CD46 Transgenic Mouse Model of Necrotizing Fasciitis Caused by Streptococcus pyogenes Infection

Abstract

We developed a human CD46-expressing transgenic (Tg) mouse model of subcutaneous (s.c.) infection into both hind footpads with clinically isolated 11 group A streptococcus (GAS) serotype M1 strains. When the severity levels of foot lesions at 72 h and the mortality rates by 336 h were compared after s.c. infection with 1 ؋ 10 7 CFU of each GAS strain, the GAS472 strain, isolated from the blood of a patient suffering from streptococcal toxic shock syndrome (STSS), induced the highest severity levels and mortality rates. GAS472 led to a 100% mortality rate in CD46 Tg mice after only 168 h postinfection through the supervention of severe necrotizing fasciitis (NF) of the feet. In contrast, GAS472 led to a 10% mortality rate in non-Tg mice through the supervention of partial necrotizing cutaneous lesions of the feet. The footpad skin sections of CD46 Tg mice showed hemorrhaging and necrotic striated muscle layers in the dermis, along with the exfoliation of epidermis with intracellular edema until 48 h after s.c. infection with GAS472. Thereafter, the bacteria proliferated, reaching a 90-fold or 7-fold increase in the livers of CD46 Tg mice or non-Tg mice, respectively, for 24 h between 48 and 72 h after s.c. infection with GAS472. As a result, the infected CD46 Tg mice appeared to suffer severe liver injuries. These findings suggest that human CD46 enhanced the progression of NF in the feet and the exponential growth of bacteria in deep tissues, leading to death.Group A streptococci (GAS), which are among the most common human pathogens, can cause a variety of uncomplicated superficial skin infections such as impetigo/pyoderma or throat infections, including streptococcal pharyngitis (sore throat) and tonsillitis (3). In addition, patients suffering from acute and complicated GAS infections, in particular streptococcal toxic shock syndrome (STSS) associated with severe necrotizing fasciitis (NF), have high mortality rates (4). M proteins, which attach to the cell wall, are one of the important virulence factors that GAS possess (15). The various GAS strains have more than 100 different antigenically distinguishable M proteins (46), and GAS serotype M1 strains are regarded as a highly virulent group (3).Membrane cofactor protein (MCP; CD46), which is expressed in every cell type except erythrocytes, is implicated as a receptor for at least six human pathogens (four viruses and two bacteria), including measles virus (9, 31, 35), herpesvirus 6 (40), adenovirus groups B (17, 41) and D (48), pathogenic Neisseria (23), and GAS (37). Human CD46-expressing transgenic (Tg) mice are susceptible to streptococcal disease (30). When CD46 Tg and non-Tg mice were infected intravenously (i.v.) with GAS, the bacteremia levels, frequency of arthritis, and mortality rate were higher in CD46 Tg mice than in non-Tg mice (30). Unfortunately, this animal model does not reflect the natural infection process in the human host. Consequently, we have attempted to establish a CD46 Tg mouse model of skin and soft tissue infection with GAS that...

Lactobacilli Reduce Cell Cytotoxicity Caused by Streptococcus pyogenes by Producing Lactic Acid That Degrades the Toxic Component Lipoteichoic Acid

“…In addition, pathogeninduced apoptosis and necrosis lead to shedding of the cell surface complement regulator CD46 (14,25). Shed CD46 binds to the surface of GAS and increases survival of the bacteria in the blood (23,27).…”

A CD46 transgenic mouse model for studying the histopathology of arthritis caused by subcutaneous infection with Streptococcus dysgalactiae subspecies equisimilis

“…of the virulent strain of GAS (GAS472) isolated from the blood of a patient suffering from streptococcal toxic shock syndrome (Matsui et al, 2009). This mouse model showed progressive NF in the feet and exponential growth of bacteria in deep tissues, leading to death with a 100 % mortality rate by day 14 after infection (Matsui et al, 2009). Consequently, we had expected that s.c. infection with RE378 would cause a high mortality rate associated with NF in the feet of CD46 Tg mice.…”

“…Human CD46-expressing Tg mice were donated by Dr J. P. Atkinson of Washington University (St Louis, MO, USA). C57BL/6J mice, employed as the corresponding non-Tg mice, were obtained from Charles River Japan, where they were established as described previously (Matsui et al, 2009). All mice were bred at the animal facility at Kitasato University, and all mouse experiments were performed in accordance with institutional guidelines under an approved protocol.…”

“…per footpad of RE378 in a stationary growth phase. After s.c. infection, the survival rates were observed every day for 28 days, and the viable counts of bacteria in the liver, spleen, kidneys and popliteal lymph nodes (PLNs) were determined by plating onto sheep-blood agar (Matsui et al, 2009(Matsui et al, , 2011.…”

“…Transgenic (Tg) mice expressing human genes have been used as recipients in humanized mouse models for GAS infection. Mice carrying the human plasminogen (Maurer et al, 2006;Sun et al, 2004) or CD46 (also known as membrane cofactor protein, MCP) (Lövkvist et al, 2008;Matsui et al, 2009) have been shown to be more susceptible to GAS infection than non-Tg mice. Human CD46 has been reported to serve as a receptor for the bacterial cell surface M protein (the emm gene product) of GAS (Okada et al, 1994Perez-Casal et al, 1995).…”