Objectives and Study

Since January 2022 there has been a global increase in severe acute hepatitis (SAH) of unknown aetiology in children. One current hypothesis is that multiple viruses, on the background of a genetic susceptibility, trigger immune-liver damage. Over-representation of a HLA subtype associated with autoimmunity was previously reported.

Methods

Clinical data on children referred to the Irish National Paediatric Liver Centre, January - November 2022, meeting the WHO/ECDC definition of SAH were prospectively collected. Cases were <16years and had acute hepatitis (non A-E) with aspartate transaminase (AST) or alanine transaminase (ALT) >500 IU/L. Other definitive causes of hepatitis were excluded. HLA typing was performed using NGS and virus detection with PCR.

Results

Thirty five children (18 F) met the case definition. Median age was 4years (IQR 2.25, 5.55). Clinical features included jaundice(63%) abdominal pain(66%), vomiting(43%), lethargy(89%) and encephalopathy(29%). Median peak AST was 2022 IU/l(IQR 999, 3756), ALT was 1838 IU/l(IQR 817, 2739).

Two groups were observed; those with jaundice (63%) (median peak bilirubin 161umol/l) and those without. Of those with jaundice, 41% (n=9) progressed to acute liver failure. Two children received a liver transplant and 1 died, the remainder recovered. Of those without jaundice, 85% have had ongoing intermittent elevation of AST/ALT (follow-up to 10 months).

Adenoviremia was found in 34% of the cohort, 34% had HHV7 viremia and 12/29 (41%) were positive for AAV2. 13/35(37%) had intermittent autoantibody positivity, 1 had high IgG. Of the 26 children tested, 62% of cases (versus 20% Irish blood donor controls) carry HLA DRB1*04:01 (OR 6.4 p<0.0001) and 12% cases HLA DRB1*04:07 versus 2.4% controls (OR 5.3, p=0.02).

Conclusions

The incidence of SAH of unknown aetiology in Ireland in 2022 is alarming. A significant proportion of the cohort are positive for HLA DRB1 04:01:01/DRB1 04:07:01, suggestive of autoimmune predisposition. Long-term outcomes for these children need to be defined further.

Objectives and Study

Mucosal-associated invariant T (MAIT) cells, defined as CD3+ Valpha7.2+ CD161++ T lymphocytes are central in protecting the biliary mucosa from microbiota due to their predominant location in the portal tracts of the human liver. In autoimmune liver disease (AILD), MAIT cell cytokine production is significantly reduced compared to healthy subjects. The functional activity of MAIT cells in children with AILD has not been investigated. We aim to 1) immunophenotype paediatric MAIT cells in AILD and 2) assess their cytokine potential to establish their role in this lifelong condition which often starts in childhood.

Methods

Mass cytometry (CyTOF; Cytometry by time of flight) was performed on peripheral blood mononuclear cells (PBMC) from children with AILD (AIH Type 1, N=8, median age 14yrs (range 9-14), and PSC, N=8, 14yrs (range 12-15)) and in healthy children (HC) (N=8, 12yrs (range 5-15). PBMCs treated with a cell stimulation cocktail containing phorbol 12-myristate 13-acetate (PMA) and ionomycin were incubated for 4hours prior to downstream CyTOF investigation. Untreated (UNSTIM) paired PBMCs from the same patients were used as controls.

Results

Stimulated (STIM) blood MAIT cells from children with PSC had higher TNF-a (p=0.01) production than AIH patients and healthy children (Figure 1a). Although a similar trend is observed in their total CD3+ T lymphocytes, the response is 100-fold less than MAIT cells (Figure 1b). In contrast, stimulated MAIT cells from healthy children had higher IFNγ production compared to the AILD cohort.

Conclusions

Activated MAIT cells from adults with AILD have impaired function with reduced TNF-a and IFNγ production described. Reduced IFNγ expression in our paediatric AILD cohort mirrors this finding but higher TNF-a production suggests preserved proinflammatory MAIT cell function in the TNF superfamily pathway in children with PSC which may contribute to disease progression.

Objectives and Study

Since January 2022 there has been an increase in cases of acute hepatitis of unknown cause in children.

Methods

We analyzed patients observed since January 2022 that met the case definition: acute hepatitis not A-E, AST or ALT ≥500 IU/L, needing admission.

We excluded cases with similar features in the period: one hepatitis A, three neonatal enteroviral hepatitis, three hemophagocytic lymphohistiocytosis, one Epstein-Barr, four autoimmune hepatitis, two hepatitis-aplasia, one metabolic disease, one Kawasaki Syndrome.

Until November 2022 there were 15 children that met the definition, all ≤11 years of age.

We reviewed medical records, serology, and molecular tests for viruses at centre and National Center of Virology. An immunologic research is in process.

Results

The median age was 4.6 years. Presenting features were jaundice (75%), vomiting (87%), and fever (60%). Median values were AST:6149 IU/L, ALT:4419 IU/L ,TBilirubin:7 mg/dL, INR:2.1, Fibrinogen:129 mg/dL. Acute liver failure (ALF) developed in 8 (53%).

Among the 14 patients tested for adenovirus, 6 were positive (43%) in any sample. Other viruses were found (1 each: RSV, Influenza, norovirus,sapovirus, enterovirus, HHV6). In 9 patients tested, SARS-CoV2 serology was positive in 8. Autoimmune markers showed positive ANA in 3/15, IgG was elevated in 2/15.

Four patients received methyl-prednisolone (2 mg/kg): 3 showed improvement, one died after transplantation

Three patients received gamma-globulin 1g/kg, no definite effect on disease was observed.

Adenovirus was identified in 2/8 with ALF. Four ALF patients received plasmapheresis+HDF. Two patients received a liver transplant. Two patients died (one after transplantation) both due to cerebral oedema.

Conclusions

In this series involving 15 children, adenovirus was isolated in 43% but its role in the pathogenesis is yet to be established. The history of prior SARS-CoV2 infection should not be disregarded. This syndrome was associated to multiple other viruses, and had a high rate of ALF.