Abstract: The present invention concerns a modified polypeptide containing at least an immunodominant region and the connecting loop between N- and C-helices of gp41 ectodomain of HIV-1, wherein the connecting loop includes at least a linker fragment having: —a size convenient for keeping the native conformation of the interaction between N- and C-helices, and —an hydrophily sufficient to provide a soluble and stable trimeric form to said modified polypeptide.

Abstract: A method for obtaining a vaccine against the infection of an animal host by a retrovirus capable of penetrating into a host's target cell, where the target cell possesses a membrane receptor for a protein of the host, by preparing candidate vaccine agents based on a modified polypeptide having at least part of an envelope protein of the retrovirus, where the polypeptide has at least one fragment of an immunodominant region of the envelope protein, the fragment containing at least one conserved amino acid of the immunodominant region present in the pathogenic strain, wherein the polypeptide induces an immune response directed both against the immunodominant region and against the protein of the host; and selecting as a vaccine such a modified polypeptide chosen from those which induce an immune response directed against said immunodominant region of the envelope protein and not against the protein of the host.

Abstract: A method for obtaining a vaccine against the infection of an animal host by a retrovirus capable of penetrating into a host's target cell, where the target cell possesses a membrane receptor for a protein of the host, by preparing candidate vaccine agents based on a modified polypeptide having at least part of an envelope protein of the retrovirus, where the polypeptide has at least one fragment of an immunodominant region of the envelope protein, the fragment containing at least one conserved amino acid of the immunodominant region present in the pathogenic strain, wherein the polypeptide induces an immune response directed both against the immunodominant region and against the protein of the host; and selecting as a vaccine such a modified polypeptide chosen from those which induce an immune response directed against said immunodominant region of the envelope protein and not against the protein of the host.

Abstract: The present invention provides peptides which are based on the HIV GP41 protein and have inhibitory activity against the fusion of HIV virus to its target cells. The invention also provides therapeutic methods based on the administration of the peptides of the invention to a subject infected with the HIV virus.

Abstract: A method of searching for and obtaining a vaccine against the pathogenic effects related to the infection of an animal or human host by a retrovirus that penetrates into a target cell of the host, and a vaccine obtained by the method are provided. The method includes preparing candidate vaccine agents based on a polypeptide comprising at least part of an envelope protein of a pathogenic strain of the retrovirus and selecting as the vaccine a modified polypeptide chosen from polypeptides that induces an immune response directed against an immunodominant region of an envelope protein of the retrovirus and not against a protein of the host.