B lymphocyte subsets and their functional activity in the early months of life

Transcriptome analysis of immune genes in peripheral blood mononuclear cells of young foals and adult horses

During the neonatal period, the ability to generate immune effector and memory responses to vaccines or pathogens is often questioned. This study was undertaken to obtain a global view of the natural differences in the expression of immune genes early in life. Our hypothesis was that transcriptome analyses of peripheral blood mononuclear cells (PBMCs) of foals (on day 1 and day 42 after birth) and adult horses would show differential gene expression profiles that characterize natural immune processes. Gene ontology enrichment analysis provided assessment of biological processes affected by age, and a list of 897 genes with ≥2 fold higher (p<0.01) expression in day 42 when compared to day 1 foal samples. Up-regulated genes included B cell and T cell receptor diversity genes; DNA replication enzymes; natural killer cell receptors; granzyme B and perforin; complement receptors; immunomodulatory receptors; cell adhesion molecules; and cytokines/chemokines and their receptors. The list of 1,383 genes that had higher (p<0.01) expression on day 1 when compared to day 42 foal samples was populated by genes with roles in innate immunity such as antimicrobial proteins; pathogen recognition receptors; cytokines/chemokines and their receptors; cell adhesion molecules; co-stimulatory molecules; and T cell receptor delta chain. Within the 742 genes with increased expression between day 42 foal and adult samples, B cell immunity was the main biological process (p = 2.4E-04). Novel data on markedly low (p<0.0001) TLR3 gene expression, and high (p≤0.01) expression of IL27, IL13RA1, IREM-1, SIRL-1, and SIRPα on day 1 compared to day 42 foal samples point out potential mechanisms of increased susceptibility to pathogens in early life. The results portray a progression from innate immune gene expression predominance early in life to adaptive immune gene expression increasing with age with a putative overlay of immune suppressing genes in the neonatal phase. These results provide insight to the unique attributes of the equine neonatal and young immune system, and offer many avenues of future investigation.

Decreased production of class-switched antibodies in neonatal B cells is associated with increased expression of miR-181b

The increased susceptibility to infections of neonates is caused by an immaturity of the immune system as a result of both qualitative and quantitative differences between neonatal and adult immune cells. With respect to B cells, neonatal antibody responses are known to be decreased. Accountable for this is an altered composition of the neonatal B cell compartment towards more immature B cells. However, it remains unclear whether the functionality of individual neonatal B cell subsets is altered as well. In the current study we therefore compared phenotypical and functional characteristics of corresponding neonatal and adult B cell subpopulations. No phenotypic differences could be identified with the exception of higher IgM expression in neonatal B cells. Functional analysis revealed differences in proliferation, survival, and B cell receptor signaling. Most importantly, neonatal B cells showed severely impaired class-switch recombination (CSR) to IgG and IgA. This was associated with increased expression of miR-181b in neonatal B cells. Deficiency of miR-181b resulted in increased CSR. With this, our results highlight intrinsic differences that contribute to weaker B cell antibody responses in newborns.

Immune responses to congenital cytomegalovirus infection

Human cytomegalovirus (HCMV) is the most common cause of viral infection acquired in utero. Even though the infection has been studied for several decades, immune determinants important for virus control and mechanisms of long-term sequelae caused by infection are still insufficiently characterized. Animal models of congenital HCMV infection provide unique opportunity to study various aspects of human disease. In this review, we summarize current knowledge on the role of immune system in congenital CMV infection, with emphasis on lessons learned from mouse model of congenital CMV infection.

Antigen-specific immunoglobulin variable region sequencing measures humoral immune response to vaccination in the equine neonate

The value of prophylactic neonatal vaccination is challenged by the interference of passively transferred maternal antibodies and immune competence at birth. Taken our previous studies on equine B cell ontogeny, we hypothesized that the equine neonate generates a diverse immunoglobulin repertoire in response to vaccination, independently of circulating maternal antibodies. In this study, equine neonates were vaccinated with 3 doses of keyhole limpet hemocyanin (KLH) or equine influenza vaccine, and humoral immune responses were assessed using antigen-specific serum antibodies and B cell Ig variable region sequencing. An increase (p<0.0001) in serum KLH-specific IgG level was measured between days 21 and days 28, 35 and 42 in vaccinated foals from non-vaccinated mares. In vaccinated foals from vaccinated mares, serum KLH-specific IgG levels tended to increase at day 42 (p = 0.07). In contrast, serum influenza-specific IgG levels rapidly decreased (p≤0.05) in vaccinated foals from vaccinated mares within the study period. Nevertheless, IGHM and IGHG sequences were detected in KLH- and influenza- sorted B cells of vaccinated foals, independently of maternal vaccination status. Immunoglobulin nucleotide germline identity, IGHV gene usage and CDR length of antigen-specific IGHG sequences in B cells of vaccinated foals revealed a diverse immunoglobulin repertoire with isotype switching that was comparable between groups and to vaccinated mares. The low expression of CD27 memory marker in antigen-specific B cells, and of cytokines in peripheral blood mononuclear cells upon in vitro immunogen stimulation indicated limited lymphocyte population expansion in response to vaccine during the study period.

High-content cytometry and transcriptomic biomarker profiling of human B-cell activation

BACKGROUND

Primary antibody deficiencies represent the most prevalent, although very heterogeneous, group of inborn immunodeficiencies, with a puzzling complexity of cellular and molecular processes involved in disease pathogenesis.

