POS0072 COMPREHENSIVE IMMUNE PROFILING OF 20 CHILDREN WITH MULTISYSTEM INFLAMMATORY SYNDROME

Background:

Multisystem inflammatory syndrome in children (MIS-C) is a rare complication of SARS-CoV-2 infection in the pediatric population, caused by extensive activation of immune system. The understanding of the distorted immune response is still in the early stages.

Objectives:

To analyze comprehensively immune profile in MIS-C patients including detailed serologic response to SARS-CoV-2 in comparison with control groups.

Methods:

Blood samples of consecutive MIS-C patients were collected at admission. Flow cytometric analysis of all lymphocyte populations including T and B cell differentiation was performed. Immunophenotyping was performed by six-color panels for the detection of lymphocyte subpopulations. Anti-SARS-CoV-2 specific antibodies were measured in the patients serum. The IgA and IgG antibodies against S protein, the IgG S1 and S2 specific antibodies, antibodies against nucleoprotein and neutralising antibodies were measured. Patients were assessed for a wide range of auto-antibodies, namely ANA, anti-ENA (Jo-1, PL-7, PL-12, SRP, Mi-2, Ku, Pm/Scl 100, Scl-70), myositis specific antibodies (EJ, MDA-5, TIH-Y, Ro52, SAE-1, SAE-2, NXP-2), anti-dsDNA, anti-phopholipid antibodies (aCl IgA, IgG, IgM, antiβ2GPI IgG, IgM) and ANCA. Control groups to compare specific antibody response consisted of 14 healthy children and 19 healthy adults, who had SARS-CoV-2 infection in the last 2 months.

Results:

Samples of 20 patients were included (14/20 boys, median age 12.4 years). Patients had higher percentage of double negative T cells and low numbers of of cytokine producing T cells Th1, Th2 and Th17. . Numbers of immune competent and CD21+ transitional B cells were also lowered. All patients had positive antibodies against SARS-CoV-2 including neutralising antibodies. Nine (9/19; 47 %) patients had high titer (≥1:160) of neutralising antibodies. Results were compared with 2 control groups; 14 healthy children (7/14 boys; median age 8 years,) and 19 healthy adults, who all experienced SARS-CoV-2 infection in the last two months. Patients with MIS-C had significantly higher levels of anti-S IgA (p<0.0001), patients with MIS-C and healthy children had significantly higher titers of anti-S1 (p=0.001) and significantly lower titers of anti-S2 (p=0.016) in comparison to adults (Figure 1). No differences were found in the titers of neutralising antibodies and anti-N antibodies. All patients were ANA negative, 19/20 patients were anti-ENA negative, whereas 1 patient had anti-Ro antibodies in low titre. Three patients had aCL IgG in medium titre and 2 patients anti-beta2GPI IgG in low titre. Patients were negative for all other autoantibodies.

Conclusion:

The immune response in MIS-C patients is specific with most prominent differences in elevated percentage of double negative T cells and low numbers of Th1, Th2, Th17 and CD21+ transitional B cells. MIS-C patients have distinct serologic response with high anti-S IgA, high anti-S1 and low anti-S2 titres.

Figure 1.

Antibody titres in patient group and control groups. Mean value with SEM s shown.

Disclosure of Interests:

None declared.

Low prevalence of active COVID-19 in Slovenia: a nationwide population study of a probability-based sample

Objectives

Accurate population-level assessment of the coronavirus disease 2019 (COVID-19) burden is fundamental for navigating the path forward during the ongoing pandemic, but current knowledge is scant. We conducted the first nationwide population study using a probability-based sample to assess active severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, combined with a longitudinal follow-up of the entire cohort over the next 6 months. Baseline SARS-CoV-2 RNA testing results and the first 3-week follow-up results are presented.

Methods

A probability-based sample of the Slovenian population comprising data from 2.1 million people was selected from the Central Population Register (n = 3000). SARS-CoV-2 RNA was detected in nasopharyngeal samples using the cobas 6800 SARS-CoV-2 assay. Each participant filled in a detailed baseline questionnaire with basic sociodemographic data and detailed medical history compatible with COVID-19. After 3 weeks, participants were interviewed for the presence of COVID-19–compatible clinical symptoms and signs, including in household members, and offered immediate testing for SARS-CoV-2 RNA if indicated.

Results

A total of 1368 individuals (46%) consented to participate and completed the questionnaire. Two of 1366 participants tested positive for SARS-CoV-2 RNA (prevalence 0.15%; posterior mean 0.18%, 95% Bayesian confidence interval 0.03–0.47; 95% highest density region (HDR) 0.01–0.41). No newly diagnosed infections occurred in the cohort during the first 3-week follow-up round.

Conclusions

The low prevalence of active COVID-19 infections found in this study accurately predicted the dynamics of the epidemic in Slovenia over the subsequent month. Properly designed and timely executed studies using probability-based samples combined with routine target-testing figures provide reliable data that can be used to make informed decisions on relaxing or strengthening disease mitigation strategies.

