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Losada C, Samaha H, Scherer EM, Kazzi B, Khalil L, Ofotokun I, Rouphael N. Efficacy and Durability of Immune Response after Receipt of HPV Vaccines in People Living with HIV. Vaccines (Basel) 2023; 11:1067. [PMID: 37376456 DOI: 10.3390/vaccines11061067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 05/24/2023] [Accepted: 05/31/2023] [Indexed: 06/29/2023] Open
Abstract
People living with HIV (PLH) experience higher rates of HPV infection as well as an increased risk of HPV-related disease, including malignancies. Although they are considered a high-priority group for HPV vaccination, there are limited data regarding the long-term immunogenicity and efficacy of HPV vaccines in this population. Seroconversion rates and geometric mean titers elicited by vaccination are lower in PLH compared to immunocompetent participants, especially in individuals with CD4 counts below 200 cells/mm3 and a detectable viral load. The significance of these differences is still unclear, as a correlate of protection has not been identified. Few studies have focused on demonstrating vaccine efficacy in PLH, with variable results depending on the age at vaccination and baseline seropositivity. Although waning humoral immunity for HPV seems to be more rapid in this population, there is evidence that suggests that seropositivity lasts at least 2-4 years following vaccination. Further research is needed to determine the differences between vaccine formulations and the impact of administrating additional doses on durability of immune protection.
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Affiliation(s)
- Cecilia Losada
- The Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, Emory University, Decatur, GA 30030, USA
| | - Hady Samaha
- The Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, Emory University, Decatur, GA 30030, USA
| | - Erin M Scherer
- The Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, Emory University, Decatur, GA 30030, USA
| | - Bahaa Kazzi
- The Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, Emory University, Decatur, GA 30030, USA
| | - Lana Khalil
- The Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, Emory University, Decatur, GA 30030, USA
| | - Ighovwerha Ofotokun
- Division of Infectious Diseases, Department of Medicine, Emory University, Atlanta, GA 30322, USA
| | - Nadine Rouphael
- The Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, Emory University, Decatur, GA 30030, USA
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Callegaro A, Karkada N, Aris E, Zahaf T. Vaccine clinical trials with dynamic borrowing of historical controls: Two retrospective studies. Pharm Stat 2023; 22:475-491. [PMID: 36606496 DOI: 10.1002/pst.2283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 11/29/2022] [Accepted: 12/03/2022] [Indexed: 01/07/2023]
Abstract
Traditional vaccine efficacy trials usually use fixed designs with fairly large sample sizes. Recruiting a large number of subjects requires longer time and higher costs. Furthermore, vaccine developers are more than ever facing the need to accelerate vaccine development to fulfill the public's medical needs. A possible approach to accelerate development is to use the method of dynamic borrowing of historical controls in clinical trials. In this paper, we evaluate the feasibility and the performance of this approach in vaccine development by retrospectively analyzing two real vaccine studies: a relatively small immunological trial (typical early phase study) and a large vaccine efficacy trial (typical Phase 3 study) assessing prophylactic human papillomavirus vaccine. Results are promising, particularly for early development immunological studies, where the adaptive design is feasible, and control of type I error is less relevant.
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Affiliation(s)
| | | | - Emmanuel Aris
- Department of Biostatistics, GSK, Rixensart, Belgium
| | - Toufik Zahaf
- Department of Biostatistics, GSK, Rixensart, Belgium
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Chambers C, Gillis J, Lindsay J, Benoit AC, Kendall CE, Kroch A, Grewal R, Loutfy M, Mah A, O'Brien K, Ogilvie G, Raboud J, Rachlis A, Rachlis B, Yeung A, Yudin MH, Burchell AN. Low human papillomavirus vaccine uptake among women engaged in HIV care in Ontario, Canada. Prev Med 2022; 164:107246. [PMID: 36075492 DOI: 10.1016/j.ypmed.2022.107246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 08/08/2022] [Accepted: 09/02/2022] [Indexed: 10/31/2022]
Abstract
Women living with HIV are at higher risk for human papillomavirus (HPV)-related dysplasia and cancers and thus are prioritized for HPV vaccination. We measured HPV vaccine uptake among women engaged in HIV care in Ontario, Canada, and identified socio-demographic, behavioural, and clinical characteristics associated with HPV vaccination. During annual interviews from 2017 to 2020, women participating in a multi-site, clinical HIV cohort responded to a cross-sectional survey on HPV vaccine knowledge and receipt. We used logistic regression to derive age-adjusted odds ratios and 95% confidence intervals (CI) for factors associated with self-reported vaccine initiation (≥1 dose) or series completion (3 doses). Among 591 women (median age = 48 years; interquartile range = 40-56 years), 13.2% (95%CI = 10.5-15.9%) had received ≥1 dose. Of those vaccinated, 64.6% had received 3 doses. Vaccine initiation (≥1 dose) was significantly higher among women aged 20-29 years at 31.0% but fell to 13.9% in those aged 30-49 years and < 10% in those aged ≥50 years. After age adjustment, vaccine initiation was significantly associated with being employed (vs. unemployed but seeking work), income $40,000-$59,999 (vs. <$20,000), being married/common-law (vs. single), living with children, immigrating to Canada >5 years ago (vs. immigrating ≤5 years ago), never smoking (vs. currently smoking), and being in HIV care longer (per 10 years). Similar factors were identified for series completion (3 doses). HPV vaccine uptake remains low among women living with HIV in our cohort despite regular engagement in care. Recommendations for improving uptake include education of healthcare providers, targeted community outreach, and public funding of HPV vaccination.
