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

Clinical efficacy of IgM-enriched immunoglobulin as adjunctive therapy in neonatal and pediatric sepsis: a systematic review and meta-analysis

Background

Sepsis is a major cause of mortality and morbidity globally, with around one-quarter of all sepsis-related deaths occurring in children under the age of 5. We conducted a meta-analysis and systematic review of the literature to evaluate the clinical effectiveness of an IgM-enriched immunoglobulin preparation in pediatrics patients and neonates with sepsis.

Methods

Systematic searches of PubMed, the Cochrane Library and Embase databases were performed in November 2022, with no date limitations, to identify studies in which IgM-enriched immunoglobulin was used as adjunctive therapy in neonatal and pediatric patients with sepsis.

Results

In total, 15 studies fulfilled the eligibility criteria, 13 neonatal studies and 2 pediatric studies. Pooled estimates from all studies indicated that mortality rates were significantly lower in patients who received treatment with the IgM-enriched immunoglobulin compared with controls (OR 0.41; 95% CI 0.32-0.55). Further analyses in neonatal studies, alone, showed a significant benefit with longer treatment durations (>3 days) vs. the recommended treatment duration (3 days) (OR 0.32; 95% CI 0.22-0.47) vs. (OR 0.61; 95% CI 0.41-0.92). Treatment with IgM-enriched immunoglobulin was associated with a lower mortality risk compared with controls in prospective studies vs. retrospective analyses (OR 0.37; 95% CI 0.27-0.51) vs. (OR 0.73; 95% CI 0.41-1.30).

Conclusions

This systematic review suggests that adjunctive treatment with IgM-enriched immunoglobulin may reduce the risk of mortality in neonatal and pediatric populations. However, large randomized controlled trials are required to further substantiate and evaluate these findings.

Chlamydia trachomatis-An Emerging Old Entity?

Chlamydia trachomatis is an evasive pathogen that can prompt severe clinical manifestations in humans such as vaginitis, epididymitis, lymphogranuloma venereum, trachoma, conjunctivitis and pneumonia. If left untreated, chronic infections with C. trachomatis can give rise to long-lasting and even permanent sequelae. To shed some light on its widespread nature, data from original research, systematic reviews and meta-analyses from three databases was collected and analyzed in the context of chlamydial infection, related symptoms and appropriate treatment modalities. This review describes the bacterium's pervasiveness on a global scale, especially in developing countries, and suggests ways to halt its transmission and spread. Infections with C. trachomatis often go unnoticed, as many individuals are asymptomatic and unaware of their diagnosis, contributing to a delay in diagnosis and treatment. The high prevalence of chlamydial infection highlights the need for a universal screening and detection method enabling immediate treatment at its onset. Prognosis is favorable with antibiotic therapy and education for high-risk groups and their sexual partners. In the future, a quick, easily accessible, and inexpensive test should be developed to diagnose and treat infected individuals early on. Along with a vaccine against C. trachomatis, it would halt the transmission and spread of the pathogen worldwide.

A new hope? Possibilities of therapeutic IgA antibodies in the treatment of inflammatory lung diseases

Inflammatory lung diseases represent a persistent burden for patients and the global healthcare system. The combination of high morbidity, (partially) high mortality and limited innovations in the last decades, have resulted in a great demand for new therapeutics. Are therapeutic IgA antibodies possibly a new hope in the treatment of inflammatory lung diseases? Current research increasingly unravels the elementary functions of IgA as protector against infections and as modulator of overwhelming inflammation. With a focus on IgA, this review describes the pathological alterations in mucosal immunity and how they contribute to chronic inflammation in the most common inflammatory lung diseases. The current knowledge of IgA functions in the circulation, and particularly in the respiratory mucosa, are summarized. The interplay between neutrophils and IgA seems to be key in control of inflammation. In addition, the hurdles and benefits of therapeutic IgA antibodies, as well as the currently known clinically used IgA preparations are described. The data highlighted here, together with upcoming research strategies aiming at circumventing the current pitfalls in IgA research may pave the way for this promising antibody class in the application of inflammatory lung diseases.

