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Akkoyunlu M. State of pneumococcal vaccine immunity. Hum Vaccin Immunother 2024; 20:2336358. [PMID: 38567485 PMCID: PMC10993918 DOI: 10.1080/21645515.2024.2336358] [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: 01/26/2024] [Accepted: 03/26/2024] [Indexed: 04/04/2024] Open
Abstract
Like the other invasive encapsulated bacteria, Streptococcus pneumoniae is also covered with a polysaccharide structure. Infants and elderly are most vulnerable to the invasive and noninvasive diseases caused by S. pneumoniae. Although antibodies against polysaccharide capsule are efficient in eliminating S. pneumoniae, the T cell independent nature of the immune response against polysaccharide vaccines renders them weakly antigenic. The introduction of protein conjugated capsular polysaccharide vaccines helped overcome the weak immunogenicity of pneumococcal polysaccharides and decreased the incidence of pneumococcal diseases, especially in pediatric population. Conjugate vaccines elicit T cell dependent response which involve the interaction of specialized CD4+ T cells, called follicular helper T cells (Tfh) with germinal center B cells in secondary lymphoid organs. Despite their improved immunogenicity, conjugate vaccines still need to be administered three to four times in infants during the first 15 month of their life because they mount poor Tfh response. Recent studies revealed fundamental differences in the generation of Tfh cells between neonates and adults. As the portfolio of pneumococcal conjugate vaccines continues to increase, better understanding of the mechanisms of antibody development in different age groups will help in the development of pneumococcal vaccines tailored for different ages.
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Affiliation(s)
- Mustafa Akkoyunlu
- Division of Bacterial Allergenic and Parasitic Diseases, Center for Biologics Evaluation and Research, US Food and Drug Administration, Silver Spring, MD, USA
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2
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Vissers M, van de Garde MDB, He SWJ, Brandsen M, Hendriksen R, Nicolaie MA, van der Maas L, Meiring HD, van Els CACM, van Beek J, Rots NY. Quantity and Quality of Naturally Acquired Antibody Immunity to the Pneumococcal Proteome Throughout Life. J Infect Dis 2024:jiae255. [PMID: 38888894 DOI: 10.1093/infdis/jiae255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Accepted: 05/07/2024] [Indexed: 06/20/2024] Open
Abstract
BACKGROUND Young children and older adults are susceptible for invasive pneumococcal disease (IPD) caused by Streptococcus pneumoniae. Pneumococcal protein-specific antibodies play a protective role against IPD; however, not much is known about the pace of acquisition, maturation, and maintenance of these antibodies throughout life. METHODS Immunoglobulin G (IgG) and IgA levels, avidity, and/or specificity to the pneumococcal proteome in serum and saliva from healthy young children, adults, and older adults, with known carriage status, were measured by enzyme-linked immunosorbent assay (ELISA) and 2-dimensional western blotting against ΔcpsTIGR4. RESULTS Eleven-month-old children, the youngest age group tested, had the lowest pneumococcal proteome-specific IgG and IgA levels and avidity in serum and saliva, followed by 24-month-old children and were further elevated in adult groups. Among adult groups, the parents had the highest serum and saliva IgG and IgA antibody levels. In children, antibody levels and avidity correlated with daycare attendance and presence of siblings, posing as proxy for exposure and immunization. Immunodominance patterns slightly varied throughout life. CONCLUSIONS Humoral immunity against the pneumococcal proteome is acquired through multiple episodes of pneumococcal exposure. Low-level and low-avidity antiproteome antibody profiles in young children may contribute to their IPD susceptibility, while in overall antiproteome antibody-proficient older adults other factors likely play a role.
