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Journal of Virology, June 2005, p. 6741-6750, Vol. 79, No. 11
0022-538X/05/$08.00+0 doi:10.1128/JVI.79.11.6741-6750.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Departments of Pathology,1 Pediatrics,2 Gynecology & Obstetrics, The Johns Hopkins School of Medicine, Baltimore, Maryland 21205,3 University of New Mexico Department of Molecular Genetics and Microbiology, Albuquerque, New Mexico 87131,4 Department of Biochemistry and Molecular Genetics, University of Colorado Health Science Center, School of Medicine, Denver, Colorado 80262,5 Department of Host Defense, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan,6 Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, Maryland 208927
Received 24 November 2004/ Accepted 18 January 2005
Infection with oncogenic human papillomaviruses (HPVs), typified by HPV type 16 (HPV16), is a necessary cause of cervical cancer. Prophylactic vaccination with HPV16 L1 virus-like particles (VLPs) provides immunity. HPV16 VLPs activate dendritic cells and a potent neutralizing immunoglobulin G (IgG) response, yet many cervical cancer patients fail to generate detectable VLP-specific IgG. Therefore, we examined the role of the innate recognition of HPV16 L1 in VLP-induced immune responses and its evasion during carcinogenesis. Nonconservative mutations within HPV16 L1 have been described in isolates from cervical cancer and its precursor, high-grade cervical intraepithelial neoplasia (CIN). We determined the effect of mutations in L1 upon in vitro self-assembly into VLPs and their influence upon the induction of innate and adaptive immune responses in mice. Several nonconservative mutations in HPV16 L1 isolated from high-grade CIN or cervical carcinoma prevent self-assembly of L1 VLPs. Intact VLPs, but not assembly-defective L1, activate dendritic cells to produce proinflammatory factors, such as alpha interferon, that play a critical role in inducing adaptive immunity. Indeed, effective induction of L1-specific IgG1 and IgG2a was dependent upon intact VLP structure. Dendritic cell activation and production of virus-specific neutralizing IgG by VLPs requires MyD88-dependent signaling, although the L1 structure that initiates MyD88-mediated signaling is distinct from the neutralizing epitopes. We conclude that innate recognition of the intact L1 VLP structure via MyD88 is critical in the induction of high-titer neutralizing IgG. Tumor progression is associated with genetic instability and L1 mutants. Selection for assembly-deficient L1 mutations suggests the evasion of MyD88-dependent immune control during cervical carcinogenesis.
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