T Cell Subsets During Early Life and Their Implication in the Treatment of Childhood Acute Lymphoblastic Leukemia

The immune system plays a major role in recognizing and eliminating malignant cells, and this has been exploited in the development of immunotherapies aimed at either activating or reactivating the anti-tumor activity of a patient's immune system. A wide range of therapeutic approaches involving T lymphocytes, such as programmed cell death protein ligand-1 (PDL-1) inhibitors, cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) blockers, and CD19-targeted T-cell therapy through chimeric antigen receptor (CAR)-T cells or CD19/CD3 bi-specific T-cell engagers, have been introduced to the field of oncology, leading to significant improvements in overall survival of adult cancer patients. During the past few years, the availability and approval of T-cell based immunotherapies have become a reality also for the treatment of childhood cancers. However, the distribution, ratio of regulatory to effector cells and the quality of T-cell responses early in life are distinct from those during adolescence and adulthood, raising the possibility that these differences impact the efficacy of immunotherapy. Herein we provide a brief overview of the properties of conventional T cell subsets during early life. Focusing on the most common cancer type during childhood, acute lymphoblastic leukemia (ALL), we describe how current conventional therapies used against ALL influence the T-cell compartment of small children. We describe early life T-cell responses in relation to immunotherapies engaging T-cell anticancer reactivity and present our opinion that it is not only immaturity of the adaptive immune system, but also the impact of an immunosuppressive environment that may prove disadvantageous in the setting of immunotherapies targeting pediatric cancer cells.

The Feasibility of Host Transcriptome Profiling as a Diagnostic Tool for Microbial Etiology in Childhood Cancer Patients with Febrile Neutropenia

Infection is a common and serious complication of cancer treatment in children that often presents as febrile neutropenia (FN). Gene-expression profiling techniques can reveal transcriptional signatures that discriminate between viral, bacterial and asymptomatic infections in otherwise healthy children. Here, we examined whether gene-expression profiling was feasible in children with FN who were undergoing cancer treatment. The blood transcriptome of the children (n = 63) was investigated at time of FN diagnosed as viral, bacterial, co-infection or unknown etiology, respectively, and compared to control samples derived from 12 of the patients following the FN episode. RNA sequencing was successful in 43 (68%) of the FN episodes. Only two genes were significantly differentially expressed in the bacterial versus the control group. Significantly up-regulated genes in patients with the other three etiologies versus the control group were enriched with cellular processes related to proliferation and cellular stress response, with no clear enrichment with innate responses to pathogens. Among the significantly down-regulated genes, a few clustered into pathways connected to responses to infection. In the present study of children during cancer treatment, the blood transcriptome was not suitable for determining the etiology of FN because of too few circulating immune cells for reliable gene expression analysis.

Deficits in the IgG+ memory B-cell recovery after anthracycline treatment is confined to the spleen of rhesus macaques

Objectives

Loss of vaccine‐induced antibodies (Abs) after chemotherapy against paediatric acute lymphoblastic leukaemia (ALL) is common and often necessitates re‐immunisation after cessation of treatment. Even so, some ALL survivors fail to mount or to maintain protective Abs. Germinal centres (GCs) are clusters of proliferating B cells in follicles of secondary lymphoid tissues (SLTs) formed during adaptive immune responses and the origins of long‐lived memory B and plasma cells that are the source of Abs. Furthermore, productive GC reactions depend on T follicular helper (T_FH) cells. To understand why chemotherapy induces deficits in Ab responses, we examined how SLTs were affected by chemotherapy.

Methods

Rhesus macaques were infused with either three cycles of the anthracycline doxorubicin or saline, followed by immunisation with a de novo and booster antigen. Spleen and lymph nodes were removed, and memory B, bulk T and T_FH cells were examined.

Results

Despite adequate GC morphology, a diminished memory and IgG⁺ B‐cell population along with diminished total and booster vaccine‐specific IgG‐producing memory B cells were noted in the spleens of macaques with past doxorubicin exposure compared to the saline‐treated controls (P < 0.05). Intact bulk T and T_FH cells were found in the SLTs of treated macaques, which displayed higher CD40L upregulation capacity by their splenic CXCR5⁺ helper T cells (P < 0.01). In contrast to the spleen, the immune cell populations studied were comparable between the lymph nodes of both saline‐ and doxorubicin‐treated macaques.

