Iron homeostasis in full-term, normal birthweight Gambian neonates over the first week of life

Human neonates elicit a profound hypoferremia which may protect against bacterial sepsis. We examined the transience of this hypoferremia by measuring iron and its chaperone proteins, inflammatory and haematological parameters over the first post-partum week. We prospectively studied term, normal weight Gambian newborns. Umbilical cord vein and artery, and serial venous blood samples up to day 7 were collected. Hepcidin, serum iron, transferrin, transferrin saturation, haptoglobin, c-reactive protein, α1-acid-glycoprotein, soluble transferrin receptor, ferritin, unbound iron-binding capacity and full blood count were assayed. In 278 neonates we confirmed the profound early postnatal decrease in serum iron (22.7 ± 7.0 µmol/L at birth to 7.3 ± 4.6 µmol/L during the first 6-24 h after birth) and transferrin saturation (50.2 ± 16.7% to 14.4 ± 6.1%). Both variables increased steadily to reach 16.5 ± 3.9 µmol/L and 36.6 ± 9.2% at day 7. Hepcidin increased rapidly during the first 24 h of life (19.4 ± 14.4 ng/ml to 38.9 ± 23.9 ng/ml) and then dipped (32.7 ± 18.4 ng/ml) before rising again at one week after birth (45.2 ± 19.1 ng/ml). Inflammatory markers increased during the first week of life. The acute postnatal hypoferremia in human neonates on the first day of life is highly reproducible but transient. The rise in serum iron during the first week of life occurs despite very high hepcidin levels indicating partial hepcidin resistance.Trial Registration: clinicaltrials.gov (NCT03353051). Registration date: November 27, 2017.

Superinfection with SARS-CoV-2 Has Deleterious Effects on Mycobacterium bovis BCG Immunity and Promotes Dissemination of Mycobacterium tuberculosis

An estimated one-third of the world's population is infected with Mycobacterium tuberculosis, with the majority being vaccinated with Mycobacterium bovis BCG. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains a threat, and we must understand how SARS-CoV-2 can modulate both BCG immunity and tuberculosis pathogenesis. Interestingly, neither BCG vaccination nor tuberculosis infection resulted in differences in clinical outcomes associated with SARS-CoV-2 in transgenic mice. Surprisingly, earlier M. tuberculosis infection resulted in lower SARS-CoV-2 viral loads, mediated by the heightened immune microenvironment of the murine lungs, unlike vaccination with BCG, which had no impact. In contrast, M. tuberculosis-infected tissues had increased bacterial loads and decreased histiocytic inflammation in the lungs following SARS-CoV-2 superinfection. SARS-CoV-2 modulated BCG-induced type 17 responses while decreasing type 1 and increasing type 2 cytokines in M. tuberculosis-infected mice. These findings challenge initial findings of BCG's positive impact on SARS-CoV-2 infection and suggest potential ramifications for M. tuberculosis reactivation upon SARS-CoV-2 superinfection. IMPORTANCE Prior to SARS-CoV-2, M. tuberculosis was the leading infectious disease killer, with an estimated one-third of the world's population infected and 1.7 million deaths a year. Here, we show that SARS-CoV-2 superinfection caused increased bacterial dissemination in M. tuberculosis-infected mice along with immune and pathological changes. SARS-CoV-2 also impacted the immunity of BCG-vaccinated mice, resulting in decreased interleukin-17 (IL-17) levels, while offering no protective effect against SARS-CoV-2. These results demonstrate that SARS-CoV-2 may have a deleterious effect on the ongoing M. tuberculosis pandemic and potentially limit BCG's efficacy.

Iron Homeostasis over the First Week of Life: A Prospective Cohort Study in Hospital-Delivered Gambian Neonates

Objectives

Full-term newborns elicit an immediate postnatal hypoferremia at birth. We examined whether preterm and low birthweight babies are capable of a similar response. The transience of this innate defence in full-term babies was assessed by measuring iron, inflammatory and haematological parameters over the first postpartum week.

