The biosafety of GM crops needs to be thoroughly scrutinized
for their potential allergenicity, prior to their introduction into the market. The source of the protein, sequence similarity with known allergenic
proteins, in vitro digestibility and
degradability, sera binding tests, animal models and clinical tests are the various
components of the allergenicity assesment recommended by the Codex Alimentarius
guidelines. There may be ethical issues
over these clinical or immunological tests as they may expose patients to harmful
substances that may elicit adverse reactions. A ‘weight of evidence’ approach that
includes bioinformatics, digestibility
and animal models is recommended by the Codex Alimentarius guidelines to assess
the risk of allergenicity of GM foods.The in silico sequence analysis is prequisite to the various strategies employed
for assessing the potential allergenicity.. A revised
decision tree approach has been set
forth by the Food and Agricultural Organization/World Health Organization (FAO/WHO)
of the United Nations to advance the startegy for allergy-related safety assessment
of genetically transformed foods.
This decision tree
has increased the rigor in the evaluation of amino acid sequence homology from 8
amino acids to 6 amino acids, and a 35% identity match over any 80 or more
contiguous amino acids throughout the sequence of the protein. Sequence homology
between the proteins has highly probability of
causing cross-reactions. However, structures with low sequence
similarity may also cause cross-reactivity due to the fact that the structural similarity
is possible even in absence of sequence similarity. This database provides a listing
of the domains in the allergens listed in the allergen online database. This database
can be searched for the domains deduced to be present in transgenic proteins or
other query proteins and this can serve as a resource for detection of possible
allergenicity.
