Unveiling the hidden human virome: defining antigenicity and immune recognition of anelloviruses

The National Institutes of Health Office of the Director awarded Icahn School of Medicine at Mount Sinai $335,999 under the Trans-NIH Research Support program (CFDA 93.310) on September 1, 2026, to generate the first human monoclonal antibodies against anellovirus ORF1 and define the antigenic landscape of this highly prevalent human virus.

The award funds research to isolate ORF1-specific memory B cells from donors with detectable serologic responses and generate 50 fully human monoclonal antibodies. The work will characterize these antibodies and structurally visualize discrete immunogenic epitopes within ORF1 using cryo-electron microscopy, establishing foundational resources for studying anellovirus biology and virome-host interactions. Anelloviruses infect more than 90 percent of the global population and represent the dominant eukaryotic component of the healthy human virome, yet remain among the least understood human viral families; the absence of human monoclonal antibodies and molecular tools has prevented mechanistic understanding of viral tropism, persistence pathways, and immune modulation.

The award is classified as a Project Grant (R03 mechanism). Period of performance runs from September 1, 2026, through August 31, 2028. Place of performance is New York, New York 10029. No sub-recipients are identified in the source.

Abstract

Anelloviruses are the most prevalent persistent viruses in humans, infecting more than 90% of the global population and representing the dominant eukaryotic component of the healthy human virome. Despite their extraordinary ubiquity, lifelong persistence, and strong linkage to the immune system, anelloviruses remain one of the least understood human viral families. Their small ~3 KB genome encodes only a few proteins, most notably ORF1, the putative capsid and primary immunogenic structural element. Yet, no human monoclonal antibodies exist for any anellovirus. This absence of fundamental molecular tools has prevented mechanistic understanding of viral tropism, persistence pathways, immune modulation, and virome-host interactions. Establishing an antigenic and immunologic framework for anelloviruses is therefore an essential first step toward elevating them from enigmatic components of the virome to experimentally tractable viral systems. The overall goal of this R03 proposal is to generate the first human monoclonal antibodies against the conserved immunogenic domain of anellovirus ORF1 and to define, for the first time, the antigenic landscape of this highly prevalent virus. Our central hypothesis is that discrete immunogenic epitopes within ORF1 can be resolved through human antibody responses and structurally visualized by cryo-electron microscopy, creating foundational resources for studying anellovirus biology. This hypothesis is supported by our preliminary data showing robust human IGG responses to ORF1 and by our laboratory's extensive expertise in isolating rare antigen-specific human b cells and generating monoclonal antibodies. We will pursue two complementary aims. Aim 1 will generate 50 fully human monoclonal antibodies by isolating ORF1-specific memory b cells from donors with detectable serologic responses. These antibodies will be characterized for specificity, affinity, and cross-clade recognition, and five to eight antibody-ORF1 complexes will be structurally determined by cryo-EM in collaboration with DR. Goran bajic. Aim 2 will define population-level patterns of anellovirus immunity by profiling IGG, IGA, and IGG subclass responses in more than 3,000 serum samples from existing cohorts, integrating demographic and epidemiologic metadata through multivariate, systems-level analyses to uncover determinants of exposure, transmission, and immune engagement. This project will generate the first molecular toolkit for anellovirus immunology, including human monoclonal antibodies, structural epitope maps, and deep serologic datasets. These resources will directly address major knowledge gaps, enable mechanistic studies of a ubiquitous yet understudied viral family, and accelerate broader efforts of the human virome project. The proposed work will establish the foundation necessary for future investigations into anellovirus persistence, tropism, immune modulation, and potential utility as biomarkers or therapeutic platforms.