Pneumococcal Antibody Research Articles

Streptococcus pneumoniae serotype distribution in Bangladeshi under-fives with community-acquired pneumonia pre-10-valent pneumococcal conjugate vaccination

BackgroundStreptococcus pneumoniae is the most frequent causative pathogen of bacterial pneumonia in children worldwide. Bangladesh introduced the 10-valent pneumococcal conjugate vaccine (PCV10) in their national immunization program for infants in 2015. We assessed its potential coverage in under-fives with community-acquired pneumonia (CAP) in the years before PCV10 was introduced.MethodsA total of 1502 childhood pneumonia cases (< 5 year olds living in the urban section Kamalapur, Dhaka) were enrolled between 2011 and 2013. Acute phase and late (convalescent) serum samples were collected from 1380 cases. Serotype-specific pneumococcal antibody concentrations were measured using a 25-plex immunoassay panel. Pneumococcal CAP was diagnosed based on a serotype-specific pneumococcal antibody response.ResultsS. pneumoniae was serologically identified as causative pathogen in 406/1380 (29%) cases. The five most prevalent serotypes were (in descending order) 11A, 22F, 3, 2 and 19F. Based on the percentage of pneumonia cases associated with PCV10 vaccine types, the potential PCV10 coverage was 29% (116/406).ConclusionsIn almost a third of the studied cases S. pneumoniae was identified as a causative pathogen. Because of the characteristics of the immunoassay, this might well be a gross underestimation. Nevertheless, the potential PCV10-coverage was low. Given the high serotype diversity, the region might benefit greatly from a higher-coverage PCV or recombinant protein vaccine.

Pneumococcal Serotype-Specific Antibodies in Children with Recurrent Oto-sinopulmonary Infections.

Low titers to pneumococcal vaccine are a frequent finding in pediatric patients with recurrent oto-sinopulmonary infections. To characterize the pre- and post-immunization antibody trend for each serotype included in the pneumococcal 13-valent conjugate vaccine (PCV13), in a cohort of pediatric patients with recurrent oto-sinopulmonary infections. This retrospective review identified 182 patients with recurrent oto-sinopulmonary infections (131 required an immune workup and 99 had low pneumococcal titers leading to a PCV13 vaccine booster). Baseline pneumococcal serotype-specific antibody titers at initial visit and 6 weeks after the vaccine booster were obtained. An adequate response to the pneumococcal conjugate vaccine was deemed to be a 4-fold increase over baseline and/or a post-immunization titer of 1.3 µg/ml or greater. Overall, PCV13 booster provided a significant improvement in the number of protective titers, increasing from 3.6 serotypes at baseline to 11.1 serotypes at 6 weeks (p < 0.001). This increase correlated with improved clinical outcomes (81% showed no signs of recurrent infection after the first booster and 94% after a second booster). Post-immunization antibody concentrations were significantly higher than at baseline for all serotypes (p< 0.05) and only 8, 9N, and 12F did not exhibit a greater than 4-fold increase (p> 0.05) 6 weeks following booster. There were no differences between patients at different ages in post-immunization titer levels for all serotypes. In pediatric patients with recurrent oto-sinopulmonary infections, an additional pneumococcal booster proved to be effective in the protection of these children against further infections, across all age groups.

Persistence of immunity in children aged 2 months and 7 months – 5 years old after primary immunization with 13-valent pneumococcal conjugate vaccine

