SARS-CoV-2 Infection in Children Less Than Forty Days Hospitalized in Belgium Between 2020 and 2022.

Our study aimed to assess the severity of severe acute respiratory syndrome coronavirus 2 infection in hospitalized infants under 40 days old, across 21 Belgian hospitals between 2020 and 2022. Of the 365 infants studied, 14.2% needed respiratory support. The median hospital stay was 3 days (interquartile range, 2-4), and there were no deaths. Infection severity was similar during the Omicron and Alpha/Delta periods.

Immunovirological status in people with perinatal and adult-acquired HIV-1 infection: a multi-cohort analysis from France.

Background: No study has compared the virological and immunological status of young people with perinatally-acquired HIV infection (P-HIV) with that of people with HIV adulthood (A-HIV) having a similar duration of infection. Methods: 5 French cohorts of P-HIV and A-HIV patients with a known date of HIV-infection and receiving antiretroviral treatment (ART), were used to compare the following proportions of: virological failure (VF) defined as plasma HIV RNA ≥ 50 copies/mL, CD4 cell percentages and CD4:CD8 ratios, at the time of the most recent visit since 2012. The analysis was stratified on time since infection, and multivariate models were adjusted for demographics and treatment history. Findings: 310 P-HIV were compared to 1515 A-HIV (median current ages 20.9 [IQR:14.4-25.5] and 45.9 [IQR:37.9-53.5] respectively). VF at the time of the most recent evaluation was significantly higher among P-HIV (22.6%, 69/306) than A-HIV (3.3%, 50/1514); p ≤ 0.0001. The risk of VF was particularly high among the youngest children (2-5 years), adolescents (13-17 years) and young adults (18-24 years), compared to A-HIV with a similar duration of infection: adjusted Odds-Ratio (aOR) 7.0 [95% CI: 1.7; 30.0], 11.4 [4.2; 31.2] and 3.3 [1.0; 10.8] respectively. The level of CD4 cell percentages did not differ between P-HIV and A-HIV. P-HIV aged 6-12 and 13-17 were more likely than A-HIV to have a CD4:CD8 ratio ≥ 1: 84.1% vs. 58.8% (aOR = 3.5 [1.5; 8.3]), and 60.9% vs. 54.7% (aOR = 1.9 [0.9; 4.2]) respectively. Interpretation: P-HIV were at a higher risk of VF than A-HIV with a similar duration of infection, even after adjusting for treatment history, whereas they were not at a higher risk of immunological impairment. Exposure to viral replication among young patients living with HIV since birth or a very early age, probably because of lower adherence, could have an impact on health, raising major concerns about the selection of resistance mutations and the risk of HIV transmission. Funding: Inserm - ANRS MIE.

Maternal immunization in women living with HIV.

Thanks to widespread use of antiretroviral therapy worldwide, women living with HIV (WLWH) are becoming pregnant and giving birth to HIV-exposed but uninfected (HEU) newborns. Both pregnancy and HIV infection-related factors such as low CD4+ T-cell count or uncontrolled viral load increase the risk of severe infections such as influenza, COVID-19, and others, making maternal immunization a valuable tool to decrease maternal morbidity among WLWH. Vaccines administered during pregnancy may also benefit the health of HEU infants. Indeed, HEU infants suffer from higher risk of morbidity of infectious origin, including respiratory syncytial virus (RSV), group B streptococcus (GBS), pneumococcus and pertussis infections. Maternal pertussis immunization is recommended in various high-income countries but not in many low-middle income countries where HIV prevalence is higher. GBS and RSV vaccines to be administered during pregnancy are currently in late-phase clinical trials in HIV-uninfected women and could represent a valuable tool to decrease morbidity during infancy. Decreased transfer of vaccine-specific IgG, accelerated waning of vaccine-induced antibody responses, linked to persistent maternal immune activation, and blunting of infant immune response to vaccines could hamper vaccine effectiveness among WLWH and HEU infants. Vaccine hesitancy could limit benefits of maternal immunization and strategies to tackle vaccine hesitancy should be part of HIV routine care. The aim of this review is to summarize the current knowledge regarding the immunogenicity and efficacy of available and upcoming vaccines recommended during pregnancy of WLWH.

