[show abstract][hide abstract] ABSTRACT: Human papillomavirus (HPV) E6 proteins of high-risk alpha types target a select group of PSD95/DLG1/ZO1 (PDZ) domain-containing proteins by using a C-terminal PDZ-binding motif (PBM); an interaction that can be negatively regulated by phosphorylation of the E6 PBM by protein kinase A (PKA). Here, we have mutated the canonical PKA recognition motif that partially overlaps with the E6 PBM in the HPV18 genome (E6153PKA), and compared the affect of this mutation on the HPVl8 life cycle in primary keratinocytes with the wild type genome, and with a second mutant genome that lacks the E6 PBM (E6ΔPDZ). Loss of PKA recognition of E6 was associated with increased growth of the genome-containing cells relative to cells carrying the wild type genome, and upon stratification, a more hyperplastic phenotype, with an increase in the number of S phase competent cells in the upper suprabasal layers, whilst the opposite was seen with the E6ΔPDZ genome. Moreover, the growth of wild type genome-containing cells was sensitive to changes in PKA activity and these changes were associated with increased phosphorylation of the E6 PBM. In marked contrast to E6ΔPDZ genomes, the E6153PKA mutation exhibited no deleterious effects on viral genome amplification or expression of late proteins. Our data suggests that the E6 PBM function is differentially regulated by phosphorylation in the HPV18 life cycle. We speculate that perturbation of protein kinase signalling pathways could lead to changes in E6 PBM function, which in turn could have bearing on tumour promotion and progression.
[show abstract][hide abstract] ABSTRACT: Discs-large (DLG) is a multi-PDZ domain-containing protein that belongs to the family of molecular scaffolding proteins known as membrane guanylate kinases or MAGUKs. DLG is a component of the Scribble polarity complex and genetic analyses of DLG in Drosophila have identified a role for the protein in several key biological processes including the regulation of apico-basal polarity of epithelial cells, as well as other polarity processes such as asymmetric cell division and cell invasion. Disturbance of DLG function leads to uncontrolled epithelial cell proliferation and neoplastic transformation, thereby defining DLG as a potential tumour suppressor. However, whether mammalian homologues of DLG (DLG1, DLG2, DLG3 and DLG4) also possess tumour suppressor functions is not known. In this minireview, we focus on the biological functions of DLG1 in human epithelial cells and on how the function of this MAGUK relates to its intracellular location. We examine some of the evidence that implies that DLG has both tumour suppressor and, paradoxically, oncogenic functions depending upon the precise cellular context.
[show abstract][hide abstract] ABSTRACT: Gap junctions, composed of Cxs (connexins), allow direct intercellular communication. Gap junctions are often lost during the development of malignancy, although the processes behind this are not fully understood. Cx43 is a widely expressed Cx with a long cytoplasmic C-terminal tail that contains several potential protein-interaction domains. Previously, in a model of cervical carcinogenesis, we showed that the loss of gap junctional communication correlated with relocalization of Cx43 to the cytoplasm late in tumorigenesis. In the present study, we demonstrate a similar pattern of altered expression for the hDlg (human discs large) MAGUK (membrane-associated guanylate kinase) family tumour suppressor protein in cervical tumour cells, with partial co-localization of Cx43 and hDlg in an endosomal/lysosomal compartment. Relocalization of these proteins is not due to a general disruption of cell membrane integrity or Cx targeting. Cx43 (via its C-terminus) and hDlg interact directly in vitro and can form a complex in cells. This novel interaction requires the N- and C-termini of hDlg. hDlg is not required for Cx43 internalization in W12GPXY cells. Instead, hDlg appears to have a role in maintaining a cytoplasmic pool of Cx43. These results demonstrate that hDlg is a physiologically relevant regulator of Cx43 in transformed epithelial cells.
