Uninfected but not unaffected: chronic maternal infections during pregnancy, fetal immunity, and susceptibility to postnatal infections

Development of immunity in early life

The immune system in early life goes through rapid and radical changes. Early life is also the period with the highest risk of infections. The foetal immune system is programmed to coexist with foreign antigenic influences in utero, and postnatally to rapidly develop a functional system capable of distinguishing helpful microbes from harmful pathogens. Both host genetics and environmental influences shape this dramatic transition and direct the trajectory of the developing immune system into early childhood and beyond. Given the malleability of the immune system in early life, interventions aimed at modulating this trajectory thus have the potential to translate into considerable reductions in infectious disease burden with immediate as well as long-lasting benefit. However, an improved understanding of the underlying molecular drivers of early life immunity is prerequisite to optimise such interventions and transform the window of early life vulnerability into one of opportunity.

Recent developments in malaria vaccinology

The development of a highly effective malaria vaccine remains a key goal to aid in the control and eventual eradication of this devastating parasitic disease. The field has made huge strides in recent years, with the first-generation vaccine RTS,S showing modest efficacy in a Phase III clinical trial. The updated 2030 Malaria Vaccine Technology Roadmap calls for a second generation vaccine to achieve 75% efficacy over two years for both Plasmodium falciparum and Plasmodium vivax, and for a vaccine that can prevent malaria transmission. Whole-parasite immunisation approaches and combinations of pre-erythrocytic subunit vaccines are now reporting high-level efficacy, whilst exciting new approaches to the development of blood-stage and transmission-blocking vaccine subunit components are entering clinical development. The development of a highly effective multi-component multi-stage subunit vaccine now appears to be a realistic ambition. This review will cover these recent developments in malaria vaccinology.

Tolerance of the newborn to antiretroviral drug exposure in utero

INTRODUCTION

The prevention of mother-to-child HIV-1 transmission by antiretroviral drug treatment is remarkably effective. The risk of transmission to the child is now almost zero for women optimally treated during pregnancy. The rapid expansion of this prophylactic treatment has led the World Health Organization to aspire to the virtual elimination of mother-to-child transmission and pediatric AIDS over the next few years. In 2014, more than 900,000 women worldwide were treated with antiretroviral drugs during pregnancy. The issue of fetal and neonatal antiretroviral drug tolerance is therefore extremely important.

AREAS COVERED

This review focuses on the possible impact of in utero exposure to antiretroviral drug on newborn health. To restrict analysis to this period is justified by the specificities of transplacental drug exposure and fetal vulnerability. Relevant data are available from trials and observational cohorts. The significance of various bio-markers detectable at birth is still unresolved, but merits a careful evaluation. Long-term assessment is associated with various logistical difficulties.

EXPERT OPINION

The health of 'exposed but not infected' children poses no major problem in the immense majority of cases, but a series of biological, clinical and imaging-based warning signs have emerged indicating the need for careful attention to be paid to this issue. Some effects that are straightforward to manage in industrialized countries may have more severe consequences in countries in which access to effective healthcare is limited. Nucleoside/nucleotide analogs are potentially genotoxic to mitochondrial and nuclear DNA, and the principal question to be addressed concerns their potential long-term effects.

Influence of maternal infections on neonatal acute phase proteins and their interaction in the development of non-affective psychosis

