Recombinant vaccinia viruses used as experimental leishmaniases vaccines within the last 10 years.
Abstract
Due to an increase in the incidence of leishmaniases worldwide, the development of new strategies such as prophylactic vaccines to prevent infection and decrease the diseases has become a high priority. The development of vaccines against the various species of pathogenic Leishmania to humans has been hampered, in part, by the inefficient stimulation of the protective cellular immunity promoted by the administration of purified or recombinant antigens, indicating the need for new approaches. Viral vectors represent an attractive way to deliver and present vaccine antigens that may offer advantages over traditional platforms. Among the most attractive and efficient viral vectors in inducing a cellular immune response, vaccinia virus has been the most used in leishmaniases vaccine trials. The first report of the use of recombinant vaccinia virus (VACV) in the induction of protection against Leishmania infection was made in 1993. Since then, several Leishmania spp. antigenic subunits were cloned into recombinant VACV. Although highly attenuated poxviral vectors are capable of inducing protective immunity against Leishmania spp., their limitation in replicative capacity reduces their potential as compared to replicative vectors. In order to achieve a balance between safety and replication, several VACV strains with intermediate phenotype have been developed.
Keywords
- leishmaniases
- vaccines
- viral vectors
- recombinant vaccinia virus
- VACV
1. Introduction
Leishmaniases are important neglected tropical diseases (NTD) caused by protozoan parasites from the genus
It is estimated that 14 million people are infected worldwide, and 350 million are at risk of infection. Approximately 1.3 million new cases are registered annually [3]. According to the Global Burden of Disease Study (GDB) 2010, about 50,000 people die each year from the diseases, resulting in 3.3 million disability-adjusted life years (DALY) lost [6]. In recent decades, several
According to the World Health Organization (WHO), leishmaniases are among the emerging and uncontrolled category 1 diseases, and their prevention is based primarily on three parameters: (I) vector control, (II) control of parasitic reservoir animals, and (III) research and development of new vaccine candidates [8]. Spraying of intra- and peri-domiciliary residual insecticides has been crucial in the control of sandflies. However, there is concern about the emergence of vector resistance to dichlorodiphenyltrichloroethane (DDT), especially in highly endemic areas [9]. The chemotherapeutic treatment of infected dogs, the main reservoirs of the parasite in VL, reduces or eliminates symptoms. Yet, many animals are still able to transmit the parasite, remaining the epidemiological risk. Other measures, such as topical insecticides and impregnated collars, are expensive and difficult to implement in national control programs [10]. In the absence of effective strategies, vaccine development is cost-effective in controlling leishmaniases. It is estimated that a vaccine with a 70% efficacy providing protection for 10 years is able to prevent 41–144 thousand CL cases in seven Latin American countries (Bolivia, Brazil, Colombia, Ecuador, Mexico, Peru, and Venezuela) with an inferior cost than the currently recommended treatments. As for VL, even a vaccine that provides protection for only 5 years with a 50% efficacy would still be more economically feasible compared to current treatments [9].
The first leishmaniases vaccination attempts, named leishmanization, were based on the observation that an individual cured of a cutaneous lesion became refractory to reinfection [7, 8]. In leishmanization, the infectious lesion material, later replaced by the cultured parasites, was used in the inoculation of uninfected individuals. This method was interrupted due to a number of factors, including quality control, persistence of the parasite in the body, the emergence of the HIV virus in the 1980s, and ethical reasons [11].
The first generation of vaccines emerged from leishmanization and comprises heat or phenol-killed promastigote forms associated with different adjuvants, including BCG (
The second generation of vaccines includes purified or recombinant
Likewise A2, FML, LiESP, and Protein Q , several other
Among the possible vaccine vectors, the most promising are those based on recombinant viruses, capable of expressing heterologous proteins directly within the cells of the host organism, likewise in natural infection. Vaccines based on viral vectors represent a highly versatile platform for the development of vaccines. Viral genomes can be manipulated to express any target antigen and consistently carry relatively large transgene insertions [23]. Moreover, among the advantages of using recombinant viruses as vaccine vectors is the fact that viruses have evolved as the most efficient organisms in infecting cells. After 10 minutes of infection, more than 95% of certain viruses can be found inside host cells. Another advantage is that viral proteins can play as powerful adjuvants. Besides, viruses can infect antigen-presenting cells (APC), avoiding cross-presentation. Lastly, some recombinant viruses can be lyophilized and stored without the need for special refrigeration equipment [22]. Considering the recombinant viruses most commonly used as vaccine vectors, there are already established high-throughput and large-scale production processes, aiming to use this technology in the context of pandemics [23]. Vaccinia virus is one of the most attractive and efficient vectors [22] and widely used in leishmaniases vaccine trials, which is the focus of the present study.
