Role of natural antibodies in immune homeostasis: IVIg perspective

Case Series: Efficacy of Polyclonal Intravenous Immunoglobulin for Refractory Clostridioides difficile Infection

BACKGROUND

Intravenous immunoglobulin (IVIg) for Clostridioides difficile infection (CDI) no longer features in treatment guidelines. However, IVIg is still used by some clinicians for severe or recurrent CDI (rCDI) cases. The main objective of this study was to investigate the efficacy of IVIg and to identify possible predictors of disease resolution post IVIg administration for patients with CDI.

METHODS

This retrospective observational cohort study of patients ≥2 years old hospitalised with severe, relapsing, or rCDI treated with IVIg therapy was performed in a large UK tertiary hospital between April 2018 and March 2023. Scanned electronic notes from patient admissions and clinical reporting systems were used to collect relevant data.

RESULTS

In total, 20/978 patients diagnosed with CDI over the 5-year study were treated with IVIg. Twelve (60%) had hospital-onset CDI. Eleven of the twenty patients (55%) responded to treatment, with a mean of 8.6 (SD 10.7) days to disease resolution. Sixteen (80%) patients were treated for severe CDI and four (20%) for rCDI (n = 3) and relapsing CDI (n = 1). There were no statistically significant differences in possible independent predictors of disease resolution post IVIg administration between groups. There was an average of 6.2 (4.9) days to IVIg administration after diagnosis with no difference between responders and non-responders (p = 0.88) and no further significant difference in additional indicators. Four (36%) of the responders were immunosuppressed compared to just one (11%) of the non-responders (p = 0.15). Six of the responders (two with recurrent and four with severe CDI) improved rapidly within 2 days, and three of these were immunosuppressed.

CONCLUSION

We observed disease resolution post IVIg therapy in over 50% of patients with refractory CDI. Our data also support a potential enhanced effect of IVIg in immunosuppressed individuals. Thus, the role of IVIg for CDI treatment, particularly in the immunosuppressed, warrants future case-control studies coupled to mechanistic investigations to improve care for this ongoing significant healthcare-associated infection.

Intravenous immunoglobulin therapy in immunoglobulin A vasculitis with gastrointestinal tract involvement

OBJECTIVE

The aim of this study is to evaluate the outcomes of patients who received intravenous immunoglobulin (IVIG) for immunoglobulin A vasculitis (IgAV) with gastrointestinal (GI) tract involvement, and to determine the differences between the groups that responded to IVIG and those that did not.

METHODS

This retrospective study comprised 152 patients with IgAV between 2018 and 2022. Sixty-five patients (43%) had GI tract involvement. Patients with IgAV-GI involvement who had been treated with IVIG were evaluated. Patients were classified with IgAV according to the 2008 Ankara-EULAR/PRINTO/PRES. Their demographics, presentation, and management are reported.

RESULTS

Twelve (7 boys/5 girls) of these patients were treated with IVIG. The median age was 90.1 (31-177) months. The mean follow-up period was 30.6 ± 9.9 months. All patients had skin involvement, joint involvement (arthralgia or arthritis), and abdominal pain. All 12 patients were given steroids (30 mg/kg/day pulse methylprednisolone for 3-7 days, followed by 2 mg/kg/day steroids) before IVIG. Nine patients received cyclophosphamide treatment (four before IVIG and five after IVIG). Complete remission was achieved in 5 of the patients with IVIG. Four patients were diagnosed with IgAV concomitant familial Mediterranean fever, and colchicine treatment was initiated.

CONCLUSIONS

IVIG may be used in steroids and/or immunosuppressive drug resistant IgAV. It can be considered as a treatment option, especially in patients with multi-organ/system involvement, comorbid inflammatory diseases such as familial Mediterranean fever, and in patients with IgAV-GI tract involvement resistant to standard treatment in the advanced pediatric age group.

Efficacy and safety of blood derivatives therapy in Alzheimer's disease: a systematic review and meta-analysis

BACKGROUND

Blood derivatives therapy is a conventional clinical treatment, while the treatment for Alzheimer's disease (AD) is relatively novel. To provide clinical references for treating AD, this meta-analysis was performed to evaluate the efficacy and safety of blood derivatives therapy on the patients with AD.

METHODS

A systematic articles search was performed for eligible studies published up to December 6, 2021 through the PubMed, Embase, Cochrane library, ClinicalTrials.gov , Chinese National Knowledge Infrastructure database, and Wanfang databases. The included articles were screened by using rigorous inclusion and exclusion criteria. Study selection and data-extraction were performed by two authors independently. Random effects model or fixed effects model was used. Quality of studies and risk of bias were evaluated according to the Cochrane risk of bias tool. All analyses were conducted using Review Manager 5.4. The study was designed and conducted according to the Preferring Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline.

RESULTS

A total of three plasma administrations (two plasma exchange and one young plasma infusion) and five intravenous immunoglobulin (IVIG) randomized controlled trials with a sample size of 1148 subjects diagnosed with AD were included. There was no significant difference in cognitive improvement and all-cause discontinuation between intervention and placebo groups (RR 1.10, 95% CI 0.79-1.54). And Intervention groups showed not a statistically significant improvement in cognition of included subjects measured by the ADAS-Cog (MD 0.36, 95% CI 0.87-1.59), ADCS-ADL (MD -1.34, 95% CI - 5.01-2.32) and NPI (MD 2.20, 95% CI 0.07-4.32) score compared to the control groups. IVIG is well tolerated for AD patients even under the maximum dose (0.4 g/kg), but it is inferior to placebo in Neuropsychiatric Inventory scale in AD patients (MD 2.19, 95% CI 0.02-4.37).

CONCLUSIONS

The benefits of blood derivatives therapy for AD are limited. It is necessary to perform well-designed randomized controlled trials with large sample sizes focusing on the appropriate blood derivatives for the specific AD sub-populations in the future.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42021233886.

Role of HLA-I Structural Variants and the Polyreactive Antibodies They Generate in Immune Homeostasis

Cell-surface HLA-I molecules consisting of β2-microglobulin (β2m) associated heavy chains (HCs), referred to as Face-1, primarily present peptides to CD8+ T-cells. HCs consist of three α-domains, with selected amino acid sequences shared by all alleles of all six isoforms. The cell-surface HLA undergoes changes upon activation by pathological conditions with the expression of β2m-free HCs (Face-2) resulting in exposure of β2m-masked sequences shared by almost all alleles and the generation of HLA-polyreactive antibodies (Abs) against them. Face-2 may homodimerize or heterodimerize with the same (Face-3) or different alleles (Face-4) preventing exposure of shared epitopes. Non-allo immunized males naturally carry HLA-polyreactive Abs. The therapeutic intravenous immunoglobulin (IVIg) purified from plasma of thousands of donors contains HLA-polyreactive Abs, admixed with non-HLA Abs. Purified HLA-polyreactive monoclonal Abs (TFL-006/007) generated in mice after immunizing with Face-2 are documented to be immunoregulatory by suppressing or activating different human lymphocytes, much better than IVIg. Our objectives are (a) to elucidate the complexity of the HLA-I structural variants, and their Abs that bind to both shared and uncommon epitopes on different variants, and (b) to examine the roles of those Abs against HLA-variants in maintaining immune homeostasis. These may enable the development of personalized therapeutic strategies for various pathological conditions.