Conclusion

Our findings suggest that the splenic memory B‐cell subset, compared to its lymph node counterpart, is more severely altered by anthracycline treatment.

Altered proportions of circulating CXCR5+ helper T cells do not dampen influenza vaccine responses in children with rheumatic disease

Biological therapy options for the treatment of rheumatic disease target molecules that can affect the cross-talk between innate and adaptive immune responses upon vaccination. Influenza vaccination in children with rheumatic disease has been recommended, but there are only sparse data on the quality of vaccine responses from pediatric patients treated with biological therapy. We conducted an influenza vaccine study over 3 consecutive seasons where the antibody response to TIV was evaluated in children with PRD (n = 78), including both non-treated (n = 17) and treated (with methotrexate, TNF-inhibitors with or without methotrexate, or IL-inhibitors, n = 61) children as well as healthy age-matched controls (n = 24). Peripheral B cells, T and NK cell populations, as well as CXCR5+ (follicular) helper T cells (T_FH) and chemokines involved in antibody responses were assessed prior to immunization in the same cohort. Data on disease duration, therapy and data on previous influenza vaccinations were retrieved. The proportion of circulating T_FH cells were significantly lower in non-treated children with PRD compared to treated patients and healthy controls. The significantly lower proportion of T_FH cells was mirrored by a marked significant increase in CXCL13 serum level, the ligand for CXCR5, with higher levels in non-treated children with PRD compared to treated patients and healthy controls. However, the proportion of T_FH cells or CXCL13 level at the time of vaccination was not a predictor of the antibody response to TIV in this cohort of children. Children with PRD had an overall similar response to TIV as healthy children. Although not significant, children treated with TNF-inhibitors differed as a few children remained seronegative towards H3N2- and influenza B viruses after immunization. Our data show that children with PRD respond to TIV as healthy children. Furthermore, plasma CXCL13 levels did not correlate to the proportion of T_FH cells in blood prior to immunisation, or to antibody responses following immunization.

Epstein-Barr Virus, but Not Cytomegalovirus, Latency Accelerates the Decay of Childhood Measles and Rubella Vaccine Responses-A 10-Year Follow-up of a Swedish Birth Cohort

BACKGROUND

Epstein-Barr virus (EBV) and cytomegalovirus (CMV) are ubiquitous and persistent herpesviruses commonly acquired during childhood. Both viruses have a significant impact on the immune system, especially through mediating the establishment of cellular immunity, which keeps these viruses under control for life. Far less is known about how these viruses influence B-cell responses.

OBJECTIVES

To evaluate the impact of latent EBV and CMV infection on rubella- and measles-specific antibody responses as well as on the B-cell compartment in a prospective birth cohort followed during the first 10 years of life.

METHODS

IgG titers against rubella and measles vaccines were measured in plasma obtained from the same donors at 2, 5, and 10 years of age. Peripheral B-cell subsets were evaluated ex vivo at 2 and 5 years of age. Factors related to optimal B-cell responses including IL-21 and CXCL13 levels in plasma were measured at all-time points.

RESULTS

EBV carriage in the absence of CMV associated with an accelerated decline of rubella and measles-specific IgG levels (p = 0.003 and p = 0.019, respectively, linear mixed model analysis), while CMV carriage in the absence of EBV associated with delayed IgG decay over time for rubella (p = 0.034). At 5 years of age, EBV but not CMV latency associated with a lower percentage of plasmablasts, but higher IL-21 levels in the circulation.

CONCLUSION

Our findings suggest that EBV carriage in the absence of CMV influences the B-cell compartment and the dynamics of antibody responses over time during steady state in the otherwise healthy host.

