Efficiency of MY09/11 consensus PCR in the detection of multiple HPV infections

Human papillomavirus genotype distribution by cytological status and associated risk factors in the general population of Congolese women living in urban and rural areas: Implications for cervical cancer prevention

INTRODUCTION

Cervical cancer related to high risk-human papillomavirus (HR-HPV) is the second female cancer in the Republic of Congo (Congo). We herein evaluated the molecular epidemiology of cervical HPV infection and associated risk factors in Congolese women living in urban (Brazzaville) and rural (Plateaux department) settings.

PATIENTS AND METHODS

A population-based, cross-sectional survey was conducted to collect demographic and behavioral data among Congolese women, and to obtain endocervical swab samples for HPV DNA molecular detection (Anyplex II HPV28, Seegene, Seoul, South Korea).

RESULTS

A total of 284 women (mean age: 37.8 years; HIV-1-positivity: 18.6%) were included. The prevalence of HPV DNA cervical shedding was 64.4% [HR-HPV: 80.9%, mainly HPV-16 (15.8%), and HPV-35 and HPV-52 (15.3%); multiple HPV infections: 60.6%; 9-valent HPV Gardasil-9® vaccine genotypes: 42.6%]. 91.6% and 100% of low-grade squamous intraepithelial neoplasia (LSIL) and cervical cancer, respectively, showed HR-HPV. HR-HPV prevalence was higher among students (aOR: 7.9) and HIV-infected women (aOR: 3.1) in Brazzaville, and among women aged between 21-30 years (aOR: 7.2) and HIV-infected women (aOR: 5.1) in the Plateaux department.

CONCLUSION

Cervical HR-HPV infection is particularly frequent in young or HIV-infected Congolese women. Prophylactic HPV vaccination combined with primary molecular screening of HR-HPV infection in this country should be extended.

The Role of the p16 and p53 Tumor Suppressor Proteins and Viral HPV16 E6 and E7 Oncoproteins in the Assessment of Survival in Patients with Head and Neck Cancers Associated with Human Papillomavirus Infections

The role of HPV in the survival prognosis of patients with head and neck squamous cell carcinoma, especially patients with laryngeal squamous cell carcinoma (LSCC) and hypopharyngeal squamous cell carcinoma (HPSCC), is still somewhat ambiguous. The present study aimed to explore the significance of tumor suppressor proteins and HPV16 E6 and E7 oncoproteins in the assessment of survival in patients with oropharyngeal squamous cell carcinoma (OPSCC), LSCC, and HPSCC associated with high-risk (HR-) and low-risk (LR-) HPV infections. By utilizing molecular and immunohistochemical investigations of HNSCC samples and patient data, univariate and multivariate survival analyses were conducted. The presence of HPV DNA (LR- and HR-HPV) was associated with a better 5-year OS and DSS for OPSCC and LSCC. The IHC overexpression of HPV16 E6 protein and p16 protein was associated with better survival in the univariate (for OPSCC) and multivariate (OPSCC and HPSCC) survival analyses. The overexpression of p53 was associated with better survival in OPSCC. HPV infection plays a significant role in the tumorigenesis of HNSCC, and the immunohistochemical assessment of HPV16 E6 protein expression should be interpreted as a useful prognostic marker for OPSCC and HPSCC.

Comparison of AmpFire and MY09/11 assays for HPV genotyping in anogenital specimen of Rwandan men who have sex with men

Introduction

The AmpFire HPV genotyping Assay (Atila Biosystems, Mountain View, CA, USA) is a new test for which there are few data regarding its analytic performance and reliability. Using anal and penile swab specimens from a cohort study of men who have sex with men (MSM) in Rwanda, we compared high-risk HPV (hrHPV) detection by AmpFire done at two laboratories, one at University of California San Francisco (UCSF) and the other Rwanda Military Hospital, and well-validated MY09/11-based assay done at UCSF.

Methods

Anal and penile specimens collected from 338 MSM from March 2016 to September 2016 were tested for high-risk HPV genotypes (hrHPV) by MY09/11, AmpFire UCSF and AmpFire RMH. Cohen's kappa coefficient was used to test for reproducibility.

