HIV-1 infection increases the expression of human endogenous retroviruses type K (HERV-K) in vitro

Antibodies to HERV-K antigens have been linked to HIV-1 infection and expression of HERV-K proteins generates T-cell cytotoxic responses in many cancers. HERV-K RNA and protein abundance was measured in HIV-1-infected and control cells. In vitro exposure of HIV-1 laboratory-adapted and primary isolates on U87MG cells increased the expression of HERV-K RNA in a dose-dependent manner. HERV-K RNA and protein burdens were significantly increased in HIV-1-producing H9 cell lines compared to H9 cells. The expression of HERV-K was synergistically increased in HIV-1-infected PBMCs after stimulation with PMA/ionomycin. Furthermore, the expression of HERV-K in PBMCs, and particularly in CD4(+) T cells, was higher in HIV-1 patients compared to control subjects. The expression of HERV-K might be related to HIV-1 pathogenesis and AIDS-associated cancers.     

Serological response to human endogenous retrovirus K in melanoma patients correlates with survival probability

A few years ago, reactivation of human endogenous retrovirus K (HERV-K) proviruses in melanoma was described. The expression of HERV-K proteins induces humoral immune responses. The aim of the present study was to elucidate the prognostic relevance of serological anti-HERV-K reactivity in melanoma patients. In a retrospective study, anti-HERV-K Gag and Env antibodies were detected in 51 of the 312 randomly selected and blinded sera from melanoma patients, but not in any of the 70 sera from healthy controls. Comparing serological HERV-K reactivity with established melanoma markers revealed a significant correlation (p = 0.018, Chi-square test) with the stage of disease classified according to the American Joint Committee on Cancer (AJCC). Anti-HERV-K reactivity was elevated in patients with acrolentiginous/mucosal/uveal melanoma (tumor subtypes developing at sun-protected sites) compared to patients with lentigo/nodular/superficial spreading melanoma (p = 0.011, Chi-square test). Patients with anti-HERV-K antibodies had a significantly decreased disease-specific overall survival (stage I-IV, p < 0.001; stage I-III, p = 0.005, log-rank test). Significantly, multivariate Cox regression analysis including prognostic markers in clinical use (e.g., AJCC stage, T-class, serum level of S100-beta) revealed serological HERV-K reactivity as an independent marker of reduced survival probability (p = 0.027) in melanoma patients with the early stages of the disease (AJCC I-III). This is the first report that the humoral anti-HERV-K immune response may provide additional prognostic information to that of established melanoma markers.     

Insertional polymorphisms of endogenous HERV-K113 and HERV-K115 retroviruses in breast cancer patients and age-matched controls

Endogenous retroviral sequences resulting from ancient retrovirus infections of germline cells account for up to 8% of the human genome. Most of these sequences are highly truncated, have been altered by mutations, and do not encode functional genes. However, some members of the human endogenous retrovirus (HERV)-K family are remarkably intact and display high genetic homology to mouse mammary tumor virus (MMTV), a retrovirus causing breast cancer in mice. Two full-length HERVs (K113 and K115) have been reported to show insertional polymorphism. We used PCR to investigate the presence of these two HERVs in 102 female breast cancer patients and an equal number of age-matched controls with no history of malignancy (age range: 25-92 years). The two groups showed no significant difference in frequency (HERV-K113, 16.7% vs. 12.7%; HERV-K115, 4.9% vs. 9.8%) and no apparent association with histology, age at diagnosis, receptor status, HER-2/neu status, or TNM stage at diagnosis. This suggests that the two HERV-Ks do not play a pathogenetic role in the majority of breast cancer patients, though they may be involved in a minority of patients. The results are discussed.     

Human endogenous retrovirus K solo-LTR formation and insertional polymorphisms: implications for human and viral evolution

Human endogenous retroviruses (HERVs) are a potential source of genetic diversity in the human genome. Although many of these elements have been inactivated over time by the accumulation of deleterious mutations or internal recombination leading to solo-LTR formation, several members of the HERV-K family have been identified that remain nearly intact and probably represent recent integration events. To determine whether HERV-K elements have caused recent changes in the human genome, we have undertaken a study of the level of HERV-K polymorphism that exists in the human population. By using a high-resolution unblotting technique, we analyzed 13 human-specific HERV-K elements in 18 individuals. We found that solo LTRs have formed at five of these loci. These results enable the estimation of HERV solo-LTR formation in the human genome and indicate that these events occur much more frequently than described in inbred mice. Detailed sequence analysis of one provirus shows that solo-LTR formation occurred at least three separate times in recent history. An unoccupied preintegration site also was present at this locus in two individuals, indicating that although the age of this provirus is estimated to be approximately 1.2 million years, it has not yet become fixed in the human population.     

Detection of lymphocytes producing a human retrovirus associated with adult T-cell leukemia by syncytia induction assay.