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Affiliation(s)
- Catharine Chambers
- University of Toronto, Toronto, Canada; St. Michael's Hospital, Unity Health Toronto, Toronto, Canada
| | | | - Joanne Lindsay
- St. Michael's Hospital, Unity Health Toronto, Toronto, Canada
| | - Anita C Benoit
- University of Toronto, Toronto, Canada; Women's College Research Institute, Toronto, Canada
| | - Claire E Kendall
- Bruyère Research Institute, Ottawa, Canada; Faculty of Medicine, University of Ottawa, Ottawa, Canada; ICES (formerly Institute for Clinical Evaluative Sciences), Toronto, Canada
| | - Abigail Kroch
- University of Toronto, Toronto, Canada; Ontario HIV Treatment Network, Toronto, Canada; Public Health Ontario, Toronto, Canada
| | - Ramandip Grewal
- St. Michael's Hospital, Unity Health Toronto, Toronto, Canada; Public Health Ontario, Toronto, Canada
| | - Mona Loutfy
- Women's College Research Institute, Toronto, Canada
| | - Ashley Mah
- St. Michael's Hospital, Unity Health Toronto, Toronto, Canada
| | | | - Gina Ogilvie
- University of British Columbia, Vancouver, Canada
| | - Janet Raboud
- University of Toronto, Toronto, Canada; Toronto General Hospital Research Institute, University Health Network, Toronto, Canada
| | | | - Beth Rachlis
- University of Toronto, Toronto, Canada; ICES (formerly Institute for Clinical Evaluative Sciences), Toronto, Canada
| | - Anna Yeung
- St. Michael's Hospital, Unity Health Toronto, Toronto, Canada
| | - Mark H Yudin
- St. Michael's Hospital, Unity Health Toronto, Toronto, Canada
| | - Ann N Burchell
- University of Toronto, Toronto, Canada; St. Michael's Hospital, Unity Health Toronto, Toronto, Canada.
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Staadegaard L, Rönn MM, Soni N, Bellerose ME, Bloem P, Brisson M, Maheu-Giroux M, Barnabas RV, Drolet M, Mayaud P, Dalal S, Boily MC. Immunogenicity, safety, and efficacy of the HPV vaccines among people living with HIV: A systematic review and meta-analysis. EClinicalMedicine 2022; 52:101585. [PMID: 35936024 PMCID: PMC9350866 DOI: 10.1016/j.eclinm.2022.101585] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 07/08/2022] [Accepted: 07/08/2022] [Indexed: 01/21/2023] Open
Abstract
Background Vaccines have been demonstrated to protect against high-risk human papillomavirus infection (HPV), including HPV-16/18, and cervical lesions among HIV negative women. However, their efficacy remains uncertain for people living with HIV (PLHIV).We systematically reviewed available evidence on HPV vaccine on immunological, virological, or other biological outcomes in PLHIV. Methods We searched five electronic databases (PubMed, Medline and Embase, clinicaltrials.gov and the WHO clinical trial database) for longitudinal prospective studies reporting immunogenicity, virological, cytological, histological, clinical or safety endpoints following prophylactic HPV vaccination among PLHIV. We included studies published by February 11th, 2021. We summarized results, assessed study quality, and conducted meta-analysis and subgroup analyses, where possible. Findings We identified 43 publications stemming from 18 independent studies (Ns =18), evaluating the quadrivalent (Ns =15), bivalent (Ns =4) and nonavalent (Ns =1) vaccines. A high proportion seroconverted for the HPV vaccine types. Pooled proportion seropositive by 28 weeks following 3 doses with the bivalent, quadrivalent, and nonavalent vaccines were 0.99 (95% confidence interval: 0.95-1.00, Ns =1), 0.99 (0.98-1.00, Ns =9), and 1.00 (0.99-1.00, Ns =1) for HPV-16 and 0.99 (0.96-1.00, Ns =1), 0.94 (0.91-0.96, Ns =9), and 1.00 (0.99-1.00, Ns =1) for HPV-18, respectively. Seropositivity remained high among people who received 3 doses despite some declines in antibody titers and lower seropositivity over time, especially for HPV-18, for the quadrivalent than the bivalent vaccine, and for HIV positive than negative individuals. Seropositivity for HPV-18 at 29-99 weeks among PLHIV was 0.72 (0.66-0.79, Ns =8) and 0.96 (0.92-0.99, Ns =2) after 3 doses of the quadrivalent and bivalent vaccine, respectively and 0.94 (0.90-0.98, Ns =3) among HIV-negative historical controls. Evidence suggests that the seropositivity after vaccination declines over time but it can lasts at least 2-4 years. The vaccines were deemed safe among PLHIV with few serious adverse events. Evidence of HPV vaccine efficacy against acquisition of HPV