Immune-metabolic trajectories delineate subgroups in paediatric long COVID, 2026, Vilser et al.

[SNT Gatchaman]

Immune-metabolic trajectories delineate subgroups in paediatric long COVID

Spoiler: Authors

Vilser, Daniel; Han, Irina; Vogel, Katrin; Jakobs, Pauline; Lorenz, Michael; Huppke, Peter; Newman, Lars; Paszkier, Michelle; Kuhle, Jens; Mohr, Juliane; Aign, Clara; Reinhold, Annegret; Reinhold, Dirk; Weinzierl, Stefan; Ullmann, Elisabeth; Proquitté, Hans; Brunner-Weinzierl, Monika C

Most children and adolescents recover rapidly from SARS-CoV-2 infection, yet a subset develops paediatric long COVID (LC). How immune ontogeny shapes LC biology and heterogeneity remains unclear.

We deeply phenotype a two-visit cohort with severe LC (n = 74) and controls (n = 27) spanning up to 3.2 years post index infection. Symptom burden remains high and neurofilament light chain (NfL) percentiles inversely associate with functional status (Bell score;  = −0.3536, P = 0.0060). Cardiopulmonary assessment and serology are unremarkable.

Conventional autoantibodies are not enriched, whereas anti-DFS70 supports subgrouping. Immune features are temporally structured; SARS-CoV-2–associated mediators decline within 1 year, while innate-weighted, Th2-skewed cytokines persist. Metabolomics (43 metabolites) recapitulate the identified subgroups and align with EBV serostatus, disease phase (<1 year versus years 1–3.2), and anti-DFS70 positivity. In EBV-naive LC, higher haemoglobin concentration (MCHC) tracks worse function, whereas higher IL-12p40, thiamine and basophils track milder impairment (all P ≤ 0.0170).

These data delineate immune-metabolic and haematological axes of paediatric LC heterogeneity and support biomarker-guided stratification.

Web | DOI | PDF | Nature Communications | Open Access

 

[Murph]

Some fascinating patterns showing cytokines surging then returning to levels comparable with controls, even as symptoms continue.
A phenotype presentation that changes over time is confirmed by:

• earlier findings in mecfs (Klimas?),
• anecdotes in these pages, and
• my own experience: I had non-stop sore throats for a while and then none for many years

 

[SNT Gatchaman]

We analysed 74 children with active LC symptoms and 27 controls, defining the index date as the last documented SARS-CoV2 infection preceding LC onset; time since index infection at study visit (TsinceIndex) ranged up to 166 weeks (~3.2 years). Controls comprised healthy children (n = 14) and clinically stable children with cystic fibrosis (CF; n = 13), included as a respiratory infection-exposed comparator group.

Patients assessed within 1 year of active LC showed no group-level improvement in physical or mental health measures. Across the broader post-infection window (up to 3 years), we similarly observed no consistent improvement at the cohort level, although individual trajectories varied, with some patients showing modest improvement or decline.

Collectively, these data define a first-year LC signature characterised by immunological dysregulation with distinct cytokine patterns.

findings outline an early antiviral and Th2-skewed response within the first year shifts towards a waning SARS-CoV-2 response showing innate- and Th2/17-oriented responses. This is consistent with the progressive immunopathological remodelling associated with chronicity.

covariates were defined a priori to represent complementary biological axes rather than being selected by univariable screening: a marker of prior EBV exposure (anti-EBV EBNA; exposure history, not reactivation), mean corpuscular haemoglobin concentration (MCHC), as a haematological readout, IL-12p40 as a robust proxy of IL-12/IL-23–axis activity, and basophil granulocyte counts as an indicator of granulocyte lineage shifts.

The fixed effects explained 21% of Bell score variance (R ² m = 0.2121), and each covariate was significantly associated with the Bell score. Notably, anti-EBV EBNA and MCHC decreased with clinical improvement, whereas basophil counts and IL-12p40 increased.

