Biology subjects

Ljunggren, H.-G.

Publications and source records attributed to Ljunggren, H.-G..

10 recordsLinked to original sources

bioRxiv2025

From Structure to Immunogenicity: Decoding Correlated Dynamics atthe Peptide MHC interface to Understand TCR Recognition

The interaction between a class I peptide-major histocompatibility complex (pMHC) and a T cell receptor (TCR) plays a central role in the elicitation of CD8+ T cell immune responses. As a result, considerable effort has been invested in understanding the structural, dynamic, and biophysical parameters that govern this recognition event, including designing altered peptide ligands (APLs) which seek to modulate the downstream signaling outcomes. However, dynamic links between modified peptide positions and distant residues have until yet been ill resolved. Using an integrative approach combining crystallographic ensemble and single models with atomistic molecular dynamics simulations and correlational analysis, we have established an approach that allows us to identify coupled dynamics between spatially distant residues at the pMHC interface. Furthermore, we constructed a network encoding the inter-residue couplings observed throughout the simulations. This computational workflow corroborates well with experimental data and leads to novel insights regarding the differential immunogenicity of the closely related peptides analyzed in this study. Ultimately, we present an intuitive and comprehensive strategy for decoding the linked dynamics at the pMHC interface allowing for mechanistic insights into the biophysical bases governing immunogenicity. One Sentence SummaryThe dynamics at the pMHC interface can be encoded as a biophysically relevant network to yield molecular insights into immunogenicity

immunology↗

bioRxiv2025

SAXS reveals the molecular basis underlying pH-driven G3BP1 conformational dynamics: implications for stress granule formation

G3BP1 is the central node and molecular switch in stress granule (SG) assembly. However, structural insights into full-length G3BP1 remain elusive owing to its extensive intrinsically disordered regions (IDRs). Using size-exclusion chromatography-coupled small-angle X-ray scattering (SEC-SAXS), we have characterized the solution architecture and conformational dynamics of full-length G3BP1. Under physiological conditions, G3BP1 adopts an elongated, head-to-head antiparallel homodimeric conformation, whereas acidification induces a pronounced conformational compaction. Subsequent biophysical studies reveal that this compact state enables robust RNA-mediated and, notably, homotypic phase separation in vitro. Deletion of the RGG region abolishes this acidity-induced compaction and markedly impairs phase separation, establishing a causal link between the RGG-dependent conformational switch and phase separation propensity. By moving beyond hypothetical models to experimental solution-state data, our work fills a longstanding void in the field and provides critical insights into the structural plasticity that underlies G3BP1 function, offering a missing structural link essential for deciphering the molecular mechanism of SG formation. We propose that stress-associated physicochemical changes, specifically localized acidification coupled with mRNA accumulation, trigger this reversible structural reconfiguration of G3BP1, thereby facilitating phase separation.

molecular biology↗

bioRxiv2025

Development of DARPin T cell engagers for specific targeting of tumor-associated HLA/peptide complexes

The compromise between affinity and specificity in TCR-dependent targeting of HLA-restricted tumor-associated antigens presents a significant challenge in developing efficacious immunotherapies. As such, T cell engagers which circumvent these limitations are of particular interest. We have established a process to generate bispecific Designed Ankyrin Repeat Proteins (DARPins) that simultaneously target HLA-I molecules in complex with tumor-associated peptides and CD3{varepsilon}. High-affinity HLA-A*0201/NY-ESO1157-165-specific DARPins were isolated after only four rounds of in-vitro selection from naive DARPin libraries. Combining HLA-A*0201/NY-ESO1157-165-specific DARPins with a CD3{varepsilon}-specific DARPin created potent T cell engagers which elicited CD8+ T cell activation towards tumor targets with high peptide specificity, as confirmed by X-scanning mutagenesis and functional killing assays. The cryo-EM structure of a ternary DARPin/HLA-A*0201/NY-ESO1157-165 complex revealed a rigid and concave DARPin surface that binds to the entire length of the peptide-binding cleft, contacting both -helices and the peptide. The present results unveil promising immuno-oncotherapeutic approaches with the possibility of rapidly developing DARPins with high affinity and specificity to HLA/peptide targets that can be readily combined with a new generation of anti-CD3{varepsilon}-specific DARPins.

synthetic biology↗

bioRxiv2024

Crystallographic and NMR studies of Streptococcus pneumonia LCP protein PsrSp indicate the importance of dynamics in four long loops for ligand specificity

