Disassembly and reassembly of human papillomavirus virus-like particles produces more virion-like antibody reactivity

<p>Abstract</p> <p>Background</p> <p>Human papillomavirus (HPV) vaccines based on major capsid protein L1 are licensed in over 100 countries to prevent HPV infections. The yeast-derived recombinant quadrivalent HPV L1 vaccine, GARDASIL(R), has played an important role in reducing cancer and genital warts since its introduction in 2006. The L1 proteins self-assemble into virus-like particles (VLPs).</p> <p>Results</p> <p>VLPs were subjected to post-purification disassembly and reassembly (D/R) treatment during bioprocessing to improve VLP immunoreactivity and stability. The post-D/R HPV16 VLPs and their complex with H16.V5 neutralizing antibody Fab fragments were visualized by cryo electron microscopy, showing VLPs densely decorated with antibody. Along with structural improvements, post-D/R VLPs showed markedly higher antigenicity to conformational and neutralizing monoclonal antibodies (mAbs) H16.V5, H16.E70 and H263.A2, whereas binding to mAbs recognizing linear epitopes (H16.J4, H16.O7, and H16.H5) was greatly reduced.</p> <p>Strikingly, post-D/R VLPs showed no detectable binding to H16.H5, indicating that the H16.H5 epitope is not accessible in fully assembled VLPs. An atomic homology model of the entire</p> <p>HPV16 VLP was generated based on previously determined high-resolution structures of bovine papillomavirus and HPV16 L1 pentameric capsomeres.</p> <p>Conclusions</p> <p>D/R treatment of HPV16 L1 VLPs produces more homogeneous VLPs with more virion-like antibody reactivity. These effects can be attributed to a combination of more complete and regular assembly of the VLPs, better folding of L1, reduced non-specific disulfide-mediated aggregation and increased stability of the VLPs. Markedly different antigenicity of HPV16 VLPs was observed upon D/R treatment with a panel of monoclonal antibodies targeting neutralization sensitive epitopes. Multiple epitope-specific assays with a panel of mAbs with different properties and epitopes are required to gain a better understanding of the immunochemical properties of VLPs and to correlate the observed changes at the molecular level. Mapping of known antibody epitopes to the homology model explains the changes in antibody reactivity upon D/R. In particular, the H16.H5 epitope is partially occluded by intercapsomeric interactions involving the L1 C-terminal arm. The homology model allows a more precise mapping of antibody epitopes. This work provides a better understanding of VLPs in current vaccines and could guide the design of improved vaccines or therapeutics.</p

How long do nosocomial pathogens persist on inanimate surfaces? A systematic review

BACKGROUND: Inanimate surfaces have often been described as the source for outbreaks of nosocomial infections. The aim of this review is to summarize data on the persistence of different nosocomial pathogens on inanimate surfaces. METHODS: The literature was systematically reviewed in MedLine without language restrictions. In addition, cited articles in a report were assessed and standard textbooks on the topic were reviewed. All reports with experimental evidence on the duration of persistence of a nosocomial pathogen on any type of surface were included. RESULTS: Most gram-positive bacteria, such as Enterococcus spp. (including VRE), Staphylococcus aureus (including MRSA), or Streptococcus pyogenes, survive for months on dry surfaces. Many gram-negative species, such as Acinetobacter spp., Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, Serratia marcescens, or Shigella spp., can also survive for months. A few others, such as Bordetella pertussis, Haemophilus influenzae, Proteus vulgaris, or Vibrio cholerae, however, persist only for days. Mycobacteria, including Mycobacterium tuberculosis, and spore-forming bacteria, including Clostridium difficile, can also survive for months on surfaces. Candida albicans as the most important nosocomial fungal pathogen can survive up to 4 months on surfaces. Persistence of other yeasts, such as Torulopsis glabrata, was described to be similar (5 months) or shorter (Candida parapsilosis, 14 days). Most viruses from the respiratory tract, such as corona, coxsackie, influenza, SARS or rhino virus, can persist on surfaces for a few days. Viruses from the gastrointestinal tract, such as astrovirus, HAV, polio- or rota virus, persist for approximately 2 months. Blood-borne viruses, such as HBV or HIV, can persist for more than one week. Herpes viruses, such as CMV or HSV type 1 and 2, have been shown to persist from only a few hours up to 7 days. CONCLUSION: The most common nosocomial pathogens may well survive or persist on surfaces for months and can thereby be a continuous source of transmission if no regular preventive surface disinfection is performed

Induction of immune responses against human papillomaviruses by hypervariable epitope constructs