Background: Pneumococcus is a common cause of pneumonia, meningitis, and other serious infections in children. The previous study has proved that the 13-valent pneumococcal conjugate vaccine (PCV13) has sufficient immunogenicity in children. The data on long-term persistence of immunity will help the follow-up development work of pneumococcal vaccines.Methods: Children who received the full vaccination course of the tested PCV13 in the previous clinical trial were enrolled again, and these who received other pneumococcal vaccines, or were infected with one or more serotypes of S. pneumoniae corresponding to PCV13 before enrollment were excluded. Participants were divided into four groups by age which is same as that of previous trial. The study lasted for 5 years, during which we measured pneumococcal antibodies of 13 serotypes included in PCV13 at particular points in time. Geometric mean concentrations (GMCs) and seropositive rates (the rate of IgG concentration ≥0.35 μg/mL) of antibodies against 13 serotypes were calculated.Results: For the participants aged 2 months, five years after primary vaccination, except for serotypes 3 and 4, seropositive rates were 100%. GMCs of IgG antibodies against 13 serotypes ranged from 0.733 to 15.160 μg/mL. All of the participants aged 7–11 months had the serotype-specific IgG concentration ≥0.35 μg/mL four years after primary vaccination with the exception of serotypes 3, 4, 6 A and 9 V. IgG GMCs were 0.753–11.031 μg/mL. All participants aged 12–23 months and 2–5 years old had the serotype-specific IgG concentration ≥0.35 μg/mL three or two years after primary vaccination respectively, except for serotype 3. IgG GMCs ranged from 0.815 to 13.111 μg/mL, and 0.684 to 12.282 μg/mL respectively.Conclusion: PCV13 was applied to the population aged 2 months and 7 months - 5 years old with a good immune persistence, providing more extensive evidence of long-term efficacy for that vaccine.Trial Registration: The trial was registered with ClinicalTrials.gov, number NCT06210737.

Quantity and Quality of Naturally Acquired Antibody Immunity to the Pneumococcal Proteome Throughout Life.

Young children and older adults are susceptible for invasive pneumococcal disease (IPD) caused by Streptococcus pneumoniae. Pneumococcal protein-specific antibodies play a protective role against IPD; however, not much is known about the pace of acquisition, maturation, and maintenance of these antibodies throughout life. Immunoglobulin G (IgG) and IgA levels, avidity, and/or specificity to the pneumococcal proteome in serum and saliva from healthy young children, adults, and older adults, with known carriage status, were measured by enzyme-linked immunosorbent assay (ELISA) and 2-dimensional western blotting against ΔcpsTIGR4. Eleven-month-old children, the youngest age group tested, had the lowest pneumococcal proteome-specific IgG and IgA levels and avidity in serum and saliva, followed by 24-month-old children and were further elevated in adult groups. Among adult groups, the parents had the highest serum and saliva IgG and IgA antibody levels. In children, antibody levels and avidity correlated with daycare attendance and presence of siblings, posing as proxy for exposure and immunization. Immunodominance patterns slightly varied throughout life. Humoral immunity against the pneumococcal proteome is acquired through multiple episodes of pneumococcal exposure. Low-level and low-avidity antiproteome antibody profiles in young children may contribute to their IPD susceptibility, while in overall antiproteome antibody-proficient older adults other factors likely play a role.

Developmentand validation of carbodiimide-activated ELISA plate for quantifying IgG levels against Streptococcus pneumoniae capsular polysaccharides.

Background:Conventional microtiter plates lack the surface strength needed for effective binding of pneumococcalpolysaccharide antigens. This study tackles the limitation by altering the surface of polystyrene plates through carbodiimide activation under acidic pH conditions.Method:The microtiter plates were activated with carbodiimide coupling agents, N,N'-Dicyclohexylcarbodiimide (DCC) and N-Hydroxysuccinimide (NHS). They were subsequently coated with 13 pneumococcal antigens at a concentration of 5 μg/ml with a pH of 3.5. The IgG antibody titer was assessed utilizing the World Health Organization (WHO) ELISA protocol for 30 human serum samples. In addition, validation experiments were conducted to evaluate specificity and precision.Results: The modified plates exhibited two-times higher antibody titers compared to conventional plates across all 13 serotypes. Observations revealed elevated antibody levels, with geometric concentrations ranging between 0.96 μg/ml and 4.24 μg/ml.Conclusion:Carbodiimide activation and acidic pH modification of microtiter plates enhance sensitivity and specificity in detecting pneumococcal antibodies, critical for vaccination planning and immunity assessment.

Serological profiling of pneumococcal proteins reveals unique patterns of acquisition, maintenance and waning of antibodies throughout life.

Streptococcus pneumoniae is a leading cause of morbidity and mortality in children and older adults. Yet knowledge on the development of pneumococcal protein-specific antibody responses throughout life is limited. To investigate this, we measured serum IgG levels to 55 pneumococcal proteins in 11-month old infants (n=73), 24-month old children (n=101), parents (n=99), adults without children <6 years of age (n= 99) and older adults aged >60 years (n=100). Our findings revealed low IgG levels in infancy, with distinct development patterns peaking in adults. A decrease in levels was observed for 27 antigens towards older age. Adults and older adults had increased IgG levels during pneumococcal carriage and at increased exposure risk to S. pneumoniae. Carriage was a stronger predictor than exposure or age for antibody responses. These findings highlight the dynamic nature of naturally acquired humoral immunity to pneumococcal proteins throughout life, offering insights for age-targeted interventions.

