Reference intervals for lymphocyte subsets in preterm and term neonates without immune defects

Gender and sex hormone effects on neonatal innate immune function

OBJECTIVES

Scientific evidence provides a widened view of differences in immune response between male and female neonates. The X-chromosome codes for several genes important in the innate immune response and neonatal innate immune cells express receptors for, and are inhibited by, maternal sex hormones. We hypothesized that sex differences in innate immune responses may be present in the neonatal population which may contribute to the increased susceptibility of premature males to sepsis. We aimed to examine the in vitro effect of pro-inflammatory stimuli and hormones in neutrophils and monocytes of male and female neonates, to examine the expression of X-linked genes involved in innate immunity and the miRNA profiles in these populations.

METHODS

Preterm infants (n = 21) and term control (n = 19) infants were recruited from the Coombe Women and Infants University Hospital Dublin with ethical approval and explicit consent. The preterm neonates (eight female, 13 male) were recruited with a mean gestation at birth (mean ± SD) of 28 ± 2 weeks and corrected gestation at the time of sampling was 30 + 2.6 weeks. The mean birth weight of preterm neonates was 1084 ± 246 g. Peripheral blood samples were used to analyze immune cell phenotypes, miRNA human panel, and RNA profiles for inflammasome and inflammatory genes.

RESULTS

Dividing neutrophil results by sex showed no differences in baseline CD11b between sexes among either term or preterm neonates. Examining monocyte CD11b by sex shows, that at baseline, total and classical monocytes have higher CD11b in preterm females than preterm males. Neutrophil TLR2 did not differ between sexes at baseline or following lipopolysaccharide (LPS) exposure. CD11b expression was higher in preterm male non-classical monocytes following Pam3CSK treatment when compared to females, a finding which is unique to our study. Preterm neonates had higher TLR2 expression at baseline in total monocytes, classical monocytes and non-classical monocytes than term. A sex difference was evident between preterm females and term females in TLR2 expression only. Hormone treatment showed no sex differences and there was no detectable difference between males and females in X-linked gene expression. Two miRNAs, miR-212-3p and miR-218-2-3p had significantly higher expression in preterm female than preterm male neonates.

CONCLUSIONS

This study examined immune cell phenotypes and x-linked gene expression in preterm neonates and stratified according to gender. Our findings suggest that the responses of females mature with advancing gestation, whereas male term and preterm neonates have very similar responses. Female preterm neonates have improved monocyte activation than males, which likely reflects improved innate immune function as reflected clinically by their lower risk of sepsis. Dividing results by sex showed changes in preterm and term infants at baseline and following LPS stimulation, a difference which is reflected clinically by infection susceptibility. The sex difference noted is novel and may be limited to the preterm or early neonatal population as TLR2 expression on monocytes of older children does not differ between males and females. The differences shown in female and male innate immune cells likely reflect a superior innate immune defense system in females with sex differences in immune cell maturation. Existing human studies on sex differences in miRNA expression do not include preterm patients, and most frequently use either adult blood or cord blood. Our findings suggest that miRNA profiles are similar in neonates of opposite sexes at term but require further investigation in the preterm population. Our findings, while novel, provide only very limited insights into sex differences in infection susceptibility in the preterm population leaving many areas that require further study. These represent important areas for ongoing clinical and laboratory study and our findings represent an important contribution to exiting literature.

Lower peripheral blood CD4+ lymphocyte ratio is associated with severe bronchopulmonary dysplasia

OBJECTIVE

To elucidate the characteristics of lymphocyte subsets in bronchopulmonary dysplasia (BPD) diagnosis following Jensen's criterion to understand the spectrum of lymphocytes in different degrees of BPD.

STUDY DESIGN

This single-center retrospective cohort study included 120 neonates admitted to the neonatal intensive care unit between 1 July 2014 and 30 June 2021, who had undergone peripheral blood lymphocyte subpopulation detection.

RESULTS

Thirty-one neonates were included in the control group, whereas 33 infants with BPD were included in the case group. In addition, we selected 56 infants with a gestational age (GA) <37 weeks without BPD who were receiving oxygen therapy. Among the three groups, the B cell and NK cell frequencies were significantly higher and the frequencies of T cells and CD4+ cells were significantly lower in the BPD group. In newborns without BPD, the distribution of T lymphocyte subsets was similar at different GAs. Comparing different degrees of BPD, the patients in the grades 2-3 BPD group had significantly lower percentages of T lymphocytes and CD4+ T cells than those in the other groups. Remarkably, the frequencies of NK cells were significantly higher in patients with grades 2-3 BPD, and the Treg cells slightly increased with BPD severity, although the differences were not significant.

CONCLUSION

Healthy neonates had similar ratios of lymphocyte subsets among different GAs; although as the GAs increased, the percentage of lymphocytes increased slightly. Severe BPD was associated with lower CD4+ T cells and higher NK cells. However, whether such changes were the cause or the consequence of BPD has not been determined.

Immunophenotypes of Newborns From SARS-CoV-2-infected Mothers

BACKGROUND

Little is known about the neonatal immunologic response to a maternal SARS-CoV-2 infection present during childbirth. Here we analyze a cohort of 75 neonates from SARS-CoV-2-infected mothers.

