Infant and Adult Human B Cell Responses to Rotavirus Share Common Immunodominant Variable Gene Repertoires

Abstract

Ab repertoires exhibit marked restrictions during fetal life characterized by biases of variable gene usage and lack of junctional diversity. We tested the hypothesis that Ab repertoire restriction contributes to the observed poor quality of specific Ab responses made by infants to viral infections. We analyzed the molecular determinants of B cell responses in humans to two Ags of rotavirus (RV), a common and clinically important infection of human infants. We sequenced Ab H and L chain V region genes (VH and VL) of clones expanded from single B cells responding to RV virus protein 6 or virus protein 7. We found that adults exhibited a distinct bias in use of gene segments in the VH1 and VH4 families, for example, VH1–46, VH4–31, and VH4–61. This gene segment bias differed markedly from the VH3 dominant bias seen in randomly selected adult B cells. Recombinant Abs incorporating any of those three immunodominant VH segments bound to RV-infected cells and also to purified RV particles. The RV-specific B cell repertoires of infants aged 2–11 mo and those of adults were highly related when compared by VH, D, JH, VL, and JL segment selection, extent of junctional diversity, and mean H chain complementarity determining region 3 length. These data suggest that residual fetal bias of the B cell repertoire is not a limiting determinant of the quality of Ab responses to viruses of infants beyond the neonatal period.

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).…”

“…The dominance of this V H gene segment appears to stem from the fact that the HCDR1 and HCDR2 loops specified by V H 1-46 exhibit an optimal Ab-combining site for loops on the surface of VP6 with a high level of shape complementarity and resulting optimal affinity for a primary response (26). Our original report on RV-specific B cell repertoire also suggested V H 1-46 gene usage in B cells sorted to be VP7 specific (15). Our subsequent studies, however, suggested that these clones were VP6 specific and likely sorted by the DLPs displaying VP6 that resulted from the loss of VP7 on the relatively unstable triple-layered particles used for sorting.…”

“…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).…”

“…Our previous studies have shown that V H gene segment usage in VP6-specific human B cells was distinct from that of randomly selected B cells, and was similar in both adults and infants (15,16).…”

Fetal and neonatal gene therapy: benefits and pitfalls

“…36 Human fetal B cells have reduced antibody repertoires due to reduced junctional diversity; however, this is not a limiting determinant of the quality of antibody response to viruses of infants beyond the neonatal period. 37 It has also been observed that white blood cells from preterm and term neonates show blunted IL-10 and TGFb production after lipopolysaccharide and phorbol myristoyl aceate/ionomycin stimulation, respectively. Furthermore, IL-10 was less effective in inhibiting IL1a, IL-6, IL-8 and TNFa produced in response to LPS.…”