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De Pascalis R, Bhargava V, Espich S, Wu TH, Gelhaus HC, Elkins KL. In vivo and in vitro immune responses against Francisella tularensis vaccines are comparable among Fischer 344 rat substrains. Front Microbiol 2023; 14:1224480. [PMID: 37547680 PMCID: PMC10400713 DOI: 10.3389/fmicb.2023.1224480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 06/15/2023] [Indexed: 08/08/2023] Open
Abstract
Identifying suitable animal models and standardizing preclinical methods are important for the generation, characterization, and development of new vaccines, including those against Francisella tularensis. Non-human primates represent an important animal model to evaluate tularemia vaccine efficacy, and the use of correlates of vaccine-induced protection may facilitate bridging immune responses from non-human primates to people. However, among small animals, Fischer 344 rats represent a valuable resource for initial studies to evaluate immune responses, to identify correlates of protection, and to screen novel vaccines. In this study, we performed a comparative analysis of three Fischer rat substrains to determine potential differences in immune responses, to evaluate methods used to quantify potential correlates of protection, and to evaluate protection after vaccination. To this end, we took advantage of data previously generated using one of the rat substrains by evaluating two live vaccines, LVS and F. tularensis SchuS4-ΔclpB (ΔclpB). We compared immune responses after primary vaccination, adaptive immune responses upon re-stimulation of leukocytes in vitro, and sensitivity to aerosol challenge. Despite some detectable differences, the results highlight the similarity of immune responses to tularemia vaccines and challenge outcomes between the three substrains, indicating that all offer acceptable and comparable approaches as animal models to study Francisella infection and immunity.
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Affiliation(s)
- Roberto De Pascalis
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, United States
| | - Varunika Bhargava
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, United States
| | - Scott Espich
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, United States
| | - Terry H. Wu
- Center for Infectious Disease and Immunity and Department of Internal Medicine, University of New Mexico, Albuquerque, NM, United States
| | | | - Karen L. Elkins
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, United States
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Working correlates of protection predict SchuS4-derived-vaccine candidates with improved efficacy against an intracellular bacterium, Francisella tularensis. NPJ Vaccines 2022; 7:95. [PMID: 35977964 PMCID: PMC9385090 DOI: 10.1038/s41541-022-00506-9] [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: 07/27/2021] [Accepted: 07/01/2022] [Indexed: 11/09/2022] Open
Abstract
Francisella tularensis, the causative agent of tularemia, is classified as Tier 1 Select Agent with bioterrorism potential. The efficacy of the only available vaccine, LVS, is uncertain and it is not licensed in the U.S. Previously, by using an approach generally applicable to intracellular pathogens, we identified working correlates that predict successful vaccination in rodents. Here, we applied these correlates to evaluate a panel of SchuS4-derived live attenuated vaccines, namely SchuS4-ΔclpB, ΔclpB-ΔfupA, ΔclpB-ΔcapB, and ΔclpB-ΔwbtC. We combined in vitro co-cultures to quantify rodent T-cell functions and multivariate regression analyses to predict relative vaccine strength. The predictions were tested by rat vaccination and challenge studies, which demonstrated a clear relationship between the hierarchy of in vitro measurements and in vivo vaccine protection. Thus, these studies demonstrated the potential power a panel of correlates to screen and predict the efficacy of Francisella vaccine candidates, and in vivo studies in Fischer 344 rats confirmed that SchuS4-ΔclpB and ΔclpB-ΔcapB may be better vaccine candidates than LVS.