Although primary infections with Toxoplasma gondii or herpes viruses during pregnancy are established teratogens, chronic maternal infections with these pathogens are considered far less serious. However, such chronic infections have been associated with neuropsychiatric disorders in the offspring. The risks of non-affective psychoses, including schizophrenia, in offspring associated with these exposures during pregnancy have not been completely defined. We used data from neonatal dried blood samples from 199 cases of non-affective psychosis and 525 matched controls (born 1975-1985). We measure immunoglobulin G antibodies directed at T. gondii, cytomegalovirus and herpes simplex virus type-1 and -2, as well as levels of nine acute phase proteins (APPs). We assessed the interaction between maternal antibodies and neonatal APP in terms of risk of non-affective psychosis. Among controls, maternal exposure to T. gondii or cytomegalovirus, but not to the other herpes viruses, was associated with significantly higher levels of neonatal APPs. Among cases, none of the maternal exposures were associated with any significant change in APPs. We observed increased RR for non-affective psychosis associated with maternal infection with T. gondii (odds ratio 2.1, 95% confidence interval 1.1-4.0) or cytomegalovirus (1.7, 0.9-3.3) only among neonates with low APP levels. These findings suggest that chronic maternal infection with T. gondii or cytomegalovirus affect neonatal markers of innate immunity. Deficient fetal immune responses in combination with maternal chronic infections may contribute to subsequent risk for psychosis. A greater understanding of the maternal-fetal immunological interplay may ultimately lead to preventive strategies toward neuropsychiatric disorders.

The impact of HIV exposure and maternal Mycobacterium tuberculosis infection on infant immune responses to bacille Calmette-Guérin vaccination

Objective:

The objective of this study is to assess the effect of maternal HIV and Mycobacterium tuberculosis (Mtb) infection on cellular responses to bacille Calmette-Guérin (BCG) immunization.

Design:

A mother–infant cohort study.

Methods:

Samples were collected from mother–infant pairs at delivery. Infants were BCG-vaccinated at 6 weeks of age and a repeat blood sample was collected from infants at 16 weeks of age. BCG-specific T-cell proliferation and intracellular cytokine expression were measured by flow cytometry. Secreted cytokines and chemokines in cell culture supernatants were analysed using a Multiplex assay.

Results:

One hundred and nine (47 HIV-exposed and 62 HIV-unexposed) mother–infants pairs were recruited after delivery and followed longitudinally. At birth, proportions of mycobacteria-specific proliferating T cells were not associated with either in-utero HIV exposure or maternal Mtb sensitization. However, in-utero HIV exposure affected infant-specific T-cell subsets [tumour necrosis factor-alpha (TNF-α) single positive proliferating CD4⁺ T cells and interferon-gamma (IFN-γ), TNF-α dual-positive CD4⁺ T cells]. Levels of TNF-α protein in cell culture supernatants were also significantly higher in HIV-exposed infants born to Mtb-sensitized mothers. In the presence of maternal Mtb sensitization, frequencies of maternal and newborn BCG-specific proliferating CD4⁺ T cells were positively correlated. Following BCG vaccination, there was no demonstrable effect of HIV exposure or maternal Mtb infection on infant BCG-specific T-cell proliferative responses or concentrations of secreted cytokines and chemokines.

Conclusion:

Effects of maternal HIV and Mtb infection on infant immune profiles at birth are transient only, and HIV-exposed, noninfected infants have the same potential to respond to and be protected by BCG vaccination as HIV-unexposed infants.

Expression and function of endothelial selectins during human development

Leucocyte trafficking is vital for the immune defence. In adults, early tethering and rolling interactions between leucocytes and endothelial cells are mediated by P-, E- and L-selectins and their ligands. In contrast, the role of selectins in migration of mononuclear cells during fetal development in humans remains unknown. We studied the functions of endothelial E- and P-selectins and their counter-receptors during human ontogeny. Immunohistochemical stainings showed that P-selectin is expressed in megakaryocytes and endothelial cells starting from gestational weeks 7 and 11, respectively. Endothelial E-selectin appeared latest, at week 32. Real-time imaging using in vitro flow chamber assays showed that cord blood mononuclear leucocytes used E-, P- and L-selectin and PSGL-1 to roll on and adhere to endothelium under physiological shear stress. These data show that selectins are synthesized and functional before birth in humans and have the potential to mediate the emigration of mononuclear cells and inflammatory responses.