Polyvalent human immunoglobulin for infectious diseases: Potential to circumvent antimicrobial resistance

Antimicrobial resistance (AMR) is a global health problem that causes more than 1.27 million deaths annually; therefore, it is urgent to focus efforts on solving or reducing this problem. The major causes of AMR are the misuse of antibiotics and antimicrobials in agriculture, veterinary medicine, and human medicine, which favors the selection of drug-resistant microbes. One of the strategies proposed to overcome the problem of AMR is to use polyvalent human immunoglobulin or IVIG. The main advantage of this classic form of passive immunization is its capacity to enhance natural immunity mechanisms to eliminate bacteria, viruses, or fungi safely and physiologically. Experimental data suggest that, for some infections, local administration of IVIG may produce better results with a lower dose than intravenous application. This review presents evidence supporting the use of polyvalent human immunoglobulin in AMR, and the potential and challenges associated with its proposed usage.

The Functional Role of IgA in the IgM/IgA-Enriched Immunoglobulin Preparation Trimodulin

In comparison to human immunoglobulin (Ig) G, antibodies of IgA class are not well investigated. In line with this, the functional role of the IgA component in IgM/IgA-enriched immunoglobulin preparations is also largely unknown. In recent years, powerful anti-pathogenic and immunomodulatory properties of human serum IgA especially on neutrophil function were unraveled. Therefore, the aim of our work is to investigate functional aspects of the trimodulin IgA component, a new plasma-derived polyvalent immunoglobulin preparation containing ~56% IgG, ~23% IgM and ~21% IgA. The functional role of IgA was investigated by analyzing the interaction of IgA with FcαRI, comparing trimodulin with standard intravenous IgG (IVIG) preparation and investigating Fc receptor (FcR)-dependent functions by excluding IgM-mediated effects. Trimodulin demonstrated potent immunomodulatory, as well as anti-pathogenic effects in our neutrophil model (neutrophil-like HL-60 cells). The IgA component of trimodulin was shown to induce a strong FcαRI-dependent inhibitory immunoreceptor tyrosine-based activation motif (ITAMi) signaling, counteract lipopolysaccharide-induced inflammation and mediate phagocytosis of Staphylococcus aureus. The fine-tuned balance between immunomodulatory and anti-pathogenic effects of trimodulin were shown to be dose-dependent. Summarized, our data demonstrate the functional role of IgA in trimodulin, highlighting the importance of this immunoglobulin class in immunoglobulin therapy.

Higher levels of IgA and IgG at sepsis onset are associated with higher mortality: results from the Albumin Italian Outcome Sepsis (ALBIOS) trial

Background

The role of intravenous immunoglobulins (IVIG) during sepsis is controversial, as different trials on IVIG have observed inconsistent survival benefits. We aimed to elucidate the possible association and clinical significance between circulating levels of immunoglobulins.

Methods

In a subset of 956 patients with severe sepsis and septic shock of the multicentre, open-label RCT ALBIOS, venous blood samples were serially collected 1, 2, and 7 days after enrolment (or at ICU discharge, whichever came first). IgA, IgG and IgM concentrations were assayed in all patients on day 1 and in a subgroup of 150 patients on days 2 and 7. Ig concentrations were measured employing a turbidimetric assay, OSR61171 system.

Results

IgA on day 1 had a significant predictive value for both 28-day and 90-day mortality (28-day mortality, HR: 1.50 (95% CI 1.18–1.92); 90-day mortality, HR: 1.54 (95% CI 1.25–1.91)). IgG, but not IgM, on day 1 showed similar results for 28-day (HR 1.83 (95% CI 1.33–2.51) and 90-day mortality HR: 1.66 (95% CI 1.23–2.25)). In addition, lower levels of IgG but not of IgA and IgM, at day 1 were associated with significantly higher risk of secondary infections (533 [406–772] vs 600 [452–842] mg/dL, median [Q1–Q3], p = 0.007).

Conclusions

In the largest cohort study of patients with severe sepsis or septic shock, we found that high levels of IgA and IgG on the first day of diagnosis were associated with a decreased 90-day survival. No association was found between IgM levels and survival. As such, the assessment of endogenous immunoglobulins could be a useful tool to identify septic patients at high risk of mortality.

Trial registration #NCT00707122, Clinicaltrial.gov, registered 30 June 2008

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00952-z.

