Opsonic antibodies to the surface M protein of group A streptococci in pooled normal immunoglobulins (IVIG): potential impact on the clinical efficacy of IVIG therapy for severe invasive group A streptococcal infections

In vitro evaluation of human intravenous immunoglobulin in combination with antimicrobials and human serum against multidrug-resistant isolates of Acinetobacter baumannii

The high incidence of multidrug-resistant (MDR) Acinetobacter baumannii has been a challenge for health worldwide, due to the reduction of therapeutic options, making the use of antimicrobial combinations necessary for the treatment, such as meropenem, amikacin, and colistin. Antibodies against bacterial species, mainly immunoglobulins G (IgG), are produced for acting as effector mechanisms (neutralization, opsonization, phagocytosis, and complement system activation). Some studies have demonstrated promising results of IgG in combination with antimicrobial preparations against bacterial infections, in which the direct action of IgG has restored the immune system balance. Serious problem caused by the increase of MDR A. baumannii isolates results in a constant search for therapeutic alternatives to defeat these infections. However, this study aims to verify in vitro the phagocytosis rate of the A. baumannii-infected human monocytes, as well as to analyze possible morphological changes induced by intravenous immunoglobulin G (IVIG) with human serum in association with antimicrobials. The phagocytosis rate and bacterial cell binding capacity of IVIG were determined for two A. baumannii isolates submitted to 4 mg/mL of human IVIG alone and in combination with different sub-minimum inhibitory concentrations (sub-MICs) of meropenem, amikacin, and colistin and processed for indirect immunofluorescence. Subsequently, these isolates were resubmitted and coupled with human serum and processed for scanning electron microscopy. There was no statistical difference for phagocytosis rates in the isolates tested. Bacterial isolates showed alterations in cell morphology when exposed to IVIG/human serum alone and in combination with antimicrobials such as alteration in shape, wrinkling, membrane depression, and especially cell rupture with extravasation of cytoplasmic material. The isolates visually differed in the IVIG binding to the bacterial cell, with higher fluorescence intensity, which corresponds to the highest IVIG binding, in the isolate more sensitive to meropenem, amikacin, and colistin. No differences between treatments were observed in the IVIG binding to the bacterial cell. The combined action of IVIG with meropenem, amikacin, and colistin against A. baumannii MDR isolates induced several bacterial cell damages. And when associated with human serum, a massive destruction of cells can be observed. These results may suggest the analysis of the use of IgG preparations for the treatment of A. baumannii MDR infections.

Correlates of immunity to Group A Streptococcus: a pathway to vaccine development

Understanding immunity in humans to Group A Streptococcus (Strep A) is critical for the development of successful vaccines to prevent the morbidity and mortality attributed to Strep A infections. Despite decades of effort, no licensed vaccine against Strep A exists and immune correlates of protection are lacking; a major impediment to vaccine development. In the absence of a vaccine, we can take cues from the development of natural immunity to Strep A in humans to identify immune correlates of protection. The age stratification of incidence of acute Strep A infections, peaking in young children and waning in early adulthood, coincides with the development of specific immune responses. Therefore, understanding the immune mechanisms involved in natural protection from acute Strep A infection is critical to identifying immune correlates to inform vaccine development. This perspective summarises the findings from natural infection studies, existing assays of immunity to Strep A, and highlights the gaps in knowledge to guide the development of Strep A vaccines and associated correlates of protection.

Immunotherapy targeting the Streptococcus pyogenes M protein or streptolysin O to treat or prevent influenza A superinfection

Viral infections complicated by a bacterial infection are typically referred to as coinfections or superinfections. Streptococcus pyogenes, the group A streptococcus (GAS), is not the most common bacteria associated with influenza A virus (IAV) superinfections but did cause significant mortality during the 2009 influenza pandemic even though all isolates are susceptible to penicillin. One approach to improve the outcome of these infections is to use passive immunization targeting GAS. To test this idea, we assessed the efficacy of passive immunotherapy using antisera against either the streptococcal M protein or streptolysin O (SLO) in a murine model of IAV-GAS superinfection. Prophylactic treatment of mice with antiserum to either SLO or the M protein decreased morbidity compared to mice treated with non-immune sera; however, neither significantly decreased mortality. Therapeutic use of antisera to SLO decreased morbidity compared to mice treated with non-immune sera but neither antisera significantly reduced mortality. Overall, the results suggest that further development of antibodies targeting the M protein or SLO may be a useful adjunct in the treatment of invasive GAS diseases, including IAV-GAS superinfections, which may be particularly important during influenza pandemics.

