Human papillomavirus (HPV) types 6, 11, 16 and 18 L1 virus-like particles (VLPs) have been used to generate the prophylactic quadrivalent vaccine, Gardasil ® . There is a high degree of L1 homology between HPV types and it is likely that there is a substantial degree of surface exposed viral epitope similarity. An investigation of vaccine-induced antibody binding and neutralization was undertaken focusing on A7 species members, HPV 18 and 45. Polyclonal sera from Gardasil ® recipients and from HPV 18 L1 VLP recipients were evaluated. Vaccine-induced antibodies were found to cross-neutralize HPV 45 pseudovirions (PsV) in vitro. Examination of a panel of monoclonal antibodies made against L1 VLPs revealed the presence of conformational, neutralizing epitopes on the surface of VLPs that may be shared between HPV 18 and HPV 45. These data demonstrate that Gardasil(r) immunization induces antibodies capable of neutralizing HPV 18 PsV and HPV 45 PsV in vitro.

In an effort to characterize important epitopes of Staphylococcus aureus iron-regulated surface determinant B (IsdB), murine IsdB-specific monoclonal antibodies (MAbs) were isolated and characterized. A panel of 12 MAbs was isolated. All 12 MAbs recognized IsdB in enzyme-linked immunosorbent assays and Western blots; 10 recognized native IsdB expressed by S. aureus. The antigen epitope binding of eight of the MAbs was examined further. Three methods were used to assess binding diversity: MAb binding to IsdB muteins, pairwise binding to recombinant IsdB, and pairwise binding to IsdB-expressing bacteria. Data from these analyses indicated that MAbs could be grouped based on distinct or nonoverlapping epitope recognition. Also, MAb binding to recombinant IsdB required a significant portion of intact antigen, implying conformational epitope recognition. Four MAbs with nonoverlapping epitopes were evaluated for in vitro opsonophagocytic killing (OPK) activity and efficacy in murine challenge models. These were isotype switched from immunoglobulin G1 (IgG1) to IgG2b to potentially enhance activity; however, this isotype switch did not appear to enhance functional activity. MAb 2H2 exhibited OPK activity (>50% killing in the in vitro OPK assay) and was protective in two lethal challenge models and a sublethal indwelling catheter model. MAb 13C7 did not exhibit OPK (<50% killing in the in vitro assay) and was protective in one lethal challenge model. Neither MAb 13G11 nor MAb 1G3 exhibited OPK activity in vitro or was active in a lethal challenge model. The data suggest that several nonoverlapping epitopes are recognized by the IsdB-specific MAbs, but not all of these epitopes induce protective antibodies.

A prophylactic vaccine for genital herpes disease remains an elusive goal. We report the results of two studies performed collaboratively in different laboratories that assessed immunogenicity and vaccine efficacy in herpes simplex virus 1 (HSV-1)-seropositive guinea pigs immunized and subsequently challenged intravaginally with HSV-2. In study 1, HSV-2 glycoproteins C (gC2) and D (gD2) were produced in baculovirus and administered intramuscularly as monovalent or bivalent vaccines with CpG and alum. In study 2, gD2 was produced in CHO cells and given intramuscularly with monophosphoryl lipid A (MPL) and alum, or gC2 and gD2 were produced in glycoengineered Pichia pastoris and administered intramuscularly as a bivalent vaccine with Iscomatrix and alum to HSV-1-naive or -seropositive guinea pigs. In both studies, immunization boosted neutralizing antibody responses to HSV-1 and HSV-2. In study 1, immunization with gC2, gD2, or both immunogens significantly reduced the frequency of genital lesions, with the bivalent vaccine showing the greatest protection. In study 2, both vaccines were highly protective against genital disease in naive and HSV-1-seropositive animals. Comparisons between gD2 and gC2/gD2 in study 2 must be interpreted cautiously, because different adjuvants, gD2 doses, and antigen production methods were used; however, significant differences invariably favored the bivalent vaccine. Immunization of naive animals with gC2/gD2 significantly reduced the number of days of vaginal shedding of HSV-2 DNA compared with that for mock-immunized animals. Surprisingly, in both studies, immunization of HSV-1-seropositive animals had little effect on recurrent vaginal shedding of HSV-2 DNA, despite significantly reducing genital disease.

Epidemiological studies and clinical trials of vaccines depend on the accurate measurement of antibodies within the polyclonal response to infection or vaccination. The assay currently used to measure the antibody response to vaccination with GARDASIL [Quadrivalent Human Papillomavirus (Types 6, 11, 16, 18) Recombinant Vaccine]--a quadrivalent vaccine used against human papillomavirus (HPV) types 6, 11, 16, and 18--is a competitive Luminex assay (cLIA) that uses multiplex technology to detect type-specific neutralizing antibodies against all four HPV types in a single serum sample. Here we describe how the cLIA was developed, as well as how the monoclonal antibodies (mAbs), used as competitors in the assay, were characterized. An enzyme-linked immunosorbent assay (ELISA) was used to screen eight previously-identified mAbs for their ability to bind to HPV virus-like particles (VLPs) in a type-specific and conformation-dependent manner. Four of these mAbs, H6.M48, K11.B2, H16.V5, and H18.J4, met our specifications and were shown to have the potential to neutralize HPV infection in hemagglutination inhibition and pseudovirus neutralization assays. The competitive immunoassay format was able to distinguish type-specific antibodies in the sera of nonhuman primates vaccinated with HPV VLPs, whereas a traditional direct-bind ELISA could not. In addition, the serum antibodies measured by the competitive assay are known to be neutralizing, whereas the ELISA does not distinguish neutralizing and nonneutralizing antibodies in a serum sample. By detecting antibodies to neutralizing epitopes, the competitive assay both demonstrates sero-conversion and provides a potential functional link between sero-conversion and protective immunity in response to vaccination with GARDASIL.

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