Hepatitis A virus antibodies in immunoglobulin preparations

Clinical false positives resulting from recent intravenous immunoglobulin therapy: case report

Background

Many clinicians are aware that certain therapies administered to their patients can have downstream consequences in the form of clinical laboratory test interferences. This is particularly true of laboratory tests that depend on, or directly involve the use of, antibody-based methodology. Intravenously-administered immunoglobulin therapy is one such treatment that can in theory directly impact the results of particular tests in the area of viral serology. This study can help serve as a reference for clinicians researching the impact of intravenously-administered immunoglobulin therapy in the context of positive results that do not reflect the clinical background of the patient.

Case presentation

We describe a case whereby an intravenously-administered immunoglobulin therapy led to a series of clinical false positives in viral serology, inconsistent with the known patient history as well as recent laboratory results. The patient presented to hospital with petechiae-type bleeding rashes and was investigated for thrombocytopenia after initial blood investigations indicated very low platelets.

Subsequent testing of the potential causes for low-platelet involved several viral serology investigations, including hepatitis, cytomegalovirus and human immunodeficiency virus. Initial testing indicated patient exhibited negative status for all viral antibodies and antigens (except immunity for hepatitis B surface antigen antibody).

As part of the thrombocytopenia treatment, intravenously-administered immunoglobulin therapy was administered, and subsequent viral serology was ordered. These investigations indicated a positive status for several hepatitis antibodies as well as cytomegalovirus.

Conclusions

This case study illustrates the potential for improper diagnosis of previous or ongoing infection status in patients administered IVIg therapy. Caution should be exercised particularly when interpreting results involving cytomegalovirus and hepatitis.

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.

Intravenous Immunoglobulins at the Crossroad of Autoimmunity and Viral Infections

Intravenous immunoglobulins (IVIG) are blood preparations pooled from the plasma of donors that have been first employed as replacement therapy in immunodeficiency. IVIG interact at multiple levels with the different components of the immune system and exert their activity against infections. Passive immunotherapy includes convalescent plasma from subjects who have recovered from infection, hyperimmune globulin formulations with a high titer of neutralizing antibodies, and monoclonal antibodies (mAbs). IVIG are used for the prevention and treatment of several infections, especially in immunocompromised patients, or in case of a poorly responsive immune system. The evolution of IVIG from a source of passive immunity to a powerful immunomodulatory/anti-inflammatory agent results in extensive applications in autoimmune diseases. IVIG composition depends on the antibodies of the donor population and the alterations of protein structure due to the processing of plasma. The anti-viral and anti-inflammatory activity of IVIG has led us to think that they may represent a useful therapeutic tool even in COVID-19. The human origin of IVIG carries specific criticalities including risks of blood products, supply, and elevated costs. IVIG can be useful in critically ill patients, as well as early empirical treatment. To date, the need for further well-designed studies stating protocols and the efficacy/tolerability profile of IVIG and convalescent plasma in selected situations are awaited.

Development of an Orally Bioavailable Isoliquiritigenin Self-Nanoemulsifying Drug Delivery System to Effectively Treat Ovalbumin-Induced Asthma

Purpose

Isoliquiritigenin (ILQ), an important component of Anti-Asthma Herbal Medicine Intervention (ASHMI), had shown potent anti-asthma effect in vitro in our previous study. However, poor solubility and low bioavailability hindered in vivo application to treat asthma. This study was to develop a novel ILQ loaded self-nanoemulsifying drug delivery system (ILQ-SMEDDS) with enhanced bioavailability.

Methods

The optimized SMEDDS formulation was composed of ethyl oleate (oil phase), Tween 80 (surfactant) and PEG400 (co-surfactant) at a mass ratio of 3:6:1. The physiochemical properties of ILQ-SMEDDS, including drug content, globule size, zeta potential, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, were characterized. And the in vitro release profile, in situ intestinal absorption, in vivo pharmacokinetic parameters and the anti-asthma effect of ILQ suspension and ILQ-SMEDDS were evaluated.