Methods

We conducted an observational study of 152 babies who were either preterm (>32 to <37weeks gestational age) and/or low birthweight (<2500 g) (PTB/LBW) and 278 term, normal-weight babies (FTB/NBW). Blood was sampled from the umbilical cord and matched venous blood samples were taken from all neonates between 6–24 hours after delivery. Term, normal-weight babies were then randomised to a second blood draw at 25–80 h (V2), 81–136 h (V3) or 137–192 h (V4). We measured haematological, iron and inflammatory markers in all samples.

Results

PTB/LBW and FTB/NBW babies decreased serum iron 3-fold within 12 h of postpartum life compared to cord blood (7.5 ± 4.5 vs 23.3 ± 7.1 ng/ml, P < 0.001, n = 425). Transferrin saturation showed a similar decline. C-reactive protein levels increased over 10-fold (P < 0.001) and hepcidin levels doubled (P < 0.001). No difference was observed in these responses between study groups. FTB/NBW newborns then steadily increased serum iron (16.5 ± 3.9 µmol/L) and TSAT (36.7 ± 9.2%) by V4 (P for trend <0.0001 for each). Hepcidin (45.2 ± 19.1 ng/ml) increased during this period (P for trend <0.0001), showing only a weak influence on serum iron and TSAT. Inflammatory markers increased from V1 to V4.

Conclusions

Premature and low birthweight babies mount a rapid postnatal hypoferremia equal to that in term babies. Data suggest that this hepcidin-mediated response is triggered by acute inflammation at birth. This evolved method of protection against septicaemia is transient, with a later increase in serum iron despite very high hepcidin. This indicates hepcidin resistance possibly caused by macrophage iron saturation. Pharmacological prolongation of hypoferremia might offer an ancillary tool in the arsenal against infection, however, it would need to overcome the hepcidin resistance we now report.

Funding Sources

Bill & Melinda Gates Foundation.

Early postnatal hypoferremia in low birthweight and preterm babies: A prospective cohort study in hospital-delivered Gambian neonates

BACKGROUND

Neonates, particularly those born preterm (PTB) and with low birthweight (LBW), are especially susceptible to bacterial and fungal infections that cause an estimated 225,000 deaths annually. Iron is a vital nutrient for the most common organisms causing septicaemia. Full-term babies elicit an immediate postnatal hypoferremia assumed to have evolved as an innate defence. We tested whether PTB and LBW babies are capable of the same response.

METHODS

We conducted an observational study of 152 babies who were either PTB (born ≥32 to <37 weeks gestational age) and/or LBW (<2500 g) (PTB/LBW) and 278 term, normal-weight babies (FTB/NBW). Blood was sampled from the umbilical cord vein and artery, and matched venous blood samples were taken from all neonates between 6-24 h after delivery. We measured haematological, iron and inflammatory markers.

FINDINGS

In both PTB/LBW and FTB/NBW babies, serum iron decreased 3-fold within 12 h of delivery compared to umbilical blood (7·5 ± 4·5 vs 23·3 ± 7·1 ng/ml, P < 0·001, n = 425). Transferrin saturation showed a similar decline with a consequent increase in unsaturated iron-binding capacity. C-reactive protein levels increased over 10-fold (P < 0·001) and hepcidin levels doubled (P < 0·001). There was no difference in any of these responses between PTB/LBW and FTB/NBW babies.

INTERPRETATION

Premature or low birthweight babies are able to mount a very rapid hypoferremia that is indistinguishable from that in normal term babies. The data suggest that this is a hepcidin-mediated response triggered by acute inflammation at birth, and likely to have evolved as an innate immune response against bacterial and fungal septicaemia.

TRIAL REGISTRATION

clinicaltrials.gov (NCT03353051). Registration date: November 27, 2017.

FUNDING

Bill & Melinda Gates Foundation (OPP1152353).