Results

The hrHPV positivity by MY09/11 and AmpFire UCSF was 13% and 20.7% (k = 0.73) for anal specimens and was 26.3% and 32.6% (k = 0.67) for penile specimens. Specifically, good reproducibility was for types 16 and 18 (k = 0.69 and k = 0.71) for anal specimens and (k = 0.50 and k = 0.72) for penile specimens. The hrHPV positivity by AmpFire at UCSF and RMH was 20.7% for both laboratories (k = 0.87) for anal specimens and was 34.9% and 31.9% (k = 0.89) for penile specimens. Specifically, excellent reproducibility was for types 16 and 18 for anal specimens (k = 0.80 and k = 1.00) and penile specimens (k = 0.85 and k = 0.91).

Conclusion

Results show that MY09/11 and AmpFire assays have good reproducibility while the AmpFire UCSF and RMH assays have excellent reproducibility. These results show that AmpFire is a promising HPV genotyping test.

Trends in Co-circulation of Oncogenic HPV Genotypes in Single and Multiple Infections among Unvaccinated Community

Cocirculation of multiple human papillomavirus (HPV) infections with low, probably high, and high‐risk genotypes are to be associated with various grades of infections and cancer progression. The oncogenic high‐risk HPVs are distributed and cocirculated throughout the world. This study was investigated to identify HPV genotypes related to genital disorders in unvaccinated women. The subjects were referred from clinics to a molecular lab for HPV testing in Iran as a low‐coverage vaccinated country. HPVs DNAs of cervical scrapping and genital tissue specimens of 1,133 un‐vaccinated women were genotyped using an in vitro diagnostic line probe (reverse hybridization) assay. In addition, phylogenetic trees were constructed on 100 MY09/MY11 polymerase chain reaction (PCR) amplicons of common genotypes of HPV L1 gene by Sanger sequencing. The mean age of the population study was 32.7 ± 8.0 and the mean age of HPV‐positive cases was 31.6 ± 7.8. HPV DNA was detected in 57.8% (655/1133) of women subjects and 42.2% (478/1133) of cases were undetected. Among 655 HPV‐positive cases, 639 subjects (56.4%) were related to defined genotypes and 16 subjects (1.4%) were untypeable. The highest prevalence rate of HPV genotypes was identified in the 25–34 years. The top 6 dominant HPVs in single and multiple genotypes were HPV6 (284/655 [43.4%]), HPV16 (111/655 [16.9%]), HPV31 (72/655 [11%]), HPV53 (67/655 [10.2%]), HPV11 (62/655 [9.5%]), and HPV52 (62/655 [9.5%]). Moreover, single, multiple and untypeable HPV genotypes were diagnosed as follows: 1 type (318/655 [48.5%]), 2 types (162/655 [24.8%]), 3 types (83/655 [12.7%]), 4 types (42/655 [6.5%]), more than 5 types (34/655 [5.3%]), and 1.4% un‐typeable subjects. The sequenced partial L1 gene of HPV genotypes (GenBank databases under the accession numbers: MH253467‐MH253566) confirmed and determined the cocirculated HPV genotypes' origins and addressed helpful insights into the future viral epidemiology investigations. Multiple HPV infections and cocirculation of various oncogenic HPV genotypes among the normal population (women and men) with asymptomatic forms are still challenging in unvaccinated communities. The preventive and organized surveillance programs for HPV screening are needed to be considered and compiled by health policy makers of low or unvaccinated countries.

Human papillomavirus detected in sperm of Japanese infertile males affects reproductive parameters

OBJECTIVES

The effects of human papillomavirus (HPV) infection on male reproductive parameters are currently a matter of controversy. In order to clarify the issue in Japanese infertile men, the prevalence and localization of HPV in semen, sperm parameters, and superoxide dismutase (SOD) activity in seminal plasma were examined in 216 Japanese infertile men.

METHODS

DNA was extracted from liquid-based cytological semen samples. The β-globin gene was amplified by polymerase chain reaction (PCR), and HPV-DNA was amplified using nested PCR with MY09/MY11 as outer primers and GP5+/GP6+ as inner primers. HPV genotyping was performed in the HPV-positive samples. In addition, SOD levels in seminal plasma were analysed quantitatively. In-situ hybridization (ISH) was performed to localize HPV-DNA in sperm from HPV-positive samples.

RESULTS

Any-risk and high-risk prevalence rates of HPV in semen were 12.5% and 6.9%, respectively. No significant difference in the prevalence of HPV was observed between azoospermic and non-azoospermic subjects. Among non-azoospermic patients, those with HPV detected in semen had significantly lower sperm motility and concentration compared with subjects without HPV detected in semen. SOD levels in seminal plasma were significantly higher in HPV-positive patients compared with HPV-negative patients. ISH analysis of HPV-positive samples revealed that HPV-DNA was localized to the head and mid-piece of sperm. HPV-DNA was present in the sperm of young infertile men.

