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.; Kroon, A.C. de; Chimgoneko, L.; Nthandira, T.; Galafa, B.; Thole, F.; Nsomba, E.; Dula, D.; Ngoliwa, C.; Toto, N.; Makhaza, L.; Muyaya, A.; Kudowa, E.; Chirwa, A.E.; Henrion, M.Y.R.; Chikaonda, T.; Urban, B.C.; Ferreira, D.M.; Jambo, K.C.; Jochems, S.P.; Gordon, S.B.

doi:doi:10.1016/j.vaccine.2026.128269

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 capsulespecific 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...Show morePneumococcal 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 capsulespecific 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.Show less

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13-valent pneumococcal conjugate vaccine-induced B cells produce serotype 6B but not serotype 3 capsule-specific IgG antibodies in young Malawian adults