The Role of Streptococcal and Staphylococcal Exotoxins and Proteases in Human Necrotizing Soft Tissue Infections

Necrotizing soft tissue infections (NSTIs) are critical clinical conditions characterized by extensive necrosis of any layer of the soft tissue and systemic toxicity. Group A streptococci (GAS) and Staphylococcus aureus are two major pathogens associated with monomicrobial NSTIs. In the tissue environment, both Gram-positive bacteria secrete a variety of molecules, including pore-forming exotoxins, superantigens, and proteases with cytolytic and immunomodulatory functions. The present review summarizes the current knowledge about streptococcal and staphylococcal toxins in NSTIs with a special focus on their contribution to disease progression, tissue pathology, and immune evasion strategies.

Anti-chlamydia IgG and IgA are insufficient to prevent endometrial chlamydia infection in women, and increased anti-chlamydia IgG is associated with enhanced risk for incident infection

PROBLEM

Chlamydia infections in women can ascend to the upper genital tract, and repeated infections are common, placing women at risk for sequelae. The protective role of anti-chlamydia antibodies to surface exposed antigens in ascending and incident infection is unclear.

METHOD OF STUDY

A whole-bacterial ELISA was used to quantify chlamydia-specific IgG and IgA in serum and cervical secretions of 151 high-risk women followed longitudinally. Correlations were determined between antibody and cervical burden, and causal mediation analysis investigated the effect of antibody on ascension. We examined the relationship of antibody to incident infection using the marginal Cox model.

RESULTS

Serum and cervical anti-chlamydia IgG and cervical IgA levels correlated inversely with cervical burden. While lower burden was associated with reduced ascension, causal mediation analysis revealed that the indirect effects of antibody mediated through reductions in bacterial burden were insufficient to prevent ascension. Analysis of women uninfected at enrollment revealed that serum and cervical anti-chlamydia IgG were associated with increased risk of incident infection; hazard ratio increased 3.6-fold (95% CI, 1.3-10.3), and 22.6-fold (95% CI, 3.1-165.2) with each unit of serum and cervical IgG, respectively.

CONCLUSION

Although anti-chlamydia IgG and IgA correlated with reduced cervical chlamydia burden, they failed to prevent ascension and increased levels of anti-chlamydia IgG were associated with increased risk for incident infection.

IgM and IgA enriched polyclonal immunoglobulins reduce short term mortality in extremely low birth weight infants with sepsis: a retrospective cohort study

BACKGROUND

Immunoglobulin supplementation is a debated strategy in fighting sepsis. We evaluated a polyclonal IgM and IgA enriched immunoglobulin (IgMeIVIG) preparation in reducing the short-term mortality in extremely low birth weight neonates (ELBW) with proven infection.

METHODS

ELBW infants born from January 2008 to December 2014 were eligible for this retrospective case-control analysis if they were symptomatic and had a positive blood culture after 72 hours of life. Patients received antibiotic treatment with or without IgMeIVIG (intravenously, 250 mg/kg/day for 3 days) within the 24 hours from clinical suspicion as per indication of the attending physician. Short-term (7 and 21 days) mortality was the study primary outcome while secondary outcomes were: mortality at discharge, intraventricular hemorrhage, necrotizing enterocolitis, bronchopulmonary dysplasia, periventricular leukomalacia, and retinopathy of prematurity.

RESULTS

Each group was composed by thirty-nine infants. Both groups were similar for antenatal steroids, mode of delivery, birth weight, gestational age and SNAPII score as indicator of disease severity. Infants receiving IgMeIVIG had a significantly lower short-term mortality compared with neonates receiving antibiotics alone: 6/39 (15%) vs. 14/39 (36%); P=0.038. No differences in other outcomes were found.

CONCLUSIONS

This study shows that IgMeIVIG may have a role as adjuvant therapy in ELBW infants with proven sepsis. We warrant future prospective, blinded RCT studies where IgMeIVIG can be consistently used if needed throughout the NICU admission in ELBW septic neonates to appropriately evaluate its effect on mortality at discharge.