Associations between EBV and CMV Seropositivity, Early Exposures, and Gut Microbiota in a Prospective Birth Cohort: A 10-Year Follow-up

Early-life infections with persistent Epstein-Barr virus (EBV) and cytomegalovirus (CMV) are delayed in affluent countries, probably due to alterations in early environmental exposures, such as maternal age, siblings, and day-care attendance. We have previously reported that the timing of EBV and CMV contraction is related both to allergic sensitization and changes in functional competence of immune cells, while the presence/absence of lactobacilli [Lactobacillus (L.) casei, L. paracasei, and L. rhamnosus] or Staphylococcus (S.) aureus in feces is related to the risk for allergy. Here, we used the same prospective longitudinal birth cohort of children to investigate early-life environmental exposures and their influence on EBV and CMV contraction over time. Since gut microbes also belong to this category of early exposures, we investigated their association with herpesvirus contraction. Our results show that these two viruses are acquired with different kinetics and that EBV and CMV seroprevalence at 10 years of age was 47 and 57%, respectively. We also observed that a delayed EBV or CMV infection was associated with older maternal age [time ratio (TR) 1.14, 95% confidence interval (CI) 1.07-1.21, P adj < 0.001 and TR 1.09, CI 1.03-1.16, P adj = 0.008, respectively]. Further, we present the novel finding that S. aureus colonization reduced the time to CMV acquisition (TR 0.21, CI 0.06-0.78, P adj = 0.02). Together, these findings suggest that there is a relationship between timing of herpesvirus acquisition and early-life immune modulating exposures, which interestingly also includes the early infant gut microbiota.

Etiology of community acquired pneumonia among children in India: prospective, cohort study

Background

Childhood community acquired pneumonia (CAP) is a significant problem in developing countries, and confirmation of microbial etiology is important for individual, as well as public health. However, there is paucity of data from a large cohort, examining multiple biological specimens for diverse pathogens (bacteria and viruses). The Community Acquired Pneumonia Etiology Study (CAPES) was designed to address this knowledge gap.

Methods

We enrolled children with CAP (based on WHO IMCI criteria of tachypnea with cough or breathing difficulty) over 24 consecutive months, and recorded presenting symptoms, risk factors, clinical signs, and chest radiography. We performed blood and nasopharyngeal aspirate (NPA) bacterial cultures, and serology (Mycoplasma pneumoniae, Chlamydophila pneumoniae). We also performed multiplex PCR for 25 bacterial/viral species in a subgroup representing 20% of the cohort. Children requiring endotracheal intubation underwent culture and PCR of bronchoalveolar lavage (BAL) specimens.

Findings

We enrolled 2345 children. NPA and blood cultures yielded bacteria in only 322 (13.7%) and 49 (2.1%) children respectively. In NPA, Streptococcus pneumoniae (79.1%) predominated, followed by Haemophilus influenzae (9.6%) and Staphylococcus aureus (6.8%). In blood, S. aureus (30.6%) dominated, followed by S. pneumoniae (20.4%) and Klebsiella pneumoniae (12.2%). M. pneumoniae and C. pneumoniae serology were positive in 4.3% and 1.1% respectively. Multiplex PCR in 428 NPA specimens identified organisms in 422 (98.6%); of these 352 (82.2%) had multiple organisms and only 70 (16.4%) had a single organism viz. S. pneumoniae: 35 (50%), Cytomegalovirus (CMV): 13 (18.6%), Respiratory Syncytial Virus (RSV): 9 (12.9%), other viruses: 6 (8.7%), S. aureus: 5 (7.1%), and H. influenzae: 2 (2.9%). BAL PCR (n = 30) identified single pathogens in 10 (S. pneumoniae–3, CMV–3, S. aureus–2, H. influenzae–2) and multiple pathogens in 18 children. There were 108 (4.6%) deaths. The pattern of pathogens identified did not correlate with pneumonia severity or mortality.

Conclusions

The majority of children with CAP have multiple pathogens (bacteria and viruses). S. pneumoniae and S. aureus predominate in NPA and blood respectively. CMV and RSV were the dominant respiratory viruses in NPA and BAL. The presence of multiple pathogens, especially organisms associated with nasopharyngeal carriage, precludes confirmation of a causal relationship in most cases.

