Differential long-term bivalent HPV vaccine cross-protection by variants in the Costa Rica HPV vaccine trial.

The AS04-adjuvanted human papillomavirus (HPV)16/18 vaccine, an L1-based vaccine, provides strong vaccine efficacy (VE) against vaccine-targeted type infections, and partial cross-protection to phylogenetically-related types, which may be affected by variant-level heterogeneity. We compared VE against incident HPV31, 33, 35, and 45 detections between lineages and SNPs in the L1 region among 2846 HPV-vaccinated and 5465 HPV-unvaccinated women through 11-years of follow-up in the Costa Rica HPV Vaccine Trial. VE was lower against HPV31-lineage-B (VE=60.7%;95%CI = 23.4%,82.8%) compared to HPV31-lineage-A (VE=94.3%;95%CI = 83.7%,100.0%) (VE-ratio = 0.64;95%CI = 0.25,0.90). Differential VE was observed at several lineage-associated HPV31-L1-SNPs, including a nonsynonymous substitution at position 6372 on the FG-loop, an important neutralization domain. For HPV35, the only SNP-level difference was at position 5939 on the DE-loop, with significant VE against nucleotide-G (VE=65.0%;95%CI = 28.0,87.8) but not for more the common nucleotide-A (VE=7.4%;95%CI = -34.1,36.7). Because of the known heterogeneity in precancer/cancer risk across cross-protected HPV genotype variants by race and region, our results of differential variant-level AS04-adjuvanted HPV16/18 vaccine efficacy has global health implications.

Analysis of cervical HPV infections among unvaccinated young adult women to inform vaccine strategies in this age group: the Costa Rica HPV Vaccine Trial.

INTRODUCTION: Human papillomavirus (HPV) vaccines protect against incident HPV infections, which cause cervical cancer. OBJECTIVES: We estimated the prevalence and incidence of HPV infections in young adult women to understand the impact of an HPV vaccination programme in this population. METHODS: We collected cervical specimens from 6322 unvaccinated women, aged 18-37 years, who participated in the Costa Rica Vaccine Trial and its long-term follow-up. Women were followed for (median) 4.8 years and had (median) 4.0 study visits. Cervical specimens were tested for the presence/absence of 25 HPV genotypes. For each age band, we estimated the percentage of women with 1+ prevalent or 1+ incident HPV infections using generalised estimating equations. We also estimated the prevalence and incidence of HPV as a function of time since first sexual intercourse (FSI). RESULTS: The model estimated HPV incident infections peaked at 28.0% (95% CI 25.3% to 30.9%) at age 20 years then steadily declined to 11.8% (95% CI 7.6% to 17.8%) at age 37 years. Incident oncogenic HPV infections (HPV16/18/31/33/35/39/45/51/52/56/58/59) peaked and then declined from 20.3% (95% CI 17.9% to 22.9%) to 7.7% (95% CI 4.4% to 13.1%); HPV16/18 declined from 6.4% (95% CI 5.1% to 8.1%) to 1.1% (95% CI 0.33% to 3.6%) and HPV31/33/45/52/58 declined from 11.0% (95% CI 9.3% to 13.1%) to 4.5% (95% CI 2.2% to 8.9%) over the same ages. The percentage of women with 1+ incident HPV of any, oncogenic, non-oncogenic and vaccine-preventable (HPV16/18, HPV31/33/45, HPV31/33/45/52/58, and HPV6/11) types peaked <1 year after FSI and steadily declined with increasing time since FSI (p for trends <0.001). We observed similar patterns for model estimated HPV prevalences. CONCLUSION: Young adult women may benefit from HPV vaccination if newly acquired vaccine-preventable oncogenic infections lead to cervical precancer and cancer. HPV vaccination targeting this population may provide additional opportunities for primary prevention. TRIAL REGISTRATION NUMBER: NCT00128661.

Performance of Cervical Screening a Decade Following HPV Vaccination: The Costa Rica Vaccine Trial.

