Update on Transplacental Transfer of IgG Subclasses: Impact of Maternal and Fetal Factors

Acquired hemophilia A: a narrative review and management approach in the emicizumab era

Acquired hemophilia A (AHA) is a rare bleeding disorder caused by inhibitory autoantibodies to factor (F)VIII. The goals of treatment are 2-fold, namely immunosuppressive therapy to eradicate the inhibitor and hemostatic management to control bleeding. Emicizumab, a bispecific antibody that acts as a FVIIIa-mimetic, has seen growing use in AHA following its approval for congenital hemophilia A. This review provides an overview of the epidemiology, pathophysiology, diagnosis, and treatment of AHA. Registry, trial, and case series data are assimilated and summarized with an emphasis on a standardized approach that integrates the use of emicizumab. With recent registry data suggesting the need to focus on immunosuppression-related mortality in AHA, we provide treatment recommendations in an algorithmic format that have become the standard of care at our institution. These recommendations are intended to minimize hemostatic product usage and potential toxicity related to immunosuppressive therapy while reducing morbidity and rehospitalization rates for bleeding. The proposed treatment algorithm, which includes key interventions by phase of therapy, can be readily implemented at centers that have rapid access to plasma FVIII activity using a one-stage assay. A case is presented to illustrate the proposed diagnostic and management considerations.

Transplacental Antibodies: Role of Maternal Vaccines and Immunity

Transplacental transfer of maternal antibody in utero is a key component of neonatal immunity. This transfer of maternal antibody across the placenta provides temporary protection from bacterial and viral pathogens that threaten newborn health. Maternal vaccination before and during pregnancy may be used to boost maternal immunity and optimize neonatal protection from infection and serious illness.

Sex-specific association of immunological markers in CS-delivered newborns with pre-pregnancy body mass index and gestational weight gain of mothers

Just as overweight and obesity may impair immunity, excessive body weight-related parameters of women in the pre-conception period and during pregnancy are possible detrimental factors for fetal programming of the immune system in their offspring. We investigated the relationship of pre-pregnancy body mass index (pBMI) and gestational weight gain (GWG) of mothers with the placental transport rate (PTR) of IgG antibodies and antineutrophil cytoplasmatic antibodies against lactoferrin (Lf-ANCA) and their concentration in umbilical cord blood serum (UCS), verifying the sex-specificity of this relationship. The examined group of this cross-sectional pilot study consisted of 101 pregnant women and their healthy CS-delivered newborn children. The concentration of antibodies in maternal serum (MS) and UCS were determined by ELISA method. PTR was assessed as a ratio of the concentration of antibodies in the UCS and MS. A significantly lower PTR of IgG and their concentration in the UCS were demonstrated in newborns of mothers with an excessive pBMI compared to those with pBMI < 25 and the association was more pronounced in male newborns. The lowest PTR of beneficial IgG and their concentration in the UCS as well as the highest PTR of detrimental Lf-ANCA and their concentration in UCS were observed in newborns born to mothers with co-occurrence of both an excessive pBMI and GWG. It seems that maternal preconception overweight and obesity along with an excessive GWG can be a predictor of unfavorable immune effects in fetuses. Further studies are needed to explain the role of maternal weight-related parameters in the development of immunological health of their offspring.

Molecular and cellular morphology of placenta unveils new mechanisms of reproductive immunology

INTRODUCTION

Despite of numerous studies of the placenta, some molecular and cellular characteristics, particularly the relationship among different cell types, have not been well understood. We aim to investigate the basic and intricate details of cellular and molecular elements in early and late phase placentas to gain better understanding of the immune regulation of human reproductive process.

METHODS

A novel combination of techniques of spatial transcriptomics(ST), multiple immunohistochemistry, and a dual labeling combining immunohistochemistry and (fluorescence in situ hybridization) FISH on normal and ectopic pregnancy and animal models was employed to investigate the placenta at tissue, cell, protein and molecular levels and to trace the fetal and maternal origin of every cell in early and late placentas.

RESULTS

Original discoveries include early expression of immune checkpoint proteins in embryo trophoblasts even before implantation. The detailed distributional relationships among different cell types of fetal and maternal origins in placenta and decidua indicate an immune rejection of the mother towards the fetus and this was counterbalanced by immune inhibitory proteins and blocking antibody Immunoglobulin G4 (IgG4) at the junction between the fetus and the mother. In contrary to common believe, we found that vascular endothelial and glandular epithelial cells in the decidua remain maternal in origin and were not replaced by fetal cells. At term placenta, fetal immune cells infiltrated into the maternal side of the decidus and vice versa indicating a possible immune reaction between fetal and maternal immune systems and suggesting a possible immune mechanism for trigger of parturition. The ability of trophoblasts to create an immune suppressed environment was also supported by findings in ectopic pregnancy and the animal models.

CONCLUSION

The findings indicate a fetus-driven mechanism of immune balance involving both cellular and humoral immunity in human reproduction.

The recent landscape of RSV vaccine research

Respiratory syncytial virus (RSV) causes a significant burden of acute respiratory illness across all ages, particularly for infants and older adults. Infants, especially those born prematurely or with underlying health conditions, face a high risk of severe RSV-related lower respiratory tract infections (LRTIs). Globally, RSV contributes to millions of LRTI cases annually, with a disproportionate burden in low- and middle-income countries (LMICs). The RSV virion outer capsule contains glycoproteins G and F which are essential for viral entry into respiratory epithelial cells and represent key targets for therapeutics development. The F-glycoprotein has several highly conserved antigenic sites that have proven useful targets for the development of monoclonal antibodies (mAbs) against RSV. Historically, prevention in infants was limited to the mAb palivizumab, which, despite its efficacy, was costly and inaccessible in many regions. Recent advancements include nirsevimab, a long-acting mAb that has shown substantial efficacy in reducing medically attended RSV-related disease in infants, in phase III clinical trials, early regional and national real-world data. In addition, three new vaccines have been approved: two protein subunit vaccines and a messenger RNA vaccine. The vaccines are all licenced for use in older adults, with one also approved as a maternal vaccine. Promising candidates in development include the mAb clesrovimab, which has an extended half-life and high levels in the nasal epithelial lining and high safety and efficacy profiles in late-stage trials. There are also a wide range of vaccine candidates currently in late-stage clinical trials. These developments signify a major advancement in RSV prevention strategies, offering improved protection for high-risk populations. With the ongoing rollout of the recently licenced vaccines and mAbs internationally, the landscape of RSV care is rapidly changing. We also must ensure these advances reach those in LMICs who need these therapies most.

Maternal and neonatal IgG against Klebsiella pneumoniae are associated with lower risk of neonatal sepsis: A case-control study of hospitalized neonates in Botswana

Sepsis is the leading postnatal cause of neonatal mortality worldwide. Globally Klebsiella pneumoniae is the leading cause of sepsis in hospitalized neonates. This study reports the development and evaluation of an ELISA for anti-Klebsiella IgG using dried blood spot (DBS) samples and evaluates the association of anti-Klebsiella IgG (anti-Kleb IgG) antibodies in maternal and neonatal samples with the risk of neonatal sepsis. Neonates and their mothers were enrolled at 0-96 hours of life in the neonatal unit of a tertiary referral hospital in Gaborone, Botswana and followed until death or discharge to assess for episodes of blood culture-confirmed neonatal sepsis. Neonates with sepsis had significantly lower levels of Kleb-IgG compared to neonates who did not develop sepsis (Mann-Whitney U, p = 0.012). Similarly, samples from mothers of neonates who developed sepsis tended to have less Kleb-IgG compared to mothers of controls. The inverse correlation between Kleb-IgG levels and all-cause bacteremia suggests that maternal Kleb-IgG may be protective through cross-reactivity with common bacterial epitopes. These data support the continued use of immunoglobulin assays using DBS samples to explore the role of passive immunity on neonatal sepsis risk and reaffirm the critical need for research supporting the development of maternal vaccines for neonatal sepsis.

Probiotic therapy as a promising strategy for gestational diabetes mellitus management

INTRODUCTION

Gestational diabetes mellitus (GDM) has become the most common pregnancy medical complication, and its prevalence has increased in recent years. The GDM treatment primarily relies on adopting healthy eating habits, physical exercise, and insulin therapy. However, using probiotics to modulate the gut microbiota has been the subject of clinical trials as a promising therapeutic strategy for GDM management.

AREAS COVERED

Due to the adverse effects of gut dysbiosis in women with GDM, strategies targeting the gut microbiota to mitigate hyperglycemia, low-grade inflammation, and adverse pregnancy outcomes have been explored. Probiotic supplementation may improve glucose metabolism, lipid profile, oxidative stress, inflammation, and blood pressure in women with GDM. Furthermore, decreased fasting blood glucose, insulin resistance, and inflammatory markers, such as TNF-α and CRP, as well as increased total antioxidant capacity, lipid profile modulation, and improved blood pressure in women with GDM, are some of the important results reported in the available literature.

