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Li S, Liang H, Zhao SH, Yang XY, Guo Z. Recent progress in pneumococcal protein vaccines. Front Immunol 2023; 14:1278346. [PMID: 37818378 PMCID: PMC10560988 DOI: 10.3389/fimmu.2023.1278346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 09/07/2023] [Indexed: 10/12/2023] Open
Abstract
Pneumococcal infections continue to pose a significant global health concern, necessitating the development of effective vaccines. Despite the progress shown by pneumococcal polysaccharide and conjugate vaccines, their limited coverage and the emergence of non-vaccine serotypes have highlighted the need for alternative approaches. Protein-based pneumococcal vaccines, targeting conserved surface proteins of Streptococcus pneumoniae, have emerged as a promising strategy. In this review, we provide an overview of the advancements made in the development of pneumococcal protein vaccines. We discuss the key protein vaccine candidates, highlight their vaccination results in animal studies, and explore the challenges and future directions in protein-based pneumococcal vaccine.
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Affiliation(s)
- Sha Li
- Zhuhai Key Laboratory of Basic and Applied Research in Chinese Medicine, School of Bioengineering, Zunyi Medical University, Zhuhai, Guangdong, China
| | - Hangeri Liang
- Zhuhai Key Laboratory of Basic and Applied Research in Chinese Medicine, School of Bioengineering, Zunyi Medical University, Zhuhai, Guangdong, China
| | - Shui-Hao Zhao
- Center for Biological Science and Technology, Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai, Guangdong, China
| | - Xiao-Yan Yang
- Zhuhai Key Laboratory of Basic and Applied Research in Chinese Medicine, School of Bioengineering, Zunyi Medical University, Zhuhai, Guangdong, China
| | - Zhong Guo
- Center for Biological Science and Technology, Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai, Guangdong, China
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Afshari E, Ahangari Cohan R, Shams Nosrati MS, Mousavi SF. Development of a bivalent protein-based vaccine candidate against invasive pneumococcal diseases based on novel pneumococcal surface protein A in combination with pneumococcal histidine triad protein D. Front Immunol 2023; 14:1187773. [PMID: 37680628 PMCID: PMC10480505 DOI: 10.3389/fimmu.2023.1187773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 08/01/2023] [Indexed: 09/09/2023] Open
Abstract
Extensive efforts have been made toward improving effective strategies for pneumococcal vaccination, focusing on evaluating the potential of multivalent protein-based vaccines and overcoming the limitations of pneumococcal polysaccharide-based vaccines. In this study, we investigated the protective potential of mice co-immunization with the pneumococcal PhtD and novel rPspA proteins against pneumococcal sepsis infection. The formulations of each antigen alone or in combination were administered intraperitoneally with alum adjuvant into BALB/c mice three times at 14-day intervals. The production of antigen-specific IgG, IgG1 and IgG2a subclasses, and IL-4 and IFN-γ cytokines, were analyzed. Two in vitro complement- and opsonophagocytic-mediated killing activities of raised antibodies on day 42 were also assessed. Finally, the protection against an intraperitoneal challenge with 106 CFU/mouse of multi-drug resistance of Streptococcus pneumoniae ATCC49619 was investigated. Our findings showed a significant increase in the anti-PhtD and anti-rPspA sera IgG levels in the immunized group with the PhtD+rPspA formulation compared to each alone. Moreover, the results demonstrated a synergistic effect with a 6.7- and 1.3- fold increase in anti-PhtD and anti-rPspA IgG1, as well as a 5.59- and 1.08- fold increase in anti-PhtD and anti-rPspA IgG2a, respectively. Co-administration of rPspA+PhtD elicited a mixture of Th-2 and Th-1 immune responses, more towards Th-2. In addition, the highest complement-mediated killing activity was observed in the sera of the immunized group with PhtD+rPspA at 1/16 dilution, and the opsonophagocytic activity was increased from 74% to 86.3%. Finally, the survival rates showed that mice receiving the rPspA+PhtD formulation survived significantly longer (100%) than those receiving protein alone or PBS and exhibited the strongest clearance with a 2 log10 decrease in bacterial load in the blood 24h after challenge compared to the control group. In conclusion, the rPspA+PhtD formulation can be considered a promising bivalent serotype-independent vaccine candidate for protection against invasive pneumococcal infection in the future.
