Characterization of serum antibodies from women immunized with Gardasil: A study of HPV-18 infection of primary human keratinocytes

Abstract

The prevalent human papillomaviruses (HPVs) infect human epithelial tissues. Infections by the mucosotropic HPV genotypes cause hyperproliferative ano-genital lesions. Persistent infections by high-risk (HR) HPVs such as HPV-16, HPV-18 and related types can progress to high grade intraepithelial neoplasias and cancers. Prophylactic HPV vaccines are based on DNA-free virus-like particles (VLPs) composed of the major capsid protein L1 of HPV-16, -18, -6 and -11 (Gardasil) or HPV-16 and -18 (Cervarix). Sera from vaccinated animals effectively prevent HPV pseudovirions to infect cell lines and mouse cervical epithelia. Both vaccines have proven to be highly protective in people. HPV pseudovirions are assembled in HEK293TT cells from matched L1 and L2 capsid proteins to encapsidate a reporter gene. Pseudovirions and genuine virions have structural differences and they infect cell lines or primary human keratinocytes (PHKs) with different efficiencies. In this study, we show that sera and isolated IgG from women immunized with Gardasil prevent authentic HPV-18 virions from infecting PHKs, whereas non-immune sera and purified IgG thereof are uniformly ineffective. Using early passage PHKs, neutralization is achieved only if immune sera are added within 2 to 4 h of infection. We attribute the timing effect to a conformational change in HPV virions, thought to occur upon initial binding to heparan sulfate proteoglycans (HSPG) on the cell surface. This interpretation is consistent with the inability of immune IgG bound to or taken up by PHKs to neutralize the virus. Interestingly, the window of neutralization increases to 12 to 16 h in slow growing, late passage PHKs, suggestive of altered cell surface molecules. In vivo, this window might be further lengthened by the time required to activate the normally quiescent basal cells to become susceptible to infection. Our observations help explain the high efficacy of HPV vaccines.

Transcriptome analysis of HPV-induced warts and healthy skin in humans

“…Compared to the C15orf59 and CYB561A3 genes, much more is known about the third most down-regulated gene, Fc fragment of IgG receptor and transporter (FCGRT), which encodes for the neonatal Fc receptor and is normally expressed in human epidermal keratinocytes [25]. In cell lines infected with high-risk HPV, FCGRT expression on epithelial keratinocytes was found to modulate the uptake of IgG antibodies [26].…”

Chlamydia Trachomatis Urogenital Infections

“…Systemic immunization with two currently available HPV vaccines induces specific antibodies of the IgG isotype in plasma as well as in genital tract secretions (Kwak et al 2011;Petaja et al 2011;Wang et al 2016). Although local responses in the cervix, manifested by the presence of HPV-specific antibodysecreting cells, have not been demonstrated, based on other studies of the origin of IgG in genital tract after systemic immunization (Underdown and Strober 2015), it is highly probable that such antibodies are of circulatory origin and are selectively transported in the genital secretion by an epithelial FcRn-dependent mechanism.…”