Increased Frequency of Activated Switched Memory B Cells and Its Association With the Presence of Pulmonary Fibrosis in Diffuse Cutaneous Systemic Sclerosis Patients

Disease-associated, high-affinity pathological autoantibody production is a well-described consequence of immune dysregulation affecting B cells in systemic sclerosis (SSc), including the distribution of B-cell subsets. We have previously shown that the increased relative frequency of CD19+CD27+IgD- switched memory B cells is associated with the severe form of SSc. This study sought to analyze memory B cell subsets using an extended range of markers for further subdivision based on CD19, IgD, CD27, CD38 and CD95 phenotype, to define relationship between the alterations of memory B cell subsets and the clinical features of SSc. Peripheral blood samples were obtained from 21 SSc patients, including 14 diffuse (dcSSc) and 7 limited (lcSSc) cutaneous SSc patients, with disease duration of 2.7 ( ± 1.6) years. After purification of CD19+ B cells, multiparametric flow cytometry was performed and the frequencies of CD19+IgD-CD27-CD38+ double negative (DN) 1, CD19+IgDloCD27+CD38+ unswitched, CD19+IgD-CD27+CD38+CD95- resting switched and CD19+IgD-CD27+CD38-CD95+ activated switched memory (ASM) B cells were determined, and correlated with clinical features of SSc. The dcSSc patients had a higher frequency of ASM B cells (p = 0.028) compared to lcSSc patients. The percentage of ASM B cells was elevated in anti-Scl-70 (anti-topoisomerase I) antibody positive patients compared to negative patients (p = 0.016). Additionally, the frequency of ASM B cells was also increased in patients with pulmonary fibrosis (p = 0.003) suggesting that patients with severe form of SSc have higher ASM B cell ratios. Furthermore, the ratio of DN1 B cells was decreased (p = 0.029), while the level of anti-citrate synthase IgG natural autoantibody was elevated (p = 0.028) in patients with active disease. Our observations on the increase of ASM B cells in dcSSc and in patients with pulmonary fibrosis may point to the association of this alteration with the severe form of the disease. Functionally the correlation of ASM B cells as effector memory-plasma cell precursors with anti-topoisomerase I antibody positivity could reflect their contribution to pathological autoantibody production, whereas the decrease of memory precursor DN B cells and the increase of anti-citrate synthase IgG autoantibody may have potential significance in the assessment of disease activity.

Characterization of antibodies in human immunoglobulin products from different regions worldwide

AIM

The antibody levels against a broad spectrum of pathogens were assessed in commercial intravenous immunoglobulin (IVIG) manufactured from pooled plasma obtained from different global regions.

METHODS

Twenty-four IVIG commercial lots from eight manufacturers corresponding to 12 brands were analyzed. The plasma was collected in 10 countries/regions. Depending on each pathogen, antibody levels were measured using specific commercial IgG-specific enzyme immunoassay kits or by cell culture neutralization test and guinea pig skin neutralization test. A principal component analysis was performed.

RESULTS

For polio and diphtheria (reference markers of the US authorities), all IVIGs had relevant titers in accordance with reference levels. IVIGs from Canada, Australia, and the USA were positive for titers against globally distributed pathogens or those under vaccination programs in the developed world (parainfluenza, Epstein-Barr, varicella-zoster, influenza B, parvovirus B19, and measles viruses). IVIG from Taiwan and Hong Kong showed low antibody titers for these pathogens but high titers for Pseudomonas aeruginosa. IVIG from India had high titers for pathogens frequently found in developing countries (West Nile, dengue, chikungunya, and hepatitis E viruses and Streptococcus pneumoniae). IVIGs from Argentina, Spain, Israel, and Czechia showed intermediate antibody concentrations.

CONCLUSION

The antibody profile in IVIG was greatly influenced by regional characteristics including climate, vaccination programs, and the prevalence of pathogens in the different countries and regions.

Update on treatment and preventive interventions against COVID-19: an overview of potential pharmacological agents and vaccines

The outbreak of coronavirus disease 2019 (COVID-19) triggered by the new member of the coronaviridae family, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has created an unprecedented challenge for global health. In addition to mild to moderate clinical manifestations such as fever, cough, and fatigue, severe cases often developed lethal complications including acute respiratory distress syndrome (ARDS) and acute lung injury. Given the alarming rate of infection and increasing trend of mortality, the development of underlying therapeutic and preventive treatment, as well as the verification of its effectiveness, are the top priorities. Current research mainly referred to and evaluated the application of the empirical treatment based on two precedents, severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), including antiviral drugs targeting different stages of virus replication, immunotherapy modulating the overactivated inflammation response, and other therapies such as herbal medicine and mesenchymal stem cells. Besides, the ongoing development of inventing prophylactic interventions such as various vaccines by companies and institutions worldwide is crucial to decline morbidity and mortality. This review mainly focused on promising candidates for the treatment of COVID-19 and collected recently updated evidence relevant to its feasibility in clinical practice in the near future.

Do different IgG repertoires play a role in B- and T-cell functional modulation during ontogeny? The "hooks without bait" theory

The mechanisms by which immunoglobulin (Ig)G can modulate immunity have been investigated over the past few decades. In the past three years, some studies have demonstrated that IgG can play a pivotal role in mediating complex interactions that result in functional lymphocyte modulation during maturation in self or offspring primary lymphoid organs. This effect appears to be dependent on the IgG repertoire in the absence of the influence of antigens and the functionality of diverse cell populations, including B, αβT (CD4 T and CD8 T), invariant natural killer T and γδT cells, in mice and humans. Based on the literature, especially on findings resulting from the therapeutic use of purified IgG (intravenous Ig) and recent pieces of evidence obtained by my group, the "hooks without bait" theory is described here to guide the future development of therapies for specific immune regulation.

Anti-Neuronal Antibodies Within the IVIg Preparations: Importance in Clinical Practice

Our study objective was testing for anti-neuronal autoantibodies within commercially available intravenous immunoglobulin (IVIg) preparations. Sixteen samples from 5 different commercially available IVIg preparations were tested with cell-based assays (CBA) and enzyme-linked immunosorbent assay (ELISA) to detect and characterize common neuronal autoantibodies, and with immunohistochemistry on teased fibers from mouse sciatic nerve and on mouse brain sections to screen for nodal and not yet identified neuronal antigens. In 15/16 IVIg preparations, anti-GAD antibodies were detected in titers ranging from 40 to 1507 IU/mL, as typically seen in type 1 diabetes, but not in the range (> 2000 IU/mL) seen in GAD-positive neurological patients. None of the preparations was however positive with anti-GAD CBA. Antibodies to AQP4 were also detected by ELISA in 15/16 IVIg preparations with titers comparable to those seen in AQP4-seropositive NMO patients; with CBA, however, all IVIg samples were AQP4-negative. IVIg preparations contained IgG-anti-MAG antibodies by ELISA at statistically significant higher titers compared to controls. Two of the 16 IVIg samples were positive for human 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) antibodies. All IVIg preparations were negative for antibodies to MOG, NMDAR, anti-nodal, and other neuronal-specific proteins. IVIg preparations contain antibodies against GAD and AQP4 in titers comparable to those seen in autoimmune patients when tested by ELISA, but not by CBA or tissue immunohistochemistry, suggesting that the autoantibodies within the IVIg are against linear rather than structural epitopes, as part of the natural antibody immune repertoire. The information is clinically important for diagnosis when testing patients' sera after they have received therapy with IVIg to avoid false interpretation.