EXPERT OPINION

To fill the knowledge gap, further studies are needed focusing on modulating gut microbiota composition and metabolic activity and their systemic repercussions in GDM.

Specific antibody responses to Qβ-displayed Plasmodium falciparum-derived UB05 and MSP3 proteins in mother-neonate couples

Malaria blood-stage parasite is a critical pathogenic stage responsible for serious adverse outcomes in pregnant women and their neonates. Immunoglobulin G (IgG) antibody responses specific to various asexual blood-stage antigens were well reported in non-pregnant individuals. However, little is still known during placental malaria. To assess the antibody responses specific to Plasmodium falciparum-derived MSP3 and UB05 malaria vaccine candidates in mother-neonate couples, mother's peripheral blood and neonate's cord blood samples were collected at delivery. After malaria diagnostic, plasma levels of IgG and IgG subclass responses specific to UB05, MSP3 and UB05-MSP3 were determined using ELISA. As outcomes, both mothers and neonates had significantly higher IgG responses to UB05 and UB05-MSP3 compared to anti-MSP3 IgG (p < 0.05), irrespective of malaria status. Significant negative correlations were observed between IgG levels specific to the three antigens and parasitaemia (p < 0.01). Anti-UB05 and anti-UB05-MSP3 IgG levels in neonates showed a significant positive correlation with the corresponding mothers' antibodies (rs = 0.25 with p = 0.04; rs = 0.31 with p = 0.01, respectively). UB05MSP3-specific IgG3 and IgG1 subclass responses were significantly higher than the IgG4 subclass (p < 0.01). The neonates IgG1 and IgG3 levels positively correlated with the corresponding antibody subclasses of mothers. These findings suggest an association between UB05 and UB05-MSP3-specific antibody responses and malaria control during pregnancy. Maternal-foetal transfer of MSP3 and UB05-specific IgG occurs during pregnancy, suggesting the interest in the future malaria vaccination strategies in pregnant women to generate early protective immunity in baby against malaria.

Regulators of placental antibody transfer through a modeling lens

Infants are vulnerable to infections owing to a limited ability to mount a humoral immune response and their tolerogenic immune phenotype, which has impeded the success of newborn vaccination. Transplacental transfer of IgG from mother to fetus provides crucial protection in the first weeks of life, and maternal immunization has recently been implemented as a public health strategy to protect newborns against serious infections. Despite their early success, current maternal vaccines do not provide comparable protection across pregnancies with varying gestational lengths and placental and maternal immune features, and they do not account for the dynamic interplay between the maternal immune response and placental transfer. Moreover, progress toward the rational design of maternal vaccines has been hindered by inadequacies of existing experimental models and safety challenges of investigating longitudinal dynamics of IgG transfer in pregnant humans. Alternatively, in silico mechanistic models are a logical framework to disentangle the processes regulating placental antibody transfer. This Review synthesizes current literature through a mechanistic modeling lens to identify placental and maternal regulators of antibody transfer, their clinical covariates, and knowledge gaps to guide future research. We also describe opportunities to use integrated modeling and experimental approaches toward the rational design of vaccines against existing and emerging neonatal pathogen threats.

Optimizing lipid nanoparticles for fetal gene delivery in vitro, ex vivo, and aided with machine learning

There is a clinical need to develop lipid nanoparticles (LNPs) to deliver congenital therapies to the fetus during pregnancy. The aim of these therapies is to restore normal fetal development and prevent irreversible conditions after birth. As a first step, LNPs need to be optimized for transplacental transport, safety on the placental barrier and fetal organs and transfection efficiency. We developed and characterized a library of LNPs of varying compositions and used machine learning (ML) models to delineate the determinants of LNP size and zeta potential. Utilizing different in vitro placental models with the help of a Random Forest algorithm, we could identify the top features driving percentage LNP transport and kinetics at 24 h, out of a total of 18 input features represented by 41 LNP formulations and 48 different transport experiments. We further evaluated the LNPs for safety, placental cell uptake, transfection efficiency in placental trophoblasts and fetal lung fibroblasts. To ensure the integrity of the LNPs following transplacental transport, we screened LNPs for transport and transfection using a high-throughput integrated transport-transfection in vitro model. Finally, we assessed toxicity of the LNPs in a tracheal occlusion fetal lung explant model. LNPs showed little to no toxicity to fetal and placental cells. Immunoglobin G (IgG) orientation on the surface of LNPs, PEGylated lipids, and ionizable lipids had significant effects on placental transport. The Random Forest algorithm identified the top features driving LNPs placental transport percentage and kinetics. Zeta potential emerged in the top driving features. Building on the ML model results, we developed new LNP formulations to further optimize the transport leading to 622 % increase in transport at 24 h versus control LNP formulation. To induce preferential siRNA transfection of fetal lung, we further optimized cationic lipid percentage and the lipid-to-siRNA ratio. Studying LNPs in an integrated placental and fetal lung fibroblasts model showed a strong correlation between zeta potential and fetal lung transfection. Finally, we assessed the toxicity of LNPs in a tracheal occlusion lung explant model. The optimized formulations appeared to be safe on ex vivo fetal lungs as indicated by insignificant changes in apoptosis (Caspase-3) and proliferation (Ki67) markers. In conclusion, we have optimized an LNP formulation that is safe, with high transplacental transport and preferential transfection in fetal lung cells. Our research findings represent an important step toward establishing the safety and effectiveness of LNPs for gene delivery to the fetal organs.

Impact of Infections During Pregnancy on Transplacental Antibody Transfer

Vaccination in pregnancy is important to protect the mother and fetus from infectious diseases. The transfer of maternal antibodies across the placenta during pregnancy can continue to protect the neonate for several months after birth while the neonatal adaptive immune system develops. Several pathogens have been shown to impair the transplacental transfer of maternal antibodies, including human immunodeficiency virus, malaria, the severe acute respiratory syndrome coronavirus 2, and cytomegalovirus. This review discusses the mechanisms contributing to decreased transplacental antibody transfer in the setting of maternal infections, such as changes in antibody glycosylation profile, maternal hypergammaglobulinemia, and placental injury. The frequency of epidemics is increasing, and pregnant people are more likely to become exposed to novel pathogens now than they were in the past. Understanding the mechanisms by which infectious diseases impair maternal-fetal antibody transfer is important for pandemic preparedness to maximize the impact of maternal vaccination for child health.

On placental and lactational transfer of IgG-based therapeutic proteins - Current understanding and knowledge gaps from a clinical pharmacology perspective

Maternal medication use may expose the developing fetus through placental transfer or the infant through lactational transfer. Because pregnant and lactating individuals have been historically excluded from early drug development trials, there is often limited to no human data available to inform pharmacokinetics (PK) and safety in these populations at the time of drug approval. We describe the known mechanisms of placental or lactational transfer of IgG-based therapeutic proteins and use clinical examples to highlight the potential for fetal or infant exposure during pregnancy and lactation. Placental transfer of IgG-based therapeutic proteins may result in systemic exposure to the developing fetus. A lactational transfer may be associated with local gastrointestinal (GI) exposure in the infant and may also result in systemic exposure, although data are very limited as proteins have shown instability in the GI tract. Understanding of PK and pharmacodynamic (PD) effects of IgG-based therapeutic proteins in infants exposed in utero as well as the potential exposure through human milk and its clinical implications is critical for developing treatment strategies for pregnant or lactating individuals. We share the current knowledge gaps and considerations for future evaluations to inform PK, PD, and the safety of IgG-based therapeutic proteins for safe use during pregnancy and lactation. With the increasing use of IgG-based therapeutic proteins in treating chronic diseases during pregnancy and lactation, there is a need to improve the quantity and quality of data to inform the safe use in pregnant and lactating individuals.

Antibody-mediated protection against respiratory syncytial virus in children

Respiratory syncytial virus (RSV) is a major global pathogen, causing lower respiratory tract disease in at-risk populations including young children. Antibodies form a crucial layer of protection from RSV disease, particularly in immunologically naïve infants. Such antibodies are derived from the mother via transplacental transfer and breast milk, but may be particularly low in high-risk infants such as those born preterm. Maternally derived antibodies can now be supplemented by the administration of anti-RSV monoclonal antibodies, while a rising wave of maternal and paediatric vaccine strategies are approaching. The implementation of these prophylactics may profoundly decrease the healthcare burden of RSV. In this article, we review the role of antibody-mediated immunity in protecting children from RSV. We focus on maternally derived antibodies as the main source of protection against RSV and study factors that influence the scale of this transfer. The role of passive and active prophylactic approaches in protecting infants against RSV are discussed and knowledge gaps in our understanding of antibody-mediated protection against RSV are identified.

