Limits...
Increased Susceptibility of Humanized NSG Mice to Panton-Valentine Leukocidin and Staphylococcus aureus Skin Infection.

Tseng CW, Biancotti JC, Berg BL, Gate D, Kolar SL, Müller S, Rodriguez MD, Rezai-Zadeh K, Fan X, Beenhouwer DO, Town T, Liu GY - PLoS Pathog. (2015)

Bottom Line: Staphylococcus aureus is a leading cause of skin and soft-tissue infections worldwide.However a supra-physiologic S. aureus inoculum is required to establish gross murine skin pathology.PMX53, a human C5aR inhibitor, blocked PVL-induced cellular cytotoxicity in vitro and reduced the size difference of lesions induced by the PVL+ and PVL- S. aureus, but PMX53 also reduced recruitment of neutrophils and exacerbated the infection.

View Article: PubMed Central - PubMed

Affiliation: Division of Pediatric Infectious Diseases and the Immunobiology Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America.

ABSTRACT
Staphylococcus aureus is a leading cause of skin and soft-tissue infections worldwide. Mice are the most commonly used animals for modeling human staphylococcal infections. However a supra-physiologic S. aureus inoculum is required to establish gross murine skin pathology. Moreover, many staphylococcal factors, including Panton-Valentine leukocidin (PVL) elaborated by community-associated methicillin-resistant S. aureus (CA-MRSA), exhibit selective human tropism and cannot be adequately studied in mice. To overcome these deficiencies, we investigated S. aureus infection in non-obese diabetic (NOD)/severe combined immune deficiency (SCID)/IL2rγ (NSG) mice engrafted with human CD34+ umbilical cord blood cells. These "humanized" NSG mice require one to two log lower inoculum to induce consistent skin lesions compared with control mice, and exhibit larger cutaneous lesions upon infection with PVL+ versus isogenic PVL- S. aureus. Neutrophils appear important for PVL pathology as adoptive transfer of human neutrophils alone to NSG mice was sufficient to induce dermonecrosis following challenge with PVL+ S. aureus but not PVL- S. aureus. PMX53, a human C5aR inhibitor, blocked PVL-induced cellular cytotoxicity in vitro and reduced the size difference of lesions induced by the PVL+ and PVL- S. aureus, but PMX53 also reduced recruitment of neutrophils and exacerbated the infection. Overall, our findings establish humanized mice as an important translational tool for the study of S. aureus infection and provide strong evidence that PVL is a human virulence factor.

Show MeSH

Related in: MedlinePlus

PVL contributes to dermonecrosis in NSG mice adoptively transferred with human PMN.NSG mice were injected i.v. with 5 x 106 human PMN (n = 17) or mouse PMN (n = 7). Three hours later, the mice were infected on the left flank with 106 CFU WT S. aureus and on the right flank with 106 CFU PVL- isogenic S. aureus. The mice were sacrificed on d 3 post-infection. Shown are (A) skin lesion sizes on d 3 and (B) MPO activity at 3 h and 24 h. Red bar = mean, ***: p < 0.005.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4664407&req=5

ppat.1005292.g003: PVL contributes to dermonecrosis in NSG mice adoptively transferred with human PMN.NSG mice were injected i.v. with 5 x 106 human PMN (n = 17) or mouse PMN (n = 7). Three hours later, the mice were infected on the left flank with 106 CFU WT S. aureus and on the right flank with 106 CFU PVL- isogenic S. aureus. The mice were sacrificed on d 3 post-infection. Shown are (A) skin lesion sizes on d 3 and (B) MPO activity at 3 h and 24 h. Red bar = mean, ***: p < 0.005.

Mentions: It has been hypothesized that human PMN play a central role in PVL-mediated injury. Among immune cells, human PMN express the highest level of C5aR on their surface [15] and are the most susceptible to the cytotoxic effect of PVL. We sought to address the role of PMN in PVL-related pathology by performing cellular depletion experiments, but were unable to identify a source of depleting antibodies against human PMN. As an alternative, we injected NSG mice i.v. with PMN isolated from human volunteers or BALB/c mice. After 3 h, we infected the mice with 106 CFU isogenic WT and PVL-S. aureus. Overall, mice injected with human PMN and WT bacteria produced prominent lesions in only about half of the animals (Fig 3A). Therefore, this simplified model of humanized mice is not as robust as NSG mice injected neonatally with human CD34+ cells. However, consistent with findings from the humanized NSG mice, PVL+S. aureus induced significantly larger lesions compared to the isogenic PVL- mutant (Fig 3A), while PVL+ and PVL-S. aureus induced smaller lesions of comparable sizes in NSG mice injected with mouse PMN. As was observed in infected humanized NSG mice, there was a transient increase in MPO at 3 h but not at 24 h post-infection in NSG mice adoptively transferred with human PMN (Fig 3B). Evaluation at the infection site for CFU and human cytokines secreted by human PMN also showed no differences between the WT and PVL- mutant groups (S5 Fig).