The level of natural autoantibodies to IFN-gamma in varicella infection treated with antiviral drug Anaferon for children: A pilot study

Natural circulating antibodies (NAbs) to endogenous regulators have shown to be potential biomarkers in medicine. Due to the lack of reliable assays, only few of them have been well studied. To employ NAbs as biomarkers, an evaluation of changes over the course of a treatment is required. This paper describes our work to analyze the dynamics of NAbs titer to interferon-gamma (IFN-γ) among healthy children of different age and in patients with varicella infection receiving an antiviral drug Anaferon for children (AC, the API are highly diluted antibodies to IFN-γ) in comparison with placebo, and to correlate the findings with the treatment results. IFN-γ plays an essential role during varicella infection, and this fact causes the consequent increase of NAbs to IFN-γ level. The mean anti-IFN-γ NAbs level in the healthy volunteer group was 101 × 10³ U/ml (age: 0-15 years), which was significantly lower than the mean pre-treatment value in patients with varicella infection 167 × 10³ U/ml (age: 3-17 years). In the AC group, the NAbs level observed on days 5 and 10 decreased significantly to a level of 154 × 10³ U/ml, whereas in the placebo group it continued to rise in a time-dependent manner reaching 229 × 10³ U/ml on day 10. Our findings suggest that treatment with AC is characterized by "normalization" of the anti-IFN-γ NAbs levels in patients with varicella infection.

Toll-Like Receptor Mediated Activation of Natural Autoantibody Producing B Cell Subpopulations in an Autoimmune Disease Model

Altered expression and function of the Toll-like receptor (TLR) homologue CD180 molecule in B cells have been associated with autoimmune disorders. In this study, we report decreased expression of CD180 at protein and mRNA levels in peripheral blood B cells of diffuse cutaneous systemic sclerosis (dcSSc) patients. To analyze the effect of CD180 stimulation, together with CpG (TLR9 ligand) treatment, on the phenotype defined by CD19/CD27/IgD/CD24/CD38 staining, and function (CD69 and CD180 expression, cytokine and antibody secretion) of B cell subpopulations, we used tonsillar B cells. After stimulation, we found reduced expression of CD180 protein and mRNA in total B cells, and CD180 protein in B cell subpopulations. The frequency of CD180+ cells was the highest in the CD19+CD27+IgD+ non-switched (NS) B cell subset, and they showed the strongest activation after anti-CD180 stimulation. Furthermore, B cell activation via CD180 induced IL-6 and natural autoantibody secretion. Treatment with the combination of anti-CD180 antibody and CpG resulted in increased IL-6 and IL-10 secretion and natural autoantibody production of B cells. Our results support the role of CD180 in the induction of natural autoantibody production, possibly by NS B cells, and suggest an imbalance between the pathologic and natural autoantibody production in SSc patients.

Differential immunomodulation of T-cells by immunoglobulin replacement therapy in primary and secondary antibody deficiency

Patients with primary or secondary antibody deficiency (PAD or SAD) are at increased risk of recurrent infections that can be alleviated by immunoglobulin replacement therapy (IRT). In addition to replenishing antibody levels, IRT has been suggested to modulate immune response in patients with antibody deficiency. Although both commonly treated with IRT, the underlying causes of PAD and SAD vary greatly, suggesting differential modulation of T-cell function that may lead to different responses to IRT. To explore this, peripheral blood mononuclear cells (PBMCs) were sampled from 17 PAD and 14 SAD patients before and 2–10 months after initiation of IRT, and analyzed for changes in T-cell phenotype and function. Proportions of CD4, CD8, Treg, or memory T-cells did not significantly change post-IRT compared to pre-IRT. However, we report distinct modulation in T-cell function between PAD and SAD patients post-IRT. Upon α-CD3/CD28 stimulation, proportion of IFN-γ+ CD4 and CD8 T-cells increased in SAD (p = 0.005) but not PAD patients post-IRT compared to baseline. Interestingly, total T-cell proliferation was reduced post-IRT in both PAD and SAD patients, although the reduction in proliferation was primarily due to reduced CD4 T-cell proliferation in PAD (p = 0.025) in contrast to CD8 T-cells in SAD (p = 0.042). In summary, even though IRT provides patients with passive humoral immunity-mediated protection in PAD and SAD, our findings suggest that IRT immunomodulation of T-cells is different in T-cell subsets depending on underlying immunodeficiency.

Severe acute respiratory failure due to Sai-rei-to-induced lung injury successfully treated by multi-modal therapy including immunosuppressive therapy, plasma exchange, and intravenous immunoglobulin: A case report

Corticosteroid therapy may not be enough to control pneumonitis in some cases of severe drug-induced lung injury (DLI); however, an advanced treatment strategy for such cases is lacking. Here, we report the case of an 88-year-old man who presented with severe DLI, caused by Sai-rei-to. The patient visited our hospital complaining of progressive dyspnea. High-resolution computed tomography of the chest demonstrated bilateral patchy ground-glass opacities and infiltrative shadows. Nasal high-flow oxygen therapy was initiated because of severe hypoxemia. Bronchoalveolar lavage on admission revealed diffuse alveolar hemorrhage. Further, as the patient had started taking Sai-rei-to a month earlier, DLI caused by Sai-rei-to was the most likely diagnosis. Therefore, Sai-rei-to was stopped and steroid pulse therapy was initiated. However, he still required high-flow oxygen therapy. We considered an alternative diagnosis of Goodpasture syndrome or anti-neutrophil cytoplasmic antibody (ANCA) related vasculitis. We initiated the administration of cyclosporin A and therapeutic plasma exchange (TPE), but his respiratory condition did not improve satisfactorily. Therefore, we also initiated intravenous immunoglobulin (IVIG) therapy for the treatment of potential vasculitis. Subsequently, his respiratory status began to improve. Further, tests for anti-glomerular basement membrane antibody, myeloperoxidase-ANCA, and proteinase 3-ANCA revealed negative results. Drug-induced lymphocyte stimulation test performed six months after withdrawing methylprednisolone was positive for Sai-rei-to. Thus, the final diagnosis was DLI due to Sai-rei-to. Our findings demonstrate that in cases of severe acute respiratory failure due to DLI, the multi-modal therapy with plasma exchange and IVIG in addition to conventional treatment with prednisolone and immunosuppressant may be beneficial.