CONCLUSION

HPV infection of sperm was associated with reduced sperm motility and concentration, and resulted in an increase in seminal SOD activity.

Comparative analysis of different PCR-based strategies for HPV detection and genotyping from cervical samples

BACKGROUND

Human papillomavirus (HPV) is the main cause of cervical cancer. Polymerase chain reaction (PCR)-based techniques are associated with accurate results with respect to HPV detection and genotyping, being able to identify viral DNA at low levels. However, differences in primer design influence their sensibility and specificity, depending on the HPV type assessed.

OBJECTIVE

The aim of the study was to comparatively evaluate the effectiveness of three different PCR-based strategies for HPV detection and genotyping from cervical samples.

STUDY DESIGN

The procedures were based on different primer design strategies, using MY09/MY11, EntroA, and type specific multiplex PCR primers.

RESULTS

Out of 411 samples of cervical scrapings, 45 (10.9%), 50 (12.2%), and 117 (28.5%) were positive for MY09/MY11, EntroA, and multiplex PCR, respectively. For MY09/MY11 positive samples, 36 were negative for EntroA and 23 for multiplex PCR. For EntroA positive samples, 40 were negative for MY09/MY11 and 26 for multiplex PCR. For multiplex PCR positive samples, 96 were negative for MY09/MY11 and 94 for EntroA. MY09/MY11 identified 12 different HPV types, EntroA detected eight types and multiplex PCR detected 11 HPV types. EntroA primers were able to detect HPV in more samples than MY09/MY11, while multiplex PCR, despite the limited targeted HPV types, presented higher sensibility than the other methods.

CONCLUSIONS

The three methods presented different advantages and disadvantages, and the present study reinforces the need to use more than one molecular strategy for HPV detection and genotyping, and the development of novel methods which could overcome the limitations of the existing tests.

Identification of High-Risk Human Papillomavirus DNA, p16, and E6/E7 Oncoproteins in Laryngeal and Hypopharyngeal Squamous Cell Carcinomas

Human papillomavirus (HPV) was proven to play a significant role in cancer development in the oropharynx. However, its role in the development of laryngeal (LSCC) and hypopharyngeal squamous cell carcinoma (HPSCC) remains to be clarified. High-risk HPV (HR-HPV) viral proteins E6 and E7 are considered to be pertinent to HPV-related carcinogenesis. Hence, our aim was to estimate LSCC and HPSCC for HR-HPV DNA, p16, and E6/E7 oncoprotein status by using molecular virology and immunohistochemistry methods. The prevalence of HPV16 infection was 22/41 (53.7%) and 20/31 (64.5%) for LSCC and HPSCC, accordingly. The majority of HPV16+ tumor samples were stage III or IV. In most samples, the presence of either HPV16 E6 or HPV16 E7 viral protein in dysplastic or tumor cells was confirmed using immunohistochemistry. Our results suggest a high prevalence of HPV16 as a primary HR-HPV type in LSCC and HPSCC. The lack of HPV E6/E7 oncoproteins in some tumor samples may suggest either the absence of viral integration or the presence of other mechanisms of tumorigenesis. The utilization of p16 IHC as a surrogate marker of HR-HPV infection is impractical in LSCC and HPSCC.

Immune responses against autologous tumor and human papilloma virus in lymph nodes from patients with penile cancer

Purpose

Nearly half of penile cancers are related to human papillomavirus (HPV) infection. Investigations of tumor- and HPV-specific T cell reactivity in regional lymph nodes (LNs) from patients with penile cancer are warranted.

Materials and Methods

In this study, single-cell suspensions from LNs and peripheral blood from 11 patients with penile cancer were stained with antibodies for lymphocyte markers and analyzed by fluorescence-activated cell sorting (FACS). DNA was extracted from the tumor tissue and HPV status was investigated by PCR.

