Summer in France with Baby by Dakota Corbin
We are most defenseless when we are born. Up until fifteen weeks after birth a baby is incapable of producing its own immunological defenses and must depend on an alternative. It is known that the mother provides her own antibodies for the child to use to detect foreign invaders. Antibodies are like biological tags with which our white blood cells can identify and eliminate foreign agents and their parts. Antibodies are typically composed of two antigen binding segments (Fab), and one receptor interacting segment (Fc). An antigen is a foreign molecule which the immune system can recognize. When the mother provides these pre-made antibodies it is known as passive immunity because the baby has not produced the antibodies themselves and will have the immunity only temporarily. Due to the nature of passive immunity it assumes the mother will have appropriate defenses and that the child will be able to make use of them until they can form their own.
Pou et. Al. conduct their study of preterm and term birthed babies to compare the differences that may arise in the way and time they receive the passive immunity. They conduct experiments using around 200 viruses to compare their infant antibody samples. Viruses have a number of different external markers and receptors which antibodies can bind to. Some of these are specific to the virus and can therefore be used to identify the foreign attack. These areas which can be bound by antibodies for detection are known as epitopes and the research group use a combination of all the available epitopes to screen for the antibodies in the infants. Around 94,000 epitopes on the aforementioned viruses are used to get a good idea of the nature of the antibodies being passed on.
Comparisons are made using the plasma samples from blood at three different stages in the infants post birth. Some blood is taken from the cord at birth, at week 1, week 4, and week 12 to test as well as some samples from the mother. This creates a longitudinal study which refers to the fact that the same infants were tested over a period of time to verify results and observe changes. Samples of antibodies from the infants are introduced to the viral epitopes on magnetic beads and thus separated from unused antibodies via VirScan. In this way they can describe whether or not an infant would be able to respond to an antigen or foreign invader and thus be called seropositive. The samples are then given a VirScore which represents the ability to bind to foreign antigen epitopes.
The research data finds that generally an infant’s repertoire of immunity closely matches that of the mother with the exception of what seem to be infant specific diseases such as the respiratory syncytial virus. Additionally less dynamic viruses seem to carry more prominent and recognized epitopes compared to influenza which can vary drastically given mutations and other changes. Due to more rapid changes in influenza the immunodominant epitopes may not remain as helpful tags for long. Other viruses such as rhinovirus and herpesvirus however seem to have more immunodominant epitopes exploited by the infants. The most interesting information from the article seems to be that despite being born at between 24 to 40 weeks of gestation, the infants ended up with a healthy concentration of antibodies. This contradicts the idea that preterm babies are born with ineffective to low efficacy immunity. They only seem to vary in antibody concentrations immediately after birth however and reach comparable concentrations by week 12.
Preterm babies have shorter life spans on their passive immunity only because of this lower concentration passed on at birth. Pou et. Al. find however that their immunity reaches comparable concentrations by week 12 and that they do not generally vary much from the maternal repertoire of antibodies. As expected the less dynamic and changing viruses have more immunodominant epitope antibodies which can be hypothetically be explained. Some variance of the infant’s immunity can be explained in the differences of gestation but a majority still remains to be explained. As it turns out passive immunity bestowed upon us is largely dependent on mothers but not much threat is posed in terms of immunity should a child be born before the 37 week mark. Just another reason to thank your mother for everything she has given you.
In Depth
The article has very insightful diagrams and conclusions which form a cohesive statement and step forward in understanding. In particular the color coding and organization of all the gestational ages and viruses serve the reader well. Some graphs do however have logarithmic axes which are not intuitive as they are reversed with the farther end being the lowest concentration. Other than that the data presented is concise and desvriptive with good follow-up material data graphs at the end. They make solid conclusions from the evidence and ask appropriate follow-up information on the low amount of variance which can be explained by gestational age. Is it possible that some of the variance specifically for viruses such as the RS virus can be explained by the relevance of virus to infants versus adults? Additionally it would be a good idea to flesh out the normalization method of the serum IgG versus the genome of bacteriophage process in VirScan as this is a crux of the study. Overall the information is solid and they conclude that in fact the gestational age does not compromise the immunity of the child. This knowledge has implications for the way one might handle applying additional passive immunity to a child as it may not be needed or simply needed a bit earlier. Preterm babies will also not necessarily be at risk by the mere fact as they just take time to fully assemble their immunological defenses; more observation time may be necessary but no alarm bells should go off.
Pou, C., Nkulikiyimfura, D., Henckel, E., Olin, A., Lakshmikanth, T., Mikes, J., Wang, J., Chen, Y., Bernhardsson, A., Gustafsson, A., Bohlin, K. and Brodin, P. (2019). The repertoire of maternal anti-viral antibodies in human newborns. [online] Nature. https://www.nature.com/articles/s41591-019-0392-8.
Dakota Corbin. https://unsplash.com/@thedakotacorbin
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The Lead 
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