Prophylactic Antibiotics Versus Immunoglobulin Replacement in Specific Antibody Deficiency

Primary Immunodeficiency: Specific antibody deficiency with normal IgG

Specific antibody deficiency (SAD) is a common primary immunodeficiency disorder that should be considered in older children and adults with recurrent and/or severe sinopulmonary infections. The diagnosis is characterized by inadequate antibody response to polysaccharide vaccine, specifically, pneumococcal, with normal responses to protein antigens and normal levels of serum immunoglobulins as well as immunoglobulin G (IgG) subclasses. The underlying mechanism for SAD is not completely elucidated. It is understood that young children have limited polysaccharide responsiveness, which develops with increased age. Due to this phenomenon, the consensus is that there is adequate immune maturity after age 2 years, which is the earliest for the SAD diagnosis to be established. There remains a lack of consensus on thresholds for polysaccharide nonresponse, and there are several commercial laboratories that measure a range of serotypes, with the recommendation for patients to have their diagnostic evaluation with serotype testing both before vaccination and after vaccination to be conducted by the same laboratory. Once a diagnosis has been made, the management of SAD is based on the clinical severity. Clinicians may consider prophylactic antibiotics as well as immunoglobulin replacement. These patients should be closely followed up, with the possibility of discontinuation of IgG replacement after 12 to 24 months. Children are more likely to demonstrate resolution of SAD than are adolescents and adults. Patients with SAD may also progress to a more severe immunodeficiency; therefore, continued monitoring remains a crucial principle of practice in the care of patients with SAD.

IPINeT Ped-unPAD Study: Goals, Design, and Preliminary Results

Background: An unclassified primary antibody deficiency (unPAD) is a widely heterogeneous clinical entity, recently identified within the spectrum of Inborn Errors of Immunity (IEIs). Since unPAD has been traditionally considered as a mild condition, it has incorrectly received little attention, resulting in the paucity of extensive and comparable studies describing its natural history. To address the gaps in characterizing, understanding, and managing pediatric unPAD patients, the Italian Primary Immunodeficiency Network (IPINet) Ped-unPAD study has recently been launched. Methods: Seventeen IPINeT Centers have expressed interest to participate, and data collection is still on-going. Hereby, we anticipate preliminary key issues emerging from the first 110 enrolled patients, attending three IPINet Centers. Results: A proportion of unPAD patients have experienced a severe infectious phenotype, which required hospitalization in a quarter of patients and antibiotic prophylaxis or Immunoglobulin Replacement Therapy in approximately 10% of patients. In this partial cohort, a mean follow-up (FU) of 5 years confirmed unPAD diagnosis in fifty percent of cases, with the remaining being reclassified as the Transient Hypogammaglobulinemia of Infancy (25%) and other IEIs (25%), such as a Common Variable Immunodeficiency, Selective IgA deficiency, Selective IgM deficiency, and IgG3 subclass deficiency. Conclusions: Despite a phenotype overlap at diagnosis, clinicians should be aware that unPAD is a mutable condition that deserves comprehensive evaluation and long-term monitoring to dissect the final diagnosis for optimal treatment.

Inborn Errors of Immunity

Inborn errors of immunity occur in 1 in 1000 to 1 in 5000 individuals and are characterized by immune deficiency and immune dysregulation. The primary care provider (PCP) should be familiar with key features of these diagnoses including recurrent and/or severe infections, hyperinflammation, malignancy, and autoimmunity and have a low threshold to refer for evaluation. The PCP can begin a laboratory evaluation before referral by sending a complete blood count (CBC) with differential, antibody levels, vaccine titers, and possibly other tests. Management approaches vary from antibiotic prophylaxis to hematopoietic stem cell transplantation depending on the specific diagnosis.

High Frequency of Specific Polysaccharide Antibody Deficiency in Adults With Unexplained, Recurrent and/or Severe Infections With Encapsulated Bacteria

BACKGROUND

Primary immunodeficiencies (PIDs) in adults are mainly revealed by recurrent and/or severe bacterial infections. The objective of this study was to evaluate a systematic research strategy of PIDs in adults with unexplained bacterial infections, with a special focus on specific polysaccharide antibody deficiency (SPAD).

METHODS

In this prospective multicenter study, inclusion criteria were recurrent benign upper and lower respiratory tract infections (RTIs) for at least two years (group 1), at least one upper or lower RTI requiring hospitalization (group 2), and/or at least one invasive infection documented with encapsulated bacteria (group 3). Main exclusion criteria were all local and general conditions that could explain infections. If no PID diagnosis was made, response to polysaccharide antigens was assessed using a pneumococcal polysaccharide vaccine.

