A method for identifying an immunosuppressive domain in the fusion protein of an enveloped RNA virus having a lipid membrane, said method comprising: a. Identifying at least one well conserved domain among the group consisting of the membrane domains of the fusion protein and the surface domains of the fusion protein; i. by aligning virus candidates from viruses within an order using an alignment tool; if no stretches of conserved amino acids ranging from 6 to 30 amino acids long are identified by step (i), ii. by aligning virus candidates from the family of viruses using an alignment tool; if no stretches of conserved amino acids ranging from 6 to 30 amino acids long are identified by step (ii), iii. by aligning virus candidates from the subfamily of viruses using an alignment tool; if no stretches of conserved amino acids ranging from 6 to 30 amino acids long are identified by step (iii), iv. by aligning virus candidates from viruses from a genus using an alignment tool; if no stretches of conserved amino acids ranging from 6 to 30 amino acids long are identified bv step (iv) v. by aligning individual viral sequences from a single species of virus using an alignment tool; b. Providing at least one peptide with the sequence of said identified at least one well conserved domain; c. Optionally dimerizing or multimerizing said at least one peptide; and d. Confirming the immunosuppressive activity of said at least one optionally dimerized or multimerized peptide by testing said at least one optionally dimerized or multimerized peptide for immunosuppressive activity. a. Identifying at least one well conserved domain among the group consisting of the membrane domains of the fusion protein and the surface domains of the fusion protein; i. by aligning virus candidates from viruses within an order using an alignment tool; if no stretches of conserved amino acids ranging from 6 to 30 amino acids long are identified by step (i), ii. by aligning virus candidates from the family of viruses using an alignment tool; if no stretches of conserved amino acids ranging from 6 to 30 amino acids long are identified by step (ii), iii. by aligning virus candidates from the subfamily of viruses using an alignment tool; if no stretches of conserved amino acids ranging from 6 to 30 amino acids long are identified by step (iii), iv. by aligning virus candidates from viruses from a genus using an alignment tool; if no stretches of conserved amino acids ranging from 6 to 30 amino acids long are identified bv step (iv) v. by aligning individual viral sequences from a single species of virus using an alignment tool; i. by aligning virus candidates from viruses within an order using an alignment tool; if no stretches of conserved amino acids ranging from 6 to 30 amino acids long are identified by step (i), ii. by aligning virus candidates from the family of viruses using an alignment tool; if no stretches of conserved amino acids ranging from 6 to 30 amino acids long are identified by step (ii), iii. by aligning virus candidates from the subfamily of viruses using an alignment tool; if no stretches of conserved amino acids ranging from 6 to 30 amino acids long are identified by step (iii), iv. by aligning virus candidates from viruses from a genus using an alignment tool; if no stretches of conserved amino acids ranging from 6 to 30 amino acids long are identified bv step (iv) v. by aligning individual viral sequences from a single species of virus using an alignment tool; b. Providing at least one peptide with the sequence of said identified at least one well conserved domain; c. Optionally dimerizing or multimerizing said at least one peptide; and d. Confirming the immunosuppressive activity of said at least one optionally dimerized or multimerized peptide by testing said at least one optionally dimerized or multimerized peptide for immunosuppressive activity.