METHODS

The SARS-CoV-2 infection status was laboratory assessed by real-time reverse transcription polymerase chain reaction on nasopharyngeal swabs (NPS) in both mothers during childbirth and neonates within 24 hours of life. Immunophenotypes of peripheral blood mononucleated cells and SARS-CoV-2 antispike IgA, IgM and IgG of the newborns were recorded. Ten (13.3%) of 75 neonates had positive NPS for SARS-CoV-2; 17 of 75 (23%) were SARS-CoV-2-IgG seropositive, of which one with positive NPS. All the newborns resulted seronegative for SARS-CoV-2 IgA and IgM and were asymptomatic. Our cohort of newborns was divided into groups according to IgG seropositivity (IgG+/-) and NPS results (NPS+/-).

RESULTS

The count and proportion of lymphocyte subsets (evaluated measuring CD3, CD4, CD8 and CD19 markers) and of natural killer cells (evaluated by measuring the CD3-/CD16+/CD56+ subset) were all in the normal range, with no statistical differences among groups. We found a significant expansion of the T cell (CD3+) subset in the IgG+ group interpreted as the result of immune effects triggered by trained immunity in these newborns, but a decrease in CD4+ T cells for NPS+ neonates. It is therefore difficult to conclude that the decrease in CD4 can certainly be caused by an infection.

CONCLUSIONS

A maternal SARS-CoV-2 infection resulted in an expansive effect of CD3+ T cells in IgG+ newborns; nonetheless, it seems not to affect structural and functional development of the newborn immune system.

Congenital cytomegalovirus infection in a preterm infant with 22q11.2 deletion syndrome and immunological abnormalities

The 22q11.2 deletion syndrome has many complications; one of them is immunodeficiency. However, the time of onset and the degree of immunodeficiency can vary. We report a case of a preterm infant with congenital cytomegalovirus infection complicated with 22q11.2 deletion syndrome and immunological abnormalities. Ultrasonography revealed pulmonary atresia, ventricular septal defect, major aortopulmonary collateral artery, and thymic hypoplasia. His serum chemistry tests on admission revealed immunoglobulin G, A, and M levels of 1,547 mg/dL, 70 mg/dL, and 274 mg/dL, respectively. A surface antigen analysis of the peripheral lymphocytes using flow cytometry revealed the following: relatively low CD4-positive T-cell levels (18.1%; 1,767/μL), very high CD8-positive T-cell levels (58.9%; 5,751/μL), and CD4/CD8 ratio of 0.31. The level of T-cell receptor excision circles was relatively low at 17.5 copies/μL. After birth, the CD8-positive T-cell level began to gradually decrease, whereas the CD4/CD8 ratio began to increase. Thrombocytopenia, neutropenia, and skin petechiae were observed on admission. However, the condition improved. Treatment for congenital cytomegalovirus infection was not provided due to the absence of viremia. Unfortunately, the patient died suddenly on the 158th day of life, and the cause of death was unknown. To the best of our knowledge, no association between 22q11 deletion syndrome and cCMV has been described in the recent medical literature. According to the calculation, around one newborn infant who have both 22q11 deletion syndrome and cCMV infection will be born each year in Japan. Healthcare providers should pay more attention to this medical situation in the future.

Kocuria species: an underappreciated pathogen in pediatric patients-a single-center retrospective analysis of 10 years' experience in China

Kocuria species are known to be opportunistic pathogens that cause infections in humans, especially immunocompromised hosts. However, reports of pediatric patients are limited. This retrospective study was designed to investigate the spectrum of infections in pediatric patients caused by Kocuria species. Thirty-six patients were enrolled; of these, 29 were infected by Kocuria kristinae, 4 by Kocuria roseus, 2 by Kocuria varians, and 1 by Kocruria rhizophila. Twenty-six patients were diagnosed with bloodstream infection; 6 had ventilator-associated pneumonia; and one each had a catheter-associated urinary tract infection, purulent meningitis, cholangitis, and empyema. Twenty-seven patients were immunocompromised or debilitating, had congenital abnormalities or fitted with indwelling devices. Nine patients were immunocompetent, 4 with early onset before 1 year of age. All Kocuria species were susceptible to lenezolid, vancomycin, and tigecycline; while showing frequent resistance to penicillin and oxacillin. Most cases were cured by administering appropriate antimicrobial agents. To our knowledge, this is the largest case series of pediatric patients with Kocuria species infection. We highlight Kocuria species should be considered as an underappreciated pathogen in pediatric patients.

Disease Evolution in Women With Highly Active MS Who Suspended Natalizumab During Pregnancy vs Rituximab/Ocrelizumab Before Conception

BACKGROUND AND OBJECTIVES

In women with highly active multiple sclerosis (MS), suspending rituximab (RTX) for planning pregnancy is associated with low disease reactivation. Whether this strategy reduces the risk of disease reactivity as compared with suspending natalizumab (NTZ) 3 months after conception is unclear.