Pre-eclampsia affects cord blood NK cell expression of activation receptors and serum cytokine levels but not CB monocyte characteristics

PROBLEM

Maternal immunopathology in pre-eclampsia is well studied; however, less is known regarding the immunological effects on the newborns. Increased inflammation and activation of immune cells at the fetal-maternal interface in pre-eclampsia could influence the neonatal immune compartment.

METHOD OF STUDY

Monocytes and natural killer (NK) cells from cord blood (CB) of children with pre-eclamptic or healthy mothers were analyzed by flow cytometry for surface markers and intracellular cytokines. In addition, serum cytokine profiles were investigated using ELISA or cytometric bead array.

RESULTS

Neonates born to pre-eclamptic mothers had an inflammatory serum cytokine profile. While CB monocyte characteristics seemed unaffected, CB NK cells from pre-eclamptic pregnancies had higher NKp30, but borderline lower NKG2D expression.

CONCLUSION

In utero inflammatory priming of neonatal innate immunity taking place in pre-eclamptic pregnancies might influence specific NK cell functions in newborns.

Cytomegalovirus-seropositive children show inhibition of in vitro EBV infection that is associated with CD8+CD57+ T cell enrichment and IFN-γ

EBV, a human herpesvirus, is commonly acquired during childhood and persists latently in B cells. EBV seropositivity has been connected to immunomodulatory effects such as altered T and NK cell functional responses as well as protection against early IgE sensitization; however, owing to the asymptomatic presentation during childhood little is known regarding the infection process in children of different ages. In this study, we used mononuclear cells from cord blood and from 2- and 5-y-old EBV-naive children for in vitro EBV infection. We show that the degree of EBV-induced B cell activation and expansion differs between age groups and in particular in relationship to IFN-γ production capacity. EBV infection induced redistribution between B cell subsets with enrichment of IgD(+)CD27(+) cells (commonly referred to as non-switched memory) in infected cord blood cell cultures, and of IgD(-)CD27(+) cells (switched memory) in cell cultures from older children. We also related results to serostatus to CMV, a persistent herpesvirus that can affect differentiation status of T and NK cells. As compared with CMV(-) children, the EBV-induced enrichment of IgD(-)CD27(+) B cells was significantly reduced in infected cell cultures from CMV(+) children. This effect was associated with high levels of IFN-γ and frequencies of highly mature CD8(+)CD57(+) T cells in CMV(+) children. Our results demonstrate that both a child's age and serostatus to CMV will have an impact on EBV-induced B cell activation and expansion, and they point to the ability of viruses with immunomodulatory functions, such as CMV, to affect immune responses within the host system.

A glycosylation-dependent CD45RB epitope defines previously unacknowledged CD27⁻IgM(high) B cell subpopulations enriched in young children and after hematopoietic stem cell transplantation

The immune system is dysfunctional for years after hematopoietic stem cell transplantation (HSCT). A potential cause is an intrinsic B cell deficiency. In a cohort of pediatric HSCT patients few CD27(+) B cells formed after transplantation with the number of CD27(+)IgM(high) cells more affected than class-switched ones. A previously unacknowledged population of CD27(-)IgM(high) cells made up the majority of B cells and this population was also enlarged in healthy children compared to adults. Only a minority of these CD27(-)IgM(high) B cells expressed markers typical for transitional B cells, and the non-transitional CD27(-)IgM(high) cells could be further divided into subpopulations based on their ability to extrude the dye Rhodamine 123 and their expression of CD45RB(MEM55), a glycosylation-dependent epitope. Thus, we define several novel human CD27(-)IgM(high) B cell subpopulations in blood, all of which are present in higher frequencies and numbers in young children and after HSCT than in adults.

