The frequency of early-activated hapten-specific B cell subsets predicts the efficacy of vaccines for nicotine dependence

Abstract

Therapeutic vaccines for nicotine addiction show pre-clinical efficacy. Yet, clinical evaluation of the first-generation nicotine vaccines did not meet expectations because only a subset of immunized subjects achieved effective serum antibody levels. Recent studies suggest that vaccine design affects B cell activation, and that the frequency of the hapten-specific B cell subsets contributes to vaccine efficacy against drugs of abuse. To extend this hypothesis to nicotine immunogens, we synthesized a novel hapten containing a carboxymethylureido group at the 2-position of the nicotine structure (2CMUNic) and compared its efficacy to the previously characterized 6CMUNic hapten. Haptens were conjugated to the keyhole limpet hemocyanin (KLH) carrier protein, and evaluated for efficacy against nicotine in mice using the clinically approved alum adjuvant. Using a novel fluorescent antigen-based magnetic enrichment strategy paired with multicolor flow cytometry analysis, polyclonal hapten-specific B cell subsets were measured in mice immunized with either 6CMUNic-KLH or 2CMUNic-KLH. The 6CMUNic-KLH showed significantly greater efficacy than 2CMUNic-KLH on nicotine distribution to serum and to the brain. The 6CMUNic-KLH elicited higher anti-nicotine serum antibody titers, and a greater frequency of hapten-specific B cells than 2CMUNic-KLH. Within the splenic polyclonal B cell population, a higher number of hapten-specific IgMhigh and germinal center B cells predicted greater vaccine efficacy against nicotine distribution. These early pre-clinical findings suggest that hapten structure affects activation of B cells, and that variations in the frequency of early-activated hapten-specific B cell subsets underlie individual differences in vaccine efficacy.

Biologics to treat substance use disorders: Current status and new directions

“…33,34 The strength of this approach is that very rare antigen-specific B and T cells are detected prior to, or shortly after immunization. [35][36][37][38][39] To date, this approach has been used to test the effect of hapten structure, 40,41 adjuvant, 42 or host genetics 42 on the B cell response to vaccines for SUD. This strategy has also been used to study the relationship between antigen-specific B and T cells and individual variability in post-immunization Ab titers, or efficacy against drug distribution and drug-induced behavior in mice.…”

“…This strategy has also been used to study the relationship between antigen-specific B and T cells and individual variability in post-immunization Ab titers, or efficacy against drug distribution and drug-induced behavior in mice. 41,43 These studies found that na€ ıve and early-activated B cells can discriminate between structurally-related haptens, and that the size of the polyclonal hapten-specific B cell population determines vaccine immunogenicity and efficacy against drugs of abuse. 40,41 When comparing individuals, differences in the population size of hapten-specific B cells and carrier-specific T cells are found before and/or after immunization in individual mice, and correlate to vaccine immunogenicity and efficacy.…”

“…41,43 These studies found that na€ ıve and early-activated B cells can discriminate between structurally-related haptens, and that the size of the polyclonal hapten-specific B cell population determines vaccine immunogenicity and efficacy against drugs of abuse. 40,41 When comparing individuals, differences in the population size of hapten-specific B cells and carrier-specific T cells are found before and/or after immunization in individual mice, and correlate to vaccine immunogenicity and efficacy. 41,43 Hence, analysis of na€ ıve and early-activated B and T cells could be used to examine vaccine formulations and individual variability across subjects.…”

“…40,41 When comparing individuals, differences in the population size of hapten-specific B cells and carrier-specific T cells are found before and/or after immunization in individual mice, and correlate to vaccine immunogenicity and efficacy. 41,43 Hence, analysis of na€ ıve and early-activated B and T cells could be used to examine vaccine formulations and individual variability across subjects.…”

“…59,60 Consistently, individual variability of similar magnitude has been found in the polyclonal hapten-specific B cell population in blood, peripheral lymph nodes and spleen of various mouse strains, before and after immunization with vaccines for oxycodone and nicotine. [40][41][42][43] Multiple mechanisms may underlie the pre-and post-immunization variability in the antigenspecific B and T cell subsets and contribute to individual vaccine efficacy. Apoptosis and antigen affinity affect the heterogeneity of the primary immune response by limiting differentiation of a single na€ ıve B cell shortly after immunization.…”