Surface protein distribution in Group B Streptococcus isolates from South Africa and identifying vaccine targets through in silico analysis

Group B Streptococcus (GBS) is a major cause of pneumonia, sepsis, and meningitis in infants younger than 3 months of age. Furthermore, GBS infection in pregnant women is associated with stillbirths and pre-term delivery. It also causes disease in immunocompromised adults and the elderly, but the highest incidence of the disease occurs in neonates and young infants. At this time, there are no licensed vaccines against GBS. Complete GBS genome sequencing has helped identify genetically conserved and immunogenic proteins, which could serve as vaccine immunogens. In this study, in silico reverse vaccinology method were used to evaluate the prevalence and conservation of GBS proteins in invasive and colonizing isolates from South African infants and women, respectively. Furthermore, this study aimed to predict potential GBS vaccine targets by evaluating metrics such as antigenicity, physico-chemical properties, subcellular localization, secondary and tertiary structures, and epitope prediction and conservation. A total of 648 invasive and 603 colonizing GBS isolate sequences were screened against a panel of 89 candidate GBS proteins. Ten of the 89 proteins were highly genetically conserved in invasive and colonizing GBS isolates, nine of which were computationally inferred proteins (gbs2106, SAN_1577, SAN_0356, SAN_1808, SAN_1685, SAN_0413, SAN_0990, SAN_1040, SAN_0226) and one was the surface Immunogenic Protein (SIP). Additionally, the nine proteins were predicted to be more antigenic than the SIP protein (antigenicity score of > 0.6498), highlighting their potential as GBS vaccine antigen targets.

Maternal Immunization with Adjuvanted Recombinant Receptor-Binding Domain Protein Provides Immune Protection against SARS-CoV-2 in Infant Monkeys

Maternal vaccinations administered prior to conception or during pregnancy enhance the immune protection of newborn infants against many pathogens. A feasibility experiment was conducted to determine if monkeys can be used to model the placental transfer of maternal antibody against SARS-CoV-2. Six adult rhesus monkeys were immunized with adjuvanted recombinant-protein antigens comprised of receptor-binding domain human IgG1-Fc fusion proteins (RBD-Fc) containing protein sequences from the ancestral-Wuhan or Gamma variants. The female monkeys mounted robust and sustained anti-SARS-CoV-2 antibody responses. Blood samples collected from their infants after delivery verified prenatal transfer of high levels of spike-specific IgG, which were positively correlated with maternal IgG titers at term. In addition, an in vitro test of ACE2 neutralization indicated that the infants' IgG demonstrated antigen specificity, reflecting prior maternal immunization with either Wuhan or Gamma-variant antigens. All sera showed stronger ACE2-RBD binding inhibition when variants in the assay more closely resembled the vaccine RBD sequence than with more distantly related variants (i.e., Delta and Omicron). Monkeys are a valuable animal model for evaluating new vaccines that can promote maternal and infant health. Further, the findings highlight the enduring nature and safety of the immune protection elicited by an adjuvanted recombinant RBD-Fc vaccine.

From Womb to World: Exploring the Immunological Connections between Mother and Child

Mother and child are immunologically interconnected by mechanisms that we are only beginning to understand. During pregnancy, multiple molecular and cellular factors of maternal origin are transferred across the placenta and influence the development and function of the fetal and newborn immune system. Altered maternal immune states arising from pregnancy-associated infections or immunizations have the potential to program offspring immune function in ways that may have long-term health consequences. In this study, we review current literature on the impact of prenatal infection and vaccination on the developing immune system, highlight knowledge gaps, and look to the horizon to envision maternal interventions that could benefit both the mother and her child.

Reduced anti-viral IgG repertoire in HIV-exposed but uninfected infants compared to HIV-unexposed infants

Infants who are HIV exposed but uninfected (iHEU) have higher risk of viral infections compared to infants who are HIV unexposed (iHUU). We explored the effect of intrauterine HIV exposure on the infant antibody repertoire by quantifying plasma immunoglobulin (Ig) G against 206 eukaryote-infecting viruses using phage immunoprecipitation sequencing (PhiPSeq) in iHEU and iHUU at birth and 36 weeks of life. Maternal HIV infection altered the infant IgG repertoire against eukaryote-infecting viruses at birth, resulting in significantly lower antibody breadth and diversity among iHEU compared to iHUU. Neonatal anti-viral IgG repertoire was dominated by antibodies against viruses belonging to the Herpesviridae family, although, by 36 weeks, this had shifted toward antibodies against enteroviruses, likely due to waning of maternal-derived antibodies and polio vaccine-induced antibody responses as expected. The observed reduced anti-viral IgG repertoire breadth and diversity acquired at birth in iHEU might contribute to the increased rates of viral infections among iHEU during early life.

Longer interval between maternal RSV vaccination and birth increases placental transfer efficiency

Background

Respiratory Syncytial Virus (RSV) is associated with significant neonatal and infant morbidity and mortality. Maternal bivalent RSVpreF RSV vaccination to protect neonates and infants was approved in September 2023 for administration between 32+0 and 36+6 weeks to protect neonates and infants. This approved timeframe is narrower than the 24-36 week window evaluated in the clinical trial, due to the possible association between preterm birth and vaccine administration. Currently, data are lacking on how maternal vaccine timing within the approved window affects the transfer of antibodies from mother to fetus, critical information that could influence clinical practice.

Objectives

We sought to examine how gestational age at vaccination and time elapsed from maternal RSV vaccination to delivery impacted transfer of maternal antibodies measured in the umbilical cord at delivery and in peripheral blood of 2-month infants. We also examined differences in maternal and cord RSV antibody levels achieved by vaccination versus natural RSV infection.

Study Design

A prospective cohort study was conducted at two academic medical centers between September 20, 2023 and March 21, 2024, enrolling 124 individuals who received the RSV vaccine during pregnancy. Infant capillary blood was collected at 2 months of age from 29 of the infants. Maternal and cord IgG levels achieved by RSV vaccination were compared to those associated with maternal natural RSV infection, using banked blood from 20 maternal:cord dyads collected prior to the availability of the maternal RSV vaccine. Levels of IgG against RSV strain A2 and B fusion (F) and attachment (G) proteins and against pertussis toxin (as a comparator antigen from a vaccine routinely administered earlier in pregnancy) were measured using a Binding Antibody Multiplex Assay. Differences in titers between vaccination and natural infection were examined using Wilcoxon rank sum test. Differences in cord:maternal transfer ratios and 2-month infant antibody levels by timing of maternal vaccination were evaluated by Kruskal-Wallis testing.

Results

Maternal RSV vaccination resulted in significantly higher maternal and cord anti-F RSV antibody levels than natural infection (5.72 vs 4.82 log 10 MFI, p < 0.0001 maternal; 5.81 vs 5.03 log 10 MFI, p < 0.0001 cord). Maternal vaccination 2-3 weeks and 3-4 weeks prior to delivery was associated with significantly lower cord:maternal transfer ratios than were observed when vaccination occurred > 5 weeks prior to delivery (p = 0.03 for 2-3 weeks, p = 0.007 for 3-4 weeks), and significantly lower transfer ratios than observed for pertussis vaccination administered prior to 30 weeks' gestation (p = 0.008 for 2-3 weeks, p = 0.03 for 3-4 weeks, similar at > 4 weeks).

Conclusions

Vaccine administration earlier in the approved 32-36 week window (at least 5 weeks prior to delivery) results in the highest transplacental transfer of maternal antibodies to the neonate. These results should inform the counseling of pregnant individuals on optimal vaccination timing.

Maternal and neonatal IgG against Klebsiella pneumoniae are associated with broad protection from neonatal sepsis: a case-control study of hospitalized neonates in Botswana

Sepsis is the leading postnatal cause of neonatal mortality worldwide. Globally Klebsiella pneumoniae is the leading cause of sepsis in hospitalized neonates. This study reports development and evaluation of ELISA for anti-Klebsiella IgG using dried blood spot samples and evaluates the association of anti-Klebsiella IgG (anti-Kleb IgG) antibodies in maternal and neonatal samples and the risk of neonatal sepsis. Neonates and their mothers were enrolled at 0-96 hours of life in the neonatal unit of a tertiary referral hospital in Gaborone, Botswana and followed until death or discharge to assess for episodes of blood culture-confirmed neonatal sepsis. Neonates with sepsis had significantly lower levels of Kleb-IgG compared to neonates who did not develop sepsis (Mann-Whitney U, p=0.012). Similarly, samples from mothers of neonates who developed sepsis tended to have less Kleb-IgG compared to mothers of controls (p=0.06). The inverse correlation between Kleb-IgG levels and all-cause bacteremia suggests that maternal Kleb-IgG is broadly protective through cross-reactivity with common bacterial epitopes. These data support the continued use of immunoglobulin assays using DBS samples to explore the role of passive immunity on neonatal sepsis risk and reaffirm the critical need for research supporting the development of maternal vaccines for neonatal sepsis.