Nasopharyngeal infection by Streptococcus pyogenes requires superantigen-responsive Vβ-specific T cells

The globally prominent pathogen Streptococcus pyogenes secretes potent immunomodulatory proteins known as superantigens (SAgs), which engage lateral surfaces of major histocompatibility class II molecules and T-cell receptor (TCR) β-chain variable domains (Vβs). These interactions result in the activation of numerous Vβ-specific T cells, which is the defining activity of a SAg. Although streptococcal SAgs are known virulence factors in scarlet fever and toxic shock syndrome, mechanisms by how SAgs contribute to the life cycle of S. pyogenes remain poorly understood. Herein, we demonstrate that passive immunization against the Vβ8-targeting SAg streptococcal pyrogenic exotoxin A (SpeA), or active immunization with either wild-type or a nonfunctional SpeA mutant, protects mice from nasopharyngeal infection; however, only passive immunization, or vaccination with inactive SpeA, resulted in high-titer SpeA-specific antibodies in vivo. Mice vaccinated with wild-type SpeA rendered Vβ8⁺ T cells poorly responsive, which prevented infection. This phenotype was reproduced with staphylococcal enterotoxin B, a heterologous SAg that also targets Vβ8⁺ T cells, and rendered mice resistant to infection. Furthermore, antibody-mediated depletion of T cells prevented nasopharyngeal infection by S. pyogenes, but not by Streptococcus pneumoniae, a bacterium that does not produce SAgs. Remarkably, these observations suggest that S. pyogenes uses SAgs to manipulate Vβ-specific T cells to establish nasopharyngeal infection.

Serum IgG levels and mortality in patients with severe sepsis and septic shock : The SBITS data

BACKGROUND

The role of intravenous immune globulin (Ig) therapy in patients with severe sepsis and septic shock is discussed controversially. Low initial IgG levels could help to identify those patients who might benefit from an adjunctive Ig treatment.

OBJECTIVES

To investigate the effect of initial serum IgG levels on 28-day mortality in patients with severe sepsis and septic shock.

MATERIALS AND METHODS

In this retrospective analysis of the SBITS trial data, 543 patients were allocated to four groups (quartiles) depending on their initial serum IgG levels (1: IgG ≤ 6.1 g/l; 2: IgG 6.2-8.4 g/l; 3: IgG 8.5-11.9 g/l; 4: IgG > 11.9 g/l). The third quartile was taken as the reference quartile. For the applied logistic regression model clinically relevant confounders were defined and integrated into further risk-adjusted calculations.

RESULTS

Patients with the lowest IgG levels had a mortality rate similar to those patients with initial IgG levels in the second and third quartile, representing the physiological IgG range in healthy people. Surprisingly, patients with the highest IgG levels even showed a significantly higher mortality in a risk-adjusted calculation compared to the reference quartile (OR 1.69, CI 1.01-2.81, p = 0.05). Subgroup analyses revealed that initial IgG levels were of no prognostic value in patients presenting with vasopressor-dependent septic shock on admission as well as in patients with either gram-positive or gram-negative sepsis.

CONCLUSIONS

Initially low IgG levels do not discriminate between survival and nonsurvival in patients with severe sepsis and septic shock. Therefore, low IgG cannot help to identify those patients who might benefit from an adjunctive IgG sepsis therapy. Whether a high initial IgG serum level is an independent mortality risk factor needs to be investigated prospectively.

Immunoglobulins in neonatal sepsis: has the final word been said?

Systemic infection is a major cause of mortality and morbidity among premature neonates. In this fragile population, the immaturity of the innate immune response relates inversely to gestational age and is one of the determinants of susceptibility to infections. Antibiotic therapy, even when appropriately and timely instituted, may fail to prevent death or significant sequelae. The quest for additional strategies is still open; in this scenario, the supplementation with exogenous immunoglobulins represents an attractive additional strategy of defence. As current data are conflicting, we provide a critical appraisal with a focus on IgM enriched immunoglobulins preparations.