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Affiliation(s)
- Elnaz Afshari
- Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
- Department of Microbiology, Pasteur Institute of Iran, Tehran, Iran
| | - Reza Ahangari Cohan
- Department of Nanobiotechnology, New Technologies Research Group, Pasteur Institute of Iran, Tehran, Iran
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Leal JT, Primon-Barros M, de Carvalho Robaina A, Pizzutti K, Mott MP, Trentin DS, Dias CAG. Streptococcus pneumoniae serotype 19A from carriers and invasive disease: virulence gene profile and pathogenicity in a Galleria mellonella model. Eur J Clin Microbiol Infect Dis 2023; 42:399-411. [PMID: 36790530 DOI: 10.1007/s10096-023-04560-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 01/27/2023] [Indexed: 02/16/2023]
Abstract
PURPOSE This study aimed to evaluate and compare the presence of genes related to surface proteins between isolates of Streptococcus pneumoniae from healthy carriers (HC) and invasive pneumococcal disease (IPD) with a particular focus on serotype 19A. METHODS The presence of these genes was identified by real-time PCR. Subsequently, we employed the Galleria mellonella larval infection model to study their effect on pathogenicity in vivo. RESULTS The percentage of selected virulence genes was similar between the HC and IPD groups (p > 0.05), and the genes lytA, nanB, pavA, pcpA, phtA, phtB, phtE, rrgA, and sipA were all present in both groups. However, the virulence profile of the isolates differed individually between HC and IPD groups. The highest lethality in G. mellonella was for IPD isolates (p < 0.01), even when the virulence profile was the same as compared to the HC isolates or when the nanA, pspA, pspA-fam1, and pspC genes were not present. CONCLUSIONS The occurrence of the investigated virulence genes was similar between HC and IPD S. pneumoniae serotype 19A groups. However, the IPD isolates showed a higher lethality in the alternative G. mellonella model than the HC isolates, regardless of the virulence gene composition, indicating that other virulence factors may play a decisive role in virulence. Currently, this is the first report using the in vivo G. mellonella model to study the virulence of clinical isolates of S. pneumoniae.
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Affiliation(s)
- Josiane Trevisol Leal
- Laboratório de Microbiologia Molecular, Departamento de Ciências Básicas da Saúde, Programa de Pós-Graduação em Ciências da Saúde (PPGCS), Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Porto Alegre, Rio Grande Do Sul, Brasil
- Laboratório de Bacteriologia & Modelos Experimentais Alternativos, Departamento de Ciências Básicas da Saúde, Programa de Pós-Graduação em Biociências (PPGBIO), Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Porto Alegre, RS, Brasil
| | - Muriel Primon-Barros
- Laboratório de Microbiologia Molecular, Departamento de Ciências Básicas da Saúde, Programa de Pós-Graduação em Ciências da Saúde (PPGCS), Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Porto Alegre, Rio Grande Do Sul, Brasil
| | - Amanda de Carvalho Robaina
- Laboratório de Microbiologia Molecular, Departamento de Ciências Básicas da Saúde, Programa de Pós-Graduação em Ciências da Saúde (PPGCS), Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Porto Alegre, Rio Grande Do Sul, Brasil
| | - Kauana Pizzutti
- Laboratório de Microbiologia Molecular, Departamento de Ciências Básicas da Saúde, Programa de Pós-Graduação em Ciências da Saúde (PPGCS), Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Porto Alegre, Rio Grande Do Sul, Brasil
| | - Mariana Preussler Mott
- Laboratório de Microbiologia Molecular, Departamento de Ciências Básicas da Saúde, Programa de Pós-Graduação em Ciências da Saúde (PPGCS), Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Porto Alegre, Rio Grande Do Sul, Brasil
| | - Danielle Silva Trentin
- Laboratório de Bacteriologia & Modelos Experimentais Alternativos, Departamento de Ciências Básicas da Saúde, Programa de Pós-Graduação em Biociências (PPGBIO), Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Porto Alegre, RS, Brasil.