OBJECTIVE

We aimed to study in detail the kinetics of CD40 ligand/IL-21-induced B-cell differentiation to define new biomarker sets for further research into primary antibody deficiencies.

METHODS

We applied high-content screening methods to monitor B-cell activation on the cellular (chip cytometry) and transcriptomic (RNA microarray) levels.

RESULTS

The complete activation process, including stepwise changes in protein and RNA expression patterns, entry into the cell cycle, proliferation and expression of activation-induced cytidine deaminase (AID), DNA repair enzymes, and post-class-switch expression of IgA and IgG, was successfully monitored during in vitro differentiation. We identified a number of unknown pathways engaged during B-cell activation, such as CXCL9/CXCL10 secretion by B cells. Finally, we evaluated a deduced set of biomarkers on a group of 18 patients with putative or proved intrinsic B-cell defects recruited from the European Society for Immunodeficiencies database and successfully predicted 2 AID defects and 1 DNA repair defect. Complete absence of class-switched B cells was a sensitive predictor of AID deficiency and should be further evaluated as a diagnostic biomarker.

CONCLUSION

The biomarkers found in this study could be used to further study the complex process of B-cell activation and to understand conditions that lead to the development of primary antibody deficiencies.

Memory B cell compartment constitution and susceptibility to recurrent lower respiratory tract infections in young children

A proportion of children have recurrent LRTIs, mostly as a result of Spn, which persist after 2 years of age. Here, we investigate, by flow cytofluorometry, the constitution of the memory B cell compartment in 90 healthy children and 49 children with recurrent LRTIs to determine if an increased susceptibility to recurrent LRTIs results from a delayed or abnormal ontogeny with poor antibody-mediated protection. Total IgA, IgM, IgG, and IgG subclasses were measured by nephelometry, as well as antipneumococcal antibodies by ELISA. Pneumococcal vaccination status was obtained. We show that the memory B cells increase between birth and 2 years of age (1.6% vs. 21.1%, P<0.001) without further significant increase noted per additional years (3-4 years old: 23.3%; 4-5 years old: 22.2%, P>0.40) to reach adult-like values (31.8±11.8%, P=0.08). Proportions of switched and IgM memory B cells were similar in children and adults. Comparatively, LRTI children had no delay in the constitution of their memory B cell compartment (2-3 years old: 26.9%; 3-4 years old: 18.2%; 4-5 years old: 26.8%, P>0.05). Their switched and IgM memory B cells were similar among age categories, and the distribution was overall similar to that of healthy controls. LRTI children had normal total and pneumococcal serotype-specific antibody values but showed a rapid waning of antipneumococcal antibody levels after vaccination. In summary, our results show that the memory B cell compartment is already similarly constituted at 2 years of age in healthy and LRTI children and thus, cannot explain the increased susceptibility to bacterial pneumonia. However, the waning of antibodies might predispose children to recurrent infections in the absence of revaccination.

Development of newborn and infant vaccines

Vaccines for early-life immunization are a crucial biomedical intervention to reduce global morbidity and mortality, yet their developmental path has been largely ad hoc, empiric, and inconsistent. Immune responses of human newborns and infants are distinct and cannot be predicted from those of human adults or animal models. Therefore, understanding and modeling age-specific human immune responses will be vital to the rational design and development of safe and effective vaccines for newborns and infants.

Investigation and management of Toxoplasma gondii infection in pregnancy and infancy: a prospective study

AIM

Toxoplasma gondii infection during pregnancy poses a serious risk to the fetus, therefore timely and accurate diagnosis is essential. The aim of this study was to estimate the frequency of congenital infection via evaluating mother's immunological status and the possibility to improving the diagnostic and therapeutic approaches.

METHODS

Eighty five mothers with Toxoplasma seroconversion and their offspring were enrolled (among them, 2 spontaneous abortions were documented in the first trimester). Prenatal PCR diagnosis was carried out on 50 patients (60%), with 7 positive cases (14%). Morphological ultrasound scanning revealed anomalies in one fetus. Long-term follow-up included general physical examinations, serological status tested using Western blot, neuro-radiological, ophthalmologic and neurologic examinations, psychological and developmental tests, visual evoked potential tests and audiology tests, as well as anti-Toxoplasma treatment regimes.

RESULTS

Fourteen (17%) of the infants were infected at one-year serological follow-up. Chi-square for linear trend of vertical transmission from the first to the third trimester was significant (P=0.009). Western blot analysis showed IgM and IgA in half of the infected infants. In 69 uninfected infants, anti-Toxoplasma IgG immunoblot analysis excluded infection within the 3 months in 18 infants (26%) and in the others within 6 months of life. The most relevant instrumental findings are described.

CONCLUSION

Western blot analysis may help to evaluate infection within the 6 months of life. The accuracy of ultrasound imaging to determine the brain damage in the fetus and newborns is doubtful, and should be combined with MR imaging. Multistep approaches can improve the timing of postnatal follow-up.

Tumor Necrosis Factor-Alpha and Mast Cells: Revisited Study

Mast cells reside in connective tissues and are widely recognized as effector cells important in innate and acquired immunity. These cells are the only ones capable of storing preformed TNFα in their cytoplasmatic granules and release upon activation. TNF-alpha is a potent multifunctional cytokine involved in autoimmune diseases, cancer, allergy, and acute and chronic inflammation. In this study, we revisit the interrelationship between TNFα and mast cells.