Genetic diversity and macrolide resistance of Mycoplasma pneumoniae isolates from two consecutive epidemics in Slovenia

Two nationwide Mycoplasma pneumoniae epidemics occurred in Slovenia between 2006 and 2016. The aim of this study was to assess which M. pneumoniae genotypes were present in our area during the selected timeframe, whether the origin of the epidemics was monoclonal or polyclonal and whether the proportion between detected genotypes changed over time. We were also interested in the presence of macrolide resistance (MR) and whether it could be linked to specific genotypes. We performed pyrosequencing of the P1 gene and multiple-locus variable-number tandem repeat (VNTR) analysis (MLVA) typing from 872 M. pneumoniae isolates obtained from respiratory tract infections (RTI)-suffering patients. Additionally, isolates were tested for the presence of MR implicated mutations in the 23S rRNA gene. The MLVA typing results revealed that three main genotypes, MLVA-3,5,6,2, MLVA-3,6,6,2 and MLVA-4,5,7,2, were constantly present and occasionally joined by less abundant, short-lived genotypes, which were detected mostly, but not exclusively, during epidemics. We also noticed a switch in abundance from MLVA-3,5,6,2 and MLVA-3,6,6,2, which dominated in the first epidemic (77.0%; 97/126), to MLVA-4,5,7,2 (71.6%; 428/598), which dominated in the second. Similar to this finding, the dominant P1 type also shifted from type 2 to type 1, although a complete P1 type shift was not observed, since both types remained in circulation. MR was detected in 0.8% (7/872) of M. pneumoniae isolates. Our results seem to suggest that MR remains sporadic in Slovenia at this point in time and that both recent epidemics were polyclonal in nature and, possibly, to some extent, fuelled by the P1 type dominance change.

Hantavirus infections

Over the past few decades understanding and recognition of hantavirus infection has greatly improved worldwide, but both the amplitude and the magnitude of hantavirus outbreaks have been increasing. Several novel hantaviruses with unknown pathogenic potential have been identified in a variety of insectivore hosts. With the new hosts, new geographical distributions of hantaviruses have also been discovered and several new species were found in Africa. Hantavirus infection in humans can result in two clinical syndromes: haemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS) caused by Old World and New World hantaviruses, respectively. The clinical presentation of HFRS varies from subclinical, mild, and moderate to severe, depending in part on the causative agent of the disease. In general, HFRS caused by Hantaan virus, Amur virus and Dobrava virus are more severe with mortality rates from 5 to 15%, whereas Seoul virus causes moderate and Puumala virus and Saaremaa virus cause mild forms of disease with mortality rates <1%. The central phenomena behind the pathogenesis of both HFRS and HCPS are increased vascular permeability and acute thrombocytopenia. The pathogenesis is likely to be a complex multifactorial process that includes contributions from immune responses, platelet dysfunction and the deregulation of endothelial cell barrier functions. Also a genetic predisposition, related to HLA type, seems to be important for the severity of the disease. As there is no effective treatment or vaccine approved for use in the USA and Europe, public awareness and precautionary measures are the only ways to minimize the risk of hantavirus disease.

Viral load and immune response dynamics in patients with haemorrhagic fever with renal syndrome

Haemorrhagic fever with renal syndrome (HFRS) in Slovenia can be caused by infection with either Dobrava (DOBV) or Puumala (PUUV) virus, but a clear difference in disease severity is observed. We hypothesized that the wide spectrum of disease observed among HFRS patients might be related to differing immune responses and viral load kinetics. To test this hypothesis we analysed sequential blood samples from 29 HFRS patients hospitalized in Slovenia. Measuring viral RNA in patient samples revealed that viraemia lasts for longer than previously believed, with DOBV or PUUV-infected patients having viraemias lasting on average 30 days or 16 days, respectively. DOBV-infected patients were found to have a higher viral load than the PUUV-infected patients (10(7) vs. 10(5) RNA copies/mL). Both DOBV and PUUV-infected patients had IgM at the time of hospital admission, but there was a difference in IgG antibody dynamics, with only a minority of DOBV-infected patients having IgG antibodies. In our study, elevated levels of IL-10, TNF-α and IFN-γ were detected in all of the samples regardless of the causative agent. In DOBV-infected patients the decrease in cytokine secretion level appeared around day 20 post-infection, while in PUUV-infected patients the change was earlier. In general, our findings point toward notable differences between PUUV and DOBV infections, in terms of viral load and antibody and cytokine response dynamics, all of which may be reflected in differing disease severities and clinical outcomes.

Increased number of cases of haemorrhagic fever with renal syndrome in Slovenia, January to April 2012

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Increased number of cases of haemorrhagic fever with renal syndrome in Slovenia, January to April 2012

Haemorrhagic fever with renal syndrome is endemic in parts of Slovenia. Since 1999, in January to April each year, the number of notified cases has generally been low (n=0-6). A high number of cases (n=26) in the first four months of 2012 has been observed, similar to that seen in the same period in 2008 (n=14). Given the increase in the number of cases at the start of 2012, we can expect a high number of cases this year.