Results

T-cell reactivity against autologous tumor-extract and against the HPV-vaccine Gardasil® was tested by flow-cytometric assay of specific cell-mediated immune response in activated whole blood (FASCIA). CD4⁺/CD8⁺ ratios were significantly lower in HPV positive LNs (p<0.05). Immune responses to tumor extract assessed by blast transformation and expansion in vitro, of either CD4⁺ or CD8⁺ T-cells, were found in 9 of 13 LNs (69%). 5 of 6 tested patients demonstrated T cell recognition of tumor-associated antigen(s). In HPV-positive patients, dose-dependent T cell responses against L1 (late) HPV proteins (Gardasil vaccine) were demonstrated.

Conclusions

LN-derived T cells from patients with penile cancer recognize tumor antigen(s) and in HPV-positive cases, there is a response against L1 (late) HPV proteins, being constituents of the Gardasil vaccine.

Application of an entropy-based computational strategy to identify genomic markers for molecular detection and typing of human papillomavirus

Human papillomavirus (HPV) is a diverse group of double-stranded DNA viruses that present high tropism for the epithelium and infect keratinocytes. Currently, over 200 viral types have been identified, and almost 40 types preferentially infect the epithelial cells of the genital tract. Infections caused by HPV are the most prevalent viral infections that are sexually transmitted in the world. Given how HPV infection is one of the key factors in the development of cervical cancer, we need to develop more effective diagnostic methods to correctly diagnose patients. The significance of our research is that we have developed and applied a novel computational approach based on entropy to identify phylogenetically informative genomic regions that could be used as markers for the detection and typing of HPV. We have demonstrated that our strategy is capable of finding phylogenetically informative L1 regions to design a primer set that can be used to accurately detect and genotype HPV isolates.

Analytical evaluation of a new Microdisk™ technology-based multiplex HPV genotyping system – the QPLEX™ HPV genotyping kit

Background

Recently, the QPLEX™ human papillomavirus (HPV) genotyping kit (QuantaMatrix, Seoul, Korea), a Microdisk™ technology-based multiplex system, was developed to detect 32 HPV genotypes. We evaluated the analytical performance of this kit by conducting a comparison study, precision evaluation and interference testing.

Methods

A total of 1594 cervical swab specimens were used to compare the QPLEX™ HPV genotyping kit with other commercially available kits (GeneFinder HPV Liquid Bead MicroArray Genotype polymerase chain reaction [PCR] kit, Infopia, Seoul, Korea; PANArray™ HPV Genotyping Chip, PANAGENE, Daejeon, Korea). For the determination of precision, we evaluated four types of precision profiles: repeatability, lot-to-lot variability, operator-to-operator variability and site-to-site variability. In addition, interference tests were performed with various interferents.

Results

The results of the QPLEX™ HPV genotyping kit showed almost perfect agreement with the other commercially available HPV genotyping assays. The combined precision was acceptable. In addition, there was no tested interferent that affected the results of the QPLEX™ HPV genotyping kit.

Conclusions

The QPLEX™ HPV genotyping kit showed acceptable analytical performance in our study. This assay could be a suitable option for HPV genotyping in routine and follow-up tests.

Importance of High-Risk Human Papillomavirus Infection Detection in Female Renal Transplant Recipients in the First Year after Transplantation

Objectives

Most of human papillomavirus (HPV) infections are “cleared” by the immune system; however, in cases of immune system suppression, infections could lead to development of malignancies. The aim of this study was to find out the frequency of HR-HPV infection in early period after renal transplantation in recipients receiving immunosuppressive therapy and to follow the progression of the infection up to one year.

Methods

43 female renal transplant recipients and 79 healthy female individuals as a control group were enrolled in this investigation. For the detection of HPV infection, patients' samples (blood and vaginal swabs) were collected two weeks after transplantation with following collection of six months and one year. Different polymerase chain reactions for HR-HPV genomic sequences detection and ELISA kit for detection of anti-HPV IgG antibodies were used.

Results

In this study, we show that frequency rate of HR-HPV infection has increased in the first year after transplantation from early stage of immunosuppressive therapy (from 24% to 36%). Also an increase of HR-HPV load was detected over time, showing the highest median viral load at sixth month after transplantation.

Conclusions

From the obtained data, it follows that it is very important to carefully monitor patients receiving immunosuppression therapy on progression of HR-HPV.

