13-valent pneumococcal conjugate vaccine-induced B cells produce serotype 6B but not serotype 3 capsule-specific IgG antibodies in young Malawian adults.
Tembo G., Hoving D., de Kroon AC., Chimgoneko L., Nthandira T., Galafa B., Thole F., Nsomba E., Dula D., Ngoliwa C., Toto N., Makhaza L., Muyaya A., Kudowa E., Chirwa AE., Henrion MYR., Chikaonda T., Urban BC., Ferreira DM., Jambo KC., Jochems SP., Gordon SB.
Pneumococcal conjugate vaccine (PCV13) introduction has reduced vaccine-type carriage and disease; however pneumococcal carriage persists at high rates particularly in high-transmission settings. Serotype 3 remains a particular problem in Malawi and globally, with high carriage rates, as well as strain resistance to antibiotics and antibody-mediated killing. We studied antibody and B cell responses to PCV13 in 65 healthy Malawian adults (18-40 years) taking part in a randomized controlled trial. Serum, nasal fluid, and PBMC samples were collected before and after vaccination. Anti-capsular IgG for serotypes 3 and 6B were measured by ELISA, and capsule-specific B cells were assessed by spectral flow cytometry. PCV13 increased both serum and mucosal IgG levels, and IgG+ B cells in blood for serotype 6B but not serotype 3. The poor immunogenicity of serotype 3 capsular polysaccharide in Malawian young adults highlights the need for alternative vaccines to address persistent serotype 3 carriage and disease.