Changes in concentrations of tau-reactive antibodies are dependent on sex in Alzheimer's disease patients

The presence of pre-existing natural antibodies against Alzheimer's disease (AD) pathological proteins might interfere with immune responses to therapeutic vaccination with these proteins. We aimed to compare levels of antibodies in CSF and serum: We observed higher reactivity of natural tau-reactive antibodies towards phosphorylated bovine tau protein than to human recombinant (non-phosphorylated) tau protein. Males with MCI-AD had higher amounts of these antibodies than corresponding controls. Concentrations of antibodies were lower in females with the MCI-AD than in control females. These findings may have implications for tau vaccination trials.

Use of human immunoglobulins as an anti-infective treatment: the experience so far and their possible re-emerging role

INTRODUCTION

Pooled human immunoglobulins (IGs) are prepared from plasma obtained from healthy donors as a concentrated antibody-containing solution. In addition, high-titer IGs (hyperimmune) against a specific pathogen can be obtained from vaccinated or convalescing donors. Currently, IGs can be used for the treatment of a variety of infections for which no specific therapy exists or that remain difficult to treat. Moreover, the recent pathogen outbreaks for which there is no approved treatment have renewed attention to the role of convalescent plasma and IGs. Areas covered: In this review, a historical perspective of the use of sera and IGs in humans as anti-infective agents (any viral, bacterial, parasitic infection), excluding immunodeficient patients, is presented from early development to the latest clinical studies. A Medline search was conducted to examine the peer-reviewed literature, with no date limits. Expert commentary: Human pooled plasma-derived IG products benefit from the polyclonal response of every individual donor and from the interindividual variability in such response. The trend to increased availability of vaccines for infectious diseases also opens new potential applications of hyperimmune IGs for emerging or re-emerging infectious diseases (e.g.: Ebola, Zika, Dengue), for the prevention and treatment in the general population, healthcare personnel and caregivers.

Intravenous immunoglobulin: pharmacological properties and use in polyneuropathies

INTRODUCTION

Intravenous immunoglobulin (IVIg) is increasingly used for the treatment of autoimmune and systemic inflammatory diseases with both licensed and off-label indications. The mechanism of action is complex and not fully understood, involving the neutralization of pathological antibodies, Fc receptor blockade, complement inhibition, immunoregulation of dendritic cells, B cells and T cells and the modulation of apoptosis. Areas covered: First, this review describes the pharmacological properties of IVIg, including the composition, mechanism of action, and adverse events. The second part gives an overview of some of the immune-mediated polyneuropathies, with special focus on the pathomechanism and clinical trials assessing the efficacy of IVIg. A literature search on PubMed was performed using the terms IVIg, IVIg preparations, side effects, mechanism of action, clinical trials, GBS, CIDP. Expert opinion: Challenges associated with IVIg therapy and the treatment possibilities for immune-mediated polyneuropathies are discussed. The availability of IVIg is limited, the expenses are high, and, in several diseases, a chronic therapy is necessary to maintain the immunomodulatory effect. The better understanding of the mechanism of action of IVIg could open the possibility of the development of disease-specific, targeted immune therapies.

The Homophilic Domain - An Immunological Archetype

The homophilic potential emerges as an important biological principle to boost the potency of immunoglobulins. Since homophilic antibodies in human and mouse sera exist prior environmental exposure, they are part of the natural antibody repertoire. Nevertheless, hemophilic properties are also identified in induced antibody repertoire. The use of homophilicity of antibodies in the adaptive immunity signifies an archetypic antibody structure. The unique feature of homophilicity in the antibody repertoire also highlights an important mechanism to boost the antibody potency to protect against infection and atherosclerosis as well to treat cancer patients.

Intravenous IgG (IVIG) and subcutaneous IgG (SCIG) preparations have comparable inhibitory effect on T cell activation, which is not dependent on IgG sialylation, monocytes or B cells

IVIG modulates T cell activation in vitro and inflammatory-autoimmune conditions in vivo. Sialylation of IgG, Fc receptor interactions, modulation of monocyte/macrophage/B cell functions have been implicated in IVIG effects. Subcutaneous IgG (SCIG) therapy is increasingly used for IgG replacement but whether these preparations share the effects of IVIG on T cell modulation is not documented. We compared the potency of SCIG-Hizentra™ (20% IgG preparation) with IVIG-Privigen® (10% IgG) for T cell inhibition, and assessed the involvement of IgG sialylation, monocytes and B cells in this process. Human PBMCs or sorted cells were cultured 3-7 days, and T cells were stimulated with immobilized anti-CD3 mAb or Candida antigen. Thymidine incorporation into DNA was quantitated and cytokines assayed by ELISA/Luminex® assay. IVIG and SCIG both dose-dependently (1-20mg/ml) inhibited (up to >80%) T cell proliferation to anti-CD3 mAb. Response to Candida albicans was comparably inhibited by IVIG and SCIG by 50-80% at 10mg/ml with inhibition even at 3mg/ml (P<0.05). These effects were not affected by depletion of sialic acid containing IgG using neuraminidase treatment or lectin affinity chromatography. With anti-CD3 or Candida stimulation, IL-1β, IL-2, IL-5, IL-6, IL-13, GMCSF, TNF-α, interferon-γ (with anti-CD3) and IL-17 (with Candida) levels were suppressed by IVIG or SCIG, with no effect on IL-4, IL-10, IL-12, IL-15 or TGFβ. Monocytes or B cells were not required for IgG-induced suppression of proliferation, in fact depletion of monocytes potentiated the IgG-induced inhibition. Reconstitution with monocytes restored the original inhibitory effect. These data show that IVIG (Privigen®) and SCIG (Hizentra™) have comparable inhibitory effects on T cell activation, which do not require sialylation of IgG. Inhibition is independent of monocytes or B cells. There is a potent suppression of multiple effector cytokines. Like IVIG, SCIG therapy is expected to show immunomodulatory activity.

Natural (auto)antibodies in calves are affected by age and diet

BACKGROUND

Natural autoantibodies (N(a)ab) were found in every species tested so far, and are likely important in maintaining homeostasis.

OBJECTIVES

(1) To determine N(a)ab in Bos taurus calves, (2) evaluate effects of diet and age on N(a)ab binding repertoires in calves, and (3) delineate bovine liver cell lysate (BLL) antigens related with variation in rumen score and body weight.

ANIMALS AND METHODS

Effects of age and diet on staining of BLL fragments by IgM and IgG antibodies in serum samples collected at 20 or at 26 weeks of age from bull calves either fed a restricted or ad libitum diet were analyzed using quantitative Western blotting. Correlations between fragments stained and grouping of calves were done by Principal Component Analysis (PCA). Redundancy analysis (RDA) was done to relate rumen score and body weight variation at slaughter at 27 weeks of age with stained BLL fragments.

RESULTS

In sera from all calves IgM and IgG antibodies binding BLL antigens were found. Corresponding fragments were stained, but quantitative differences in staining intensities were related to diet and age for both IgM and IgG. PCA revealed that age had a greater influence than diet on BLL fragment staining. RDA suggested that staining by IgM or IgG of specific BLL fragments was related with variation in rumen score and body weight.