Pregnancy and helminth infections

It has been proposed that helminth infection may be particularly detrimental during pregnancy, through adverse effects on maternal anaemia and on birth outcomes, and that anthelminthic treatment during pregnancy will therefore be particularly beneficial. However, the few treatment trials that have been conducted have given, but little support to this notion and further trials in settings of nutritional stress are needed. It has also been proposed that prenatal exposure to helminth infection has an important effect on the development of the foetal immune response. There is evidence that this may impact, long-term, upon responses to helminth and nonhelminth antigens, and to allergens. Exposure to helminths in utero may also have nonspecific effects that may modify the offspring's susceptibility to diseases mediated by inflammation, including metabolic disorders. The mechanisms of such effects are not known, but they deserve to be explored as current epidemiological findings suggest the possibility of primary prevention for inflammatory conditions such as allergy, through intervention during pregnancy.

The role of environmental factors in modulating immune responses in early life

The concept of immunological memory stipulates that past exposures shape present immune function. These exposures include not only specific antigens impacting adaptive immune memory but also conserved pathogen or danger associated molecular patterns that mold innate immune responses for prolonged periods of time. It should thus not come as a surprise that there is a vast range of external or environmental factors that impact immunity. The importance of environmental factors modulating immunity is most readily recognized in early life, a period of rapidly changing environments. We here summarize available data on the role of environment shaping immune development and from it derive an overarching hypothesis relating the underlying molecular mechanisms and evolutionary principles involved.

Efficacy and safety of the RTS,S/AS01 malaria vaccine during 18 months after vaccination: a phase 3 randomized, controlled trial in children and young infants at 11 African sites

BACKGROUND

A malaria vaccine could be an important addition to current control strategies. We report the safety and vaccine efficacy (VE) of the RTS,S/AS01 vaccine during 18 mo following vaccination at 11 African sites with varying malaria transmission.

METHODS AND FINDINGS

6,537 infants aged 6-12 wk and 8,923 children aged 5-17 mo were randomized to receive three doses of RTS,S/AS01 or comparator vaccine. VE against clinical malaria in children during the 18 mo after vaccine dose 3 (per protocol) was 46% (95% CI 42% to 50%) (range 40% to 77%; VE, p<0.01 across all sites). VE during the 20 mo after vaccine dose 1 (intention to treat [ITT]) was 45% (95% CI 41% to 49%). VE against severe malaria, malaria hospitalization, and all-cause hospitalization was 34% (95% CI 15% to 48%), 41% (95% CI 30% to 50%), and 19% (95% CI 11% to 27%), respectively (ITT). VE against clinical malaria in infants was 27% (95% CI 20% to 32%, per protocol; 27% [95% CI 21% to 33%], ITT), with no significant protection against severe malaria, malaria hospitalization, or all-cause hospitalization. Post-vaccination anti-circumsporozoite antibody geometric mean titer varied from 348 to 787 EU/ml across sites in children and from 117 to 335 EU/ml in infants (per protocol). VE waned over time in both age categories (Schoenfeld residuals p<0.001). The number of clinical and severe malaria cases averted per 1,000 children vaccinated ranged across sites from 37 to 2,365 and from -1 to 49, respectively; corresponding ranges among infants were -10 to 1,402 and -13 to 37, respectively (ITT). Meningitis was reported as a serious adverse event in 16/5,949 and 1/2,974 children and in 9/4,358 and 3/2,179 infants in the RTS,S/AS01 and control groups, respectively.

CONCLUSIONS

RTS,S/AS01 prevented many cases of clinical and severe malaria over the 18 mo after vaccine dose 3, with the highest impact in areas with the greatest malaria incidence. VE was higher in children than in infants, but even at modest levels of VE, the number of malaria cases averted was substantial. RTS,S/AS01 could be an important addition to current malaria control in Africa.

TRIAL REGISTRATION

www.ClinicalTrials.gov NCT00866619 Please see later in the article for the Editors' Summary.