An ideal prophylactic vaccine against human papillomaviruses (HPV) would be one that can induce broadly reactive antibody titres to at least the major oncogenic strains of HPV. It has been previously shown that HPV structural proteins are highly immunogenic but fail to elicit cross-reactive immune responses against heterologous strains of HPV. Recent studies have demonstrated that the immunity induced by virus-like particles is mostly type specific. In the present study, we determined the breadth of reactivity of antibodies induced in mice immunized with hypervariable epitope constructs (HECs), which represent sequence variants of immunodominant B-cell epitopes of the major capsid protein L1 of HPV. In order to test the breadth of reactivity, sera from immunized mice were tested against peptides representing analogous sequences of HPV types 16, 18, 31 and 45. Mice immunized with HECs based on two epitopes mounted antibody responses that cross-reacted with two different analogues, 16 and 18. Significantly, antibodies from mice immunized with HECs also inhibited haemagglutination mediated by HPV-16 L1 VLPs, suggesting that immunization resulted in the development of antibodies that could bind to viral capsid proteins in their native conformation. Our observations suggest that HECs may overcome the restriction of type specific immunity against HPV

Abstract P6-08-12: Understanding the etiology of osteopenia and osteoporosis in young breast cancer survivors compared to cancer-free women

Abstract Background: Our group previously reported that young breast cancer (BC) survivors have a higher risk of osteopenia/osteoporosis compared to their cancer-free peers. In order to develop successful interventions we need to understand the major contributing factors. Therefore, we investigated bone loss in young BC survivors by age at diagnosis, tumor characteristics and BC treatment compared to their cancer-free peers. Methods: We studied 775 women (211 BC survivors, 564 cancer-free) with familial risk of breast and/or ovarian cancer in the Breast and Ovarian Surveillance Service (BOSS) cohort at Johns Hopkins. Survivors were diagnosed with stage 0-III BC &amp;lt;5 years prior to enrollment. The comparison group was cancer-free women at enrollment. Osteopenia and osteoporosis were ascertained based on self-reported physician diagnosis in baseline and follow-up questionnaires. Prevalent cases of osteopenia or osteoporosis were excluded. Multivariable (MV)-adjusted Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) of osteopenia and/or osteoporosis among BC survivors compared to cancer-free women. BC survivors were stratified by age at diagnosis, estrogen-receptor (ER) tumor status, and BC treatment. MV models were adjusted for age, menopausal status, body mass index, physical activity, smoking, alcohol use, hormone replacement therapy and early oophorectomy. Results: Mean time from BC diagnosis to enrollment was 1.4 years for survivors and mean age at BC diagnosis was 47 years. At baseline, BC survivors were more likely to be slightly older, postmenopausal, and current vitamin D users and less likely to have had an early bilateral oophorectomy compared to cancer-free women. During a mean follow-up time of 5.7 years, 66% of BC survivors and 54% of cancer-free women reported having ≥1 bone density exam and 112 incident cases of osteopenia/osteoporosis were identified (75% osteopenia only). BC survivors diagnosed at age ≤50 years had a 2-fold increased risk of osteopenia/osteoporosis compared to cancer-free women (HR=2.05, 95% CI=1.24-3.40). Risk of bone loss was similar among survivors with ER-positive tumors compared to cancer-free women (HR=2.04, 95% CI=1.30-3.22). No association was observed for BC survivors treated with tamoxifen only or chemotherapy only. BC survivors treated with aromatase inhibitors (AIs) only had almost 3-fold increased risk of osteopenia/osteoporosis compared to cancer-free women (HR=2.92, 95% CI=1.38-6.17). BC survivors treated with chemotherapy + tamoxifen and chemotherapy + AIs had over 2- and 4-fold increased risk of osteopenia/osteoporosis compared to cancer-free women (HR=2.28, 95% CI=1.04-5.00; HR=4.09, 95% CI=1.99-8.42, respectively). Results suggest that risk of bone loss was highest within 5 years after BC diagnosis. Conclusion: Our results demonstrate that osteopenia/osteoporosis incidence is higher in BC survivors compared to cancer-free women and risk varies by age at diagnosis, ER-status and BC treatment. Our findings provide support for a baseline evaluation of bone density close to diagnosis in BC survivors with familial risk. Future studies are needed to address the frequency of monitoring among specific age and treatment groups. Citation Format: Ramin CA, May BJ, Roden RBS, McCullough M, Armstrong DK, Visvanathan K. Understanding the etiology of osteopenia and osteoporosis in young breast cancer survivors compared to cancer-free women [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-08-12.</jats:p