BACKGROUND: We investigated the impact of human papillomavirus (HPV) vaccination on the performance of cytology-based and HPV-based screening for detection of cervical precancer among women vaccinated as young adults and reaching screening age. METHODS: A total of 4632 women aged 25-36 years from the Costa Rica HPV Vaccine Trial were included (2418 HPV-vaccinated as young adults and 2214 unvaccinated). We assessed the performance of cytology- and HPV-based cervical screening modalities in vaccinated and unvaccinated women to detect high-grade cervical precancers diagnosed over 4 years and the absolute risk of cumulative cervical precancers by screening results at entry. RESULTS: We detected 95 cervical intraepithelial neoplasia grade 3 or worse (52 in unvaccinated and 43 in vaccinated women). HPV16/18/31/33/45 was predominant (69%) among unvaccinated participants, and HPV35/52/58/39/51/56/59/66/68 predominated (65%) among vaccinated participants. Sensitivity and specificity of cervical screening approaches were comparable between women vaccinated as young adults and unvaccinated women. Colposcopy referral rates were lower in the vaccinated group for HPV-based screening modalities, but the positive predictive value was comparable between the 2 groups. CONCLUSIONS: Among women approaching screening ages, vaccinated as young adults, and with a history of intensive screening, the expected reduction in the positive predictive value of HPV testing, associated with dropping prevalence of HPV-associated lesions, was not observed. This is likely due to the presence of high-grade lesions associated with nonvaccine HPV types, which may be less likely to progress to cancer.

HPV16 infection decreases vaccine-induced HPV16 antibody avidity: the CVT trial.

The HPV vaccine has shown sustained efficacy and consistent stabilization of antibody levels, even after a single dose. We defined the HPV16-VLP antibody avidity patterns over 11 years among women who received one- or three doses of the bivalent HPV vaccine in the Costa Rica HPV Vaccine Trial. Absolute HPV16 avidity was lower in women who received one compared to three doses, although the patterns were similar (increased in years 2 and 3 and remained stable over the remaining 8 years). HPV16 avidity among women who were HPV16-seropositive women at HPV vaccination, a marker of natural immune response to HPV16 infection, was significantly lower than those of HPV16-seronegative women, a difference that was more pronounced among one-dose recipients. No differences in HPV16 avidity were observed by HPV18 serostatus at vaccination, confirming the specificity of the findings. Importantly, point estimates for vaccine efficacy against incident, six-month persistent HPV16 infections was similar between women who were HPV16 seronegative and seropositive at the time of initial HPV vaccination for both one-dose and three-dose participants. It is therefore likely that this lower avidity level is still sufficient to enable antibody-mediated protection. It is encouraging for long-term HPV-vaccine protection that HPV16 antibody avidity was maintained for over a decade, even after a single dose.

Seroprevalence and Determinants of Helicobacter pylori Infection in the Hispanic Community Health Study/Study of Latinos.

BACKGROUND & AIMS: Helicobacter pylori infection is the primary known risk factor for gastric cancer. Despite the global decline in H. pylori prevalence, this infection remains a major public health concern in developing areas, including Latin America. Our study aimed to determine H. pylori seroprevalence and identified its determinants among Hispanics/Latinos living in the United States (U.S.). METHODS: The Hispanic Community Health Study/Study of Latinos (HCHS/SOL) is a population-based sample of self-identified Hispanics/Latinos (n = 16,144) in four U.S. communities, aged 18 to 74 years, recruited from randomly selected households using a stratified two-stage area probability sample design based on sampling households within sampled census block groups weighted for differential response rates. Anti-H. pylori immunoglobulin G antibodies were measured by an enzyme-linked immunosorbent assay using plasma samples. We calculated adjusted seroprevalence (i.e., predicted margins) from multivariable logistic regression models. RESULTS: The overall weighted H. pylori seroprevalence was 57% among HCHS/SOL participants, with 38% and 62% seropositivity among U.S.-born and non-U.S.-born individuals, respectively. Age-adjusted prevalence varied by self-reported Hispanic/Latino background, ranging from 47% in Puerto Rican to 72% in Central American backgrounds. Adjusted H. pylori seroprevalence was higher in the following groups: older age, male sex, lower education, non-U.S. born status, smoking, greater number of missing teeth, fewer doctor visits, lower ferritin level, and hepatitis A seropositivity. CONCLUSIONS: H. pylori seroprevalence in Hispanics/Latinos remains high and differed significantly by Hispanic/Latino background. H. pylori seropositivity is strongly associated with poor socioeconomic conditions. These findings highlight the ongoing importance of this bacterial infection in the U.S.

