Survival of Surfactant Protein-A1 and SP-A2 Transgenic Mice After Klebsiella pneumoniae Infection, Exhibits Sex-, Gene-, and Variant Specific Differences; Treatment With Surfactant Protein Improves Survival

Abstract

Surfactant protein A (SP-A) is involved in lung innate host defense and surfactant-related functions. The human SFTPA1 and SFTPA2 genes encode SP-A1 and SP-2 proteins, and each gene has been identified with numerous genetic variants. SP-A1 and SP-A2 differentially enhance bacterial phagocytosis. Sex differences have been observed in pulmonary disease and in survival of wild type and SP-A knockout (KO) mice. The impact of human SP-A variants on survival after infection is unknown. In this study, we determined whether SP-A variants differentially affect survival of male and female mice infected with Klebsiella pneumoniae. Transgenic (TG) mice, where each carries a different human (h) SP-A1 (6A2, 6A4), SP-A2 (1A0, 1A3) variant or both variants SP-A1/SP-A2 (6A2/1A0, co-ex), and SP-A- KO, were utilized. The hTG and KO mice were infected intratracheally with K. pneumoniae bacteria, and groups of KO mice were treated with SP-A1 or SP-A2 either prior to and/or at the time of infection and survival for both experimental groups was monitored over 14 days. The binding of purified SP-A1 and SP-A2 proteins to phagocytic and non-phagocytic cells and expression of cell surface proteins in alveolar macrophages (AM) from SP-A1 and SP-A2 mice was examined. We observed gene-, variant-, and sex-specific (except for co-ex) differences with females showing better survival: (a) Gene-specific differences: co-ex = SP-A2 > SP-A1 > KO (both sexes); (b) Variant-specific survival co-ex (6A2/1A0) = 1A0 > 1A3 = 6A2 > 6A4 (both sexes); (c) KO mice treated with SPs (SP-A1 or SP-A2) proteins exhibit significantly (p < 0.05) better survival; (d) SP-A1 and SP-A2 differentially bind to phagocytic, but not to non-phagocytic cells, and AM from SP-A1 and SP-A2 hTG mice exhibit differential expression of cell surface proteins. Our results indicate that sex and SP-A genetics differentially affect survival after infection and that exogenous SP-A1/SP-A2 treatment significantly improves survival. We postulate that the differential SP-A1/SP-A2 binding to the phagocytic cells and the differential expression of cell surface proteins that bind SP-A by AM from SP-A1 and SP-A2 mice play a role in this process. These findings provide insight into the importance of sex and innate immunity genetics in survival following infection.

Donor surfactant protein A2 polymorphism and lung transplant survival

“…The change in amino acid 223 between these two variants is significant. Variants 1A 5 and 1A 0 that were associated with reduced infection risk (1A 5 ) [28] and better survival (1A 0 ) in the present study and in a recent mouse study [27] have the same amino acid, namely a glutamine. This charged amino acid may contribute to a better outcome.…”

“…Recent animal studies have shown that not only SP-A1 and SP-A2 variants distinctively affect the alveolar macrophage miRNome [25], but most relevantly they also differentially affect lung function and survival after infection [26,27]. It is therefore conceivable that SP-A gene variants may contribute to the complex etiologic pathogenesis of lung allograft dysfunction.…”

Surfactant protein A and D polymorphisms and methylprednisolone pharmacogenetics in donor lungs

“…In humanized transgenic mice, those carrying SP-A2 variant 1A0 had greater survival after Klebsiella pneumonia infection. 37 Lung transplant recipients of allografts with SP-A2 genotype 1A 0 -1A 0 had significantly greater SP-A mRNA expression before implantation, which resulted in improved clinical outcomes. 24,25 Of note, donors before organ procurement are treated with 1 to 2 g of intravenous methylprednisolone every 12 hours, and lung transplant recipients are treated with 0.5 mg/kg of methylprednisolone early post-transplant, which is slowly tapered over the first year, thereafter reaching a .…”

Using toponomics to characterize phenotypic diversity in alveolar macrophages from male mice treated with exogenous SP-A1

“…These functions include bacterial phagocytosis and cytokine production by AM [18,24,25], actin polymerization in the AM [7], and effects on the AM proteome and miRNome [26][27][28]. Moreover, the effects of SP-A variants on the regulation of the AM proteome and miRNome, survival, and pulmonary mechanics after infection, vary with sex [26][27][28][29][30].…”