Rapid Collection of Human Rectal Secretions Using OriCol Devices Is Suitable for Measurement of Mucosal Ig without Blood Contamination.

ABSTRACT

Measurements of IgG and IgA in human rectal secretions are used to evaluate the Abs elicited by HIV vaccines or the bioaccumulation following immunoprophylaxis at the sites of HIV exposure. To improve sampling methods and tolerability of the procedure, we optimized a balloon device (OriCol) for rectal microbiome sampling requiring 10 second inflation and compared this method to a 5 minute collection using sponges. Lubrication of the device did not interfere with IgG, IgA, or hemoglobin ELISA. Lubricated OriCols inflated to 30 cc minimized hemoglobin contamination (<4.68 ng/ml) compared with collections with two sponge types (Weck-Cel 267.2 ng/ml, p < 0.0001; and Merocel 59.38 ng/ml, p = 0.003). Median human serum albumin for OriCols was 14.9 µg/ml, whereas Merocels and Weck-Cels were 28.57 µg/ml (p = 0.0005) and 106.2 µg/ml (p = 0.0002), respectively. Consistent with reduced systemic contamination, the median IgG measured in OriCol-collected rectal secretions (986 ng) was lower than secretions from sponges (Weck-Cel 8588 ng, p < 0.0001; Merocel 2509 ng, p = 0.0389). The median IgA yield of samples using the OriCol method (75,253 ng) was comparable to that using Merocel (71,672 ng; p = 0.6942) but significantly higher than Weck-Cel sponges (16,173 ng, p = 0.0336). Median recovery volumes for OriCols were 800 µl, whereas Merocels and Weck-Cels were 615 µl (p = 0.0010) and 655 µl (p = 0.0113), respectively. The balloon device was acceptable among 23 participants, as 85.1% experiencing their first collection ranked it as "seven acceptable - a lot" or "six acceptable - somewhat" in a seven-point Likert scale. Therefore, lubricated OriCols inflated to 30 cc allowed for a rapid, well-tolerated, blood-free collection of human rectal secretions.