infection and/or associated disease from the eight trials available was inconclusive due to the low quality. Interpretation PLHIV have a robust and safe immune response to HPV vaccination. Antibody titers and seropositivity rates decline over time but remain high. The lack of a formal correlate of protection and efficacy results preclude definitive conclusions on the clinical benefits. Nevertheless, given the burden of HPV disease in PLHIV, although the protection may be shorter or less robust against HPV-18, the robust immune response suggests that PLHIV may benefit from receiving HPV vaccination after acquiring HIV. Better quality studies are needed to demonstrate the clinical efficacy among PLHIV. Funding World Health Organization. MRC Centre for Global Infectious Disease Analysis, Canadian Institutes of Health Research, UK Medical Research Council (MRC).
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Affiliation(s)
- Lisa Staadegaard
- Department of Infectious Diseases Epidemiology, Imperial College, London, United Kingdom
| | - Minttu M. Rönn
- Department of Global Health and Population, Harvard T.H. Chan School of Public Health, Boston, United States
| | - Nirali Soni
- Department of Infectious Diseases Epidemiology, Imperial College, London, United Kingdom
- Medical Research Council Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, London, United Kingdom
| | - Meghan E. Bellerose
- Department of Global Health and Population, Harvard T.H. Chan School of Public Health, Boston, United States
| | - Paul Bloem
- World Health Organization, Geneva, Switzerland
| | - Marc Brisson
- Laval University, Québec, Canada
- Centre de recherche du CHU de Québec-Université Laval, Canada
| | - Mathieu Maheu-Giroux
- Department of Epidemiology and Biostatistics, School of Population and Global Health, McGill University, Montreal, Canada
| | - Ruanne V. Barnabas
- Department of Global Health, Division of Allergy and Infectious Diseases, University of Washington, Seattle, WA, United States
| | - Melanie Drolet
- Centre de recherche du CHU de Québec-Université Laval, Canada
| | - Philippe Mayaud
- Faculty of Infectious & Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Shona Dalal
- World Health Organization, Geneva, Switzerland
| | - Marie-Claude Boily
- Department of Infectious Diseases Epidemiology, Imperial College, London, United Kingdom
- Medical Research Council Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, London, United Kingdom
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Advances in Infectious Disease Vaccine Adjuvants. Vaccines (Basel) 2022; 10:vaccines10071120. [PMID: 35891284 PMCID: PMC9316175 DOI: 10.3390/vaccines10071120] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 07/01/2022] [Accepted: 07/04/2022] [Indexed: 02/01/2023] Open
Abstract
Vaccines are one of the most significant medical interventions in the fight against infectious diseases. Since their discovery by Edward Jenner in 1796, vaccines have reduced the worldwide transmission to eradication levels of infectious diseases, including smallpox, diphtheria, hepatitis, malaria, and influenza. However, the complexity of developing safe and effective vaccines remains a barrier for combating many more infectious diseases. Immune stimulants (or adjuvants) are an indispensable factor in vaccine development, especially for inactivated and subunit-based vaccines due to their decreased immunogenicity compared to whole pathogen vaccines. Adjuvants are widely diverse in structure; however, their overall function in vaccine constructs is the same: to enhance and/or prolong an immunological response. The potential for adverse effects as a result of adjuvant use, though, must be acknowledged and carefully managed. Understanding the specific mechanisms of adjuvant efficacy and safety is a key prerequisite for adjuvant use in vaccination. Therefore, rigorous pre-clinical and clinical research into adjuvant development is essential. Overall, the incorporation of adjuvants allows for greater opportunities in advancing vaccine development and the importance of immune stimulants drives the emergence of novel and more effective adjuvants. This article highlights recent advances in vaccine adjuvant development and provides detailed data from pre-clinical and clinical studies specific to infectious diseases. Future perspectives into vaccine adjuvant development are also highlighted.
