Prophylactic HPV vaccination; An overview

Introduction: Human papillomavirus infection (HPV) is among the most common sexually transmitteddiseases throughout the world. Approximately ۸۰% of people experience HPV during their sexually activeyears. Considering that a large number of HPV infections are asymptomatic, persistent infections can result insevere morbidity and mortality. Over ۲۰۰ different genotypes of HPV have been identified, among which morethan ۲۰ are known as possible carcinogenic factors. Oncogenic strains of HPV (types ۱۶/۱۸ strains) cause almostall cervical malignancies. HPV vaccines were introduced worldwide in the last decade; and has been effectivein the reduction of HPV infection and related diseases, including cervical, head, and neck as well as anogenitalcancers. HPV-induced cancers are extensively preventable. Hence, primary and secondary prevention isavailable. Pap smear screening tests detect cervical cancers in their early stages while there’s no other screeningmeasurement to detect HPV-related conditions. Given that the diagnosis is quite challenging, primaryprevention using vaccination is highly promising which potentially prevents ۷۰% to ۹۰% of all HPV-relatedcancers. From ۲۰۰۶ to ۲۰۱۴ Gardasil® (quadrivalent HPV vaccine), Cervarix® (bivalent HPV vaccine), andGardasil®۹ (nonavalent HPV vaccine) were approved by FDA and introduced to the market afterwards.Although each vaccine specifically protects against certain virus genotypes, emerging data suggest they alsoinduce cross-strain protection. The mechanism of HPV vaccines is based on a virus-like particle (VLP) of themajor papillomavirus capsid protein L۱. VLPs are mere proteins and do not contain viral genome, thereforethey are considered non-infectious and non-oncogenic. Cervarix® consists of HPV۱۶ and ۱۸ VLPs,monophosphoryl lipid A (MPL), and aluminum hydroxide. MPL is a toll/like receptor ۴ agonist that can inducehigh titers of antibodies compared to Gardasil® and Gardasil® ۹, both of which contain only aluminumhydroxide as an adjuvant.Methods: In this review, we focus on the up-to-date information about current HPV vaccines, and vaccineefficacy.Results: The current vaccines are based on the first-generation VLP (L۱-VLP); whereas the second generation(L۲-VLP and chimeric L۱-L۲ VLP) were shown to target a broader genotype coverage. Both vaccines showrobust protection and efficacy against persistent infection and progression to the related cancers. Moreover,Gardasil®- and Gardasil®۹-induced antibodies disappear more rapidly in comparison to Cervarix® ones. WhileGardasil® may trigger robust strain-specific immunity (however poor cross-protection after vaccination);Cervarix® strongly afforded both within and cross-strain immunity.Conclusion: Regarding the studies, prophylactic vaccination using Cervarix® has been showing more promisingoutcomes than the others.

کلیدواژه ها:

HPV ، vaccination ، Cervarix® ، Gardasil®