Correlation Between Immunoglobulin Dose Administered and Plasma Neutralization of Streptococcal Superantigens in Patients With Necrotizing Soft Tissue Infections

Analyses of plasma collected pre- and postadministration of intravenous immunoglobulin (IVIG) from patients with group A Streptococcus necrotizing soft tissue infections demonstrated a negative correlation between IVIG dose and toxin-triggered T-cell proliferation (r = −.67, P < .0001). One 25-g IVIG dose was sufficient to yield plasma-neutralizing activity against streptococcal superantigens.

Clinical Trials Registration. NCT 01790698 and NCT02111161.

Identification of the Streptococcus pyogenes surface antigens recognised by pooled human immunoglobulin

Immunity to common bacteria requires the generation of antibodies that promote opsonophagocytosis and neutralise toxins. Pooled human immunoglobulin is widely advocated as an adjunctive treatment for clinical Streptococcus pyogenes infection however, the protein targets of the reagent remain ill defined. Affinity purification of the anti-streptococcal antibodies present within pooled immunoglobulin resulted in the generation of an IgG preparation that promoted opsonophagocytic killing of S. pyogenes in vitro and provided passive immunity in vivo. Isolation of the streptococcal surface proteins recognised by pooled human immunoglobulin permitted identification and ranking of 94 protein antigens, ten of which were reproducibly identified across four contemporary invasive S. pyogenes serotypes (M1, M3, M12 and M89). The data provide novel insight into the action of pooled human immunoglobulin during invasive S. pyogenes infection, and demonstrate a potential route to enhance the efficacy of antibody based therapies.

Group a streptococcal vaccine candidates: potential for the development of a human vaccine

Currently there is no commercial Group A Streptococcus (GAS; S. pyogenes) vaccine available. The development of safe GAS vaccines is challenging, researchers are confronted with obstacles such as the occurrence of many unique serotypes (there are greater than 150 M types), antigenic variation within the same serotype, large variations in the geographical distribution of serotypes, and the production of antibodies cross-reactive with human tissue which can lead to host auto-immune disease. Cell wall anchored, cell membrane associated, secreted and anchorless proteins have all been targeted as GAS vaccine candidates. As GAS is an exclusively human pathogen, the quest for an efficacious vaccine is further complicated by the lack of an animal model which mimics human disease and can be consistently and reproducibly colonized by multiple GAS strains.

Intravenous immunoglobulin in children with streptococcal toxic shock syndrome

BACKGROUND

Streptococcal toxic shock syndrome (TSS) is a rare and severe manifestation of group A streptococcal infection. The role of intravenous immunoglobulin (IVIG) for streptococcal TSS in children is controversial. This study aims to describe the epidemiology of streptococcal TSS in children and to determine whether adjunctive therapy with IVIG is associated with improved outcomes.

METHODS

A multicenter, retrospective cohort study of children with streptococcal TSS from 1 January 2003 through 31 December 2007 was conducted. Propensity scores were used to determine each child's likelihood of receiving IVIG. Differences in the primary outcomes of death, hospital length of stay, and total hospital costs were compared after matching IVIG recipients and nonrecipients on propensity score.

RESULTS

The median patient age was 8.2 years. IVIG was administered to 84 (44%) of 192 patients. The overall mortality rate was 4.2% (95% confidence interval, 1.8%-8.0%). Differences in mortality between IVIG recipients (n = 3; 4.5%) and nonrecipients (n = 3; 4.5%) were not statistically significant (p > .99). Although patients receiving IVIG had higher total hospital and drug costs than nonrecipients, differences in hospital costs were not significant once drug costs were removed (median difference between matched patients, $6139; interquartile range, -$8316 to $25,993; P = .06). No differences were found in length of hospital stay between matched IVIG recipients and nonrecipients.