51 Polymicrobial necrotizing pneumonia in a 3-year-old child with nearabsent pneumococcal antibody and mitogen interferon-γ responses

51 Polymicrobial necrotizing pneumonia in a 3-year-old child with nearabsent pneumococcal antibody and mitogen interferon-γ responses

38 Young Children With Recurrent Infection and Allergic Background Have Inadequate Baseline Pneumococcal Antibodies

38 Young Children With Recurrent Infection and Allergic Background Have Inadequate Baseline Pneumococcal Antibodies

In Vitro Evaluation of Effect of Storage Time on Immunogenicity of the 10-Valent Pneumococcal Conjugate Vaccine Using Baby Rabbit Complement &amp; HL-60 Cells

Background: The efficacy and effectiveness of a vaccine is influenced by several factors including storage duration. Additionally, vaccines may be sufficiently administered but functionality of antibody generated may be hampered with by other factors such as nutritional status of the patient. As such, one of the ways of assessing vaccine efficacy is assessing the functionality of the antibodies generated. The 10v-PCV is a highly effective vaccine used to prevent invasive pneumococcal diseases in children. However, here in Kenya, cases of pneumococcal diseases are high and challenging to treat. This study thus aimed to evaluate the effect of storage of PCV-10 storage time on the functionality of Abs generated. Methodology; An in vitro experimental research design was employed for this study. opsonophagocytic activity assay using HL-60 Cells &amp; Baby rabbit complement was used to assess whether or not the Pneumococci Serotype IgG antibodies elicited following administration with 10v-PCV vaccine are functional. Only 10v-PCV vaccine with same production date were procured. Twenty experimental rabbits of same gender were procured and used injected intraperitoneally with 3 doses of 100µl (0.34g) of 10v-PCV vaccine after every four weeks. Antibody functionality was then assessed using the opsonophagocytic activity assay method. Results: An average of 28.9% of pneumococcus exposed to the vaccine-induced secreted antibodies were killed by the pneumococcal IgG antibody. The highest percentage of number of bacteria killed was achieved after the 3rd dose of vaccination. There was no significant influence of storage duration on opsonophagocytic activity of generated antibodies. Conclusion: Storing of 10v-PCV vaccine up to 12 weeks does not significantly affect the opsonophagocytic activity of pneumococcal IgG antibodies.

Mycophenolate mofetil hampers antibody responses to a broad range of vaccinations in kidney transplant recipients: Results from a randomized controlled study

To study the effect of mycophenolate mofetil (MMF) on various vaccination responses in kidney transplant recipients. In a randomized controlled trial (EudraCT nr.: 2014-001372-66), low immunologically risk kidney transplant recipients were randomized to TAC/MMF or TAC-monotherapy (TACmono), six months post-transplantation. One year after transplantation, in a pre-specified sub-study, recipients were vaccinated against pneumococcus, tetanus and influenza. Blood was sampled before and 21 days after vaccination. Adequate vaccination responses were defined by international criteria. A post-hoc analysis was conducted on SARS-CoV-2 vaccination responses within the same cohort. Seventy-one recipients received pneumococcal and tetanus vaccines (TAC/MMF: n=37, TACmono: n=34), with 29 also vaccinated against influenza. When vaccinated, recipients were 60 (54-66) years old, with median eGFR of 54 (44-67) ml/min, tacrolimus trough levels 6.1 (5.4-7.0) ug/L in both groups and TAC/MMF daily MMF dose of 1000 (500-2000) mg. Adequate vaccination responses were: pneumococcal (TAC/MMF 43%, TACmono 74%, p=0.016), tetanus (TAC/MMF 35%, TACmono 82%, p<0.0001) and influenza (TAC/MMF 20%, TACmono 71%, p=0.0092). Only 7% of TAC/MMF responded adequately to all three compared to 36% of TACmono (p=0.080). Additionally, 40% of TAC/MMF responded inadequately to all three, whereas all TACmono patients responded adequately to at least one vaccination (p=0.041). Lower SARS-CoV-2 vaccination antibody responses correlated with lower pneumococcal antibody vaccination responses (correlation coefficient: 0.41, p=0.040). MMF on top of tacrolimus severely hampers antibody responses to a broad range of vaccinations.