IgG and IgM responses to the Plasmodium falciparum asexual stage antigens reflect respectively protection against malaria during pregnancy and infanthood

BACKGROUND

Plasmodium falciparum malaria is a public health issue mostly seen in tropical countries. Until now, there is no effective malaria vaccine against antigens specific to the blood-stage of P. falciparum infection. Because the pathogenesis of malarial disease results from blood-stage infection, it is essential to identify the most promising blood-stage vaccine candidate antigens under natural exposure to malaria infection.

METHODS

A cohort of 400 pregnant women and their infants was implemented in South Benin. An active and passive protocol of malaria surveillance was established during pregnancy and infancy to precisely ascertain malaria infections during the follow-up. Twenty-eight antibody (Ab) responses specific to seven malaria candidate vaccine antigens were repeatedly quantified during pregnancy (3 time points) and infancy (6 time points) in order to study the Ab kinetics and their protective role. Abs were quantified by ELISA and logistic, linear and cox-proportional hazard model were performed to analyse the associations between Ab responses and protection against malaria in mothers and infants, taking into account socio-economic factors and for infants an environmental risk of exposure.

RESULTS

The levels of IgM against MSP1, MSP2 and MSP3 showed an early protective response against the onset of symptomatic malaria infections starting from the 18th month of life, whereas no association was found for IgG responses during infancy. In women, some IgG responses tend to be associated with a protection against malaria risk along pregnancy and at delivery, among them IgG3 against GLURP-R0 and IgG2 against MSP1.

CONCLUSION

The main finding suggests that IgM should be considered in vaccine designs during infanthood. Investigation of the functional role played by IgM in malaria protection needs further attention.

Antibody kinetics between birth and three months of life in healthy infants with natural exposure to Group B streptococcus: A UK cohort study

INTRODUCTION

Capsular polysaccharide (CPS) serotype-specific Immunoglobulin G (IgG) in cord blood has been proposed as a correlate of protection against invasive Group B Streptococcus (iGBS) disease. Although protective levels are required in infants throughout the window of vulnerability up to 3 months of age, little is known regarding the kinetics of GBS-specific IgG over this period.

METHODS

We enrolled 33 healthy infants born to mothers colonized with GBS. We collected cord blood and infant blood samples either at one (21-35 days), two (49-63 days), or three months of age (77-91 days). We measured GBS serotype-specific CPS IgG concentrations and calculated the decay rate using a mixed-effects model. We further explored whether the antibody kinetics were affected by common maternal and infant factors and estimated the correlation between IgG concentration at birth and one, two, and three months of age.

RESULTS

The half-life estimate of IgG concentration for homologous and non-homologous GBS serotypes in paired samples with detectable IgG levels at both time points was 27.4 (95 % CI: 23.5-32.9) days. The decay rate did not vary by maternal age (p = 0.7), ethnicity (p = 0.1), gravida (p = 0.1), gestation (p = 0.7), and infant sex (p = 0.1). Predicted IgG titres above the assay lower limit of quantification on day 30 strongly correlated with titres at birth (Spearman correlation coefficient 0.71 [95 % CI: 0.60-0.80]).

CONCLUSION

Our results provide a basis for future investigations into the use of antibody kinetics in defining a serocorrelate of protection against late-onset iGBS disease.

Preexisting maternal immunity to AAV but not Cas9 impairs in utero gene editing in mice

In utero gene editing (IUGE) is a potential treatment for inherited diseases that cause pathology before or soon after birth. Preexisting immunity to adeno-associated virus (AAV) vectors and Cas9 endonuclease may limit postnatal gene editing. The tolerogenic fetal immune system minimizes a fetal immune barrier to IUGE. However, the ability of maternal immunity to limit fetal gene editing remains a question. We investigated whether preexisting maternal immunity to AAV or Cas9 impairs IUGE. Using a combination of fluorescent reporter mice and a murine model of a metabolic liver disease, we demonstrated that maternal anti-AAV IgG antibodies were efficiently transferred from dam to fetus and impaired IUGE in a maternal titer-dependent fashion. By contrast, maternal cellular immunity was inefficiently transferred to the fetus, and neither maternal cellular nor humoral immunity to Cas9 impaired IUGE. Using human umbilical cord and maternal blood samples collected from mid- to late-gestation pregnancies, we demonstrated that maternal-fetal transmission of anti-AAV IgG was inefficient in midgestation compared with term, suggesting that the maternal immune barrier to clinical IUGE would be less relevant at midgestation. These findings support immunologic advantages for IUGE and inform maternal preprocedural testing protocols and exclusion criteria for future clinical trials.

Placental transfer dynamics and durability of maternal COVID-19 vaccine-induced antibodies in infants

Completion of a COVID-19 vaccination series during pregnancy effectively reduces COVID-19 hospitalization among infants less than 6 months of age. The dynamics of transplacental transfer of maternal vaccine-induced antibodies, and their persistence in infants at 2, 6, 9, and 12 months, have implications for new vaccine development and optimal timing of vaccine administration in pregnancy. We evaluated anti-COVID antibody IgG subclass, Fc-receptor binding profile, and activity against wild-type Spike and RBD plus five variants of concern (VOCs) in 153 serum samples from 100 infants. Maternal IgG1 and IgG3 responses persisted in 2- and 6-month infants to a greater extent than the other IgG subclasses, with high persistence of antibodies binding placental neonatal Fc-receptor and FcγR3A. Lowest persistence was observed against the Omicron RBD-specific region. Maternal vaccine timing, placental Fc-receptor binding capabilities, antibody subclass, fetal sex, and VOC all impact the persistence of antibodies in infants through 12 months of age.

Life-threatening infections in human newborns: Reconciling age-specific vulnerability and interindividual variability

In humans, the interindividual variability of clinical outcome following exposure to a microorganism is immense, ranging from silent infection to life-threatening disease. Age-specific immune responses partially account for the high incidence of infection during the first 28 days of life and the related high mortality at population level. However, the occurrence of life-threatening disease in individual newborns remains unexplained. By contrast, inborn errors of immunity and their immune phenocopies are increasingly being discovered in children and adults with life-threatening viral, bacterial, mycobacterial and fungal infections. There is a need for convergence between the fields of neonatal immunology, with its in-depth population-wide characterization of newborn-specific immune responses, and clinical immunology, with its investigations of infections in patients at the cellular and molecular levels, to facilitate identification of the mechanisms of susceptibility to infection in individual newborns and the design of novel preventive and therapeutic strategies.

Immunogenicity at delivery after Tdap vaccination in successive pregnancies

Background

Tetanus, diphtheria, acellular pertussis (Tdap) vaccination is recommended to be administered in every pregnancy. Although the safety of this strategy has been confirmed, the immunogenicity of Tdap vaccination in two successive pregnancies has not yet been described. This study investigated Tdap-specific immunity levels and transplacental transfer in two successive pregnancies after repeated Tdap-vaccination.

Methods

Women enrolled in prior studies on Tdap vaccination during pregnancy were invited to participate in a follow-up study if they became pregnant again. Women who received a Tdap vaccine in both pregnancies were considered for this analysis. Tdap-specific total IgG and IgG subclasses were measured with a multiplex immunoassay.

Results

In total, 27 participants with a mean interval between deliveries of 2.4 years were included in the analysis. In maternal serum, Tdap-specific total IgG levels were comparable at both deliveries whereas in cord serum, all Tdap-specific total IgG antibody levels were reduced at the second compared to the first delivery. This was largely reflected in the IgG1 levels in maternal and cord serum. Transplacental transfer ratios of total IgG and IgG1 were also mostly reduced in the second compared to the first pregnancy.

Conclusion

This study reports for the first time Tdap-specific total IgG and IgG subclass levels and transfer ratios after repeated Tdap vaccination in successive pregnancies. We found reduced transfer of most Tdap-specific IgG and IgG1 antibodies in the successive pregnancy. As pertussis-specific antibodies wane quickly, Tdap vaccination in each pregnancy remains beneficial. However, more research is needed to understand the impact of closely spaced booster doses during pregnancy on early infant protection against pertussis.

