Detection of individual virus-infected cells by filter in situ hybridization

Regulation of susceptibility and cell surface receptor for the B-lymphotropic papovavirus by N glycosylation

The host range of the B-lymphotropic papovavirus (LPV) in cultured human cells is limited to a few B-lymphoma-derived cell lines. The constitutively expressed cell surface receptor for the virus is a major determinant restricting the LPV host range (G. Haun, O. T. Keppler, C. T. Bock, M. Herrmann, H. Zentgraf, and M. Pawlita, J. Virol. 67:7482-7492, 1993). Here we show that human B-lymphoma cells with low-level susceptibility are rendered highly susceptible to LPV infection by pretreatment with the N glycosylation inhibitor tunicamycin but remain nonsusceptible to infection by the related polyomavirus simian virus 40. Among the selective N glycosylation processing inhibitors, deoxymannojirimycin, but not deoxynojirimycin, swainsonine, or castanospermine, could mimic the effect of tunicamycin. Tunicamycin treatment also induced a drastic enhancement of the cells' LPV-binding capacity, indicating that the induction of LPV susceptibility might be mediated by an increase in the number of functional cell surface receptors and/or by increased receptor affinity. Sialidase sensitivity of the tunicamycin-induced LPV receptor showed that oligosaccharides carrying terminal sialic acids are necessary for binding and are likely to be O linked. The constitutive LPV receptor is also sialic acid dependent, which points to a possible identity with the sialic acid-dependent tunicamycin-induced LPV receptor. We conclude that removal or modification of certain N-linked oligosaccharides in human B-lymphoma cells can enhance expression or functional activity of the sialylated LPV receptor.

The cell surface receptor is a major determinant restricting the host range of the B-lymphotropic papovavirus

The B-lymphotropic papovavirus (LPV) productively infects only a subset of human B-lymphoma-derived cell lines while transfection of the viral genome yields infectious viral particles in a much wider variety of human hematopoietic cell lines. We have analyzed the contribution of a putative LPV receptor on the cell surface of B-cell lines in restricting the virus host range. In order to establish a quantitative virus binding assay for LPV, infectious virus particles were highly purified by metrizamide equilibrium density centrifugation and used as immunogens to raise seven mouse monoclonal antibodies specific for LPV VP1. Virus particle binding was quantitated in an indirect, nonradioactive assay with an LPV VP1-specific enzyme-linked immunosorbent assay. Binding of LPV particles to permissive human B-lymphoma cell line BJA-B occurred within minutes. Kinetics and capacity of binding were similar at 4 and 37 degrees C. A BJA-B cell was estimated to bind approximately 600 virus particles at conditions under which 50% of the administered virus was bound. The sialidase and trypsin sensitivities of the cellular virus binding moiety show that sialylated and proteinaceous components are necessary components of the LPV receptor on BJA-B cells. Despite a high binding capacity of BJA-B cells for simian virus 40, LPV binding was not significantly affected by a 20-fold excess of simian virus 40 particles, indicating that these related polyomaviruses do not bind to the same receptor on BJA-B cells. Reduction of LPV binding to sialidase-pretreated BJA-B cells was accompanied by a similar reduction of infection, indicating that virus binding may be a limiting factor in the LPV replicative cycle. The two highly LPV-permissive human B-lymphoma cell lines BJA-B and Namalwa displayed high virus binding whereas low and nonpermissive hematopoietic cell lines showed reduced or undetectable virus binding. We conclude that the inability of LPV particles to productively infect the nonpermissive human hematopoietic cell lines analyzed is probably due to the absence or insufficient expression of a functional cell surface receptor.