[show abstract][hide abstract] ABSTRACT: The contribution of early virus-induced epigenetic changes to human papillomavirus (HPV)-associated carcinogenesis is poorly understood. Using genome-wide methylation array profiling and a cell-based model, which supports replication of HPV episomes, we found that transfection of primary human foreskin keratinocytes with episomal forms of high-risk HPV types was followed by upregulation of the DNA methyltransferases, DNMT1 and DNMT3B, and changes in the methylation status of cellular genes many of which are reported to be differentially methylated in cervical neoplasia. HPV16- and HPV18-associated changes were not randomly distributed across the genome, but clustered at specific chromosomal locations which mapped on to known HPV integration sites and to chromosomal regions lost and gained in high-grade cervical neoplasia. Methylation changes were directed in part by the same cis-acting factors that appear to direct methylation changes in cancer, the presence of a bivalent chromatin mark in human embryonic stem cells and promoter CpG content; these associations explain much of the ontological profile of genes found to have increased methylation following HPV16 transfection. We were also able to show, using sequential samples from a cohort of young women with incident HPV16 infections, that the detection in cervical samples of methylated forms of the tumour suppressor gene, RARB, often parallels the natural history of cervical HPV infection. Our findings suggest that further investigation of the distribution and determinants of early virus-induced epigenetic reprogramming will provide important insights into the pathogenesis of virus-associated malignancy.
[show abstract][hide abstract] ABSTRACT: The components of the Scrib/Dlg tumour suppressor complex have complementary roles in Drosophila and loss of both proteins is a common event in many different human tumours. However no studies have directly addressed the respective contributions of loss of hScrib and hDlg in the same human cell background to cellular phenotypes associated with cell transformation. In human HaCaT keratinocytes we show that removal of hScrib greatly reduces cell-cell contact and cell-matrix interactions, and promotes an invasive phenotype. Conversely, in cells lacking hDlg1 cell-cell contacts are maintained and there are decreases in both cell growth and invasion. However, hDlg-depleted cells show increased resistance to a specialized form of apoptosis known as anoikis, to which cells lacking hScrib are highly susceptible. Thus whilst it has been widely assumed that hScrib and hDlg have complementary roles, these studies in fact demonstrate that hScrib and hDlg1 have distinct and opposing functions in human keratinocytes.
PLoS ONE 01/2012; 7(7):e40279. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: The G2/M arrest function of human papillomavirus (HPV) E4 proteins is hypothesized to be necessary for viral genome amplification. Full-length HPV18 E1^E4 protein is essential for efficient viral genome amplification. Here we identify key determinants within a CDK-bipartite consensus recognition motif in HPV18 E1^E4 that are critical for association with active CDK-cyclin complexes and in vitro phosphorylation at the predicted CDK phosphorylation site (threonine 23). The optimal cyclin-binding sequence ((43)RRLL(46)) within this E4 motif is required for G2/M arrest of primary keratinocytes and correlates with cytoplasmic retention of cyclin B1, but not cyclin A. Disruption of this motif in the E4 ORF of HPV18 genomes, and the subsequent generation of stable cell lines in primary keratinocytes revealed that this motif was not essential for viral genome amplification or L1 capsid protein induction. We conclude that the HPV18 E4 G2/M arrest function does not play a role in early vegetative events.
[show abstract][hide abstract] ABSTRACT: It has been suggested that in women who test positive for high-risk human papillomavirus (HPV) types, viral load can distinguish women who are at increased risk of cervical neoplasia from those who are not.
Quantitative PCR (qPCR) was used to measure HPV copy number in serial samples taken from 60 and 58 young women previously found to have incident cervical HPV16 or HPV18 infections, respectively, using GP5+/GP6+ primers; women provided at least three samples for qPCR testing, at least one of which was positive.
A 10-fold increase in HPV16 or HPV18 copy number was associated with a modestly increased risk of acquiring a cytologic abnormality [HPV16: hazards ratio, 1.76 (95% confidence interval, 1.38-2.25); HPV18: hazards ratio, 1.59 (95% confidence interval, 1.25-2.03)]. However, in most women, copy number increased during follow-up, before decreasing again. In women with a HPV16 infection, the median copy number per 1,000 cells was 7.7 in their first qPCR HPV-positive sample, 1,237 in the sample yielding the maximum copy number, and 7.8 in their last qPCR HPV-positive sample; corresponding copy numbers for women with HPV18 infection were 2.3, 87, and 2.4. Maximum HPV16 and HPV18 copy number did not differ significantly between women who acquired an incident cervical cytologic abnormality and those who did not.
Whereas large relative increases in copy number are associated with an increased risk of abnormality, a single measurement of viral load made at an indeterminate point during the natural history of HPV infection does not reliably predict the risk of acquiring cervical neoplasia. Therefore, a single measure of HPV viral load cannot be considered a clinically useful biomarker.