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Shoudy LE, Namjoshi P, Giordano G, Kumar S, Bowling JD, Gelhaus C, Barry EM, Hazlett AJ, Hazlett BA, Cooper KL, Pittman PR, Reed DS, Hazlett KRO. The O-Ag Antibody Response to Francisella Is Distinct in Rodents and Higher Animals and Can Serve as a Correlate of Protection. Pathogens 2021; 10:pathogens10121646. [PMID: 34959601 PMCID: PMC8704338 DOI: 10.3390/pathogens10121646] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 12/13/2021] [Accepted: 12/17/2021] [Indexed: 11/16/2022] Open
Abstract
Identifying correlates of protection (COPs) for vaccines against lethal human (Hu) pathogens, such as Francisella tularensis (Ft), is problematic, as clinical trials are currently untenable and the relevance of various animal models can be controversial. Previously, Hu trials with the live vaccine strain (LVS) demonstrated ~80% vaccine efficacy against low dose (~50 CFU) challenge; however, protection deteriorated with higher challenge doses (~2000 CFU of SchuS4) and no COPs were established. Here, we describe our efforts to develop clinically relevant, humoral COPs applicable to high-dose, aerosol challenge with S4. First, our serosurvey of LVS-vaccinated Hu and animals revealed that rabbits (Rbs), but not rodents, recapitulate the Hu O-Ag dependent Ab response to Ft. Next, we assayed Rbs immunized with distinct S4-based vaccine candidates (S4ΔclpB, S4ΔguaBA, and S4ΔaroD) and found that, across multiple vaccines, the %O-Ag dep Ab trended with vaccine efficacy. Among S4ΔguaBA-vaccinated Rbs, the %O-Ag dep Ab in pre-challenge plasma was significantly higher in survivors than in non-survivors; a cut-off of >70% O-Ag dep Ab predicted survival with high sensitivity and specificity. Finally, we found this COP in 80% of LVS-vaccinated Hu plasma samples as expected for a vaccine with 80% Hu efficacy. Collectively, the %O-Ag dep Ab response is a bona fide COP for S4ΔguaBA-vaccinated Rb and holds significant promise for guiding vaccine trials with higher animals.
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Affiliation(s)
- Lauren E. Shoudy
- Department of Regenerative and Cancer Cell Biology, Albany Medical College, Albany, NY 12208, USA; (L.E.S.); (G.G.)
| | - Prachi Namjoshi
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, NY 12208, USA; (P.N.); (S.K.)
| | - Gabriela Giordano
- Department of Regenerative and Cancer Cell Biology, Albany Medical College, Albany, NY 12208, USA; (L.E.S.); (G.G.)
| | - Sudeep Kumar
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, NY 12208, USA; (P.N.); (S.K.)
| | - Jennifer D. Bowling
- Center for Vaccine Research, University of Pittsburgh, Pittsburgh, PA 15261, USA; (J.D.B.); (D.S.R.)
| | | | - Eileen M. Barry
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD 21201, USA;
| | - Allan J. Hazlett
- Department of Philosophy, Washington University, St Louis, MO 63130, USA;
| | - Brian A. Hazlett
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA;
| | - Kristine L. Cooper
- Hillman Cancer Center, Biostatistics Facility, University of Pittsburgh, Pittsburgh, PA 15261, USA;
| | - Phillip R. Pittman
- U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Fredrick, MD 21702, USA;
| | - Douglas S. Reed
- Center for Vaccine Research, University of Pittsburgh, Pittsburgh, PA 15261, USA; (J.D.B.); (D.S.R.)
| | - Karsten R. O. Hazlett
- Department of Regenerative and Cancer Cell Biology, Albany Medical College, Albany, NY 12208, USA; (L.E.S.); (G.G.)
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, NY 12208, USA; (P.N.); (S.K.)
- Correspondence: ; Tel.: +1-518-262-2338
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Differential Immune Response Following Intranasal and Intradermal Infection with Francisella tularensis: Implications for Vaccine Development. Microorganisms 2021; 9:microorganisms9050973. [PMID: 33946283 PMCID: PMC8145380 DOI: 10.3390/microorganisms9050973] [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: 03/25/2021] [Revised: 04/19/2021] [Accepted: 04/21/2021] [Indexed: 11/17/2022] Open
Abstract
Francisella tularensis (Ft) is a Gram-negative, facultative intracellular coccobacillus that is the etiological agent of tularemia. Interestingly, the disease tularemia has variable clinical presentations that are dependent upon the route of infection with Ft. Two of the most likely routes of Ft infection include intranasal and intradermal, which result in pneumonic and ulceroglandular tularemia, respectively. While there are several differences between these two forms of tularemia, the most notable disparity is between mortality rates: the mortality rate following pneumonic tularemia is over ten times that of the ulceroglandular disease. Understanding the differences between intradermal and intranasal Ft infections is important not only for clinical diagnoses and treatment but also for the development of a safe and effective vaccine. However, the immune correlates of protection against Ft, especially within the context of infection by disparate routes, are not yet fully understood. Recent advances in different animal models have revealed new insights in the complex interplay of innate and adaptive immune responses, indicating dissimilar patterns in both responses following infection with Ft via different routes. Further investigation of these differences will be crucial to predicting disease outcomes and inducing protective immunity via vaccination or natural infection.