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Affiliation(s)
- Marloes Vissers
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | - Martijn D B van de Garde
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | - Samantha W J He
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | - Milou Brandsen
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | - Rosanne Hendriksen
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | - Mioara Alina Nicolaie
- Expertise Centre for Methodology and Information Services, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | - Larissa van der Maas
- Product Characterization and Formulation, Institute for Translational Vaccinology, Bilthoven, The Netherlands
| | - Hugo D Meiring
- Product Characterization and Formulation, Institute for Translational Vaccinology, Bilthoven, The Netherlands
| | - Cecile A C M van Els
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
- Infectious Diseases and Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Josine van Beek
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
| | - Nynke Y Rots
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
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Cinar MS, Niyas A, Avci FY. Serine-rich repeat proteins: well-known yet little-understood bacterial adhesins. J Bacteriol 2024; 206:e0024123. [PMID: 37975670 PMCID: PMC10810200 DOI: 10.1128/jb.00241-23] [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] [Indexed: 11/19/2023] Open
Abstract
Serine-rich-repeat proteins (SRRPs) are large mucin-like glycoprotein adhesins expressed by a plethora of pathogenic and symbiotic Gram-positive bacteria. SRRPs play major functional roles in bacterial-host interactions, like adhesion, aggregation, biofilm formation, virulence, and pathogenesis. Through their functional roles, SRRPs aid in the development of host microbiomes but also diseases like infective endocarditis, otitis media, meningitis, and pneumonia. SRRPs comprise shared domains across different species, including two or more heavily O-glycosylated long stretches of serine-rich repeat regions. With loci that can be as large as ~40 kb and can encode up to 10 distinct glycosyltransferases that specifically facilitate SRRP glycosylation, the SRRP loci makes up a significant portion of the bacterial genome. The significance of SRRPs and their glycans in host-microbe communications is becoming increasingly evident. Studies are beginning to reveal the glycosylation pathways and mature O-glycans presented by SRRPs. Here we review the glycosylation machinery of SRRPs across species and discuss the functional roles and clinical manifestations of SRRP glycosylation.
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Affiliation(s)
- Mukaddes S. Cinar
- Department of Biochemistry, Emory Vaccine Center, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Afaq Niyas
- Department of Biochemistry, Emory Vaccine Center, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Fikri Y. Avci
- Department of Biochemistry, Emory Vaccine Center, Emory University School of Medicine, Atlanta, Georgia, USA
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Milani B, dos Santos TW, Guerra MES, Oliveira S, Goulart C, André GO, Leite LCC, Converso TR, Darrieux M. Fusion of PspA to detoxified pneumolysin enhances pneumococcal vaccine coverage. PLoS One 2023; 18:e0291203. [PMID: 38096222 PMCID: PMC10721071 DOI: 10.1371/journal.pone.0291203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2023] [Accepted: 08/23/2023] [Indexed: 12/17/2023] Open
Abstract
Despite the implementation of conjugate vaccines in several countries, S. pneumoniae continues to pose a great burden worldwide, causing around 1 million annual deaths. Pneumococcal proteins have long been investigated as serotype-independent vaccines against this pathogen, with promising results. However, it is a consensus that one antigen alone will not be sufficient to provide long-term protection with wide coverage. Amongst the most well studied pneumococcal proteins are PspA and pneumolysin (Ply), two major virulence factors required by the bacterium for successful invasion of host tissues. PspA is highly immunogenic and protective, but it is structurally variable; pneumolysin is conserved among different pneumococci, but it is toxic to the host. To overcome these limitations, N-terminal PspA fragments have been genetically fused to non-toxic pneumolysin derivatives (PlD) to create PspA_PlD chimeras. Mouse immunization with these fusions confers protection against pneumococcal strains expressing heterologous PspAs, which correlates with antibody-induced complement C3 deposition on the surface of multiple pneumococcal strains. Analysis of mutant strains lacking PspA or Pneumolysin shows that both proteins contribute to the antibody-mediated enhancement in complement deposition induced by the fusion. These results expand previous data evaluating PspA_PlD and demonstrate that the fusion combines the protective traits of both proteins, inducing antibodies that efficiently promote complement deposition on multiple strains and cross-protection.