CONCLUSIONS AND CLINICAL IMPORTANCE

Analyses of N(a)ab in serum could be a potential tool to estimate the health status of cattle, and be used to evaluate effects of husbandry practices.

Review of bortezomib treatment of antibody-mediated rejection in renal transplantation

SIGNIFICANCE

Development of donor-specific antibodies (DSA) after kidney transplantation is associated with reduced allograft survival. A few strategies have been tested in controlled clinical trials for the treatment of antibody-mediated rejection (AMR), and no therapies are approved by regulatory authorities. Thus development of antihumoral therapies that provide prompt elimination of DSA and improve allograft survival is an important goal.

RECENT ADVANCES

Proteasome inhibitor (PI)-based regimens provide a promising new approach for treating AMR. To date, experiences have been limited to off-label bortezomib use in AMR. Key findings with PI-based therapy are that they provide effective primary and rescue therapy for AMR by prompt reduction in immunodominant DSA and improvements in histologic and renal function. Early and late AMR differ immunologically and in response to PI therapy. Bortezomib-related toxicities in renal transplant recipients are similar to those observed in the multiple myeloma population.

CRITICAL ISSUES

Although preliminary evidence with PI therapy for AMR is encouraging, the evidence is limited. Larger, prospective, randomized controlled trials with long-term follow up are needed. Advancement in endpoints of clinical trial designs and rigorous clinical trials with more standardized adjunct therapies are also required to explore the risks and benefits of AMR treatment modalities.

FUTURE DIRECTIONS

In the next few years, new PIs are likely to be introduced and new approaches would be developed for achieving synergy with PIs. The ultimate goal will be to develop a regimen that delivers reliable, rapid, complete, and durable elimination of DSA with an acceptable safety profile.

IVIG regulates BAFF expression in patients with chronic inflammatory demyelinating polyneuropathy (CIDP)

Recent studies indicate that the cytokine B-cell activating factor (BAFF) is involved in the pathogenesis of chronic inflammatory demyelinating polyneuropathy (CIDP). Intravenous immunoglobulin (IVIg) is standard treatment for CIDP and is known to rapidly modulate increased serum levels of pro-inflammatory cytokines. We evaluated the expression profile of BAFF and its corresponding BAFF-receptor in samples from CIDP patients, focusing on rapid changes before and after IVIg treatment. In CIDP patients BAFF serum concentrations were elevated compared to controls. Treatment with high-dose IVIg restored those elevated BAFF serum levels. Whereas treatment with IVIg did not affect BAFF production in monocytes, antibodies against BAFF could be detected in IVIg preparations, which may explain the short-term decrease of BAFF levels after IVIg treatment. Our data suggest that BAFF plays an important role in the pathogenesis of CIDP and may serve as marker for IVIg treatment response.

Dendritic cell immunoreceptor: a novel receptor for intravenous immunoglobulin mediates induction of regulatory T cells

BACKGROUND

Intravenous immunoglobulin (IVIg) is a polyclonal IgG preparation with potent immunomodulating properties. Our laboratory demonstrated that IVIg significantly increases numbers of forkhead box protein 3-positive regulatory T (Treg) cells through generation of tolerogenic dendritic cells (DCs) in an allergic airways disease model.

OBJECTIVE

We sought to investigate potential receptors on DCs mediating these events.

METHODS

C57BL/6 mice were either sensitized to ovalbumin (OVA) intraperitoneally or through adoptive transfer of OVA-primed DCs and then challenged with intranasal OVA. IVIg was fractionated into sialic acid-enriched IVIg (SA-IVIg) and sialic acid-depleted IVIg (non-SA-IVIg). Dendritic cell immunoreceptor (DCIR) constructs in CHO cells or on DCs were examined by using fluorescent microscopy and flow cytometry.

RESULTS

Administration of SA-IVIg, but not non-SA-IVIg, to OVA-sensitized and OVA-challenged mice induced Treg cells and attenuated airway hyperresponsiveness (AHR) and inflammation comparably with IVIg. Bone marrow-derived dendritic cells cultured with SA-IVIg or IVIg adoptively transferred to mice before OVA challenge induced Treg cells and inhibited AHR. IVIg-treated bone marrow-derived dendritic cells from Fcγ receptor knockout mice inhibited AHR, suggesting IVIg's action was not caused by Fcγ receptor-mediated events. Fluorescently labeled IVIg or SA-IVIg bound DCs and colocalized specifically to the C-type lectin DCIR. IVIg binding to DCIR induced phosphorylation of Src homology domain 2-containing protein tyrosine phosphatase (SHP) 2 and Src homology domain 2-containing inositol phosphatase 1 (SHIP-1) and internalization of IVIg into DCs. Inhibition of IVIg binding to DCIR by small interfering RNA completely blocked induction of Treg cells. Inhibition of SHP-2 or abrogation of IgG internalization through clatherin inhibitors rendered IVIg ineffective.

CONCLUSIONS

IVIg alleviates allergic airways disease through interaction of SA-IgG with DCIR. DCIR is a novel receptor for IVIg, mediating interaction of innate and adaptive immunity in tolerogenic responses.

Management of antibody-mediated rejection in transplantation

Despite intensive traditional immunosuppressive therapy, rates of graft loss have approximated 15% to 20% at 1 year following antibody-mediated rejection (AMR) in solid organ transplant recipients. Therefore, the development of antihumoral therapies that provide prompt elimination of donor-specific anti-HLA antibodies and improve allograft survival is an important goal. Traditional treatment modalities for AMR deplete B-cell populations but not the cell at the source of antibody production, the mature plasma cell. Plasma cell-targeted therapies using proteasome inhibition is a novel approach to treating AMR. This review discusses current and emerging treatment modalities used for AMR.

Diagnosis and therapy of myasthenia gravis with antibodies to muscle-specific kinase

Myasthenia gravis (MG) with antibodies to the muscle-specific receptor tyrosine kinase (MuSK-MG) is a rare disease which covers 5-8% of all MG patients. Symptoms are nearly always generalized, though more focal than in MG with anti-acetylcholine receptor antibodies, with predominant involvement of cranial, bulbar and axial muscles; early respiratory crises are frequent. Focal atrophy, mostly of facial, masseter and tongue muscles, occurs in a proportion of patients. Diagnosis is often challenging on account of atypical presentation with little or no symptom fluctuations, lack of response to acetylcholinesterase inhibitors in a high proportion of patients and negative results of electrodiagnostic studies when performed on limb muscles. Immunosuppression is the mainstay of treatment, since the response to acetylcholinesterase inhibitors is generally unsatisfactory and thymectomy does not appear to improve the course of the disease. Although corticosteroids result in marked improvement, disease flares are frequent during prednisone dosage tapering and most patients remain dependent on treatment. Since treatment with rituximab, in uncontrolled studies, induced sustained benefit in patients with refractory disease, B cell depletion is an attractive option for MuSK-MG patients unresponsive to conventional immunosuppressants.