Results

The ILQ-SMEDDS had an average globule size of 20.63 ± 1.95 nm with a polydispersity index (PDI) of 0.11 ± 0.03, and its zeta potential was −12.64 ± 2.12 mV. The cumulative release rate of ILQ from ILQ-SMEDDS to the simulated gastrointestinal tract was significantly higher than that of free ILQ suspension. And area under curve with ILQ-SMEDDS was found to be 3.95 times higher than that of ILQ suspension indicating improved bioavailability by SMEDDS. Although ILQ-SMEDDS showed a slight less effective inhibitory effect on eotaxin-1 in human lung fibroblast (HFL-1) cells than free ILQ, in an ovalbumin-induced asthma model, ILQ-SMEDDS exhibited more efficacy than ILQ suspension in improving asthma-associated inflammation, including eosinophil production, ovalbumin-specific immunoglobulin E (OVA-sIgE), interleukin 4 (IL 4), interleukin 5 (IL 5) and interferon-γ (IFN-γ). Even the low dose of ILQ-SMEDDS group (10 mg/kg) showed better anti-asthma effect than that of the ILQ suspension group (20 mg/kg).

Conclusion

Compared with ILQ suspension, ILQ-SMEDDS showed significantly improved bioavailability and anti-asthma effect, revealing its potential as a favorable pharmaceutical agent for treating asthma.

Plasma Donors in the Southwestern United States Positively Contribute to the Diverse Therapeutic Antibody Profile of Immune Globulin Products

Human-plasma-derived immune globulin (IG) is used in augmentation therapy to provide protective levels of antibodies to patients with primary immune deficiency diseases (PIDD) and for prophylaxis against infectious diseases. To maintain the breadth of antibodies necessary for clinical protection, it is important to understand regional patterns of antibody seroprevalence in source plasma from which IG products are manufactured. In this study, source plasma from donation centers in various locations of the Southwestern quarter of the United States was surveyed for antibody titers to hepatitis A virus (HAV), measles virus (MeV), and cytomegalovirus (CMV). A broad range of anti-HAV Ig plasma titers was observed among these centers, with some centers exhibiting 3-5 times the titers of the others. Minor to no differences were observed for levels of anti-MeV and anti-CMV, respectively. Importantly, elevated anti-HAV Ig titers were broadly observed across plasma units obtained from the centers exhibiting high titers, indicative of a potential regional phenomenon among donors as opposed to few donors with singularly high titers. Plasma from these high-titer centers conferred significantly greater neutralization against HAV in vitro. The outcomes of this study give a glimpse of the antibody diversity inherent in human plasma used to manufacture IG products..

High level antibodies to TORCH in the IVIG preparation from Taiwanese

BACKGROUND

Congenital TORCH (toxoplasmosis, other viruses [varicella-zoster virus, VZV, etc.], rubella, cytomegalovirus [CMV], Herpes simplex virus [HSV]) infections are major causes of prenatal, perinatal, and postnatal morbidity and mortality. Although treatment or prevention strategies are available for these pathogens, all drugs may not be safe during the pregnancy. The aim of this study is to measure the antibodies (Abs) concentration in the intravenous immunoglobulin (IVIG) preparation to evaluate the therapeutic potential for TORCH infection.

METHODS

We tested the only one commercial IVIG preparation from Taiwanese for the presence of Abs against Toxoplasma gondii, VZV, Epstein-Barr virus (EBV), measles, mumps, rubella, CMV, HSV type 1 (HSV-1), and HSV type 2 (HSV-2) by using enzyme-linked immunosorbent assay or chemiluminescent microparticle immunoassay.

RESULTS

In our study, the median level (range) of anti-CMV immunoglobulin G (IgG) is > 250 (All > 250) (arbitrary unit, AU)/mL, anti-EBV > 200 (All > 200) (relative unit, RU)/mL, anti-HSV > 200 (152.75 to >200) RU/mL, anti-VZV > 5000 (All > 5000) IU/L, anti-measles > 5000 (All > 5000) IU/L, anti-mumps > 200 (156.5 to > 200) RU/mL, anti-rubella 209.8 IU/mL (192.7 to 238.5), and anti-Toxoplasma is 14.05 (12.3 to 16) IU/mL. There was not any immunoglobulin M (IgM) against HSV, VZV, mumps, measles, rubella, CMV, EBV, and Toxoplasma in the "Taiwan Blood Services Foundation" IVIG preparations.