Altered innate immune development in HIV-exposed uninfected infants

BACKGROUND

Early in life, HIV-exposed uninfected (HEU) infants are at an increased risk of morbidity and mortality from infectious disease compared with HIV-unexposed (UE) infants. To improve our understanding of the mechanisms underlying their increased risk, we contrasted innate immune development between HEU and UE infants in a developing world setting, where early life infectious disease risk is exceptionally high.

METHODS

A prospective longitudinal cohort of HEU and UE newborns was established, and the most detailed characterization to date of HEU infant immune development was performed. Single-cell cytokine production was analyzed by flow cytometry after stimulation of whole blood with pathogen-associated molecular patterns (PAMPs).

RESULTS

Monocyte, classical dendritic cell, and plasmacytoid dendritic cell composition was similar between HEU and UE infants throughout the first year of life. However, HEU mononuclear cells mounted an enhanced pro-inflammatory response to PAMP stimulation, both in quantity of cytokine produced per cell and in proportion of responder cells. Significant differences in cytokine production were detected on the single-cell level in a PAMP-specific pattern, but only at 2 and 6 weeks of age; all differences normalized by 12 months of age.

CONCLUSIONS

This time course of innate immune deviation early in life corresponds to the clinical window of vulnerability to infections in HEU infants and may be at least partially responsible for their increased morbidity and mortality from infectious disease.

Impact of maternal HIV-1 viremia on lymphocyte subsets among HIV-exposed uninfected infants: protective mechanism or immunodeficiency

BACKGROUND

Reports of increased morbidity and mortality from infectious diseases among HIV Exposed Uninfected (HEU) infants have raised concern about a possible underlying immunodeficiency among them. The objective of this study was to assess the immunological profile of HEU infants born to mothers exhibiting different levels of HIV-1 viremia at the time of delivery.

METHODS

Study subjects were enrolled in the Centre maternel et infantile sur le SIDA (CMIS) mother-child cohort between 1997 and 2010 (n =585). Infant CD4+ T cell, CD8+ T cell and CD19+ B cell counts were assessed at 2 and 6 months of age, and compared among HEU infants in groups defined by maternal viral load (VL) at the time of delivery (VL < 50 copies/ml, VL 50-1000 copies/ml, and VL > 1000 copies/ml) in a multivariable analysis.

RESULTS

At 2 months of age, infants born to mothers with VL > 1000 copies/ml had lower CD4+ T cell counts compared to those born to mothers with VL < 50 copies/ml at the time of delivery (44.3% versus 48.3%, p = 0.007, and 2884 vs. 2432 cells/mm3, p = 0.02). These differences remained significant after adjusting for maternal and infant antiretroviral drug use, gender, race and gestational age, and persisted at 6 months of age. There were no differences in CD8+ T cell count or absolute CD19+ B cell count between groups, though higher CD19+ B cell percentage was seen among infants born to mothers with VL > 1000 copies/ml.

CONCLUSIONS

These results suggest that exposure to high levels of HIV-1 viremia in utero, even in the absence of perinatal transmission, may affect the infant's developing immune system. While further work needs to be done to confirm these findings, they reinforce the need for optimal treatment of HIV infected pregnant women, and careful follow-up of HEU infants.

HIV-exposed uninfected children: a growing population with a vulnerable immune system?

Through the successful implementation of policies to prevent mother-to-child-transmission (PMTCT) of HIV-1 infection, children born to HIV-1-infected mothers are now much less likely to acquire HIV-1 infection than previously. Nevertheless, HIV-1-exposed uninfected (HEU) children have substantially increased morbidity and mortality compared with children born to uninfected mothers (unexposed uninfected, UU), predominantly from infectious causes. Moreover, a range of phenotypical and functional immunological differences between HEU and UU children has been reported. As the number of HEU children continues to increase worldwide, two questions with clear public health importance need to be addressed: first, does exposure to HIV-1 and/or ART in utero or during infancy have direct immunological consequences, or are these poor outcomes simply attributable to the obvious disadvantages of being born into an HIV-affected household? Secondly, can we expect improved maternal care and ART regimens during and after pregnancy, together with optimized infant immunization schedules, to reduce the excess morbidity and mortality of HEU children?