NKG2C+CD57+ CD56dim NK cells are enriched following Epstein-Barr virus transformed lymphoblastoid cell line co-culture with peripheral blood mononuclear cells from cytomegalovirus+ donors (P4359)

Cytomegalovirus (CMV) is a persistent herpesvirus that promotes NKG2C+ Natural Killer (NK) cell differentiation. Highly mature CD57+ NKG2C+ NK cells have been proposed as the equivalent of mouse memory-like NK cells, which have features as long-term persistence and enhanced recall responses. AIM: To examine if co-infection with another common herpesvirus, Epstein-Barr virus (EBV), affects the NKG2C+ CD56dim NK cell population. METHODS: PBMCs from 45 five-year old children with known EBV and CMV serostatus were phenotyped. Further, PBMCs from 6 CMV sero+ EBV sero- infants were used for co-culture with EBV+ lymphoblastoid cell-lines (LCLs) during 72 hours. EBV- LCLs (Ramos) served as controls. Anti CD3, CD14, CD19, CD56, CD57, NKG2C and ki-67 antibodies were used for flow cytometric analysis. RESULTS: EBV and CMV co-infection was related to higher proportions of NKG2C+ and NKG2C+CD57+ CD56dim NK cells compared to infection with CMV or EBV alone, or seronegativity. In contrast to co-culture with Ramos, PBMC co-culture with EBV+ LCLs generally led to enrichment of NKG2C+CD57+ NK cells (stimulation index median 1.23, range 0.87-1.30), which was not related with higher NK cell proliferation. CONCLUSIONS: EBV co-infection seems to promote the existence of higher proportions of memory-like NK cells. Our data herein indicate that this is not due to enhanced proliferation of these cells; rather it suggests that memory-like NK cells may be maintained by EBV co-infection.

Cord blood monocyte subsets are similar to adult and show potent peptidoglycan-stimulated cytokine responses

Human monocytes can be divided into two major subpopulations, CD14(++) CD16(-) and CD14(+) CD16(+) cells, which are suggested to play different roles in antimicrobial responses. In neonates, characteristics and functional responses of monocyte subsets have not previously been explored, and might contribute to the qualitative difference between neonatal and adult cytokine profiles. We report that at baseline, monocyte subsets in cord blood and adult peripheral blood are present in similar frequencies, and show similar expression of CD11c, CD80/CD86, CD163 and HLA-DR. In response to the bacterial ligand peptidoglycan, cord blood monocytes had high inherent capacity for production of the early-response cytokines with levels of tumour necrosis factor and interleukin-12p70 exceeding adult levels, and also a higher phosphorylation of p38-mitogen-activated protein kinase. The CD14(+) CD16(+) cells expressed more interleukin-12p70 than CD14(++) CD16(-) cells and were present in a higher frequency in peptidoglycan-stimulated cord blood mononuclear cell cultures. Together, the behaviour of cord blood CD14(+) CD16(+) cells following peptidoglycan stimulation might indicate a qualitative difference between the neonatal antimicrobial response and that of the adult. In addition we found that serum factors in cord blood and adult sera affected cytokine production similarly, with the exception of tumour necrosis factor, regardless of the source of serum or cells. Overall, our data provide new insights into monocyte heterogeneity in cord blood and monocyte subset responses to a bacterial ligand at birth.

Impaired Toll-like receptor 2 signalling in monocytes from 5-year-old allergic children

The relative composition of the two major monocytic subsets CD14(+)CD16(-) and CD14(+)CD16(+) is altered in some allergic diseases. These two subsets display different patterns of Toll-like receptor levels, which could have implications for activation of innate immunity leading to reduced immunoglobulin E-specific adaptive immune responses. This study aimed to investigate if allergic status at the age of 5 years is linked to differences in monocytic subset composition and their Toll-like receptor levels, and further, to determine if Toll-like receptor regulation and cytokine production upon microbial stimuli is influenced by the allergic phenotype. Peripheral blood mononuclear cells from 5-year-old allergic and non-allergic children were stimulated in vitro with lipopolysaccharide and peptidoglycan. Cells were analysed with flow cytometry for expression of CD14, Toll-like receptors 2 and 4 and p38-mitogen-activated protein kinase (MAPK). The release of cytokines and chemokines [tumour necrosis factor, interleukin (IL)-1 beta, IL-6, IL-8, IL-10, IL-12p70] into culture supernatants was measured with cytometric bead array. For unstimulated cells there were no differences in frequency of the monocytic subsets or their Toll-like receptor levels between allergic and non-allergic children. However, monocytes from allergic children had a significantly lower up-regulation of Toll-like receptor 2 upon peptidoglycan stimulation. Further, monocytes from allergic children had a higher spontaneous production of IL-6, but there were no differences between the two groups regarding p38-MAPK activity or cytokine and chemokine production upon stimulation. The allergic subjects in this study have a monocytic population that seems to display a hyporesponsive state as implicated by impaired regulation of Toll-like receptor 2 upon peptidoglycan stimulation.