CONCLUSION

There was high activity against T. gondii, VZV, EBV, measles, mumps, rubella, CMV, HSV-1, and HSV-2 in all IVIG batches. Further investigation is warranted to confirm the efficacy of IVIG from Taiwanese for congenital TORCH infections.

Immunoglobulins and virus antibody titers: of past needs, current requirements, and future options

BACKGROUND

Immunoglobulins (Igs) have been in clinical use for almost 70 years, and early on were also used in conjunction with exposure to the measles virus or polio virus. The US regulations that describe functional Ig lot release thus require the demonstration of minimum antibody titers against these two viruses, although the use of vaccines has now dramatically reduced their incidence. The lower clinical importance of these viruses raises the question of whether other virus antibodies might be more informative for patients with immunodeficiency.

STUDY DESIGN AND METHODS

A literature survey was conducted to identify viruses of potential clinical concern for people with immunodeficiency. The viruses selected have stable seroepidemiology and associated functional antibody assays. As a result, neutralizing antibody titers to human adenovirus 5 (HAdV5), respiratory syncytial virus (RSV) serotypes A and B, and human parainfluenza virus 3 (hPIV3) were determined in Ig lots produced from plasma collected in either the United States or the European Union.

RESULTS

The virus antibody titers measured were high and consistent among the Ig lots tested. Use of either US- or EU-derived plasma as starting material resulted in equivalent virus antibody titers, with the exception of RSV serotype B, for which a lower titer was seen in EU plasma-derived Ig lots.

CONCLUSION

With the significant decline in measles virus and polio virus circulation, and even their potential eradication, measurement of antibody titers against other viruses in Ig products may be more informative for functional lot release testing.

Antibodies to vaccine antigens in pooled polyclonal human IgG products

Immune-deficient patients depend on the antibodies in pooled human immunoglobulin G (IgG) preparations to remain free from serious infections. The potency of IgG preparations is therefore an ongoing concern. The use of pooled IgG to prevent infection is based on the concept that healthy adults have recovered from infections earlier in life and maintain relatively high antibody titers. In general, vaccine-induced immunity is less robust or long-lasting than immunity after natural infection, and many infectious diseases which were formerly widely prevalent have become much less common due to improved hygiene and vaccines. This raises questions as to the adequacy of protective antibodies in current IgG preparations. This paper reviews available data on antibodies against selected bacterial and virus vaccine antigens in current IgG products. Most products contain sufficient antibody to yield levels above minimal protective concentrations to a broad range of pathogens and toxins. Illustrative examples of effects of vaccines on antibody content of IgG products are also discussed: antibody titers to hepatitis A virus in donor plasma pools in both the US and EU are dropping due to decreased natural infection, but they are still sufficient to provide robust protection. Increasing seroprevalence of hepatitis B virus as a result of immunization suggests that antibody titers against this virus may actually be increasing. Finally, serial studies suggest that pooled IgG provides protection against seasonal influenza viruses despite year-to-year antigenic drift, and is also likely to provide at least some protective antibody against potentially pandemic strains.