Human Papillomavirus E6 biosensing: Current progression on early detection strategies for cervical Cancer

Prognosis of early cancer detection becomes one of the tremendous issues in the medical health system. Medical debates among specialist doctor and researcher in therapeutic approaches became a hot concern for cervix cancer deficiencies early screening, risk factors cross-reaction, portability device, rapid and free labeling system. The electrical biosensing based system showed credibility in higher specificity and selectivity due to hybridization of DNA duplex between analyte target and DNA probes. Electrical DNA sensor for cervix cancer has attracted too many attentions to researcher notification based on high performance, easy to handle, rapid system and possible to miniaturize. This review explores the current progression and future insignificant for HPV E6 genobiosensing for early Detection Strategies of Cervical Cancer.

Prevalence of High-Risk Human Papillomavirus in Tonsil Tissue in Healthy Adults and Colocalization in Biofilm of Tonsillar Crypts

IMPORTANCE

The pathogenesis of human papillomavirus (HPV)-associated oropharyngeal squamous cell carcinoma is currently an important topic of elucidation. The presence of latent HPV infection in tonsil tissue of healthy adults may provide an explanation for a component of this process and contribute to the understanding of HPV-associated squamous cell carcinoma oncogenesis of the oropharynx.

OBJECTIVE

To determine the prevalence of oropharyngeal HPV and to determine the spatial relationship between the virus and crypt biofilm in tonsil tissue.

DESIGN, SETTING, AND PARTICIPANTS

A retrospective, cross-sectional study was carried out using samples obtained from tonsils that were archived at a university hospital following elective nononcologic tonsillectomy from 2012 to 2015. Samples consisted of formalin-fixed paraffin embedded samples of tumor-free tonsil tissue from 102 adults between the ages of 20 and 39 years.

EXPOSURES

Human papillomavirus status was assessed by polymerase chain reaction, and high-risk subtypes 16 and 18 were assessed with quantitative polymerase chain reaction assay. Samples that demonstrated presence of HPV were then analyzed by in situ hybridization to localize the viral capsid protein. These samples were then stained with concanavalin A to establish biofilm presence and morphology. These samples were also stained with diamidino-phenylindole (DAPI) to visualize location of the virus in relation to cell nuclei. These data were then assembled for aggregate analysis to colocalize HPV in the biofilm of the tonsillar crypts.

MAIN OUTCOMES AND MEASURES

Outcome measurements were determined prior to data collection and include prevalence of high-risk HPV types 16 and 18 in tonsil tissue of otherwise healthy adults, as well as demonstration with immunohistochemistry of HPV in tonsillar crypt biofilm.

RESULTS

In 102 otherwise healthy adults (55 [53.9%] female; age range, 20-39 years), the overall prevalence of HPV in tonsils was 4.9% (n = 5); and high-risk type 16 or 18, 3.9% (n = 4). In this sample population, in situ hybridization colocalized HPV virus to the biofilm of the tonsillar crypts.

CONCLUSIONS AND RELEVANCE

Biofilm is present in the tonsillar crypts in a considerable proportion of tonsil tissues and may be reproducibly identified. Human papillomavirus is demonstrated to colocalize to the crypt biofilm. This has important implications with respect to the determination of HPV prevalence rates in the oropharynx. It may also play a role in the pathogenesis of HPV-related oropharyngeal carcinoma.

Artemisinin Represses Telomerase Subunits and Induces Apoptosis in HPV-39 Infected Human Cervical Cancer Cells

Artemisinin, a plant-derived antimalarial drug with relatively low toxicity on normal cells in humans, has selective anticancer activities in various types of cancers, both in vitro and in vivo. In the present study, we have investigated the anticancer effects of artemisinin in human cervical cancer cells, with special emphasis on its role in inducing apoptosis and repressing cell proliferation by inhibiting the telomerase subunits, ERα which is essential for maintenance of the cervix, and downstream components like VEGF, which is known to activate angiogenesis. Effects of artemisinin on apoptosis of ME-180 cells were measured by flow cytometry, DAPI, and annexin V staining. Expression of genes and proteins related to cell proliferation and apoptosis was quantified both at the transcriptional and translational levels by semi-quantitative RT-PCR and western blot analysis, respectively. Our findings demonstrated that artemisinin significantly downregulated the expression of ERα and its downstream component, VEGF. Antiproliferative activity was also supported by decreased telomerase activity and reduced expression of hTR and hTERT subunits. Additionally, artemisinin reduced the expression of the HPV-39 viral E6 and E7 components. Artemisinin-induced apoptosis was confirmed by FACS, nuclear chromatin condensation, annexin V staining. Increased expression of p53 with concomitant decrease in expression of the p53 inhibitor Mdm2 further supported that artemisinin-induced apoptosis was p53-dependent. The results clearly indicate that artemisinin induces antiproliferative and proapoptotic effects in HPV-39-infected ME-180 cells, and warrants further trial as an effective anticancer drug.