Listeria monocytogenes: a promising vehicle for neonatal vaccination

Vaccination as a medical intervention has proven capable of greatly reducing the suffering from childhood infectious disease. However, newborns and infants in particular are age groups for whom adequate vaccine-mediated protection is still largely lacking. With the challenges that the neonatal immune system faces and the required highest level of stringency for safety, designing vaccines for early life in general and the newborn in particular poses great difficulty. Nevertheless, recent advances in our understanding of neonatal immunity and its responses to vaccines and adjuvants suggest that neonatal vaccination is a task fully within reach. Among the most promising developments in neonatal vaccination is the use of Listeria monocytogenes (Lm) as a delivery platform. In this review, we will outline key properties of Lm that make it such an ideal neonatal and early life vaccine vehicle, and also discuss potential constraints of Lm as a vaccine delivery platform.

Biomarkers and neurodevelopment in perinatally HIV-infected or exposed youth: a structural equation model analysis

OBJECTIVE

To examine the relationship between markers of vascular dysfunction and neurodevelopmental outcomes in perinatally HIV-infected (PHIV+) and perinatally HIV-exposed but uninfected (PHEU) youth.

DESIGN

Cross-sectional design within a prospective, 15-site US-based cohort study.

METHODS

Neurodevelopmental outcomes were evaluated in relation to nine selected vascular biomarkers in 342 youth (212 PHIV+, 130 PHEU). Serum levels were assessed for adiponectin, C-reactive protein (CRP), fibrinogen, interleukin-6 (IL-6), soluble vascular cell adhesion molecule-1 (sVCAM-1), E-selectin (sE-selectin), monocyte chemoattractant protein (sMCP-1), intercellular adhesion molecule-1 (sICAM-1), and P-selectin (sP-selectin). The Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) was administered at entry, yielding a Full-Scale IQ score, and four index scores. Factor analysis was conducted to reduce the biomarkers to fewer factors with related biological roles. Structural equation models (SEMs) were used to measure associations between resulting factors and WISC-IV scores.

RESULTS

Mean participant age was 11.4 years, 54% were female, 70% black. The nine biomarkers were clustered into three factor groups: F1 (fibrinogen, CRP, and IL-6); F2 (sICAM-1 and sVCAM-1); and F3 (MCP-1, sP-selectin, and sE-selectin). Adiponectin showed little correlation with any factor. SEMs revealed significant negative association of F1 with WISC-IV processing speed score in the total cohort. This effect remained significant after adjusting for HIV status and other potential confounders. A similar association was observed when restricted to PHIV+ participants in both unadjusted and adjusted SEMs.

CONCLUSION

Aggregate measures of fibrinogen, CRP, and IL-6 may serve as a latent biomarker associated with relatively decreased processing speed in both PHIV+ and PHEU youth.

Immunology of pediatric HIV infection

Most infants born to human immunodeficiency virus (HIV)-infected women escape HIV infection. Infants evade infection despite an immature immune system and, in the case of breastfeeding, prolonged repetitive exposure. If infants become infected, the course of their infection and response to treatment differs dramatically depending upon the timing (in utero, intrapartum, or during breastfeeding) and potentially the route of their infection. Perinatally acquired HIV infection occurs during a critical window of immune development. HIV's perturbation of this dynamic process may account for the striking age-dependent differences in HIV disease progression. HIV infection also profoundly disrupts the maternal immune system upon which infants rely for protection and immune instruction. Therefore, it is not surprising that infants who escape HIV infection still suffer adverse effects. In this review, we highlight the unique aspects of pediatric HIV transmission and pathogenesis with a focus on mechanisms by which HIV infection during immune ontogeny may allow discovery of key elements for protection and control from HIV.

