HSV-2 increases the mitochondrial aspartate amino transaminase characteristic of tumor cells.

A set of polypeptides has previously been described as being immunoprecipitated from tumor cell lysates by the sera of tumor-bearing animals (TBS) or by antisera raised to herpes simplex virus type 2 (HSV-2)-infected cells. These polypeptides were not immunoprecipitated from control cells. The principal polypeptides detected of MW 200, 90 (U90 and L90), 40, and 32 kDa were increased by HSV-2 infection. This communication describes the purification of the 40-kDa protein and its identification by amino acid sequence analysis as being homologous to the mature form of mitochondrial aspartate amino transaminase (mAAT). Two different forms of mAAT were purified and sequenced. One form, of low abundance, was immunoprecipitated by TBS and corresponded to the 40-kDa protein immunoprecipitated from tumor, but not control, cell lysates. Western blotting of the 40-kDa protein immunoprecipitated by TBS showed that it was a form of mAAT found only in tumor cells. The other abundant form reacted in Western blots with antibody to mAAT and was clearly the constitutive enzyme, present in all cells. In general, mAAT was increased up to fourfold after infection with HSV-2, HSV-2 infection also increased mAAT enzyme activity. Northern blotting and quantitative PCR showed that mAAT was induced by HSV-2 at the level of transcription. The specific form of mAAT immunoprecipitated from tumor, but not control, cell lysates could have a role in tumorigenesis, could be a putative tumor cell marker, or could be a target for antitumor drugs. HSV-2 probably induces enzymes of glutamine metabolism because HSV-2 requires glutamine for growth, thus revealing potential new antiviral targets.

Patients with cervical cancer produce an antibody response to an HSV-inducible tumour-specific cell polypeptide.

Anti-sera raised against HSV-2-infected cells (WI) and the sera of animals bearing tumours (TBS) to HSV-2 transformed cells contain antibodies to a set of tumour-specific cell-coded polypeptides. The specificity of these polypeptides for tumour cells is monitored by the ability of [35S]-L-methionine labelled proteins to be immunoprecipitated by these anti-sera, in contrast to control cells from which the polypeptides are not precipitated. The polypeptides which share an epitope and are co-precipitated are of MWs 90,000 (a doublet), 40,000 and 32,000. The upper 90,000-MW polypeptide (U90) is induced by HSV-2 infection. This communication deals with the 40,000-MW polypeptide which was shown to be immunoprecipitated by TBS and a monoclonal antibody (MAb) raised to the DNA-binding proteins of HSV-2-infected cells. Immunological and biochemical studies reveal that the 40,000-MW protein which is immunoprecipitated comprises more than one polypeptide, and that the proteins may need to interact to produce the peptide pattern specific for the tumour form of the immunoprecipitated 40,000-MW protein. WI antisera and TBS both recognise antigens specific for tumour cells in sections of cervical-carcinoma tissue. Sera from patients with cancer of the cervix contain antibodies to a cell-coded polypeptide of MW 40,000, which by peptide analysis is indistinguishable from the 40,000-MW polypeptide induced by HSV-2 infection and immunoprecipitated by WI and TBS.

A transformation-specific polypeptide distinct from heat shock proteins is induced by herpes simplex virus type 2 infection.

A tumour-specific polypeptide designated U90 is one of a set of polypeptides which are encoded by the host cell and are specific for the transformed cell state, being immunoprecipitated by the sera of tumour-bearing animals. The interest in these tumour-specific polypeptides centres on the finding that they are also recognized by antisera raised against herpes simplex virus type 2 (HSV-2)-infected cells, implying some role for HSV-2 in tumorigenesis. The peptide map of HSV-2-induced U90 is indistinguishable from that of U90 present in uninfected tumour cells, including mouse cells transformed by human papillomavirus type 16. In tumour cells, U90 is located principally in the plasma membrane fraction and cannot be induced by heat shock, glucose starvation, or treatment with tunicamycin or calcium ionophore. U90 is not related to either the heat shock protein of Mr 90,000 (HSP90) or the glucose-related polypeptide of Mr 94,000 (GRP94) as determined by peptide mapping and the use of monospecific, monoclonal and antipeptide antibodies. This suggests that U90 is a novel transformation-specific protein which can be induced by infection with HSV-2.