Reconstituted human polyclonal plasma-derived secretory-like IgM and IgA maintain the barrier function of epithelial cells infected with an enteropathogen

Intravenous administration of polyclonal and monoclonal antibodies has proven to be a clinically valid approach in the treatment, or at least relief, of many acute and chronic pathologies, such as infection, immunodeficiency, and a broad range of autoimmune conditions. Plasma-derived IgG or recombinant IgG are most frequently used for intravenous or subcutaneous administration, whereas a few IgM-based products are available as well. We have established recently that secretory-like IgA and IgM can be produced upon association of plasma-derived polymeric IgA and IgM with a recombinant secretory component. As a next step toward potential future mucosal administration, we sought to unravel the mechanisms by which these secretory Igs protect epithelial cells located at the interface between the environment and the inside of the body. By using polarized epithelial Caco-2 cell monolayers and Shigella flexneri as a model enteropathogen, we found that polyspecific plasma-derived SIgA and SIgM fulfill many protective functions, including dose-dependent recognition of the antigen via formation of aggregated immune complexes, reduction of bacterial infectivity, maintenance of epithelial cell integrity, and inhibition of proinflammatory cytokine/chemokine production by epithelial cells. In this in vitro model devoid of other cellular or molecular interfering partners, IgM and secretory IgM showed stronger bacterial neutralization than secretory IgA. Together, these data suggest that mucosally delivered antibody preparations may be most effective when combining both secretory-like IgA and IgM, which, together, play a crucial role in preserving several levels of epithelial cell integrity.

Polyclonal intravenous immunoglobulin: an important additional strategy in sepsis?

Sepsis syndrome is characterized by a systemic inflammatory response to infection potentially leading to acute organ failure and rapid decline to death. Polyclonal intravenous immune globulin, a blood product derived from human donor blood, in addition to antiinfective activities, also exerts a broad antiinflammatory and immunomodulating effect. Intravenous immunoglobulin (IVIg) has been proposed as adjuvant therapy for sepsis even though the clinical studies demonstrating their efficacy and safety are relatively small. Several systematic reviews and meta-analyses of intravenous immunoglobulin treatment in sepsis have been performed. As a result of heterogeneity across studies and inconsistencies in results, the majority have concluded that more evidence, coming from large, well-conducted randomized controlled trials (RCTs), is required. Moreover the appropriate timing of administration and the identification of specific clinical settings represent a key factor to maximizing their beneficial effect. The authors, in this revision, review the basic mechanisms of action of IVIg, the rationale for their use, and their clinical applications.

Proteobacteria-specific IgA regulates maturation of the intestinal microbiota

The intestinal microbiota changes dynamically from birth to adulthood. In this study we identified γ-Proteobacteria as a dominant phylum present in newborn mice that is suppressed in normal adult microbiota. The transition from a neonatal to a mature microbiota was in part regulated by induction of a γ-Proteobacteria-specific IgA response. Neocolonization experiments in germ-free mice further revealed a dominant Proteobacteria-specific IgA response triggered by the immature microbiota. Finally, a role for B cells in the regulation of microbiota maturation was confirmed in IgA-deficient mice. Mice lacking IgA had persistent intestinal colonization with γ-Proteobacteria that resulted in sustained intestinal inflammation and increased susceptibility to neonatal and adult models of intestinal injury. Collectively, these results identify an IgA-dependent mechanism responsible for the maturation of the intestinal microbiota.

Benefits and risks of IgA in immunoglobulin preparations

The case of Immunoglobulin A (IgA) in transfusion medicine is unsettled: on one hand IgA is an important component of adaptive immunity and its deficiency may cause disease, on the other its presence in blood products might induce, in rare instances, allergy-like symptoms if not anaphylaxis. The practice with i.v. immunoglobulins currently changes as up to 10% concentrated preparations are given at fast rates hence even trace amounts of IgA contained in these IgG preparations can cause unexpected (side-) effects. Fortunately, the spectrum of sensitive IgA assays, along with anti-IgA screening assays now permits laboratories to narrow down IgA-dependent transfusion reactions to the real cases, in which IgA was the decisive trigger of anaphylaxis, proven or not by the presence of anti-IgA of the IgG or even IgE class. Tolerance to allogenic IgA has recently been reported. The known association of HLA with IgA deficiency (IgAD) has now been completed with an association to the nonsynonymous variant in IFHI1, allowing physicians to more precisely spot recipients at risk for an IgA-dependent transfusion reaction. Our review, along with our own experience here in Switzerland, allows us to conclude that IgA is a beneficial antibody rather than an allergen to be placed at the end of the list of non-infectious transfusion complications such as TRALI, febrile non-hemolytic reactions, purpura or volume overload.