Effectiveness of hepatitis A vaccination as post-exposure prophylaxis

Hepatitis A (HA) has been a vaccine-preventable disease since 1995. In Catalonia, a universal combined hepatitis A+B vaccination program of preadolescents was initiated at the end of 1998. However, outbreaks are reported each year and post-exposure prophylaxis (PEP) with hepatitis A virus (HAV) vaccine or immunoglobulin (IG) is recommended to avoid cases. The aim of this study was to assess the effectiveness of HAV vaccine and IG in preventing hepatitis A cases in susceptible exposed people. A retrospective cohort study of contacts of HA cases involved in outbreaks reported in Catalonia between January 2006 and December 2012 was made. The rate ratios and 95% confidence intervals (CI) of HA in susceptible contacts receiving HAV or IG versus those without PEP were calculated. There were 3550 exposed persons in the outbreaks studied: 2381 received one dose of HAV vaccine (Hepatitis A or hepatitis A+B), 190 received IG, and 611 received no PEP. 368 exposed subjects received one dose of HAV vaccine and IG simultaneously and were excluded from the study. The effectiveness of PEP was 97.6% (95% CI 96.2-98.6) for HAV vaccine and 98.3% (95% CI 91.3-99.9) for IG; the differences were not statistically significant (p = 0.36). The elevated effectiveness of HAV vaccination for PEP in HA outbreaks, similar to that of IG, and the long-term protection of active immunization, supports the preferential use of vaccination to avoid secondary cases.

Antibodies against Hepatitis A and Hepatitis B Virus in Intravenous Immunoglobulin Products

The worldwide seroprevalence of hepatitis A virus (HAV) and hepatitis B virus (HBV) has changed over the last two decades, indicating a declining incidence of HAV and HBV infections. Therefore, vaccinations against HAV and HBV are recommended for unimmunized people before traveling to an endemic area. Unfortunately, primary antibody deficiency (PAD) patients can only obtain humoral immunity through intravenous immunoglobulin G (IVIG) replacement and not from vaccination because of a defect in antibody production. However, few studies have analyzed the titers of antibodies against HAV or HBV in IVIG products. In this study, the titers of anti-HAV and anti-HBs antibodies were measured in nineteen lots of IVIG products from five manufacturers from three countries (A, B from Korea; C, D from Japan; and E from the USA), and trough titers in plasma were estimated. Concentrations of anti-HAV antibody ranged from 1,888-8,927 mIU/mL and estimated trough titers exceeded the minimal protective value in all evaluated IVIG products. Concentrations of anti-HBs antibody ranged from 438-965 mIU/mL in products A and B and were 157, 123, and 1,945 mIU/mL in products C, D, and E, respectively. Estimated trough titers in products A, B, and E exceeded the minimal protective value but those in products C and D did not reach this threshold. These data demonstrated that available IVIG products generally provide sufficient antibodies against HAV and HBV to protect patients with PAD, although the trough concentrations of anti-HBs antibody in two IVIG products did not reach the minimum protective value.

Ebola virus convalescent blood products: where we are now and where we may need to go

The world is regularly exposed to emerging infections with the potential to burst into a pandemic. One possible way to treat patients, when no other treatment is yet developed, is passive immunization performed by transfusing blood, plasma or plasma immunoglobulin fractions obtained from convalescent donors who have recovered from the disease and have developed protective antibodies. The most recent on-going epidemic is caused by the Ebola virus, a filovirus responsible for Ebola virus disease, a severe, often lethal, hemorrhagic fever. Recently, the use of convalescent blood products was proposed by the WHO as one early option for treating patients with Ebola virus disease. This publication provides an overview of the various convalescent blood products and technological options that could theoretically be considered when there is a need to rely on this therapeutic approach. In countries without access to advanced blood-processing technologies, the choice may initially be restricted to convalescent whole blood or plasma. In technologically advanced countries, additional options for convalescent blood products are available, including virally inactivated plasma and fractionated immunoglobulins. The preparation of minipool immunoglobulins is also a realistic option to consider.

Antibody levels to tetanus, diphtheria, measles and varicella in patients with primary immunodeficiency undergoing intravenous immunoglobulin therapy: a prospective study

BACKGROUND

Patients with antibody deficiencies depend on the presence of a variety of antibody specificities in intravenous immunoglobulin (IVIG) to ensure continued protection against pathogens. Few studies have examined levels of antibodies to specific pathogens in IVIG preparations and little is known about the specific antibody levels in patients under regular IVIG treatment. The current study determined the range of antibodies to tetanus, diphtheria, measles and varicella in IVIG products and the levels of these antibodies in patients undergoing IVIG treatment.