CONCLUSION

This multicenter study is, to our knowledge, the largest to describe the epidemiology and outcomes of children with streptococcal TSS and the first to explore the association between IVIG use and clinical outcomes. IVIG use was associated with increased costs of caring for children with streptococcal TSS but was not associated with improved outcomes.

Hyperimmune products in the prevention and therapy of infectious disease: a report of a hyperimmune products expert advisory panel

This paper reviews a meeting at which basic pathophysiology of infections, mechanisms of action of hyperimmune products and pharmacokinetic and pharmacodynamic parameters, as well as currently available hyperimmunes and their potential new targets and uses, were discussed. A hyperimmune product was defined as either a monoclonal antibody or a polyclonal preparation enriched with antibody directed against one or more particular targets. A number of issues were emphasised, including: resistant bacterial pathogens, such as Staphylococcus aureus and Streptococcus pyogenes; the role of hyperimmune intravenous globulins in the prevention of sepsis in low birthweight infants; hepatitis B virus infection associated with liver transplantation; combination therapy; the potential role of hyperimmunes in the prevention and treatment of hepatitis C virus; and the use of immunoglobulins for the prophylaxis of Epstein-Barr virus-related lymphoproliferative disease. Routes of administration were also discussed. It was concluded that the development of hyperimmunes faces numerous obstacles. It was agreed that the use of hyperimmunes in clinical trials must be standardised; clinical trials must be large enough to have sufficient power to demonstrate efficacy with clear-cut end-points, and means need to be developed, in conjunction with regulatory agencies, for the feasible evaluation of combination products. However, progress in all these aspects will provide a wide range of hyperimmunes for future use.

A survey of physician's attitudes regarding management of severe group A streptococcal infections

Intravenous immunoglobulins (IVIG) use in the management of streptococcal toxic shock syndrome remains highly controversial. To evaluate the current management of severe group A streptococcal infections and the feasibility of a randomized controlled trial comparing immunoglobulins versus placebo for streptococcal toxic shock syndrome and/or necrotizing fasciitis, a 32-question mail and web-based survey of Canadian infectious disease specialists was conducted between December 2003 and February 2004. Overall, 172 respondents (90.5%) recommended immunoglobulins as adjunctive treatment of streptococcal toxic shock compared to 67 (35.3%) for fasciitis without toxic shock and 93 (48.9%) for invasive group A streptococcal infections with hypotension. A considerable proportion of respondents agreed that a randomized clinical trial in streptococcal toxic shock (70.1%, 131/187) and necrotizing fasciitis without toxic shock (88.2%, 162/186) would be ethical. From these, a great majority would be willing to enroll patients in a trial comparing IVIG to placebo for streptococcal toxic shock (125/131, 95.4%) and necrotizing fasciitis without shock (152/162, 93.8%). These initial results clearly demonstrate ambivalence in the utilization of intravenous immunoglobulins (IVIG) in invasive group A streptococcal infections in Canada and emphasize the need for further clinical data on immunoglobulin use in streptococcal toxic shock syndrome. They also demonstrate that, although the majority of physicians recommend immunoglobulins, there is important variability between physician recommendations with regard to the indications of use, dose, and time of administration.

Antibodies against a surface protein of Streptococcus pyogenes promote a pathological inflammatory response

Streptococcal toxic shock syndrome (STSS) caused by Streptococcus pyogenes is a clinical condition with a high mortality rate despite modern intensive care. A key feature of STSS is excessive plasma leakage leading to hypovolemic hypotension, disturbed microcirculation and multiorgan failure. Previous work has identified a virulence mechanism in STSS where M1 protein of S. pyogenes forms complexes with fibrinogen that activate neutrophils to release heparin-binding protein (HBP), an inducer of vascular leakage. Here, we report a marked inter-individual difference in the response to M1 protein-induced HBP release, a difference found to be related to IgG antibodies directed against the central region of the M1 protein. To elicit massive HBP release, such antibodies need to be part of the M1 protein-fibrinogen complexes. The data add a novel aspect to bacterial pathogenesis where antibodies contribute to the severity of disease by promoting a pathologic inflammatory response.