Gen Z and HIV-Strategies for Optimizing the Care of the Next Generation of Adolescents Living with HIV.

The management of adolescents living with HIV represents a particular challenge in the global response to HIV. The challenges specific to this age group include difficulties engaging and maintaining them in care, challenges with transition to adult care, and limited therapeutic options for treatment-experienced patients, all of which have been jeopardized by the COVID-19 pandemic. This paper summarizes some of the challenges in managing adolescents living with HIV, as well as some of the most recent and innovative therapeutic approaches in this population.

SARS-CoV-2 vaccination elicits broad and potent antibody effector functions to variants of concern in vulnerable populations.

SARS-CoV-2 variants have continuously emerged in the face of effective vaccines. Reduced neutralization against variants raises questions as to whether other antibody functions are similarly compromised, or if they might compensate for lost neutralization activity. Here, the breadth and potency of antibody recognition and effector function is surveyed following either infection or vaccination. Considering pregnant women as a model cohort with higher risk of severe illness and death, we observe similar binding and functional breadth for healthy and immunologically vulnerable populations, but considerably greater functional antibody breadth and potency across variants associated with vaccination. In contrast, greater antibody functional activity targeting the endemic coronavirus OC43 is noted among convalescent individuals, illustrating a dichotomy in recognition between close and distant human coronavirus strains associated with exposure history. This analysis of antibody functions suggests the differential potential for antibody effector functions to contribute to protecting vaccinated and convalescent subjects as novel variants continue to evolve.

Imported Malaria in Children: A Study Over an 11-Year Period in Brussels.

BACKGROUND: Malaria is a major global public health concern in endemic countries and imported childhood malaria is increasing in malaria non-endemic countries. METHODS: This was a retrospective case review of all laboratory-confirmed malaria cases in children 0-16 years admitted between 2009 and 2019 in 2 large university teaching Hospitals in Brussels. RESULTS: A total of 160 children with a median age of 6.8 years (range 5-191 months) were included. We identified 109 (68%) children living in Belgium who had acquired malaria during their visit to malaria-endemic countries to visiting friends and relatives (VFRs), 49 children (31%) visitors or newly installed migrants, and 2 Belgian tourists. Peak seasonal incidence occurred between August and September. Plasmodium falciparum was responsible for 89% of all malaria cases. Almost 80% of children living in Belgium visited a travel clinic for advice, but only one-third reported having taken the prophylaxis schedule according to the recommendations. Based on WHO criteria, 31 children (19.3%) developed severe malaria; most of the patients with severe malaria were VFR travelers and were significantly younger, had higher leukocytosis, had more thrombocytopenia, higher CRP, and lower natremia compared with patients with an uncomplicated course. All children recovered fully. CONCLUSIONS: Malaria is a significant cause of morbidity among returning travelers and newly arrived immigrants to Belgium. Most of the children had an uncomplicated disease course. Physicians should educate families about traveling to malaria-endemic areas to correct malaria preventive measures and prophylaxis.

Retrospective comparison of respiratory syncytial virus and metapneumovirus clinical presentation in hospitalized children.

Respiratory syncytial virus (RSV) and Human metapneumovirus (hMPV), members of Pneumoviridae family are common causes of acute respiratory tract infections (ARTI) among children. Study material includes routine nasopharyngeal samples obtained during 8-year period for hMPV and one single season for RSV in children hospitalized for ARTI between 0 and 15 years at the Center Hospitalier Universitaire (CHU) Saint Pierre in Brussels. Positive samples for RSV or hMPV identified by viral culture, lateral flow chromatography test for RSV or direct fluorescent assay for hMPV were selected retrospectively. Characteristics of children hospitalized for RSV or hMPV infections were compared. Children hospitalized for RSV infection were significantly younger and requiring more respiratory support, longer hospital stay and transfers in Pediatric intensive Care Units than those hospitalized for hMPV infection. Pneumonia diagnostic and antibiotics therapies were more significantly associated with hMPV infections. In conclusion, despite their genetic similarities, RSV, and hMPV present epidemiological and clinical differences in pediatric infections. Our results should be confirmed prospectively.