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Affiliation(s)
- Barbara Milani
- Laboratório de Microbiologia Molecular e Clínica, Universidade São Francisco, Bragança Paulista, Brazil
| | - Tanila Wood dos Santos
- Laboratório de Microbiologia Molecular e Clínica, Universidade São Francisco, Bragança Paulista, Brazil
- Programa de Pós-Graduação Interunidades em Biotecnologia-USP-IPT-IB, São Paulo, Brazil
| | | | - Sheila Oliveira
- Laboratório de Microbiologia Molecular e Clínica, Universidade São Francisco, Bragança Paulista, Brazil
| | - Cibelly Goulart
- Centro de Biotecnologia, Instituto Butantan, São Paulo, Brazil
| | - Greiciely O. André
- Laboratório de Microbiologia Molecular e Clínica, Universidade São Francisco, Bragança Paulista, Brazil
| | | | - 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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Akhmatova NK, Vorobyev DS, Petukhova ES, Semenova IB, Yakovleva IV, Gavrilova NF, Zaitsev AE, Akhmatova EA, Volokh YV, Leonova AY, Poddubikov AV, Kurbatova EA. Recombinant Pneumolysin of Pneumococci Induces TLR4 Expression and Maturation of Dendritic Cells In Vitro. Bull Exp Biol Med 2023; 176:191-193. [PMID: 38191877 DOI: 10.1007/s10517-024-05993-5] [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: 04/27/2023] [Indexed: 01/10/2024]
Abstract
Pneumolysin (Ply) is a target for the development of serotype-independent pneumococcal vaccines, an important condition for the efficacy of which is their ability to activate innate immunity with the subsequent formation of adaptive immunity. In this study, the ability of recombinant full-length Ply (rPly) of pneumococci to induce TLR expression and maturation of dendritic cells generated from mouse bone marrow was evaluated. It was shown that rPly in vitro increased the number of dendritic cells expressing Toll-like receptor 4 (TLR4) on the membrane. rPly caused maturation of dendritic cells generated from mouse bone marrow, which manifested in a decrease in the number of progenitor cells (CD34), an increase in the number of cells expressing the adhesion molecule CD38, costimulatory molecules CD80 and CD86, molecules of terminal differentiation of dendritic cells CD83, as well as molecules of antigenic presentation of the major histocompatibility complex class II.
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Affiliation(s)
- N K Akhmatova
- I. I. Mechnikov Research Institute of Vaccines and Sera, Moscow, Russia
| | - D S Vorobyev
- I. I. Mechnikov Research Institute of Vaccines and Sera, Moscow, Russia
| | - E S Petukhova
- I. I. Mechnikov Research Institute of Vaccines and Sera, Moscow, Russia
| | - I B Semenova
- I. I. Mechnikov Research Institute of Vaccines and Sera, Moscow, Russia
| | - I V Yakovleva
- I. I. Mechnikov Research Institute of Vaccines and Sera, Moscow, Russia
| | - N F Gavrilova
- I. I. Mechnikov Research Institute of Vaccines and Sera, Moscow, Russia
| | - A E Zaitsev
- I. I. Mechnikov Research Institute of Vaccines and Sera, Moscow, Russia
| | - E A Akhmatova
- I. I. Mechnikov Research Institute of Vaccines and Sera, Moscow, Russia
| | - Yu V Volokh
- I. I. Mechnikov Research Institute of Vaccines and Sera, Moscow, Russia
| | - A Yu Leonova
- I. I. Mechnikov Research Institute of Vaccines and Sera, Moscow, Russia
| | - A V Poddubikov
- I. I. Mechnikov Research Institute of Vaccines and Sera, Moscow, Russia
| | - E A Kurbatova
- I. I. Mechnikov Research Institute of Vaccines and Sera, Moscow, Russia.
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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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Yokota SI, Tsukamoto N, Sato T, Ohkoshi Y, Yamamoto S, Ogasawara N. Serotype replacement and an increase in non-encapsulated isolates among community-acquired infections of Streptococcus pneumoniae during post-vaccine era in Japan. IJID REGIONS 2023; 8:105-110. [PMID: 37554357 PMCID: PMC10404989 DOI: 10.1016/j.ijregi.2023.07.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 07/05/2023] [Accepted: 07/06/2023] [Indexed: 08/10/2023]
Abstract
OBJECTIVES It is feared that the serotype replacement of Streptococcus pneumoniae occurred by the introduction of pneumococcal vaccines as periodical inoculation leads to reduced efficacy of the approved vaccines and altered antimicrobial susceptibility. METHODS We determined serotypes of 351 S. pneumoniae isolates collected at a commercial clinical laboratory in Hokkaido prefecture, Japan, from December 2018 to February 2019 by using the polymerase chain reaction procedure of the US Centers for Disease Control and Prevention. Antimicrobial susceptibility and resistance gene profiles were also examined. RESULTS Vaccine coverage rates were 7.9% for 13-valent conjugate vaccine, and 32.5% for 23-valent polysaccharide vaccine, respectively. Non-typable strains were 19.7%. cpsA-positive isolates (group I), and null capsule clade (NCC)1, NCC2 and NCC3 (group II) comprised 31.3%, 28.4%, 32.8%, and 7.5% of the 69 non-typable strains, respectively. No penicillin-resistant/intermediate isolates were found; however, serotypes 35B and 15A/F showed low susceptibility to β-lactams. Only five strains (1.4%) were levofloxacin-resistant, and all were from the older persons, and three strains were serotype 35B. CONCLUSION The progression of serotype replacement in non-invasive pneumococcal infections has occurred during the post-vaccine era in Japan, and non-encapsulated isolates, such as NCC, have increased. Antimicrobial susceptibility is not worsened.