Vertical Transmission of SARS-CoV-2-Specific Antibodies and Cytokine Profiles in Pregnancy

Despite intensive characterization of immune responses after COVID-19 infection and vaccination, research examining protective correlates of vertical transmission in pregnancy are limited. Herein, we profiled humoral and cellular characteristics in pregnant women infected or vaccinated at different trimesters and in their corresponding newborns. We noted a significant correlation between spike S1-specific IgG antibody and its RBD-ACE2 blocking activity (receptor-binding domain-human angiotensin-converting enzyme 2) in maternal and cord plasma (P < .001, R > 0.90). Blocking activity of spike S1-specific IgG was significantly higher in pregnant women infected during the third trimester than the first and second trimesters. Elevated levels of 28 cytokines/chemokines, mainly proinflammatory, were noted in maternal plasma with infection at delivery, while cord plasma with maternal infection 2 weeks before delivery exhibited the emergence of anti-inflammatory cytokines. Our data support vertical transmission of protective SARS-CoV-2-specific antibodies. This vertical antibody transmission and the presence of anti-inflammatory cytokines in cord blood may offset adverse outcomes of inflammation in exposed newborns.

Disturbances in the IgG Antibody Profile in HIV-Exposed Uninfected Infants Associated with Maternal Factors

Over the last 20 years, the incidence of vertical HIV transmission has decreased from 25%-42% to less than 1%. Although there are no signs of infection, the health of HIV-exposed uninfected (HEU) infants is notoriously affected during the first months of life, with opportunistic infections being the most common disease. Some studies have reported effects on the vertical transfer of antibodies, but little is known about the subclass distribution of these antibodies. We proposed to evaluate the total IgG concentration and its subclasses in HIV+ mothers and HEU pairs and to determine which maternal factors condition their levels. In this study, plasma from 69 HEU newborns, their mothers, and 71 control pairs was quantified via immunoassays for each IgG isotype. Furthermore, we followed the antibody profile of HEUs throughout the first year of life. We showed that mothers present an antibody profile characterized by high concentrations of IgG1 and IgG3 but reduced IgG2, and HEU infants are born with an IgG subclass profile similar to that of their maternal pair. Interestingly, this passively transferred profile could remain influenced even during their own antibody production in HEU infants, depending on maternal conditions such as CD4+ T-cell counts and maternal antiretroviral treatment. Our findings indicate that HEU infants exhibit an altered IgG subclass profile influenced by maternal factors, potentially contributing to their increased susceptibility to infections.

Current Insights Into K-associated Fetal Anemia and Potential Treatment Strategies for Sensitized Pregnancies

K-associated anemic disease of the fetus and newborn (K-ADFN) is a rare but life-threatening disease in which maternal alloantibodies cross the placenta and can mediate an immune attack on fetal red blood cells expressing the K antigen. A considerably more common disease, D-associated hemolytic disease of the fetus and newborn (D-HDFN), can be prophylactically treated using polyclonal α-D antibody preparations. Currently, no such prophylactic treatment exists for K-associated fetal anemia, and disease is usually treated with intrauterine blood transfusions. Here we review current understanding of the biology of K-associated fetal anemia, how the maternal immune system is sensitized to fetal red blood cells, and what is understood about potential mechanisms of prophylactic HDFN interventions. Given the apparent challenges associated with preventing alloimmunization, we highlight novel strategies for treating sensitized mothers to prevent fetal anemia that may hold promise not only for K-mediated disease, but also for other pathogenic alloantibody responses.

PCSK9 inhibitor use during pregnancy in a case of familial hypercholesterolemia complicated with coronary artery disease

Limited data have been reported on the use of proprotein convertase subtilisin/kexin type 9 (PCSK 9) inhibitors during pregnancy in women with familial hypercholesterolemia (FH). Here, we present the first case of initiating evolocumab (PCSK9 inhibitor) in a compound heterozygous FH mother. The patient was a 34-year-old primipara with severe dyslipidemia and a history of coronary artery bypass surgery. An elevated low-density lipoprotein cholesterol (LDL-C) level of 420 mg/dL was detected in the first trimester and persistently increased throughout pregnancy. Evolocumab was administered at 31 and 35 weeks of gestation, showing a positive effect on stabilizing LDL-C levels. Planned delivery with labor analgesia was performed at 38 + 4 weeks. Both the mother and infant were discharged without any notable complications. Hence, evolocumab, an IgG2 monochromatic antibody with little placental permeability, may be an alternative medication with limited influence on infants. Further studies are needed to assess the safety of evolocumab administration during pregnancy.

FcRn-enhancing mutations lead to increased and prolonged levels of the HIV CCR5-blocking monoclonal antibody leronlimab in the fetuses and newborns of pregnant rhesus macaques

Prenatal administration of monoclonal antibodies (mAbs) is a strategy that could be exploited to prevent viral infections during pregnancy and early life. To reach protective levels in fetuses, mAbs must be transported across the placenta, a selective barrier that actively and specifically promotes the transfer of antibodies (Abs) into the fetus through the neonatal Fc receptor (FcRn). Because FcRn also regulates Ab half-life, Fc mutations like the M428L/N434S, commonly known as LS mutations, and others have been developed to enhance binding affinity to FcRn and improve drug pharmacokinetics. We hypothesized that these FcRn-enhancing mutations could similarly affect the delivery of therapeutic Abs to the fetus. To test this hypothesis, we measured the transplacental transfer of leronlimab, an anti-CCR5 mAb, in clinical development for preventing HIV infections, using pregnant rhesus macaques to model in utero mAb transfer. We also generated a stabilized and FcRn-enhanced form of leronlimab, termed leronlimab-PLS. Leronlimab-PLS maintained higher levels within the maternal compartment while also reaching higher mAb levels in the fetus and newborn circulation. Further, a single dose of leronlimab-PLS led to complete CCR5 receptor occupancy in mothers and newborns for almost a month after birth. These findings support the optimization of FcRn interactions in mAb therapies designed for administration during pregnancy.

Antibody and B-cell Immune Responses Against Bordetella Pertussis Following Infection and Immunization

Neither immunization nor recovery from natural infection provides life-long protection against Bordetella pertussis. Replacement of a whole-cell pertussis (wP) vaccine with an acellular pertussis (aP) vaccine, mutations in B. pertussis strains, and better diagnostic techniques, contribute to resurgence of number of cases especially in young infants. Development of new immunization strategies relies on a comprehensive understanding of immune system responses to infection and immunization and how triggering these immune components would ensure protective immunity. In this review, we assess how B cells, and their secretory products, antibodies, respond to B. pertussis infection, current and novel vaccines and highlight similarities and differences in these responses. We first focus on antibody-mediated immunity. We discuss antibody (sub)classes, elaborate on antibody avidity, ability to neutralize pertussis toxin, and summarize different effector functions, i.e. ability to activate complement, promote phagocytosis and activate NK cells. We then discuss challenges and opportunities in studying B-cell immunity. We highlight shared and unique aspects of B-cell and plasma cell responses to infection and immunization, and discuss how responses to novel immunization strategies better resemble those triggered by a natural infection (i.e., by triggering responses in mucosa and production of IgA). With this comprehensive review, we aim to shed some new light on the role of B cells and antibodies in the pertussis immunity to guide new vaccine development.

Maternal vaccination against RSV can substantially reduce childhood mortality in low-income and middle-income countries: A mathematical modeling study

Background

Respiratory syncytial virus (RSV) is a leading cause of childhood mortality in infants below 6 months of age. In low-income and middle-income countries (LMICs), the public health burden is substantial and resources are limited. It is critical to inform decision makers about effectiveness of new interventions.

Methods

We developed a mathematical model where individual RSV subtype A (RSV-A) and B (RSV-B) maternally derived neutralizing titers were predicted at time of birth after maternal vaccination with the RSV prefusion F protein-based vaccine. We estimated the subsequent duration of vaccine-induced immunity and compared this to the age at time of death distribution in the RSV GOLD Mortality Database to predict the potential impact of maternal vaccination on RSV-related childhood mortality. We used country-specific timing of antenatal care visits distributions and mortality estimates to make country-specific predictions for number of cases averted.

Findings

The model predicts that on average a neonate born at 40 weeks gestational age will be protected between 6 and 7 months from RSV-A and approximately 5 months from RSV-B related mortality. We estimated the potential impact of RSV-related mortality for in-hospital and out-of-hospital cases in LMICs and predicted that in 51 GAVI-eligible countries maternal vaccination could avert between 55% and 63% of the RSV-related in-hospital mortality cases below 6 months of age.

Interpretation

We show that maternal vaccination could substantially decrease RSV-A and RSV-B related in-hospital and out-of-hospital mortality in LMICs in the first 6 months of life.

Acquisition of complement fixing antibodies targeting Plasmodium falciparum merozoites in infants and their mothers in Uganda

Background

Antibody-mediated complement fixation has previously been associated with protection against malaria in naturally acquired immunity. However, the process of early-life development of complement-fixing antibodies in infants, both in comparison to their respective mothers and to other immune parameters, remains less clear.

