Identification of two Vβ7-specific viral superantigens

The commonly used strains of laboratory mice have mouse mammary tumor viruses (MTV) integrated at various locations in their DNA. The number and position of these integrants varies from one strain of mouse to another. It has recently been shown that the genomes of many of the MTV code for superantigens. The predicted amino acid sequences of these superantigens and their specificity for TCR Vβ differs for each MTV integrant. This study contains the predicted amino acid sequence and Vβ specificity of two MTV superantigens that had not previously been analyzed. The results show that both of these MTV superantigens are specific for TCR that bear Vβ7, but unlike the MTV7 superantigen not for receptors bearing Vβ6 or Vβ8.1. The data also support the conclusion of previous studies that the COOH-terminal sequence of these proteins is a major factor in controlling their Vβ reactivity.