Soluble M1 protein of Streptococcus pyogenes triggers potent T cell activation

Streptococcus pyogenes of the M1 serotype is commonly associated with large outbreaks of invasive streptococcal infections and development of streptococcal toxic shock syndrome (STSS). The pathogenesis behind these infections is believed to involve bacterial superantigens that induce potent inflammatory responses, but the reason why strains of the M1 serotype are over-represented in STSS is still not understood. In the present investigation, we show that a highly purified soluble form of the M1 protein from S. pyogenes, which lacks the membrane-spanning region, is a potent inducer of T cell proliferation and release of Th1 type cytokines. M1 protein-evoked T cell proliferation was HLA class II-dependent but not MHC-restricted, did not require intracellular processing and was Vbeta-restricted. Extensive mass spectrometry studies indicated that there were no other detectable proteins in the preparation. Taken together, our data demonstrate that soluble M1 protein is a novel streptococcal superantigen, which likely contributes to the excessive T cell activation and hyperinflammatory response seen in severe invasive streptococcal infections.

The epidemiology of invasive group A streptococcal disease in Victoria, Australia

OBJECTIVE

To estimate the incidence and severity of invasive group A streptococcal infection in Victoria, Australia.

DESIGN

Prospective active surveillance study.

SETTING

Public and private laboratories, hospitals and general practitioners throughout Victoria.

PATIENTS

People in Victoria diagnosed with group A streptococcal disease notified to the surveillance system between 1 March 2002 and 31 August 2004.

MAIN OUTCOME MEASURE

Confirmed invasive group A streptococcal disease.

RESULTS

We identified 333 confirmed cases: an average annual incidence rate of 2.7 (95% CI, 2.3-3.2) per 100,000 population per year. Rates were highest in people aged 65 years and older and those younger than 5 years. The case-fatality rate was 7.8%. Streptococcal toxic shock syndrome occurred in 48 patients (14.4%), with a case-fatality rate of 23%. Thirty cases of necrotising fasciitis were reported; five (17%) of these patients died. Type 1 (23%) was the most frequently identified emm sequence type in all age groups. All tested isolates were susceptible to penicillin and clindamycin. Two isolates (4%) were resistant to erythromycin.

CONCLUSION

The incidence of invasive group A streptococcal disease in temperate Australia is greater than previously appreciated and warrants greater public health attention, including its designation as a notifiable disease.

Differences in Potency of Intravenous Polyspecific Immunoglobulin G against Streptococcal and Staphylococcal Superantigens: Implications for Therapy of Toxic Shock Syndrome

Administration of intravenous polyspecific immunoglobulin G (IVIG) has been proposed as adjunctive therapy for toxic shock syndrome caused by Streptococcus pyogenes or Staphylococcus aureus. We investigated whether superantigen-containing culture supernatants prepared from streptococcal isolates (n=21) and staphylococcal isolates (n=20) from cases of severe sepsis were inhibited to an equal extent by IVIG in proliferation experiments that used human peripheral blood mononuclear cells. All 3 IVIG preparations tested were highly efficient in neutralizing the superantigens, and most supernatants were completely inhibited at concentrations ranging from 0.05 to 2.5 mg IVIG/mL. An important finding was that culture supernatants from S. pyogenes isolates were consistently inhibited to a greater extent than those of S. aureus isolates (P<.01). The findings demonstrate that staphylococcal superantigens are not inhibited as efficiently as streptococcal superantigens by IVIG, and, hence, a higher dose of IVIG may be required for therapy of staphylococcal toxic shock syndrome in order to achieve protective titers and clinical efficacy.