METHODS

We retrospectively included women with MS followed in our department during pregnancy and 1 year after birth who suspended NTZ at the end of the first trimester (option mostly proposed before 2016) or suspended RTX/ocrelizumab (RTX/OCR) in the year before conception (option proposed since 2016).

RESULTS

In women who suspended NTZ, 45 pregnancies resulted in 3 miscarriages and 42 live births, including 1 newborn with major malformations. In women who suspended RTX/OCR, 37 pregnancies resulted in 3 miscarriages and 33 live births; 1 pregnancy was terminated for malformation. During pregnancy, relapse occurred in 3/42 (7.1%) patients of the NTZ group and 1/33 (3%) of the RTX/OCR group (p = 0.6). After delivery, relapse occurred in 9/42 (21.4%) patients of the NTZ group and 0/33 of the RTX/OCR group (p < 0.01). In the NTZ group, 8/9 relapses occurred in patients who restarted NTZ less than 4 weeks after delivery. The proportion of patients with gadolinium-enhanced and/or new T2 lesions on brain or spinal cord MRI performed after delivery was higher in the NTZ than RTX/OCR group (14/40 [35%] vs 1/31 [3%] patients, p = 0.001), the proportion with EDSS score progression during the period including pregnancy and the year after delivery was higher (7/42 [17%] vs 0/33 patients, p = 0.01), and the proportion fulfilling NEDA-3 during this period was lower (21/40 [53%] vs 30/31 [97%] patients, p < 0.001).

DISCUSSION

Suspending RTX/OCR in the year before conception in women with highly active MS was associated with no disease reactivation during and after pregnancy. As previously reported, stopping NTZ at the end of the first trimester was associated with disease reactivation. In women receiving NTZ who are planning pregnancy, a bridge to RTX/OCR for pregnancy or continuing NTZ until week 34 are both reasonable clinical decisions. The RTX/OCR option is more comfortable for women and reduces the exposure of infants to monoclonal antibodies.

Epigenetic Immune Cell Counting to Analyze Potential Biomarkers in Preterm Infants: A Proof of Principle in Necrotizing Enterocolitis

Epigenetic immune cell counting is a DNA (de)methylation-based technique which can be used to quantify lymphocyte subsets on dried blood spots (DBS). The foregoing techniques allow for a retrospective investigation of immune cell profiles in newborns. In this study, we used this technique for determining lymphocyte subcounts as a potential biomarker for necrotizing enterocolitis (NEC). We investigated whether this technique can be implemented in the field of neonatology, by testing whether regulatory T cell (Treg) levels are pre-existently low in preterms with NEC. Newborn screening (NBS) cards from 32 preterms with NEC and 32 age- and weight-matched preterm controls, and 60 healthy term newborns, were analyzed. Relative and absolute cell counts were determined for CD3+, CD4+, CD8+, Th17, and Treg T cells. For both relative and absolute cell counts of CD3+, CD4+, CD8+, and Th17 T cells, significant differences were found between healthy term controls and both preterm groups, but not between preterm groups. For Tregs, no significant differences were found in either relative or absolute counts between any of the newborn groups. This study demonstrates the principle of epigenetic immune cell counting to analyze lymphocyte subsets in preterm neonates.

Newborn Screening in the Diagnosis of Primary Immunodeficiency

Newborn screening for severe combined immune deficiency (SCID) is the first inborn error of immunity (IEI) to be detected through population screening. It also represents the first newborn screening test to utilize molecular testing on DNA from newborn dried blood spots. Newborn screening for SCID has provided opportunities to measure the population prevalence of this disorder and evaluate the effect of early interventions on the overall outcomes in affected infants. The success of SCID newborn screening has increased interest in developing and implementing molecular testing for other clinically significant inborn errors of immunity. This methodology has been adapted to screen for another monogenic inborn defect, spinal muscle atrophy. Advances in the clinical care and new therapeutics for many inborn errors of immunity support the need for early diagnosis and prompt institution of therapies to reduce morbidity and mortality. Early diagnosis may also improve the quality of life for affected patients. This article provides an overview of newborn screening for SCID, recommended steps for follow-up testing and early intervention as well as long-term follow-up. Numerous challenges remain, including the development of clinical consensus regarding confirmatory and diagnostic testing, early interventions, and best practices for immune reconstitution in affected infants.

Normal B cell ranges in infants: A systematic review and meta-analysis

BACKGROUND

During the first year of life, B cell level is a valuable indicator of whether external factors, such as exposure to B cell depleting therapies, have an adverse impact on immune system development. However, there are no standard reference ranges of B cell levels in healthy infants by age.

OBJECTIVE

To estimate the normal range of B cell levels in infants, by age, during the first year of life, by pooling data from published studies.

METHODS

Studies reporting B cell levels measured using flow cytometry and CD19 markers in healthy infants were identified via a systematic literature review. Quality and feasibility assessments determined suitability for inclusion in meta-analyses by age group and/or continuous age. Means and normal ranges (2.5th-97.5th percentile) were estimated for absolute and percentage B cell levels. Sensitivity analyses assessed the impact of various assumptions.

