytes, macrophages, neutrophils, and NK cells), followed by those of CD4+ and CD8+ T cells, during Karp infection, but such responses were greatly attenuated during Gilliam infection. The robust cellular responses in Karp-infected B6 mice were positively correlated with significantly early and high levels of serum cytokine/chemokine protein levels (CXCL1, CCL2/3/5, and G-CSF), as well as pulmonary gene expression (CXCL1/2, CCL2/3/4, and IFN{gamma}). In vitro infection of B6 mouse-derived primary macrophages also revealed bacterial strain-dependent immune gene expression profiles. This study provided the first lines of evidence that highlighted differential tissue cellular responses against Karp vs. Gilliam infection, offering a framework for future investigation of Ot strain-related mechanisms of disease pathogenesis vs. infection control. Authors SummaryOrientia tsutsugamushi (Ot) infection-induced scrub typhus is a leading cause of febrile illness in endemic countries. Research on Ot strain-related disease outcomes or immune signatures in tissue and blood samples is very limited. Using two clinically prevalent strains (Karp and Gilliam), we examined host susceptibility in inbred and outbred mouse models and provided new evidence for the activation of pulmonary immune cell subsets during the acute stages of infection. While Gilliam-infected C57BL/6 (B6) mice developed self-limiting infection, mild cellular responses, and tissue injury, Karp infection led to a strong and sustained activation of innate immune cells, followed by extensive influx of activated T cells, which correlated to protein levels of inflammatory cytokines/chemokines in serum samples. We also provided in vitro evidence for Ot strain-dependent immune gene profiles, indicating differential macrophage responses to Karp versus Gilliam bacteria. This is the first comparison of different scrub typhus mouse models with in-depth analyses of cellular responses in inflamed lungs, offering novel insights into potential mechanisms of disease progression versus infection control related to Ot strains and laying the foundation for future investigations.

immunology↗

bioRxiv2023

Alterations in Germinal Center Formation and B Cell Activation during Severe Orientia tsutsugamushi Infection in Mice

Scrub typhus is a poorly studied but life-threatening disease caused by the intracellular bacterium Orientia tsutsugamushi (Ot). Cellular and humoral immunity in Ot-infected patients is not long-lasting, waning as early as one-year post-infection; however, its underlying mechanisms remain unclear. To date, no studies have examined germinal center (GC) or B cell responses in Ot-infected humans or experimental animals. This study was aimed at evaluating humoral immune responses at acute stages of severe Ot infection and possible mechanisms underlying B cell dysfunction. Following inoculation with Ot Karp, a clinically dominant strain known to cause lethal infection in C57BL/6 mice, we measured antigen-specific antibody titers, revealing IgG2c as the dominant isotype induced by infection. Splenic GC responses were evaluated by immunohistology, co-staining for B cells (B220), T cells (CD3), and GCs (GL-7). Organized GCs were evident at day 4 post-infection (D4), but they were nearly absent at D8, accompanied by scattered T cells throughout splenic tissues. Flow cytometry revealed comparable numbers of GC B cells and T follicular helper (Tfh) cells at D4 and D8, indicating that GC collapse was not due to excessive death of these cell subtypes at D8. B cell RNAseq analysis revealed significant differences in expression of genes associated with B cell adhesion and co-stimulation at D8 versus D4. The significant downregulation of S1PR2 (a GC-specific adhesion gene) was most evident at D8, correlating with disrupted GC formation. Signaling pathway analysis uncovered downregulation of 71% of B cell activation genes at D8, suggesting attenuation of B cell activation during severe infection. This is the first study showing the disruption of B/T cell microenvironment and dysregulation of B cell responses during Ot infection, which may help understand the transient immunity associated with scrub typhus. Author SummaryScrub typhus is an understudied disease caused by the intracellular bacterium O. tsutsugamushi. A hallmark of scrub typhus is the unexplained, non-durable immunity after infection. While cellular immune responses are known to be important for controlling this infection, our understanding of B cell and GC responses remains limited. In this study, we examined B cell activation and GC responses using our recently established murine model of severe scrub typhus. We measured bacterial antigen-specific antibody titers and identified IgG2c, an IFN-{gamma}-driven isotype, as the major IgG subtype. We also found that O. tsutsugamushi infection disrupted spleen morphology, exemplified by randomly dispersed T cells and lost GC structures. Transcriptomic analysis of purified splenic B cells demonstrated reduced expression of genes encoding critical adhesion and co-stimulation molecules, including GC-adhesion gene S1PR2, at severe stages of infection. Several humoral immune response pathways relevant to B cell receptor signaling, B cell activation and differentiation were significantly downregulated during infection. This study is the first report describing humoral immunity in a scrub typhus mouse model and provides detailed evidence that B cell and GC responses are impaired during acute infection.

immunology↗

bioRxiv2022

Beyond winglets: evolution of flight-related morphology in stick insects (Phasmatodea)

The first winged insects evolved from a wingless ancestor, but details of the transition to a fully-winged morphology remain unclear. Studying extant pterygotes with partial wings, such as the stick insects (Order Phasmatodea), may help us to understand such a transition. Here, we address how a series of flight-related morphological parameters may correlate with flight evolution by studying different phasmids representing a volancy continuum ranging from miniaturized to full-sized wings. Variation in phasmid wing shape, venation, wing mass and the mass of flight muscle can be described by specific scaling laws referenced to wing length and wing loading. Also, the mass distribution of the body-leg system is conserved in spite of a wide range of variation in body shape. With reduced wing size and increased wing loading, the longitudinal position of the wing-bearing thoracic segments is shifted closer to the insects center of body mass. These results demonstrate complex reconfiguration of the flight system during wing morphological transitions in phasmids, with various anatomical features potentially correlated with reduced flight performance attained with partial wings. Although these data represent phasmid-specific features of the flight apparatus and body plan, the associated scaling relationships can provide insight into functionality of intermediate conditions between wingless and fully-winged insects more generally.

evolutionary biology↗