Younger Children Develop Higher Effector Antibody Responses to SARS-CoV-2 Infection.

Background: The basis of the less severe clinical presentation of coronavirus disease 2019 (COVID-19) in children as compared with adults remains incompletely understood. Studies have suggested that a more potent boosting of immunity to endemic common cold coronaviruses (HCoVs) may protect children. Methods: To test this hypothesis, we conducted a detailed analysis of antibodies induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children aged 2 months to 14 years. Results: Younger children had higher titers of antibodies to SARS-CoV-2 receptor binding domain (RBD), S1 but not S2 domain, and total spike (S) protein, higher avidity RBD immunoglobulin G, and higher titers of neutralizing and complement-activating antibodies as compared with older children. In contrast, older children had higher titers of antibodies to HCoVs, which correlated with antibodies to the SARS-CoV-2 S2 domain but not with neutralizing or complement-activating antibodies. Conclusions: These results reveal a unique capacity of young children to develop effector antibody responses to SARS-CoV-2 infection independently of their immunity to HCoVs.

SARS-CoV-2 mRNA vaccination elicits broad and potent Fc effector functions to VOCs in vulnerable populations.

SARS-CoV-2 variants have continuously emerged even as highly effective vaccines have been widely deployed. Reduced neutralization observed against variants of concern (VOC) raises the question as to whether other antiviral antibody activities are similarly compromised, or if they might compensate for lost neutralization activity. In this study, the breadth and potency of antibody recognition and effector function was surveyed in both healthy individuals as well as immunologically vulnerable subjects following either natural infection or receipt of an mRNA vaccine. Considering pregnant women as a model cohort with higher risk of severe illness and death, we observed similar binding and functional breadth for healthy and immunologically vulnerable populations. In contrast, considerably greater functional antibody breadth and potency across VOC was associated with vaccination than prior infection. However, greater antibody functional activity targeting the endemic coronavirus OC43 was noted among convalescent individuals, illustrating a dichotomy in recognition between close and distant human coronavirus strains that was associated with exposure history. Probing the full-length spike and receptor binding domain (RBD) revealed that antibody-mediated Fc effector functions were better maintained against full-length spike as compared to RBD. This analysis of antibody functions in healthy and vulnerable populations across a panel of SARS-CoV-2 VOC and extending through endemic alphacoronavirus strains suggests the differential potential for antibody effector functions to contribute to protecting vaccinated and convalescent subjects as the pandemic progresses and novel variants continue to evolve. One Sentence Summary: As compared to natural infection with SARS-CoV-2, vaccination drives superior functional antibody breadth raising hopes for candidate universal CoV vaccines.

Outcomes of etravirine-based antiretroviral treatment in treatment-experienced children and adolescents living with HIV in Europe and Thailand.