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Affiliation(s)
- Shin-ichi Yokota
- Department of Microbiology, Sapporo Medical University School of Medicine, Sapporo, Japan
| | | | - Toyotaka Sato
- Laboratory of Veterinary Hygiene, Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Japan
- Graduate School of Infectious Diseases, Hokkaido University, Sapporo, Japan
- One Health Research Center, Hokkaido University, Sapporo, Japan
| | - Yasuo Ohkoshi
- Department of Microbiology, Sapporo Medical University School of Medicine, Sapporo, Japan
- Department of Clinical Laboratory, NTT Medical Center Sapporo, Sapporo, Japan
| | - Soh Yamamoto
- Department of Microbiology, Sapporo Medical University School of Medicine, Sapporo, Japan
| | - Noriko Ogasawara
- Department of Microbiology, Sapporo Medical University School of Medicine, Sapporo, Japan
- Department of Otolaryngology-Head and Neck Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan
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8
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Duke JA, Avci FY. Emerging vaccine strategies against the incessant pneumococcal disease. NPJ Vaccines 2023; 8:122. [PMID: 37591986 PMCID: PMC10435554 DOI: 10.1038/s41541-023-00715-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 08/01/2023] [Indexed: 08/19/2023] Open
Abstract
The incidence of invasive pneumococcal disease (IPD) caused by infection with the pathogen Streptococcus pneumoniae (Spn) has been on a downward trend for decades due to worldwide vaccination programs. Despite the clinical successes observed, the Center for Disease Control (CDC) reports that the continued global burden of S. pneumoniae will be in the millions each year, with a case-fatality rate hovering around 5%. Thus, it is a top priority to continue developing new Spn vaccination strategies to harness immunological insight and increase the magnitude of protection provided. As emphasized by the World Health Organization (WHO), it is also crucial to broaden the implementation of vaccines that are already obtainable in the clinical setting. This review focuses on the immune mechanisms triggered by existing pneumococcal vaccines and provides an overview of the current and upcoming clinical strategies being employed. We highlight the associated challenges of serotype selectivity and using pneumococcal-derived proteins as alternative vaccine antigens.
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Affiliation(s)
- Jeremy A Duke
- Sanofi, Suite 300, 2501 Discovery Drive, Orlando, FL, 32826, USA
| | - Fikri Y Avci
- Department of Biochemistry, Emory Vaccine Center, Emory University School of Medicine, Atlanta, GA, 30322, USA.
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Aceil J, Venkat A, Pan E, Kannan N, Avci FY. Prevalence and Homology of the Pneumococcal Serine-Rich Repeat Protein at the Global Scale. Microbiol Spectr 2023; 11:e0325222. [PMID: 36995217 PMCID: PMC10269691 DOI: 10.1128/spectrum.03252-22] [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: 08/17/2022] [Accepted: 03/09/2023] [Indexed: 03/31/2023] Open
Abstract
Pneumococcal pneumonia remains a WHO high-priority disease despite multivalent conjugate vaccines administered in clinical practice worldwide. A protein-based, serotype-independent vaccine has long-promised comprehensive coverage of most clinical isolates of the pneumococcus. Along with numerous pneumococcal surface protein immunogens, the pneumococcal serine-rich repeat protein (PsrP) has been investigated as a potential vaccine target due to its surface exposure and functions toward bacterial virulence and lung infection. Three critical criteria for its vaccine potential - the clinical prevalence, serotype distribution, and sequence homology of PsrP - have yet to be well characterized. Here, we used genomes of 13,454 clinically isolated pneumococci from the Global Pneumococcal Sequencing project to investigate PsrP presence among isolates, distribution among serotypes, and interrogate its homology as a protein across species. These isolates represent all age groups, countries worldwide, and types of pneumococcal infection. We found PsrP present in at least 50% of all isolates across all determined serotypes and nontypeable (NT) clinical isolates. Using a combination of peptide matching and HMM profiles built on full-length and individual PsrP domains, we identified novel variants that expand PsrP diversity and prevalence. We also observed sequence variability in its basic region (BR) between isolates and serotypes. PsrP has a strong vaccine potential due to its breadth of coverage, especially in nonvaccine serotypes (NVTs) when exploiting its regions of conservation in vaccine design. IMPORTANCE An updated outlook on PsrP prevalence and serotype distribution sheds new light on the comprehensiveness of a PsrP-based protein vaccine. The protein is present in all vaccine serotypes and highly present in the next wave of potentially disease-causing serotypes not included in the current multivalent conjugate vaccines. Furthermore, PsrP is strongly correlated with clinical isolates harboring pneumococcal disease as opposed to pneumococcal carriage. PsrP is also highly present in strains and serotypes from Africa, where the need for a protein-based vaccine is the greatest, giving new reasoning to pursue PsrP as a protein vaccine.