Intravenous Immunoglobulin and Mycophenolate Mofetil for Long-Standing Sensory Neuronopathy in Sjögren's Syndrome

Sensory neuronopathy is described in association with the Sjögren's syndrome (SS). We studied a 55-year-old woman with a 4-year history of progressive asymmetric numbness, distal tingling, and burning sensation in upper and lower limbs. In a few months, she developed ataxia with increased hypoanaesthesia. Electrodiagnostic tests revealed undetectable distal and proximal sensory nerve action potential in upper and lower limbs. Cervical spine magnetic resonance showed a signal hyperintensity of posterior columns. Previous treatment with high-dose glucocorticoids and azathioprine was ineffective. A combined treatment with intravenous immunoglobulin and mycophenolate mofetil was followed by a progressive and persistent improvement. This case documented the efficacy and the safety of the coadministration of intravenous immunoglobulin and mycophenolate mofetil in sensory neuronopathy associated with SS refractory to conventional immunosuppressive therapy.

Impact of intravenous immunoglobulin on the dopaminergic system and immune response in the acute MPTP mouse model of Parkinson's disease

Intravenous immunoglobulin (IVIg) is a blood-derived product, used for the treatment of immunodeficiency and autoimmune diseases. Since a range of immunotherapies have recently been proposed as a therapeutic strategy for Parkinson’s disease (PD), we investigated the effects of an IVIg treatment in a neurotoxin-induced animal model of PD. Mice received four injections of MPTP (15 mg/kg) at 2-hour intervals followed by a 14-day IVIg treatment, which induced key immune-related changes such as increased regulatory T-cell population and decreased CD4⁺/CD8⁺ ratio. The MPTP treatment induced significant 80% and 84% decreases of striatal dopamine concentrations (P < 0.01), as well as 33% and 40% reductions in the number of nigral dopaminergic neurons (P < 0.001) in controls and IVIg-treated mice, respectively. Two-way analyses of variance further revealed lower striatal tyrosine hydroxylase protein levels, striatal homovanillic acid concentrations and nigral dopaminergic neurons (P < 0.05) in IVIg-treated animals. Collectively, our results fail to support a neurorestorative effect of IVIg on the nigrostriatal system in the MPTP-treated mice and even suggest a trend toward a detrimental effect of IVIg on the dopaminergic system. These preclinical data underscore the need to proceed with caution before initiating clinical trials of IVIg in PD patients.

How immune complexes from certain IgG NAbs and any F(ab')₂ can mediate excessive complement activation

In sepsis death follows an excessive inflammatory response involving cytokines and complement that is activated primarily via the amplifying C3/C5 convertase. Excessive stimulation of complement amplification requires IgG-containing or F(ab')₂-containing immune complexes (IC) that capture dimeric C3b on one of their heavy chains or heavy chain fragments. The ability of IgG-IC to capture dimeric C3b by the Fab portion is dependent on an affinity for C3 within the Fab portion, but outside the antigen-binding region. This property is rare among IgG NAbs. In contrast to this, the lack of the Fc portion renders the Fab regions of any F(ab')(2)-IC accessible to nascent C3b, but dimeric C3b deposits only if F(ab')₂-IC form secondary IC with anti-hinge NAbs that rigidify the complex and thereby promote deposition of dimeric C3b. Both types of complexes, C3b₂-IgG-IC and C3b₂-F(ab')₂-IC/anti-hinge NAbs, are potent precursors of alternative C3 convertases and stimulate complement amplification along with properdin up to 750 times more effectively than C3b and properdin. F(ab')₂ fragments are not normally generated, but are formed from NAbs by enzymes from pathogens and neutrophils in sepsis. Unlike IgG-IC F(ab')₂-IC are not cleared by Fc-receptor dependent processes and circulate long enough to form secondary IC with anti-hinge NAbs that rigidify the complexes such that they capture dimeric C3b and gain the potency to stimulate complement amplification.

[Intravenous immunoglobulin: immunomodulatory key of the immune system]

The mechanisms of action of intravenous immunoglobulins (IVIG) are complex and mostly reproduce those of the natural immunoglobulin G (IgG) in our organism. The therapeutic doses used range from substitutive (200-400mg/kg of body weight) in immunodeficiencies to high doses (1-2g/kg of body weight) in autoimmune or inflammatory diseases. The paradoxical pro- or anti-inflammatory effects of IVIG are based on the modulation of the expression of activating versus inhibitory Fc receptors, the type and stage of maturation of the target cell. This huge diversity of actions may explain the extensive and varied range of clinical applications of IVIG nowadays (immunodeficiencies, autoimmune diseases, degenerative diseases such as Alzheimer's, and cancer). On the other hand, biological therapies with monoclonal antibodies mostly consist of IgG molecules with unique antigen specificity, and currently represent a therapeutic field expanding in various pathologies including cancer and diseases of immunological basis. The effects of IgG are added to their specific effects on molecules target.

Cutting edge: intravenous Ig inhibits invariant NKT cell-mediated allergic airway inflammation through FcγRIIIA-dependent mechanisms

Despite their increasing use in autoimmune, inflammatory, and allergic conditions, the mechanism of action of i.v. Igs (IVIg) is poorly understood. On the basis of the critical role of invariant NKT (iNKT) cells in allergic airway inflammation (AAI) and their constitutive expression of the low-affinity IgG receptor FcγRIIIA, we surmised that IVIg targets iNKT cells to exert their anti-inflammatory effect. We found that IVIg treatment significantly inhibited AAI in OVA-sensitized C57BL/6 mice and downregulated α-galactosylceramide-induced iNKT cell activation and cytokine production. Allergic responses were restored in iNKT cell-deficient mice by transferring iNKT cells from PBS- but not from IVIg-treated mice, suggesting that IVIg acts directly on activated iNKT cells that have a critical role in AAI. The inhibitory effects of IVIg on both iNKT cell activation/function and OVA-driven AAI were lost in FcγRIIIA(-/-) mice. Our data unravel an FcγRIIIA-dependent inhibitory effect of IVIg on activated iNKT cells that confers protection in AAI.

Treatment with polyclonal immunoglobulin during T-cell reconstitution promotes naive T-cell proliferation

Natural antibodies are unique self molecules endowed with both suppressive and activating functions on various cells of the immune system and are recognized as a fundamental link between the adaptive and innate immune system. Here, we examine the role of natural antibodies, using polyclonal immunoglobulins (Ig), as a promoter of T-cell reconstitution in a context of lymphopenia. We have established a mouse model to mimic immunologic recovery in adult patients with severe hypothymic function subjected to autologous hematopoietic precursor cell transplantation. Thymectomized mice were transplanted and treated with low doses of Ig or its Fab or Fc fragments. The animals displayed, during early phases of Ig treatment, a significant increase of T-cell reconstitution displaying a naive CD4(+) phenotype. In addition, the Ig-treated animals exhibited an increase dilution of single-joint T-cell receptor excision circles (sjTRECs) in peripheral blood, suggesting an early increase in proliferation of T cells stimulated by the natural antibodies. These results unveil a novel and considerable effect of intravenous Ig treatment in situations of severe lymphopenia as a stimulator of proliferation of peripheral naive T cells, possibly protecting diverse immune repertoires.