BACKGROUND: Etravirine (ETR) is approved as a component of second or third-line antiretroviral treatment (ART) for children living with HIV. We assessed the outcomes of ETR-based ART in children in routine care in Europe and Thailand. METHODS: Data on children aged <18 years at ETR start were pooled from 17 observational cohorts. Characteristics at ETR start, immunological and virological outcomes at 12 months, discontinuations, adverse events (AEs) and serious adverse events (SAEs) were described. Follow-up was censored at ETR discontinuation, death or last visit. RESULTS: 177 children ever received ETR. At ETR start, median [IQR] age was 15 [12,16] years, CD4 count 480 [287, 713] cells/mm3, 70% had exposure to ≥3 ART classes and 20% had viral load (VL) <50 copies/mL. 95% received ETR in combination with ≥1 potent drug class, mostly protease inhibitor-based regimens. Median time on ETR was 24 [7, 48] months. Amongst those on ETR at 12 months (n=141), 69% had VL<50 copies/mL. Median CD4 increase since ETR start (n=83) was 147 [16, 267] cells/mm3. Overall, 81 (46%) discontinued ETR by last follow-up. Median time to discontinuation was 23 [8, 47] months. Common reasons for discontinuation were treatment simplification (19%), treatment failure (16%) and toxicity (12%). Eight children (5%) had AEs causally associated with ETR, all dermatological/hypersensitivity reactions. Two were SAEs, both Stevens-Johnson Syndrome in children on regimens containing ETR and darunavir and were causally related to either drugs; both resolved following ART discontinuation. CONCLUSION: Children receiving ETR were predominantly highly treatment-experienced, over two-thirds were virally suppressed at 12 months.

Growth and CD4 patterns of adolescents living with perinatally acquired HIV worldwide, a CIPHER cohort collaboration analysis.

INTRODUCTION: Adolescents living with HIV are subject to multiple co-morbidities, including growth retardation and immunodeficiency. We describe growth and CD4 evolution during adolescence using data from the Collaborative Initiative for Paediatric HIV Education and Research (CIPHER) global project. METHODS: Data were collected between 1994 and 2015 from 11 CIPHER networks worldwide. Adolescents with perinatally acquired HIV infection (APH) who initiated antiretroviral therapy (ART) before age 10 years, with at least one height or CD4 count measurement while aged 10-17 years, were included. Growth was measured using height-for-age Z-scores (HAZ, stunting if <-2 SD, WHO growth charts). Linear mixed-effects models were used to study the evolution of each outcome between ages 10 and 17. For growth, sex-specific models with fractional polynomials were used to model non-linear relationships for age at ART initiation, HAZ at age 10 and time, defined as current age from 10 to 17 years of age. RESULTS: A total of 20,939 and 19,557 APH were included for the growth and CD4 analyses, respectively. Half were females, two-thirds lived in East and Southern Africa, and median age at ART initiation ranged from <3 years in North America and Europe to >7 years in sub-Saharan African regions. At age 10, stunting ranged from 6% in North America and Europe to 39% in the Asia-Pacific; 19% overall had CD4 counts <500 cells/mm3 . Across adolescence, higher HAZ was observed in females and among those in high-income countries. APH with stunting at age 10 and those with late ART initiation (after age 5) had the largest HAZ gains during adolescence, but these gains were insufficient to catch-up with non-stunted, early ART-treated adolescents. From age 10 to 16 years, mean CD4 counts declined from 768 to 607 cells/mm3 . This decline was observed across all regions, in males and females. CONCLUSIONS: Growth patterns during adolescence differed substantially by sex and region, while CD4 patterns were similar, with an observed CD4 decline that needs further investigation. Early diagnosis and timely initiation of treatment in early childhood to prevent growth retardation and immunodeficiency are critical to improving APH growth and CD4 outcomes by the time they reach adulthood.

Boosting of cross-reactive antibodies to endemic coronaviruses by SARS-CoV-2 infection but not vaccination with stabilized spike.