Persistence of antibody to 23-valent pneumococcal polysaccharide vaccine: a 5-year prospective follow-up cohort study

ABSTRACT Background Pneumococcal vaccines are effective in preventing pneumococcal diseases in adults. The evaluation of the antibodies persistence to the 23-valent pneumococcal polysaccharide vaccine (PPV23) could provide evidence on PPV23 revaccination. Research design and methods Adults aged ≥ 60 years were selected and vaccinated with PPV23 in Shanghai, and followed up for 5 years with blood samples collection of a 1-year interval. The geometric mean concentrations (GMC) of the IgG against 23 pneumococcal serotypes covered by PPV23 were detected using enzyme-linked immunosorbent assay. The antibodies to 23 pneumococcal serotypes among different groups was analyzed using statistical analysis. Results Overall, 517 participants completed all six visits over a 5-year period (2013–2018). The GMC of 23 serotypes in adults aged ≥ 60 years decreased slowly after PPV23 vaccination compared to baseline pre-vaccination (P < 0.05), except serotype 3. Additionally, the multiplicative increase in the antibody concentration after PPV23 vaccination was greater, and the antibody levels of serotypes 1 and 6B were significantly higher at visit 5 than at visit 4 (P < 0.05). Conclusions The pneumococcal antibodies in elderly after PPV23 vaccination could sustain high levels over long-term follow-up, which suggested that the interval of revaccination with PPV23 in elderly should be at least 5 years after the first vaccination.

Outcomes of Children with a History of Pneumococcal Antibody Testing

Outcomes of Children with a History of Pneumococcal Antibody Testing

Experience with 23-valent pneumococcal polysaccharide vaccine in patients with ankylosing spondylitis and psoriatic arthritis

Pneumococcus plays a primary role as a causative agent of pneumonia both in the general population and in patients with immuno-inflammatory rheumatic diseases (IVRS), including spondylarthritis (SpA). However, data on the immunogenicity, efficacy and safety of pneumococcal vaccines in patients with SpA are limited.The aim of the study. To study the immunogenicity, efficacy and safety of the 23-valent pneumococcal polysaccharide vaccine (PPV-23) in patients with ankylosing spondylitis (AS) and psoriatic arthritis (PsA), observed at the V.A. Nasonova Research Institute (Moscow, Russia).Materials and methods. 145 people were included in the study: 51 patients with AS, 25 with PsA, 69 in control group (СG) without IVR. The majority of patients (65.8%) received immunosuppressive therapy. PPV-23 was administered in an amount of one dose (0.5 ml) subcutaneously against the background of antirheumatic therapy, regardless of the activity of the main IVR. The level of antibodies (AT) to pneumococcal capsular polysaccharide was determined using the EIA PCP IgG kit (TestLine Clinical Diagnostics, Czech Republic) before vaccination and 1, 3 and 12 months after it. The clinical efficacy and safety of PPV-23 were also evaluated, including the effect on the activity of AS and PsA according to the dynamics of BASDAI and DAPSA indices.Results. After 1, 3 and 12 months after vaccination, the concentration of pneumococcal AT was significantly higher compared to baseline values, which indicates sufficient immunogenicity of PPV-23. The clinical efficacy of PPV-23 in patients with AS and PsA was 98.7%. In general, there was no negative effect of vaccination on the activity of the underlying disease. The frequency of postvaccinal reactions in patients and in СG was comparable.Conclusions. The obtained results of the study indicate sufficient immunogenicity, clinical efficacy and safety of PPV-23 in patients with AS and Ps A.

Spleen function is reduced in individuals with NR5A1 variants with or without a difference of sex development: a cross-sectional study.

