Natural Immunity to Klebsiella pneumoniae in Mothers and Their Infants in Malawi
Abstract
Background: Klebsiella pneumoniae is a leading cause of neonatal sepsis in low- and middle-income countries, with high associated mortality. Anti–K. pneumoniae maternal antibodies may provide early-life protection to neonates, yet data about their prevalence, transplacental transfer, and functional activity remain limited.
Methods: We conducted a study in Malawian mother–infant dyads measuring immunoglobulin G (IgG) to K. pneumoniae O1 serotypes, O1αβ,2α and O1αβ,2β, and functional immunity. Immunity was also analyzed in dyad sera from (i) culture-confirmed K. pneumoniae infection (cases), (ii) non–K. pneumoniae infections (sick controls), and (iii) healthy controls.
Results: Anti O1-IgG titers were similar in all mothers and significantly greater in infants. Similarly, functional immunity was significantly higher in mothers than their infants. Transfer ratios for functional immunity between mother and infant were significantly lower (0.017) than those seen for anti-O1 IgG (0.8). While IgG to O1αβ,2α and O1αβ,2β and functional immunity were significantly correlated in healthy infants, this was not the case in maternal serum. Neither Klebsiella-specific maternal IgM titers nor IgG subclasses could explain this; thus additional factors, in addition to anti-O1 IgG, are likely contributing to functional immunity.
Conclusions: Natural anti O1 antibodies are ubiquitous in healthy mothers in Malawi, and IgG is efficiently transferred to neonates. Reduced functional immunity in infants compared with mothers, as demonstrated in this study, may underpin the susceptibility to K. pneumoniae infection in early life, justifying the exploration of maternal immunization to prevent early-life infection. Further studies are needed to define the characteristics of anti–K. pneumoniae immunity that might be associated with clinical protection.
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BibTeX
@article{karaky2026natural,
title = {{Natural Immunity to Klebsiella pneumoniae in Mothers and Their Infants in Malawi}},
author = {Nathalie Karaky and Oliver Pearse and Robert Lawrence and Emma Bownes and Edward Hildebrand and Allan Zuza and Luis Gadama and David Lissauer and Samantha Lissauer and Kondwani Kawaza and Nicholas Feasey and David Goldblatt},
journal = {Open Forum Infectious Diseases},
year = {2026},
month = oct,
doi = {10.1093/ofid/ofag676},
url = {https://doi.org/10.1093/ofid/ofag676},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Natural Immunity to Klebsiella pneumoniae in Mothers and Their Infants in Malawi
AU - Nathalie Karaky
AU - Oliver Pearse
AU - Robert Lawrence
AU - Emma Bownes
AU - Edward Hildebrand
AU - Allan Zuza
AU - Luis Gadama
AU - David Lissauer
AU - Samantha Lissauer
AU - Kondwani Kawaza
AU - Nicholas Feasey
AU - David Goldblatt
PY - 2026
DA - 2026/10/22
JO - Open Forum Infectious Diseases
DO - 10.1093/ofid/ofag676
UR - https://doi.org/10.1093/ofid/ofag676
AB - Background: Klebsiella pneumoniae is a leading cause of neonatal sepsis in low- and middle-income countries, with high associated mortality. Anti–K. pneumoniae maternal antibodies may provide early-life protection to neonates, yet data about their prevalence, transplacental transfer, and functional activity remain limited. Methods: We conducted a study in Malawian mother–infant dyads measuring immunoglobulin G (IgG) to K. pneumoniae O1 serotypes, O1αβ,2α and O1αβ,2β, and functional immunity. Immunity was also analyzed in dyad sera from (i) culture-confirmed K. pneumoniae infection (cases), (ii) non–K. pneumoniae infections (sick controls), and (iii) healthy controls. Results: Anti O1-IgG titers were similar in all mothers and significantly greater in infants. Similarly, functional immunity was significantly higher in mothers than their infants. Transfer ratios for functional immunity between mother and infant were significantly lower (0.017) than those seen for anti-O1 IgG (0.8). While IgG to O1αβ,2α and O1αβ,2β and functional immunity were significantly correlated in healthy infants, this was not the case in maternal serum. Neither Klebsiella-specific maternal IgM titers nor IgG subclasses could explain this; thus additional factors, in addition to anti-O1 IgG, are likely contributing to functional immunity. Conclusions: Natural anti O1 antibodies are ubiquitous in healthy mothers in Malawi, and IgG is efficiently transferred to neonates. Reduced functional immunity in infants compared with mothers, as demonstrated in this study, may underpin the susceptibility to K. pneumoniae infection in early life, justifying the exploration of maternal immunization to prevent early-life infection. Further studies are needed to define the characteristics of anti–K. pneumoniae immunity that might be associated with clinical protection.
SN - 2328-8957
ER -