Carrageenan as a Preventive Agent Against Human Papillomavirus Infection: A Narrative Review

Carrageenan, an extract from red algae, was identified over a decade ago as a potent inhibitor of human papillomavirus (HPV) infection in vitro. After this discovery, several studies evaluated carrageenan's anti-HPV activity in cells, experimental animals, and humans. We reviewed the evidence for carrageenan's anti-HPV activity. Studies had to be in vitro, in vivo, or in humans and report on carrageenan's anti-HPV activity. Of the 39 records identified in PubMed and 29 records in Clinicaltrials.gov, 22 records were included after screening: 8 in vitro (including 2 ex vivo), 3 in vivo, 5 in vitro and in vivo, 3 clinical studies, and 3 trial protocols. A total of 12 studies evaluated carrageenan exclusively, whereas 7 considered carrageenan combined with additional antiviral or other agents. One study protocol will evaluate carrageenan exclusively, and 2 others will evaluate carrageenan-combination products. Most clinical studies evaluated carrageenan's ability to prevent HPV acquisition (n = 4), whereas one study explored its ability to promote clearance of existing infection (defined as the absence of HPV DNA detection). Carrageenan's anti-HPV activity was observed consistently across study designs, except in 2 studies: 1 in vitro study where 2 of the HPV types tested were not significantly inhibited by carrageenan and 1 phase IIB trial in gay, bisexual, and other men who have sex with men. This review supports the premise that carrageenan, alone or in combination with other antiviral agents, might be a potential prevention strategy complementary to HPV vaccination for women.