Infection by certain human papillomavirus types is regarded as the major risk factor in the development of cervical cancer, one of the most common cancers of women worldwide. Analysis of the immunogenic and structural features of papillomavirus vinons has been hampered by the inability to efficiently propagate the viruses in cultured cells. For instance, it has not been established whether the major capsid protein Li alone is sufficient for virus particle assembly. Relatively little is known about the immunity to papillomavirus infections, in large part due to the inability to generate virus stocks in vitro. Studies of immunity to papillomavirus infection have principally been conducted using the BPV model, since relatively large numbers of infectious virus particles can be isolated from BPV-induced warts, and, in contrast to the HPVs, a quantitative focal transformation assay for BPV infectivity has been developed (10). Rabbit antisera raised against infectious BPV1 virions have been shown to contain high-titer antibodies that inhibit focal transformation of C127 cells (10) and also inhibit transformation of fetal bovine skin grafts, whereas antisera raised against denatured virions do not (11). In addition, monoclonal antibodies (mAbs) that neutralized HPV11 infection in a mouse xenograft assay recognized native, but not denatured, HPV11 virions (12). Therefore, it appears that neutralizing antibodies recognize conformationally dependent epitopes. It has been reported that neutralizing antibodies can be generated against both bacterially derived BPV Li and L2 but these antibodies were of very low titer (13,14). Similarly, in vitro-synthesized cottontail rabbit papillomavirus Li and L2 only induced low-titer neutralizing sera (15,16). It is therefore not known whether the high-titer antibodies raised against intact virions principally recognize epitopes from Li, L2, or a combination of the two proteins.With the long-term goal to gain insight into the immune response to papillomavirus infection and to develop a papillomavirus vaccine, we have expressed the LI major capsid protein of HPV16 and BPV1 in insect cells. In contrast to previous reports (17), we demonstrate that Li alone is sufficient for assembly of virus-like particles that are morphologically similar to native virions. These in vitrosynthesized particles are able to induce high-titer neutralizing antisera that are capable of preventing papillomavirus infection in vitro.Abbreviations: BPV, bovine papillomavirus; HPV, human papillomavirus; AcMNPV, Autographa californica multiple nuclear polyhedrosis virus; nt, nucleotide(s); mAb, monoclonal antibody; wt, wild type. 12180The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

SummaryTumor necrosis factor a (TNF-a), in addition to being cytotoxic for certain tumor cells, has turned out as a multifunctional cytokine that is involved in the regulation of immunity and inflammation. Since human keratinocytes have been demonstrated to be a potent source of various cytokines, it was investigated whether epidermal cells synthesize and release TNF-m Supernatants derived from normal human keratinocytes (HNK) and human epidermoid carcinoma cell lines (KB, A431) were tested both in a TNF-a-specific ELISA and a bioassay. In supernatants of untreated epidermal cells, no or minimal TNF-a activity was found, while after stimulation with lipopolysaccharide (LPS) or ultraviolet (UV) light, significant amounts were detected. Western blot analysis using an antibody directed against human TNF-a revealed a molecular mass of 17 kD for keratinocyte-derived TNF-a. These biological and biochemical data were also confirmed by Northern blot analysis revealing mRNA specific for TNF-a in LPS-or ultraviolet B (UVB)-treated HNK and KB cells. In addition, increased TNF-a levels were detected in the serum obtained from human volunteers 12 and 24 h after a single total body UVB exposure, which caused a severe sunburn reaction . These findings indicate that keratinocytes upon stimulation are able to synthesize and release TNF-a, which may gain access to the circulation. Thus, TNF-a in concert with other epidermal cell-derived cytokines may mediate local and systemic inflammatory reactions during host defense against injurious events caused by microbial agents or UV irradiation.

Background-Previous studies have demonstrated that genital infection with high-risk types of human papillomavirus (HPV), most often HPV16, is the most significant risk factor for the development of cervical cancer. However, serologic assays that have been developed to identify high-risk HPV infection have either failed to associate serum reactivity with other indicators of HPV infection or have identified only a minority of HPV-infected individuals.

Cutaneous HPV types are primarily detected at sites extensively exposed to the sun. HPV types of Beta-papillomavirus species 2, but not of species 1, are associated with squamous cell carcinoma.