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Affiliation(s)
- Javid Aceil
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Aarya Venkat
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Eric Pan
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Natarajan Kannan
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Fikri Y. Avci
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
- Department of Biochemistry, Emory Vaccine Center, Emory University School of Medicine, Atlanta, Georgia, USA
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Afshari E, Cohan RA, Sotoodehnejadnematalahi F, Mousavi SF. In-silico design and evaluation of an epitope-based serotype-independent promising vaccine candidate for highly cross-reactive regions of pneumococcal surface protein A. J Transl Med 2023; 21:13. [PMID: 36627666 PMCID: PMC9830136 DOI: 10.1186/s12967-022-03864-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 12/29/2022] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND The pathogenicity of pneumococcus with high morbidity, mortality, and multi-drug resistance patterns has been increasing. The limited coverage of the licensed polysaccharide-based vaccines and the replacement of the non-vaccine serotypes are the main reasons for producing a successful serotype-independent vaccine. Pneumococcal surface protein A (PspA) is an extremely important virulence factor and an interesting candidate for conserved protein-based pneumococcal vaccine classified into two prominent families containing five clades. PspA family-elicited immunity is clade-dependent, and the level of the PspA cross-reactivity is restricted to the same family. METHODS To cover and overcome the clade-dependent immunity of the PspAs in this study, we designed and tested a PspA1-5c+p vaccine candidate composed of the highest immunodominant coverage of B- and T-cell epitope truncated domain of each clade focusing on two cross-reactive B and C regions of the PspAs. The antigenicity, toxicity, physicochemical properties, 3D structure prediction, stability and flexibility of the designed protein using molecular dynamic (MD) simulation, molecular docking of the construct withHLADRB1*(01:01) and human lactoferrin N-lop, and immune simulation were assessed using immunoinformatics tools. In the experimental section, after intraperitoneal immunization of the mice with Alum adjuvanted recombinant PspA1-5c+p, we evaluated the immune response, cross-reactivity, and functionality of the Anti-PspA1-5c+p antibody using ELISA, Opsonophagocytic killing activity, and serum bactericidal assay. RESULTS For the first time, this work suggested a novel PspA-based vaccine candidate using immunoinformatics tools. The designed PspA1-5c+p protein is predicted to be highly antigenic, non-toxic, soluble, stable with low flexibility in MD simulation, and able to stimulate both humoral and cellular immune responses. The designed protein also could interact strongly with HLADRB1*(01:01) and human lactoferrin N-lop in the docking study. Our immunoinformatics predictions were validated using experimental data. Results showed that the anti-PspA1-5c+p IgG not only had a high titer with strong and same cross-reactivity coverage against all pneumococcal serotypes used but also had high and effective bioactivity for pneumococcal clearance using complement system and phagocytic cells. CONCLUSION Our findings elucidated the potential application of the PspA1-5c+p vaccine candidate as a serotype-independent pneumococcal vaccine with a strong cross-reactivity feature. Further in-vitro and in-vivo investigations against other PspA clades should be performed to confirm the full protection of the PspA1-5c+p vaccine candidate.
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Affiliation(s)
- Elnaz Afshari
- grid.411463.50000 0001 0706 2472Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
| | - Reza Ahangari Cohan
- grid.420169.80000 0000 9562 2611Department of Nanobiotechnology, New Technologies Research Group, Pasteur Institute of Iran, Tehran, Iran
| | - Fattah Sotoodehnejadnematalahi
- grid.411463.50000 0001 0706 2472Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
| | - Seyed Fazlollah Mousavi
- grid.420169.80000 0000 9562 2611Department of Microbiology, Pasteur Institute of Iran, 69 Pasteur Ave., Tehran, 13164 Iran
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