Risk Factors for Non-Human Papillomavirus (HPV) Type 16/18 Cervical Infections and Associated Lesions Among HPV DNA-Negative Women Vaccinated Against HPV-16/18 in the Costa Rica Vaccine Trial.

BACKGROUND: Factors that lead human papillomavirus (HPV) infections to persist and progress to cancer are not fully understood. We evaluated co-factors for acquisition, persistence, and progression of non-HPV-16/18 infections among HPV-vaccinated women. METHODS: We analyzed 2153 women aged 18-25 years randomized to the HPV-vaccine arm of the Costa Rica HPV Vaccine Trial. Women were HPV DNA negative for all types at baseline and followed for approximately 11 years. Generalized estimating equation methods were used to account for correlated observations. Time-dependent factors evaluated were age, sexual behavior, marital status, hormonally related factors, number of full-term pregnancies (FTPs), smoking behavior, and baseline body mass index. RESULTS: A total of 1777 incident oncogenic non-HPV-16/18 infections were detected in 12 292 visits (average, 0.14 infections/visit). Age and sexual behavior-related variables were associated with oncogenic non-HPV-16/18 acquisition. Twenty-six percent of incident infections persisted for ≥1 year. None of the factors evaluated were statistically associated with persistence of oncogenic non-HPV-16/18 infections. Risk of progression to Cervical Intraepithelial Neoplasia grade 2 or worst (CIN2+) increased with increasing age (P for trend = .001), injectable contraceptive use (relative risk, 2.61 [95% confidence interval, 1.19-5.73] ever vs never), and increasing FTPs (P for trend = .034). CONCLUSIONS: In a cohort of HPV-16/18-vaccinated women, age and sexual behavior variables are associated with acquisition of oncogenic non-HPV-16/18 infections; no notable factors are associated with persistence of acquired infections; and age, parity, and hormonally related exposures are associated with progression to CIN2+.

Association Between Common Vaginal Infections and Cervical Non-Human Papillomavirus (HPV) 16/18 Infection in HPV-Vaccinated Women.

BACKGROUND: How vaginal infections such as bacterial vaginosis, Candida spp, and Trichomonas vaginalis affect persistence of human papillomavirus (HPV) infection is not well established. Our study aimed to evaluate the association between common vaginal infections and cervical non-HPV16/18 infection, as risk factors associated with persistence of nonvaccine HPV types will become increasingly relevant in the setting of HPV vaccination. METHODS: We performed an analysis in 2039 AS04-HPV16/18-vaccinated women enrolled in a phase II/III trial in China, who were HPV DNA negative at month 0 and 6 and had at least 1 subsequent follow-up visit. Vaginal infections were detected in liquid-based cytology according to the diagnostic criteria of the Bethesda System. Associations between vaginal infections and incident and 6-month persistent non-HPV16/18 infections in the cervix were evaluated using generalized estimating equations, adjusting for the age at initial vaccination, as well as HPV types in the persistence analysis. RESULTS: Study visits with any vaginal infection had a statistically significant increased risk of incident non-HPV16/18 infection compared to those without vaginal infections (odds ratio [OR], 1.44 [95% confidence interval {CI}, 1.09-1.92]). However, vaginal infections were not associated with 6-month persistent non-HPV16/18 infection (OR, 1.02 [95% CI, .62-1.69]). CONCLUSIONS: Our study suggests that common vaginal infections are not associated with persistence of non-HPV16/18 infection among HPV16/18-vaccinated women.

Efficacy of the bivalent HPV vaccine against HPV 16/18-associated precancer: long-term follow-up results from the Costa Rica Vaccine Trial.