NR5A1 is a key regulator of sex differentiation and has been implicated in spleen development through transcription activation of TLX1. Concerns exist about hypo- or asplenism in individuals who have a difference of sex development (DSD) due to an NR5A1 disease-causing variant. We aimed to assess spleen anatomy and function in a clinical cohort of such individuals and in their asymptomatic family member carriers. Cross-sectional assessment in 22 patients with a DSD or primary ovarian insufficiency and 5 asymptomatic carriers from 18 families, harboring 14 different NR5A1 variants. Spleen anatomy was assessed by ultrasound, spleen function by peripheral blood cell count, white blood cell differentiation, percentage of nonswitched memory B cells, specific pneumococcal antibody response, % pitted red blood cells, and Howell-Jolly bodies. Patients and asymptomatic heterozygous individuals had significantly decreased nonswitched memory B cells compared to healthy controls, but higher than asplenic patients. Thrombocytosis and spleen hypoplasia were present in 50% of heterozygous individuals. Four out of 5 individuals homozygous for the previously described p.(Arg103Gln) variant had asplenia. Individuals harboring a heterozygous NR5A1 variant that may cause DSD have a considerable risk for functional hyposplenism, irrespective of their gonadal phenotype. Splenic function should be assessed in these individuals, and if affected or unknown, prophylaxis is recommended to prevent invasive encapsulated bacterial infections. The splenic phenotype associated with NR5A1 variants is more severe in homozygous individuals and is, at least for the p.(Arg103Gln) variant, associated with asplenism.

Tdap vaccine in pregnancy and immunogenicity of pertussis and pneumococcal vaccines in children: What is the impact of different immunization schedules?

BackgroundIn 2019, the 3 + 1 schedule for children’s vaccination (2–4–6–18 months old) was changed for a reduced 2 + 1 schedule (2–4–12 months old) in Quebec, Canada. We compared the post-booster anti-pertussis and anti-pneumococcus IgG antibody concentrations among children of Tdap-vaccinated and unvaccinated mothers for different vaccine schedules and vaccine formulations. MethodsWe conducted an observational cohort study. An invitation letter to potential participants was provided during a routine vaccination visit. Children’s blood samples were analyzed post-booster at 13 (2 + 1 schedule) or 19 (3 + 1 schedule) months of age for antibodies against pertussis antigens (pertussis toxin (PT), filamentous hemagglutinin (FHA) and pertactin (PRN)) and pneumococcal antigens (serotypes 4, 18C, 19A, and 19F). IgG concentrations among children of Tdap-vaccinated and unvaccinated mothers for each vaccination schedule were compared using geometric mean concentrations (GMCs) and GMC ratios (GMRs), adjusting for potentially immune-response-influencing factors (aGMR). Serotype-specific pneumococcal seroprotection rates were also compared. ResultsA total of 360 children were included for pertussis analysis and 248 for pneumococcal analysis. For the 2 + 1 schedule, 13-month-old children of Tdap-vaccinated mothers had lower GMCs against PT, FHA, and PRN, with aGMR (95 %CI) of 0.77 (0.65–0.90), 0.66 (0.55–0.79), 0.72 (0.52–0.99), respectively. For the 3 + 1 schedule, at 19 months old, the interference appeared to be attenuated (higher aGMR values). GMCs against PT were slightly higher in the 3 + 1 than the 2 + 1 schedule: 126.5 IU/ml vs 91.6 IU/ml; aGMR = 1.27. GMCs against PT, FHA and PRN were slightly higher among children who received Infanrix hexa® compared to those who received Pediacel® at 12 months old. For pneumococcal antibodies, at 13 months old, there was no strong evidence of immune interference in children of Tdap-vaccinated mothers. ConclusionInfant vaccination schedule may influence immune interference associated with maternal Tdap vaccination. More studies are needed to assess the clinical impact of this interference on children’s protection.

Worldwide Index of Serotype-Specific Pneumococcal Antibody Responses (WISSPAR): A curated database of clinical trial data.

The Worldwide Index of Serotype Specific Pneumococcal Antibody Responses (WISSPAR; https://wisspar.com), is a centralized, online platform housing data on immunogenicity from clinical trials of pneumococcal vaccines. The data on WISSPAR are primarily curated from outcomes tables from clinical trials and are made available in a searchable format that can be readily used for downstream analyses. The WISSPAR database includes trials covering numerous vaccine products, manufacturers, dosing schedules, age groups, immunocompromised groups, and geographic regions. Customizable data visualization tools are embedded within the site, or the data can be exported for further analyses. Users can also browse summary information about the clinical trials and their results. WISSPAR provides a platform for analysts and policy makers to efficiently gather, compare, and collate clinical trial data about pneumococcal vaccines.