Preexisting antibodies to endemic coronaviruses (CoV) that cross-react with SARS-CoV-2 have the potential to influence the antibody response to COVID-19 vaccination and infection for better or worse. In this observational study of mucosal and systemic humoral immunity in acutely infected, convalescent, and vaccinated subjects, we tested for cross-reactivity against endemic CoV spike (S) protein at subdomain resolution. Elevated responses, particularly to the ß-CoV OC43, were observed in all natural infection cohorts tested and were correlated with the response to SARS-CoV-2. The kinetics of this response and isotypes involved suggest that infection boosts preexisting antibody lineages raised against prior endemic CoV exposure that cross-react. While further research is needed to discern whether this recalled response is desirable or detrimental, the boosted antibodies principally targeted the better-conserved S2 subdomain of the viral spike and were not associated with neutralization activity. In contrast, vaccination with a stabilized spike mRNA vaccine did not robustly boost cross-reactive antibodies, suggesting differing antigenicity and immunogenicity. In sum, this study provides evidence that antibodies targeting endemic CoV are robustly boosted in response to SARS-CoV-2 infection but not to vaccination with stabilized S, and that depending on conformation or other factors, the S2 subdomain of the spike protein triggers a rapidly recalled, IgG-dominated response that lacks neutralization activity.

Standardized Definitions of In Utero Human Immunodeficiency Virus and Antiretroviral Drug Exposure Among Children.

In countries with high human immunodeficiency virus (HIV) prevalence, up to 30% of pregnant women are living with HIV, with fetal exposure to both HIV and antiretroviral therapy during pregnancy. In addition, pregnant women without HIV but at high risk of HIV acquisition are increasingly receiving HIV preexposure antiretroviral prophylaxis (PrEP). Investments are being made to establish and follow cohorts of children to evaluate the long-term effects of in utero HIV and antiretroviral exposure. Agreement on a key set of definitions for relevant exposures and outcomes is important both for interpreting individual study results and for comparisons across cohorts. Harmonized definitions of in utero HIV and antiretroviral drug (maternal treatment or PrEP) exposure will also facilitate improved classification of these exposures in future observational studies and clinical trials. The proposed definitions offer a uniform approach to facilitate the consistent description and estimation of effects of HIV and antiretroviral exposures on key child health outcomes.

Children living with HIV in Europe: do migrants have worse treatment outcomes?

OBJECTIVES: To assess the effect of migrant status on treatment outcomes among children living with HIV in Europe. METHODS: Children aged < 18 years at the start of antiretroviral therapy (ART) in European paediatric HIV observational cohorts where ≥ 5% of children were migrants (defined as born abroad) were included. Three outcomes were considered: (i) severe immunosuppression-for-age; (ii) viraemic viral load (≥ 400 copies/mL) at 1 year after ART initiation; and (iii) AIDS/death after ART initiation. The effect of migrant status was assessed using univariable and multivariable logistic and Cox models. RESULTS: Of 2620 children included across 12 European countries, 56% were migrants. At ART initiation, migrant children were older than domestic-born children (median 6.1 vs. 0.9 years, p < 0.001), with slightly higher proportions being severely immunocompromised (35% vs. 33%) and with active tuberculosis (2% vs. 1%), but a lower proportion with an AIDS diagnosis (14% vs. 19%) (all p < 0.001). At 1 year after beginning ART, a lower proportion of migrant children were viraemic (18% vs. 24%) but there was no difference in multivariable analysis (p = 0.702), and no difference in severe immunosuppression (p = 0.409). However, there was a trend towards higher risk of AIDS/death in migrant children (adjusted hazard ratio = 1.51, 95% confidence interval: 0.96-2.38, p = 0.072). CONCLUSIONS: After adjusting for characteristics at ART initiation, migrant children have virological and immunological outcomes at 1 year of ART that are comparable to those who are domestic-born, possibly indicating equity in access to healthcare in Europe. However, there was some evidence of a difference in AIDS-free survival, which warrants further monitoring.

Boosting of Cross-Reactive Antibodies to Endemic Coronaviruses by SARS-CoV-2 Infection but not Vaccination with Stabilized Spike.