RESULTS

From March 2015 to March 2020, 118 patients were included (37 males, median age of 41 years): 73, 17, and 28 in groups 1, 2, and 3, respectively. Forty-seven PIDs were diagnosed, giving an estimated frequency of 39.8% (95% confidence interval [CI] [30.4, 48.8]). SPAD was the most frequent diagnosis by far (n = 37/47, 78.7%), and was made in 23, 5, and 9 patients from groups 1 to 3, respectively. All SPAD patients received conjugate vaccines and, according to their infectious history, were on surveillance or treated with preventive antibiotics (n = 6) and/or with immunoglobulins replacement therapy (n = 10), the latter being dramatically efficient in all cases.

CONCLUSIONS

Considering its high prevalence among adults with unexplained recurrent and/or severe bacterial infections, SPAD should be screened in those patients.

CLINICAL TRIALS REGISTRATION

NCT02972281.

Inborn Errors of Immunity

Inborn errors of immunity occur in 1 in 1000 to 1 in 5000 individuals and are characterized by immune deficiency and immune dysregulation. The primary care provider (PCP) should be familiar with key features of these diagnoses including recurrent and/or severe infections, hyperinflammation, malignancy, and autoimmunity and have a low threshold to refer for evaluation. The PCP can begin a laboratory evaluation before referral by sending a complete blood count (CBC) with differential, antibody levels, vaccine titers, and possibly other tests. Management approaches vary from antibiotic prophylaxis to hematopoietic stem cell transplantation depending on the specific diagnosis.

Risk Factors of Pneumonia in Primary Antibody Deficiency Patients Receiving Immunoglobulin Therapy: Data from the US Immunodeficiency Network (USIDNET)

BACKGROUND

Despite immunoglobulin replacement (IgRT) therapy, some patients with primary antibody deficiency (PAD) continue to develop respiratory infections. Recurrent and severe respiratory infections, particularly pneumonia, can lead to significant morbidity and mortality. Therefore, we sought to determine the risk factors of developing pneumonia in PAD patients, already receiving IgRT.

METHODS

We evaluated clinical and laboratory features of PAD patients enrolled in the US Immune Deficiency Network (USIDNET) registry by April 2017. Patients were included if they met the following criteria: (1) PAD diagnosis (common variable immunodeficiency (CVID), agammaglobulinemia, hypogammaglobinemia, and specific antibody deficiency (SAD) and (2) available data on infections before and after IgRT. Patients were excluded if they were not receiving IgRT, or if no pre/post infections data were available. Descriptive and multivariable logistic regression analyses were used to identify factors associated with pneumonia post-IgRT.

RESULTS

A total of 1232 patients met the inclusion criteria. Following IgRT, 218 patients (17.7%) were reported to have at least one pneumonia episode. Using multivariate logistic regression analysis, we found a statistically significant increased risk of pneumonia in patients with asthma (OR: 2.55, 95% CI (1.69-3.85), p < 0.001) bronchiectasis (OR: 3.94, 95% CI (2.29-6.80), p < 0.001), interstitial lung disease (ILD) (OR: 3.28, 95%CI (1.43-7.56), p < 0.005), splenomegaly (OR: 2.02, 95%CI (1.08-3.76), p < 0.027), allergies (OR: 2.44, 95% CI [1.44-4.13], p = 0.001), and patients who were not on immunosuppressives (OR: 1.61; 95%CI [1.06-2.46]; p = 0.027). For every 50 unit increase in IgA, the odds of reporting pneumonia post IgRT decreased (OR: 0.86, 95% CI [0.73-1.02], p = 0.062). Infectious organisms were reported in 35 of 218 patients who reported pneumonia after IgRT. Haemophilus influenzae was the most frequently reported (n = 11, 31.43%), followed by Streptococcus pneumoniae (n = 7, 20.00%).

CONCLUSION

Our findings suggest PAD patients with chronic and structural lung disease, splenomegaly, and allergies were associated with persistent pneumonia. However, our study is limited by the cross-sectional nature of the USIDNET database and limited longitudinal data. Further studies are warranted to identify susceptible causes and explore targeted solutions for prevention and associated morbidity and mortality.

CLINICAL IMPLICATIONS

Patients with primary antibody deficiency with structural lung disease, allergies, and splenomegaly are associated with persistent pneumonia post-IgRT.

Four diseases, PLAID, APLAID, FCAS3 and CVID and one gene (PHOSPHOLIPASE C, GAMMA-2; PLCG2): Striking clinical phenotypic overlap and difference

We suggest PLAID, APLAID, and FCAS3 have to be considered as different aspects of the same underlying condition, because of our long-term clinical and genetical experiences. Some CVID patients have the same disease-causing mutations in PLCG2 gene, so it may be better to define all of them as "PLCG2deficiency."

Specific Antibody Deficiency in Adult Patients With IgG or IgG Subclass Deficiency

Purpose

Specific antibody deficiency (SAD) involves a deficient response to a polysaccharide vaccine despite having normal immunoglobulin levels. The failure of the polysaccharide response can be observed as a component of various primary antibody deficiencies. However, only a few studies have described the clinical and immunological profiles in SAD and/or other primary immunodeficiencies (PIDs) in adults.