Herpesvirus seropositivity in childhood associates with decreased monocyte-induced NK cell IFN-gamma production

EBV infection is inversely associated with IgE sensitization in children, and this association is further enhanced by CMV coinfection. In mice, herpesvirus latency causes systemic innate activation and protection from bacterial coinfection, implying the importance of herpesviruses in skewing immune responses during latent infection. Early control of viral infections depends on IFN-gamma release by NK cells, which generally requires the presence of accessory cells. We investigated IFN-gamma production by NK cells in PBMCs from children seropositive (SP) for EBV alone, for both EBV and CMV, or seronegative for both viruses. The ability of classical (CD14(++)CD16(-)) and proinflammatory (CD14(+)CD16(+)) monocytes to induce autologous NK cell IFN-gamma was studied by coculture experiments with enriched CD3(-)CD56(+) cells. Transwell experiments were used to evaluate how monocytes interact with NK cells to induce IFN-gamma synthesis. SP children had a significantly reduced proportion of IFN-gamma(+) NK cells and cognate intracellular IFN-gamma levels, which was more pronounced in CMV-coinfected subjects. Also, resting PBMCs of SP children displayed lower proportions of proinflammatory monocytes. IFN-gamma production by NK cells was dependent on interactions with monocytes, with the proinflammatory subset inducing the highest IFN-gamma. Finally, SP children had markedly lower levels of plasma IFN-gamma, concurrent with in vitro findings. Herpesvirus infections could be one contributing factor for maturation toward balanced Th1-Th2 responses. Our data indicate that early infection by herpesviruses may affect NK cell and monocyte interactions and thereby also influence the development of allergies.

Maternal allergy influences p38-mitogen-activated protein kinase activity upon microbial challenge in CD14+ monocytes from 2-year-old children

BACKGROUND

The development of allergic diseases is dependent on genetic and environmental factors. It has been shown previously that cord blood mononuclear cells (CBMCs) from infants with parental allergy have altered cytokine profiles upon bacterial encounter; it might be possible that such impairment persists during the early years of childhood.

OBJECTIVE

The aim of this study was to investigate anti-microbial responses with regard to p38-mitogen-activated protein kinase (MAPK) activity in CD14(+) monocytes and IL-6 release from mononuclear cells in the same group of children at birth and at 2 years of age. Methods Paired samples of CBMCs and peripheral blood mononuclear cells (PBMCs) were stimulated with either lipopolysaccharide (LPS) or peptidoglycan in vitro. CD14(+) monocytes were analysed for p38-MAPK activity by flow cytometry, and soluble IL-6 receptor, soluble glycoprotein130 and IL-6 release from PBMC cultures were quantified by ELISA.

RESULTS

CBMCs from newborns with allergic mothers tended to have a lower IL-6 response following an LPS (P=0.09) challenge compared with the group without maternal allergy while p38-MAPK activation levels did not differ between the groups. PBMCs from 2-year-olds with allergic mothers released significantly less (P<0.05) IL-6 upon peptidoglycan stimuli compared with age-matched infants with non-allergic mothers. Infants with allergic mothers displayed markedly reduced CD14(+) monocyte p38-MAPK phosphorylation after LPS (P<0.05) and peptidoglycan (P<0.01) challenge. This altered anti-microbial response was attributed to maternal allergy rather than to being IgE-sensitized at 2 years of age.

CONCLUSION

Monocytes from children with allergic mothers are less responsive to bacterial challenge than monocytes from children with non-allergic mothers, and this impairment persists during the first 2 years of infancy.