In this article from Aidsmap, Gus Cairns writes on the RIO trial results presented by Professor Sarah Fidler at CROI conference on 10th March 2025.
Chief investigator Professor Sarah Fidler of Imperial College London told the conference that 23.5% of bnAb recipients (eight people) had the typical viral rebound pattern of a rapidly increasing viral load within the first 20 weeks. Four of these ‘rapid rebounders’ had mutations in their HIV suggesting it would be resistant to 10-1074 (currently there is no assay for resistance to 3BNC117).
This study, conducted in the UK and Denmark, gave half of its 68 participants placebo saline infusions. The other half got infusions of long-lasting formulations of two antibodies that can neutralise HIV.
Forty-eight per cent of bnAb recipients had a delayed reappearance of their HIV, between 20 and 72 weeks after stopping ART. Not all of these were single rebound events – many participants had viral loads that oscillated between undetectability and quite high values, up to 55,000, before restarting.
This indicates that the bnAbs, as had been hoped, did more than simply neutralise viral particles – they had a ‘vaccinal’ effect of strengthening immune responses.