The crystal structure of the extracellular region of the second pneumococcal LCP, a polyisoprenyl-teichoic acid-peptidoglycan teichoic acid transferase PsrSp, was determined and refined to 2.15[A] resolution. Despite the low sequence homology with other LCP proteins, the PsrSp maintains the fold of the LCP domain and the positions of the 15 residues suggested to participate in the transferase function are conserved. The empty tunnel found in the PsrSp between the central {beta}-sheet and three -helices is wide enough to accommodate polyisoprenyl-teichoic acid. Comparison of the crystallographic temperature factors of LCP from distinct bacteria demonstrated that the four long loops located close to the teichoic acid and peptidoglycan binding sites have different relative mobility. To compare the dynamics of the PsrSp in crystalline state and in solution, NMR spectra were recorded, and 88% of the residues were assigned in the 1H-15N TROSY HSQC spectra. Comparison of the secondary structure of the crystal structure of PsrSp with NMR data demonstrated a perfect concordance between the results using these two methods. Moreover, the relative mobility of the essential loops estimated from the crystallographic B-factor is in good agreement with order parameter S2, predicted from chemical shift. We hypothesize that the dynamics of these loops are important for the substrate promiscuity of LCP proteins.

microbiology↗

bioRxiv2024

Human NK cell responses to the SARS-CoV-2 Spike269-277 peptide YLQPRTFLL

Natural killer (NK) cells act as the first line of defense against virus infections. The effector functions of human NK cells are controlled by inhibitory and activating receptors, including NKG2A and NKG2C, which recognize peptides presented by HLA-E. Recent studies have suggested that the SARS-CoV-2 Spike269-277 peptide YLQPRTFLL may modulate NK cell activity. Here, we show that the YLQPRTFLL peptide is poorly presented by HLA-E. Functional interrogation further revealed that loading of target cells with YLQPRTFLL did not affect the effector functions of NKG2A+ nor NKG2C+ NK cells. Our findings thus indicate that the Spike269-277 peptide YLQPRTFLL has a limited influence on human NK cell responses.

immunology↗

bioRxiv2021

Longitudinal characterization of humoral and cellular immunity in hospitalized COVID-19 patients reveal immune persistence up to 9 months after infection

BackgroundInsights into early, specific humoral and cellular responses to infection with SARS-CoV-2, as well as the persistence and magnitude of resulting immune memory is important amidst the ongoing pandemic. The combination of humoral and cellular immunity will most likely contribute to protection from reinfection or severe disease. MethodsHere, we conducted a longitudinal study on hospitalized moderate and severe COVID-19 patients from the acute phase of disease into convalescence at five- and nine-months post symptom onset. Utilizing flow cytometry, serological assays as well as B cell and T cell FluoroSpot assays, we assessed the magnitude and specificity of humoral and cellular immune memory during and after human SARS-CoV-2 infection. FindingsDuring acute COVID-19, we observed an increase in germinal center activity, a substantial expansion of antibodysecreting cells, and the generation of SARS-CoV-2-neutralizing antibodies. Despite gradually decreasing antibody levels, we show persistent, neutralizing antibody titers as well as robust specific memory B cell responses and polyfunctional T cell responses at five- and nine-months after symptom onset in both moderate and severe COVID-19 patients. Long-term SARS-CoV-2 specific responses were marked by preferential targeting of spike over nucleocapsid protein. ConclusionsOur findings describe the initiation and, importantly, persistence of cellular and humoral SARS-CoV-2 specific immunological memory in hospitalized COVID-19 patients long after recovery, likely contributing towards protection against reinfection.

immunology↗

bioRxiv2021

Distinct lung-homing receptor expression and activation profiles on NK cell and T cell subsets in COVID-19 and influenza

Respiratory viral infections with SARS-CoV-2 or influenza viruses commonly induce a strong infiltration of immune cells into the lung, with potential detrimental effects on the integrity of the lung tissue. Despite comprising the largest fractions of circulating lymphocytes in the lung, little is known about how blood natural killer (NK) cells and T cell subsets are equipped for lung-homing in COVID-19 and influenza. Using 28-colour flow cytometry and re-analysis of published RNA-seq datasets, we provide a detailed comparative analysis of NK cells and T cells in peripheral blood from moderately sick COVID-19 and influenza patients, focusing on the expression of chemokine receptors known to be involved in leukocyte recruitment to the lung. The results reveal a predominant role for CXCR3, CXCR6, and CCR5 in COVID-19 and influenza patients, mirrored by scRNA-seq signatures in peripheral blood and bronchoalveolar lavage from publicly available datasets. NK cells and T cells expressing lung-homing receptors displayed stronger phenotypic signs of activation as compared to cells lacking lung-homing receptors, and activation was overall stronger in influenza as compared to COVID-19. Together, our results indicate migration of functionally competent CXCR3+, CXCR6+, and/or CCR5+ NK cells and T cells to the lungs in moderate COVID-19 and influenza patients, identifying potential common targets for future therapeutic interventions in respiratory viral infections. Author summaryThe composition of in particular CXCR3+ and/or CXCR6+ NK cells and T cells is altered in peripheral blood upon infection with SARS-CoV-2 or influenza virus in patients with moderate disease. Lung-homing receptor-expression is biased towards phenotypically activated NK cells and T cells, suggesting a functional role for these cells co-expressing in particular CXCR3 and/or CXCR6 upon homing towards the lung.

