The recognition of pathogen-derived peptides by T lymphocytes is the cornerstone of adaptive immunity, whereby intracellular antigens are degraded in the cytosol and short peptides assemble with class I human leukocyte antigen (HLA) molecules in the endoplasmic reticulum (ER). These peptide-HLA complexes egress to the cell surface and are scrutinized by cytotoxic CD8+ T-cells leading to the eradication of the infected cell. Here we identify naturally presented HLA-B57:01 bound peptides derived from the envelope protein of the human immunodeficiency virus (HIVenv). HIVenv peptides were present at a very small percentage of the overall HLA-B57:01 peptidome (<0.1%) and both native and post-translationally modified forms of two distinct HIV peptides were identified. Notably, a peptide bearing a natively encoded C-terminal tryptophan residue was also present in a modified form containing a kynurenine residue. Kynurenine is a major product of tryptophan catabolism and is abundant during inflammation and infection. We examined the binding of these peptides at a molecular level and examine their immunogenicity in preliminary functional studies. Modest immune responses were observed to the modified HIVenv peptide, highlighting a potential role for kynurenine-modified peptides in the immune response to HIV and other viral infections. This article is protected by copyright. All rights reserved.