The Utility of (1→3)-ß-D-Glucan Testing in the Diagnosis of Coccidioidomycosis in Hospitalized Immunocompromised Patients.

Coccidioidomycosis is a fungal infection endemic to the Southwestern United States which is associated with high morbidity and mortality in immunocompromised hosts. Serology is the main diagnostic tool, although less sensitive among immunocompromised hosts. (1→3)-ß-D-glucan (BDG) is a non-specific fungal diagnostic test that may identify suspected coccidioidomycosis and other invasive fungal infections. We retrospectively investigated the utility of BDG between 2017 and 2021 in immunocompromised hosts with positive Coccidioides spp. cultures at our institutions. During the study period, there were 368 patients with positive cultures for Coccidioides spp.; among those, 28 patients were immunocompromised hosts, had both Coccidioides serology and BDG results available, and met other inclusion and exclusion criteria. Half of the patients had positive Coccidioides serology, and 57% had a positive BDG ≥ 80 pg/mL. Twenty-three (82%) had at least one positive test during their hospitalization. Among immunocompromised hosts with suspicion for coccidioidomycosis, the combination of Coccidioides serology and BDG can be useful in the initial work up and the timely administration of appropriate antifungal therapy. However, both tests failed to diagnose many cases, underscoring the need for better diagnostic techniques for identifying coccidioidomycosis in this population.

Posttranscriptional Regulation of Gcr1 Expression and Activity Is Crucial for Metabolic Adjustment in Response to Glucose Availability.

The transcription factor Gcr1 controls expression of over 75% of the genes in actively growing yeast. Yet despite its widespread effects, regulation of Gcr1 itself remains poorly understood. Here, we show that posttranscriptional Gcr1 regulation is nutrient dependent. Moreover, GCR1 RNA contains a long, highly conserved intron, which allows the cell to generate multiple RNA and protein isoforms whose levels change upon glucose depletion. Intriguingly, an isoform generated by intron retention is exported from the nucleus, and its translation is initiated from a conserved, intronic translation start site. Expression of gene products from both the spliced and unspliced RNAs is essential, as cells expressing only one isoform cannot adjust their metabolic program in response to environmental changes. Finally, we show that the Gcr1 proteins form dimers, providing an elegant mechanism by which this one gene, through its regulation, can perform the repertoire of transcriptional activities necessary for fine-tuned environmental response.