Discovery of a Unique Set of Dog-Seroreactive Coccidioides Proteins Using Nucleic Acid Programmable Protein Array

Abstract

Valley Fever (VF), caused by fungi in the genus Coccidioides, is a prevalent disease in southwestern and western parts of the United States that affects both humans and animals, such as dogs. Although the immune responses to infection with Coccidioides spp. are not fully characterized, antibody-detection assays are used in conjunction with clinical presentation and radiologic findings to aid in the diagnosis of VF. These assays often use Complement Fixation (CF) and Tube Precipitin (TP) antigens as the main targets of IgG and IgM reactivity, respectively. Our group previously reported evidence of over 800 genes expressed at the protein level in C. posadasii. However, antibody reactivity to the majority of these proteins has never been explored. Using a new, high-throughput screening technology, the Nucleic Acid Programmable Protein Array (NAPPA), we screened serum specimens from dogs against 708 of these previously identified proteins for IgG reactivity. Serum from three separate groups of dogs was analyzed and revealed a small panel of proteins to be further characterized for immuno-reactivity. In addition to CF/CTS1 antigen, sera from most infected dogs showed antibody reactivity to endo-1,3-betaglucanase, peroxisomal matrix protein, and another novel reactive protein, CPSG_05795. These antigens may provide additional targets to aid in antibody-based diagnostics.

Keywords: antibodies; coccidioidomycosis; diagnostics; dogs; valley fever.

Figure 1

Venn diagram of the thirty-three overlapping seroreactive proteins from the laboratory-infected and seropositive naturally infected dogs. The thirty-three overlapping proteins and their protein identifiers are listed in the table to the right of the diagram.

Figure 2

Venn diagram of the eight overlapping seroreactive proteins from all three groups: laboratory-infected (blue circle), sero-positive endemic dogs (green), and vaccine + challenge (pink). The eight overlapping proteins and their protein identifiers are listed in the table to the right of the diagram.