In separate analyses, to probe a potential autoimmune contribution to autonomic involvement, aAbs against GPCR (GPCR-aAb) targeting β 1/ β 2-adrenergic and M3/M4-muscarinic receptors were quantified by ELISA. […] Moreover, aAb levels did not differ between LC TsinceIndex windows (<1 year vs 1–3 years). Next, we analysed additional aAbs as surrogate markers of vasculitis […]. None of these markers […] were elevated relative to controls, and all remained below the assay cut-off during the first year of paediatric LC).

 

[SNT Gatchaman]

Multiple testing was controlled within each family (Holm–Bonferroni), and the composite summary highlights only readouts with significant overall model fit and a significant positive contribution of EBV exposure.

Using this framework, EBV exposure was associated with a pronounced inflammatory signature in paediatric LC. EBV-experienced patients showed an innate-inflammatory cytokine profile with elevated IL-1α and IL-15, accompanied by higher IFNα and IL-18.

This composite highlights a predominantly innate-inflammatory and IL-12p40/IL-22 skewed cytokine landscape in EBV-experienced paediatric LC patients, accompanied by increased neutrophils and regulatory cytokines.

We identified three features by which LC subgroups can be categorised: The first relates to TsinceIndex, where LC in the first year is characterised by Th2-, innate and viral-associated cytokines, and LC persisting for 1–3.2 years is characterised by Th2-biased, Th17-related and innate-like systemic cytokines. A second relates to anti-DFS70positivity, which was associated with markedly fewer coagulation abnormalities. The third involves EBV serostatus, which was linked to a pro-inflammatory cytokine profile and granulocytic dysregulation.

Leveraging the anti-EBV EBNA–negative/low status observed in ~50% of our paediatric LC cohort, we applied LMMs used for disease severity in Fig. 2k (Bell score as dependent variable) to this subgroup, omitting EBV status as a covariate and retaining IL-12p40, MCHC, basophil counts and vitamin B1 (thiamine) as predictors. The model was highly significant (P < 0.0001) and showed an improved R ² m of 0.3180, supporting an immunometabolic contribution to clinical severity within EBV-naïve/low participants.

Together, these data identify an EBV-naïve/low subgroup within paediatric LC with severity-linked immunometabolic and haematological features, including higher IL-12p40, basophil counts, vitamin B1 and anti-DFS70 positivity in participants with better functional status.

 

[SNT Gatchaman]

This longitudinal structure also helps explain why adult-derived frameworks may not fully recapitulate paediatric biology: in adults, cytokine and aAb patterns often resemble EBV-positive cohorts, whereas in children, the lower prevalence of latent EBV infection may preserve discriminatory power to detect cytokine and metabolic correlates of reduced fatigue and recovery-associated trajectories.

When stratifying paediatric LC by EBV exposure, we observed a selective association of EBV-experienced status with components of the antiviral, innate and regulatory cytokine network, but not with a broad autoantibody signature. These data argue that EBV infection in paediatric LC is linked to a more activated antiviral/innate cytokine milieu and a neutrophil response, rather than to a generalised break in B-cell tolerance or a distinct aAb-defined subgroup. In postural orthostatic tachycardia syndrome, which can also occur post SARSCoV-2 infection, GPCR aAbs have been similarly elevated as reported here, with levels not differing from controls and no correlation with disease severity.

Importantly, EBV reactivation appeared rare in line with EBV reactivation known from other paediatric cohorts, contrasting adult LC where reactivation can define a subgroup; in children, EBV serostatus thus acts less as a transient epiphenomenon of viral stress and more as a stable imprint of prior herpesvirus experience that segregates a neutrophil–cytokine–biased subgroup.

A decrease in MCHC with improving Bell scores may reflect shifts in microcirculatory dynamics; although MCHC is not a direct viscosity readout, reductions could indicate improved erythrocyte hydration or membrane stability and thereby oxygen delivery. Given reported erythrocyte deformability defects in adult LC, recovery-associated shifts in paediatric red-cell rheology may represent a tractable component of resolution.