Pediatric Sepsis Guidelines: Summary for resource-limited countries

Justification:

Pediatric sepsis is a commonly encountered global issue. Existing guidelines for sepsis seem to be applicable to the developed countries, and only few articles are published regarding application of these guidelines in the developing countries, especially in resource-limited countries such as India and Africa.

Process:

An expert representative panel drawn from all over India, under aegis of Intensive Care Chapter of Indian Academy of Pediatrics (IAP) met to discuss and draw guidelines for clinical practice and feasibility of delivery of care in the early hours in pediatric patient with sepsis, keeping in view unique patient population and limited availability of equipment and resources. Discussion included issues such as sepsis definitions, rapid cardiopulmonary assessment, feasibility of early aggressive fluid therapy, inotropic support, corticosteriod therapy, early endotracheal intubation and use of positive end expiratory pressure/mechanical ventilation, initial empirical antibiotic therapy, glycemic control, and role of immunoglobulin, blood, and blood products.

Objective:

To achieve a reasonable evidence-based consensus on the basis of published literature and expert opinion to formulating clinical practice guidelines applicable to resource-limited countries such as India.

Recommendations:

Pediatric sepsis guidelines are presented in text and flow chart format keeping resource limitations in mind for countries such as India and Africa. Levels of evidence are indicated wherever applicable. It is anticipated that once the guidelines are used and outcomes data evaluated, further modifications will be necessary. It is planned to periodically review and revise these guidelines every 3–5 years as new body of evidence accumulates.

Hyperreactive malarial splenomegaly is associated with low levels of antibodies against red blood cell and Plasmodium falciparum derived glycolipids in Yanomami Amerindians from Venezuela

The immunological basis of the aberrant immune response in hyperreactive malarial splenomegaly (HMS) is poorly understood, but believed to be associated with polyclonal B cell activation by an unidentified malaria mitogen, leading to unregulated immunoglobulin and autoantibody production. HMS has been previously reported in Yanomami communities in the Upper Orinoco region of the Venezuelan Amazon. To investigate a possible association between antibody responses against Plasmodium falciparum and uninfected red blood cell (URBC) glycolipids and splenomegaly, a direct comparison of the parasite versus host anti-glycolipid antibody responses was made in an isolated community of this area. The anti-P. falciparum glycolipid (Pfglp) response was IgG3 dominated, whereas the uninfected red blood cell glycolipid (URBCglp) response showed a predominance of IgG1. The levels of IgG1 against Pfglp, and of IgG4 and IgM against URBCglp were significantly higher in women, while the anti-Pfglp or URBCglp IgM levels were inversely correlated with the degree of splenomegaly. Overall, these results suggest differential regulation of anti-parasite and autoreactive responses and that these responses may be linked to the development and evolution of HMS in this population exposed to endemic malaria. The high mortality rates associated with HMS point out that its early diagnosis together with the implementation of malaria control measures in these isolated Amerindian communities are a priority.

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.

Structural and functional properties of antibodies to the superantigen TSST-1 and their relationship to menstrual toxic shock syndrome

Menstrual toxic shock syndrome (mTSS) is an acute febrile disease accompanied by hypotension and multiple organ involvement. Infection with Staphylococcus aureus producing the superantigen toxic shock syndrome toxin-1 (TSST-1) vaginally is necessary; however, only a small fraction of those infected with TSST-1 producing bacteria actually develop mTSS, suggesting that host factors modulate disease susceptibility. Serum antibodies to the toxin protect against development of the syndrome, but not all antibodies can neutralize the toxin. We set out to determine whether risk of developing the syndrome is related to the absence of neutralizing antibody and if antibody isotypes influence the neutralization capacity. In healthy subjects, TSST-1-binding serum antibodies were exclusively of the IgG and IgM classes; however, toxin-neutralizing capacity was correlated to the TSST-1-specific IgG1 and IgG4 antibodies (r (2)=0.88, p<0.0001 and 0.33, p<0.0086, respectively) but not with IgM antibodies. Specific IgA was not detectable. Compared to healthy matched controls who were colonized vaginally with S. aureus, IgG1 anti-TSST-1 antibodies and toxin neutralizing activity was lacking in all of the acute phases and in the majority of convalescent sera, suggesting that these patients may be incapable of generating TSST-1 neutralizing antibodies. These new findings support the hypothesis that host factors are important in the development of mTSS and that the anti-toxin isotype impacts antibody functionality.

