Biology subjects

Zajonc, D. M.

Publications and source records attributed to Zajonc, D. M..

3 recordsLinked to original sources

bioRxiv2026

CD1a-Mediated Presentation of Canonical Microbial Peptides to T Cells

Langerhans cells express the nonpolymorphic antigen-presenting molecule CD1a, positioning them as contributors to host immunity against Mycobacterium leprae in human leprosy. CD1a was originally shown to present non-canonical lipopeptide antigens such as dideoxymycobactin and chemically diverse hydrophobic ligands. Here, we generated CD4 T cell lines from leprosy lesions that recognized M. leprae in a CD1a-restricted manner. Unexpectedly, antigen recognition was protease-sensitive, prompting biochemical purification that identified two microbial protein antigens: LppX, a 25-kDa lipoglycoprotein, and Ag85A, a 30-kDa secreted protein with no known lipid modification. Recombinant proteins activated the corresponding T cell lines in a CD1a-dependent manner. Epitope mapping identified 12-mer peptides that fully reconstituted antigenicity, were conserved between M. leprae and M. tuberculosis, and elicited robust, dose-dependent IFN-{gamma} production and T cell proliferation, establishing that DNA-encoded, ribosomally translated peptides serve as CD1a-restricted cognate antigens. Biochemical analyses showed peptide binding to CD1a, supported by isoelectric focusing and surface plasmon resonance (KD [~]75 M for Ag85A). CD1a-peptide tetramers specifically stained cognate T cells, soluble CD1a was sufficient to present peptide antigen, and transfer of the LppX-specific TCR into naive T cells restored antigen responsiveness. Using CD1a-peptide tetramers, we identified antigen-specific T cells enriched in patients undergoing reversal reactions compared with patients with lepromatous leprosy and healthy donors. The CD1a-restricted T cell lines secreted IFN-{gamma} and IL-26, cytokines with established antimicrobial activity. Together, these findings demonstrate that CD1a can present canonical microbial peptides as part of a cell-mediated immune response in leprosy, extending the known spectrum of CD1a ligands. Because CD1a is nonpolymorphic and presents antigens to antimicrobial T cells, CD1a-peptide complexes may provide a broadly applicable platform for studying, detecting, and potentially targeting mycobacterial immunity.

immunology↗

bioRxiv2019

Structure of human cytomegalovirus UL144, an HVEM orthologue, bound to the B and T cell Lymphocyte Attenuator

Human cytomegalovirus (HCMV) is a {beta}-herpesvirus that has co-evolved with the host immune system to establish lifelong persistence. HCMV encodes many immune-modulatory molecules, including the glycoprotein UL144. UL144 is a structural mimic of the TNFRSF member HVEM, which binds to various ligands LIGHT, LT, BTLA, CD160 and gD. However, in contrast to HVEM, UL144 selectively binds to only BTLA, inhibiting T cell activation. Here, we report the crystal structure of the UL144/BTLA complex, providing key insights into the molecular mechanisms underlying this virus-host protein interaction. Our structure reveals that UL144 utilizes residues from its N-terminal CRD1 to interact with BTLA in an orientation similar, but not exactly, to that of HVEM. The structural modifications at the CRD1 region of UL144 compared to HVEM have a significant impact on the fine-tuning of BTLA-binding. In addition, the N-terminal CRD2 loop of UL144 is shorter compared to the corresponding region of HVEM, altering the relative orientation of CRD2 with respect to CRD1. Employing structure-guided mutagenesis we have identified a mutant of BTLA (L123A) that interferes with binding to HVEM while preserving interaction towards UL144. Furthermore, our results illuminate structural differences between UL144 and HVEM that explain the inability of UL144 to bind to either LIGHT or CD160. In summary, the specific molecular differences that UL144 has evolved to exclusively target BTLA highlight it as a suitable scaffold for designing superior BTLA agonists that have high potential for potently inhibiting immune responses.\n\nImportanceThe co-evolution of HCMV with its host over millions of years has allowed the virus to develop an efficient and specific immune modulatory protein, UL144, that binds exclusively to an immune inhibitory receptor BTLA. The crystal structure of the UL144/BTLA complex presented in this manuscript provides key insights into the molecular mechanisms underlying the virus-host protein interaction. The structure guided mutagenesis revealed select structural hot spots of the UL144/BTLA interaction. The structural details of this viral protein that has evolved to target only BTLA helps in successful design of BTLA agonists to target various T and B cell mediated autoimmune diseases.

immunology↗

bioRxiv2018

Organized spatial patterns of activated β2 integrins in arresting neutrophils

The transition from leukocyte rolling to firm adhesion is called arrest. {beta}2 integrins are required for neutrophil arrest1. Chemokines can trigger neutrophil arrest in vivo2 and in vitro3. Resting integrins4 exist in a \"bent-closed\" conformation, i.e., not extended (E-) and not high affinity (H-), unable to bind ligand. Electron microscopic images of isolated {beta}2 integrins in \"open\" and \"closed\" conformations5 inspired the switchblade model of integrin activation from E-H- to E+H- to E+H+67. Recently8, we discovered an alternative pathway of integrin activation from E-H- to E-H+ to E+H+. Spatial patterning of activated integrins is thought to be required for effective arrest, but so far only diffraction-limited localization maps of activated integrins exist8. Here, we combine superresolution microscopy with molecular modeling to identify the molecular patterns of H+E-, H-E+, and H+E+ activated integrins on primary human neutrophils. At the time of neutrophil arrest, E+H+ integrins form oriented (non-random) nanoclusters that contain a total of 4,625{+/-}369 E+H+ {beta}2 integrin molecules.

immunology↗