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Abouqal R, Beji M, Chakroun M, Marhoum El Filali K, Rammaoui J, Zaghden H. Trends in Adult and Elderly Vaccination: Focus on Vaccination Practices in Tunisia and Morocco. Front Public Health 2022; 10:903376. [PMID: 35844850 PMCID: PMC9286557 DOI: 10.3389/fpubh.2022.903376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 06/09/2022] [Indexed: 11/25/2022] Open
Abstract
Vaccine preventable diseases (VPDs) are a prevailing concern among the adult population, despite availability of vaccines. Unlike pediatric vaccination programs, adult vaccination programs lack the required reach, initiative, and awareness. Clinical studies and real-world data have proven that vaccines effectively reduce the disease burden of VPDs and increase life expectancy. In Tunisia and Morocco, the national immunization program (NIP) focuses more on pediatric vaccination and have limited vaccination programs for adults. However, some vaccination campaigns targeting adults are organized. For example, influenza vaccination campaigns prioritizing at risk adults which includes healthcare professionals, elderly, and patients with comorbidities. Women of childbearing age who have never been vaccinated or whose information is uncertain are recommended to receive tetanus vaccination. Tunisia NIP recommends rubella vaccine mainly for women of childbearing age, while in Morocco, national vaccination campaigns were organized for girls and women (up to 24 years of age) to eliminate rubella. Further, travelers from both countries are recommended to follow all requirements and recommendations in the travel destination. The objective of this manuscript is to provide an overview of the global disease burden of common VPDs including (but not limited to) meningococcal diseases, pneumococcal diseases, hepatitis, and influenza. The review also provides an overview of clinical data and guidelines/recommendations on adult vaccination practices, with special focus on Tunisia and Morocco. Some European and North American countries have concrete recommendations and strategies for adult vaccination to keep the VPDs in check. In Morocco and Tunisia, although, there are sporadic adult vaccination initiatives, the efforts still need upscaling and endorsements to boost vaccination awareness and uptake. There is a need to strengthen strategies in both countries to understand the disease burden and spread awareness. Additional studies are needed to generate economic evidence to support cost-effectiveness of vaccines. Integration of private and public healthcare systems may further improve vaccination uptake in adults.
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Affiliation(s)
- Redouane Abouqal
- Laboratory of Biostatistics, Clinical and Epidemiological Research, Faculty of Medicine and Pharmacy, Mohammed V University in Rabat, Rabat, Morocco
- Acute Medical Unit, Ibn Sina University Hospital, Rabat, Morocco
| | - Maher Beji
- Department of Internal Medicine, Military Hospital Bizerte, Bizerte, Tunisia
- Faculty of Medicine of Tunis, University El Manar, Tunis, Tunisia
- Tunisian Society of Tropical Medicine and Travel, Tunis, Tunisia
| | - Mohamed Chakroun
- Infectious Diseases Department, University Hospital, Monastir, Tunisia
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Immunogenicity of a Two-Dose Human Papillomavirus Vaccine Schedule in HIV-Infected Adolescents with Immune Reconstitution. Vaccines (Basel) 2022; 10:vaccines10010118. [PMID: 35062779 PMCID: PMC8779595 DOI: 10.3390/vaccines10010118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 01/10/2022] [Accepted: 01/11/2022] [Indexed: 12/10/2022] Open
Abstract
HIV-infected patients are at increased risk of human papillomavirus (HPV) acquisition and HPV-associated diseases. This study set out to determine whether a two-dose (2D) HPV vaccination schedule was sufficient in HIV-infected adolescents with immune reconstitution (IR) following antiretroviral treatment. Participants aged 9–15 years who had CD4 cell counts > 500 cells/mm3 and HIV-1 RNA < 40 copies/mL for at least one year were assigned to the 2D schedule, while older participants or those without IR received a three-dose (3D) schedule. Antibodies to HPV-16 and -18 were measured using a pseudovirion-based neutralization assay. A total of 96 subjects were enrolled; 31.3% and 68.7% received the 2D and 3D schedule, respectively. Of these, 66.7% and 57.6% of the 2D and 3D participants, respectively, were male. The seroconversion rates for HPV-16 and HPV-18 were 100% in all cases, except for HPV-18 in males who received the 3D schedule (97.4%). In males, the anti-HPV-16 geometric mean titers (GMTs) were 6859.3 (95% confidence interval, 4394.3–10,707.1) and 7011.1 (4648.8–10,573.9) in the 2D and 3D groups (p = 0.946), respectively, and the anti-HPV-18 GMTs were 2039.3 (1432.2–2903.8) and 2859.8 (1810.0–4518.4) in the 2D and 3D (p = 0.313) groups, respectively. In females, the anti-HPV-16 GMTs were 15,758.7 (8868.0–28,003.4) and 26,241.6 (16,972.7–40,572.3) in the 2D and 3D groups (p = 0.197), respectively, and the anti-HPV-18 GMTs were 5971.4 (3026.8–11,780.6) and 9993.1 (5950.8–16,781.1) in the 2D and 3D groups (p = 0.271), respectively. In summary, a 2D schedule is as immunogenic in young adolescents with IR as a 3D schedule in older subjects and those without IR.