Methods

A total of 47 patients who had a clinical history suggestive of antibody deficiency or had already been diagnosed with various antibody deficiencies were enrolled. Polysaccharide responses to 7 pneumococcal serotypes (4, 6B, 9V, 14, 18C, 19F and 23F) were measured using the World Health Organization enzyme-linked immunosorbent assay (WHO-ELISA), and postvaccination immunoglobulin G (IgG) titers were compared to clinical and laboratory parameters.

Results

Based on the American Academy of Allergy, Asthma, and Immunology (AAAAI) criteria for the WHO-ELISA, 11 (23.4%) patients were diagnosed as having SAD. Sixteen-three percent of them had combined with other types of PID, such as IgG subclass deficiency and hypogammaglobulinemia. Postvaccination IgG titers for the serotypes 4/9V/18C correlated with IgG2 (P = 0.012, P = 0.001, and P = 0.004) and for 6B/9V/14 with IgG3 (P = 0.003, P = 0.041, and P = 0.036, respectively). The IgG3 subclass levels negatively correlated with forced expiratory volume in 1 second (FEV1, %) and FEV1/forced vital capacity (P < 0.001 and P = 0.001, respectively).

Conclusion

SAD can be diagnosed in patients with normal IgG levels as well as in those deficient in IgG or the IgG3 subclass, implicating that restricted responses to Streptococcus pneumoniae polysaccharide antigens commonly exist in patients with predominantly antibody deficiency.

Immunoglobulin Replacement Therapy Versus Antibiotic Prophylaxis as Treatment for Incomplete Primary Antibody Deficiency

Background

Patients with an IgG subclass deficiency (IgSD) ± specific polysaccharide antibody deficiency (SPAD) often present with recurrent infections. Previous retrospective studies have shown that prophylactic antibiotics (PA) and immunoglobulin replacement therapy (IRT) can both be effective in preventing these infections; however, this has not been confirmed in a prospective study.

Objective

To compare the efficacy of PA and IRT in a randomized crossover trial.

Methods

A total of 64 patients (55 adults and 9 children) were randomized (2:2) between two treatment arms. Treatment arm A began with 12 months of PA, and treatment arm B began with 12 months of IRT. After a 3-month bridging period with cotrimoxazole, the treatment was switched to 12 months of IRT and PA, respectively. The efficacy (measured by the incidence of infections) and proportion of related adverse events in the two arms were compared.

Results

The overall efficacy of the two regimens did not differ (p = 0.58, two-sided Wilcoxon signed-rank test). A smaller proportion of patients suffered a related adverse event while using PA (26.8% vs. 60.3%, p < 0.0003, chi-squared test). Patients with persistent infections while using PA suffered fewer infections per year after switching to IRT (2.63 vs. 0.64, p < 0.01).

Conclusion

We found comparable efficacy of IRT and PA in patients with IgSD ± SPAD. Patients with persistent infections during treatment with PA had less infections after switching to IRT.

Clinical Implication

Given the costs and associated side-effects of IRT, it should be reserved for patients with persistent infections despite treatment with PA.

Electronic supplementary material

The online version of this article (10.1007/s10875-020-00841-3) contains supplementary material, which is available to authorized users.

Delivery of subcutaneous immunoglobulin by rapid "push" infusion for primary immunodeficiency patients in Manitoba: a retrospective review

Background

Both intravenous and subcutaneous human immune globin G (IgG) replacement (IVIG and SCIG, respectively) reduce severe infection and increase serum IgG levels in primary immune deficiency disorder (PIDD) patients who require replacement. SCIG can be administered either with the aid of an infusion pump, or by patients or caregivers themselves, using butterfly needles and a syringe (“SCIG push”). SCIG offers advantages over IVIG, including higher steady state IgG levels, improved patient quality of life indicators, and decreased cost to the healthcare system, and for these reasons, SCIG has been increasingly used in Manitoba starting in 2007. We sought to determine the effectiveness of SCIG push in our local adult PIDD population.

Methods

We conducted a retrospective chart review of all adult patients enrolled in the SCIG push program in Manitoba, Canada from its inception in November 2007 through September 2018. We included patients who were naïve to IgG replacement prior to SCIG, and those who had received IVIG immediately prior. We collected data regarding serum IgG levels, antibiotic prescriptions, hospital admissions, and adverse events during a pre-defined period prior to and following SCIG initiation. Statistical significance was determined via two-tailed t-test.

Results

62 patients met inclusion criteria, of whom 35 were on IVIG prior and 27 were IgG replacement naïve. SCIG push resulted in an increase in serum IgG levels in those naïve to IgG replacement, as well as in those who received IVIG prior. SCIG push also resulted in a statistically significant reduction in number of antibiotic prescriptions filled in the naïve subgroup, and no significant change in antibiotics filled in the IVIG prior group. 8/62 PIDD patients (12.9%) left the SCIG program during our review period for varying reasons, including side-effects.

Conclusions

In a real-life setting, in the Manitoba adult PIDD population, SCIG push is an effective method of preventing severe infections, with most patients preferring to continue this therapy once initiated.