Biology subjects

Kelsoe, G. H.

Publications and source records attributed to Kelsoe, G. H..

5 recordsLinked to original sources

bioRxiv2026

Genetically restricted human antibodies recognize a conserved β-hairpin in postfusion influenza hemagglutinin

A public class of broadly protective, human antibodies (Abs) binds a conserved {beta}-hairpin exposed in the postfusion conformation of influenza virus hemagglutinin (HA). We here describe use of in vitro immunoassays and high-resolution cryogenic electron microscopy analysis of Ab:HA complexes to explain the apparent genetic restriction of these Abs and the wide range of influenza A and B subtypes they recognize. We show that recognition of the {beta}-hairpin epitope requires 1) germline-encoded residues unique to certain alleles of the human immunoglobulin heavy chain gene IGHV1-2, 2) a short (<14-residue) HCDR3 to avoid steric clash with HA, and 3) several Ab light chain residues that are germline-encoded by various IGLV2-family genes or IGLV7-46. Despite the genetic restrictions, the capacity to make {beta}-hairpin Abs is widespread among humans. We recovered examples of these Abs from 14 genetically unrelated donors, and a previously reported analysis of the IGHV genotypes of ~2,500 individuals sampled from major ethnic populations estimates that >75% of people have the necessary IGHV1-2 alleles to make these Abs. We conclude that an immunogen that displays the {beta}-hairpin epitope might reliably elicit broadly protective influenza antibodies in most humans.

immunology↗

bioRxiv2026

Antibody feedback limits specific B-cell entry and alters germinal center repertoires by antibody-antigen complexes

Antibody (Ab) feedback impacts germinal center (GC) responses. Mice given IgG1 or IgG2c recombinant Ab (rAb) specific for the receptor binding site (RBS) of H3 hemagglutinin (HA) and later immunized with the H3 HA trimer exhibited altered GC repertoires. Passive RBS rAb had no effect on the magnitude of ensuing primary GC responses but reduced the numbers of RBS-specific GC B cells. These losses were matched by increases in "unspecific" B cells which did not bind the HA immunogen, with no changes in B cells specific for distal epitopes. These effects were independent of IgG subclass. Higher doses of passive rAb resulted in reduced epitope-specific affinity maturation and clonal proliferation in GCs. Passive rAb generated Ab:HA complexes and favored recruitment of rare HA-specific GC B cells with enhanced avidity for the rAb:HA immune complex (IC). We show that some no- and low-affinity GC B cells represent responses to local ICs.

immunology↗

bioRxiv2025

Fluorescence-barcoded cell lines stably expressing membrane-anchored influenza neuraminidases

The discovery of broadly protective antibodies to the influenza virus neuraminidase (NA) has raised interest in NA as a vaccine target. However, recombinant, solubilized tetrameric NA ectodomains are often challenging to express and isolate, hindering the study of anti-NA humoral responses. To address this obstacle, we established a panel of 22 non-adherent cell lines stably expressing native, historical N1, N2, N3, N9, and NB NAs anchored on the cell surface. The cell lines are barcoded with fluorescent proteins, enabling high-throughput, 16-plex analyses of antibody binding with commonly available flow cytometers. The cell lines were at least as efficient as a Luminex multiplex binding assay at identifying NA antibodies from a library of unselected clonal IgGs derived from human memory B cells. The cell lines were also useful for measuring the magnitude and breadth of the serum antibody response elicited by experimental infection of rhesus macaques with influenza virus. The membrane-anchored NAs are catalytically active and are compatible with established sialidase activity assays. NA-expressing K530 cell lines therefore represent a useful tool for studying NA immunity and evaluating influenza vaccine efficacy.

immunology↗

bioRxiv2023

A class of antibodies that overcome a steric barrier to cross-group neutralization of influenza viruses

Antibody titers that inhibit the influenza virus hemagglutinin (HA) from engaging its receptor are the accepted correlate of protection from infection. Many potent antibodies with broad, intra-subtype specificity bind HA at the receptor binding site (RBS). One barrier to broad H1-H3 cross-subtype neutralization is an insertion (133a) between positions 133 and 134 on the rim of the H1 HA RBS. We describe here a class of antibodies that overcome this barrier. These genetically unrestricted antibodies are abundant in the human B-cell memory compartment. Analysis of the affinities of selected members of this class for historical H1 and H3 isolates suggest that they were elicited by H3 exposure and broadened or diverted by later exposure(s) to H1 HA. RBS mutations in egg-adapted vaccine strains cause the new H1 specificity of these antibodies to depend on the egg adaptation. The results suggest that suitable immunogens might elicit 133a-independent, H1-H3 cross neutralization by RBS-directed antibodies.

microbiology↗

bioRxiv2022

Infant antibody repertoires during the first two years of influenza vaccination

The first encounter with influenza virus biases later immune responses. This "immune imprinting", formerly from infection within a few years of birth, is in the U.S. now largely from immunization with a quadrivalent, split vaccine (IIV4). In a pilot study of IIV4 imprinting, we characterized, by single-B-cell cultures, NextGen sequencing, and plasma antibody proteomics, the primary antibody responses to influenza in two infants during their first two years of seasonal influenza vaccination. One infant, who received only a single vaccination in Year 1, contracted an influenza B (IBV) infection between the two years, allowing us to compare imprinting by infection and vaccination. That infant had a shift in hemagglutinin (HA)-reactive B-cell specificity from largely influenza A (IAV)-specific in Year 1 to IBV-specific in Year 2, both before and after vaccination. HA-reactive B cells from the other infant maintained a more evenly distributed specificity. In Year 2, class-switched HA-specific B cell IGHV somatic hypermutation (SHM) levels reached average levels seen in adults. The HA-reactive plasma antibody repertoires of both infants comprised a relatively small number of antibody clonotypes, with one or two very abundant clonotypes. Thus, after the Year 2 boost, both infants had overall B cell profiles that resembled those of adult controls. ImportanceInfluenza virus is a moving target for the immune system. Variants emerge that escape protection from antibodies elicited by a previously circulating variant ("antigenic drift"). The immune system usually responds to a drifted influenza virus by mutating existing antibodies rather than by producting entirely new ones. Thus, immune memory of the earliest influenza exposure has a major influence on later responses to infection or vaccination ("immune imprinting"). In the many studies of influenza immunity in adult subjects, imprinting has been from an early infection, since only in the past two decades have infants received influenza immunizations. The work reported in this paper is a pilot study of imprinting in two infants by the flu vaccine, which they received before experiencing an influenza infection. The results suggest that a quadrivalent (four-subtype) vaccine may provide an immune imprint less dominated by one subtype than does a monovalent infection.

immunology↗