RESULTS

Of 37 relevant studies identified, 28 were included in at least 1 meta-analysis. Means and normal ranges of B cell levels were found to be 707 (123-2324) cells/μL in cord blood, 508 (132-1369) cells/μL at age 0-1 month, 1493 (416-3877) cells/μL at age 1-6 months and 1474 (416-3805) cells/μL at age >6 months. The continuous age model showed that B cell levels peaked at week 26. Trends were similar for the percentage B cell estimates and in sensitivity analyses.

CONCLUSION

These meta-analyses provide the first normal reference ranges for B cell levels in infants, by week of age, during the first year of life.

Can we identify WHIM in infancy? Opportunities with the public newborn screening process

Newborn screening (NBS) for severe combined immunodeficiency (SCID) utilizing T-cell receptor excision circles (TRECs) has been implemented in all 50 states as of December 2018 and has been transformative for the clinical care of SCID patients. Though having high sensitivity for SCID, NBS-SCID has low specificity, therefore is able to detect other causes of lymphopenia in newborns including many inborn errors of immunity (IEIs). In a recent study, three of six newborns later diagnosed with Warts, Hypogammaglobulinemia, Infections, and Myelokathexis (WHIM) syndrome were found to have a low TRECs and lymphopenia at birth. This presents an opportunity to increase the detection and diagnosis of WHIM syndrome by NBS-SCID with immunological follow-up along with a combination of flow cytometry for immune cell subsets, absolute neutrophil count, and genetic testing, extending beyond the conventional bone marrow studies. Coupled with emerging technologies such as next-generation sequencing, transcriptomics and proteomics, dried blood spots used in NBS-SCID will promote earlier detection, diagnosis, and therefore treatment of IEIs such as WHIM syndrome.

Premature Infants Have Normal Maturation of the T Cell Receptor Repertoire at Term

Premature infants are known to have immature immune systems compared to term infants; however, the impacts of ex utero immune development are not well characterized. Our previous retrospective clinical review showed prolonged T cell lymphopenia in a subset of extremely premature infants, suggesting that they may have lasting abnormalities in their T cell compartments. We used T cell receptor (TCR) repertoire sequencing to analyze the composition of the T cell compartment in premature and term infants in our NICU. We collected twenty-eight samples from individual subjects and analyzed the number of clonotypes, repertoire diversity, CDR3 length, and V gene usage between groups based on gestational age at birth and postmenstrual age at the time of sample collection. Further, we examined the TCR repertoire in infants with severe bronchopulmonary dysplasia (BPD) and those with abnormal T cell receptor excision circle (TREC) assays. Former extremely premature infants who were corrected to term postmenstrual age had TCR repertoire diversity that was more similar to term born infants than extremely premature infants, supporting normal maturation of the repertoire. Infants with severe BPD did not appear to have increased abnormalities in repertoire diversity. Decreased TCR repertoire diversity was associated with repeatedly abnormal TREC screening, although the diversity was within the normal range for subjects without low TRECs. This study suggests that extremely premature infants demonstrate normal maturation of the T cell repertoire ex utero. Further work is needed to better characterize postnatal T cell development and function in this population.

Inborn Errors of Immunity in the Premature Infant: Challenges in Recognition and Diagnosis

Due to heightened awareness and advanced genetic tools, inborn errors of immunity (IEI) are increasingly recognized in children. However, diagnosing of IEI in premature infants is challenging and, subsequently, reports of IEI in premature infants remain rare. This review focuses on how common disorders of prematurity, such as sepsis, necrotizing enterocolitis, and bronchopulmonary dysplasia, can clinically overlap with presenting signs of IEI. We present four recent cases from a single neonatal intensive care unit that highlight diagnostic dilemmas facing neonatologists and clinical immunologists when considering IEI in preterm infants. Finally, we present a conceptual framework for when to consider IEI in premature infants and a guide to initial workup of premature infants suspected of having IEI.

Establishing Newborn Screening for SCID in the USA; Experience in California

Newborn screening for severe combined immunodeficiency (SCID) has developed from the realization that infants affected with SCID require prompt diagnosis and treatment to avoid fatal infectious complications. Screening DNA from infant dried blood spots for T-cell receptor excision circles (TRECs), byproducts of normal antigen-receptor gene rearrangement, has proven to be a reliable method to identify infants with SCID and other serious T lymphocyte defects before the onset of serious infections. The experience of the SCID newborn screening program in California after screening over 3 million infants demonstrates the effectiveness of this measure.

Characteristics of immune function of full-term infants with different feeding patterns at the age of 3 months: a prospective cohort study

OBJECTIVES

To explore the characteristics of immune function of healthy full-term infants at the age of 3 months, and to analyze the relationship of immune function with feeding pattern and sex.

METHODS

A total of 84 healthy full-term infants born in four hospitals in Beijing and Hohhot, China were prospectively recruited. Their feeding patterns remained unchanged within 4 months after birth. They were divided into a breast-feeding group and a milk powder feeding group according to their feeding patterns. At the age of 3 months after birth, peripheral venous blood samples of the two groups were collected to evaluate cellular immunity and humoral immunity and perform routine blood test. The laboratory indices were compared between infants with different feeding patterns and sexes.