Duration of Protection From Pneumonia After Pneumococcal Vaccination in Hemodialysis Patients (DOPPIO): Protocol for a Prospective Multicenter Study.

Pneumonia is a leading cause of death in patients with end-stage chronic kidney disease treated with dialysis. Current vaccination schedules recommend pneumococcal vaccination. However, this schedule disregards findings of rapid titer decline in adult hemodialysis patients after 12 months. The primary objective is to compare pneumonia rates between recently vaccinated patients and patients vaccinated more than 2 years ago. As an exploratory objective, antipneumococcal antibody titers in hemodialysis patients will be determined as a function. Factors influencing antibody kinetics will be identified. Within this prospective multicenter study, we aim to compare 2 strata of vaccinated patients: those recently vaccinated and those vaccinated more than 2 years ago. A total of 792 patients will be enrolled. Twelve partner sites (within the German Centre for Infection Research [DZIF]) with allocated dialysis practices participate in this study. All dialysis patients who are vaccinated against pneumococcal infection in accordance with Robert Koch Institute guidelines prior to enrollment will be eligible. Data on baseline demographics, vaccination history, and underlying disease will be assessed. Pneumococcal antibody titers will be determined at baseline and every 3 months for 2 years. DZIF clinical trial units coordinate titer assessment schedules and actively follow-up on study patients for 2-5 years after enrollment, including validation of end points of hospitalization, pneumonia, and death. The study has enrolled 792 patients and the last follow-up has been completed. Currently, the statistical and laboratory analyses are ongoing. Results will increase physician adherence to current recommendations. Establishing a framework for the efficient evaluation of guideline recommendations through a combination of routine and study data will inform the evidence base for future guidelines. ClinicalTrials.gov NCT03350425; https://clinicaltrials.gov/ct2/show/NCT03350425. DERR1-10.2196/45712.

Non-protective immunity after standard pneumococcal vaccination series identified as a potential contributing risk factor for refractory otolaryngologic conditions in children.

To examine the relationship between conferred immunity after standard pneumococcal series and refractory otolaryngologic infections in pediatric patients using post-vaccination antibody titers, and to identify contributory underlying conditions revealed when vaccination/re-vaccination fails to confer protective immunity. IRB-reviewed and "exempt" retrospective case series with chart review using the Epic® Electronic Medical Record system from 2013 to 2021. Dedicated tertiary referral children's hospital. Pneumococcal antibody titer results were assessed for children ages 0 to 21 years and: (1) at least 1 of 7 otolaryngologic disease diagnoses and (2) having received the 4-dose schedule of pneumococcal conjugate vaccine (PCV 7 or 13). A total of 241 subjects met inclusion criteria with 356 laboratory tests. Recurrent acute otitis media, chronic rhinitis, and chronic otitis media with effusion were the 3 most frequent diagnoses. At presentation, only 27.0% of subjects had titers conferring immunity from their prior vaccinations with PCV. About 85 subjects had been subsequently revaccinated with Pneumococcal Polysaccharide Vaccine (PPSV), and antibody responses conferring immunity reached 91.8%. Seven subjects never developed adequate responses; 5 of these had recurrent acute otitis media as the primary otolaryngologic diagnosis. Secondary "revealed" diagnoses included Juvenile Rheumatoid Arthritis (n = 1), unresolved specific antibody deficiency (n = 2), and Hypogammaglobulinemia (n = 1). In pediatric patients with recurrent infectious otolaryngologic disease refractory to traditional medical and surgical therapy, inadequate responses to pneumococcal vaccination may be revealed. This correlation represents a potential pathway for diagnosis and therapy.