Pre-existing antibodies to endemic coronaviruses (CoV) that cross-react with SARS-CoV-2 have the potential to influence the antibody response to COVID-19 vaccination and infection for better or worse. In this observational study of mucosal and systemic humoral immunity in acutely infected, convalescent, and vaccinated subjects, we tested for cross reactivity against endemic CoV spike (S) protein at subdomain resolution. Elevated responses, particularly to the ß-CoV OC43, were observed in all natural infection cohorts tested and were correlated with the response to SARS-CoV-2. The kinetics of this response and isotypes involved suggest that infection boosts preexisting antibody lineages raised against prior endemic CoV exposure that cross react. While further research is needed to discern whether this recalled response is desirable or detrimental, the boosted antibodies principally targeted the better conserved S2 subdomain of the viral spike and were not associated with neutralization activity. In contrast, vaccination with a stabilized spike mRNA vaccine did not robustly boost cross-reactive antibodies, suggesting differing antigenicity and immunogenicity. In sum, this study provides evidence that antibodies targeting endemic CoV are robustly boosted in response to SARS-CoV-2 infection but not to vaccination with stabilized S, and that depending on conformation or other factors, the S2 subdomain of the spike protein triggers a rapidly recalled, IgG-dominated response that lacks neutralization activity.

Aetiology of acute respiratory infection in preschool children requiring hospitalisation in Europe-results from the PED-MERMAIDS multicentre case-control study.

BACKGROUND: Both pathogenic bacteria and viruses are frequently detected in the nasopharynx (NP) of children in the absence of acute respiratory infection (ARI) symptoms. The aim of this study was to estimate the aetiological fractions for ARI hospitalisation in children for respiratory syncytial virus (RSV) and influenza virus and to determine whether detection of specific respiratory pathogens on NP samples was associated with ARI hospitalisation. METHODS: 349 children up to 5 years of age hospitalised for ARI (following a symptom-based case definition) and 306 hospital controls were prospectively enrolled in 16 centres across seven European Union countries between 2016 and 2019. Admission day NP swabs were analysed by multiplex PCR for 25 targets. RESULTS: RSV was the leading single cause of ARI hospitalisations, with an overall population attributable fraction (PAF) of 33.4% and high seasonality as well as preponderance in younger children. Detection of RSV on NP swabs was strongly associated with ARI hospitalisation (OR adjusted for age and season: 20.6, 95% CI: 9.4 to 45.3). Detection of three other viral pathogens showed strong associations with ARI hospitalisation: influenza viruses had an adjusted OR of 6.1 (95% CI: 2.5 to 14.9), parainfluenza viruses (PIVs) an adjusted OR of 4.6 (95% CI: 1.8 to 11.3) and metapneumoviruses an adjusted OR of 4.5 (95% CI: 1.3 to 16.1). Influenza viruses had a PAF of 7.9%, PIVs of 6.5% and metapneumoviruses of 3.0%. In contrast, most other pathogens were found in similar proportions in cases and controls, including Streptococcus pneumoniae, which was weakly associated with case status, and endemic coronaviruses. CONCLUSION: RSV is the predominant cause of ARI hospitalisations in young children in Europe and its detection, as well as detection of influenza virus, PIV or metapneumovirus, on NP swabs can establish aetiology with high probability. PAFs for RSV and influenza virus are highly seasonal and age dependent.

Neurological development of children who are HIV-exposed and uninfected.

Widespread use of antiretroviral drugs for pregnant/breastfeeding females with human immunodeficiency virus (HIV) has led to declining vertical transmission. Despite being HIV-uninfected, the increasing number of children who are HIV-exposed and uninfected (CHEU) often present with developmental alterations. We review seminal and recent evidence on the neurological development of CHEU and associations with early life HIV/antiretroviral exposure. Our conceptual model highlights the numerous exposures and universal risk factors for CHEU developmental disorders. Early studies suggest a significant association between HIV exposure and neurological abnormalities, varying according to the burden of HIV-specific exposures and other risk factors. More recent observations from the modern era are inconsistent, although some studies suggest specific antiretrovirals may adversely affect neurological development of CHEU. As the CHEU population continues to grow, alongside simultaneous increases in types and combinations of antiretrovirals used in pregnancy, long-term monitoring of CHEU is necessary for understanding the effects of HIV/antiretroviral exposure on CHEU developmental outcomes. What this paper adds Evidence on the neurological development of children who are human immunodeficiency virus (HIV)-exposed and uninfected (CHEU) is synthesized. Comparisons are made to children who are HIV-unexposed, across treatment eras and settings, and by antiretroviral drug regimens and drug classes. CHEU exposures are complex and include HIV-specific and universal risk factors which may affect development during the early years of life.