Intravenous immunoglobulin adjunctive therapy in sepsis, with special emphasis on severe invasive group A streptococcal infections

Immunotherapy targeted against microbial toxins and host mediators has been studied in many preclinical investigations and clinical trials of sepsis during the past 20 y. Intravenous immunoglobulin, including both monoclonal and polyclonal antibodies, represents one such immunotherapeutic strategy. Mononclonal antibodies directed against endotoxin or tumour necrosis factor-alpha have been tested extensively in clinical trials, but have so far failed to reveal a significant effect on mortality rates. Several studies have assessed the efficacy of polyclonal intravenous immunoglobulin (IVIG) in sepsis, with varying results. Although there are no conclusive data available to date to support the use of IVIG therapy in all sepsis cases, there are strong indications that certain defined septic subgroups, such as streptococcal toxic shock syndrome caused by group A streptococcus, will benefit from its use. This review briefly summarizes the clinical trials on IVIG therapy in sepsis, and describes in more detail the mechanistic actions of IVIG and the clinical data that support the use of IVIG as adjunctive therapy in severe invasive group A streptococcal infections.

Intravenous immunoglobulin G therapy in streptococcal toxic shock syndrome: a European randomized, double-blind, placebo-controlled trial

The efficacy and safety of high-dose intravenous polyspecific immunoglobulin G (IVIG) as adjunctive therapy in streptococcal toxic shock syndrome (STSS) were evaluated in a multicenter, randomized, double-blind, placebo-controlled trial. The trial was prematurely terminated because of slow patient recruitment, and results were obtained from 21 enrolled patients (10 IVIG recipients and 11 placebo recipients). The primary end point was mortality at 28 days, and a 3.6-fold higher mortality rate was found in the placebo group. A significant decrease in the sepsis-related organ failure assessment score at days 2 (P=.02) and 3 (P=.04) was noted in the IVIG group. Furthermore, a significant increase in plasma neutralizing activity against superantigens expressed by autologous isolates was noted in the IVIG group after treatment (P=.03). Although statistical significance was not reached in the primary end point, the trial provides further support for IVIG as an efficacious adjunctive therapy in STSS.

The Treatment of Severe Group A Streptococcal Infections

Group A streptococci can cause a variety of diseases ranging from uncomplicated superficial infections to severe systemic infections associated with high morbidity and mortality. Since the late 1980s a drastic resurgence of highly aggressive invasive streptococcal infections, including streptococcal toxic shock syndrome and necrotizing fasciitis, have been noted worldwide. This has prompted intense research in the field and important new information has been gained regarding the pathogenesis and treatment of life-threatening invasive group A streptococcal infections. Exotoxins with superantigenic activities have been identified as central mediators of the systemic effects seen in streptococcal toxic shock syndrome. Novel therapeutic strategies include agents that can inhibit these superantigens, and one promising candidate is intravenous polyspecific immunoglobulin that contains neutralizing antibodies against a wide spectrum of streptococcal superantigens. Intravenous immunoglobulin adjunctive therapy was shown in a case-control study to reduce mortality in patients with streptococcal toxic shock syndrome.

Back to the future: antibody-based strategies for the treatment of infectious diseases

Before antibiotics, sera from immune animals and humans were used to treat a variety of infectious diseases, often with successful results. After the discovery of antimicrobial agents, serum therapy for bacterial infections was rapidly forsaken. In the last two decades, problems with treatment of newly emerged, re-emerged, or persistent infectious diseases necessitated researchers to develop new and/or improved antibody-based therapeutic approaches. This article reviews some information on the use of antibodies for the treatment of infectious diseases, with special reference to the most seminal discoveries and current advances as well as available treatment approaches in this field.

A direct comparison of the antigen-specific antibody profiles of intravenous immunoglobulins derived from US and UK donor plasma

BACKGROUND AND OBJECTIVES

Intravenous immunoglobulin (IVIG) is used in a range of immunodeficiency states that require a broad spectrum of protective antibodies to a range of common pathogens. A comparison of the antigen-specific antibody profile of preparations of an IVIG (Vigam) derived from US and UK sourced plasma was performed, and these preparations were also compared with three other IVIG products from different manufacturers.