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Systems Vaccinology for a Live Attenuated Tularemia Vaccine Reveals Unique Transcriptional Signatures That Predict Humoral and Cellular Immune Responses. Vaccines (Basel) 2019; 8:vaccines8010004. [PMID: 31878161 PMCID: PMC7158697 DOI: 10.3390/vaccines8010004] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 12/19/2019] [Accepted: 12/20/2019] [Indexed: 12/16/2022] Open
Abstract
Background: Tularemia is a potential biological weapon due to its high infectivity and ease of dissemination. This study aimed to characterize the innate and adaptive responses induced by two different lots of a live attenuated tularemia vaccine and compare them to other well-characterized viral vaccine immune responses. Methods: Microarray analyses were performed on human peripheral blood mononuclear cells (PBMCs) to determine changes in transcriptional activity that correlated with changes detected by cellular phenotyping, cytokine signaling, and serological assays. Transcriptional profiles after tularemia vaccination were compared with yellow fever [YF-17D], inactivated [TIV], and live attenuated [LAIV] influenza. Results: Tularemia vaccine lots produced strong innate immune responses by Day 2 after vaccination, with an increase in monocytes, NK cells, and cytokine signaling. T cell responses peaked at Day 14. Changes in gene expression, including upregulation of STAT1, GBP1, and IFIT2, predicted tularemia-specific antibody responses. Changes in CCL20 expression positively correlated with peak CD8+ T cell responses, but negatively correlated with peak CD4+ T cell activation. Tularemia vaccines elicited gene expression signatures similar to other replicating vaccines, inducing early upregulation of interferon-inducible genes. Conclusions: A systems vaccinology approach identified that tularemia vaccines induce a strong innate immune response early after vaccination, similar to the response seen after well-studied viral vaccines, and produce unique transcriptional signatures that are strongly correlated to the induction of T cell and antibody responses.
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De Pascalis R, Hahn A, Brook HM, Ryden P, Donart N, Mittereder L, Frey B, Wu TH, Elkins KL. A panel of correlates predicts vaccine-induced protection of rats against respiratory challenge with virulent Francisella tularensis. PLoS One 2018; 13:e0198140. [PMID: 29799870 PMCID: PMC5969757 DOI: 10.1371/journal.pone.0198140] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 05/14/2018] [Indexed: 12/17/2022] Open
Abstract
There are no defined correlates of protection for any intracellular pathogen, including the bacterium Francisella tularensis, which causes tularemia. Evaluating vaccine efficacy against sporadic diseases like tularemia using field trials is problematic, and therefore alternative strategies to test vaccine candidates like the Francisella Live Vaccine Strain (LVS), such as testing in animals and applying correlate measurements, are needed. Recently, we described a promising correlate strategy that predicted the degree of vaccine-induced protection in mice given parenteral challenges, primarily when using an attenuated Francisella strain. Here, we demonstrate that using peripheral blood lymphocytes (PBLs) in this approach predicts LVS-mediated protection against respiratory challenge of Fischer 344 rats with fully virulent F. tularensis, with exceptional sensitivity and specificity. Rats were vaccinated with a panel of LVS-derived vaccines and subsequently given lethal respiratory challenges with Type A F. tularensis. In parallel, PBLs from vaccinated rats were evaluated for their functional ability to control intramacrophage Francisella growth in in vitro co-culture assays. PBLs recovered from co-cultures were also evaluated for relative gene expression using a large panel of genes identified in murine studies. In vitro control of LVS intramacrophage replication reflected the hierarchy of protection. Further, despite variability between individuals, 22 genes were significantly more up-regulated in PBLs from rats vaccinated with LVS compared to those from rats vaccinated with the variant LVS-R or heat-killed LVS, which were poorly protective. These genes included IFN-γ, IL-21, NOS2, LTA, T-bet, IL-12rβ2, and CCL5. Most importantly, combining quantifications of intramacrophage growth control with 5-7 gene expression levels using multivariate analyses discriminated protected from non-protected individuals with greater than 95% sensitivity and specificity. The results therefore support translation of this approach to non-human primates and people to evaluate new vaccines against Francisella and other intracellular pathogens.
