Biology subjects

Obraztsova, A.

Publications and source records attributed to Obraztsova, A..

4 recordsLinked to original sources

bioRxiv2023

Memory B cells dominate the early antibody-secreting cell response to SARS-CoV-2 mRNA vaccination in naive individuals independently of their antibody affinity

Memory B cells (MBCs) formed over the individuals lifetime constitute nearly half of the adult peripheral blood B cell repertoire in humans. To assess their response to novel antigens, we tracked the origin and followed the differentiation paths of MBCs in the early anti-S response to mRNA vaccination in SARS-CoV-2-naive individuals on single-cell and monoclonal antibody level. Newly generated and pre-existing MBCs differed in their differentiation paths despite similar levels of SARS-CoV-2 and common corona virus S-reactivity. Pre-existing highly mutated MBCs showed no signs of germinal center re-entry and rapidly developed into mature antibody secreting cells (ASCs). In contrast, newly generated MBCs derived from naive precursors showed strong signs of antibody affinity maturation before differentiating into ASCs. Thus, although pre-existing human MBCs have an intrinsic propensity to differentiate into ASCs, the quality of the anti-S antibody and MBC response improved through the clonal selection and affinity maturation of naive precursors. HighlightsO_LImRNA vaccination of SARS-CoV-2 naive individuals recruits naive and pre-existing MBCs with similar levels of S-reactivity into the response C_LIO_LIS-reactive naive but not pre-existing MBCs undergo affinity maturation C_LIO_LIS-reactive pre-existing MBCs dominate the early ASC response independent of their antigen affinity C_LIO_LIHigh-affinity S-reactive MBCs and ASCs develop over time and originate from affinity matured naive precursors C_LI

immunology↗

bioRxiv2023

Molecular and functional properties of human Plasmodium falciparum CSP C-terminus antibodies

Human monoclonal antibodies (mAbs) against the central repeat and junction domain of Plasmodium falciparum circumsporozoite protein (PfCSP) have been studied extensively to guide malaria vaccine design compared to antibodies against the PfCSP C terminus. Here, we describe the molecular characteristics and protective potential of a panel of 73 germline and mutated human mAbs against the highly immunogenic PfCSP C-terminal domain. Two mAbs recognized linear epitopes in the C-terminal linker with sequence similarity to repeat and junction motifs, whereas all others targeted conformational epitopes in the -thrombospondin repeat (-TSR) domain. Specificity for the polymorphic Th2R/Th3R but not the conserved RII+ region in the -TSR was associated with IGHV3-21/IGVL3-21 or IGLV3-1 gene usage. Although the C terminus specific mAbs showed signs of more efficient affinity maturation and class-switching compared to anti-repeat mAbs, parasite inhibitory activity was limited to a single C-linker reactive mAb with cross-reactivity to the central repeat and junction. The data provide novel insights in the human anti-C-linker and anti--TSR antibody response that support exclusion of the PfCSP C terminus from malaria vaccine designs.

immunology↗

bioRxiv2021

Clonal evolution and specificity of the human T follicular helper cell response to Plasmodium falciparum circumsporozoite protein

T follicular helper (TFH) cells play a crucial role in the development of long-lived, quality-improved B cell responses after infection and vaccination. However, little is known about their clonal evolution. Here we assessed the cell phenotype, clonal dynamics, and TCR specificity of human circulating TFH (cTFH) cells at monoclonal level during successive malaria immunizations with radiation-attenuated Plasmodium falciparum (Pf) sporozoites. Repeated parasite exposures induced a dynamic, polyclonal cTFH response with high frequency of cells specific to the Pf circumsporozoite protein (PfCSP), the main surface protein of sporozoites and a validated vaccine target. Repeated immunizations were required to induce detectable PfCSP-reactive cTFH cell responses to a small number of epitopes. HLA-restrictions and differences in TCR generation probability explain the high targeting frequency of the polymorphic Th2R/T* region over the conserved T1 epitope. The vast majority of anti-Th2R/T* TCRs failed to tolerate natural polymorphisms in their target peptide sequence suggesting that parasite diversity limits natural boosting of the cTFH cell response in endemic areas and protection from non-vaccine strains. Among convergent anti-Th2R/T* TCRs with high sequence similarity, subtle differences in CDR3 composition discriminated cross-reactive from non-cross-reactive cTFH cells. Thus, our study provides deep molecular and cellular insights into the kinetics, fine specificity and HLA-restrictions of the anti-cTFH cell response that are of direct relevance for the design of PfCSP-based malaria vaccines by guiding the selection of PfCSP peptides that induce optimal B cell help.

immunology↗

bioRxiv2019

sumrep: a summary statistic framework for immune receptor repertoire comparison and model validation

The adaptive immune system generates an incredible diversity of antigen receptors for B and T cells to keep dangerous pathogens at bay. The DNA sequences coding for these receptors arise by a complex recombination process followed by a series of productivity-based filters, as well as affinity maturation for B cells, giving considerable diversity to the circulating pool of receptor sequences. Although these datasets hold considerable promise for medical and public health applications, the complex structure of the resulting adaptive immune receptor repertoire sequencing (AIRR-seq) datasets makes analysis difficult. In this paper we introduce sumrep, an R package that efficiently performs a wide variety of repertoire summaries and comparisons, and show how sumrep can be used to perform model validation. We find that summaries vary in their ability to differentiate between datasets, although many are able to distinguish between covariates such as donor, timepoint, and cell type for BCR and TCR repertoires. We show that deletion and insertion lengths resulting from V(D)J recombination tend to be more discriminative characterizations of a repertoire than summaries that describe the amino acid composition of the CDR3 region. We also find that state-of-the-art generative models excel at recapitulating gene usage and recombination statistics in a given experimental repertoire, but struggle to capture many physiochemical properties of real repertoires.

immunology↗