Publications

OBJECTIVE

A low-cost point-of-care urine assay for lipoarabinomannan (LAM) used for screening patients prior to antiretroviral therapy (ART) rapidly diagnoses a proportion of tuberculosis (TB) cases. We determined the characteristics and outcomes of such patients.

METHODS

Adults enrolling in a South African township ART clinic were systematically screened for pulmonary TB by testing paired sputum samples using microscopy, liquid culture and Xpert MTB/RIF in a centralized laboratory. Stored urine samples were retrospectively tested for LAM using the Determine TB-LAM assay, but results did not inform treatment. Patients were followed up in the routine ART service and early (90-day) programmatic outcomes were determined. Analysis was restricted to those with CD4 cell counts below 200 cells/μl.

RESULTS

Of patients with CD4 cell counts below 200 cells/μl and complete results (n=325), 59 (18.2%) had culture-positive TB. Of these, 23 (39%) patients tested urine LAM-positive and 36 (61%) urine LAM-negative. Patients with LAM-positive TB had much lower CD4 cell counts, higher plasma viral loads, lower haemoglobin concentrations and lower BMIs compared to those with LAM-negative TB. They also had evidence of higher mycobacterial load, more frequently testing sputum smear-positive, Xpert-positive (sputum and urine) and having a shorter time to sputum culture positivity. Of five (8.5%) patients who died, four did so before TB treatment was started. All five retrospectively tested LAM-positive.

CONCLUSIONS

A low-cost point-of-care urine test for LAM rapidly diagnoses a sub-group of cases with advanced HIV-associated TB and poor prognosis. If used in combination with laboratory-based diagnostics, treatment delays would decrease and survival might be improved.

Missense mutations that reduce or abrogate myeloid cell expression of the F-BAR domain protein, proline serine threonine phosphatase-interacting protein 2 (PSTPIP2), lead to autoinflammatory disease involving extramedullary hematopoiesis, skin and bone lesions. However, little is known about how PSTPIP2 regulates osteoclast development. Here we examined how PSTPIP2 deficiency causes osteopenia and bone lesions, using the mouse PSTPIP2 mutations, cmo, which fails to express PSTPIP2 and Lupo, in which PSTPIP2 is dysfunctional. In both models, serum levels of the pro-osteoclastogenic factor, MIP-1α, were elevated and CSF-1 receptor (CSF-1R)-dependent production of MIP-1α by macrophages was increased. Treatment of cmo mice with a dual specificity CSF-1R and c-Kit inhibitor, PLX3397, decreased circulating MIP-1α and ameliorated the extramedullary hematopoiesis, inflammation, and osteopenia, demonstrating that aberrant myelopoiesis drives disease. Purified osteoclast precursors from PSTPIP2-deficient mice exhibit increased osteoclastogenesis in vitro and were used to probe the structural requirements for PSTPIP2 suppression of osteoclast development. PSTPIP2 tyrosine phosphorylation and a functional F-BAR domain were essential for PSTPIP2 inhibition of TRAP expression and osteoclast precursor fusion, whereas interaction with PEST-type phosphatases was only required for suppression of TRAP expression. Thus, PSTPIP2 acts as a negative feedback regulator of CSF-1R signaling to suppress inflammation and osteoclastogenesis.