Abstract: Anthrax Vaccine Adsorbed (AVA) generates short-lived protective antigen (PA) specific IgG that correlates with in vitro toxin neutralization and protection from Bacillus anthracis challenge. Animal studies suggest that when PA-specific IgG has waned, survival after spore challenge correlates with an activation of PA-specific memory B cells. Here, we characterize the quantity and the longevity of AVA-induced memory B cell responses in humans. Peripheral blood mononuclear cells (PBMCs) from individuals vaccinated ≥3 times with AVA (n = 50) were collected early (3–6 months, n = 27) or late after their last vaccination (2–5 years, n = 23), pan-stimulated, and assayed by ELISPOT for total and PA-specific memory B cells differentiated into antibody secreting cells (ASCs). PA-specific ASC percentages ranged from 0.02% to 6.25% (median: 1.57%) and did not differ between early and late post-vaccination individuals. PA-specific ASC percentages correlated with plasma PA-specific IgG (r = 0.42, p = 0.03) and toxin neutralization (r = 0.52, p = 0.003) early post vaccination. PA-specific ASC percentages correlated with supernatant anti-PA both early (r = 0.60, p = 0.001) and late post vaccination (r = 0.71, p < 0.0001). These data suggest PA-specific memory B cell responses are long-lived and can be estimated after recent vaccination by the magnitude and neutralization capacity of the humoral response.
Keywords: Anthrax Vaccine Adsorbed; cellular immunity; lethal toxin neutralization; protective antigen
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Garman, L.; Smith, K.; Farris, A.D.; Nelson, M.R.; Engler, R.J.M.; James, J.A. Protective Antigen-Specific Memory B Cells Persist Years after Anthrax Vaccination and Correlate with Humoral Immunity. Toxins 2014, 6, 2424-2431.
Garman L, Smith K, Farris AD, Nelson MR, Engler RJM, James JA. Protective Antigen-Specific Memory B Cells Persist Years after Anthrax Vaccination and Correlate with Humoral Immunity. Toxins. 2014; 6(8):2424-2431.
Garman, Lori; Smith, Kenneth; Farris, A. D.; Nelson, Michael R.; Engler, Renata J.M.; James, Judith A. 2014. "Protective Antigen-Specific Memory B Cells Persist Years after Anthrax Vaccination and Correlate with Humoral Immunity." Toxins 6, no. 8: 2424-2431.