Correlation between antibody titers in human serum and plasma prepared with EDTA for the assessment of cholera vaccine immune responses

The possibility of quantifying vibriocidal antibody activity and cholera anti-toxin IgG antibody levels using both serum and plasma samples in quantification assays is essential during the clinical evaluation of cholera vaccines. However, the anticoagulant used to obtain plasma could not interfere with the analytical results. In this work, the activity of bacterial growth inhibitory antibodies (vibriocidal antibody activity), as well as anti-toxin IgG levels, was determined in the blood of nine patients diagnosed with cholera. A strong correlation was demonstrated between antibody titers against immunologically relevant antigens during the analysis of serum and plasma samples, which were obtained concomitantly and prepared in the presence of EDTA. This result supports the feasibility of the indiscriminate use of serum or plasma in such immunological assays. Likewise, we report the preparation and characterization of reference samples that can be used as positive and negative controls in such tests.