VH1–46 Is the Dominant Immunoglobulin Heavy Chain Gene Segment in Rotavirus-Specific Memory B Cells Expressing the Intestinal Homing Receptor α4β7

Abstract

Memory B cells expressing the intestinal homing marker α4β7 are important for protective immunity against human rotavirus (RV). It is not known whether the B cell repertoire of intestinal homing B cells differs from B cells of the systemic compartment. In this study, we analyzed the RV-specific VH and VL repertoire in human IgD− B cells expressing the intestinal homing marker α4β7. The mean frequency of RV-specific B cells in the systemic compartment of healthy adult subjects was 0.6% (range, 0.2–1.2). The mean frequency of IgD− B cells that were both RV specific and α4β7 was 0.04% (range, 0.01–0.1), and a mean of 10% (range, 1–32) of RV-specific peripheral blood human B cells exhibited an intestinal homing phenotype. We previously demonstrated that VH1–46 is the dominant Ab H chain gene segment in RV-specific systemic B cells from adults and infants. RV-specific systemic IgD− or intestinal homing IgD−/α4β7+ B cells in the current study also used the gene segment VH1–46 at a high frequency, while randomly selected B cells with those phenotypes did not. These data show that VH1–46 is the immunodominant gene segment in human RV-specific effector B cells in both the systemic compartment and in intestinal homing lymphocytes. The mean replacement/silent mutation ratio of systemic compartment IgD− B cells was >2, consistent with a memory phenotype and antigenic selection. Interestingly, RV-specific intestinal homing IgD−/α4β7+ B cells using the VH1–46 gene segment were not mutated, in contrast to systemic RV-specific IgD− B cells.

Immunodominance of the VH1–46 Antibody Gene Segment in the Primary Repertoire of Human Rotavirus-Specific B Cells Is Reduced in the Memory Compartment through Somatic Mutation of Nondominant Clones

“…We found that the proportion of RV VP6-specific B cells that are memory cells represents a lower frequency and a less frequently isotype-switch phenotype compared with the proportion of randomly selected B cells that are memory cells. This high proportion of naive B cells in virus-specific clones in the circulation during infection, even in adults who likely have a history of many previous RV infections, is curious and unexplained (14,15,17). We showed previously a high frequency of naive B cells in the VP6 repertoire in adults, and a reduced frequency of somatic mutations in VP6-specific IgD Ϫ memory B cells (15,17).…”

“…We showed previously a high frequency of naive B cells in the VP6 repertoire in adults, and a reduced frequency of somatic mutations in VP6-specific IgD Ϫ memory B cells (15,17). The Ab genes of RV-specific intestinal-homing memory (␣ 4 ␤ 7 ϩ IgD Ϫ ) B cells in particular are almost completely devoid of somatic mutations, even though they are isotype switched (17). Our previous studies, however, considered IgD ϩ -positive cells to be naive cells, whereas recent studies show that a third major subset of B cells exists within the unclass-switched IgD ϩ population (i.e., CD27 ϩ IgD ϩ cells) that are memory cells (18,19).…”

“…This high proportion of naive B cells in virus-specific clones in the circulation during infection, even in adults who likely have a history of many previous RV infections, is curious and unexplained (14,15,17). We showed previously a high frequency of naive B cells in the VP6 repertoire in adults, and a reduced frequency of somatic mutations in VP6-specific IgD Ϫ memory B cells (15,17). The Ab genes of RV-specific intestinal-homing memory (␣ 4 ␤ 7 ϩ IgD Ϫ ) B cells in particular are almost completely devoid of somatic mutations, even though they are isotype switched (17).…”

“…V H 1-46 is the immunodominant Ig gene segment used in both circulating and intestinal-homing VP6-specific B cells (17). However, whether the V H gene bias resides in the naive and/or in the memory VP6-specific B cell compartment remains to be determined.…”

High-throughput antibody sequencing reveals genetic evidence of global regulation of the naïve and memory repertoires that extends across individuals

“…Although there is no direct evidence of such a mechanism, several recent studies indicate the presence of repertoire-based regulatory mechanisms in circulating B-cell subsets. Despite the tendency of pathogen-specific antibody responses to exhibit biased germline gene repertoires, [16][17][18] the frequency of gene family use in naïve and memory subsets is remarkably consistent across individuals. 9,11 Further, alteration of this gene family homeostasis in the circulating B-cell repertoire is associated with disease states.…”