Access to ultra-long IgG CDRH3 bovine antibody sequences using short read sequencing technology

Investigating the IgM and IgG B Cell Receptor Repertoires and Expression of Ultralong Complementarity Determining Region 3 in Colostrum and Blood from Holstein-Friesian Cows at Calving

In cattle, colostral maternal immunoglobulins and lymphocytes transfer across the neonate's intestinal epithelium to provide protection against pathogens. This study aimed to compare repertoires of B cell populations in blood and colostrum in cows for the first time, with an emphasis on ultralong complementarity determining region 3 (CDR3, ≥40 amino acids). Blood mononuclear cells (BMCs, n= 7) and colostral cells (n = 7) were isolated from Holstein-Friesian dairy cows. Magnetic-activated cell sorting was used to capture IgM and IgG B cells from BMCs. Colostral cells were harvested by centrifugation. RNA was extracted and cDNA was produced; IgM and IgG transcripts were amplified using polymerase chain reactions. Amplicons were sequenced using the Nanopore Native barcoding kit 24 V14 and MinION with R10.4 flow cells. In colostrum, there was a significantly greater percentage of IgM B cells with ultralong CDR3s (8.09% ± 1.73 standard error of the mean) compared to blood (4.22% ± 0.70, p = 0.05). There was a significantly greater percentage of IgG B cells in colostrum with ultralong CDR3s (12.98% ± 1.98) compared to blood (6.61% ± 1.11, p = 0.05). A higher percentage of IgM and IgG B cells with ultralong CDR3s in colostrum may be indicative of a potential role in protecting the neonate.

Estimates of Sequences with Ultralong and Short CDR3s in the Bovine IgM B Cell Receptor Repertoire Using the Long-read Oxford Nanopore MinION Platform

Cattle produce Abs with an H chain ultralong CDR3 (40-70 aa). These Abs have been shown to have features such as broad neutralization of viruses and are investigated as human therapeutics. A common issue in sequencing the bovine BCR repertoire is the sequence length required to capture variable (V) and isotype gene information. This study aimed to assess the use of Oxford Nanopore Technologies' MinION platform to perform IgM BCR repertoire sequencing to assess variation in the percentage of ultralong CDR3s among dairy cattle. Blood was collected from nine Holstein heifers. B cells were isolated using magnetic bead-based separation, RNA was extracted, and IgM+ transcripts were amplified using PCR and sequenced using a MinION R10.4 flow cell. The distribution of CDR3 lengths was trimodal, and the percentage of ultralong CDR3s ranged among animals from 2.32 to 20.13% in DNA sequences and 1.56% to 17.02% in productive protein sequences. V segment usage varied significantly among heifers. Segment IGHV1-7, associated with ultralong CDR3s, was used in 5.8-24.2% of sequences; usage was positively correlated with ultralong CDR3 production (r = 0.99, p < 0.01). To our knowledge, this is the first study to sequence the bovine BCR repertoire using Oxford Nanopore Technologies and demonstrates the potential for cost-efficient long-read repertoire sequencing in cattle without assembly. Findings from this study support literature describing the distribution of length and percentage of ultralong CDR3s. Future studies will investigate changes in the bovine BCR repertoire associated with age, antigenic exposure, and genetics.

De novo genome assembly depicts the immune genomic characteristics of cattle

Immunogenomic loci remain poorly understood because of their genetic complexity and size. Here, we report the de novo assembly of a cattle genome and provide a detailed annotation of the immunogenomic loci. The assembled genome contains 143 contigs (N50 ~ 74.0 Mb). In contrast to the current reference genome (ARS-UCD1.2), 156 gaps are closed and 467 scaffolds are located in our assembly. Importantly, the immunogenomic regions, including three immunoglobulin (IG) loci, four T-cell receptor (TR) loci, and the major histocompatibility complex (MHC) locus, are seamlessly assembled and precisely annotated. With the characterization of 258 IG genes and 657 TR genes distributed across seven genomic loci, we present a detailed depiction of immune gene diversity in cattle. Moreover, the MHC gene structures are integrally revealed with properly phased haplotypes. Together, our work describes a more complete cattle genome, and provides a comprehensive view of its complex immune-genome.