Results

We measured complement-fixing antibodies in newborns and their mothers in a malaria endemic area over 5 years follow-up and found that infants' complement-fixing antibody levels were highest at birth, decreased until six months, then increased progressively until they were similar to birth at five years. Infants with high levels at birth experienced a faster decay of complement-fixing antibodies but showed similar levels to the low response group of newborns thereafter. No difference was observed in antibody levels between infant cord blood and mothers at delivery. The same result was found when categorized into high and low response groups, indicating placental transfer of antibodies. Complement-fixing antibodies were positively correlated with total schizont-specific IgG and IgM levels in mothers and infants at several time points. At nine months, complement-fixing antibodies were negatively correlated with total B cell frequency and osteopontin concentrations in the infants, while positively correlated with atypical memory B cells and P. falciparum-positive atypical memory B cells.

Conclusion

This study indicates that complement-fixing antibodies against P. falciparum merozoites are produced in the mothers and placentally-transferred, and they are acquired in infants over time during the first years of life. Understanding early life immune responses is crucial for developing a functional, long lasting malaria vaccine.

Quantitative mechanistic model reveals key determinants of placental IgG transfer and informs prenatal immunization strategies

Transplacental antibody transfer is crucially important in shaping neonatal immunity. Recently, prenatal maternal immunization has been employed to boost pathogen-specific immunoglobulin G (IgG) transfer to the fetus. Multiple factors have been implicated in antibody transfer, but how these key regulators work together to elicit selective transfer is pertinent to engineering vaccines for mothers to optimally immunize their newborns. Here, we present the first quantitative mechanistic model to uncover the determinants of placental antibody transfer and inform personalized immunization approaches. We identified placental FcγRIIb expressed by endothelial cells as a limiting factor in receptor-mediated transfer, which plays a key role in promoting preferential transport of subclasses IgG1, IgG3, and IgG4, but not IgG2. Integrated computational modeling and in vitro experiments reveal that IgG subclass abundance, Fc receptor (FcR) binding affinity, and FcR abundance in syncytiotrophoblasts and endothelial cells contribute to inter-subclass competition and potentially inter- and intra-patient antibody transfer heterogeneity. We developed an in silico prenatal vaccine testbed by combining a computational model of maternal vaccination with this placental transfer model using the tetanus, diphtheria, and acellular pertussis (Tdap) vaccine as a case study. Model simulations unveiled precision prenatal immunization opportunities that account for a patient's anticipated gestational length, placental size, and FcR expression by modulating vaccine timing, dosage, and adjuvant. This computational approach provides new perspectives on the dynamics of maternal-fetal antibody transfer in humans and potential avenues to optimize prenatal vaccinations that promote neonatal immunity.

Advances in proteomics: characterization of the innate immune system after birth and during inflammation

Proteomics is the characterization of the protein composition, the proteome, of a biological sample. It involves the large-scale identification and quantification of proteins, peptides, and post-translational modifications. This review focuses on recent developments in mass spectrometry-based proteomics and provides an overview of available methods for sample preparation to study the innate immune system. Recent advancements in the proteomics workflows, including sample preparation, have significantly improved the sensitivity and proteome coverage of biological samples including the technically difficult blood plasma. Proteomics is often applied in immunology and has been used to characterize the levels of innate immune system components after perturbations such as birth or during chronic inflammatory diseases like rheumatoid arthritis (RA) and inflammatory bowel disease (IBD). In cancers, the tumor microenvironment may generate chronic inflammation and release cytokines to the circulation. In these situations, the innate immune system undergoes profound and long-lasting changes, the large-scale characterization of which may increase our biological understanding and help identify components with translational potential for guiding diagnosis and treatment decisions. With the ongoing technical development, proteomics will likely continue to provide increasing insights into complex biological processes and their implications for health and disease. Integrating proteomics with other omics data and utilizing multi-omics approaches have been demonstrated to give additional valuable insights into biological systems.

Reduced maternal immunity and vertical transfer of immunity against SARS-CoV-2 variants of concern with COVID-19 exposure or initial vaccination in pregnancy

Introduction

As the SARS-CoV-2 pandemic continues to evolve, we face new variants of concern with a concurrent decline in vaccine booster uptake. We aimed to evaluate the difference in immunity gained from the original SARS-CoV-2 mRNA vaccine series in pregnancy versus SARS-CoV-2 exposure during pregnancy against recent variants of concern.

Study Design

This is a retrospective analysis of previously collected samples from 192 patients who delivered between February 2021 and August 2021. Participants were categorized as 1) COVID vaccine: mRNA vaccine in pregnancy, 2) COVID-exposed, and 3) controls. The primary outcome was neutralizing capacity against wild-type, Delta, and Omicron-B1 between cohorts. Secondary outcomes include a comparison of cord-blood ID50 as well as the efficiency of vertical transfer, measured by cord-blood:maternal blood ID50 for each variant.

Results

Pregnant women with COVID-19 vaccination had a greater spike in IgG titers compared to both those with COVID-19 disease exposure and controls. Both COVID exposure and vaccination resulted in immunity against Delta, but only COVID vaccination resulted in significantly greater Omicron ID-50 versus controls. The neutralizing capacity of serum from newborns was lower than that of their mothers, with COVID-vaccination demonstrating higher cord-blood ID50 vs wildtype and Delta variants compared to control or COVID-exposed, but neither COVID-exposure nor vaccination demonstrated significantly higher Omicron ID50 in cord-blood compared to controls. There was a 0.20 (0.07-0.33, p=0.004) and 0.12 (0.0-0.24, p=0.05) increase in cord-blood:maternal blood ID50 with COVID vaccination compared to COVID-19 exposure for wild-type and Delta respectively. In pair-wise comparison, vertical transfer of neutralization capacity (cord-blood:maternal blood ID50) was greatest for wild-type and progressively reduced for Delta and Omicron ID50.

Conclusion

Pregnant patients with either an initial mRNA vaccination series or COVID-exposure demonstrated reduced immunity against newer variants compared to wild-type as has been reported for non-pregnant individuals; however, the COVID-vaccination series afforded greater cross-variant immunity to pregnant women, specifically against Omicron, than COVID-disease. Vertical transfer of immunity is greater in those with COVID vaccination vs COVID disease exposure but is reduced with progressive variants. Our results reinforce the importance of bivalent booster vaccination in pregnancy for both maternal and infant protection and also provide a rationale for receiving updated vaccines as they become available.

Are high avidity antibodies to Plasmodium falciparum antigens preferentially transferred across the placenta of premature and term babies?

INTRODUCTION

Transplacental transport of maternal IgG via the neonatal Fc receptor (FcRn) provides babies with passive immunity. Several factors are reported to influence transport, including the avidity of antibodies (Abs) for their cognate antigens. Unfortunately, information on the role of antibody (Ab) avidity is limited. This study investigated if i) antibodies (Abs) with high avidity for 6 Plasmodium falciparum antigens and tetanus toxoid (TTx) were preferentially transferred to premature and term Cameroonian babies and ii) if Ab avidity was increased in babies whose mothers had placental malaria (PM), implicating the involvement of immune complexes.

METHODS

Total IgG (mg/ml) and Abs to malarial antigens (AMA1, EBA-175, MSP1-42, MSP2, MSP3, DBL5 of VAR2CSA) and TTx were measured in paired mother-cord samples obtained from premature and term deliveries in Cameroon. Half the women had PM at delivery. Avidity Indices (AIs) were determined by treating antigen-bound-Abs with different molar concentrations of NH4SCN and calculating 50% endpoints.

RESULTS

Total IgG and antigen-specific Abs increased in cord blood with gestational age; however, AIs did not. AIs in paired maternal-cord blood samples were strongly associated for all antigens (r = 0.77-0.96). However, no significant different in AIs was found between paired mother-cord blood samples for any of the antigens (p values > 0.05). Similarly, Ab avidity was not increased in cord blood of babies whose mothers had PM or hypergammaglobulinemia.

DISCUSSION

Overall, there was no evidence that higher avidity Abs to any of the malarial antigens or TTx were preferentially transferred to Cameroonian babies.

Transplacental transfer of anti-SARS-CoV-2 neutralizing antibodies in comparison to other pathogens total antibodies

BACKGROUNDS

Due to immaturity of their immune system, passive maternal immunization is essential for newborns during their first months of life. Therefore, in the current context of intense circulation of SARS-CoV-2, identifying factors influencing the transfer ratio (TR) of neutralizing antibodies against SARS-CoV-2 (NAb) appears important.

METHODS

Our study nested in the COVIPREG cohort (NCT04355234), included mothers who had a SARS-CoV-2 PCR positive during their pregnancy and their newborns. Maternal and neonatal NAb levels were measured with the automated iFlash system.