RESULTS

Compared with the milk powder feeding group, the breast-feeding group had significantly lower proportion of T cell second signal receptor CD28, immunoglobulin M, and proportion and absolute count of neutrophils (P<0.05) and significantly higher expression and proportion of HLA-DR, a surface activation marker of CD8⁺ T cells, and proportion of lymphocytes (P<0.05). The male infants had a significantly lower white blood cell count and a significantly higher proportion of eosinophils compared with the female infants (P<0.05).

CONCLUSIONS

Sex has no significant effect on the proportion of lymphocyte subsets in 3-month-old full-term infants, but feeding patterns are associated with the proportion of CD28⁺ T cells (lymphocyte functional subset) and HLA-DR⁺ T cells (lymphocyte activation subset), suggesting that feeding patterns have a certain effect on the development of immune function in 3-month-old full-term infants.

First Year of TREC-Based National SCID Screening in Sweden

Screening for severe combined immunodeficiency (SCID) was introduced into the Swedish newborn screening program in August 2019 and here we report the results of the first year. T cell receptor excision circles (TRECs), kappa-deleting element excision circles (KRECs), and actin beta (ACTB) levels were quantitated by multiplex qPCR from dried blood spots (DBS) of 115,786 newborns and children up to two years of age, as an approximation of the number of recently formed T and B cells and sample quality, respectively. Based on low TREC levels, 73 children were referred for clinical assessment which led to the diagnosis of T cell lymphopenia in 21 children. Of these, three were diagnosed with SCID. The screening performance for SCID as the outcome was sensitivity 100%, specificity 99.94%, positive predictive value (PPV) 4.11%, and negative predictive value (NPV) 100%. For the outcome T cell lymphopenia, PPV was 28.77%, and specificity was 99.95%. Based on the first year of screening, the incidence of SCID in the Swedish population was estimated to be 1:38,500 newborns.

Newborn Screening for Severe Combined Immunodeficiency: Do Preterm Infants Require Special Consideration?

The Wisconsin Newborn Screening (NBS) Program began screening for severe combined immunodeficiency (SCID) in 2008, using real-time PCR to quantitate T-cell receptor excision circles (TRECs) in DNA isolated from dried blood NBS specimens. Prompted by the observation that there were disproportionately more screening-positive cases in premature infants, we performed a study to assess whether there is a difference in TRECs between full-term and preterm newborns. Based on de-identified SCID data from 1 January to 30 June 2008, we evaluated the TRECs from 2510 preterm newborns (gestational age, 23-36 weeks) whose specimens were collected ≤72 h after birth. The TRECs from 5020 full-term newborns were included as controls. The relationship between TRECs and gestational age in weeks was estimated using linear regression analysis. The estimated increase in TRECs for every additional week of gestation is 9.60%. The 95% confidence interval is 8.95% to 10.25% (p ≤ 0.0001). Our data suggest that TRECs increase at a steady rate as gestational age increases. These results provide rationale for Wisconsin's existing premature infant screening procedure of recommending repeat NBS following an SCID screening positive in a premature infant instead of the flow cytometry confirmatory testing for SCID screening positives in full-term infants.

Neonatal lymphocyte subpopulations analysis and maternal preterm premature rupture of membranes: a pilot study

OBJECTIVES

Preterm premature rupture of membranes (pPROM) causes preterm delivery, and increases maternal T-cell response against the fetus. Fetal inflammatory response prompts maturation of the newborn's immunocompetent cells, and could be associated with unfavorable neonatal outcome. The aims were (1) to examine the effects of pPROM on the newborn's and mother's immune system and (2) to assess the predictive value of immune system changes in neonatal morbidity.

METHODS

Mother-newborn pairs (18 mothers and 23 newborns) who experienced pPROM and controls (11 mothers and 14 newborns), were enrolled. Maternal and neonatal whole blood samples underwent flow cytometry to measure lymphocyte subpopulations.

RESULTS

pPROM-newborns had fewer naïve CD4 T-cells, and more memory CD4 T-cells than control newborns. The effect was the same for increasing pPROM latency times before delivery. Gestational age and birth weight influenced maturation of the newborns' lymphocyte subpopulations and white blood cells, notably cytotoxic T-cells, regulatory T-cells, T-helper cells (absolute count), and CD4/CD8 ratio. Among morbidities, fewer naïve CD8 T-cells were found in bronchopulmonary dysplasia (BPD) (p=0.0009), and more T-helper cells in early onset sepsis (p=0.04).

CONCLUSIONS

pPROM prompts maturation of the newborn's T-cell immune system secondary to antigenic stimulation, which correlates with pPROM latency. Maternal immunity to inflammatory conditions is associated with a decrease in non-major histocompatibility complex (MHC)-restricted cytotoxic cells.

Dysfunctional Immune System Reconstitution After Rituximab Exposure In Utero

Rituximab is an antibody that binds to B-lymphocytes and is increasingly used during pregnancy. As an immunoglobulin G, it will transfer across the placenta. Previous case reports describe a diversity of clinical presentations in neonates born following rituximab exposure in utero. Our case is the first to offer the long-term experience in the care of an infant with severe neutropenia and prolonged profound hypogammaglobulinemia and class-switching B cell defect after in utero rituximab exposure.