Increased Susceptibility of Humanized NSG Mice to Panton-Valentine Leukocidin and Staphylococcus aureus Skin Infection.

Tseng CW, Biancotti JC, Berg BL, Gate D, Kolar SL, Müller S, Rodriguez MD, Rezai-Zadeh K, Fan X, Beenhouwer DO, Town T, Liu GY - PLoS Pathog. (2015)

PVL contributes to dermonecrosis in NSG mice adoptively transferred with human PMN.NSG mice were injected i.v. with 5 x 106 human PMN (n = 17) or mouse PMN (n = 7). Three hours later, the mice were infected on the left flank with 106 CFU WT S. aureus and on the right flank with 106 CFU PVL- isogenic S. aureus. The mice were sacrificed on d 3 post-infection. Shown are (A) skin lesion sizes on d 3 and (B) MPO activity at 3 h and 24 h. Red bar = mean, ***: p < 0.005.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664407&req=5

ppat.1005292.g003: PVL contributes to dermonecrosis in NSG mice adoptively transferred with human PMN.NSG mice were injected i.v. with 5 x 106 human PMN (n = 17) or mouse PMN (n = 7). Three hours later, the mice were infected on the left flank with 106 CFU WT S. aureus and on the right flank with 106 CFU PVL- isogenic S. aureus. The mice were sacrificed on d 3 post-infection. Shown are (A) skin lesion sizes on d 3 and (B) MPO activity at 3 h and 24 h. Red bar = mean, ***: p < 0.005.
Mentions: It has been hypothesized that human PMN play a central role in PVL-mediated injury. Among immune cells, human PMN express the highest level of C5aR on their surface [15] and are the most susceptible to the cytotoxic effect of PVL. We sought to address the role of PMN in PVL-related pathology by performing cellular depletion experiments, but were unable to identify a source of depleting antibodies against human PMN. As an alternative, we injected NSG mice i.v. with PMN isolated from human volunteers or BALB/c mice. After 3 h, we infected the mice with 106 CFU isogenic WT and PVL-S. aureus. Overall, mice injected with human PMN and WT bacteria produced prominent lesions in only about half of the animals (Fig 3A). Therefore, this simplified model of humanized mice is not as robust as NSG mice injected neonatally with human CD34+ cells. However, consistent with findings from the humanized NSG mice, PVL+S. aureus induced significantly larger lesions compared to the isogenic PVL- mutant (Fig 3A), while PVL+ and PVL-S. aureus induced smaller lesions of comparable sizes in NSG mice injected with mouse PMN. As was observed in infected humanized NSG mice, there was a transient increase in MPO at 3 h but not at 24 h post-infection in NSG mice adoptively transferred with human PMN (Fig 3B). Evaluation at the infection site for CFU and human cytokines secreted by human PMN also showed no differences between the WT and PVL- mutant groups (S5 Fig).

Bottom Line: Staphylococcus aureus is a leading cause of skin and soft-tissue infections worldwide.However a supra-physiologic S. aureus inoculum is required to establish gross murine skin pathology.PMX53, a human C5aR inhibitor, blocked PVL-induced cellular cytotoxicity in vitro and reduced the size difference of lesions induced by the PVL+ and PVL- S. aureus, but PMX53 also reduced recruitment of neutrophils and exacerbated the infection.

View Article: PubMed Central - PubMed

Affiliation: Division of Pediatric Infectious Diseases and the Immunobiology Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America.

ABSTRACT
Staphylococcus aureus is a leading cause of skin and soft-tissue infections worldwide. Mice are the most commonly used animals for modeling human staphylococcal infections. However a supra-physiologic S. aureus inoculum is required to establish gross murine skin pathology. Moreover, many staphylococcal factors, including Panton-Valentine leukocidin (PVL) elaborated by community-associated methicillin-resistant S. aureus (CA-MRSA), exhibit selective human tropism and cannot be adequately studied in mice. To overcome these deficiencies, we investigated S. aureus infection in non-obese diabetic (NOD)/severe combined immune deficiency (SCID)/IL2rγ (NSG) mice engrafted with human CD34+ umbilical cord blood cells. These "humanized" NSG mice require one to two log lower inoculum to induce consistent skin lesions compared with control mice, and exhibit larger cutaneous lesions upon infection with PVL+ versus isogenic PVL- S. aureus. Neutrophils appear important for PVL pathology as adoptive transfer of human neutrophils alone to NSG mice was sufficient to induce dermonecrosis following challenge with PVL+ S. aureus but not PVL- S. aureus. PMX53, a human C5aR inhibitor, blocked PVL-induced cellular cytotoxicity in vitro and reduced the size difference of lesions induced by the PVL+ and PVL- S. aureus, but PMX53 also reduced recruitment of neutrophils and exacerbated the infection. Overall, our findings establish humanized mice as an important translational tool for the study of S. aureus infection and provide strong evidence that PVL is a human virulence factor.

Show MeSH
Related in: MedlinePlus