RESULTS

For the 173 mother-infant pairs included in our study, the median gestational age (GA) at delivery was 39.4 weeks of gestation (WG), and 29.7 WG at maternal SARS-CoV-2 infection. Using a multivariate logistic model, having a NAb TR above 1 was positively associated with a longer delay from maternal positive SARS-CoV-2 PCR to delivery (aOR 1.09, 95% CI: 1.03 - 1.17) and with a later GA at delivery (aOR = 1.58, 95% CI: 1.09 - 2.52). It was negatively associated with being a male newborn (aOR 0.21, 95% CI: 0.07 - 0.59). In 3rd trimester SARS-CoV-2 infected mothers, NAb TR was inferior to VZV, toxoplasmosis, CMV, measle and rubella's TR. However, in 1st or 2nd trimester infected mothers, only measle TR was different from NAb TR.

CONCLUSION

Male newborn of mothers infected by SARS-CoV-2 during their pregnancy appear to have less protection against SARS-CoV-2 in their first months of life than female newborns. Measle TR was superior to NAb TR even in case of 1st or 2nd trimester maternal SARS-CoV-2 infection. Future studies are needed to investigate possible differences in transmission of NAb following infection vs vaccination and its impact on TR.

Modulation of engineered nanomaterial interactions with organ barriers for enhanced drug transport

The biomedical use of nanoparticles (NPs) has been the focus of intense research for over a decade. As most NPs are explored as carriers to alter the biodistribution, pharmacokinetics and bioavailability of associated drugs, the delivery of these NPs to the tissues of interest remains an important topic. To date, the majority of NP delivery studies have used tumor models as their tool of interest, and the limitations concerning tumor targeting of systemically administered NPs have been well studied. In recent years, the focus has also shifted to other organs, each presenting their own unique delivery challenges to overcome. In this review, we discuss the recent advances in leveraging NPs to overcome four major biological barriers including the lung mucus, the gastrointestinal mucus, the placental barrier, and the blood-brain barrier. We define the specific properties of these biological barriers, discuss the challenges related to NP transport across them, and provide an overview of recent advances in the field. We discuss the strengths and shortcomings of different strategies to facilitate NP transport across the barriers and highlight some key findings that can stimulate further advances in this field.

Maternal vaccination: shaping the neonatal response to pertussis

Antepartum maternal vaccination can protect highly sensitive newborns before they are old enough to receive their own vaccines. Two vaccines are currently recommended during pregnancy: the flu vaccine and the Tdap vaccine against tetanus, diphtheria, and pertussis. Although there is strong evidence that maternal vaccination works to protect the offspring, limitations in the understanding of vaccines and of maternal transfer of immunity compound to obscure our understanding of how they work. Here we focus on the example of pertussis to explore the possible mechanisms involved in the transfer of protection to offspring and how these may impact the newborn's response to future exposure to pertussis. For example, Tdap vaccines induce pathogen specific antibodies, and those antibodies are known to be transferred from mother to the fetus in utero and to the newborn via milk. But antibodies alone have modest impact on pertussis disease, and even less effect on colonization/transmission. Maternal immune cells can also be transferred to offspring and may play a direct role in protection from disease and/or influence the developing neonatal immune system. However, some of the transferred immunity may also blunt the offspring's response to subsequent vaccination. In this review we will summarize the protection conferred to offspring by maternal vaccination against pertussis and the likely mechanisms by which protection is transferred, identifying the many knowledge gaps that limit our most effective application of this approach.

The therapeutic age of the neonatal Fc receptor

IgGs are essential soluble components of the adaptive immune response that evolved to protect the body from infection. Compared with other immunoglobulins, the role of IgGs is distinguished and enhanced by their high circulating levels, long half-life and ability to transfer from mother to offspring, properties that are conferred by interactions with neonatal Fc receptor (FcRn). FcRn binds to the Fc portion of IgGs in a pH-dependent manner and protects them from intracellular degradation. It also allows their transport across polarized cells that separate tissue compartments, such as the endothelium and epithelium. Further, it is becoming apparent that FcRn functions to potentiate cellular immune responses when IgGs, bound to their antigens, form IgG immune complexes. Besides the protective role of IgG, IgG autoantibodies are associated with numerous pathological conditions. As such, FcRn blockade is a novel and effective strategy to reduce circulating levels of pathogenic IgG autoantibodies and curtail IgG-mediated diseases, with several FcRn-blocking strategies on the path to therapeutic use. Here, we describe the current state of knowledge of FcRn-IgG immunobiology, with an emphasis on the functional and pathological aspects, and an overview of FcRn-targeted therapy development.

Impact of pregnancy on polyfunctional IgG and memory B cell responses to Tdap immunization

BACKGROUND

Maternal pertussis immunization using Tdap vaccine is recommended in many countries to protect newborns from severe post-natal infection. Immunological changes during pregnancy may influence the response to vaccines. The quality of IgG and memory B cell responses to Tdap immunization in pregnant women has not yet been described.

METHODS

The impact of pregnancy on the response to Tdap vaccination was assessed by comparing humoral immune responses in 42 pregnant and 39 non-pregnant women. The levels of serum pertussis antigens and tetanus toxoid-specific IgG, IgG subclasses, IgG Fc-mediated effector functions, as well as memory B cell frequencies were assessed before and at several time points after vaccination.

RESULTS

Tdap immunization induced similar levels of pertussis and tetanus-specific IgG and IgG subclasses in pregnant and non-pregnant women. Pregnant women produced IgG promoting complement deposition, and neutrophils and macrophages phagocytosis at levels comparable to non-pregnant women. They were also able to expand pertussis and tetanus-specific memory B cells at similar frequencies as non-pregnant women, suggesting equivalent "boostability". Higher levels of vaccine-specific IgG, IgG subclasses, and IgG Fc-mediated effector functions were detected in cord blood as compared to maternal blood, indicating efficient transport across the placenta.

CONCLUSIONS

This study demonstrates that pregnancy does not affect the quality of effector IgG and memory B cell responses to Tdap immunization and that polyfunctional IgG are efficiently transferred across the placenta.

REGISTRY'S URL AND THE TRIAL'S REGISTRATION NUMBER

ClinicalTrials.Gov (NCT03519373).

Maternal HIV infection drives altered placental Mtb-specific antibody transfer

Introduction

Placental transfer of maternal antibodies is essential for neonatal immunity over the first months of life. In the setting of maternal HIV infection, HIV-exposed uninfected (HEU) infants are at higher risk of developing severe infections, including active tuberculosis (TB). Given our emerging appreciation for the potential role of antibodies in the control of Mycobacterium tuberculosis (Mtb), the bacteria that causes TB, here we aimed to determine whether maternal HIV status altered the quality of Mtb-specific placental antibody transfer.

Methods

Antigen-specific antibody systems serology was performed to comprehensively characterize the Mtb-specific humoral immune response in maternal and umbilical cord blood from HIV infected and uninfected pregnant people in Uganda.

Results

Significant differences were noted in overall antibody profiles in HIV positive and negative maternal plasma, resulting in heterogeneous transfer of Mtb-specific antibodies. Altered antibody transfer in HIV infected dyads was associated with impaired binding to IgG Fc-receptors, which was directly linked to HIV viral loads and CD4 counts.

Conclusions

These results highlight the importance of maternal HIV status on antibody transfer, providing clues related to alterations in transferred maternal immunity that may render HEU infants more vulnerable to TB than their HIV-unexposed peers.

Evidence for the Role of a Second Fc-Binding Receptor in Placental IgG Transfer in Nonhuman Primates

Transplacental transfer of maternal antibodies provides the fetus and newborn with passive protection against infectious diseases. While the role of the highly conserved neonatal Fc receptor (FcRn) in transfer of IgG in mammals is undisputed, recent reports have suggested that a second receptor may contribute to transport in humans. We report poor transfer efficiency of plant-expressed recombinant HIV-specific antibodies, including engineered variants with high FcRn affinity, following subcutaneous infusion into rhesus macaques close to parturition. Unexpectedly, unlike those derived from mammalian tissue culture, plant-derived antibodies were essentially unable to cross macaque placentas. This defect was associated with poor Fcγ receptor binding and altered Fc glycans and was not recapitulated in mice. These results suggest that maternal-fetal transfer of IgG across the three-layer primate placenta may require a second receptor and suggest a means of providing maternal antibody treatments during pregnancy while avoiding fetal harm. IMPORTANCE This study compared the ability of several human HIV envelope-directed monoclonal antibodies produced in plants with the same antibodies produced in mammalian cells for their ability to cross monkey and mouse placentas. We found that the two types of antibodies have comparable transfer efficiencies in mice, but they are differentially transferred across macaque placentas, consistent with a two-receptor IgG transport model in primates. Importantly, plant-produced monoclonal antibodies have excellent binding characteristics for human FcRn receptors, permitting desirable pharmacokinetics in humans. The lack of efficient transfer across the primate placenta suggests that therapeutic plant-based antibody treatments against autoimmune diseases and cancer could be provided to the mother while avoiding transfer and preventing harm to the fetus.