Immunity and Genetics at the Revolving Doors of Diagnostics in Primary Immunodeficiencies

Primary immunodeficiencies (PIDs) are a large and growing group of disorders commonly associated with recurrent infections. However, nowadays, we know that PIDs often carry with them consequences related to organ or hematologic autoimmunity, autoinflammation, and lymphoproliferation in addition to simple susceptibility to pathogens. Alongside this conceptual development, there has been technical advancement, given by the new but already established diagnostic possibilities offered by new genetic testing (e.g., next-generation sequencing). Nevertheless, there is also the need to understand the large number of gene variants detected with these powerful methods. That means advancing beyond genetic results and resorting to the clinical phenotype and to immunological or alternative molecular tests that allow us to prove the causative role of a genetic variant of uncertain significance and/or better define the underlying pathophysiological mechanism. Furthermore, because of the rapid availability of results, laboratory immunoassays are still critical to diagnosing many PIDs, even in screening settings. Fundamental is the integration between different specialties and the development of multidisciplinary and flexible diagnostic workflows. This paper aims to tell these evolving aspects of immunodeficiencies, which are summarized in five key messages, through introducing and exemplifying five clinical cases, focusing on diseases that could benefit targeted therapy.

Primary immunodeficiency testing in a Massachusetts tertiary care NICU: persistent challenges in the extremely premature population

BACKGROUND

Prematurity presents a diagnostic challenge in interpreting primary immunodeficiency (PID) testing.

METHODS

We retrospectively reviewed the charts of all infants in our level IV referral neonatal intensive care unit (NICU) in Massachusetts, with immunologic testing performed from 2006 to 2018.

RESULTS

The overall rate of PID testing was enriched in our population, with 1% of admitted patients having extended immunologic testing. The addition of TREC (T cell receptor excision circle) newborn screening in Massachusetts in 2009 increased the proportion of infants tested for PID in our NICU by 3-fold (1.21% post-newborn screening (NBS) vs. 0.46% pre-NBS). A majority of the term and late preterm (≥34 weeks) infants (31 of 41, 76%), as well as very premature (29-33 weeks) infants (12 of 17, 71%), who had immune testing, had a genetic diagnosis associated with secondary immunodeficiency or a PID. Most infants who were born extremely premature (EP, <29 weeks) (25 of 29, 86%) had no identifiable cause of immunodeficiency besides prematurity, despite a mean postmenstrual age of 40.1 weeks at the time of testing.

CONCLUSIONS

Persistent immune derangements were present within a subgroup of the EP population through term postmenstrual age. EP infants with significant infectious history and abnormal immune testing at term-corrected age should be considered for genetic testing.

IMPACT

The role of immunologic testing in the premature population is unclear, we therefore reviewed the records of all infants in our NICU who had immunologic testing, to rule out immunodeficiency, done from 2006 to 2018. The addition of newborn screening for SCID in 2009 doubled the number of infants who had immune investigations. The extremely premature cohort included many infants with persistent immune derangements through term-corrected gestational age, suggesting a persistent effect of prematurity on immune development and potential function. We propose that former premature infants with clinical evidence of immunodeficiency and sustained immune abnormalities by term-corrected age undergo genetic testing for immunodeficiency.

When Screening for Severe Combined Immunodeficiency (SCID) with T Cell Receptor Excision Circles Is Not SCID: a Case-Based Review

Newborn screening efforts focusing on the quantification of T cell receptor excision circles (TRECs), as a biomarker for abnormal thymic production of T cells, have allowed for the identification and definitive treatment of severe combined immunodeficiency (SCID) in asymptomatic neonates. With the adoption of TREC quantification in Guthrie cards across the USA and abroad, typical, and atypical SCID constitutes only ~ 10% of cases identified with abnormal TRECs associated with T cell lymphopenia. Several other non-SCID-related conditions may be identified by newborn screening in a term infant. Thus, it is important for physicians to recognize that other factors, such as prematurity, are often associated with low TRECs initially, but often improve with age. This paper focuses on a challenge that immunologists face: the diagnostic evaluation and management of cases in which abnormal TRECs are associated with variants of T cell lymphopenia in the absence of a genetically defined form of typical or atypical SCID. Various syndromes associated with T cell impairment, secondary forms of T cell lymphopenia, and idiopathic T cell lymphopenia are identified using this screening approach. Yet there is no consensus or guidelines to assist in the evaluation and management of these newborns, despite representing 90% of the patients identified, resulting in significant work for the clinical teams until a diagnosis is made. Using a case-based approach, we review pearls relevant to the evaluation of these newborns, as well as the management dilemmas for the families and team related to the resolution of genetic ambiguities.

SCID newborn screening: What we've learned

Newborn screening for severe combined immunodeficiency, the most profound form of primary immune system defects, has long been recognized as a measure that would decrease morbidity and improve outcomes by helping patients avoid devastating infections and receive prompt immune-restoring therapy. The T-cell receptor excision circle test, developed in 2005, proved to be successful in pilot studies starting in the period 2008 to 2010, and by 2019 all states in the United States had adopted versions of it in their public health programs. Introduction of newborn screening for severe combined immunodeficiency, the first immune disorder accepted for population-based screening, has drastically changed the presentation of this disorder while providing important lessons for public health programs, immunologists, and transplanters.