[show abstract][hide abstract] ABSTRACT: Integration of high-risk human papillomavirus (HPV) types into the host-cell genome disrupts the HPV regulatory E2 protein, resulting in a loss of negative feedback control of viral oncogene expression; this disruption has been considered a critical event in the pathogenesis of cervical neoplasia, and a potential biomarker of progressive disease. However, using serial samples taken from a cohort of young women who were recruited soon after they first had sexual intercourse, we show that disruption of the E2 gene is a common and early event in the natural history of incident cervical HPV infections. The E2 gene was significantly more likely to be disrupted in women who tested positive for HPV18 in their baseline sample than in those who tested positive for HPV16 [26% versus 58%; relative risk, 2.26; 95% confidence interval (CI), 1.38-3.71; chi(2), 9.23; 1 degree of freedom (df); P = 0.002]. Among women with an intact E2 gene in their baseline sample, the median time to first detection of E2 disruption was also shorter for those who tested positive for HPV18 than HPV16 (5.7 versus 10.9 months; hazards ratio, 1.93; 95% CI, 0.84-4.44; chi(2), 2.49; 1 df; P = 0.11). This tendency for HPV18 to integrate early, coupled with the substantial reduction in viral load in HPV18-positive samples in which E2 is disrupted, may explain why HPV18-associated disease is often reported to be characterized by minor cytologic changes, which underestimate the severity of the underlying histologic abnormality.
Cancer Research 05/2009; 69(9):3828-32. · 8.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: Productive infections by human papillomaviruses (HPVs) are restricted to nondividing, differentiated keratinocytes. HPV early proteins E6 and E7 deregulate cell cycle progression and activate the host cell DNA replication machinery in these cells, changes essential for virus synthesis. Productive virus replication is accompanied by abundant expression of the HPV E4 protein. Expression of HPV1 E4 in cells is known to activate cell cycle checkpoints, inhibiting G(2)-to-M transition of the cell cycle and also suppressing entry of cells into S phase. We report here that the HPV1 E4 protein, in the presence of a soluble form of the replication-licensing factor (RLF) Cdc6, inhibits initiation of cellular DNA replication in a mammalian cell-free DNA replication system. Chromatin-binding studies show that E4 blocks replication initiation in vitro by preventing loading of the RLFs Mcm2 and Mcm7 onto chromatin. HPV1 E4-mediated replication inhibition in vitro and suppression of entry of HPV1 E4-expressing cells into S phase are both abrogated upon alanine replacement of arginine 45 in the full-length E4 protein (E1;E4), implying that these two HPV1 E4 functions are linked. We hypothesize that HPV1 E4 inhibits competing host cell DNA synthesis in replication-activated suprabasal keratinocytes by suppressing licensing of cellular replication origins, thus modifying the phenotype of the infected cell in favor of viral genome amplification.
Journal of Virology 09/2008; 82(18):9056-64. · 5.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: Activation of the productive phase of the human papillomavirus (HPV) life cycle in differentiated keratinocytes is coincident with high-level expression of E1E4 protein. To determine the role of E1E4 in the HPV replication cycle, we constructed HPV18 mutant genomes in which expression of the full-length E1E4 protein was abrogated. Undifferentiated keratinocytes containing mutant genomes showed enhanced proliferation when compared to cells containing wildtype genomes, but there were no differences in maintenance of viral episomes. Following differentiation, cells with mutant genomes exhibited reduced levels of viral DNA amplification and late gene expression, compared to wildtype genome-containing cells. This indicates that HPV18 E1E4 plays an important role in regulating HPV late functions, and it may also function in the early phase of the replication cycle. Our finding that full-length HPV18 E1E4 protein plays a significant role in promoting viral genome amplification concurs with a similar report with HPV31, but is in contrast to an HPV11 study where viral DNA amplification was not dependent on full-length E1E4 expression, and to HPV16 where only C-terminal truncations in E1E4 abrogated vegetative genome replication. This suggests that type-specific differences exist between various E1E4 proteins.