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Affiliation(s)
- Roberto De Pascalis
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, Maryland, United States of America
| | - Andrew Hahn
- Center for Infectious Disease and Immunity, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Helen M. Brook
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, Maryland, United States of America
| | - Patrik Ryden
- Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden
| | - Nathaniel Donart
- Center for Infectious Disease and Immunity, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Lara Mittereder
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, Maryland, United States of America
| | - Blake Frey
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, Maryland, United States of America
| | - Terry H. Wu
- Center for Infectious Disease and Immunity, University of New Mexico, Albuquerque, New Mexico, United States of America
- Department of Internal Medicine, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Karen L. Elkins
- Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, Maryland, United States of America
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Bar-On L, Cohen H, Elia U, Rotem S, Bercovich-Kinori A, Bar-Haim E, Chitlaru T, Cohen O. Protection of vaccinated mice against pneumonic tularemia is associated with an early memory sentinel-response in the lung. Vaccine 2017; 35:7001-7009. [PMID: 29102170 DOI: 10.1016/j.vaccine.2017.10.053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Revised: 10/03/2017] [Accepted: 10/18/2017] [Indexed: 01/06/2023]
Abstract
Francisella tularensis is the intracellular bacterial pathogen causing the respiratory life-threatening disease tularemia. Development of tularemia vaccines has been hampered by an incomplete understanding of the correlates of immunity. Moreover, the importance of lung cellular immunity in vaccine-mediated protection against tularemia is a controversial matter. Live attenuated vaccine strains of F. tularensis such as LVS (Live Vaccine Strain), elicit an immune response protecting mice against subsequent challenge with the virulent SchuS4 strain, yet the protective immunity against pulmonary challenge is limited in its efficacy and longevity. We established a murine intra-nasal immunization model which distinguishes between animals fully protected, challenged at 4 weeks post double-vaccination (200 inhalation Lethal Dose 50%, LD50, of SchuS4), and those which do not survive the lethal SchuS4 infection, challenged at 8 weeks post double vaccination. Early in the recall immune response in the lung (before day 3), disease progression and bacterial dissemination differed considerably between protected and non-protected immunized mice. Pre-challenge analysis, revealed that protected mice, exhibited significantly higher numbers of lung Ft-specific memory T cells compared to non-protected mice. Quantitative PCR analysis established that a higher magnitude, lung T cells response was activated in the lungs of the protected mice already at 24 h post-challenge. The data imply that an early memory response within the lung is strongly associated with protection against the lethal SchuS4 bacteria presumably by restricting the dissemination of the bacteria to internal organs. Thus, future prophylactic strategies to countermeasure F. tularensis infection may require modulation of the immune response within the lung.
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Affiliation(s)
- Liat Bar-On
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel.
| | - Hila Cohen
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel
| | - Uri Elia
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel
| | - Shahar Rotem
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel
| | - Adi Bercovich-Kinori
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel
| | - Erez Bar-Haim
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel
| | - Theodor Chitlaru
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel
| | - Ofer Cohen
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel.
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Gaur R, Alam SI, Kamboj DV. Immunoproteomic Analysis of Antibody Response of Rabbit Host Against Heat-Killed Francisella tularensis Live Vaccine Strain. Curr Microbiol 2017; 74:499-507. [PMID: 28233060 DOI: 10.1007/s00284-017-1217-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 02/10/2017] [Indexed: 11/24/2022]
Abstract
Francisella tularensis, the causative agent of tularemia, has attained the status of one of the high priority agents that could be used in the act of bioterrorism. Currently, there is no licensed vaccine for this highly infectious intracellular pathogen. Being a listed 'Category A' agent of the U.S. Center for Disease Control and Prevention (CDC), vaccines and therapeutics are immediately required against this pathogen. In this study, an immunoproteomic approach based on the techniques of 2-dimensional gel electrophoresis (2DE) and immunoblotting combined with mass spectrometry (MS) was used for elucidation of immunogenic components and putative vaccine candidates. Whole-cell soluble protein extract of F. tularensis LVS (Ft LVS) was separated by 2DE, and immunoblots were developed with sera raised in rabbit after immunization with heat-killed Ft LVS. A total of 28 immunoreactive proteins were identified by tandem mass spectrometry. Rabbit immunoproteome of F. tularensis was compared with those previously reported using sera from human patients and in murine model. Out of 28 immunoreactive proteins identified in this study, 12 and 17 overlapping proteins were recognized by human and murine sera, respectively. Nine proteins were found immunogenic in all the three hosts, while eight new immunogenic proteins were found in this study. Identified immunoreactive proteins may find application in design and development of protein subunit vaccine for tularemia.