| | - Cícero Armídio Gomes Dias
- Laboratório de Microbiologia Molecular, Departamento de Ciências Básicas da Saúde, Programa de Pós-Graduação em Ciências da Saúde (PPGCS), Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Porto Alegre, Rio Grande Do Sul, Brasil
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Silva PH, Vázquez Y, Campusano C, Retamal-Díaz A, Lay MK, Muñoz CA, González PA, Kalergis AM, Bueno SM. Non-capsular based immunization approaches to prevent Streptococcus pneumoniae infection. Front Cell Infect Microbiol 2022; 12:949469. [PMID: 36225231 PMCID: PMC9548657 DOI: 10.3389/fcimb.2022.949469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Accepted: 09/02/2022] [Indexed: 12/02/2022] Open
Abstract
Streptococcus pneumoniae is a Gram-positive bacterium and the leading cause of bacterial pneumonia in children and the elderly worldwide. Currently, two types of licensed vaccines are available to prevent the disease caused by this pathogen: the 23-valent pneumococcal polysaccharide-based vaccine and the 7-, 10, 13, 15 and 20-valent pneumococcal conjugate vaccine. However, these vaccines, composed of the principal capsular polysaccharide of leading serotypes of this bacterium, have some problems, such as high production costs and serotype-dependent effectiveness. These drawbacks have stimulated research initiatives into non-capsular-based vaccines in search of a universal vaccine against S. pneumoniae. In the last decades, several research groups have been developing various new vaccines against this bacterium based on recombinant proteins, live attenuated bacterium, inactivated whole-cell vaccines, and other newer platforms. Here, we review and discuss the status of non-capsular vaccines against S. pneumoniae and the future of these alternatives in a post-pandemic scenario.
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Affiliation(s)
- Pedro H. Silva
- Millennium Institute on Immunology and Immunotherapy, Santiago, Chile
- Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Yaneisi Vázquez
- Millennium Institute on Immunology and Immunotherapy, Santiago, Chile
- Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Camilo Campusano
- Millennium Institute on Immunology and Immunotherapy, Santiago, Chile
- Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Angello Retamal-Díaz
- Departamento de Biotecnología, Facultad de Ciencias del Mar y Recursos Biológicos, Universidad de Antofagasta, Antofagasta, Chile
| | - Margarita K. Lay
- Departamento de Biotecnología, Facultad de Ciencias del Mar y Recursos Biológicos, Universidad de Antofagasta, Antofagasta, Chile
| | - Christian A. Muñoz
- Unidad de Microbiología, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Antofagasta, Chile
| | - Pablo A. González
- Millennium Institute on Immunology and Immunotherapy, Santiago, Chile
- Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Alexis M. Kalergis
- Millennium Institute on Immunology and Immunotherapy, Santiago, Chile
- Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Susan M. Bueno
- Millennium Institute on Immunology and Immunotherapy, Santiago, Chile
- Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
- *Correspondence: Susan M. Bueno,
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Gingerich AD, Mousa JJ. Diverse Mechanisms of Protective Anti-Pneumococcal Antibodies. Front Cell Infect Microbiol 2022; 12:824788. [PMID: 35155281 PMCID: PMC8834882 DOI: 10.3389/fcimb.2022.824788] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 01/11/2022] [Indexed: 02/05/2023] Open
Abstract
The gram-positive bacterium Streptococcus pneumoniae is a leading cause of pneumonia, otitis media, septicemia, and meningitis in children and adults. Current prevention and treatment efforts are primarily pneumococcal conjugate vaccines that target the bacterial capsule polysaccharide, as well as antibiotics for pathogen clearance. While these methods have been enormously effective at disease prevention and treatment, there has been an emergence of non-vaccine serotypes, termed serotype replacement, and increasing antibiotic resistance among these serotypes. To combat S. pneumoniae, the immune system must deploy an arsenal of antimicrobial functions. However, S. pneumoniae has evolved a repertoire of evasion techniques and is able to modulate the host immune system. Antibodies are a key component of pneumococcal immunity, targeting both the capsule polysaccharide and protein antigens on the surface of the bacterium. These antibodies have been shown to play a variety of roles including increasing opsonophagocytic activity, enzymatic and toxin neutralization, reducing bacterial adherence, and altering bacterial gene expression. In this review, we describe targets of anti-pneumococcal antibodies and describe antibody functions and effectiveness against S. pneumoniae.