immunology↗

bioRxiv2020

Robust T cell immunity in convalescent individuals with asymptomatic or mild COVID-19

ABSTRACTSARS-CoV-2-specific memory T cells will likely prove critical for long-term immune protection against COVID-19. We systematically mapped the functional and phenotypic landscape of SARS-CoV-2-specific T cell responses in a large cohort of unexposed individuals as well as exposed family members and individuals with acute or convalescent COVID-19. Acute phase SARS-CoV-2-specific T cells displayed a highly activated cytotoxic phenotype that correlated with various clinical markers of disease severity, whereas convalescent phase SARS-CoV-2-specific T cells were polyfunctional and displayed a stem-like memory phenotype. Importantly, SARS-CoV-2-specific T cells were detectable in antibody-seronegative family members and individuals with a history of asymptomatic or mild COVID-19. Our collective dataset shows that SARS-CoV-2 elicits robust memory T cell responses akin to those observed in the context of successful vaccines, suggesting that natural exposure or infection may prevent recurrent episodes of severe COVID-19 also in seronegative individuals.Competing Interest StatementThe authors have declared no competing interest.View Full Text

immunology↗

bioRxiv2020

Expansion of SARS-CoV-2-specific Antibody-secreting Cells and Generation of Neutralizing Antibodies in Hospitalized COVID-19 Patients

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged in late 2019 and has since become a global pandemic. Pathogen-specific antibodies are typically a major predictor of protective immunity, yet B cell and antibody responses during COVID-19 are not fully understood. Here, we analyzed antibody-secreting cell (ASC) and antibody responses in twenty hospitalized COVID-19 patients. The patients exhibited typical symptoms of COVID-19, and presented with reduced lymphocyte numbers and increased T cell and B cell activation. Importantly, we detected an expansion of SARS-CoV-2 nucleocapsid protein-specific ASCs in all twenty COVID-19 patients using a multicolor FluoroSpot assay. Out of the 20 patients, 16 had developed SARS-CoV-2-neutralizing antibodies by the time of inclusion in the study. SARS-CoV-2-specific IgA, IgG and IgM antibody levels positively correlated with SARS-CoV-2-neutralizing antibody titers, suggesting that SARS-CoV-2-specific antibody levels may reflect the titers of neutralizing antibodies in COVID-19 patients during the acute phase of infection. Lastly, we showed that interleukin 6 (IL-6) and C-reactive protein (CRP) concentrations were higher in serum of patients who were hospitalized for longer, supporting the recent observations that IL-6 and CRP could be used to predict COVID-19 severity. Altogether, this study constitutes a detailed description of clinical and immunological parameters in twenty COVID-19 patients, with a focus on B cell and antibody responses, and provides tools to study immune responses to SARS-CoV-2 infection and vaccination.

immunology↗

bioRxiv2019

High-dimensional analysis reveals a distinct population of adaptive-like tissue-resident NK cells in human lung

Human adaptive-like “memory” CD56dimCD16+ NK cells in peripheral blood from cytomegalovirus-seropositive individuals have been extensively investigated in recent years and are currently explored as a treatment strategy for hematological cancers. However, treatment of solid tumors remains limited due to insufficient NK cell tumor infiltration, and it is unknown whether large expansions of adaptive-like NK cells that are equipped for tissue-residency and tumor-homing exist in peripheral tissues. Here, we show that human lung and blood contains adaptive-like CD56brightCD16− NK cells with hallmarks of tissue-residency, including expression of CD49a. Expansions of adaptive-like lung tissue-resident (tr)NK cells were found to be present independently of adaptive-like CD56dimCD16+ NK cells and to be hyperresponsive towards target cells. Together, our data demonstrate that phenotypically, functionally, and developmentally distinct subsets of adaptive-like NK cells exist in human lung and blood. Given their tissue-related character and hyperresponsiveness, human lung adaptive-like trNK cells might represent a suitable alternative for therapies targeting solid tumors.Competing Interest StatementThe authors have declared no competing interest.Abbreviations:EomesEomesoderminFITCFluorescein isothiocyanateHCMVHuman cytomegalovirusILCInnate lymphoid cellKIRKiller cell immunoglobulin-like receptorNKNatural killerPEPhycoerythrinROSReactive oxygen speciesView Full Text

immunology↗