Prevention of excessive collagen accumulation by human intravenous immunoglobulin treatment in a murine model of bleomycin-induced scleroderma

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrotic changes in skin and other organs involving excessive collagen deposition. Here we investigated the effect of intravenous immunoglobulin (IVIG) on fibrosis in a murine model of bleomycin (BLM)-induced scleroderma. Scleroderma was induced in C3H/He J mice by subcutaneous BLM injections daily for 35 days. The collagen content in skin samples from the BLM-injected group (6·30 ± 0·11 mg/g tissue) was significantly higher than the PBS group (5·80 ± 0·10 mg/g tissue), and corresponded with dermal thickening at the injection site. In contrast, mice treated with IVIG for 5 consecutive days after initiating BLM injection showed lesser collagen content significantly (IVIG group, 5·61 ± 0·09 mg/g tissue; BLM vs. IVIG). In order to investigate the cellular and protein characteristics in the early stage of the model, the skin samples were obtained 7 days after the onset of experiment. Macrophage infiltration to the dermis, monocyte chemoattractant protein (MCP-1)-positive cells, and increased TGF-β1 mRNA expression were also observed in the BLM group. IVIG inhibited these early fibrogenic changes; MCP-1 expression was significantly lesser for the IVIG group (1·52 ± 0·19 pg/mg tissue) than for the BLM group (2·49 ± 0·26 pg/mg tissue). In contrast, TGF-β1 mRNA expression was significantly inhibited by IVIG. These results suggest that IVIG treatment may inhibit macrophage recruitment to fibrotic sites by down regulating MCP-1 and TGF-β production, and thus could be a potential drug for managing fibrotic disorders such as SSc.

Cell death modulation by intravenous immunoglobulin

The induction of cell death in immune cells by naturally occurring antibodies specific for death receptors may present an important antiinflammatory mechanism of intravenous immunoglobulin (IVIG). Conversely, the protection of tissue cells from death receptor-mediated apoptosis by blocking antibodies is thought to contribute to the beneficial effects of IVIG in certain inflammatory disorders such as toxic epidermal necrolysis, also known as Lyell's syndrome. In this review, we focus on recent insights into the role of functional antibodies against Fas, sialic acid-binding immunoglobulin-like lectin (Siglec)-8, and Siglec-9 receptors in IVIG-mediated cell survival or death effects. In addition, we examine a variety of factors in inflammatory disease that may interplay with these cellular events and influence the therapeutic efficacy or potency of IVIG. These involve activation status of the target cell, cytokine microenvironment, pathogenesis and stage of disease, individual genetic determinants, species characteristics, and batch-to-batch variations of IVIG preparations.

Immunological origin and functional properties of catalytic autoantibodies to amyloid beta peptide

OBJECTIVES

Objectives The objectives of this study are to (1) evaluate the ability of the immune system to synthesize specific antibodies that catalyze the degradation of amyloid beta peptide (Abeta) and to (2) evaluate the prospect of developing a catalytic IVIG (CIVIG) formulation for therapy of Alzheimer's disease (AD).

CONCLUSIONS

Polyclonal autoantibodies from humans without dementia hydrolyzed Abeta specifically. The catalytic activity improved as a function of age. Patients with AD produced catalytic antibodies at increased levels. IgM-class antibodies expressed the activity at levels superior to IgGs. Production of catalytic autoantibodies appears to be an innate immunity function with adaptive improvements occurring upon Abeta overexpression, which suggests a beneficial function of the catalytic activity. The catalytic autoantibodies impeded Abeta aggregation, dissolved preformed Abeta aggregates, and inhibited Abeta cytotoxicity in tissue culture. Recombinant catalytic antibodies from a human library have been identified, validating the phenomenon of antibody-catalyzed Abeta cleavage. As a single catalyst molecule inactivates multiple Abeta molecules, catalytic antibodies may clear Abeta efficiently. IVIG did not cleave Abeta, indicating the importance of purification procedures that maintain catalytic site integrity. Traditional Abeta-binding antibodies form immune complexes that can induce inflammatory reaction and vascular dysfunction. Catalysts do not form stable immune complexes, minimizing these risks. Criteria appropriate for developing a CIVIG formulation with potential therapeutic utility are discussed, including isolation of the Abeta-specific catalytic subsets present in IgM and IgG from human blood.

Efficacy of intravenous immunoglobulin (IVIG) affinity-purified anti-desmoglein anti-idiotypic antibodies in the treatment of an experimental model of pemphigus vulgaris

Pemphigus vulgaris is a rare life-threatening autoimmune bullous disease caused by immunoglobulin G (IgG) autoantibodies directed against desmogleins 1 and 3. Previously, we showed that intravenous immunoglobulin (IVIG) ameliorates anti-desmoglein-induced experimental pemphigus vulgaris in newborn naive mice. The aim of this study was to examine the efficacy of anti-anti-desmoglein-specific IVIG in a similar model. Pemphigus-vulgaris-specific IVIG (PV-sIVIG) was affinity-purified from IVIG on a column of single-chain variable fragment (scFv) anti-desmogleins 1 and 3. The anti-idiotypic activity of PV-sIVIG was confirmed by enzyme-linked immunosorbent assay, inhibition assay. After induction of pemphigus by injection of anti-desmogleins 1 and 3 scFv to newborn mice, the animals were treated with PV-sIVIG, IVIG (low or high dose) or IgG from a healthy donor (n = 10 each). The skin was examined 24-48 h later, and samples of affected areas were analysed by histology and immunofluorescence. In vitro study showed that PV-sIVIG significantly inhibited anti-desmogleins 1 and 3 scFv binding to recombinant desmoglein-3 in a dose-dependent manner. Specificity was confirmed by inhibition assay. In vivo analysis revealed cutaneous lesions of pemphigus vulgaris in mice injected with normal IgG (nine of 10 mice) or low-dose IVIG (nine of 10 mice), but not in mice treated with PV-sIVIG (none of 10) or high-dose IVIG (none of 10). On immunopathological study, PV-sIVIG and regular IVIG prevented the formation of acantholysis and deposition of IgG in intercellular spaces. In conclusion, the PV-sIVIG preparation is more effective than native IVIG in inhibiting anti-desmoglein-induced pemphigus vulgaris in mice and might serve as a future therapy in patients with the clinical disease.

Subcutaneous immunoglobulin in polymyositis and dermatomyositis: a novel application

OBJECTIVES

To describe the feasibility and safety of subcutaneous immunoglobulin (SCIg) in polymyositis (PM) and dermatomyositis (DM).

METHODS

Since 2009, we used SCIg to treat patients with severe idiopathic myositis (4 with DM, 3 with PM), diagnosed according to the Bohan and Peter's criteria. SCIg (Vivaglobin®; CSL Behring) was administered by a programmable pump at the patient's usual IVIg monthly dose fractioned into equal doses given subcutaneously at weekly intervals. A standardized protocol was used to evaluate patients and to assess disease activity, treatment response and quality of life.

RESULTS

Seven female patients were studied. All were Caucasians, with a median age of 53 years and a median disease duration of 72 months. The median follow-up period was 14±4 months. During treatment period, no relapse of the disease occurred. All patients showed a favourable clinical response and reported a good tolerance to the treatment with an improved quality of life. CK serum levels decreased over time with a concomitant improvement in MRC and Rankin modified scores. Three patients were able to discontinue the immunosuppressant and all to reduce the daily maintenance prednisone dose.