Comparison of Three Different Commercial Kits for the Human Papilloma Virus Genotyping

BACKGROUND

High-risk type human papilloma virus (HPV) is the most important cause of cervical cancer. Recently, real-time polymerase chain reaction and reverse blot hybridization assay-based HPV DNA genotyping kits are developed. So, we compared the performances of different three HPV genotyping kits using different analytical principles and methods.

METHODS

Two hundred positive and 100 negative cervical swab specimens were used. DNA was extracted and all samples were tested by the MolecuTech REBA HPV-ID, Anyplex II HPV28 Detection, and HPVDNAChip. Direct sequencing was performed as a reference method for confirming high-risk HPV genotypes 16, 18, 45, 52, and 58.

RESULTS

Although high-level agreement results were observed in negative samples, three kits showed decreased interassay agreement as screening setting in positive samples. Comparing the genotyping results, three assays showed acceptable sensitivity and specificity for the detection of HPV 16 and 18. Otherwise, various sensitivities showed in the detection of HPV 45, 52, and 58.

CONCLUSIONS

The three assays had dissimilar performance of HPV screening capacity and exhibited moderate level of concordance in HPV genotyping. These discrepant results were unavoidable due to difference in type-specific analytical sensitivity and lack of standardization; therefore, we suggested that the efforts to standardization of HPV genotyping kits and adjusting analytical sensitivity would be important for the best clinical performance.

Comparative evaluation of the GP5+/6+, MY09/11 and PGMY09/11 primer sets for HPV detection by PCR in oral squamous cell carcinomas

The aim of this study was to evaluate the use of GP5+/6+, MY09/11 and PGMY09/11 primer sets for the detection of human papillomavirus (HPV) DNA by single step polymerase chain reaction (PCR) and nested PCR in formalin-fixed and paraffin-embedded (FFPE) tissues from oral squamous cell carcinomas (OSCCs). DNA extracted from FFPE tissues were tested for amplification of the human beta globin gene with PCO3/4 primers. Positive samples for this gene were tested for HPV DNA using single step PCR with GP5+/6+, MY09/11 and PGMY09/11 primer sets. All negative samples at single step PCR with MY09/11 and PGMY09/11 were subjected to a further PCR with GP5+/6+ primers using the non-amplified product in the previously reactions (nested PCR) as samples. Among 26 samples, 23 were positive for the human beta globin gene and were considered viable for HPV DNA detection by PCR. Single step PCR with GP5+/6+ and MY09/11 primers and MY/GP+ nested PCR did not amplify HPV DNA in any samples. PGMY09/11 primers detected HPV DNA in 13.0% of OSCC cases and this rate was raise to 17.4% with the use of PGMY/GP+ nested PCR. According to our results the PGMY/GP+ nested PCR is the most appropriate primer set for the detection of HPV DNA using FFPE samples from OSCC.

Viral infections and colorectal cancer: a systematic review of epidemiological studies

Numerous studies have found the presence of viral DNA in colorectal tumor tissues. However, whether viral infections contribute to the risk of colorectal cancer (CRC) is still under debate. We aimed to provide an overview of published epidemiological studies on the association between viral infections and CRC. A systematic literature search was performed in PubMed to find relevant studies published until 8 May 2014. Information collected included study population, sample type, laboratory method and prevalence of viral infection in cancer or precancer patients and controls. We found 41 studies that fulfilled the selection criteria, all of which had cross-sectional or case-control designs, and most of which were of small to moderate size. Viral infections included human papillomaviruses (HPV), human polyomaviruses, human herpesviruses, human bocavirus and Inoue-Melnick virus. Inconsistent results were observed across studies. Many studies reported higher viral DNA prevalence in tumor tissues than in normal noncancerous tissues either in the same patients or in CRC-free controls. However, potential contamination or temporal sequence of the infection and cancer development were often unclear. Seroprevalence studies assessing antibody titers indicative of viral infections did not find statistically significant differences between CRC cases and healthy controls. Overall published evidence on the role of viral infections in CRC etiology remains limited. Given the potential importance of viral infections and their implication for prevention, there is a strong need for large, methodologically rigorous epidemiological studies.