of the children developed antibodies despite negative PCR tests

A case study, published in Nature, examines a family whose children, exposed to the coronavirus, developed antibodies without the pathogen having replicated in their cells. A new brick added to the rare studies on the immune reaction of children to this disease.

” Compared to adults, children with [SARS-CoV-2] have mostly mild or asymptomatic infections, but the underlying immunological differences remain unclear “, Introduces a study published on November 11 in Nature. This research work examines a surprising case: an Australian family whose parents are coronavirus positive, PCR confirmed, and symptomatic, but whose children have tested negative multiple times … despite having developed, like their parents, a ‘ elevated immune response. Any way to better understand why children are less likely to develop this disease?

The parents of the family – Leila Sawenko and Tony Maguire – were likely infected with the disease during a wedding in Sydney, during which the children were not present. As soon as they returned to Melbourne with their three children, Leila and Tony felt the first symptoms related to the coronavirus. All family members were then quickly recruited as part of a study conducted by the Murdoch Children’s Research Institute (MCRI). Samples were taken every 2-3 days from the whole family (nasopharyngeal swabs, as well as serological swabs, but also from throat, feces and urine).

The results of this study show that the children of this Australian family appear to have developed an immediate immune response that prevented the disease from developing on its own, making the onset of infection invisible as well. ” The youngest child, who has not shown any symptoms, has the strongest antibody response », Comments immunologist Melanie Neeland on the institute’s website. Along with this immune response, the levels of cytokines – which respond to inflammation – are extremely low. This means that the inflammation has just occurred.

An effective and immediate immune response

For the researchers, these children exposed to the coronavirus then immediately developed antibodies, thus not preventing the infection itself, but preventing the pathogen from replicating and this onset of the infection leading to inflammation. The immune response was in fact so rapid and effective as to prevent disease (infection must be distinguished from disease), reducing the viral load to such a low level that it could not be detected by a test. PCR, which is the most sensitive technique anyway, and also when repeated for several days.

It is obvious that it is possible to be infected with the coronavirus without showing symptoms, this asymptomatic functioning is also quite common for Covid-19 disease. But, in children, the immune response remains poorly studied, and this practical case shows that it may nevertheless have some specificities – such as causing a greater number of asymptomatic and less severe cases than adults, as well as a stronger one. invisibility of infection to PCR tests. Because usually, in adults, such a high level of antibodies as in the children involved in this study means that even in the absence of symptoms, PCR tests should have detected the infection.

The authors of the study cannot yet fully explain this mechanism in detail, but the discovery is already important as such for advancing scientific research on the immune system of children in the face of this disease and why severe forms do not develop: ” These data indicate that children can develop an immune response to SARS-Cov-2 without virological confirmation of the infection, increasing the chance that children’s immunity can prevent the onset of SARS-CoV infection. -2. “

What implication?

This is a single study, which develops conclusions on the practical case of a family. The discovery, however, surprises the authors. The mother of the affected family also confided to ABC that she noticed how the researchers themselves were amazed by what they found. Be that as it may, the authors believe above all that this invites the development of this line of research by involving more families in larger studies.

Deepening the immune response in children is crucial, since in addition to advancing the virological understanding of the coronavirus, it can have an epidemiological impact on screening strategies and measures to curb the spread of the disease, up to, for example, openness. of schools during a block. ” The discrepancy between virological PCR and clinical serological test results, despite a marked immune response, highlights the limits of sensitivity of nasopharyngeal PCR screening and current diagnostic serology in children. Our findings underscore the need for a more detailed study of the immune response to SARS-CoV-2 to better understand exposure and protective immunity in children. “, Point out the researchers of the Murdoch Children’s Research Institute.

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