2. Immunology of leishmaniases
Resistance to infection by
Reactive oxygen, nitrogen, and nitric oxide (NO) species, induced by IL-12, are the main responsible for the macrophages leishmanicidal activity. NO is produced from the metabolism of L-arginine, in a reaction catalyzed by the inducible nitric oxide synthase (iNOS). Cytokines such as interferon gamma (IFN-γ) and TNF-α stimulate iNOS expression, while IL-4 and IL-10 inhibit its expression, turning macrophages refractory to leishmanicidal activity [23, 24].
Dendritic cells (DC) also belong to the mononuclear phagocytic system and play as a link between innate and adaptive immune responses. DC are recruited to the site of infection by cytokine/chemokine released by infected macrophages and neutrophils. The ability of DC to present antigens through MHC (major histocompatibility complex) classes I and II induces the stimulation of
CD4+ T cells play a crucial role in the protective immunity against
Although
The wide variety of cytokines and effector mechanisms involved in the immune responses induced by various species of
3. Activation mechanisms of the immune response by recombinant viruses
The mammalian immune system has evolved to the efficient recognition of intruder viruses, being able to activate potent innate and adaptive immune responses (see Figure 1). Depending on the nature and replication strategy of the viral genome, several PRR are involved in the innate immune response to the recombinant virus (see Figure 1). Receptors for nucleic acids include TLR3, TLR7, TLR8, and TLR9 in the endosome, as well as cytosolic RNA/DNA sensors such as RIG-I (retinoic acid inducible gene I), MDA5 (melanoma differentiation-associated gene 5), and cGAS (cyclic GMP-AMP synthase). After binding to the viral genome, these receptors signal via the NFκB and MAPK (mitogen-activated protein kinase) pathways, resulting in the induction of pro-inflammatory cytokines and chemokines. Viral vectors that induce inflammation generally play as “self-adjuvanted.” A second effect of endosomal TLR signaling is the activation of interferon regulatory factor (IRF) 3 and IRF7, transcription factors necessary for the expression of the type I interferon (IFN-I) genes: IFN-α and IFN-β [34]. IFN-I induces the maturation of APC (see Figure 2), especially DC, by stimulating the expression of co-stimulatory molecules such as CD80, CD86, and CD40, which in turn, lead to an efficient DC homing to secondary lymphoid organs and the antigens presentation to CD4+ and CD8+ T cells. IFN-I also promotes the cross-presentation of viral antigens processed on the DC endosomes to CD8+ T cells [35].
While first-generation (killed or attenuated parasites) or second-generation (purified or recombinant proteins) vaccines are capable of inducing an intense humoral immune response, they are inefficient in activating cellular immune response based on cytotoxic CD8+ T cells (CTL). Recombinant viral vectors, however, have the specificity of inducing an intense expression of heterologous proteins, encoded in the transgene, inside infected cells [22]. Activation of CTL requires the expression of the pathogen proteins in the cytosol APC, as well as the binding of the antigen to the MHC class I molecules [36]. The immune response based on CD8+ T cells is initiated by the generation of peptides from their protein precursors cleaved in the cellular proteasome. After cleavage, the resulting peptides are complexed to TAP (transporter associated with antigen processing) and transported from the cytosol into the endoplasmic reticulum (ER), where the interaction between the peptide and the MHC class I molecule occurs (see Figure 1). Subsequently, the peptide/MHC I complex is transported to the cell surface, and the epitope can be presented and recognized by CD8+ T cells [34]. CD8+ T cells recognize the antigenic peptides of endocytosed microorganisms, producing cytokines such as IFN-γ, which activate infected phagocytes to extinguish microorganisms (cytotoxic mechanism) and stimulate inflammation (see Figure 2).