Characterization of Infants with Idiopathic Transient and Persistent T Cell Lymphopenia Identified by Newborn Screening-a Single-Center Experience in New York State

PURPOSE

Newborn screening (NBS) quantifies T cell receptor excision circles (TREC) and identifies infants with T cell lymphopenia (TCL). This study elucidates the demographics, laboratory characteristics, genetics, and clinical outcomes following live viral vaccine administration of term infants with transient or persistent idiopathic TCL.

METHODS

A single-center retrospective analysis was performed from September 2010 through June 2018. Laboratory variables were compared with Mann-Whitney tests. Correlations between initial TREC levels and T cell counts were determined by Spearman tests.

RESULTS

Twenty-two transient and 21 persistent TCL infants were identified. Males comprised 68% of the transient and 52% of the persistent TCL cohorts. Whites comprised 23% of the transient and 29% of the persistent cohorts. Median initial TREC levels did not differ (66 vs. 60 TRECs/μL of blood, P = 0.58). The transient cohort had higher median initial CD3⁺ (2135 vs. 1169 cells/μL, P < 0.001), CD4⁺ (1460 vs. 866 cells/μL, P < 0.001), and CD8⁺ (538 vs. 277 cells/μL, P < 0.001) counts. The median age of resolution for the transient cohort was 38 days. Genetic testing revealed 2 genes of interest which warrant further study and several variants of uncertain significance in immunology-related genes in the persistent cohort. 19 transient and 14 persistent subjects received the initial rotavirus and/or MMRV immunization. No adverse reactions to live viral vaccines were reported in either cohort.

CONCLUSION

Transient and persistent TCL infants differ by demographic, laboratory, and clinical characteristics. Select transient and persistent TCL patients may safely receive live attenuated viral vaccines, but larger confirmatory studies are needed.

Delivery Modality Affect Neonatal Levels of Inflammation, Stress, and Growth Factors

Introduction: As part of the study CODIBINE, Correlations and Diagnoses for Biomarkers in New-borns, the main objective of the study was to explore neonatal inflammation, stress, neurodevelopment, and growth factors after in-labor and pre-labor cesarean section compared to vaginal delivery. Increasing evidence has shown that birth delivery mode has an impact on imminent and long-term child health. However, the effect of the timing of cesarean section is insufficiently elucidated. The main objective of the study was to explore the effect of different delivery modes, vaginal delivery compared to cesarean section with or without initiation of labor, on the infants. Methods: We designed a retrospective cohort study, including dried blood spot samples from mature (gestational age ≥ 37) newborns delivered in the years 2009-2011. The newborns were divided into three groups after delivery mode: (1) pre-labor cesarean section (n = 714), i.e., cesarean delivery without initiation of labor, (2) in-labor cesarean section (n = 655), i.e., cesarean section after initiation of labor, and (3) vaginal delivery (n = 5,897). We measured infant levels of inflammatory (IL-18, MCP-1, CRP, sTNF RI), stress (HSP-70), growth (EGF, VEGF-A), and neurotrophic factors (BDNF, NT-3, S100B) 2-4 days after birth. Results: The neonatal levels of inflammatory and stress markers were significantly lower, while the levels of growth factors were higher after pre-labor cesarean section compared to vaginal delivery. The biomarker levels were similar after in-labor cesarean section and vaginal delivery. Removing cases with pre-labor rupture of membranes and artificial rupture of membranes in the calculations did not change the results. The levels of neurotrophic factors were unaffected by delivery form. Males had generally higher levels of inflammation and lower levels of growth and neurotrophic factors. Overall, the levels of inflammatory markers increased, and the growth factors decreased with increasing gestational age. Conclusion: The present study of the biomarker levels after birth suggests that the labor process has an important effect on the fetal immune system and level of stress, regardless if the delivery ends with cesarean section or vaginal birth.

Epigenetic Dynamics of the Infant Immune System Reveals a Tumor Necrosis Factor Superfamily Signature in Early Human Life

DNA methylation (DNAm) is an essential mechanism governing normal development in humans. Although most DNAm patterns in blood cells are established in utero, the genes associated with immune function undergo postnatal DNAm modifications, and the characterization of this subset of genes is incomplete. Accordingly, we used available longitudinal DNAm datasets from a large birth cohort in the U.S. to further identify postnatal DNAm variation in peripheral leukocytes from 105 children (n = 105) between birth and the first two years of life, as determined by postnatal changes in β values (with the percentage of methylation ranging from 0 to 1.0 at individual CpG sites). Our study is an extension of a previous analysis performed by our group and identified that: (1) as previously described, DNAm patterns at most CpG sites were established before birth and only a small group of genes underwent DNAm modifications postnatally, (2) this subset includes multiple immune genes critical for lymphocyte development, and (3) several members of the tumor necrosis factor receptor and cytokine superfamilies with essential roles in immune cell activation, survival, and lymphoid tissue development were among those with a larger postnatal variation. This study describes the precise epigenetic DNA methylation marks in important immune genes that change postnatally and raises relevant questions about the role of DNAm during postnatal immune development in early childhood.

