Surfactant Protein A2 (SP-A2) Variants Expressed in CHO Cells Stimulate Phagocytosis of Pseudomonas aeruginosa More than Do SP-A1 Variants
- 1 March 2007
- journal article
- research article
- Published by American Society for Microbiology in Infection and Immunity
- Vol. 75 (3), 1403-1412
- https://doi.org/10.1128/iai.01341-06
Abstract
Surfactant protein A (SP-A) enhances phagocytosis of Pseudomonas aeruginosa . Two functional genes, SP-A1 and SP-A2 , encode human SP-A. As we showed before, baculovirus-mediated insect cell-expressed SP-A2 enhances the association of P. aeruginosa with rat alveolar macrophages (rAMs) more than does SP-A1. However, true phagocytosis (internalization) was not shown, and insect cell derived proteins lack or are defective in certain mammalian posttranslational modifications that may be important for SP-A1 and SP-A2 activity and specificity. Here we used SP-A1 (6A 2 , 6A 4 ) and SP-A2 (1A 0 , 1A 1 ) allele variants expressed by CHO (Chinese hamster ovary) mammalian cells to study their effect on association and/or internalization of P. aeruginosa by rAMs and/or human AMs (hAMs) and to study if phagocytosis can be modulated differentially and/or more effectively by CHO cell-expressed SP-A variants than by insect-cell expressed SP-A variants. For cell association and internalization assessments, light microscopy and fluorescence-activated cell sorter analyses were used, respectively. We found the following for the first time. (i) SP-A2 variants enhanced phagocytosis (cell association and/or internalization) of P. aeruginosa more than SP-A1 variants did, and the cell association correlated with internalization. (ii) Differences in the activities of SP-A variants were observed in the following order: 1A 1 >1A 0 >6A 2 >6A 4 . (iii) rAMs, although more active than hAMs, are an appropriate model, as SP-A2 variants exhibited activity higher than that seen for SP-A1 variants with either rAMs or hAMs. (iv) CHO cell-expressed SP-A was considerably more active than insect cell-expressed variants. We conclude that SP-A2 variants stimulate phagocytosis of P. aeruginosa more effectively than SP-A1 variants and that posttranslational modifications positively influence the phagocytic activity of SP-A.Keywords
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