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Functional dissection of Streptococcus pyogenes M5 protein: the hypervariable region is essential for virulence.

Waldemarsson J, Stålhammar-Carlemalm M, Sandin C, Castellino FJ, Lindahl G - PLoS ONE (2009)

Bottom Line: Because the HVR of M5 is not required for phagocytosis resistance, our data imply that this HVR plays a major but unknown role during acute infection.The B-repeat region is required for phagocytosis resistance and specifically binds Fg, suggesting that it promotes virulence by binding Fg.In particular, our data provide the first in vivo evidence that the HVR of an M protein plays a major role in virulence, focusing interest on the molecular role of this region.

View Article: PubMed Central - PubMed

Affiliation: Department of Laboratory Medicine, Division of Medical Microbiology, Lund University, Lund, Sweden.

ABSTRACT
The surface-localized M protein of Streptococcus pyogenes is a major virulence factor that inhibits phagocytosis, as determined ex vivo. Because little is known about the role of M protein in vivo we analyzed the contribution of different M protein regions to virulence, using the fibrinogen (Fg)-binding M5 protein and a mouse model of acute invasive infection. This model was suitable, because M5 is required for mouse virulence and binds mouse and human Fg equally well, as shown here. Mixed infection experiments with wild type bacteria demonstrated that mutants lacking the N-terminal hypervariable region (HVR) or the Fg-binding B-repeat region were strongly attenuated, while a mutant lacking the conserved C-repeats was only slightly attenuated. Because the HVR of M5 is not required for phagocytosis resistance, our data imply that this HVR plays a major but unknown role during acute infection. The B-repeat region is required for phagocytosis resistance and specifically binds Fg, suggesting that it promotes virulence by binding Fg. However, B-repeat mutants were attenuated even in Fg-deficient mice, implying that the B-repeats may have a second function, in addition to Fg-binding. These data demonstrate that two distinct M5 regions, including the HVR, are essential to virulence during the early stages of an infection. In particular, our data provide the first in vivo evidence that the HVR of an M protein plays a major role in virulence, focusing interest on the molecular role of this region.

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Related in: MedlinePlus

Properties of different regions in the M5 protein.This figure summarizes the role of different M5 regions in mouse virulence, phagocytosis resistance, and opsonization by antibodies. The data on mouse virulence are from this report, while the data on phagocytosis resistance and opsonization are from refs. [22] and [25]. Note that the phagocytosis and opsonization data are based on ex vivo assays. ++, major role; (+), very limited role; −, no role; n.a., not analyzed.
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pone-0007279-g005: Properties of different regions in the M5 protein.This figure summarizes the role of different M5 regions in mouse virulence, phagocytosis resistance, and opsonization by antibodies. The data on mouse virulence are from this report, while the data on phagocytosis resistance and opsonization are from refs. [22] and [25]. Note that the phagocytosis and opsonization data are based on ex vivo assays. ++, major role; (+), very limited role; −, no role; n.a., not analyzed.

Mentions: For understanding of the function of the M5 protein, it is instructive to compare the virulence data reported here with known data on phagocytosis resistance and opsonization in the M5 system (Figure 5). Mouse virulence requires the HVR and the B-repeats, as shown here. In contrast, only the B-repeat region is required for phagocytosis resistance, as determined ex vivo [22], [25]. Nevertheless, only antibodies to the HVR have opsonizing capacity in the ex vivo phagocytosis system [25]. The region in M5 that promotes phagocytosis resistance is therefore distinct from the region targeted by opsonizing antibodies. It may seem paradoxical that antibodies to the HVR are opsonizing, although the HVR is not required for phagocytosis resistance, but this finding may be explained by the surface-distal location of the HVR. In vivo, antibodies to the HVR may also confer protection by blocking the essential function of this region. The lack of opsonization by antibodies to the B- and C-repeat regions may be explained by the ability of bound human plasma proteins to block antibody access to these regions [25]. Together, these comparisons indicate that the three regions in M5 have distinct functions and properties.