[show abstract][hide abstract] ABSTRACT: Human papillomavirus (HPV) infections of the squamous epithelium are associated with high-level expression of the E1circumflexE4 protein during the productive phase of infection. However, the precise mechanisms of how E1circumflexE4 contributes to the replication cycle of the virus are poorly understood. Here, we show that the serine-arginine (SR)-specific protein kinase SRPK1 is a novel binding partner of HPV type 1 (HPV1) E1circumflexE4. We map critical residues within an arginine-rich domain of HPV1 E1circumflexE4, and in a region known to facilitate E1circumflexE4 oligomerization, that are requisite for SRPK1 binding. In vitro kinase assays show that SRPK1 binding is associated with phosphorylation of an HPV1 E1circumflexE4 polypeptide and modulates autophosphorylation of the kinase. We show that SRPK1 is sequestered into E4 inclusion bodies in terminally differentiated cells within HPV1 warts and that colocalization between E1circumflexE4 and SRPK1 is not dependent on additional HPV1 factors. Moreover, we also identify SRPK1 binding of E1circumflexE4 proteins of HPV16 and HPV18. Our findings indicate that SRPK1 binding is a conserved function of E1circumflexE4 proteins of diverse virus types. SRPK1 influences important biochemical processes within the cell, including nuclear organization and RNA metabolism. While phosphorylation of HPV1 E4 by SRPK1 may directly influence HPV1 E4 function during the infectious cycle, the modulation and sequestration of SRPK1 by E1circumflexE4 may affect the ability of SRPK1 to phosphorylate its cellular targets, thereby facilitating the productive phase of the HPV replication cycle.
Journal of Virology 07/2007; 81(11):5437-48. · 5.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: The infectious cycle of human papillomavirus type 1 (HPV1) is accompanied by abundant expression of the full-length E1;E4 protein (17-kDa) and smaller E4 polypeptides (16-, 11-, and 10-kDa) that arise by sequential loss of N-terminal E1;E4 sequences. HPV1 E4 inhibits G(2)-to-M transition of the cell cycle. Here, we show that HPV1 E4 proteins mediate inhibition of cell division by more than one mechanism. Cells arrested by coexpression of E1;E4 (E4-17K) and a truncated protein equivalent to the 16-kDa species (E4-16K) contain inactive cyclin B1-cdk1 complexes. Inactivation of cdk1 is through inhibitory Tyr(15) phosphorylation, with cells containing elevated levels of Wee1, the kinase responsible for inhibitory cdk1 phosphorylation. Consistent with these findings, overexpression of Wee1 enhanced the extent to which E4-17K/16K-expressing cells arrest in G(2), indicating that maintenance of Wee1 activity is necessary for inhibition of cell division induced by coexpression of the two E4 proteins. Moreover, we have determined that depletion of Wee1 by small interfering RNA (siRNA) alleviates the G(2) block imposed by E4-17K/16K. In contrast however, maintenance of Wee1 activity is not necessary for G(2)-to-M inhibition mediated by E4-16K alone, as overexpression or depletion of Wee1 does not influence the G(2) arrest function of E4-16K. Cells arrested by E4-16K expression contain low levels of active cyclin B1-cdk1 complexes. We hypothesize that differential expression of HPV1 E4 proteins during the viral life cycle determines the host cell cycle status. Different mechanisms of inhibition of G(2)-to-M transition reinforce the supposition that distinct E4 functions are important for HPV replication.
Journal of Virology 09/2006; 80(15):7416-26. · 5.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: Posttranslational modification-oligomerization, phosphorylation, and proteolytic cleavage-of the human papillomavirus (HPV) E4 protein occurs as the infected keratinocytes migrate up through the suprabasal wart layers. It has been postulated that these events modify E4 function during the virus life cycle. In HPV type 1 (HPV1)-induced warts, N-terminal sequences are progressively cleaved from the full-length E4 protein (E1(wedge)E4) of 17 kDa to produce a series of polypeptides of 16, 11 and 10 kDa. Here, we have shown that in human keratinocytes, a truncated protein (E4-16K), equivalent to the 16-kDa species, mediated a G(2) arrest in the cell cycle that was dependent on a threonine amino acid in a proline-rich domain of the protein. Reconstitution of cyclin B1 expression in E4-16K cells reversed the G(2) arrest. Expression of E4-16K also induced chromosomal rereplication, and this was associated with aberrant nuclear morphology. Perturbation of the mitotic cell cycle was a biological activity specific to the truncated protein. However, coexpression of the full-length E1(wedge)E4 protein and the truncated E4-16K protein inhibited normal cellular proliferation and cellular DNA rereplication but did not prevent cells from arresting in G(2). Our findings provide the first evidence to support the hypothesis that proteolytic cleavage of the E1(wedge)E4 protein modifies its function. Also, different forms of the HPV1 E4 protein cooperate to negatively influence keratinocyte proliferation. We predict that these distinct biological activities of E4 act to support efficient amplification of the viral genome in suprabasal keratinocytes.
