This study investigated CQ/Pyr modulation of B cell immunity since there are implications for accurately measuring parasite immunomodulation and interpreting the generation of effective memory B cells (MBCs).
Mice were immunised with 1) carbohydrate (GPI-KLH), 2) protein (NP-KLH) or 3) naïve and drug treated or not at day 5 (D5) as per P. berghei (PBA) treatment protocol. A sub-set of mice were assessed for prime responses at D14 (flow cytometry). At D17 mice were boosted and either drug treated or not (D20). Mice were euthanised at D28 (flow cytometry, ELISPOTs). Non-parametric unpaired T test or Kruskal-Wallis tests were used to assess significance.
Untreated vaccinated mice had significantly higher cell counts and frequencies indicative of B cell activation, including MBCs, compared to naives. At D14, CQ/Pyr-treated vaccinated mice had reduced cell counts and frequencies to a level no longer significantly higher than naives. Furthermore, frequency of anti-NP-IgG1 MBCs was significantly suppressed (treatment vs no treatment). By day 28, CQ/Pyr-treated NP vaccinated mice had recovered from the initial suppression, with significantly higher B cell responses, including MBCs, compared to naives. In contrast, CQ/Pyr-treated GPI vaccinated mice did not appear to recover as quickly, with MBCs frequencies and cell counts not significantly higher than naïves.
Low doses of CQ/PYR has a generalised non-antigen specific suppressive effect on kinetics of early B cell responses to protein and carbohydrate antigens. The suppression was resolved for NP. For the carbohydrate antigen, GPI-KLH, the majority of suppressive effects were resolved however, there was lingering disruption to anti-GPI IgG1 MBC production. PBA murine models should include relevant CQ/Pyr controls if PBA challenged mice are CQ/Pyr treated to ensure only parasite modulation of B cells is accurately measured. Furthermore, potential CQ/Pyr long-term suppression on effective MBCs is unknown, and must be considered when exploring candidate vaccines.