Comparison of a Novel Rapid Lateral Flow Assay to Enzyme Immunoassay Results for Early Diagnosis of Coccidioidomycosis.

BACKGROUND: Coccidioidomycosis (CM) is a common cause of community-acquired pneumonia where CM is endemic. Manifestations include self-limited pulmonary infection, chronic fibrocavitary pulmonary disease, and disseminated coccidioidomycosis. Most infections are identified by serological assays including enzyme-linked immunoassay (EIA), complement fixation, and immunodiffusion. These are time-consuming and take days to result, impeding early diagnosis. A new lateral flow assay (LFA; Sona; IMMY, Norman, OK) improves time-to-result to 1 hour. METHODS: We prospectively enrolled 392 patients with suspected CM, compared the LFA with standard EIA and included procalcitonin evaluation. RESULTS: Compared with standard EIA, LFA demonstrates 31% sensitivity (95% confidence interval [CI], 20-44%) and 92% specificity (95% CI, 88-95%). Acute pulmonary disease (74%) was the most common clinical syndrome. Hospitalized patients constituted 75% of subjects, and compared with outpatients, they more frequently had ≥3 previous healthcare facility visits (P = .05), received antibacterials (P < .01), and had >3 antibacterial courses (P < .01). Procalcitonin (PCT) was <0.25 ng/mL in 52 (83%) EIA-positive patients, suggesting infection was not bacterial. CONCLUSIONS: When CM is a possible diagnosis, LFA identified nearly one-third of EIA-positive infections. Combined with PCT <0.25 ng/mL, LFA could reduce unnecessary antibacterial use by 77%.

The ROP16III-dependent early immune response determines the subacute CNS immune response and type III Toxoplasma gondii survival.

Toxoplasma gondii is an intracellular parasite that persistently infects the CNS and that has genetically distinct strains which provoke different acute immune responses. How differences in the acute immune response affect the CNS immune response is unknown. To address this question, we used two persistent Toxoplasma strains (type II and type III) and examined the CNS immune response at 21 days post infection (dpi). Contrary to acute infection studies, type III-infected mice had higher numbers of total CNS T cells and macrophages/microglia but fewer alternatively activated macrophages (M2s) and regulatory T cells (Tregs) than type II-infected mice. By profiling splenocytes at 5, 10, and 21 dpi, we determined that at 5 dpi type III-infected mice had more M2s while type II-infected mice had more pro-inflammatory macrophages and that these responses flipped over time. To test how these early differences influence the CNS immune response, we engineered the type III strain to lack ROP16 (IIIΔrop16), the polymorphic effector protein that drives the early type III-associated M2 response. IIIΔrop16-infected mice showed a type II-like neuroinflammatory response with fewer infiltrating T cells and macrophages/microglia and more M2s and an unexpectedly low CNS parasite burden. At 5 dpi, IIIΔrop16-infected mice showed a mixed inflammatory response with more pro-inflammatory macrophages, M2s, T effector cells, and Tregs, and decreased rates of infection of peritoneal exudative cells (PECs). These data suggested that type III parasites need the early ROP16-associated M2 response to avoid clearance, possibly by the Immunity-Related GTPases (IRGs), which are IFN-γ- dependent proteins essential for murine defenses against Toxoplasma. To test this possibility, we infected IRG-deficient mice and found that IIIΔrop16 parasites now maintained parental levels of PECs infection. Collectively, these studies suggest that, for the type III strain, rop16III plays a key role in parasite persistence and influences the subacute CNS immune response.