LDL acts as an opsonin enhancing the phagocytosis of group A Streptococcus by monocyte and whole human blood

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Web End = Med Microbiol Immunol (2016) 205:155162 DOI 10.1007/s00430-015-0436-8

ORIGINAL INVESTIGATION

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Web End = LDL acts as an opsonin enhancing the phagocytosis of group A Streptococcus by monocyte and whole human blood

Lulei Zhou1,2 Ling Liu1,2 Jinli Yang1,2 Yuxin Li1,2 Wencheng Bai1,2 Na Liu1,2 Wenlong Li1,2 Yumin Gao1,3 Liping Xu1,4 Zhi Liu1,2 Runlin Han1,2

Received: 28 May 2015 / Accepted: 6 September 2015 / Published online: 21 September 2015 The Author(s) 2015. This article is published with open access at Springerlink.com

the phagocytosis of LDL-opsonized GAS but anti-CD4 antibody did not. Most of AM41-type GAS cells were killed in human blood, whereas only a few CM41-type cells were phagocytosed. Moreover, recombinant Scl1 (rScl1) derived from M41-type GAS could signicantly decrease the opsonophagocytosis of AM41 but not CM41-type GAS because the rScl1 competitively blocked the binding of AM41-type GAS to LDL. Therefore, our ndings suggest that LDL may be an opsonin to enhance CD36-dependent opsonic phagocytosis of GAS by monocyte.

Keywords Low-density lipoprotein Group A Streptococcus Opsonin Phagocytosis Monocyte

Abbreviations

GAS Group AStreptococcusAM41 M41-type GAS (ATCC 12373)CM41 M41-type GAS (CMCC 32198)LDL

Low-density lipoprotein

Introduction

Streptococcus pyogenes [group A Streptococcus (GAS)] can cause a number of suppurative infections, including pharyngitis, impetigo/pyoderma, erysipelas, cellulitis, necrotizing fasciitis, toxic streptococcal syndrome, and scarlet fever, as well as nonsuppurative sequelae including acute rheumatic fever and acute glomerulonephritis [1].Based on the surface M protein, GAS is serologically separated into over 200 M protein serotypes [2]. Streptococcal collagen-like protein 1 (Scl1) as one of the virulence factors of GAS is found on the cell surface of many M-type GAS [3]. Although Scl1s expressed by different M-type GAS share similar triple helix structure their amino acid

Abstract Low-density lipoprotein (LDL) binds to group A Streptococcus (GAS) through Sc11 protein, and scavenger receptor CD36 of monocyte mediates the endocytosis of native or modied LDL. Therefore, we hypothesized that LDL might be an opsonin enhancing the phagocytosis of LDL-bound GAS by monocyte. The results showed that LDL could signicantly promote U937 cell to phagocytose M28 (ATCC BAA1064) and M41 (ATCC 12373, AM41)-type GAS, and the...