MATERIALS AND METHODS

Antibodies against a range of bacterial and viral pathogens were measured by immunoassay.

RESULTS

Similar profiles were found for Vigam made from UK and US source plasma and also for the other three IVIGs tested, but some specific differences were observed.

CONCLUSIONS

IVIG preparations have a similar therapeutic spectrum of antibodies when prepared from plasma sourced either from the UK or the US.

Toxic shock syndrome and bacterial superantigens: an update

Toxic shock syndrome (TSS) is an acute onset illness characterized by fever, rash formation, and hypotension that can lead to multiple organ failure and lethal shock, as well as desquamation in patients that recover. The disease is caused by bacterial superantigens (SAGs) secreted from Staphylococcus aureus and group A streptococci. SAGs bypass normal antigen presentation by binding to class II major histocompatibility complex molecules on antigen-presenting cells and to specific variable regions on the beta-chain of the T-cell antigen receptor. Through this interaction, SAGs activate T cells at orders of magnitude above antigen-specific activation, resulting in massive cytokine release that is believed to be responsible for the most severe features of TSS. This review focuses on clinical and epidemiological aspects of TSS, as well as important developments in the genetics, biochemistry, immunology, and structural biology of SAGs. From the evolutionary relationships between these important toxins, we propose that there are five distinct groups of SAGs.

Immunochemical-based assays in the bioanalysis of immunoglobulins

Intravenous immunoglobulin (IVIG) preparations consist of IgG derived from a pool of human plasma of healthy individuals and have been used as routine treatment of patients with primary and secondary immunodeficiencies, autoimmune, and/or inflammatory diseases. Emergence of new infectious agents and development of antibiotic resistance in many bacteria have posed serious problems in the treatment of infections. Since IVIGs contain natural antibodies that occur in the healthy population, their administration to immunocompromised hosts either as a prophylactic agent or as complementary treatment to the usual antimicrobial treatment have been studied. Contradictory results obtained by several clinical studies in respect to the clinical efficacy of IVIGs have in part been ascribed to the poor characterization of IVIG preparations in terms of their specific antibody content against the various pathogenic microorganisms. Immunoassays constitute a promising tool for bioanalysis of IVIGs thanks to the high sensitivity, repeatability and ease of implementation. Ensuring high selectivity, enzyme immunoassays have been used for determination of the levels of pathogen-specific antibodies in IVIG preparations. In this review, the application of immunoassays monitoring such specific antibodies in IVIGs and the relationship of estimated titers with their in vitro opsonic activity are summarized. The relationship of the content of specific antibodies in IVIGs and their functional efficacy with the outcome of clinical studies including patients with primary immunodeficiencies and premature neonates treated with IVIGs is also discussed.

Relative neutralizing activity in polyspecific IgM, IgA, and IgG preparations against group A streptococcal superantigens

In this study we compared the ability of different immunoglobulin (Ig) preparations containing IgG, IgM, and/or IgA to neutralize the activity of streptococcal pyrogenic exotoxin A (SpeA) or culture supernatant from a clinical group A streptococcal isolate. All Ig preparations markedly inhibited the mitogenic and cytokine-inducing activity of SpeA and culture supernatant at concentrations of 0.05-0.5 mg/mL, and at 0.5 mg/mL, most caused 95-100% inhibition of both stimuli. A significantly higher (P< or =.05) inhibition of SpeA was achieved by Pentaglobin (IgG, IgM, and IgA) and IgAbulin (IgA and IgG), as compared with pure IgG preparations. IgM- and IgA-enriched preparations had significantly higher inhibitory activity against SpeA than against culture supernatant, whereas the reverse was true for the IgG preparations (P< or =.05). The data show that IgM and IgA are potent inhibitors of specific streptococcal superantigens. These findings may have implications for the optimization of immunotherapy in invasive streptococcal infections.