BACKGROUND: Oncogenic human papillomavirus (HPV) infections cause most cases of cervical cancer. Here, we report long-term follow-up results for the Costa Rica Vaccine Trial (publicly funded and initiated before licensure of the HPV vaccines), with the aim of assessing the efficacy of the bivalent HPV vaccine for preventing HPV 16/18-associated cervical intraepithelial neoplasia grade 2 or worse (CIN2+). METHODS: Women aged 18-25 years were enrolled in a randomised, double-blind, controlled trial in Costa Rica, between June 28, 2004, and Dec 21, 2005, designed to assess the efficacy of a bivalent vaccine for the prevention of infection with HPV 16/18 and associated precancerous lesions at the cervix. Participants were randomly assigned (1:1) to receive an HPV 16/18 AS04-adjuvanted vaccine or control hepatitis A vaccine. Vaccines were administered intramuscularly in three 0·5 mL doses at 0, 1, and 6 months and participants were followed up annually for 4 years. After the blinded phase, women in the HPV vaccine group were invited to enrol in the long-term follow-up study, which extended follow-up for 7 additional years. The control group received HPV vaccine and was replaced with a new unvaccinated control group. Women were followed up every 2 years until year 11. Investigators and patients were aware of treatment allocation for the follow-up phase. At each visit, clinicians collected cervical cells from sexually active women for cytology and HPV testing. Women with abnormal cytology were referred to colposcopy, biopsy, and treatment as needed. Women with negative results at the last screening visit (year 11) exited the long-term follow-up study. The analytical cohort for vaccine efficacy included women who were HPV 16/18 DNA-negative at vaccination. The primary outcome of this analysis was defined as histopathologically confirmed CIN2+ or cervical intraepithelial neoplasia grade 3 or worse associated with HPV 16/18 cervical infection detected at colposcopy referral. We calculated vaccine efficacy by year and cumulatively. This long-term follow-up study is registered with ClinicalTrials.gov, NCT00867464. FINDINGS: 7466 women were enrolled in the Costa Rica Vaccine Trial; 3727 received the HPV vaccine and 3739 received the control vaccine. Between March 30, 2009, and July 5, 2012, 2635 women in the HPV vaccine group and 2836 women in the new unvaccinated control group were enrolled in the long-term follow-up study. 2635 women in the HPV vaccine group and 2677 women in the control group were included in the analysis cohort for years 0-4, and 2073 women from the HPV vaccine group and 2530 women from the new unvaccinated control group were included in the analysis cohort for years 7-11. Median follow-up time for the HPV group was 11·1 years (IQR 9·1-11·7), 4·6 years (4·3-5·3) for the original control group, and 6·2 years (5·5-6·9) for the new unvaccinated control group. At year 11, vaccine efficacy against incident HPV 16/18-associated CIN2+ was 100% (95% CI 89·2-100·0); 34 (1·5%) of 2233 unvaccinated women had a CIN2+ outcome compared with none of 1913 women in the HPV group. Cumulative vaccine efficacy against HPV 16/18-associated CIN2+ over the 11-year period was 97·4% (95% CI 88·0-99·6). Similar protection was observed against HPV 16/18-associated CIN3-specifically at year 11, vaccine efficacy was 100% (95% CI 78·8-100·0) and cumulative vaccine efficacy was 94·9% (73·7-99·4). During the long-term follow-up, no serious adverse events occurred that were deemed related to the HPV vaccine. The most common grade 3 or worse serious adverse events were pregnancy, puerperium, and perinatal conditions (in 255 [10%] of 2530 women in the unvaccinated control group and 201 [10%] of 2073 women in the HPV vaccine group). Four women in the unvaccinated control group and three in the HPV vaccine group died; no deaths were deemed to be related to the HPV vaccine. INTERPRETATION: The bivalent HPV vaccine has high efficacy against HPV 16/18-associated precancer for more than a decade after initial vaccination, supporting the notion that invasive cervical cancer is preventable. FUNDING: US National Cancer Institute.

Evaluation of serological assays to monitor antibody responses to single-dose HPV vaccines.