Biogeography of the Relationship between the Child Gut Microbiome and Innate Immune System.

The gut microbiome is a well-recognized modulator of host immunity, and its compositions differ between geographically separated human populations. Systemic innate immune responses to microbial derivatives also differ between geographically distinct human populations. However, the potential role of the microbiome in mediating geographically varied immune responses is unexplored. We here applied 16S amplicon sequencing to profile the stool microbiome and, in parallel, measured whole-blood innate immune cytokine responses to several pattern recognition receptor (PRR) agonists among 2-year-old children across biogeographically diverse settings. Microbiomes differed mainly between high- and low-resource environments and were not strongly associated with other demographic factors. We found strong correlations between responses to Toll-like receptor 2 (TLR2) and relative abundances of Bacteroides and Prevotella populations, shared among Canadian and Ecuadorean children. Additional correlations between responses to TLR2 and bacterial populations were specific to individual geographic cohorts. As a proof of concept, we gavaged germfree mice with human donor stools and found murine splenocyte responses to TLR stimulation were consistent with responses of the corresponding human donor populations. This study identified differences in immune responses correlating to gut microbiomes across biogeographically diverse settings and evaluated biological plausibility using a mouse model. This insight paves the way to guide optimization of population-specific interventions aimed to improve child health outcomes.IMPORTANCE Both the gut microbiome and innate immunity are known to differ across biogeographically diverse human populations. The gut microbiome has been shown to directly influence systemic immunity in animal models. With this, modulation of the gut microbiome represents an attractive avenue to improve child health outcomes associated with altered immunity using population-specific approaches. However, there are very scarce data available to determine which members of the gut microbiome are associated with specific immune responses and how these differ around the world, creating a substantial barrier to rationally designing such interventions. This study addressed this knowledge gap by identifying relationships between distinct bacterial taxa and cytokine responses to specific microbial agonists across highly diverse settings. Furthermore, we provide evidence that immunomodulatory effects of region-specific stool microbiomes can be partially recapitulated in germfree mice. This is an important contribution toward improving global child health by targeting the gut microbiome.

Innate Immune Responses and Gut Microbiomes Distinguish HIV-Exposed from HIV-Unexposed Children in a Population-Specific Manner.

In both high- and low-income countries, HIV-negative children born to HIV-positive mothers (HIV exposed, uninfected [HEU]) are more susceptible to severe infection than HIV-unexposed, uninfected (HUU) children, with altered innate immunity hypothesized to be a cause. Both the gut microbiome and systemic innate immunity differ across biogeographically distinct settings, and the two are known to influence each other. And although the gut microbiome is influenced by HIV infection and may contribute to altered immunity, the biogeography of immune-microbiome correlations among HEU children have not been investigated. To address this, we compared the innate response and the stool microbiome of 2-y-old HEU and HUU children from Belgium, Canada, and South Africa to test the hypothesis that region-specific immune alterations directly correlate to differences in their stool microbiomes. We did not detect a universal immune or microbiome signature underlying differences between HEU versus HUU that was applicable to all children. But as hypothesized, population-specific differences in stool microbiomes were readily detected and included reduced abundances of short-chain fatty acid-producing bacteria in Canadian HEU children. Furthermore, we did not identify innate immune-microbiome associations that distinguished HEU from HUU children in any population. These findings suggest that maternal HIV infection is independently associated with differences in both innate immunity and the stool microbiome in a biogeographical population-specific way.