Pathogenesis of group A streptococcal infections

Group A streptococci are model extracellular gram-positive pathogens responsible for pharyngitis, impetigo, rheumatic fever, and acute glomerulonephritis. A resurgence of invasive streptococcal diseases and rheumatic fever has appeared in outbreaks over the past 10 years, with a predominant M1 serotype as well as others identified with the outbreaks. emm (M protein) gene sequencing has changed serotyping, and new virulence genes and new virulence regulatory networks have been defined. The emm gene superfamily has expanded to include antiphagocytic molecules and immunoglobulin-binding proteins with common structural features. At least nine superantigens have been characterized, all of which may contribute to toxic streptococcal syndrome. An emerging theme is the dichotomy between skin and throat strains in their epidemiology and genetic makeup. Eleven adhesins have been reported, and surface plasmin-binding proteins have been defined. The strong resistance of the group A streptococcus to phagocytosis is related to factor H and fibrinogen binding by M protein and to disarming complement component C5a by the C5a peptidase. Molecular mimicry appears to play a role in autoimmune mechanisms involved in rheumatic fever, while nephritis strain-associated proteins may lead to immune-mediated acute glomerulonephritis. Vaccine strategies have focused on recombinant M protein and C5a peptidase vaccines, and mucosal vaccine delivery systems are under investigation.

An enzyme immunoassay to determine the levels of specific antibodies toward bacterial surface antigens in human immunoglobulin preparations and blood serum

Human polyvalent intravenous immunoglobulin (IVIG) preparations are used as a complementary aid to the proper antimicrobial treatment of severely septic patients in intensive care units (ICUs) and/or as a prophylactic agent to immunocompromised hosts, particularly prone to bacterial infections. There is skepticism about the usefulness of IVIGs since it is not known whether their administration ensures the enhancement of humoral immune responses by providing a sufficient amount of specific antibodies towards the specified bacterial pathogen to be treated. In this report, a simple and reproducible enzyme-linked immunosorbent assay for determining the content of specific antibodies against bacterial surface antigens in commercially available IVIG preparations is described. The method is also easily applied to determine the amount of bacterial antibodies in blood serum. The levels of specific antibodies toward gram positive and negative pathogenic isolates often encountered in ICUs were estimated in two IVIG (Sandoglobulin and Gamimmune) preparations. Significant differences regarding the content of antibodies to certain clinically bacterial isolates were identified not only between the two IVIG preparations tested, but also among various lots from each IVIG preparation. No significant variation (P < or = 0.001) among the bottles derived from the same lot was determined in both preparations. The variation in the levels of specific antibodies in IVIG preparations may be attributed to differences between the donor pools as well as the manufacturing procedure. Application of the method to patients with primary immune deficiencies showed that infusion of highly reactive IVIG preparations enhanced significantly their humoral response toward various pathogens. The results of this study suggest that the content determination of pathogen-specific antibodies in IVIG preparations before administration may be of great importance for treating bacterial infections.

Risk factors in the pathogenesis of invasive group A streptococcal infections: role of protective humoral immunity

An impressive change in the epidemiology and severity of invasive group A streptococcal infections occurred in the 1980s, and the incidence of streptococcal toxic shock syndrome cases continues to rise. The reason for the resurgence of severe invasive cases remains a mystery-has there been a change in the pathogen or in host protective immunity? To address these questions, we have studied 33 patients with invasive infection caused by genotypically indistinguishable M1T1 strains of Streptococcus pyogenes who had different disease outcomes. Patients were classified as having severe (n = 21) and nonsevere (n = 12) invasive infections based on the presence or absence of shock and organ failure. Levels of anti-M1 bactericidal antibodies and of anti-streptococcal superantigen neutralizing antibodies in plasma were significantly lower in both groups than in age- and geographically matched healthy controls (P < 0.01). Importantly, the levels of these protective antibodies in plasma samples from severe and nonsevere invasive cases were not different. Together the data suggest that low levels of protective antibodies may contribute to host susceptibility to invasive streptococcal infection but do not modulate disease outcome. Other immunogenetic factors that regulate superantigen responses may influence the severity of systemic manifestations associated with invasive streptococcal infection.