Serological and B cell responses in experimentally infected macaques. ( A ) Serum endpoint total IgG titers were measured by ELISA using CA09 HA-FL (blue) or stabilized CA09 HA stem (red) in macaques ( n = 8) infected intranasally with A/Auckland/1/2009. Note that 2 animals were sacrificed on day 23. Dotted lines denote the detection cutoff (dilution 1:100). ( B ) Frequency of IgG + memory B cells (CD19 + IgD – IgG + ) binding CA09 HA-FL (blue) or stabilized CA09 HA stem (red) was measured by flow cytometry within cryopreserved PBMC samples from infected macaques ( n = 6). Note that the 2 animals sacrificed on day 23 were excluded.
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