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Castle PE, Einstein MH, Sahasrabuddhe VV. Cervical cancer prevention and control in women living with human immunodeficiency virus. CA Cancer J Clin 2021; 71:505-526. [PMID: 34499351 PMCID: PMC10054840 DOI: 10.3322/caac.21696] [Citation(s) in RCA: 68] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 08/07/2021] [Accepted: 08/10/2021] [Indexed: 12/16/2022] Open
Abstract
Despite being highly preventable, cervical cancer is the fourth most common cancer and cause of cancer death in women globally. In low-income countries, cervical cancer is often the leading cause of cancer-related morbidity and mortality. Women living with human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome are at a particularly high risk of cervical cancer because of an impaired immune response to human papillomavirus, the obligate cause of virtually all cervical cancers. Globally, approximately 1 in 20 cervical cancers is attributable to HIV; in sub-Saharan Africa, approximately 1 in 5 cervical cancers is due to HIV. Here, the authors provide a critical appraisal of the evidence to date on the impact of HIV disease on cervical cancer risk, describe key methodologic issues, and frame the key outstanding research questions, especially as they apply to ongoing global efforts for prevention and control of cervical cancer. Expanded efforts to integrate HIV care with cervical cancer prevention and control, and vice versa, could assist the global effort to eliminate cervical cancer as a public health problem.
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Affiliation(s)
- Philip E Castle
- Division of Cancer Prevention, National Cancer Institute, National Institutes of Health, Rockville, Maryland
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, Maryland
| | - Mark H Einstein
- Department of Obstetrics, Gynecology, and Reproductive Health, Rutgers New Jersey Medical School, Newark, New Jersey
| | - Vikrant V Sahasrabuddhe
- Division of Cancer Prevention, National Cancer Institute, National Institutes of Health, Rockville, Maryland
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Novel Production of Bovine Papillomavirus Pseudovirions in Tobacco Plants. Pathogens 2020; 9:pathogens9120996. [PMID: 33260725 PMCID: PMC7760623 DOI: 10.3390/pathogens9120996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 11/22/2020] [Accepted: 11/22/2020] [Indexed: 11/17/2022] Open
Abstract
Vaccine efficacy requires the production of neutralising antibodies which offer protection against the native virus. The current gold standard for determining the presence of neutralising antibodies is the pseudovirion-based neutralisation assay (PBNA). PBNAs utilise pseudovirions (PsVs), structures which mimic native virus capsids, but contain non-viral nucleic material. PsVs are currently produced in expensive cell culture systems, which limits their production, yet plant expression systems may offer cheaper, safer alternatives. Our aim was to determine whether plants could be used for the production of functional PsVs of bovine papillomavirus 1 (BPV1), an important causative agent of economically damaging bovine papillomas in cattle and equine sarcoids in horses and wild equids. BPV1 capsid proteins, L1 and L2, and a self-replicating reporter plasmid were transiently expressed in Nicotiana benthamiana to produce virus-like particles (VLPs) and PsVs. Strategies to enhance particle yields were investigated and optimised protocols were established. The PsVs' ability to infect mammalian cells and express their encapsidated reporter genes in vitro was confirmed, and their functionality as reagents in PBNAs was demonstrated through their neutralisation by several different antibodies. This is the first report of BPV PsVs expressed in plants and demonstrates the potential for the development of therapeutic veterinary vaccines in planta.
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