Sarkkinen, J. | Search bioRxiv

bioRxiv2024

HHV-6B, HHV-7, and B19V Are Frequently Found DNA Viruses in the Human Thymus but Show No Definitive Link with Myasthenia Gravis

Myasthenia gravis (MG) is an autoimmune disorder characterised by autoantibodies that target components of the neuromuscular junction, primarily the acetylcholine receptor (AChR), resulting in muscle weakness. The thymus plays a significant role in MG pathogenesis, particularly in patients under the age of 50, who display pathological alterations and possess elements conducive to autoimmune reactions. Although viral infections are suspected drivers of thymic pathogenesis, the exact aetiology of MG remains elusive. This study investigates the potential link between MG and DNA viruses within the thymus. Using targeted next-generation sequencing and quantitative PCR, we analysed the presence of human parvovirus B19 (B19V) and nine human herpesviruses (HSV-1, HSV-2, VZV, EBV, CMV, HHV-6A, HHV-6B, HHV-7, and HHV-8) in fresh tissue samples from 19 non-thymomatous MG patients, 16 thymomas (3 with and 14 without MG), 41 normal thymus tissues, and 20 tonsils from healthy individuals. HHV-6B was the most common virus, found in over 50% of all tissue groups. B19V DNA was detected in 40% of adult control thymic tissue, 72% of MG thymus, 7.7% of non-MG thymoma, and 50% of tonsil samples. HHV-7 was present in 15-30% of thymus tissues and 95% of tonsils, while EBV was detected in less than 25% of all thymus samples but 85% of tonsils. In B19V seropositive individuals, B19V DNA was detected in 100% of thymic tissue from both MG patients and healthy individuals, except in thymomatous tissues, where it was found in only one of thirteen seropositive individuals. Immunohistochemistry for B19V protein expression did not show evident B19V VP1/VP2 protein expression, indicating dormant viral persistence. Laser capture microdissection (LCM) and RNAscope in situ hybridisation pinpointed B19V DNA localisation to the thymus medulla. This study is the first to demonstrate the persistence of various DNA viruses in the human thymus. However, neither B19V nor the nine human herpesviruses showed specific enrichment in MG thymic tissue compared to controls, suggesting that these viral infections are unlikely to be sole environmental triggers for MG.

immunology↗

bioRxiv2023

Single-cell spatial atlas of tertiary lymphoid structures in ovarian cancer

BackgroundRecent advances in highly-multiplexed tissue technologies and image analysis tools have enabled a more detailed investigation of the tumor microenvironment (TME) and its spatial features, including tertiary lymphoid structures (TLSs), at single-cell resolution. TLSs play a major part in antitumor immune responses, however, their role in antitumor immunity in ovarian cancer remains largely unexplored. MethodsIn this study, we generated a comprehensive single-cell spatial atlas of TLSs in ovarian cancer by extracting spatial topology information from in-situ highly-multiplexed cellular imaging using tissue cyclic immunofluorescence (CyCIF). Our analysis included 44 patients with high-grade serous ovarian cancer (HGSC) from the TOPACIO Phase II clinical trial. We combined spatial and phenotypic features from 302,545 single-cells with histopathology, targeted sequencing-based tumor molecular groups, and Nanostring gene expression data. ResultsWe find that TLSs are associated with a distinct TME composition and gene expression profile, characterized by elevated levels of the chemokines CCL19, CCL21, and CXCL13 correlating with the number of TLSs in the tumors. Using single-cell feature quantification and spatial mapping, we uncover enriched germinal center (GC) B cell infiltration and selective spatial attraction to follicular helper T and follicular regulatory T cells in the TLSs from chemo-exposed and BRCA1 mutated HGSCs. Importantly, spatial statistics reveal three main groups of cell-to-cell interactions; significantly enriched structural compartments of CD31+ cells, myeloid, and stromal cell types, homotypic cancer cell- and cancer cell to IBA1+ myeloid cell crosstalk, and enriched selective Tfh, Tfr, and Tfc communities with predominant Tfh - GC B cell interactions. Finally, we report spatiotemporal gradients of GC-B cell interactions during TLS maturation, with enriched non-GC B cell attraction towards the GC B cells in early TLSs, and avoidance patterns with selective GC B-cell communities in the TLSs with GCs. ConclusionsOur single-cell multi-omics analyses of TLSs showed evidence of active adaptive immunity with spatial and phenotypic variations among distinct clinical and molecular subtypes of HGSC. Overall, our findings provide new insights into the spatial biology of TLSs and have the potential to improve immunotherapeutic targeting of ovarian cancer. What is already known on this topicTLSs play a major part in antitumor immune responses, however, their exact role and mechanisms in antitumor immunity are widely unexplored. What this study addsOur results deepen the understanding of TLS biology including cell-cell interactions and shows how the presence of TLSs is characterized with a distinct TME composition and gene expression profile. How this study might affect research, practice or policyOverall, our findings provide new insights into the spatial biology of TLSs and have the potential to improve therapeutic options for ovarian cancer.

cancer biology↗