Abstract
Immune protection against pulmonary infections, such as seasonal flu and invasive pneumonia, is severely attenuated with age, and vaccination regimes for the elderly people often fail to elicit effective immune response. We have previously shown that influenza and pneumococcal vaccine responses in the older population are significantly impaired in terms of serum antibody production, and have shown repertoire differences by CDR-H3 spectratype analysis. Here we report a detailed analysis of the B cell repertoire in response to vaccine, including a breakdown of sequences by class and subclass. Clustering analysis of high-throughput sequencing data enables us to visualize the response in terms of expansions of clonotypes, changes in CDR-H3 characteristics, and somatic hypermutation as well as identifying the commonly used IGH genes. We have highlighted a number of significant age-related changes in the B cell repertoire. Interestingly, in light of the fact that IgG is the most prevalent serum antibody and the most widely used as a correlate of protection, the most striking age-related differences are in the IgA response, with defects also seen in the IgM repertoire. In addition there is a skewing toward IgG2 in the IgG sequences of the older samples at all time points. This analysis illustrates the importance of antibody classes other than IgG and has highlighted a number of areas for future consideration in vaccine studies of the elderly.
Highlights
Until recently the methods available to study B cell repertoire were limited by the fact that the diversity of the repertoire was far greater than the number of sequences that could feasibly be studied
Blood and serum samples were collected after obtaining written consent as approved by the Guy’s Hospital Research ethics committee, prior to vaccination at day 0 (D0) with the influenza (Influvac; Solvay, Southampton, UK), and 23-valent pneumococcal (Pneumovax II; Sanofi Pasteur MSD, Maidenhead, UK) vaccines and post vaccination at day 7 (D7) and day 28 (D28)
The repertoire displayed resilience in that at D28 post vaccination it showed similar characteristics to D0 despite significant changes at day 7 post vaccination. These changes at D7 included a change in expression of some IGHV and IGHJ genes such that significant differences were seen in IGH gene family usage (Figure 1A)
Summary
Until recently the methods available to study B cell repertoire were limited by the fact that the diversity of the repertoire was far greater than the number of sequences that could feasibly be studied. A random sampling of cells responding to vaccine would pick up the most prevalent Ig genes but would not give any indication of the diversity of cells responding to challenge. In humans the isolation of rearranged Ig genes with more than one type of IGHV gene has indicated that there might be diversity in the response, but the numbers of sequences studied in these experiments have been low. One of the best examples of repertoire analysis was by Kolibab et al (2005a) who looked at approximately 1300 sequences from 40 different donors after immunization by the pneumococcal vaccine and identified the major IGHV genes in use. With the advent of high-throughput sequencing methods we can study the human immune response in much more detail
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