Preprint: Closed-loop AI system discovers broadly neutralizing antibodies that protected mice from H1N1

A new arXiv preprint from researchers in China says a closed-loop AI-and-lab system can identify broadly neutralizing antibodies directly from unsorted human B-cell repertoires across multiple virus families, including influenza antibodies that fully protected mice in a lethal challenge. If the findings hold up, the work would mark a notable step in the search for rare antibodies that can block many strains of a virus rather than just one.

But the results are author-reported findings in a preprint, not a peer-reviewed paper, and they have not been independently replicated. In the study, posted to arXiv on Oct. 2, 2026, the authors wrote that their system “achieves a ~55% neutralization antibody discovery rate (60 of 110 cloned candidates) and a ~11% bnAb yield (12 of 110).” In mouse tests, they reported that five influenza antibodies found by the system gave 100% survival in a prophylactic BALB/c model after animals were challenged with 5 times the lethal dose of A/California/07/2009, an H1N1 flu strain. Mice received a single 10 milligram-per-kilogram intraperitoneal dose one day before infection. The paper said the antibodies performed comparably to MEDI8852, a clinical-stage broadly neutralizing flu antibody used as a benchmark, but also stressed that the study “was not powered to establish equivalence.”

The paper, titled “Multimodal reasoning for broadly neutralizing antibody discovery from label-free human B cell repertoires across virus families,” describes “ImmuneAgent, a closed-loop AI system” that combines computational analysis with wet-lab feedback. In plain terms, the system is designed to sift through natural human immune-cell receptor data from vaccinated or infected people, nominate promising antibody candidates, test them in the lab and feed those results back into the next round of searching. The author list includes Hantao Lou, Jianqing Zheng, Can Yue, Meihan Zhang, Yuanchao Bao, Xuetao Cao and Xiangxi Wang, among others, with primary affiliations including Nankai University, Peking Union Medical College and the Chinese Academy of Medical Sciences, the Institute of Biophysics at the Chinese Academy of Sciences, and Guangzhou National Laboratory.

The researchers also said the system generalized beyond flu without using antigen-specific sorting, a common way of narrowing down immune cells known to bind a target. For RSV and human metapneumovirus, or hMPV, they reported 13 antibodies out of 30 nominated candidates that neutralized all five tested viruses across RSV-A, RSV-B and hMPV. For human papillomavirus, or HPV, they said 9 of 50 cloned candidates showed neutralizing activity. The paper also said the work highlighted FCRL5+CD27+ atypical memory B cells as a conserved source of broadly neutralizing antibodies and pointed to hydrophobic enrichment at the antibody-antigen interface as a structural feature linked to breadth.

That matters because broadly neutralizing antibodies are both valuable and hard to find. They can work across multiple strains or related viruses, which makes them attractive as research tools and potential starting points for medicines. But they are rare in natural human immune repertoires, and historically they have been difficult to identify efficiently. MEDI8852 is a meaningful reference point because it is an established clinical-stage influenza broadly neutralizing antibody, so matching it in a mouse experiment, even without proving equivalence, gives readers a concrete benchmark for the level of activity being claimed.

The authors said they have made single-cell sequencing data, cryo-electron microscopy structures and code repositories publicly available, which should give outside researchers material to scrutinize the work. The paper also states that the authors declare no conflicts of interest. AI systems tied directly to lab experiments are an active area of research, but for this study the key next step is straightforward: independent groups will need to test whether the reported antibody hit rates, cross-virus findings and mouse protection results can be reproduced.