Biological Functions of IgA

Immunoglobulin A (IgA) is the most enigmatic of immunoglobulins. It is by far the most abundant of human Igs, being present in the blood plasma at concentrations approximating 2–3mg/mL, as well as the dominant isotype in most secretions where its output amounts to some 5–8g/day in adults. Furthermore, its evolutionary origins appear to precede the synapsid– diapsid divergence in tetrapod phylogeny (>300 million years ago) because it is present in both mammals and birds and therefore possibly also in reptiles (reviewed in Peppard et al., 2005); an IgA-like molecule has now been identified in a lizard (Deza et al., 2007).

Intravenous polyclonal IgM-enriched immunoglobulin therapy in sepsis: a review of clinical efficacy in relation to microbiological aetiology and severity of sepsis

The efficacy of intravenous polyclonal immunoglobulin (IVIG) as adjunct therapy in sepsis has long been debated. Clinical trials have yielded contradicting results, in part due to the varying study design and varying microbiological aetiologies. In most trials, the study drug has been IVIG containing polyclonal IgG. However, in recent reports, the efficacy of IgM-enriched IVIG as adjunct therapy in sepsis has been highlighted. Here we review studies on IgM-enriched IVIG therapy in sepsis and we discuss the clinical efficacy in relation to microbiological aetiology and severity of sepsis. The results suggest that patients most likely to benefit from IgM-enriched IVIG therapy are those with Gram-negative septic shock.

Necrotizing fasciitis: pathogenesis and treatment

Necrotizing fasciitis is a rapidly progressive, life-threatening infection and a true infectious disease emergency. Despite much clinical experience, the management of this disease remains suboptimal, with mortality rates remaining approximately 30%. Necrotizing fasciitis rarely presents with obvious signs and symptoms and delays in diagnosis enhance mortality. Therefore, successful patient care depends on the physician's acumen and index of suspicion. Prompt surgical debridement, intravenous antibiotics, fluid and electrolyte management, and analgesia are mainstays of therapy. Adjunctive clindamycin, hyperbaric oxygen therapy and intravenous immunoglobulin are frequently employed in the treatment of necrotizing fasciitis, but their efficacy has not been rigorously established. Improved understanding of the pathogenesis of necrotizing fasciitis has revealed new targets for rationally designed therapies to improve morbidity and mortality.

Nekrotisierende Fasziitis nach Injektionstherapie im Schultergelenk

Necrotizing fasciitis is an inflammatory, rapidly progressive soft tissue infection usually caused by Streptococcus pyogenes or by a combination of aerobic and anaerobic microorganisms. Here we report the case of a patient who developed necrotizing fasciitis near the site of therapeutic injections. An orthopaedic surgeon in private practice had given the 74-year-old patient, who suffered from left shoulder pain, cortisone injections in his left shoulder joint. During the course of this therapy, the patient developed necrotizing fasciitis. Despite radical surgical debridement of the patient's back, left thorax and amputation of his left arm, the patient expired 15 h after arriving at our department. In cases such as these, patient survival depends upon an early diagnosis followed by immediate radical surgical intervention including complete opening of fascial compartments and excision of necrotic tissues.

Immunoglobulin M-enriched intravenous polyclonal immunoglobulins reduce bacteremia following Klebsiella pneumoniae infection in an acute respiratory distress syndrome rat model

Mechanical ventilation is known to induce bacterial translocation from the lung into the systemic circulation. This study determined the effect of immunoglobulin M (IgM)-enriched polyclonal immunoglobulins on bacteremia due to ventilation-induced translocation in an acute respiratory distress syndrome (ARDS) rat model with Klebsiella-induced pneumonia. After whole lung lavage, Sprague-Dawley rats intravenously received either a high dose or a low dose of an immunoglobulin preparation, or an albumin solution as control, followed by an intratracheal injection of a Klebsiella pneumoniae solution. Blood colony-forming units (CFUs) in the treatment groups were significantly lower during the 3-hour ventilation period compared to the control group. The authors conclude that IgM-enriched polyclonal immunoglobulins lead to a reduction of bacteria in blood of surfactant-deficient, ventilated rats infected with Klebsiella pneumoniae.