Cord blood Vγ2Vδ2 T cells provide a molecular marker for the influence of pregnancy-associated malaria on neonatal immunity

BACKGROUND

Plasmodium falciparum placental infection primes the fetal immune system and alters infant immunity. Mechanisms leading to these outcomes are not completely understood. We focused on Vγ2Vδ2 cells, which are part of the immune response against many pathogens, including P. falciparum. These unconventional lymphocytes respond directly to small, nonpeptidic antigens, independent of major histocompatibility complex presentation. We wondered whether placental malaria, which may increase fetal exposure to P. falciparum metabolites, triggers a response by neonatal Vγ2Vδ2 lymphocytes that can be a marker for the extent of fetal exposure to malarial antigens.

METHODS

Cord blood mononuclear cells were collected from 15 neonates born to mothers with P. falciparum infection during pregnancy (8 with placental malaria) and 25 unexposed neonates. Vγ2Vδ2 cell phenotype, repertoire, and proliferative responses were compared between newborns exposed and those unexposed to P. falciparum.

RESULTS

Placental malaria-exposed neonates had increased proportions of central memory Vγ2Vδ2 cells in cord blood, with an altered Vγ2 chain repertoire ex vivo and after stimulation.

CONCLUSION

Our results suggest that placental malaria affects the phenotype and repertoire of neonatal Vγ2Vδ2 lymphocytes. Placental malaria may lower the capacity for subsequent Vγ2Vδ2 cell responses and impair the natural resistance to infectious diseases or the response to pediatric vaccination.

From mice to women: the conundrum of immunity to infection during pregnancy

Resistance to infection is the ability of the host to evoke a strong immune response sufficient to eliminate the infectious agent. In contrast, maternal tolerance to the fetus necessitates careful regulation of immune responses. Successful pregnancy requires the maternal host to effectively balance the opposing processes of maternal immune reactivity and tolerance to the fetus. However, this balance can be perturbed by infections which are recognized as the major cause of adverse pregnancy outcome including pre-term labor. Select pathogens also pose a serious threat of severe maternal illness. These include intracellular and chronic pathogens that have evolved immune evasive strategies. Murine models of intracellular bacteria and parasites that mimic pathogenesis of infection in humans have been developed. While human epidemiological studies provide insight into maternal immunity to infection, experimental infection in pregnant mice is a vital tool to unravel the complex molecular mechanisms of placental infection, congenital transmission and maternal illness. We will provide a comprehensive review of the pathogenesis of several infection models in pregnant mice and their clinical relevance. These models have revealed the immunological function of the placenta in responding to, and resisting infection. Murine feto-placental infection provides an effective way to evaluate new intervention strategies for managing infections during pregnancy, adverse fetal outcome and long-term effects on the offspring and mother.

[Pediatric aids, 30 years later]

Thirty years after the first descriptions of AIDS in children in May 1983, the risk of viral transmission from mother to child has been reduced to almost zero and the disease in infected children has become an asymptomatic condition, stable in the long-term, thanks to antiretroviral drugs. Unbelievable though it may have seemed until the mid-1990s, children infected during the perinatal period are now growing up to be adults in a chronic, stable, asymptomatic medical condition with often satisfactory personal, family, and social lives. The French perinatal epidemiological cohort, which was set up in 1984 and has included more than 18,000 mother-child pairs to date, traces the steps in this extraordinary revolution in the prevention and treatment of HIV-1 infection in children.

TLR7/TLR8 Activation Restores Defective Cytokine Secretion by Myeloid Dendritic Cells but Not by Plasmacytoid Dendritic Cells in HIV-Infected Pregnant Women and Newborns

