The Quantitative Assessment of the Secreted IgG Repertoire after Recall to Evaluate the Quality of Immunizations

Abstract

One of the major goals of vaccination is to prepare the body to rapidly secrete specific Abs during an infection. Assessment of the vaccine quality is often difficult to perform, as simple measurements like Ab titer only partly correlate with protection. Similarly, these simple measurements are not always sensitive to changes in the preceding immunization scheme. Therefore, we introduce in this paper a new, to our knowledge, method to assay the quality of immunization schemes for mice: shortly after a recall with pure Ag, we analyze the frequencies of IgG-secreting cells (IgG-SCs) in the spleen, as well as for each cells, the Ag affinity of the secreted Abs. We observed that after recall, appearance of the IgG-SCs within the spleen of immunized mice was fast (<24 h) and this early response was free of naive IgG-SCs. We further confirmed that our phenotypic analysis of IgG-SCs after recall strongly correlated with the different employed immunization schemes. Additionally, a phenotypic comparison of IgG-SCs presented in the spleen during immunization or after recall revealed similarities but also significant differences. The developed approach introduced a novel (to our knowledge), quantitative, and functional highly resolved alternative to study the quality of immunizations.

Quantitative modeling of the effect of antigen dosage on B-cell affinity distributions in maturating germinal centers

“…We test four different values for this delay: = 1, 2, 4 and 8 weeks. These protocols have also been used in Eyer et al, 2020 , and thanks to the multiple injections they allow us to study the effect of memory recall in subsequent immunizations.…”

“…In our experiments we test three different immunization protocols, schematized in fig which is kept constant at D = 10 µg TT, in this scheme the time delay between the first two injections ∆T is varied. We test four different values for this delay: ∆T = 1, 2, and weeks.These protocols have also been used in [38], and thanks to the multiple injections they allow us to study the effect of memory recall in subsequent immunizations.…”

“…The mice used herein were part of the study as published elsewhere [38]. In short, BALB-C mice were fig.…”

“…A second open issue concerning AM is to characterize in a quantitative way the selection acting in the GC, in particular how permissive it is [14,15,35,36]. Through mechanisms such as bystander activation [37,38,39] GC selection can indeed allow intermediate and low affinity clones to survive [10]. These phenomena generate a wider diversity than previously appreciated, especially when considering complex Ags displaying different epitopes [40].…”

“…A second open issue concerning AM is to characterize in a quantitative way the selection acting in the GC, in particular how permissive it is ( Bannard and Cyster, 2017 ; Mesin et al, 2016 ; Victora and Mouquet, 2018 ; Inoue et al, 2018 ). Through mechanisms such as bystander activation ( Bernasconi, 2002 ; Eyer et al, 2020 ; Eyer et al, 2017 ) GC selection can indeed allow intermediate- and low-affinity clones to survive ( Tas et al, 2016 ). These phenomena generate a wider diversity than previously appreciated, especially when considering complex Ags displaying different epitopes ( Kuraoka et al, 2016 ).…”