# Structure-guided design of Anaplasma P44 protein-based chimeric antigens for serodiagnosis of anaplasmosis in dogs Article · Cramer NA, Brangulis K, Mann SN, Herrera FM, Breitschwerdt EB, Carlyon JA, Marconi RT - Archive id: doi:10.1128/iai.00167-26 - Published: 2026-09-15 - Venue: Infection and immunity - DOI: https://doi.org/10.1128/iai.00167-26 - PMID: 42742337 - Citations: 0 - Source URL: https://doi.org/10.1128/iai.00167-26 - Provenance: europepmc ## Abstract Canine and human anaplasmosis are tick-borne diseases caused by the obligate intracellular bacteria, Anaplasma phagocytophilum and Anaplasma platys , respectively. In veterinary medicine, peptides derived from the immunodominant P44 protein are used to detect antibodies in serological point-of-care tests for anaplasmosis. To inform efforts to develop improved chimeric diagnostic proteins for anaplasmosis, the structure of the predicted surface-exposed domain (residues 151-308) of P44 was determined at a resolution of 1.65 Å. This domain comprises six α-helices and six short β-strands connected by loop regions. A structural similarity search of the P44 151-308 domain using the Distance Matrix Alignment server against the AlphaFold Database revealed that the domain represents a previously uncharacterized protein fold. The determined structure is consistent with AlphaFold v2 predictions, which further predict the core of P44 to be an eight-stranded β-barrel. Using P44 fragments, immunodominant epitopes were mapped within residues 151-308. Four chimeric genes (ADC1, ADC2, ADC3, and ADC4) were designed that incorporate the analogous immunodominant P44 domains from A. phagocytophilum and A. platys . The recombinant ADC chimerics were assessed for sensitivity and specificity by screening with serum from dogs diagnosed with anaplasmosis, Lyme disease, or ehrlichiosis, with sera from specific pathogen-free dogs serving as negative controls. Accuracy was further demonstrated by screening characterized serum samples from coyotes ( Canis latrans ; wild canids). The ADC1 chimeric provided 100% sensitivity and 98.04% specificity. The sensitivity and specificity of ADC1 support its potential use as a diagnostic Ag for anaplasmosis. _Abstract reproduced under CC-BY (article license as recorded by Europe PMC; abstract reproduced unmodified apart from markup removal)._ Topics: [AI Protein Design & Structure Prediction](https://space-kitty.com/topics/protein-design) --- Space Kitty Archive · https://space-kitty.com · API: https://space-kitty.com/api/v1 · MCP: https://space-kitty.com/mcp · Premium: $0.20/request via x402 (Base Sepolia (testnet)). Metadata: arXiv (CC0), OpenAlex (CC0), Europe PMC (CC BY/CC0 works), ClinicalTrials.gov.