Mother-to-child transmission (MTCT) of HIV-1 has been significantly reduced with the use of antiretroviral therapies, resulting in an increased number of HIV-exposed uninfected infants. The consequences of HIV infection on the innate immune system of both mother-newborn are not well understood. In this study, we analyzed peripheral blood and umbilical cord blood (CB) collected from HIV-1-infected and uninfected pregnant women. We measured TNF-α, IL-10 and IFN-α secretion after the stimulation of the cells with agonists of both extracellular Toll-like receptors (TLRs) (TLR2, TLR4 and TLR5) and intracellular TLRs (TLR7, TLR7/8 and TLR9). Moreover, as an indicator of the innate immune response, we evaluated the responsiveness of myeloid dendritic cells (mDCs) and plasmacytoid DCs (pDCs) to TLRs that are associated with the antiviral response. Our results showed that peripheral blood mononuclear cells (PBMCs) from HIV-1-infected mothers and CB were defective in TNF-α production after activation by TLR2, TLR5, TLR3 and TLR7. However, the TNF-α response was preserved after TLR7/8 (CL097) stimulation, mainly in the neonatal cells. Furthermore, only CL097 activation was able to induce IL-10 and IFN-α secretion in both maternal and CB cells in the infected group. An increase in IFN-α secretion was observed in CL097-treated CB from HIV-infected mothers compared with control mothers. The effectiveness of CL097 stimulation was confirmed by observation of similar mRNA levels of interferon regulatory factor-7 (IRF-7), IFN-α and TNF-α in PBMCs of both groups. The function of both mDCs and pDCs was markedly compromised in the HIV-infected group, and although TLR7/TLR8 activation overcame the impairment in TNF-α secretion by mDCs, such stimulation was unable to reverse the dysfunctional type I IFN response by pDCs in the HIV-infected samples. Our findings highlight the dysfunction of innate immunity in HIV-infected mother-newborn pairs. The activation of the TLR7/8 pathway could function as an adjuvant to improve maternal-neonatal innate immunity.

Malaria modifies neonatal and early-life toll-like receptor cytokine responses

Protection from infections in early life relies extensively on innate immunity, but it is unknown whether and how maternal infections modulate infants' innate immune responses, thereby altering susceptibility to infections. Plasmodium falciparum causes pregnancy-associated malaria (PAM), and epidemiological studies have shown that PAM enhances infants' susceptibility to infection with P. falciparum. We investigated how PAM-mediated exposures in utero affect innate immune responses and their relationship with infection in infancy. In a prospective study of mothers and their babies in Benin, we investigated changes in Toll-like receptor (TLR)-mediated cytokine responses related to P. falciparum infections. Whole-blood samples from 134 infants at birth and at 3, 6, and 12 months of age were stimulated with agonists specific for TLR3, TLR4, TLR7/8, and TLR9. TLR-mediated interleukin 6 (IL-6) and IL-10 production was robust at birth and then stabilized, whereas tumor necrosis factor alpha (TNF-α) and gamma interferon (IFN-γ) responses were weak at birth and then increased. In multivariate analyses, maternal P. falciparum infections at delivery were associated with significantly higher TLR3-mediated IL-6 and IL-10 responses in the first 3 months of life (P < 0.05) and with significantly higher TLR3-, TLR7/8-, and TLR9-mediated TNF-α responses between 6 and 12 months of age (P < 0.05). Prospective analyses showed that higher TLR3- and TLR7/8-mediated IL-10 responses at birth were associated with a significantly higher risk of P. falciparum infection in infancy (P < 0.05). Neonatal and infant intracellular TLR-mediated cytokine responses are conditioned by in utero exposure through PAM late in pregnancy. Enhanced TLR-mediated IL-10 responses at birth are associated with an increased risk of P. falciparum infection, suggesting a compromised ability to combat infection in early life.

[Tolerance of antiretroviral drugs during pregnancy]

Prevention of transmission from mother to child HIV-1 with antire-trovirals is extraordinarily effective. The risk is now almost zero for a woman properly followed, early in her pregnancy. Rapid expansion of this prophylaxis gives hope of a virtual elimination of pediatric AIDS at a global scale. In 2012, more than 500,000 women around the world have received antiretrovirals during pregnancy making the issue of tolerance crucial. Even if the health of children "exposed-uninfected" is not a concern in the vast majority of cases, a series of biological, clinical and imaging alerts justifies attention. Genotoxic profile of zidovudine, and more generally that of antiretroviral nucleoside analogues for mitochondrial and/or nuclear DNA is certainly the main questions regarding the potential long-term effects to the child.

