Comprehensive profiling of antibody responses to the human anellome using programmable phage display

Anelloviruses represent a major constituent of the commensal human virome; however, little is known about their immunobiology. Here, we present "AnelloScan," a T7 phage library representing the open reading frame 1 (ORF1), ORF2, ORF3, and torque teno virus (TTV)-derived apoptosis-inducing protein (TAIP) sequences of more than 800 human anelloviruses and profile the antibody reactivities of serum samples from a cross-sectional cohort of 156 subjects by using phage-immunoprecipitation sequencing (PhIP-Seq). A majority of anellovirus peptides are not reactive in any of the subjects tested (n = ∼28,000; ∼85% of the library). Antibody-reactive peptides are largely restricted to the C-terminal region of the capsid protein ORF1. Moreover, using a longitudinal cohort of matched blood-transfusion donors and recipients, we find that most transmitted anelloviruses do not elicit a detectable antibody reactivity in the recipient and that the remainder elicit delayed responses appearing ∼100-150 days after transfusion.