INTRODUCTION: Whether existing serological assays are sufficiently robust to measure the lower antibody levels expected following single-dose HPV vaccination is unknown. METHODS: We evaluated seven assays measuring HPV-16/18 immunological responses overall and by number of doses in 530 serum samples from participants receiving varying doses of Cervarix or Gardasil up to 36-months post-vaccination. Serum was evaluated by simplex (HPV-16 ELISA, HPV-18 ELISA), multiplex (LIA-4, VLP-MIA, M9ELISA, GST-L1), and high-throughput pseudovirion-based neutralization assays (HT-PBNA), and results were compared to the gold standard HPV-16/18 secreted alkaline phosphatase neutralization assay (SEAP-NA). Reproducibility was assessed by the coefficient of variation (CV) and intraclass correlation coefficient (ICC). Percent agreement, Pearson correlation, and weighted-kappa were used to assess validity. Determinants of seronegativity were evaluated by chi-squared test. RESULTS: HPV-16: Seropositivity range was 97.1-99.5% for single dose and 98.8-99.8% overall. CV range was 4.0-18.0% for single dose and 2.9-19.5% overall. ICC range was 0.77-0.99 for single dose and 0.74-0.99 overall. Correlation with SEAP-NA range was 0.43-0.85 for single dose and 0.51-0.90 overall. Weighted-kappa range was 0.34-0.82 for single dose and 0.45-0.84 overall. HPV-18: Seropositivity range was 63.9-94.7% for single dose and 86.2-97.9% overall. CV range was 8.1-18.2% for single dose and 4.6-18.6% overall. ICC range was 0.75-0.99 for single dose and 0.83-0.99 overall. Correlation with SEAP-NA range was 0.31-0.99 for single dose and 0.27-0.96 overall. Weighted-kappa range was 0.35-0.83 for single dose and 0.45-0.84 overall. HPV-16 seronegativity was <5% for all assays. HPV-18 seronegativity range was 5.5-17.3%. For LIA-4 and GST-L1 where the proportion of seronegativity was >10%, the strongest correlates of seronegativity were receiving a single vaccine dose and receiving Gardasil. CONCLUSIONS: These results support the utility of existing serological assays to monitor antibody responses following single-dose HPV vaccination.

Evaluation of Durability of a Single Dose of the Bivalent HPV Vaccine: The CVT Trial.

BACKGROUND: The authors investigated the durability of vaccine efficacy (VE) against human papillomavirus (HPV)16 or 18 infections and antibody response among nonrandomly assigned women who received a single dose of the bivalent HPV vaccine compared with women who received multiple doses and unvaccinated women. METHODS: HPV infections were compared between HPV16 or 18-vaccinated women aged 18 to 25 years who received one (N = 112), two (N = 62), or three (N = 1365) doses, and age- and geography-matched unvaccinated women (N = 1783) in the long-term follow-up of the Costa Rica HPV Vaccine Trial. Cervical HPV infections were measured at two study visits, approximately 9 and 11 years after initial HPV vaccination, using National Cancer Institute next-generation sequencing TypeSeq1 assay. VE and 95% confidence intervals (CIs) were estimated. HPV16 or 18 antibody levels were measured in all one- and two-dose women, and a subset of three-dose women, using a virus-like particle-based enzyme-linked immunosorbent assay (n = 448). RESULTS: Median follow-up for the HPV-vaccinated group was 11.3 years (interquartile range = 10.9-11.7 years) and did not vary by dose group. VE against prevalent HPV16 or 18 infection was 80.2% (95% CI = 70.7% to 87.0%) among three-dose, 83.8% (95% CI = 19.5% to 99.2%) among two-dose, and 82.1% (95% CI = 40.2% to 97.0%) among single-dose women. HPV16 or 18 antibody levels did not qualitatively decline between years four and 11 regardless of the number of doses given, although one-dose titers continue to be statistically significantly lower compared with two- and three-dose titers. CONCLUSION: More than a decade after HPV vaccination, single-dose VE against HPV16 or 18 infection remained high and HPV16 or 18 antibodies remained stable. A single dose of bivalent HPV vaccine may induce sufficiently durable protection that obviates the need for more doses.