Age-dependent differences in systemic and cell-autonomous immunity to L. monocytogenes

Host defense against infection can broadly be categorized into systemic immunity and cell-autonomous immunity. Systemic immunity is crucial for all multicellular organisms, increasing in importance with increasing cellular complexity of the host. The systemic immune response to Listeria monocytogenes has been studied extensively in murine models; however, the clinical applicability of these findings to the human newborn remains incompletely understood. Furthermore, the ability to control infection at the level of an individual cell, known as “cell-autonomous immunity,” appears most relevant following infection with L. monocytogenes; as the main target, the monocyte is centrally important to innate as well as adaptive systemic immunity to listeriosis. We thus suggest that the overall increased risk to suffer and die from L. monocytogenes infection in the newborn period is a direct consequence of age-dependent differences in cell-autonomous immunity of the monocyte to L. monocytogenes. We here review what is known about age-dependent differences in systemic innate and adaptive as well as cell-autonomous immunity to infection with Listeria monocytogenes.

Variation between Populations in the Innate Immune Response to Vaccine Adjuvants

The success of the World Health Organization recommended “Expanded Program of Immunization” (EPI) and similar regional or national programs has been astounding. However, infectious threats currently not covered by these programs continue to infect millions of infants around the world. Furthermore, many infants do not receive existing vaccines either on time or for the required number of doses to provide optimal protection. Nor do all infants around the world develop the same protective immune response to the same vaccine. As a result approximately three million infants die every year from vaccine preventable infections. To tackle these issues, new vaccines need to be developed as well as existing ones made easier to administer. This requires identification of age-optimized vaccine schedules and formulations. In order to be most effective this approach will need to take population-based differences in response to vaccines and adjuvants into account. This review summarizes what is currently known about differences between populations around the world in the innate immune response to existing as well as new and promising vaccine adjuvants.

Pathogenesis of hepatitis C during pregnancy and childhood

The worldwide prevalence of HCV infection is between 1% and 8% in pregnant women and between 0.05% and 5% in children. Yet the pathogenesis of hepatitis C during pregnancy and in the neonatal period remains poorly understood. Mother-to-child transmission (MTCT), a leading cause of pediatric HCV infection, takes place at a rate of <10%. Factors that increase the risk of MTCT include high maternal HCV viral load and coinfection with HIV-1 but, intriguingly, not breastfeeding and mode of delivery. Pharmacological prevention of MTCT is not possible at the present time because both pegylated interferon alfa and ribavirin are contraindicated for use in pregnancy and during the neonatal period. However, this may change with the recent introduction of direct acting antiviral agents. This review summarizes what is currently known about HCV infection during pregnancy and childhood. Particular emphasis is placed on how pregnancy-associated immune modulation may influence the progression of HCV disease and impact MTCT, and on the differential evolution of perinatally acquired HCV infection in children. Taken together, these developments provide insights into the pathogenesis of hepatitis C and may inform strategies to prevent the transmission of HCV from mother to child.

Ontogeny of Toll-like receptor mediated cytokine responses of South African infants throughout the first year of life

The first year of life represents a time of marked susceptibility to infections; this is particularly true for regions in sub-Saharan Africa. As innate immunity directs the adaptive immune response, the observed increased risk for infection as well as a suboptimal response to vaccination in early life may be due to less effective innate immune function. In this study, we followed a longitudinal cohort of infants born and raised in South Africa over the first year of life, employing the most comprehensive analysis of innate immune response to stimulation published to date. Our findings reveal rapid changes in innate immune development over the first year of life. This is the first report depicting dramatic differences in innate immune ontogeny between different populations in the world, with important implications for global vaccination strategies.