AP
Calcineurin inhibitors (CNI), used frequently in solid organ transplant patients, are known to inhibit T cell proliferation, but their effect on humoral immunity is far less studied. Total and naive B cells from healthy adult donors were cultured in immunoglobulin (Ig)A- or IgG/IgE-promoting conditions with increasing doses of cyclosporin, tacrolimus, rapamycin or methylprednisolone. The effect on cell number, cell division, plasmablast differentiation and class-switching was tested. To examine the effect on T follicular helper (Tfh) cell differentiation, naive CD4(+) T cells were cultured with interleukin (IL)-12 and titrated immunosuppressive drug (IS) concentrations. Total B cell function was not affected by CNI. However, naive B cell proliferation was inhibited by cyclosporin and both CNI decreased plasmablast differentiation. Both CNI suppressed IgA, whereas only cyclosporin inhibited IgE class-switching. Rapamycin had a strong inhibitory effect on B cell function. Strikingly, methylprednisolone, increased plasmablast differentiation and IgE class-switching from naive B cells. Differentiation of Tfh cells decreased with increasing IS doses. CNI affected humoral immunity directly by suppressing naive B cells. CNI, as well as rapamycin and methylprednisolone, inhibited the in-vitro differentiation of Tfh from naive CD4(+) T cells. In view of its potent suppressive effect on B cell function and Tfh cell differentiation, rapamycin might be an interesting candidate in the management of B cell mediated complications post solid organ transplantation.
Background: Noroviruses are the leading cause of epidemic acute gastroenteritis and foodborne diarrheal disease in humans. However, there are no approved vaccines for noroviruses. Potential correlates of protection identified through human challenge studies include mucosal IgA, memory B cells, and serum-blocking antibody titers (BT50).
Methods: We conducted a single-site, randomized, double-blind, placebo-controlled clinical trial of an oral norovirus vaccine to determine safety and immunogenicity. This tablet vaccine is comprised of a nonreplicating adenovirus-based vector expressing the VP1 gene from the GI.1 norovirus strain and a double-stranded RNA adjuvant. Sixty-six adult subjects meeting inclusion/exclusion criteria were randomized 2:1 to receive a single vaccine dose or placebo, respectively. Immunogenicity was primarily assessed by serum BT50. Additional outcomes included serum ELISA titers, fecal and saliva antibody titers, memory and antibody-secreting cell (ASC) frequency, and B cell phenotyping.
Results: The vaccine was well-tolerated, with no dose-limiting toxicities. Adverse events were mild or moderate. The primary immunological endpoint (increase in BT50 titers) was met in the high-dose group (P = 0.0003), with 78% showing a =2-fold rise in titers after a single immunization. Vaccine recipients also developed mucosally primed VP1-specific circulating ASCs, IgA+ memory B cells expressing gut-homing receptor (a4ß7), and fecal IgA, indicating substantial and local responses potentially relevant to prevent norovirus infection.
Conclusion: This oral norovirus vaccine was well-tolerated and generated substantial immune responses, including systemic and mucosal antibodies as well as memory IgA/IgG. These results are a major step forward for the development of a safe and immunogenic oral norovirus vaccine.
Trial registration: ClinicalTrials.gov NCT02868073.
Funding: Vaxart.