Durability of Cross-Protection by Different Schedules of the Bivalent HPV Vaccine: The CVT Trial.

BACKGROUND: The Costa Rica HPV Vaccine Trial has documented cross-protection of the bivalent HPV vaccine against HPV31/33/45 up to 7 years after vaccination, even with one dose of the vaccine. However, the durability of such protection remains unknown. Here, we evaluate the efficacy of different schedules of the vaccine against HPV31/33/45 out to 11 years postvaccination, expanding to other nontargeted HPV types. METHODS: We compared the rates of HPV infection in vaccinated women with the rates in a comparable cohort of unvaccinated women. We estimated the average vaccine efficacy (VEavg) against incident infections and tested for a change in VE over time. RESULTS: Among 3-dose women, we observed statistically significant cross-protection against HPV31/33/45 (VEavg = 64.4%, 95% confidence interval [CI] = 57.7% to 70.0%). Additionally, we observed borderline, statistically significant cross-protection against HPV35 (VEavg = 23.2%, 95% CI = 0.3% to 40.8%) and HPV58 (VEavg = 21.2%, 95% CI = 4.2% to 35.3%). There was no decrease in VE over time (two-sided Ptrend > .05 for HPV31, -33, -35, -45, and -58). As a benchmark, VEavg against HPV16/18 was 82.0% (95% CI = 77.3% to 85.7%). Among 1-dose women, we observed comparable efficacy against HPV31/33/45 (VEavg = 54.4%, 95% CI = 21.0% to 73.7%). Acquisition of nonprotected HPV types was similar between vaccinated and unvaccinated women, indicating that the difference in HPV infection rates was not attributable to differential genital HPV exposure. CONCLUSIONS: Substantial cross-protection afforded by the bivalent vaccine against HPV31/33/45, and to a lesser extent, HPV35 and HPV58, was sustained and remained stable after 11 years postvaccination, reinforcing the notion that the bivalent vaccine is an effective option for protection against HPV-associated cancers.

Association between Trichomonas vaginalis and prostate cancer mortality.

We previously observed a positive association between seropositivity for the parasite Trichomonas vaginalis and risk of clinically significant prostate cancer at diagnosis. Here, we examined whether T. vaginalis seropositivity was associated with increased prostate cancer-specific or all-cause mortality among prostate cancer patients. We studied 736 men with prostate cancer from the Physicians' Health Study (PHS) and 749 men with prostate cancer from the Health Professionals Follow-Up Study (HPFS). We used Cox proportional hazards regression models to estimate multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of the association between T. vaginalis serostatus and progression to death from prostate cancer and from all causes. In PHS, 423 men died of any cause during a median follow-up of 13.8 years from the date of cancer diagnosis, among whom 131 died of prostate cancer. In HPFS, there were 287 deaths, including 77 deaths from prostate cancer, during a median follow-up of 12.8 years. We found no association between T. vaginalis serostatus and either prostate cancer mortality or all-cause mortality in either the PHS or HPFS. While previous studies suggest a possible role for T. vaginalis in the development of clinically significant prostate cancer, our findings do not support the hypothesis that T. vaginalis serostatus is associated with mortality among prostate cancer patients.

The Oncogenic Small Tumor Antigen of Merkel Cell Polyomavirus Is an Iron-Sulfur Cluster Protein That Enhances Viral DNA Replication.