A Customizable Suite of Methods to Sequence and Annotate Cattle Antibodies

Studying the antibody response to infection or vaccination is essential for developing more effective vaccines and therapeutics. Advances in high-throughput antibody sequencing technologies and immunoinformatic tools now allow the fast and comprehensive analysis of antibody repertoires at high resolution in any species. Here, we detail a flexible and customizable suite of methods from flow cytometry, single cell sorting, heavy and light chain amplification to antibody sequencing in cattle. These methods were used successfully, including adaptation to the 10x Genomics platform, to isolate native heavy-light chain pairs. When combined with the Ig-Sequence Multi-Species Annotation Tool, this suite represents a powerful toolkit for studying the cattle antibody response with high resolution and precision. Using three workflows, we processed 84, 96, and 8313 cattle B cells from which we sequenced 24, 31, and 4756 antibody heavy-light chain pairs, respectively. Each method has strengths and limitations in terms of the throughput, timeline, specialist equipment, and cost that are each discussed. Moreover, the principles outlined here can be applied to study antibody responses in other mammalian species.

Exploring the sheep (Ovis aries) immunoglobulin repertoire by next generation sequencing

Next-generation sequencing (NGS) has revolutionized the way we determine the antibody repertoires encoded by B cells in the blood or lymphoid organs and transformed our understanding of adaptive immune responses in many species. Sheep (Ovis aries) have been widely used as a host for therapeutic antibody production since the early 1980s, however, little is known about their immune repertoires or immunological processes affecting the antibody generation. The objective of this study was to employ NGS for a comprehensive analysis of immunoglobulin heavy and light chain repertoires in four healthy sheep. We obtained > 90 % complete antibody sequences and nearly 130,000, 48,000 and 218,000 unique CDR3 reads for the heavy chain (IGH), kappa chain (IGK), and lambda chain (IGL) loci, respectively. Consistent with other species, we observed biased usage of germline variable (V), diversity (D) and joining (J) genes in the heavy and kappa loci, but not in the lambda loci. Moreover, the enormous diversity of CDR3 sequences was observed through sequence clustering and convergent recombination. These data will build a foundation for future studies investigating immune repertoires in health and disease as well as contribute to further refinement of ovine-derived therapeutic antibody drugs.

Evolution of surrogate light chain in tetrapods and the relationship between lengths of CDR H3 and VpreB tails

In the mammalian immune system, the surrogate light chain (SLC) shapes the antibody repertoire during B cell development by serving as a checkpoint for production of functional heavy chains (HC). Structural studies indicate that tail regions of VpreB contact and cover the third complementarity-determining region of the HC (CDR H3). However, some species, particularly bovines, have CDR H3 regions that may not be compatible with this HC-SLC interaction model. With immense structural and genetic diversity in antibody repertoires across species, we evaluated the genetic origins and sequence features of surrogate light chain components. We examined tetrapod genomes for evidence of conserved gene synteny to determine the evolutionary origin of VpreB1, VpreB2, and IGLL1, as well as VpreB3 and pre-T cell receptor alpha (PTCRA) genes. We found the genes for the SLC components (VpreB1, VpreB2, and IGLL1) only in eutherian mammals. However, genes for PTCRA occurred in all amniote groups and genes for VpreB3 occurred in all tetrapod groups, and these genes were highly conserved. Additionally, we found evidence of a new VpreB gene in non-mammalian tetrapods that is similar to the VpreB2 gene of eutherian mammals, suggesting VpreB2 may have appeared earlier in tetrapod evolution and may be a precursor to traditional VpreB2 genes in higher vertebrates. Among eutherian mammals, sequence conservation between VpreB1 and VpreB2 was low for all groups except rabbits and rodents, where VpreB2 was nearly identical to VpreB1 and did not share conserved synteny with VpreB2 of other species. VpreB2 of rabbits and rodents likely represents a duplicated variant of VpreB1 and is distinct from the VpreB2 of other mammals. Thus, rabbits and rodents have two variants of VpreB1 (VpreB1-1 and VpreB1-2) but no VpreB2. Sequence analysis of VpreB tail regions indicated differences in sequence content, charge, and length; where repertoire data was available, we observed a significant relationship between VpreB2 tail length and maximum DH length. We posit that SLC components co-evolved with immunoglobulin HC to accommodate the repertoire - particularly CDR H3 length and structure, and perhaps highly unusual HC (like ultralong HC of cattle) may bypass this developmental checkpoint altogether.