Journal of Virology 01/2005; 78(24):13920-33. · 5.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: Human papillomavirus (HPV)-associated vulvar intraepithelial neoplasia (VIN) has serious sequelae for the sufferer. Current treatments are associated with poor response and high relapse rates. The development of HPV-specific T cell immunotherapies offers a new approach to treatment. This will require a detailed understanding of the spectrum of T cell responses induced by HPV antigens, and how effectively viral antigens can be accessed by the immune system. We have investigated the frequency and spectrum of HPV16-specific CD8+ T cell responses to three HPV16 antigens in 9 women with high grade VIN (VIN3). CD4-depleted populations of responder cells were screened against overlapping 30-35mer peptides covering the sequences of HPV16 E6, E7 and E4 using ELISPOT assays of IFN-gamma release. We demonstrated CD8+ T cell reactivity to one or more of the proteins in 6 of 9 patient samples. All 6 of these responders recognised peptides covering the E7 protein, 3 of 9 women responded to E6 peptides, but no reactivity was seen to E4. Our results suggest that HPV16-specific cytotoxic T cells (CTLs) are relatively common in women with persistent VIN3. The HPV-specific CTL response, however, seems to be ineffective. There is some evidence that there are problems associated with the processing and presentation of HPV antigens by the infected vulvar epithelium. It will be crucial to address this in the design of any T cell based therapy for HPV-associated VIN and vulval cancer.
International Journal of Cancer 04/2004; 108(6):857-62. · 6.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: Human papillomavirus E6 oncoproteins induce the proteasomal degradation of several multi-PDZ (PSD95/Dlg/ZO-1) domain-containing proteins such as the human homologue of Drosophila discs large. Binding to PDZ domain-containing proteins is mediated by a PDZ-binding motif contained within the C-terminus of E6. The ability of E6 proteins to induce degradation of PDZ domain-containing proteins correlates with their oncogenic potential. Here we examined the biological effect of this region of the human papillomavirus type 18 E6 oncoprotein on keratinocyte morphology. Our results show that in simian virus 40-immortalized human keratinocytes, stable expression of E6 correlated with the induction of an exaggerated mesenchymal-like morphology and actin cytoskeleton disorganization compared with parental cells. The altered phenotype was accentuated in cells expressing an E6 protein containing a mutation (Arg153Leu) within a protein kinase A recognition motif that abrogates protein kinase A's negative regulation of the activity of the PDZ-binding domain. The E6-induced changes indicated an epithelial-mesenchymal transition and were supported by the finding that E6-expressing cells contained vimentin. Changes to the epithelial phenotype of cells expressing a mutant E6 protein (Thr156Glu) that is unable to degrade discs large was significantly less marked, although they did show evidence of epithelial-mesenchymal transition. These observations imply that the activity of the E6 PDZ-binding motif contributes only to a part of the transition. Further analysis of the E6 cell lines showed a decrease in adherens junction and desmosome formation. Cells expressing a functional PDZ-binding motif showed the greatest disruption of intercellular junction formation, but this did not correlate with a decrease in total cellular levels of the individual components of adhesion junctions. This suggests that the activity of the PDZ-binding motif may have influenced either the assembly or integrity of functional adhesion complexes. An E6-mediated decrease in peripheral membrane levels of PDZ proteins like discs large could be the basis for the enhanced morphological transformation of immortalized keratinocytes.
[show abstract][hide abstract] ABSTRACT: Drosophila discs large (Dlg) has been shown to be an essential regulator of cell polarity and attachment, and is classified as a potential tumour suppressor in higher eukaryotes. Human Dlg is expressed in epithelial cells at sites of cell-cell contact and acts as a negative regulator of cell growth. Although hDlg has been shown to be phosphorylated during mitosis, little is known about its activity during this stage of the cell cycle. To investigate this further we have analysed in detail the pattern of hDlg expression during mitotic cell division. In early mitosis there is a marked increase in membrane-bound hDlg which is then retained throughout mitosis, while during cytokinesis, there is a specific concentration of hDlg at the midbody. Using mutants of Dlg we show that this is mediated by sequences in the carboxy terminal region of Dlg, but it does not require the SH3 or PDZ domains, and is independent of binding to protein 4.1. Finally, using a mutant of Dlg that consists of just this carboxy terminal region of the protein, we show that it can compete with endogenous hDlg for midbody accumulation, and this mutant also gives rise to altered cell growth. We conclude that localisation of Dlg to the midbody indicates a role for Dlg at this critical point in cytokinesis.