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Affiliation(s)
- Aaron D. Gingerich
- Center for Vaccines and Immunology, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
| | - Jarrod J. Mousa
- Center for Vaccines and Immunology, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
- Department of Biochemistry and Molecular Biology, Franklin College of Arts and Sciences, University of Georgia, Athens, GA, United States
- *Correspondence: Jarrod J. Mousa,
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Wang Y, Xia L, Wang G, Lu H, Wang H, Luo S, Zhang T, Gao S, Huang J, Min X. Subcutaneous immunization with the fusion protein ΔA146Ply-SP0148 confers protection against Streptococcus pneumoniae infection. Microb Pathog 2021; 162:105325. [PMID: 34848296 DOI: 10.1016/j.micpath.2021.105325] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Revised: 11/19/2021] [Accepted: 11/26/2021] [Indexed: 12/30/2022]
Abstract
Pneumococcal SP0148 and pneumolysin (Ply) derivatives are important vaccine candidates. SP0148 is a conserved lipoprotein with high immunogenicity produced by Streptococcus pneumoniae. We have previously demonstrated that SP0148 can confer protection against fatal infections caused by S. pneumoniae. ΔA146Ply is a noncytotoxic mutant of Ply that retains the TLR4 agonistic effect and has mucosal and subcutaneous adjuvant activities suggested to induce protective immunity against S. pneumoniae infection. In this study, we constructed the fusion protein ΔA146Ply-SP0148, composed of ΔA146Ply and SP0148, and evaluated the immunoprotective effect of the fusion protein. When mice were subcutaneously immunized with the fusion protein ΔA146Ply-SP0148, high levels of anti-ΔA146Ply and anti-SP0148 IgG antibodies were induced in the serum. Specific antibodies can bind to a variety of different serotypes of S. pneumoniae. Compared with mice immunized with ΔA146Ply and SP0148 alone, mice immunized subcutaneously with the fusion protein ΔA146Ply-SP0148 with Al(OH)3 had a higher survival rate when challenged by a lethal dose of S. pneumoniae, and they also had significantly lower lung bacterial loads and milder lung inflammation. In addition, mice immunized subcutaneously with the fusion protein ΔA146Ply-SP0148 stimulated strong Th1, Th2, and Th17 cell responses. In summary, these results suggest that subcutaneous immunization with the ΔA146Ply-SP0148 fusion protein can protect mice against fatal pneumococcal infection and lung infection. The fusion protein ΔA146ply-SP0148 can be a new pneumococcal vaccine target.
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Affiliation(s)
- Yao Wang
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Lingyin Xia
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Guangli Wang
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Huifang Lu
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Hui Wang
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Shilu Luo
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Tao Zhang
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Song Gao
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Jian Huang
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, China.
| | - Xun Min
- Department of Laboratory Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, China.
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André GO, Borges MT, Assoni L, Ferraz LFC, Sakshi P, Adamson P, Gordon DL, Ogunniyi AD, Venter H, Converso TR, Darrieux M. Protective role of PhtD and its amino and carboxyl fragments against pneumococcal sepsis. Vaccine 2021; 39:3626-3632. [PMID: 34045100 DOI: 10.1016/j.vaccine.2021.04.068] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 04/27/2021] [Accepted: 04/30/2021] [Indexed: 11/28/2022]
Abstract
The implementation of polysaccharide-based vaccines has massively reduced the incidence of invasive pneumococcal diseases. However, there is great concern regarding serotype replacement and the increase in antibiotic resistant strains expressing non-vaccine capsular types. In addition, conjugate vaccines have high production costs, a limiting factor for their implementation in mass immunization programs in developing countries. These limitations have prompted the development of novel vaccine strategies for prevention of Streptococcus pneumoniae infections. The use of conserved pneumococcal antigens such as recombinant proteins or protein fragments presents an interesting serotype-independent alternative. Pht is a family of surface-exposed proteins which have been evaluated as potential vaccine candidates with encouraging results. The present work investigated the immune responses elicited by subcutaneous immunization of mice with the polyhistidine triad protein D (PhtD) and its amino and carboxyl terminal fragments. The proteins were immunogenic and protective against pneumococcal sepsis in mice. Antibodies raised against PhtD increased complement C3b deposition on the pneumococcal surface, mainly mediated by the alternative pathway. Sera from mice immunized with PhtD and PhtD_Cter promoted an increase in bacterial uptake by mouse phagocytes. The interaction of PhtD with the complement system regulator factor H was investigated in silico and in vitro by ELISA and western blot, confirming PhtD as a factor-H binding protein. Our results support the inclusion of PhtD and more specifically, its C-terminal fragment in a multicomponent serotype independent vaccine and suggests a role for the complement system in PhtD-mediated protection.