METHODS

We selected 21 patients with primary antibody deficiencies who were receiving regular therapy with IVIG. Over a period of one year, we collected four blood samples from each patient (every 3 months), immediately before immunoglobulin infusion. We also collected samples from the IVIG preparation the patients received the month prior to blood collection. Antibody levels to tetanus, diphtheria, measles and varicella virus were measured in plasma and IVIG samples. Total IgG levels were determined in plasma samples.

RESULTS

Antibody levels to tetanus, diphtheria, varicella virus and measles showed considerable variation in different IVIG lots, but they were similar when compared between commercial preparations. All patients presented with protective levels of antibodies specific for tetanus, measles and varicella. Some patients had suboptimal diphtheria antibody levels. There was a significant correlation between serum and IVIG antibodies to all pathogens, except tetanus. There was a significant correlation between diphtheria and varicella antibodies with total IgG levels, but there was no significant correlation with antibodies to tetanus or measles.

CONCLUSIONS

The study confirmed the variation in specific antibody levels between batches of the same brand of IVIG. Apart from the most common infections to which these patients are susceptible, health care providers must be aware of other vaccine preventable diseases, which still exist globally.

Analyzing titers of antibodies against bacterial and viral antigens, and bacterial toxoids in the intravenous immunoglobulins utilized in Taiwan

Intravenous immunoglobulin (IVIG) manufactured from human plasma contains IgG as the primary ingredient, and is used for indications such as immunodeficiency syndrome. Available IVIGs in Taiwan are either manufactured from Taiwanese or North American plasma. The effectiveness of the national immunization program of Taiwan can be evaluated by analyzing and comparing IVIG antibody titers that are induced through the corresponding vaccines (tetanus, diphtheria, and pertussis, measles, rubella, hepatitis A, hepatitis B and varicella). Both enzyme-linked immunosorbent assay (ELISA) and the in vitro neutralization test demonstrated that all IVIGs provide adequate clinical protection against diphtheria and tetanus toxins. ELISA results further revealed that plasma of Taiwanese subjects contains higher levels of pertussis toxin and filamentous hemagglutinin antibodies, when compared to foreign IVIGs. This may be related to the later adoption of acellular pertussis vaccine in Taiwan. Antibodies titers against measles, rubella, hepatitis A, and varicella-zoster virus were otherwise low. Low titers of hepatitis B surface antigen antibodies are present in Taiwanese plasma IVIG, indicating immune memory decline or loss. In conclusion, our results show that Taiwanese IVIG contains varying titers of vaccine-induced antibodies, and serves as a guide for future amendments to Taiwan's immunization program.

Immunoglobulin: production, mechanisms of action and formulations

Human immunoglobulin (Ig) began to be applied in the clinical practice with the treatment of primary immunodeficiencies. Quickly, applications of Ig increased, as its anti-inflammatory and immunomodulatory functions were elucidated. Currently, Ig is the most commonly used blood product. Ig is obtained by processing plasma; methods, in particular, techniques to reduce plasma viral loads have been evolving over the years and include: pasteurization, solvent/ detergent treatment, caprylic acid treatment and nanofiltration. These methods contribute to increased safety and quality of blood products. The mechanisms of action of Ig not only involve the blockade of Fc receptors of phagocytes, but also control complement pathways, idiotype-anti-idiotype dimer formation, blockage of superantigen binding to T cells, inhibition of dendritic cells and stimulation of regulatory T cells (Tregs). There are several formulations of Ig available, each one with its own peculiar characteristics. In Brazil, there is stringent legislation regulating the quality of Ig. Only Ig products that completely fulfill the quality control criteria are released for use. These standards involve different tests from visual inspection to determination of anti-complementary activity. This paper will further review the history and current status of Ig, including its production and mechanisms of action. The formulations available in Brazil and also the criteria of quality control currently applied will be presented.