Functional dissection of Streptococcus pyogenes M5 protein: the hypervariable region is essential for virulence.

Waldemarsson J, Stålhammar-Carlemalm M, Sandin C, Castellino FJ, Lindahl G - PLoS ONE (2009)

Properties of different regions in the M5 protein.This figure summarizes the role of different M5 regions in mouse virulence, phagocytosis resistance, and opsonization by antibodies. The data on mouse virulence are from this report, while the data on phagocytosis resistance and opsonization are from refs. [22] and [25]. Note that the phagocytosis and opsonization data are based on ex vivo assays. ++, major role; (+), very limited role; −, no role; n.a., not analyzed.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2749438&req=5

pone-0007279-g005: Properties of different regions in the M5 protein.This figure summarizes the role of different M5 regions in mouse virulence, phagocytosis resistance, and opsonization by antibodies. The data on mouse virulence are from this report, while the data on phagocytosis resistance and opsonization are from refs. [22] and [25]. Note that the phagocytosis and opsonization data are based on ex vivo assays. ++, major role; (+), very limited role; −, no role; n.a., not analyzed.
Mentions: For understanding of the function of the M5 protein, it is instructive to compare the virulence data reported here with known data on phagocytosis resistance and opsonization in the M5 system (Figure 5). Mouse virulence requires the HVR and the B-repeats, as shown here. In contrast, only the B-repeat region is required for phagocytosis resistance, as determined ex vivo [22], [25]. Nevertheless, only antibodies to the HVR have opsonizing capacity in the ex vivo phagocytosis system [25]. The region in M5 that promotes phagocytosis resistance is therefore distinct from the region targeted by opsonizing antibodies. It may seem paradoxical that antibodies to the HVR are opsonizing, although the HVR is not required for phagocytosis resistance, but this finding may be explained by the surface-distal location of the HVR. In vivo, antibodies to the HVR may also confer protection by blocking the essential function of this region. The lack of opsonization by antibodies to the B- and C-repeat regions may be explained by the ability of bound human plasma proteins to block antibody access to these regions [25]. Together, these comparisons indicate that the three regions in M5 have distinct functions and properties.

Bottom Line: Because the HVR of M5 is not required for phagocytosis resistance, our data imply that this HVR plays a major but unknown role during acute infection.The B-repeat region is required for phagocytosis resistance and specifically binds Fg, suggesting that it promotes virulence by binding Fg.In particular, our data provide the first in vivo evidence that the HVR of an M protein plays a major role in virulence, focusing interest on the molecular role of this region.

View Article: PubMed Central - PubMed

Affiliation: Department of Laboratory Medicine, Division of Medical Microbiology, Lund University, Lund, Sweden.

ABSTRACT
The surface-localized M protein of Streptococcus pyogenes is a major virulence factor that inhibits phagocytosis, as determined ex vivo. Because little is known about the role of M protein in vivo we analyzed the contribution of different M protein regions to virulence, using the fibrinogen (Fg)-binding M5 protein and a mouse model of acute invasive infection. This model was suitable, because M5 is required for mouse virulence and binds mouse and human Fg equally well, as shown here. Mixed infection experiments with wild type bacteria demonstrated that mutants lacking the N-terminal hypervariable region (HVR) or the Fg-binding B-repeat region were strongly attenuated, while a mutant lacking the conserved C-repeats was only slightly attenuated. Because the HVR of M5 is not required for phagocytosis resistance, our data imply that this HVR plays a major but unknown role during acute infection. The B-repeat region is required for phagocytosis resistance and specifically binds Fg, suggesting that it promotes virulence by binding Fg. However, B-repeat mutants were attenuated even in Fg-deficient mice, implying that the B-repeats may have a second function, in addition to Fg-binding. These data demonstrate that two distinct M5 regions, including the HVR, are essential to virulence during the early stages of an infection. In particular, our data provide the first in vivo evidence that the HVR of an M protein plays a major role in virulence, focusing interest on the molecular role of this region.

Show MeSH
Related in: MedlinePlus