Humoral cross-coronavirus responses against the S2 region in children with Kawasaki disease

Identification of a mimotope of a complex gp41 Human Immunodeficiency VIrus epitope related to a non-structural protein of Hepacivirus previously implicated in Kawasaki disease

Background

We have previously isolated a highly mutated VH1-02 antibody termed group C 76-Q13-6F5 (6F5) that targets a conformational epitope on gp41. 6F5 has the capacity to mediate Ab dependent cell cytotoxicity (ADCC). When the VH1-02 group C 76 antibodies variable chain sequence was reverted to germline (76Canc), this still retained ADCC activity. Due to this ability for the 76Canc germline antibody to functionally target this epitope, we sought to identify a protein target for vaccine development.

Methods

Initially, we interrogated peptide targeting by screening a microarray containing 29,127 linear peptides. Western blot and ELISAs were used to confirm binding and explore human serum targeting. Autoimmune targeting was further interrogated on a yeast-displayed human protein microarray.

Results

76Canc specifically recognized a number of acidic peptides. Meme analysis identified a peptide sequence similar to a non-structural protein of Hepacivirus previously implicated in Kawasaki disease (KD). Binding was confirmed to top peptides, including the Hepacivirus-related and KD-related peptide. On serum competitions studies using samples from children with KD compared to controls, targeting of this epitope showed no specific correlation to having KD. Human protein autoantigen screening was also reassuring.

Conclusions

This study identifies a peptide that can mimic the gp41 epitope targeted by 76C group antibodies (i.e. a mimotope). We show little risk of autoimmune targeting including any inflammation similar to KD, implying non-specific targeting of this peptide during KD. Development of such peptides as the basis for vaccination should proceed cautiously.

Cross-protective humoral immunity to coronaviruses from SARS coronavirus 2-naïve sera of children with Kawasaki disease

OBJECTIVES

SARS coronavirus 2 (SARS-CoV-2)-associated multi-system inflammatory syndrome in children indicates that viruses can trigger a Kawasaki disease (KD)-like hyperinflammation. A plausible hypothesis was that coronavirus-specific 'holes' in humoral immunity could cause both diseases.

METHODS

To determine whether SARS-CoV-2-naïve patients with KD have inferior humoral immunity for the novel coronavirus, sera of children with KD and control children from year 2015 to 2021 were subjected to ELISA, microwestern, and neutralization assays to evaluate the capabilities in recognizing the receptor-binding domain of SARS-CoV-2, spotting spike proteins of three respiratory syndromic coronaviruses, and blocking SARS-CoV-2 from binding to angiotensin-converting enzyme 2 receptors in vitro, respectively.

RESULTS

29 patients with KD before 2019, 74 patients with KD in 2019 or 2020, 54 non-febrile controls, and 24 febrile controls were included in the study. SARS-CoV-2 was recognized on ELISA for both patients with KD in 2016 and those with KD in 2020. Microwestern demonstrated cross-reactive IgG in an all-or-none manner towards three spike proteins of syndromic coronaviruses regardless of sample year or KD status. The ratio between the sera that recognized all spike proteins and those that recognized none (51 vs. 47) was significantly higher from patients with KD than from non-febrile controls (17 vs. 32; p 0.047) but not from febrile controls (13 vs. 11; p 0.85). Most positive sera (12 of 17 controls, 5 of 8 patients with KD before 2019, and 28 of 33 patients with KD in 2019 or 2020) offered protection comparable to low-titre sera from the WHO reference panel.

DISCUSSION

Humoral immunity of SARS-CoV-2-naïve children with KD was not inferior to that of controls in offering cross-protection against the novel coronavirus.