Abstract: The present invention relates to antigens extracted from mammalian malpighian epithelia, in particular rat esophageal epithelium or human epidermis, which are specifically recognized by the autoantibodies present in patients suffering form rheumatoid arthritis in respect of antigenic determinants in common with filaggrin and human profilaggrin, as well as to the antigenic proteins of which said antigens are composed and to the peptide fragments derived therefrom. The invention relates to the use of these antigens, proteins and peptide fragments, and that of filaggrin and human profilaggrin, for the preparation of antigenic compositions, and to their applications, in particular for the diagnosis of rheumatoid arthritis. The invention also relates to the preparation of antibodies directed towards these antigens, and to their applications.

Abstract: Peptides are derived from the envelope glycoprotein of HIV virus and having one of the following formulae ##STR1## in which X represents an NH.sub.2 group which is free or converted into an amide by one or two alkyl groups comprising from 1 to 5 carbon atoms, and Z represents either an OH group which is free or present as an alkoxy and thereby containing an alkyl group comprising from 1 to 5 carbon atoms, and in which at least one of the Cys residues is deleted, substituted or protected.The peptides are applied to the detection of infection caused by the viruses HIV-1 and/or HIV-2 and to the vaccination against AIDS.