In addition to the CD8+ T cell epitopes, other important epitopes are those responsible for the induction of immune response by CD4+ T cells. Viral proteins (“self-adjuvanted”) or heterologous antigens fused to the viral capsid structural proteins may activate immune responses based on CD4+ T cells. Viral protein or heterologous proteins fused to the virus are processed inside endosomal/lysosomal vesicles, and the resulting peptides bind to MHC class II molecules (see Figure 1). The peptide/MHC II complex is presented on the surface of APC to CD4+ T cells. Vaccine viral vectors composed of these epitopes may induce memory CD4+ T cells potentially capable of being activated by the body’s natural exposure to the pathogen [22]. The differentiation of CD4+ T cells in the Th1 subtype occurs in response to microorganisms, including viruses, which infect or activate APC. Activated Th1 cells secrete IFN-γ, among other cytokines. IFN-γ acts in the APC to stimulate the destruction of microorganisms (see Figure 2). If the heterologous proteins expressed by the recombinant viral vectors present associated signal-peptide (SP), they have the potential capacity to be surface and/or secreted proteins. When the destination of these proteins is the mitochondria or the secretory pathway, their displacement usually requires the presence of N-terminal sequences capable of being recognized by the cellular transport machinery. SP are responsible for targeting the proteins to the ER and, later, to the cell secretory pathway. Thus, these proteins may be anchored to the cytoplasmic membrane or secreted [37] and recognized by B cells, activating the production of specific antibodies (see Figure 2).
4. Leishmaniases experimental vaccines based on vaccinia virus-derived vectors
Although almost every viral genome can be manipulated in order to acquire heterologous protein expression capacity in host cells, not all viruses are as effective in doing so. Some types have been shown to be more efficient than others in the induction of cellular immune response, with vaccinia virus being one of the most attractive and efficient vector [22] and widely used in leishmaniases vaccine trials.
The vaccine virus (VACV or VV) is a member of the family
4.1 Construction of a recombinant vaccinia virus by homologous recombination
The construction of recombinant viral vectors requires adaptation of the gene of interest for expression in host cells. In many cases, this requires intracellular recombination steps for the incorporation of the gene of interest into the viral genome. The construction of a recombinant vaccinia virus is based on a helper virus-dependent system [22]. Expression of the gene of interest may occur if the gene, under the control of a vaccinia virus promoter, is cloned into a plasmid (shuttle vector). The plasmid is transfected into a permissive cell highly infected with wild-type vaccinia virus. The gene of interest is incorporated into the wild-type vaccinia virus through homologous recombination between the viral genome and the shuttle vector (see Figure 3) [39].
4.2 Vaccinia virus in leishmaniases vaccines development
The development of vaccines against smallpox, which culminated in its eradication in the 1970s, resulted in a number of strains of vaccinia virus [40]. The first generation of vaccines against cancer, HIV/AIDS, and other infectious diseases was based on replication-competent strains of VACV, such as WR (Western Reserve strain), Wyeth, and Copenhagen. However, for safety reasons, most of the vectors currently used in vaccine trials are VACV non-replicative strains, such as MVA and NYVAC. Although highly attenuated vectors are capable of inducing protective immunity against various pathogens, their limitation in replicative capacity reduces their potential as compared to replicative vectors. In order to achieve a balance between safety and replication, several VACV strains with intermediate phenotype have been developed [41].
The first report of the use of recombinant vaccinia virus in the induction of protection against
Since then, several
The recombinant MVA vaccine vector expressing TRYP was used in a phase I clinical trial in dogs, the main VL domestic reservoirs caused by
Ramos
In 2013, Sánchez-Sampedro
In addition to MVA, NYVAC is one of the most studied attenuated strains of vaccinia virus. NYVAC was derived from a plaque-cloned isolate of Copenhagen smallpox vaccine strain by selective deletion of 18 open reading frames (ORF) involved in virulence, pathogenicity, and host range regulation. Sánchez-Sampedro
Finally, a heterologous prime-boost immunization strategy using KMP-11-DNA priming followed by boosting recombinant vaccinia virus (rVV) expressing the same antigen was able to induce protective immunity in both hamsters and in mice against VL caused by both antimony resistant (Sb-R) and sensitive (Sb-S)
5. Conclusion
The declaration of smallpox eradication by the World Health Organization, in 1980, and the discovery that genes encoding heterologous antigens could be inserted into the genome of attenuated vaccinia virus, in 1982, resulted in a burst of scientific publications highlighting the potential clinical benefits of the recombinant poxvirus vectors as vaccines against various pathogens. Among the most attractive and efficient viral vectors in inducing a cellular immune response, vaccinia virus has been the most used in leishmaniases vaccine trials, especially in combination with DNA vaccines (heterologous prime/boost protocols). However, studies showed that greatly enhanced immune responses could be obtained when two different viral vectors expressing the common antigen were used following the prime-boost immunization protocol, which may be experienced in future leishmaniases vaccine efficacy studies. Although highly attenuated vectors, especially MVA and NYVAC, are safe and capable of inducing protective immunity against infection by several
Conflicts of interest
The authors declare that there are no conflict of interests regarding the publication of this paper.