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.

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.

Intravenous immunoglobulin for prophylaxis and therapy of sepsis

Intravenous immunoglobulins (IVIg) are widely used as prophylaxis against and as supplemental treatment of sepsis and septic shock, although this concept does not belong to the currently approved medical indications for IVIg products. A reduction in mortality by pooled IVIgGMA more than by IVIgG alone was reported in the recent Cochrane database (eight trials, 492 patients). However, the failure to reduce mortality by IVIgG in the score-based immunoglobulin treatment in sepsis study (653 patients) seriously questions whether IVIgG may reduce mortality. Patients with streptococcal toxic shock syndrome might benefit from IVIg, although it remains questionable whether large controlled trials will ever be available. Intravenous immunoglobulin prophylaxis can undoubtedly reduce the occurrence of infections-especially pneumonias-in at-risk patients. More data are necessary to ascertain whether this beneficial effect is linked with a reduction of infection-related morbidity and mortality. Ongoing studies will document whether cardiac surgery patients with escalating systemic inflammatory response syndrome or mediastinitis will benefit from IVIg. IgM-specific complement inactivation may further stimulate the discussion of IVIgGMA superiority over IVIgG.

[Staphylococcal and streptococcal pediatric toxic syndrome from 1998 to 2000. Data from the National Center for Staphylococcal Toxemia]

The clinical and microbial settings of staphylococcal and streptococcal toxemia in pediatric patients were investigated by the French National Reference Center for Staphylococcal Toxemia. From 1998 to 2000, the number of cases was low in regard to the usual putative incidence of these toxemia; this low incidence was probably linked to the passive collection of cases. The most significant finding was the evidence of skin infections as the source of the majorities of staphylococcal toxic shock syndrome and staphylococcal scarlet fever as described for streptococcal toxic shock syndrome or nosocomial suppurative infections. Moreover, most of scalded skin syndrome were from pediatric patients and were exceptional in adults. For other syndromes, no significant original findings were observed.

Reciprocal, temporal expression of SpeA and SpeB by invasive M1T1 group a streptococcal isolates in vivo

The streptococcal pyrogenic exotoxins (Spes) play a central role in the pathogenesis of invasive group A streptococcal (GAS) infections. The majority of recent invasive GAS infections have been caused by an M1T1 strain that harbors the genes for several streptococcal superantigens, including speA, speB, speF, speG, and smeZ. However, considerable variation in the expression of Spe proteins among clonal M1 isolates has been found, and many of the speA-positive M1 strains do not produce detectable amounts of SpeA in vitro. This study was designed to test the hypothesis that speA gene expression can be induced in vivo. A mouse infection chamber model that allows sequential sampling of GAS isolates at various time points postinfection was developed and used to monitor the kinetics of Spe production in vivo. Micropore Teflon diffusion chambers were implanted subcutaneously in BALB/c mice, and after 3 weeks the pores became sealed with connective tissue and sterile fluid containing a white blood cell infiltrate accumulated inside the infection chambers. Representative clonal M1T1 isolates expressing no detectable SpeA were inoculated into the implanted chambers, and the expression of SpeA in the aspirated aliquots of the chamber fluid was analyzed on successive days postinfection. Expression of SpeA was detected in the chamber fluid as early as days 3 to 5 postinfection in most animals, with a significant increase in expression by day 7 in all infected mice. Isolates recovered from the chamber and grown in vitro continued to produce SpeA even after 21 passages in vitro, suggesting stable switch on of the speA gene. A temporal relation between the upregulation of SpeA expression and the downregulation of SpeB expression was observed in vivo. These data suggest that in vivo host and/or environmental signals induced speA gene expression and suppressed speB gene expression. This underscores the role of the host-pathogen interaction in regulating the expression of streptococcal virulence factors in vivo. The model described here should facilitate such studies.

Superantigen antagonist peptides

The production of superantigenic exotoxins by Gram positive bacteria underlies the pathology of toxic shock syndrome. Future treatment strategies for superantigen-mediated diseases are likely to be directed at blocking the three-way interaction between superantigen, T cell receptor and major histocompatibility class II molecule, which inititates an excessive and disordered inflammatory response. In this article, we review the first published data to address one such strategy in the context of other recognised and experimental treatments.