Recently 10 T-cell lines were established from patients with adult T-cell leukemia (ATL). During establishment of these cell lines, it was found that when T-cell lines expressing the ATL-associated retroviral antigen were cocultivated with 8C cat cells, multinucleated syncytia were formed. Retroviral antigen-negative T-cell lines did not induce syncytia. Peripheral blood lymphocytes obtained from ATL patients did not express the retroviral antigen before cultivation in vitro but became positive for the retroviral antigen after cultivation for a short period; these retroviral antigen-positive lymphocytes, but not retroviral antigen-negative lymphocytes, induced syncytia upon cocultivation with 8C cells. Peripheral blood lymphocytes isolated from patients with chronic lymphocytic leukemia of T-cell origin or Sézary syndrome or from normal adults and lymph node cells from a patient with immunoblastic lymphadenopathy-like T-cell lymphoma did not express the retroviral antigen even after cultivation in vitro and did not induce syncytia upon cocultivation with 8C cells. Thus, there was complete agreement between the presence of the retroviral antigen in established T-cell lines or freshly isolated peripheral blood lymphocytes and their ability to induce syncytia. Syncytia formation was enhanced 5- to 20-fold by the presence of Polybrene and inhibited by addition of plasma of ATL patients to the cocultures. Syncytia were detected within 4 hr on cocultivation of 8C cells with the retroviral antigen-positive T-cells, indicating that most syncytia were formed by early polykaryocytosis. After cocultivation, a clone of 8C cells that harbored the ATL virus genome and had syncytia-inducing activity was isolated. These findings indicate that the retrovirus associated with ATL has syncytia-inducing activity. Syncytia induction assay using 8C cells will be useful for detection and characterization of human retrovirus associated with T-cell malignancies.     

Detection of endogenous macrophage colony-stimulating factor (M-CSF) in human blood

We have detected endogenous human macrophage colony-stimulating factor (M-CSF) in blood of normal individuals, using a novel RIA that accurately measures M-CSF concentrations as low as 60 U/ml (1.2 ng/ml) in the presence of serum proteins. The RIA uses an antibody to highly purified recombinant human M-CSF and is calibrated to a mouse bone marrow colony-forming assay. Ten samples of normal human blood plasma contained an average 118 +/- 9 U/ml of M-CSF, and similar concentrations were detected in serum prepared from the same individuals. RIA-positive samples contained biologically active M-CSF, as determined in a colony assay performed on mouse bone marrow cells. The M-CSF biological activity was removed by specific immune precipitation and inhibited by addition of M-CSF antibody. Physical characterization of plasma M-CSF was done by immunoblotting after partial purification on controlled pore glass and immunoaffinity chromatography. The major reduced protein species of plasma M-CSF had an apparent molecular weight of about 24 kd, and minor species of 30, 45, and 60-70 kd were also present. The RIA results on ten normal individuals suggest that endogenous circulating M-CSF is present at a low but detectable concentration. This RIA can be used to measure M-CSF in clinical samples that contain serum proteins and other growth factors that may interfere with accurate bioassay determinations.     

Heterologous expression of specific K+ channels in T lymphocytes: functional consequences for volume regulation.

It has been postulated that the K+ channel isoform Kv1.3 plays a role in regulatory volume decrease (RVD) in response to hypotonic shock. We show that a mouse cytotoxic T-lymphocyte line, CTLL-2, is devoid of voltage-dependent K+ channels and is unable to volume regulate. Transient transfection of these cells with Kv1.3 reconstitutes their ability to volume regulate. As predicted by our model, this ability depends critically on volume-induced changes in membrane potential and the isoform of the K+ channel used. When the cells were transfected with Kv3.1, an isoform believed to be expressed in a specific subclass of mouse thymocytes, the CTLL-2 cells did not show RVD. The difference in the ability of the two isoforms to confer the capacity for RVD is expected from differences in the voltage dependence of activation of the channels, according to our proposed model for RVD. The experimental approach that we use, transient transfection and panning to select positive transfectants, is highly effective; it has a > 95% efficiency. This method, and this cell line, may be important tools in studying lymphocyte K+ channels and their function in situ.     

T lymphocytes expressing human Ia-like antigens in infectious mononucleosis (IM)

In six patients with Epstein-Barr virus (EBV) induced infectious mononucleosis (IM) and in two patients with IM-like syndrome, peripheral blood lymphocytes in the acute and convalescent phase were tested for human la-like antigens as well as other cell surface markers. The major population of T lymphocytes in the acute phase showed la-like antigens, as detected by indirect immunofluorescence with heteroantisera, and the number of la-like antigen-positive T lymphocytes decreased with convalescence. The crossabsorption study indicated that the amount of la-like antigen on the surface of IM T cells was less than that of Raji cells.