CONCLUSIONS

Our experience demonstrates the beneficial effect and the safety of SCIg administration in active and refractory inflammatory myopathies.

Intravenous immunoglobulin increases survival time in the acute phase of experimental Chagas disease

Chagas disease induced by Trypanosoma cruzi (Tc) infection is an important cause of mortality and morbidity affecting the cardiovascular system for which presently available therapies are insufficient and largely inadequate. Intravenous immunoglobulin (IVIg) is a therapeutic preparation containing normal polyspecific IgG obtained from plasma pools of several thousand healthy donors and is used in several autoimmune, inflammatory and infectious diseases. In the study of heart from mice chronically infected with Tc, we observed that IVIg restores type 1 atrioventricular block or bradycardia. In the present study, we investigated the effects of IVIg in acute Tc infection. Intravenous immunoglobulin administration after the first week of infection was associated with an increase in survival time. Taken together, results observed in the chronic and in the acute phase associate IVIg treatment with a favourable outcome in T. cruzi infection.

Intravenous immunoglobulin in recurrent-relapsing inflammatory optic neuropathy

OBJECTIVE

Recurrent-relapsing inflammatory optic neuropathy, including chronic relapsing inflammatory and autoimmune optic neuropathies, is rare, but can cause severe visual loss. Long-term steroids may preserve vision, yet side effects are frequent. We describe our experience with intravenous immunoglobulins (IVIg).

DESIGN

A semi-prospective case series from 4 medical centres.

PARTICIPANTS

Patients with steroid responsive recurrent-relapsing optic neuropathy.

METHODS

Semiprospective case series of IVIg treatment in steroid-responsive recurrent-relapsing optic neuropathy at 4 medical centres. Outcome measures included visual outcome; time to, and duration of, remission; duration of corticosteroid use; and adverse events.

RESULTS

Vision stabilized in all 6 patients treated with IVIg without steroids for extended periods of time. None improved and none worsened. One adverse event occurred during an IVIg infusion after 3 uneventful years of IVIg maintenance. Average steroid use prior to IVIg was 12 months. After IVIg treatment, 5/6 patients no longer required corticosteroids. Two patients experienced late relapses on IVIg, one of whom was treated with cyclosporine, the other with steroids.

CONCLUSIONS

IVIg can be considered an effective steroid-sparing agent in selected cases with steroid-dependent recurrent-relapsing autoimmune optic neuropathy.

Trypanosoma cruzi calreticulin: a novel virulence factor that binds complement C1 on the parasite surface and promotes infectivity

In Trypanosoma cruzi, calreticulin (TcCRT) translocates from the endoplasmic reticulum (ER) to the area of flagellum emergence. We propose herein that the parasite uses this molecule to capture complement C1, in an infective apoptotic mimicry strategy. Thus, TcCRT/C1 interactions, besides inhibiting the classical pathway of complement activation as previously shown in our laboratories, will also promote infectivity. This fact correlates with significant increases in TcCRT mRNA levels during early infection stages of a VERO cell line. In vitro, the collagenous and globular C1q domains simultaneously bind TcCRT and antigen aggregated Igs, respectively. Accordingly, mouse immunizations with TcCRT induced humoral responses that, after challenge, correlated with increased parasitemia. Thus, on the parasite surface, whole Igs anti-TcCRT promote C1 deposits on trypomastigotes while, as expected, F(ab')₂ fragments decrease it. Likewise, pretreatment of the parasites with whole anti-TcCRT antibodies augmented parasitemia and mortality in mice. In contrast, pretreatment with F(ab')₂ fragments anti-TcCRT, devoid of their capacity to provide additional C1q binding sites, was protective. Most important, while pretreatment of trypomastigotes with C1q increased infectivity in the RAW murine cell line, as well as mice mortality and parasitemia, the F(ab')₂ fragments significantly interfered with the C1q-dependent infectivity. Differently from other surface molecules involved in infectivity, TcCRT uses C1 as an adaptor molecule to recognize host cells. As expected, since TcCRT is one of several cell surface parasite molecules participating in infectivity, attempts to interfere with the C1/TcCRT interactions with F(ab')₂ fragments, were moderately but significantly effective, both in vitro and in vivo.

Information for healthcare providers on general features of IGIV with emphasis on differences between commercially available products

OBJECTIVE

Intravenous immunoglobulin (IGIV) has provided an essential replacement therapy for primary and secondary immunodeficiencies patients and prophylaxis of infectious diseases in them. It is also used in several autoimmune and chronic inflammatory disorders. An overview of IGIV with information on several commercially available IGIV products is discussed.

DATA SOURCES

Medline databases and literature provided by the manufacturer for each product presented in the manuscript.

STUDY SELECTION

From the vast body of information on IGIV, only those studies were selected that were pertinent to general features of IGIV (as presented below) or information provided by the manufacturer that facilitated comparing one product to the other.

DATA EXTRACTION

Data was extracted on production, and purification procedures, removal of infectious agents, physical and biochemical properties and issues of safety. Data was extracted only for products available in the US.

DATA SYNTHESIS

IGIV is prepared using pooled plasma. The purification of IGIV is a complex and multi-step process. There is a reciprocal relationship between the purity of IgG in the product and the recovery rate from the total plasma. It is quite possible that some of the biological mediators of the inflammatory and immune systems may be present in trace amounts. Screening and removal of blood borne pathogens is necessary and there are several different techniques available. The specifics of the administration are often variable and no consistent pattern or protocol has been used. When limited dosages are required IGIV may be administered subcutaneously. The side effects associated with IGIV are usually mild and self-limiting.

CONCLUSION

There are differences in products produced by different manufacturers. The current data does not provide sufficient detail or information to be able to make specific recommendations for the use of a given commercial preparation in a specific disease state. The use of IGIV is associated with certain common and uncommon side effects. The identification of risk factors that might predispose a patient to developing them have been studied and reported. In choosing a IGIV preparation the user may avoid features that may predispose to certain side effects. Equally important is monitoring of patients during and after the IGIV therapy.

Non-ST Elevation Myocardial Infraction after High Dose Intravenous Immunoglobulin Infusion

Intravenous immunoglobulins (IVIgs) are used for several indications, including autoimmune conditions. IVIg treatment is associated with several possible adverse reactions including induction of a hypercoagulable state. We report a 76-year-old woman treated with IVIg for myasthenia gravis, which developed chest pain and weakness following IVIg infusion. The symptoms were associated with ST segment depression in V4–6 and elevated troponin levels. The patient was diagnosed with non-ST elevation myocardial infarction (NSTEMI). The patient had no significant risk factor besides age and a cardiac perfusion scan was interpreted as normal (the patient refused to undergo cardiac catheterization). This case is compatible with IVIg-induced hypercoagulability resulting in NSTEMI. Cardiac evaluation should therefore be considered prior to initiation of IVIg treatment especially in patients with multiple cardiovascular risks.