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Affiliation(s)
- Greiciely O André
- Laboratório de Microbiologia Molecular e Clínica, Universidade São Francisco, Bragança Paulista, Brazil
| | - Mayara T Borges
- Laboratório de Microbiologia Molecular e Clínica, Universidade São Francisco, Bragança Paulista, Brazil
| | - Lucas Assoni
- Laboratório de Microbiologia Molecular e Clínica, Universidade São Francisco, Bragança Paulista, Brazil
| | - Lucio F C Ferraz
- Laboratório de Microbiologia Molecular e Clínica, Universidade São Francisco, Bragança Paulista, Brazil
| | - Piplani Sakshi
- College of Medicine and Public Health. Flinders University, Adelaide, South Australia, Australia
| | - Penelope Adamson
- Department of Microbiology and Infectious Diseases, Flinders University, Adelaide, South Australia, Australia
| | - David L Gordon
- Department of Microbiology and Infectious Diseases, Flinders University, Adelaide, South Australia, Australia
| | - Abiodun D Ogunniyi
- Australian Centre for Antimicrobial Resistance Ecology, School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, South Australia, Australia
| | - Henrietta Venter
- Health and Biomedical Innovation, Clinical and Health Sciences, University of South Australia, Adelaide, South Australia, Australia
| | - Thiago R Converso
- Laboratório de Microbiologia Molecular e Clínica, Universidade São Francisco, Bragança Paulista, Brazil
| | - Michelle Darrieux
- Laboratório de Microbiologia Molecular e Clínica, Universidade São Francisco, Bragança Paulista, Brazil.
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Broadly Reactive Human Monoclonal Antibodies Targeting the Pneumococcal Histidine Triad Protein Protect against Fatal Pneumococcal Infection. Infect Immun 2021; 89:IAI.00747-20. [PMID: 33649050 PMCID: PMC8091081 DOI: 10.1128/iai.00747-20] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 02/21/2021] [Indexed: 02/07/2023] Open
Abstract
Streptococcus pneumoniae remains a leading cause of bacterial pneumonia despite the widespread use of vaccines. While vaccines are effective at reducing the incidence of most serotypes included in vaccines, a rise in infection due to nonvaccine serotypes and moderate efficacy against some vaccine serotypes have contributed to high disease incidence. Streptococcus pneumoniae remains a leading cause of bacterial pneumonia despite the widespread use of vaccines. While vaccines are effective at reducing the incidence of most serotypes included in vaccines, a rise in infection due to nonvaccine serotypes and moderate efficacy against some vaccine serotypes have contributed to high disease incidence. Additionally, numerous isolates of S. pneumoniae are antibiotic or multidrug resistant. Several conserved pneumococcal proteins prevalent in the majority of serotypes have been examined for their potential as vaccines in preclinical and clinical trials. An additional, yet-unexplored tool for disease prevention and treatment is the use of human monoclonal antibodies (MAbs) targeting conserved pneumococcal proteins. Here, we isolated the first human MAbs (PhtD3, PhtD6, PhtD7, PhtD8, and PspA16) against the pneumococcal histidine triad protein (PhtD) and the pneumococcal surface protein A (PspA), two conserved and protective antigens. MAbs to PhtD target diverse epitopes on PhtD, and MAb PspA16 targets the N-terminal segment of PspA. The PhtD-specific MAbs bind to multiple serotypes, while MAb PspA16 serotype breadth is limited. MAbs PhtD3 and PhtD8 prolong the survival of mice infected with pneumococcal serotype 3. Furthermore, MAb PhtD3 prolongs the survival of mice in intranasal and intravenous infection models with pneumococcal serotype 4 and in mice infected with pneumococcal serotype 3 when administered 24 h after pneumococcal infection. All PhtD and PspA MAbs demonstrate opsonophagocytic activity, suggesting a potential mechanism of protection. Our results identify new human MAbs for pneumococcal disease prevention and treatment and identify epitopes on PhtD and PspA recognized by human B cells.
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