Microbial transmission, colonisation and succession: from pregnancy to infancy

The microbiome has been proven to be associated with many diseases and has been used as a biomarker and target in disease prevention and intervention. Currently, the vital role of the microbiome in pregnant women and newborns is increasingly emphasised. In this review, we discuss the interplay of the microbiome and the corresponding immune mechanism between mothers and their offspring during the perinatal period. We aim to present a comprehensive picture of microbial transmission and potential immune imprinting before and after delivery. In addition, we discuss the possibility of in utero microbial colonisation during pregnancy, which has been highly debated in recent studies, and highlight the importance of the microbiome in infant development during the first 3 years of life. This holistic view of the role of the microbial interplay between mothers and infants will refine our current understanding of pregnancy complications as well as diseases in early life and will greatly facilitate the microbiome-based prenatal diagnosis and treatment of mother-infant-related diseases.

Homo medicus: The transition to meat eating increased pathogen pressure and the use of pharmacological plants in Homo

The human lineage transitioned to a more carnivorous niche 2.6 mya and evolved a large body size and slower life history, which likely increased zoonotic pathogen pressure. Evidence for this increase includes increased zoonotic infections in modern hunter-gatherers and bushmeat hunters, exceptionally low stomach pH compared to other primates, and divergence in immune-related genes. These all point to change, and probably intensification, in the infectious disease environment of Homo compared to earlier hominins and other apes. At the same time, the brain, an organ in which immune responses are constrained, began to triple in size. We propose that the combination of increased zoonotic pathogen pressure and the challenges of defending a large brain and body from pathogens in a long-lived mammal, selected for intensification of the plant-based self-medication strategies already in place in apes and other primates. In support, there is evidence of medicinal plant use by hominins in the middle Paleolithic, and all cultures today have sophisticated, plant-based medical systems, add spices to food, and regularly consume psychoactive plant substances that are harmful to helminths and other pathogens. We propose that the computational challenges of discovering effective plant-based treatments, the consequent ability to consume more energy-rich animal foods, and the reduced reliance on energetically-costly immune responses helped select for increased cognitive abilities and unique exchange relationships in Homo. In the story of human evolution, which has long emphasized hunting skills, medical skills had an equal role to play.

Development of Porcine Monoclonal Antibodies with In Vitro Neutralizing Activity against Classical Swine Fever Virus from C-Strain E2-Specific Single B Cells

Neutralizing antibodies (nAbs) can be used before or after infection to prevent or treat viral diseases. However, there are few efficacious nAbs against classical swine fever virus (CSFV) that have been produced, especially the porcine-originated nAbs. In this study, we generated three porcine monoclonal antibodies (mAbs) with in vitro neutralizing activity against CSFV, aiming to facilitate the development of passive antibody vaccines or antiviral drugs against CSFV that offer the advantages of stability and low immunogenicity. Pigs were immunized with the C-strain E2 (CE2) subunit vaccine, KNB-E2. At 42 days post vaccination (DPV), CE2-specific single B cells were isolated via fluorescent-activated cell sorting (FACS) baited by Alexa Fluor™ 647-labeled CE2 (positive), goat anti-porcine IgG (H + L)-FITC antibody (positive), PE mouse anti-pig CD3ε (negative) and PE mouse anti-pig CD8a (negative). The full coding region of IgG heavy (H) chains and light (L) chains was amplified by reverse transcription-polymerase chain reaction (RT-PCR). Overall, we obtained 3 IgG H chains, 9 kappa L chains and 36 lambda L chains, which include three paired chains (two H + κ and one H + λ). CE2-specific mAbs were successfully expressed in 293T cells with the three paired chains. The mAbs exhibit potent neutralizing activity against CSFVs. They can protect ST cells from infections in vitro with potent IC50 values from 14.43 µg/mL to 25.98 µg/mL for the CSFV C-strain, and 27.66 µg/mL to 42.61 µg/mL for the CSFV Alfort strain. This study is the first report to describe the amplification of whole-porcine IgG genes from single B cells of KNB-E2-vaccinated pig. The method is versatile, sensitive, and reliable. The generated natural porcine nAbs can be used to develop long-acting and low-immunogenicity passive antibody vaccine or anti-CSFV agents for CSF control and prevention.

Single-center serological surveillance of SARS-CoV-2 in pregnant patients presenting to labor and delivery

OBJECTIVE

To measure maternal/fetal SARS-CoV-2 antibody levels.

METHODS

A prospective observational study of eligible parturients admitted to the hospital for infant delivery was conducted between April and September 2020. SARS-CoV-2 antibody levels were measured in maternal and umbilical cord specimens using an in-house ELISA based on the receptor-binding domain (RBD) of the spike protein. Among SARS-CoV-2 seropositive patients, spike RBD antibody isotypes (IgG, IgM, and IgA) and ACE2 inhibiting antibodies were measured.

RESULTS

In total, 402 mothers were enrolled and spike RBD antibodies in 388 pregnancies were measured (336 maternal and 52 cord specimens). Of them, 19 were positive (15 maternal, 4 cord) resulting in a seroprevalence estimate of 4.8% (95% confidence interval 2.9-7.4). Of the 15 positive maternal specimens, all had cord blood tested. Of the 15 paired specimens, 14 (93.3%) were concordant. Four of the 15 pairs were from symptomatic mothers, and all four showed high spike-ACE2 blocking antibody levels, compared to only 3 of 11 (27.3%) from asymptomatic mothers.

CONCLUSION

A variable antibody response to SARS-CoV-2 in pregnancy among asymptomatic infections compared to symptomatic infections was found, the significance of which is unknown. Although transfer of transplacental neutralizing antibodies occurred, additional research is needed to determine how long maternal antibodies can protect the infant against SARS-CoV-2 infection.

Maternal brain reactive antibodies profile in autism spectrum disorder: an update

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder with multifactorial etiologies involving both genetic and environmental factors. In the past two decades it has become clear that in utero exposure to toxins, inflammation, microbiome, and antibodies (Abs), may play a role in the etiology of ASD. Maternal brain-reactive Abs, present in 10-20% of mothers of a child with ASD, pose a potential risk to the developing brain because they can gain access to the brain during gestation, altering brain development during a critical period. Different maternal anti-brain Abs have been associated with ASD and have been suggested to bind extracellular or intracellular neuronal antigens. Clinical data from various cohorts support the increase in prevalence of such maternal brain-reactive Abs in mothers of a child with ASD compared to mothers of a typically developing child. Animal models of both non-human primates and rodents have provided compelling evidence supporting a pathogenic role of these Abs. In this review we summarize the data from clinical and animal models addressing the role of pathogenic maternal Abs in ASD. We propose that maternal brain-reactive Abs are an overlooked and promising field of research, representing a modifiable risk factor that may account for up to 20% of cases of ASD. More studies are needed to better characterize the Abs that contribute to the risk of having a child with ASD, to understand whether we can we predict such cases of ASD, and to better pinpoint the antigenic specificity of these Abs and their mechanisms of pathogenicity.

Expected impact of immunomodulatory agents during pregnancy: A newborn's perspective

The neonatal immune ontogeny begins during pregnancy to ensure that the neonate is well-suited for perinatal life. It prioritizes Th2/M2 and regulatory responses over Th/M1 activity to avoid excessive inflammatory responses and to ensure immune tolerance and homeostasis. Newborns also present increased Th17/Th22 responses providing effective anti-fungal immunity and mucosal protection. Intrauterine exposure to immune modulatory drugs with the placental transfer may influence the natural course of the fetal immune development. The vertical transfer of both biological therapy and small molecules begins during the first trimester through neonatal Fc receptor or placental diffusion, respectively, reaching its maximum transfer potential during the third trimester of pregnancy. Most of the biological therapy have a prolonged half-life in newborn's blood, being detectable in infants up to 12 months after birth (usually 6-9 months). The use of immunomodulators during pregnancy is gaining global interest. Current evidence mainly reports birth-related outcomes without exhaustive analysis of the on-target side effect on the perinatal immune system ontogeny, the infection risk, or the immune dysregulation. The present review will focus on: (1) the main characteristics of the perinatal immune system to understand its specific features and vulnerabilities to immune modulation; (2) the mechanisms of placental transfer of immunomodulators; and (3) the immune changes reported to date in newborns exposed to immunomodulators with emphasis on the current concerns and gaps in knowledge.