TY - JOUR
T1 - Isolation and Characterization of Human Monoclonal Antibodies to Pneumococcal Capsular Polysaccharide 3
AU - Babb, Rachelle
AU - Doyle, Christopher R.
AU - Pirofski, Liise Anne
N1 - Funding Information:
We thank Phil Gialanella at Montefiore Medical Center for isolation of the clinical strain B2 used in the study. This study was supported by National Institutes of Health grants to L.P., namely, R01AG045044 and R01AI123654. R.B. designed and performed experiments, analyzed and interpreted data, and wrote the manuscript. C.R.D. assisted with experimental design and contributed to revising and critically reviewing the manuscript. L.P. supervised the study, designed experiments, interpreted data, and wrote the manuscript. We have no conflict of interest with the data reported in the manuscript.
Publisher Copyright:
© 2021 Babb et al.
PY - 2021/12
Y1 - 2021/12
N2 - The current pneumococcal capsular polysaccharide (PPS) conjugate vaccine (PCV13) is less effective against Streptococcus pneumoniae serotype 3 (ST3), which remains a major cause of pneumococcal disease and mortality. Therefore, dissecting structure-function relationships of human ST3 pneumococcal capsular polysaccharide (PPS3) antibodies may reveal characteristics of protective antibodies. Using flow cytometry, we isolated PPS3-binding memory B cells from pneumococcal vaccine recipients and generated seven PPS3-specific human monoclonal antibodies (humAbs). Five humAbs displayed ST3 opsonophagocytic activity, four induced ST3 agglutination in vitro, and four mediated both activities. Two humAbs, namely, C10 and C27, that used the same variable heavy (VH) and light (VL) chain domains (VH3- 9*01/VL2-14*03) both altered ST3 gene expression in vitro; however, C10 had fewer VL somatic mutations, higher PPS3 affinity, and promoted in vitro ST3 opsonophagocytic and agglutinating activity, whereas C27 did not. In C57BL/6 mice, both humAbs reduced nasopharyngeal colonization with ST3 A66 and a clinical strain, B2, and prolonged survival following lethal A66 intraperitoneal infection, but only C10 protected against lethal intranasal infection with the clinical strain. After performing VL swaps, C10VH/C27VL exhibited reduced ST3 binding and agglutination, but C27VH/C10VL binding was unchanged. However, both humAbs lost the ability to reduce colonization in vivo when their light chains were replaced. Our findings associate the ability of PPS3-specific humAbs to reduce colonization with ST3 agglutination and opsonophagocytic activity, and reveal an unexpected role for the VL in their functional activity in vitro and in vivo. These findings also provide insights that may inform antibody- based therapy and identification of surrogates of vaccine efficacy against ST3.
AB - The current pneumococcal capsular polysaccharide (PPS) conjugate vaccine (PCV13) is less effective against Streptococcus pneumoniae serotype 3 (ST3), which remains a major cause of pneumococcal disease and mortality. Therefore, dissecting structure-function relationships of human ST3 pneumococcal capsular polysaccharide (PPS3) antibodies may reveal characteristics of protective antibodies. Using flow cytometry, we isolated PPS3-binding memory B cells from pneumococcal vaccine recipients and generated seven PPS3-specific human monoclonal antibodies (humAbs). Five humAbs displayed ST3 opsonophagocytic activity, four induced ST3 agglutination in vitro, and four mediated both activities. Two humAbs, namely, C10 and C27, that used the same variable heavy (VH) and light (VL) chain domains (VH3- 9*01/VL2-14*03) both altered ST3 gene expression in vitro; however, C10 had fewer VL somatic mutations, higher PPS3 affinity, and promoted in vitro ST3 opsonophagocytic and agglutinating activity, whereas C27 did not. In C57BL/6 mice, both humAbs reduced nasopharyngeal colonization with ST3 A66 and a clinical strain, B2, and prolonged survival following lethal A66 intraperitoneal infection, but only C10 protected against lethal intranasal infection with the clinical strain. After performing VL swaps, C10VH/C27VL exhibited reduced ST3 binding and agglutination, but C27VH/C10VL binding was unchanged. However, both humAbs lost the ability to reduce colonization in vivo when their light chains were replaced. Our findings associate the ability of PPS3-specific humAbs to reduce colonization with ST3 agglutination and opsonophagocytic activity, and reveal an unexpected role for the VL in their functional activity in vitro and in vivo. These findings also provide insights that may inform antibody- based therapy and identification of surrogates of vaccine efficacy against ST3.
KW - Agglutination
KW - Immunology
KW - Immunotherapy
KW - Monoclonal antibodies
KW - Streptococcus pneumoniae
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U2 - 10.1128/Spectrum.01446-21
DO - 10.1128/Spectrum.01446-21
M3 - Article
C2 - 34756090
AN - SCOPUS:85122731237
VL - 9
JO - Microbiology spectrum
JF - Microbiology spectrum
SN - 2165-0497
IS - 3
M1 - e01446-21
ER -