Background: Pulmonary macrophage transplantation (PMT) therapy is a promising approach for children with hereditary pulmonary alveolar proteinosis (hPAP), a recessive disease of surfactant accumulation and respiratory failure caused by mutations in either CSF2RA or CSF2RB (encoding GM-CSF receptor α and β, respectively). We previously reported that PMT therapy of hPAP in Csf2rb gene-deficient mice was well-tolerated, safe and highly efficacious (Nature 514:450-5; 2014). Here, we report on the efficacy of PMT in Csf2ra gene-deficient mice, a recently established model of hPAP in children with CSF2RA mutations, which account for 90% of hPAP patients.
Methods: Csf2ra gene-ablated (KO) mice were generated by CRISPR/Cas9 genome-editing and received wild type bone marrow-derived macrophages as a single, intrapulmonary instillation (2x106 cells/mouse) and were evaluated two months later for tolerance, safety, and therapeutic efficacy.
Results: In untreated KO mice, PAP lung disease severity worsened progressively over time similar to hPAP in children, as demonstrated by a progressive increase in bronchoalveolar lavage (BAL) turbidity (PAP disease severity). In marked contrast, two months after a single PMT treatment, BAL turbidity was markedly reduced in PMT-treated compared to untreated KO mice (P<0.01). Further, AMs in PMT-treated KO mice were small, not foamy in appearance, immunostained positive for CD116 (GM-CSF receptor α), and far fewer stained positive with oil-red-O than AMs in untreated KO mice. A single PMT treatment also reduced PAP biomarkers in BAL including levels of cholesterol, GM-CSF, M-CSF and MCP-1 (P<0.05). Finally, PMT therapy did not result in adverse events in any mice.
Conclusion: Results demonstrate that Csf2ra gene-deficient mice comprise a clinically relevant model of human hPAP caused by CSF2RA mutations and a single PMT resulted in macrophage engraftment and therapeutic efficacy with no evidence of treatment emergent adverse events. These results strongly support the feasibility of translating PMT as a novel genetic/pharmacotherapeutic for children with hPAP.