Development of an enzyme immunoassay for detection of antibodies against Coccidioides in dogs and other mammalian species

Abstract

Coccidioides is a soil-dwelling fungus that causes coccidioidomycosis, a disease also known as Valley fever, which affects humans and a variety of animal species. Recent findings of Coccidioides in new, unexpected areas of the United States have demonstrated the need for a better understanding of its geographic distribution. Large serological studies on animals could provide important information on the geographic distribution of this pathogen. To facilitate such studies, we used protein A/G, a recombinant protein that binds IgG antibodies from a variety of mammalian species, to develop an enzyme immunoassay (EIA) that detects IgG antibodies against Coccidioides in a highly sensitive and high-throughput manner. We showed the potential of this assay to be adapted to multiple animal species by testing a collection of serum and/or plasma samples from dogs, mice, and humans with or without confirmed coccidioidomycosis. We then evaluated the performance of the assay in dogs, using sera from dogs residing in a highly endemic area, and found seropositivity rates significantly higher than those in dogs of non-endemic areas. We further evaluated the specificity of the assay in dogs infected with other fungal pathogens known to cross-react with Coccidioides. Finally, we used the assay to perform a cross-sectional serosurvey investigating dogs from Washington, a state in which infection with Coccidioides has recently been documented. In summary, we have developed a Coccidioides EIA for the detection of antibodies in canines that is more sensitive and has higher throughput than currently available methods, and by testing this assay in mice and humans, we have shown a proof of principle of its adaptability for other animal species.

Re-drawing the Maps for Endemic Mycoses

“…In 1957, Edwards et al used skin testing to delineate the endemic areas within the USA [ 6 , 121 ]. Subsequently, public health surveillance as well as various serological and molecular methods have been utilized to help improve understanding of the geographic distribution of coccidioidomycosis within the USA [ 119 , 125 – 127 ]. In 2002, Fisher et al isolated two distinct pathogenic species based on phylogenetic analyses: C. immitis and C. posadasii [ 128 ].…”

“…In 2002, Fisher et al isolated two distinct pathogenic species based on phylogenetic analyses: C. immitis and C. posadasii [ 128 ]. C. immitis is primarily found in the Central Valley of California but has now been found as far north as eastern Washington state [ 119 , 129 – 134 ]. C. posadasii, is found in the desert areas of Arizona, Texas, Utah, Mexico, and Central and South America [ 6 , 133 , 135 – 140 ].…”

Soil and climactic predictors of canine coccidioidomycosis seroprevalence in Washington State: An ecological cross‐sectional study

“…No a priori sample size calculations were performed. Outcome was determined on the basis of IgG enzyme immunoassays performed on serum samples at the Centers for Disease Control and Prevention (Chow et al, ). For this analysis, indeterminate and positive results were collapsed as a single “positive” group.…”

Coccidioidomicosis en caninos y felinos: hallazgos clínicos, diagnóstico y tratamiento

“…Reciente mente se probó un inmunoensayo enzimático en el cual los anticuerpos IgG son reconocidos por la proteína A/G como herramienta para estudiar la expansión de la región endémica para la coccidioi domicosis. Este ensayo, con un punto de corte adecuado, puede ser adaptado a otras especies (Chow et al, 2017).…”