Molecular mimicry and autoimmunity in the time of COVID-19

Infectious diseases are commonly implicated as potential initiators of autoimmune diseases (ADs) and represent the most commonly known factor in the development of autoimmunity in susceptible individuals. Epidemiological data and animal studies on multiple ADs suggest that molecular mimicry is one of the likely mechanisms for the loss of peripheral tolerance and the development of clinical disease. Besides molecular mimicry, other mechanisms such as defects in central tolerance, nonspecific bystander activation, epitope-determinant spreading, and/or constant antigenic stimuli, may also contribute for breach of tolerance and to the development of ADs. Linear peptide homology is not the only mechanism by which molecular mimicry is established. Peptide modeling (i.e., 3D structure), molecular docking analyses, and affinity estimation for HLAs are emerging as critical strategies when studying the links of molecular mimicry in the development of autoimmunity. In the current pandemic, several reports have confirmed an influence of SARS-CoV-2 on subsequent autoimmunity. Bioinformatic and experimental evidence support the potential role of molecular mimicry. Peptide dimensional analysis requires more research and will be increasingly important for designing and distributing vaccines and better understanding the role of environmental factors related to autoimmunity.

Immune-mediated liver injury following COVID-19 vaccination: A systematic review

Immune-mediated liver injury (ILI) following coronavirus disease 2019 (COVID-19) vaccination is not well-characterized. Therefore, we systematically reviewed the literature on ILI after COVID-19 vaccination. We searched PubMed, Cochrane, Ovid, Embase, and gray literature to include articles describing ILI following COVID-19 vaccination. Reports without confirmatory evidence from liver biopsy were excluded. Descriptive analysis, and study quality were reported as appropriate. Of the 1,048 articles found, 13 (good/fair quality; 23 patients) were included. Studies were primarily from Europe (n = 8), America (n = 2), Asia (n = 2), or Australia (n = 1). Patients were predominantly females (62.5%) of age 55.3 years (49.1-61.4), with an antecedent exposure to Moderna messenger RNA (mRNA)-1273 (47.8%), Pfizer-BioNTech BNT162b2 mRNA (39.2%), or ChAdOx1 nCoV-19 vaccine (13%). Pre-existing comorbidities (69.6%) were common, including liver disease in 26.1% and thyroid disorders in 13% of patients. About two-thirds of the patients were on concurrent medications (paracetamol, levothyroxine, statins, and non-steroidal anti-inflammatory drugs). Jaundice was the most common symptom (78.3%). Peak bilirubin, alanine aminotransferase, and alkaline phosphatase levels were 10.8 (6.8-14.8) mg/dl, 1,106.5 (757.0-1,702.5) U/L, and 229 (174.6-259.6) U/L, respectively. Histological findings were intense portal lymphoplasmacytic infiltrate with interface hepatitis. Steroids were used in 86.9% of patients, and complete response, recovering course, and death were reported in 56.5%, 39.1%, and 4.3% of patients, respectively. ILI following COVID-19 vaccination is rare. The diagnosis is established on temporal correlation, biochemical findings, and histopathology. Prognosis is excellent with corticosteroids. Causality establishment remains a challenge.

Vaccination in pediatric acquired inflammatory immune-mediated neuromuscular disorders

AIM

To analyse literature data on vaccine related induction, worsening of the disease and disease reccurrences as well as vaccine safety and efficacy among pediatric patients with acquired inflammatory immune-mediated neuromuscular disorders (NMD).

METHODS

Medline, Pub Med and Scopus database search from 1975 to 2020 focused on pediatric age was conducted including peer reviews, meta analyses and epidemiological studies on vaccination and Guillain-Barré syndrome (GBS), Bell's palsy, optic neuritis (ON), myasthenia gravis (MG), chronic inflammatory demyelinating polyneuropathy (CIDP) and immune-mediated inflammatory myopathy (IM).

RESULTS AND CONCLUSION

s: There are no strong evidence supporting relationship between vaccination with different pediatric vaccines and development of first episodes or reccurrences of GBS, Bell's palsy, optic neuritis (ON), juvenile MG, CIDP, and IM. The vaccination and revaccination with inactivated vaccines is considered safe in children with medical history of GBS, Bell's palsy, ON, MG and IM. Caution when immunization against influenza, quadrivalent conjugated meningococcal vaccine (MCV4) and pneumococcal disease and avoiding tetanus toxoid immunization in CIDP patients is suggested. Patients with immune mediated acquired NMD should be vaccinated with live vaccines before the initiation of immunosupressive treatment. Immunosuppressed patients with low protective antibody titers should be considered for revaccination.

Acute myelitis and ChAdOx1 nCoV-19 vaccine: Casual or causal association?

A 44-year-old previously healthy woman developed acute myelitis in close temporal relationship with ChAdOx1 nCoV-19 vaccine first-dose administration. The neurological involvement was mainly sensory with neuroimaging showing two mono-metameric lesions involving the posterior and lateral cord at dorsal level. Significant improvement was promptly recorded with high-dose intravenous steroids, with complete recovery within one month.

The strict temporal relationship between vaccination and myelitis, together with the absence of clues pointing to alternative diagnoses, might suggest a conceivable role for anti-SARS-CoV-2 vaccine as immunological trigger, although a causal relationship has yet to be established and our preliminary observation suggests caution.

Vaccine-induced autoimmunity: the role of molecular mimicry and immune crossreaction

Since the early 1800s vaccines have saved numerous lives by preventing lethal infections. However, during the past two decades, there has been growing awareness of possible adverse events associated with vaccinations, cultivating heated debates and leading to significant fluctuations in vaccination rates. It is therefore pertinent for the scientific community to seriously address public concern of adverse effects of vaccines to regain public trust in these important medical interventions. Such adverse reactions to vaccines may be viewed as a result of the interaction between susceptibility of the vaccinated subject and various vaccine components. Among the implicated mechanisms for these reactions is molecular mimicry. Molecular mimicry refers to a significant similarity between certain pathogenic elements contained in the vaccine and specific human proteins. This similarity may lead to immune crossreactivity, wherein the reaction of the immune system towards the pathogenic antigens may harm the similar human proteins, essentially causing autoimmune disease. In this review, we address the concept of molecular mimicry and its application in explaining post vaccination autoimmune phenomena. We further review the principal examples of the influenza, hepatitis B, and human papilloma virus vaccines, all suspected to induce autoimmunity via molecular mimicry. Finally, we refer to possible implications on the potential future development of better, safer vaccines.