UNLABELLED: Merkel cell polyomavirus (MCPyV) plays an important role in Merkel cell carcinoma (MCC). MCPyV small T (sT) antigen has emerged as the key oncogenic driver in MCC carcinogenesis. It has also been shown to promote MCPyV LT-mediated replication by stabilizing LT. The importance of MCPyV sT led us to investigate sT functions and to identify potential ways to target this protein. We discovered that MCPyV sT purified from bacteria contains iron-sulfur (Fe/S) clusters. Electron paramagnetic resonance analysis showed that MCPyV sT coordinates a [2Fe-2S] and a [4Fe-4S] cluster. We also observed phenotypic conservation of Fe/S coordination in the sTs of other polyomaviruses. Since Fe/S clusters are critical cofactors in many nucleic acid processing enzymes involved in DNA unwinding and polymerization, our results suggested the hypothesis that MCPyV sT might be directly involved in viral replication. Indeed, we demonstrated that MCPyV sT enhances LT-mediated replication in a manner that is independent of its previously reported ability to stabilize LT. MCPyV sT translocates to nuclear foci containing actively replicating viral DNA, supporting a direct role for sT in promoting viral replication. Mutations of Fe/S cluster-coordinating cysteines in MCPyV sT abolish its ability to stimulate viral replication. Moreover, treatment with cidofovir, a potent antiviral agent, robustly inhibits the sT-mediated enhancement of MCPyV replication but has little effect on the basal viral replication driven by LT alone. This finding further indicates that MCPyV sT plays a direct role in stimulating viral DNA replication and introduces cidofovir as a possible drug for controlling MCPyV infection. IMPORTANCE: MCPyV is associated with a highly aggressive form of skin cancer in humans. Epidemiological surveys for MCPyV seropositivity and sequencing analyses of healthy human skin suggest that MCPyV may represent a common component of the human skin microbial flora. However, much of the biology of the virus and its oncogenic ability remain to be investigated. In this report, we identify MCPyV sT as a novel Fe/S cluster protein and show that conserved cysteine clusters are important for sT's ability to enhance viral replication. Moreover, we show that sT sensitizes MCPyV replication to cidofovir inhibition. The discovery of Fe/S clusters in MCPyV sT opens new avenues to the study of the structure and functionality of this protein. Moreover, this study supports the notion that sT is a potential drug target for dampening MCPyV infection.

Phosphorylation of Merkel cell polyomavirus large tumor antigen at serine 816 by ATM kinase induces apoptosis in host cells.

Merkel cell carcinoma is a highly aggressive form of skin cancer. Merkel cell polyomavirus (MCV) infection and DNA integration into the host genome correlate with 80% of all Merkel cell carcinoma cases. Integration of the MCV genome frequently results in mutations in the large tumor antigen (LT), leading to expression of a truncated LT that retains pRB binding but with a deletion of the C-terminal domain. Studies from our laboratory and others have shown that the MCV LT C-terminal helicase domain contains growth-inhibiting properties. Additionally, we have shown that host DNA damage response factors are recruited to viral replication centers. In this study, we identified a novel MCV LT phosphorylation site at Ser-816 in the C-terminal domain. We demonstrate that activation of the ATM pathway stimulated MCV LT phosphorylation at Ser-816, whereas inhibition of ATM kinase activity prevented LT phosphorylation at this site. In vitro phosphorylation experiments confirmed that ATM kinase is responsible for phosphorylating MCV LT at Ser-816. Finally, we show that ATM kinase-mediated MCV LT Ser-816 phosphorylation may contribute to the anti-tumorigenic properties of the MCV LT C-terminal domain.

Phosphorylation of large T antigen regulates merkel cell polyomavirus replication.

Merkel Cell Polyomavirus (MCPyV) was recently discovered as a novel human polyomavirus that is associated with ~80% of Merkel Cell Carcinomas. The Large Tumor antigen (LT) is an early viral protein which has a variety of functions, including manipulation of the cell cycle and initiating viral DNA replication. Phosphorylation plays a critical regulatory role for polyomavirus LT proteins, but no investigation of MCPyV LT phosphorylation has been performed to date. In this report mass spectrometry analysis reveals three unique phosphorylation sites: T271, T297 and T299. In vivo replication assays confirm that phosphorylation of T271 does not play a role in viral replication, while modification at T297 and T299 have dramatic and opposing effects on LT's ability to initiate replication from the viral origin. We test these mutants for their ability to bind, unwind, and act as a functional helicase at the viral origin. These studies provide a framework for understanding how phosphorylation of LT may dynamically regulate viral replication. Although the natural host cell of MCPyV has not yet been established, this work provides a foundation for understanding how LT activity is regulated and provides tools for better exploring this regulation in both natural host cells and Merkel cells.

