Figure 1. The seaweeds Porphyra umbilicalis (left) and Chondrus crispus (right)
This creates the question as to why these algae are able to prevent HPV from promoting carcinogenesis. The answer lies in the component known as carrageenan, a sulphated polysaccharide that is common to both seaweeds (2). By adhering to surface viral proteins, carrageenan interferes with the ability of viruses such as HPV to attach to and invade human cells. More significantly, the HPVs associated with genital disease are a thousand times more susceptible to carrageenan than other infective organisms such as herpes simplex and the human immunodeficiency virus (4). The fact that some infant formulas contain carrageenan raises the possibility that baby feeds could prevent juvenile laryngeal papillomatosis in the new born since the disease is initiated by vertical transmission of HPV during birth from mothers who have genital warts. Carrageenan is also a constituent of microbicides (lubricant gels) and clinical trials have shown that regular use of these products during sexual activity is highly effective at preventing the spread of HPV that are associated with genital cancers (5). With the potency of antioxidants and carrageenan already established in preventing HPV-related diseases, it is evident they have a significant role to play in the global fight against cervical cancer. Nevertheless, there are other, perhaps more important, precautionary measures to consider such as cervical cytology screening, molecular testing for HPV and vaccination. Existing programmes are typically reliant on attendance at health centres where smears are taken by clinicians prior to dispatch to central laboratories for staining and screening (Figure 2).
Figure 2. Cervical smear preparation using (a) the conventional Papanicolaou (Pap) and (b) liquid-based cytology (LBC)
Figure 3. Vaginal self-sampling devices: Sanitary products (left), swabs (centre)
and brushes (right)
With the global uptake of conventional cervical screening poor due to geographic, socioeconomic and cultural barriers, vaginal self-sampling is a valuable option for providing those populations with access to screening programs. With the further potential of urine sampling as a low cost, non-invasive tool for analyzing high-risk HPV, the possibilities are endless for preventing cervical cancer worldwide (11). However, encouraging and educating women to conduct self-sampling whilst giving assurances to those who may distrust results will certainly be challenging. In addition, missed opportunities to converse with clinicians about other concerns and the management of follow-up of HPV positive patients are further barriers.
- Dietary antioxidant intake and human papillomavirus infection: Evidence from a cross-sectional study in Italy (Barchitta et al, 2020). Nutrients 2020;12:1384.
- Anti-cancer activity of porphyran and carrageenan from red seaweeds (Liu et al, 2019). Molecules 2019;24:4286.
- Dietary supplementation with the red seaweed Porphyra umbilicalis protects against DNA damage and pre-malignant dysplastic skin lesions in HPV-transgenic mice (Santos et al, 2019). Marine Drugs 2019;17:0615.
- Antiviral activities of algal-based sulfated polysaccharides (Panggabean et al, 2022). Molecules 2022;27:1178.
- Are bioactive molecules from seaweeds a novel and challenging option for the prevention of HPV infection and cervical cancer therapy? - A review (Moga et al, 2021). International Journal of Molecular Sciences 2021;22:629.
- Results of a phase 1, randomized, placebo controlled first-in-human trial of griffithsin formulated in a carrageenan vaginal gel (Teleshova et al, 2022). PLoS ONE 2022;17(1): e0261775.
- Worldwide use of HPV self-sampling for cervical cancer screening (Serrano et al, 2022). Preventive Medicine 2022;154:106900.
- Effects of menstrual cycle on the accumulation of HPV-infected cells exfoliated from the cervix that drift into the vagina (Okodo et al, 2022). Microorganisms 2022;10:693.
- Validity and acceptance of self vs conventional sampling for the analysis of human papillomavirus and Pap smear (Castanyer et al, 2022). Research Square 2022:
- Meta-analysis of agreement/concordance statistics in studies comparing self- vs clinician-collected samples for HPV testing in cervical cancer screening (Arbyn et al, 2022). International Journal of Cancer 2022;1-5.
- Urine HPV in the context of genital and cervical cancer screening - An update of current literature (Daponte et al, 2021). Cancers 2021;13:1640.
Written by Dr Phil Bryant, MS, PhD#GeneralAnatomicPathology#2022#Blog