Funding
This work was partly supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq no. 306952/2017-3), Brazil.
References
- 1.
Desjeux P et al. Leishmaniasis. Nature Reviews Microbiology. 2004; 2 :692-693 - 2.
Ready PD. Biology of phlebotomine sand flies as vectors of disease agents. Annual Review of Entomology. 2013; 58 (1):227-250 - 3.
World Health Organization. OMS, Leishmaniasis. WHO. 2015 - 4.
Lainson R, Ready PD, Shaw JJ. Leishmania in phlebotomid sandflies. VII. On the taxonomic status of Leishmania peruviana, causative agent of Peruvian ‘uta’, as indicated by its development in the sandfly, Lutzomyia longipalpis. Proceedings of the Royal Society B: Biological Sciences. 1979; 206 :307-318 - 5.
Lainson R, Shaw JJ, Silveira FT. Dermal and visceral leishmaniasis and their causative agents. Transactions of the Royal Society of Tropical Medicine and Hygiene. 1987; 81 :702-703 - 6.
Hotez PJ et al. The global burden of disease study 2010: Interpretation and implications for the neglected tropical diseases. PLoS Neglected Tropical Diseases. 2014; 8 :e2865 - 7.
Vos T et al. Global, regional, and national incidence, prevalence, and years lived with disability for 301 acute and chronic diseases and injuries in 188 countries, 1990-2013: A systematic analysis for the global burden of disease study 2013. Lancet. 2015; 386 :743-800 - 8.
Jain K, Jain NK. Vaccines for visceral leishmaniasis: A review. Journal of Immunological Methods. 2015; 422 :1-12 - 9.
Gillespie PM, Beaumier CM, Strych U, Hayward T, Hotez PJ, Bottazzi ME. Status of vaccine research and development of vaccines for leishmaniasis. Vaccine. 2016; 34 :2992-2995 - 10.
Reis AB, Giunchetti RC, Carrillo E, Martins-Filho OA, Moreno J. Immunity to Leishmania and the rational search for vaccines against canine leishmaniasis. Trends in Parasitology. 2010; 26 :341-349 - 11.
Kedzierski L. Leishmaniasis vaccine: Where are we today? Journal of Global Infectious Diseases. 2010; 2 :177-185 - 12.
Ghorbani M, Farhoudi R. Leishmaniasis in humans: Drug or vaccine therapy? Drug Design Development and Therapy. 2018; 12 :25-40 - 13.
Dantas-Torres F. Leishmune® vaccine: The newest tool for prevention and control of canine visceral leishmaniosis and its potential as a transmission-blocking vaccine. Veterinary Parasitology. 2006; 141 :1-8 - 14.
Zhang WW, Matlashewski G. Characterization of the A2-A2rel gene cluster in Leishmania donovani: Involvement of A2 in visceralization during infection. Molecular Microbiology. 2001; 39 :935-948 - 15.
Fernandes AP et al. Protective immunity against challenge with Leishmania (Leishmania) chagasi in beagle dogs vaccinated with recombinant A2 protein. Vaccine. 2008; 26 :5888-5895 - 16.
Moreno J, Vouldoukis I, Martin V, McGahie D, Cuisinier AM, Gueguen S. Use of a liesp/qa-21 vaccine (canileish) stimulates an appropriate th1-dominated cell-mediated immune response in dogs. PLoS Neglected Tropical Diseases. 2012; 6 :e1683 - 17.
Martin V, Vouldoukis I, Moreno J, McGahie D, Gueguen S, Cuisinier AM. The protective immune response produced in dogs after primary vaccination with the LiESP/QA-21 vaccine (CaniLeish®) remains effective against an experimental challenge one year later. Veterinary Research. 2014; 45 :69 - 18.
Fernández Cotrina J et al. A large-scale field randomized trial demonstrates safety and efficacy of the vaccine LetiFend® against canine leishmaniosis. Vaccine. 2018; 36 :1972-1982 - 19.