Experimental Cell Research 11/2003; 290(2):265-74. · 3.56 Impact Factor
[show abstract][hide abstract] ABSTRACT: Human papillomavirus type 1 (HPV1) E4 protein is associated with cytoplasmic and nuclear inclusions in productively infected keratinocytes. Here we have used transient expression of HPV1 E4 (also known as E1E4) protein in keratinocytes to reproduce formation of E4 inclusions. Immunofluorescence analysis showed that progressive formation of inclusions correlated with diminished colocalization between E4 and keratin intermediate filaments (IFs). Our results support a model in which the HPV1 E4-keratin IF association is transient, occurring only at an early stage of inclusion formation. We also demonstrate that E4 induces relocation of the promyelocytic leukemia protein (PML) from multiple intranuclear speckles (ND10 bodies) to the periphery of nuclear E4 inclusions and that this activity is specific to full-length E4 protein. Analysis of HPV1-induced warts demonstrated that nuclear PML-E4 inclusions were present in productively infected keratinocytes, indicating that reorganization of PML occurs during the virus's replication cycle. It has been suggested that ND10 bodies are the sites for papillomavirus genome replication and virion assembly. Our finding that E4 induces reorganization of ND10 bodies in vitro and in vivo is further strong evidence that these domains play an important role in the papillomavirus life cycle. This study indicates that HPV1 is analogous to other DNA viruses that disrupt or reorganize ND10 domains, possibly to increase efficiency of virus infection. We hypothesize that HPV1 E4-induced reorganization of PML is necessary for efficient replication of the virus during the virus-producing phase.
Journal of Virology 02/2003; 77(1):673-84. · 5.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Drosophila tumour suppressor discs large (Dlg) is a cell-junction localized protein that is required for the maintenance of epithelial cyto-architecture and the negative control of cell proliferation. The mammalian homologue is likely to have a similar mode of action, and therefore functional perturbation of this protein may be linked to the development of epithelial-derived cancers. The finding that several unrelated viral oncoproteins, including the E6 protein of oncogenic human papillomaviruses, bind to the human homologue of Dlg (hDlg) supports this proposition. Employing immunohistochemistry, we show that in uterine cervical squamous epithelia, prominent localization of hDlg at sites of intercellular contact occurs in cells that have left the proliferating basal cell layers and begun maturation. The presence of hDlg at sites of cell:cell contact diminishes, whilst intracellular cytoplasmic levels increase significantly in high-grade, but not low-grade, cervical neoplasias. In invasive squamous cell carcinomas, total cellular hDlg levels are greatly reduced. Our data suggest that loss of hDlg at sites of intercellular contact may be an important step in the development of epithelial cancers.
[show abstract][hide abstract] ABSTRACT: Human papillomavirus (HPV) antigens are expressed in epithelial cells at different stages of differentiation, and this may affect how they are handled by the immune system. We assessed the relative immunogenicities of four different HPV type 1 proteins: E6 and E7, which are made early in basal or parabasal cells; E4, which is made suprabasally in differentiating cells; and L1, a late protein which appears in the highly differentiated upper spinous layers. Pools of 15-mer peptides covering the primary sequences of all four proteins were used to screen 15 normal donors in enzyme-linked immunospot assays of gamma interferon release for both CD4(+)- and CD8(+)-T-cell reactivities. CD8(+)-T-cell responses were detected to the L1 protein in 7 of the 15 samples examined. No responses to E6, E7, or E4 were detected. CD4(+)-T-cell reactivities were again detected in 7 of the 15 donors. A broader spectrum of responses to E6 (three of seven), E4 (six of seven), and L1 (three of seven) was apparent, but there was no reactivity to E7. The predominant CD4(+) response was to E4. Reactivities were seen in some cases to corresponding regions on other common HPV types but were probably due to a multiple infection rather than to a cross-reaction. Antibodies to HPV1 virus-like particles were detected in 12 of the 15 (80%) donors, but antibody status did not correlate with T-cell reactivity. The differences in the relative immunogenicities of the four proteins revealed in this study are discussed in relation to how they may be processed and presented to the immune system by differentiating epithelial cells.
Journal of Virology 07/2002; 76(12):6027-36. · 5.08 Impact Factor