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Affiliation(s)
- Ritu Gaur
- Biotechnology Division, Defence Research and Development Establishment, Gwalior, 474002, India
| | - Syed Imteyaz Alam
- Biotechnology Division, Defence Research and Development Establishment, Gwalior, 474002, India
| | - Dev Vrat Kamboj
- Biotechnology Division, Defence Research and Development Establishment, Gwalior, 474002, India.
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Abstract
Francisella tularensis (Ft) is a gram-negative intercellular pathogen and category A biothreat agent. However, despite 15 years of strong government investment and intense research focused on the development of a US Food and Drug Administration-approved vaccine against Ft, the primary goal remains elusive. This article reviews research efforts focused on developing an Ft vaccine, as well as a number of important factors, some only recently recognized as such, which can significantly impact the development and evaluation of Ft vaccine efficacy. Finally, an assessment is provided as to whether a US Food and Drug Administration-approved Ft vaccine is likely to be forthcoming and the potential means by which this might be achieved.
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Affiliation(s)
- Raju Sunagar
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, NY, USA
| | - Sudeep Kumar
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, NY, USA
| | - Brian J Franz
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, NY, USA
| | - Edmund J Gosselin
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, NY, USA
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Elkins KL, Kurtz SL, De Pascalis R. Progress, challenges, and opportunities in Francisella vaccine development. Expert Rev Vaccines 2016; 15:1183-96. [PMID: 27010448 DOI: 10.1586/14760584.2016.1170601] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Renewed interest in Francisella tularensis has resulted in substantial new information about its pathogenesis and immunology, along with development of useful animal models. While understanding of protective immunity against Francisella remains incomplete, data in both animals and humans suggest that inducing T cell-mediated immunity is crucial for successful vaccination with current candidates such as the Live Vaccine Strain (LVS), with specific antibodies and immune B cells playing supporting roles. Consistent with this idea, recent results indicate that measurements of T cell functions and relative gene expression by immune T cells predict vaccine-induced protection in animal models. Because field trials of new vaccines will be difficult to design, using such measurements to derive potential correlates of protection may be important to bridge between animal efficacy studies and people.
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Affiliation(s)
- Karen L Elkins
- a Division of Bacterial, Parasitic, and Allergenic Products, CBER/FDA , Silver Spring , MD , USA
| | - Sherry L Kurtz
- a Division of Bacterial, Parasitic, and Allergenic Products, CBER/FDA , Silver Spring , MD , USA
| | - Roberto De Pascalis
- a Division of Bacterial, Parasitic, and Allergenic Products, CBER/FDA , Silver Spring , MD , USA
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Activities of Murine Peripheral Blood Lymphocytes Provide Immune Correlates That Predict Francisella tularensis Vaccine Efficacy. Infect Immun 2016; 84:1054-1061. [PMID: 26810039 DOI: 10.1128/iai.01348-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 01/15/2016] [Indexed: 12/16/2022] Open
Abstract
We previously identified potential correlates of vaccine-induced protection against Francisella tularensis using murine splenocytes and further demonstrated that the relative levels of gene expression varied significantly between tissues. In contrast to splenocytes, peripheral blood leukocytes (PBLs) represent a means to bridge vaccine efficacy in animal models to that in humans. Here we take advantage of this easily accessible source of immune cells to investigate cell-mediated immune responses against tularemia, whose sporadic incidence makes clinical trials of vaccines difficult. Using PBLs from mice vaccinated with F. tularensis Live Vaccine Strain (LVS) and related attenuated strains, we combined the control of in vitro Francisella replication within macrophages with gene expression analyses. The in vitro functions of PBLs, particularly the control of intramacrophage LVS replication, reflected the hierarchy of in vivo protection conferred by LVS-derived vaccines. Moreover, several genes previously identified by the evaluation of splenocytes were also found to be differentially expressed in immune PBLs. In addition, more extensive screening identified additional potential correlates of protection. Finally, expression of selected genes in mouse PBLs obtained shortly after vaccination, without ex vivo restimulation, was different among vaccine groups, suggesting a potential tool to monitor efficacious vaccine-induced immune responses against F. tularensis. Our studies demonstrate that murine PBLs can be used productively to identify potential correlates of protection against F. tularensis and to expand and refine a comprehensive set of protective correlates.
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