Monitoring broadly neutralising HIV antibody concentrations using microsampling on dried blood spots in infants

The use of broadly neutralising antibodies (bNAb) to prevent HIV infection is under active investigation, including for the prevention of vertical HIV transmission. In neonates, an uncomplicated sampling method for blood collection is the use of dried blood spots (DBS). We aimed to validate the use of a combination of DBS with ELISA techniques to monitor bNAb concentrations, namely VRC07-523LS and CAP256V2LS, in neonates.

We evaluated the performance of various DBS elution protocols on spiked adult blood and next on spiked cord blood. The optimised method was validated on blood from infants injected with bNAbs.

After selecting the best elution conditions, we reported good repeatability and reproducibility for both bNAbs in cord blood samples. The concordance study with infant receiving VRC07-523LS or CAP256V2LS samples showed that the values obtained from DBS eluates were closely aligned with those from plasma samples and when corrected by the haematocrit value, the number of outliers was 10.1% with a positive bias of 0.35 µg/mL for CAP256V2LS, and 5.0% with a positive bias of 3 µg/mL for VRC07-523LS.

DBS microsampling allows accurate bNAb concentration measure in neonates, which will facilitate on-going paediatric clinical trials and possible subsequent monitoring in adults with home-sampling if deployed at scale.