IRF2BP2 mutation with autoimmune enteropathy, immune deficiency, and respiratory failure

Case historyWe present the case of a 31-year-old Hispanic male with history of recurrent bronchiectasis, invasive aspergillosis, and severe persistent asthma, who is now status post lung transplant for end-stage lung disease. He initially presented at 7 years of age with diarrhea, failure to thrive, and nearly absent immunoglobulin levels (IgG < 33 mg/dL, IgA < 7 mg/dL, IgM = 11 mg/dL, IgE = 4 IU/dL) necessitating IVIG treatment. Small intestinal biopsy showed villous atrophy consistent with autoimmune enteropathy. Sweat chloride was reported as indeterminate (44 me/dL). Initial WBC, platelet, and T- and NK-cell counts were within normal range, and B-cell count and percentage were borderline low. Most recently, he was found to have increased immature B-cell count (CD21low), decreased memory B-cells, and poor pneumococcal vaccine antibody response. Patient has been hospitalized numerous times with increasingly severe bronchiectasis, pneumonitis, and COVID-19 infections twice despite vaccination, leading to respiratory failure and lung transplantation. Family history is negative for immune deficiency and lung diseases. DiscussionOf these 3 VUSs (see the table), the one in IRF2BP2 has the most pathogenic potential due to its autosomal dominant inheritance, its location in a conserved domain (Ring), and previous case reports of pathogenic variants at the same or adjacent alleles 1–3. Baxter et al reported a de novo truncating mutation in IRF2BP2 at codon 536 (c.1606CinsTTT), which is similar to our patient's mutation. This patient was noted to have an IPEX-like presentation, with chronic diarrhea, hypogammaglobulinemia, and recurrent infections. Variant Functional Prediction Score for our variant predicts a potentially high damage effect. There are 2 other case reports of heterozygous mutations in loci adjacent to this allele; one (c.1652G>A)2 with a similar clinical phenotype to our patient and the other (C.625-665 del)3 with primarily inflammatory features and few infections. ImpactThis case highlights a variant in IRF2BP2 associated with severe hypogammaglobulinemia, recurrent pulmonary infections, and autoimmune enteropathy.Table 1(abstract: 126)ClassificationGeneExon/IntronDNA changeProtein changeZygosityInheritanceOMIMAssociated diseaseUncertain significanceIRF2BP22c.1606C>Tp.Gln536TerHeterozygousAutosomal Dominant615332Immunodeficiency Common variable, 14Uncertain SignificanceLRBA30c.4832C>Tp.Thr1611lleHeterozygousAutosomal Recessive606453Immunodeficiency Common variable, 8, with autoimmunityPathogenicCFTR4c.350G>Ap.Arg117HisHeterozygousAutosomal Recessive602421CFTR- related disorders

The Multiplexed Opsonophagocytosis Killing Assay (MOPA) in Evaluating Specific Antibody Responses in Patients with Recurrent Infections

Assessments of antibody responses to vaccines are essential tools for evaluating humoral immune responses in subjects with suspected inborn errors of immunity (IEI). Low pneumococcal IgG levels following pneumococcal vaccination indicate suboptimal humoral immune function and are often used for diagnosis of IEI. The Multiplexed Opsonophagocytosis Assay (MOPA) measures pneumococcal antibody function (PAF) via killing of pneumococci by serum antibodies in vitro. MOPA may also be useful for clinical diagnosis but has not been studied in patients with suspected IEI. We aimed to compare PAF and Streptococcus pneumoniae IgG levels in patients with recurrent infections. We also evaluated the clinical history and other immune workup results, when available. We collected serum samples from n = 17 patients with a history of recurrent infections undergoing pneumococcal IgG measurements by their primary clinical immunologists. Baseline sera (prior to vaccine challenge) were analyzed for PAF, for the serotypes present in pneumococcal conjugate vaccine (PCV13), and S. pneumoniae 23 serotypes IgG levels using MOPA and a multiplexed bead array assay, respectively. The cohort includes subjects from 2 to 60 years of age, 53% females, 94% Caucasian, and 30% Hispanic. Preliminary results show that 76% patients had protective PAF for 85% or more of the tested serotypes. Of these, 69% patients had received a pneumococcal vaccine in the previous five years as an indication for an underlying high risk medical condition or as part of their immunization schedule. Protective results for serotypes 3, 4, 9V, and 18C were discrepant between IgG levels and PAF in more than 50% of patients. We also found discrepancy between PAF and antibody levels in 35% of patients, showing intact PAF for 5 or more serotypes despite low serotype IgG levels; 83% of whom had no significant sinopulmonary infections in the last year. MOPA analysis between pre and post pneumococcal vaccine administration, in those patients for which it is clinically indicated, is currently in process. This analysis may provide more information regarding the diagnostic performance and predictive value of MOPA in patients with suspected IEI, but preliminary data shows that MOPA might be more reflective of protection than S. pneumonia IgG levels.