Virus reduction in an intravenous immunoglobulin by solvent/detergent treatment, ion-exchange chromatography and terminal low pH incubation

Virus reduction by several steps in the manufacturing process for the intravenous immunoglobulin Vigam(®), has been investigated. The solvent/detergent step based on treatment with 0.3% tri-n-butyl phosphate and 1% polysorbate 80 at 37 °C, was confirmed to be effective for a range of enveloped viruses. Virus infectivity was undetectable i.e. >6 log inactivation within 30 min of the standard 6 h process. This was consistent over the range of conditions tested i.e. solvent/detergent and protein concentration, temperature and pH. The ion-exchange chromatography step in the process was also able to remove some viruses. Virus spiked followed by blank column runs confirmed the effectiveness of the sanitisation step for ensuring there was no virus cross contamination between column runs. The terminal low pH incubation step was also able to inactivate enveloped viruses, as well as some non-enveloped viruses. The combination of these three steps ensures a high margin of virus safety for this product.

Tick-borne encephalitis virus-neutralizing antibodies in different immunoglobulin preparations

Patients with primary immunodeficiency (PIDs) depend on the presence of a variety of antibody specificities in intravenous immunoglobulin (IVIG). Using the tick-borne encephalitis virus (TBEV), geographic variability in IVIG antibody content was shown. Care should therefore be exercised when treating PIDs in a given geography, as only locally sourced plasma contains the antibody specificities against the circulating pathogens in the given locality.

Advances in basic and clinical immunology in 2010

Reports in basic and clinical immunology in 2010 reflected the use of state-of-the-art genetic and immunologic tools to characterize the pathogenesis of immunologic diseases and the development of novel therapies directed to these conditions. B-cell biology has been explained in greater detail, significantly with lessons from the genetic defects found in the humoral immunodeficiencies. Therapeutic mAbs are given for an increasing number of indications, such as anti-CD20 antibodies or rituximab, which was initially developed for non-Hodgkin lymphomas and is currently used in diverse autoimmune and inflammatory disorders. The report of an infant with severe combined immunodeficiency (SCID) in Massachusetts detected by means of newborn screening and successfully treated with hematopoietic stem cell transplantation validated recent efforts toward newborn screening for SCID. Improvement of survival outcomes for patients with primary immunodeficiencies treated with hematopoietic stem cell transplantation was demonstrated in a large European cohort, with significant appreciation of the type of donor graft, particularly the use of HLA-matched unrelated donors for patients with non-SCID. Progress in cellular mechanisms of drug hypersensitivity included the characterization of nitroso-modified drug metabolites as potent T-cell activators and the identification of the relocation of plasmacytoid dendritic cells from blood to skin as a potential risk factor for reactivation of viral disease.

Treatment of primary immunodeficiency with Kiovig: a literature review

INTRODUCTION

Primary immunodeficiency disorders are associated with increased patient susceptibility to recurrent infections. Since the 1950s, immunoglobulin products have been administered to treat infections in primary immunodeficiency, and patients often require lifelong therapy. The aim of this study is to carry out a literature review of a ready-to-use 10% liquid immunoglobulin preparation, Kiovig (Baxter, Brussels, Belgium), in the treatment of primary immunodeficiency.

METHODS

Studies were identified by searching PubMed, Centre for Reviews and Dissemination databases, Cochrane Database of Systematic Reviews, and EconLit up to January 2010. The clinical literature review focused on studies of the safety, tolerability, and effectiveness of Kiovig. Evidence about cost-effectiveness was derived from economic evaluations. In addition, budget impact analyses were identified that examined the financial impact of adopting Kiovig for the treatment of primary immunodeficiency.

RESULTS

The evidence indicates that Kiovig and other intravenous immunoglobulin products have similar safety and effectiveness. Given that Kiovig and other intravenous immunoglobulin products appear to have similar effectiveness, the pharmacoeconomic value of Kiovig depends on the costs of immunoglobulin treatment, including drug acquisition costs, and pharmacist and nursing time costs. A Belgian study indicated that the price of Kiovig is the main driver of its budget impact on the treatment of primary immunodeficiency.

CONCLUSION

The current evidence base on the treatment of primary immunodeficiency with Kiovig is limited. Head-to-head comparative studies are called for to investigate the safety, tolerability, effectiveness, and cost-effectiveness of Kiovig versus other immunoglobulin products in the treatment of primary immunodeficiency.