Tion resolution, the PVL toxoid left much to be desired in terms of its use as a promising therapeutic for S. aureus (56, 58). Insomuch as these PVL immunization studies by Gladstone et al. did not culminate in the development of an effective anti-S. aureus therapeutic agent, they did provide suitable evidence that an immune response can be mounted against PVL in humans. Interestingly, much of the immunization efforts by Gladstone and colleagues were conducted on patients with already established skin and soft tissue infections (SSTIs) (56). Thus, immunization during such active infections may have had limited value. Likewise, it is difficult to ascertain whether infection resolution was due to the administration of the toxoid or simply to natural clearance over the course of infection. It was also unknown whether or not the subjects of that study were infected with strains of S. aureus that contained the pvl genes. More recent research that calls into question the role of PVL in the pathogenesis of SSTIs further limits the interpretation of toxoid efficacy in the studies by Gladstone et al., as the majority of these patients had SSTIs. Regardless, the work of Gladstone and colleagues was at least suggestive of the potential therapeutic value associated with leucocidin immunization and supported further investigation. Importantly, these studies were conducted at a time when there was little appreciation for the diversity of leucocidins present within a given strain of S. aureus (19?1). Given the Mikamycin B site redundant and nonredundant activities of individual leucocidins, it is perhaps not surprising that the administration of a toxoid composed strictly of PVL displayed limited efficacy (19?1). Our current appreciation for the redundancies in cytotoxic molecules expressed by S. aureus makes it clear that an effective strategy to promote enhanced resolution of infection by the immune system is going to require the targeting of more than one toxic molecule (19). In particular, the diverse repertoire of immune evasion molecules produced by S. aureus will certainly necessitate the consideration of multicomponent therapeutics and vaccines (22, 23). In the past 10 years, our increased knowledge of leucocidin diversity, directed targeting of host immune cells, and their unique cellular specificities has left researchers better poised to test whether the development of novel therapeutic agents targeting multiple S. aureus leucocidins will prove to be an efficacious treatment strategy. In the last 50 years, few studies have sought to directly evaluate the therapeutic potential of antileucocidin-based treatment modalities. One study, which immunized rabbits with PVL in order to prevent the pathological outcomes of mastitis, showed no effi-cacy (325). In contrast, another study suggested that the administration of intravenous immunoglobulin (IVIG) might have potential therapeutic value, as it is likely to contain a number of antitoxin antibodies. Gauduchon et al. demonstrated that IVIG is capable of neutralizing the toxic activity of PVL in vitro and suggested that its use in conjunction with antibiotics may improve outcomes in patients with invasive S. aureus infection (326). get Mequitazine However, IVIG is currently not recommended as a routine course of therapy, even for invasive S. aureus infection, despite its ability to neutralize PVL quite efficiently (4). This is due in part to conflicting evidence surrounding whether or not inhibition of PVL by IVIG is beneficial du.Tion resolution, the PVL toxoid left much to be desired in terms of its use as a promising therapeutic for S. aureus (56, 58). Insomuch as these PVL immunization studies by Gladstone et al. did not culminate in the development of an effective anti-S. aureus therapeutic agent, they did provide suitable evidence that an immune response can be mounted against PVL in humans. Interestingly, much of the immunization efforts by Gladstone and colleagues were conducted on patients with already established skin and soft tissue infections (SSTIs) (56). Thus, immunization during such active infections may have had limited value. Likewise, it is difficult to ascertain whether infection resolution was due to the administration of the toxoid or simply to natural clearance over the course of infection. It was also unknown whether or not the subjects of that study were infected with strains of S. aureus that contained the pvl genes. More recent research that calls into question the role of PVL in the pathogenesis of SSTIs further limits the interpretation of toxoid efficacy in the studies by Gladstone et al., as the majority of these patients had SSTIs. Regardless, the work of Gladstone and colleagues was at least suggestive of the potential therapeutic value associated with leucocidin immunization and supported further investigation. Importantly, these studies were conducted at a time when there was little appreciation for the diversity of leucocidins present within a given strain of S. aureus (19?1). Given the redundant and nonredundant activities of individual leucocidins, it is perhaps not surprising that the administration of a toxoid composed strictly of PVL displayed limited efficacy (19?1). Our current appreciation for the redundancies in cytotoxic molecules expressed by S. aureus makes it clear that an effective strategy to promote enhanced resolution of infection by the immune system is going to require the targeting of more than one toxic molecule (19). In particular, the diverse repertoire of immune evasion molecules produced by S. aureus will certainly necessitate the consideration of multicomponent therapeutics and vaccines (22, 23). In the past 10 years, our increased knowledge of leucocidin diversity, directed targeting of host immune cells, and their unique cellular specificities has left researchers better poised to test whether the development of novel therapeutic agents targeting multiple S. aureus leucocidins will prove to be an efficacious treatment strategy. In the last 50 years, few studies have sought to directly evaluate the therapeutic potential of antileucocidin-based treatment modalities. One study, which immunized rabbits with PVL in order to prevent the pathological outcomes of mastitis, showed no effi-cacy (325). In contrast, another study suggested that the administration of intravenous immunoglobulin (IVIG) might have potential therapeutic value, as it is likely to contain a number of antitoxin antibodies. Gauduchon et al. demonstrated that IVIG is capable of neutralizing the toxic activity of PVL in vitro and suggested that its use in conjunction with antibiotics may improve outcomes in patients with invasive S. aureus infection (326). However, IVIG is currently not recommended as a routine course of therapy, even for invasive S. aureus infection, despite its ability to neutralize PVL quite efficiently (4). This is due in part to conflicting evidence surrounding whether or not inhibition of PVL by IVIG is beneficial du.