Sequence variants of human papillomavirus type 16 in clinical samples permit verification and extension of epidemiological studies and construction of a phylogenetic tree

Genomic variability between different viral isolates provides a powerful epidemiological tool for verifying ultrasensitive diagnostic procedures, understanding infectious pathways in individuals and human populations, and studying viral evolution. The potential of this approach has not yet been exploited for the diagnosis of human papillomaviruses (HPVs) like HPV type 16 (HPV-16), which are involved in genital cancer. Toward this end, we amplified by polymerase chain reaction, cloned, and sequenced a 364-bp noncoding segment of the HPV-16 genome from cell lines, cervical biopsy specimens, and cervical smears. The HPV-16 genomes in the cell lines SiHa and CaSki showed an identical point mutation, and in the SiHa cell line it had an additional 38-bp deletion. Only 4 of 22 cervical lesions biopsied from patients at several hospitals in Singapore contained HPV-16 DNA with the prototype sequence, while the DNAs of the other 18 cervical lesions differed by 1 to 10 mutations. This excludes contaminations with cloned HPV-16 DNA as the source of this DNA. To test whether this diversity was a geographic idiosyncrasy, we analyzed 25 cervical biopsy specimens from Brazil. Eight of these contained the prototype sequence, while 17 were mutated. Altogether, 11 genomic variants were found in the Singaporean samples and 12 genomic variants were found in the Brazilian samples, and only 5 of these occurred identically in both cohorts. All variants could be connected to form a phylogenetic tree, with some branches being specific for each cohort. This suggests that the variants did not originate over a short period in the individual patient but, rather, evolved consecutively while spreading throughout humankind.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of Epstein-Barr virus-DNA in tongue epithelium of human immunodeficiency virus-infected patients

Oral hairy leukoplakia is a lesion on the lateral part of the tongue that contains replicating Epstein-Barr virus (EBV) and presages progression from human immunodeficiency virus (HIV) infection to AIDS. To clarify the role of EBV in the development of the lesions, we used filter in situ DNA hybridization to determine the prevalence of EBV and of human papillomavirus (HPV) in epithelial cells obtained on swabs from the tongue of HIV-infected patients who had hairy leukoplakia, HIV-infected patients who did not have hairy leukoplakia, and healthy uninfected control persons. In samples collected from the 35 uninfected control persons, EBV DNA could not be detected except at low concentrations in three people. In contrast, all but one of the samples from 11 HIV-infected patients who had hairy leukoplakia contained EBV DNA. Of greatest interest, in 19 of 32 HIV-infected patients who had no signs of hairy leukoplakia, EBV DNA was also detected on the epithelium of the tongue. DNA filter in situ hybridization for the detection of HPV serotypes 6, 11, 16, and 18 in all cases yielded negative results. Statistical analysis showed that the presence of EBV DNA was significantly correlated with the clinical status of the HIV-infected persons, as determined by Walter Reed staging classification, whereas hairy leukoplakia was not. It is concluded that detection of EBV DNA in oral epithelium may be an earlier and more powerful predictor of progression to AIDS than is hairy leukoplakia.

Amplification of bovine papillomavirus DNA by N-methyl-N'-nitro-N-nitrosoguanidine, ultraviolet irradiation, or infection with herpes simplex virus

Treatment with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or irradiation with ultraviolet light (uv254 nm) induces amplification of integrated as well as episomal sequences of bovine papillomavirus (BPV) type 1 DNA in BPV-1-transformed mouse C127 cells (i.e., ID13 cells). This is shown by filter in situ hybridization and Southern blot analysis of cellular DNA. Similarly, infection of ID13 cells with herpes simplex virus (HSV) type 1 which has been shown to be mutagenic for host cell DNA leads to amplification of BPV DNA sequences. In contrast to this induction of DNA amplification by initiators, treatment of ID13 cells with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) does not result in increased synthesis of BPV DNA nor does TPA treatment modulate the initiator-induced DNA amplification. Similar to other cell systems infection with adeno-associated virus (AAV) type 2 inhibits BPV-1 DNA amplification irrespective of the inducing agent. In contrast to initiator-induced DNA amplification, treatment with carcinogen (MNNG) or tumor promoters or combination of MNNG and promoter of C127 cells prior to transformation by BPV-1 does not lead to an increase in the number of transformed foci. The induction of amplification of papillomavirus DNA by initiating agents possibly represents one of the mechanisms by which the observed synergism between papillomavirus infection and initiators in tumorigenesis might occur.