Vibrio cholerae-specific antibodies in plasma and saliva in cholera patients during a severe outbreak in Zambia: an antibody profiling approach

Charlie Chaluma Luchen^1,2*Harriet Ngo'mbe¹Fraser Liswaniso¹Samuel Bosomprah^1,3Julia A Zhiteneva⁴Jason Harris^5,6Richelle Charles^5,7,8Edward Ryan^5,7,8David Allen Sack⁹Biana Bernshtein⁴Caroline Chisenga¹

• ¹Centre for Infectious Disease Research in Zambia, Lusaka, Zambia
• ²Amsterdam UMC, location University of Amsterdam, Department of Global Health, Amsterdam Institute for Global Health and Development, Meibergdreef 9, Amsterdam, Netherlands
• ³Department of Biostatistics, School of Public Health, University of Ghana, Accra, Ghana
• ⁴Ragon Institute of Mass General, MIT, and Harvard, Cambridge, Massachusetts, United States
• ⁵Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts, United States
• ⁶Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, United States
• ⁷Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States
• ⁸Department of Medicine, Harvard Medical School, Boston, Massachusetts, United States
• ⁹Center for Immunization Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, United States

Cholera is a public health threat in resource-limited settings and is responsible for causing over 3 million cases globally. Mucosal immune responses play an important role in protecting against Vibrio cholerae infection, a non-invasive mucosal pathogen, yet traditional plasma-based assays are invasive and logistically challenging, particularly during outbreaks in low-and middle-income countries (LMICs). Saliva offers a unique window into mucosal immunity and may serve as a noninvasive alternative for seroprevalence and vaccine immunogenicity studies.We conducted a cross-sectional antibody profiling study to analyse cholera-specific antibodies in saliva and plasma samples from 74 participants upon presenting to the cholera treatment centres. These were collected from four treatment centres in Lusaka during Zambia's most severe cholera outbreak in 2024 caused by Vibrio cholerae O1 Ogawa. Levels of total IgG, IgG1-3, IgM, secretory IgA, and IgA1-2 isotypes were used to compare the biomarker profile between the two sample types.Saliva and plasma antibody profiles were comparable, with elevated IgA1 and IgA2 responses to cholera toxin-B (CtxB), sialidase, HlyA, and TcpA in saliva. Broader systemic responses were seen in plasma, including high CtxB-specific IgM, IgA1, and total IgG levels. Notably, biomarkers such as HlyA, Ogawa O-specific polysaccharide (OSP), and sialidase exhibited significant positive correlations between plasma and saliva. Elevated biomarker levels of HlyA, Ogawa O-specific polysaccharide (OSP), and sialidase in people living with HIV/AIDS (PLWHA) suggested immunological differences that warrant further exploration.We demonstrate that saliva is a viable, non-invasive alternative for cholera antibody-based profiling, offering practical advantages in resource-constrained settings. Given its strong correlation with systemic antibody profiles, saliva may be a practical sample for sero-surveillance in resource-limited settings. Future studies should investigate the duration of these salivary responses to further substantiate their use in estimating disease burden and immunity.