Abstract
BackgroundBlood collection, transportation and storage remain a problem in countries where infrastructure, laboratory facilities and skilled manpower are scarce. This limits evaluation of immune responses in natural infections and vaccination in field studies. We developed methods to measure antigen specific antibody responses using dried blood spot (DBS) in cholera, ETEC and typhoid fever patients as well as recipients of oral cholera vaccine (OCV).Methodology/Principle findingsWe processed heparinized blood for preparing DBS and plasma specimens from patients with, cholera, ETEC and typhoid as well as OCV recipients. We optimized the conventional vibriocidal method to measure vibriocidal antibody response in DBS eluates. We measured responses in DBS samples and plasma (range of titer of 5 to 10240). Vibriocidal titer showed strong agreement between DBS eluates and plasma in cholera patients (ICC = 0.9) and in OCV recipients (ICC = 0.8) using the Bland-Altman analysis and a positive correlation was seen (r = 0.7, p = 0.02 and r = 0.6, p = 0.006, respectively). We observed a strong agreement of lipopolysaccharide (LPS) and cholera toxin B (CTB)-specific antibody responses between DBS eluates and plasma in cholera patients and OCV recipients. We also found agreement of heat labile toxin B (LTB) and membrane protein (MP)-specific antibody responses in DBS eluates and plasma specimen of ETEC and typhoid patients respectively.ConclusionOur results demonstrate that dried blood specimens can be used as an alternate method for preservation of samples to measure antibody responses in enteric diseases and vaccine trials and can be applied to assessment of responses in humanitarian crisis and other adverse field settings.
Highlights
Blood collection, processing and quick transportation to laboratories from remote areas in resource poor settings can be limitations in carrying out serological studies especially in developing countries where laboratory facilities and trained manpower as well as cold chain facilities are not optimal
Our results demonstrate that dried blood specimens can be used as an alternate method for preservation of samples to measure antibody responses in enteric diseases and vaccine trials and can be applied to assessment of responses in humanitarian crisis and other adverse field settings
We set up the vibriocidal assay procedure using dried blood spot (DBS) eluates so that the assay could be measured in an ELISA Reader (Eon, BioTek, Vermont, USA) similar to the way the conventional and existing vibriocidal assay was being used (Fig 1)
Summary
Blood collection, processing and quick transportation to laboratories from remote areas in resource poor settings can be limitations in carrying out serological studies especially in developing countries where laboratory facilities and trained manpower as well as cold chain facilities are not optimal. Dried blood spot (DBS) is an alternate method for collecting blood specimens on paper. This lowers biological risks associated with conventional blood transportation, does not require maintaining cold-chain during transportation and DBS card can be shipped at ambient temperature and even by ordinary mail [1,2]. Transportation and storage remain a problem in countries where infrastructure, laboratory facilities and skilled manpower are scarce. This limits evaluation of immune responses in natural infections and vaccination in field studies. We developed methods to measure antigen specific antibody responses using dried blood spot (DBS) in cholera, ETEC and typhoid fever patients as well as recipients of oral cholera vaccine (OCV)
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