The immunologic status of newborns born to SARS-CoV-2-infected mothers in Wuhan, China

BACKGROUND

Immunologic dysfunction due to coronavirus disease 2019 (COVID-19) is closely related to clinical prognosis, and the inflammatory response of pregnant women may affect the directional differentiation and function of fetal immune cells.

OBJECTIVE

We sought to analyze the immune status of newborns from mothers with COVID-19 in the third trimester.

METHODS

Along with collecting the clinical data from 51 newborns and their respective mothers, we recorded the immunophenotypes and cytokine and immunoglobulin levels of the newborns.

RESULTS

None of the 51 newborns showed fever or respiratory distress during hospitalization. Detection of severe acute respiratory syndrome coronavirus 2 nucleic acid in pharyngeal swabs was negative. Except for the low level of CD16-CD56 cells, the count and proportion of lymphocytes, CD3, CD4, CD8, and CD19 were all in the normal range. Moreover, the serum IgG and IgM levels were within the normal range, whereas IL-6 showed increased levels. There was no correlation between maternal COVID-19 duration and the lymphocyte subsets or cytokine levels (IFN-γ, IL-2, IL-4, IL-6, IL-10, and TNF-α). There was a positive correlation between IL-6 and IL-10 levels and CD16-CD56 cells. One (1.96%) infant with an extremely elevated IL-6 concentration developed necrotizing enterocolitis in the third week after birth, and the remaining 50 infants did not show abnormal symptoms through the end of the follow-up period.

CONCLUSIONS

COVID-19 in the third trimester did not significantly affect the cellular and humoral immunity of the fetus, and there was no evidence that the differentiation of lymphocyte subsets was seriously unbalanced.

Follow-Up for an Abnormal Newborn Screen for Severe Combined Immunodeficiencies (NBS SCID): A Clinical Immunology Society (CIS) Survey of Current Practices

Severe combined immunodeficiency (SCID) includes a group of monogenic disorders presenting with severe T cell lymphopenia (TCL) and high mortality, if untreated. The newborn screen (NBS) for SCID, included in the recommended universal screening panel (RUSP), has been widely adopted across the US and in many other countries. However, there is a lack of consensus regarding follow-up testing to confirm an abnormal result. The Clinical Immunology Society (CIS) membership was surveyed for confirmatory testing practices for an abnormal NBS SCID result, which included consideration of gestational age and birth weight, as well as flow cytometry panels. Considerable variability was observed in follow-up practices for an abnormal NBS SCID with 49% confirming by flow cytometry, 39% repeating TREC analysis, and the remainder either taking prematurity into consideration for subsequent testing or proceeding directly to genetic analysis. More than 50% of respondents did not take prematurity into consideration when determining follow-up. Confirmation of abnormal NBS SCID in premature infants continues to be challenging and is handled variably across centers, with some choosing to repeat NBS SCID testing until normal or until the infant reaches an adjusted gestational age of 37 weeks. A substantial proportion of respondents included naïve and memory T cell analysis with T, B, and NK lymphocyte subset quantitation in the initial confirmatory panel. These results have the potential to influence the diagnosis and management of an infant with TCL as illustrated by the clinical cases presented herein. Our data indicate that there is clearly a strong need for harmonization of follow-up testing for an abnormal NBS SCID result.

Retrospective Analysis of a New York Newborn Screen Severe Combined Immunodeficiency Referral Center

In 2010, the New York State (NYS) Newborn Screen (NBS) Program added the T cell receptor excision circle (TREC) assay to screen for severe combined immunodeficiency disorder (SCID). The objective of this study was to perform a retrospective chart review of 199 infants referred to a single institution for abnormal TREC on NYS NBS between 2010 and 2017. Statistical analysis included analysis of variance, logistic regression models, chi-square, and linear mixed models. One hundred ninety-nine infants were found to have a TREC value of fewer than 200 copies/μL on NYS NBS. Infants were stratified as primary immunodeficiency (PID) (n = 54), immunocompetent (n = 133), lost to follow-up (n = 8), or deceased (n = 4). PID included SCID (n = 3), DiGeorge (n = 6), idiopathic lymphopenia (IL) (n = 44), and other syndromes associated with lymphopenia (n = 3). The 3 SCID cases were identified and brought to treatment, although all experienced significant infections. The study population was found to be predominately non-Hispanic, African American, and male. There was a difference in the average TREC values among those with immunocompetence (83 copies/μL), IL (81 copies/μL), and PID (40 copies/μL) (p < 0.05). On follow-up of 40 patients with IL, patients typically did not have severe infections during first few years of life. This study demonstrates that TREC value can be used to stratify infants for further confirmatory testing to exclude PID. Risk factors, such as stressful prenatal/postnatal conditions, prematurity, race, and sex may affect TREC value but cannot explain all causes of lymphopenia. This study may assist providers in risk stratifying the likelihood of PID with an abnormal TREC and determining the extent of the initial work up that is necessary at the time of a newborn's presentation.