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SEQUENCE SIMILARITY BETWEEN THYROID SELF-PROTEIN AND HEPATITIS C VIRUS POLYPROTEIN: possible triggering mechanism of autoimmune thyroiditis

Similaridade de sequências entre auto-proteínas da tireoide e poliproteínas do vírus da hepatite C: possível mecanismo de desencadeamento da tireoidite auto-imune

ABSTRACT

Background

- Exposure to viral antigens that share amino acid sequence similar with self- antigens might trigger autoimmune diseases in genetically predisposed individuals, and the molecular mimicry theory suggests that epitope mimicry between the virus and human proteins can activate autoimmune disease.

Objective

- The purpose of this study is to explore the possible sequence similarity between the amino acid sequences of thyroid self-protein and hepatitis C virus proteins, using databanks of proteins and immunogenic peptides, to explain autoimmune thyroid disease.

Methods

- Were performed the comparisons between the amino acid sequence of the hepatitis C virus polyprotein and thyroid self-protein human, available in the database of National Center for Biotechnology Information on Basic Local Alignment Search Tool.

Results

- The sequence similarity was related each hepatitis C virus genotype to each thyroid antigen. The similarities between the thyroid and the viral peptides ranged from 21.0 % (31 identical residues out of 147 amino acid in the sequence) to 71.0% (5 identical residues out of 7 amino acid in the sequence).

Conclusion

- Bioinformatics data, suggest a possible pathogenic link between hepatitis C virus and autoimmune thyroid disease. Through of molecular mimicry is observed that sequences similarities between viral polyproteins and self-proteins thyroid could be a mechanism of induction of crossover immune response to self-antigens, with a breakdown of self-tolerance, resulting in autoimmune thyroid disease.

HEADINGS
Hepacivirus; Thyroiditis; Amino acid sequence homology; Computational biology

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