Host DNA damage response factors localize to merkel cell polyomavirus DNA replication sites to support efficient viral DNA replication.

UNLABELLED: Accumulating evidence indicates a role for Merkel cell polyomavirus (MCPyV) in the development of Merkel cell carcinoma (MCC), making MCPyV the first polyomavirus to be clearly associated with human cancer. With the high prevalence of MCPyV infection and the increasing amount of MCC diagnosis, there is a need to better understand the virus and its oncogenic potential. In this study, we examined the relationship between the host DNA damage response (DDR) and MCPyV replication. We found that components of the ATM- and ATR-mediated DDR pathways accumulate in MCPyV large T antigen (LT)-positive nuclear foci in cells infected with native MCPyV virions. To further study MCPyV replication, we employed our previously established system, in which recombinant MCPyV episomal DNA is autonomously replicated in cultured cells. Similar to native MCPyV infection, where both MCPyV origin and LT are present, the host DDR machinery colocalized with LT in distinct nuclear foci. Immunofluorescence in situ hybridization and bromodeoxyuridine (BrdU) incorporation analysis showed that these DDR proteins and MCPyV LT in fact colocalized at the actively replicating MCPyV replication complexes, which were absent when a replication-defective LT mutant or an MCPyV-origin mutant was introduced in place of wild-type LT or wild-type viral origin. Inhibition of DDR kinases using chemical inhibitors and ATR/ATM small interfering RNA (siRNA) knockdown reduced MCPyV DNA replication without significantly affecting LT expression or the host cell cycle. This study demonstrates that these host DDR factors are important for MCPyV DNA replication, providing new insight into the host machinery involved in the MCPyV life cycle. IMPORTANCE: MCPyV is the first polyomavirus to be clearly associated with human cancer. However, the MCPyV life cycle and its oncogenic mechanism remain poorly understood. In this report, we show that, in cells infected with native MCPyV virions, components of the ATM- and ATR-mediated DDR pathways accumulate in MCPyV LT-positive nuclear foci. Such a phenotype was recapitulated using our previously established system for visualizing MCPyV replication complexes in cells. By combining immunofluorescent staining, fluorescence in situ hybridization, and BrdU incorporation analysis, we demonstrate that DDR proteins are important for maintaining robust MCPyV DNA replication. This study not only provides the first look into the microscopic details of DDR factor/LT replication complexes at the MCPyV origin but also provides a platform for further studying the mechanistic role of host DDR factors in the MCPyV life cycle and virus-associated oncogenesis.

Merkel cell polyomavirus large T antigen disrupts host genomic integrity and inhibits cellular proliferation.

Clonal integration of Merkel cell polyomavirus (MCV) DNA into the host genome has been observed in at least 80% of Merkel cell carcinoma (MCC). The integrated viral genome typically carries mutations that truncate the C-terminal DNA binding and helicase domains of the MCV large T antigen (LT), suggesting a selective pressure to remove this MCV LT region during tumor development. In this study, we show that MCV infection leads to the activation of host DNA damage responses (DDR). This activity was mapped to the C-terminal helicase-containing region of the MCV LT. The MCV LT-activated DNA damage kinases, in turn, led to enhanced p53 phosphorylation, upregulation of p53 downstream target genes, and cell cycle arrest. Compared to the N-terminal MCV LT fragment that is usually preserved in mutants isolated from MCC tumors, full-length MCV LT shows a decreased potential to support cellular proliferation, focus formation, and anchorage-independent cell growth. These apparently antitumorigenic effects can be reversed by a dominant-negative p53 inhibitor. Our results demonstrate that MCV LT-induced DDR activates p53 pathway, leading to the inhibition of cellular proliferation. This study reveals a key difference between MCV LT and simian vacuolating virus 40 LT, which activates a DDR but inhibits p53 function. This study also explains, in part, why truncation mutations that remove the MCV LT C-terminal region are necessary for the oncogenic progression of MCV-associated cancers.