Kedzierski L, Zhu Y, Handman E. Leishmania vaccines: Progress and problems. Parasitology. 2006; 133 (Suppl):S87-S112 - 20.
Dikhit MR et al. The potential HLA class I-restricted epitopes derived from LeIF and TSA of Leishmania donovani evoke anti-leishmania CD8+ T lymphocyte response. Scientific Reports. 2018; 8 :14175 - 21.
Kashyap M, Jaiswal V, Farooq U. Prediction and analysis of promiscuous T cell-epitopes derived from the vaccine candidate antigens of Leishmania donovani binding to MHC class-II alleles using in silico approach. Infection, Genetics and Evolution. 2017; 53 :107-115 - 22.
Rocha CD, Caetano BC, Machado AV, Bruña-Romero O. Recombinant viruses as tools to induce protective cellular immunity against infectious diseases. International Microbiology. 2004; 7 :83-94 - 23.
Rauch S, Jasny E, Schmidt KE, Petsch B. New vaccine technologies to combat outbreak situations. Frontiers in Immunology. 2018; 9 :1963 - 24.
Srivastava S, Shankar P, Mishra J, Singh S. Possibilities and challenges for developing a successful vaccine for leishmaniasis. Parasites & Vectors. 2016; 9 :277 - 25.
Alexander J, Bryson K. T helper (h)1/Th2 and Leishmania: Paradox rather than paradigm. Immunology Letters. 2005; 99 :17-23 - 26.
Sacks DL, Noben-Trauth N. The immunology of susceptibility and resistance to Leishmania major in mice. Nature Reviews. Immunology. 2002; 2 :845-858 - 27.
Wilson ME, Jeronimo SMB, Pearson RD. Immunopathogenesis of infection with the visceralizing Leishmania species. Microbial Pathogenesis. 2005; 38 :147-160 - 28.
Murray HW et al. Interleukin-10 (IL-10) in experimental visceral leishmaniasis and IL-10 receptor blockade as immunotherapy. Infection and Immunity. 2002; 70 :6284-6293 - 29.
Ahmed S et al. Intradermal infection model for pathogenesis and vaccine studies of murine visceral leishmaniasis. Infection and Immunity. 2003; 71 :401-410 - 30.
Miralles GD, Stoeckle MY, McDermott DF, Finkelman FD, Murray HW. Th1 and Th2 cell-associated cytokines in experimental visceral Leishmaniasis. Infection and Immunity. 1994; 62 :1058-1063 - 31.
De Brito RCF et al. Peptide vaccines for leishmaniasis. Frontiers in Immunology. 2018; 9 :1043 - 32.
Jordan KA, Hunter CA. Regulation of CD8+T cell responses to infection with parasitic protozoa. Experimental Parasitology. 2010; 126 :318-325 - 33.
Brunet LR. Nitric oxide in parasitic infections. International Immunopharmacology. 2001; 1 :1457-1467 - 34.
Pinschewer DD. Virally vectored vaccine delivery: Medical needs, mechanisms, advantages and challenges. Swiss Medical Weekly. 2017; 147 :w14465 - 35.
Huang X, Yang Y. Innate immune recognition of viruses and viral vectors. Human Gene Therapy. 2009; 20 :293-301 - 36.
Bramson JL, Wan Y-H. The efficacy of genetic vaccination is dependent upon the nature of the vector system and antigen. Expert Opinion on Biological Therapy. 2002; 2 :75-85 - 37.
Emanuelsson O, Nielsen H, Brunak S, von Heijne G. Predicting subcellular localization of proteins based on their N-terminal amino acid sequence. Journal of Molecular Biology. 2000; 300 :1005-1016 - 38.
Gómez CE, Perdiguero B, García-Arriaza J, Esteban M. Clinical applications of attenuated MVA poxvirus strain. Expert Review of Vaccines. 2013; 12 :1395-1416 - 39.
Miner JN, Hruby DE. Vaccinia virus: A versatile tool for molecular biologists. Trends in Biotechnology. 1990; 8 :20-25 - 40.
Jacobs BL et al. Vaccinia virus vaccines: Past, present and future. Antiviral Research. 2009; 84 :1-13 - 41.
McMahon-Pratt D et al. Recombinant vaccinia viruses expressing GP46/M-2 protect against Leishmania infection. Infection and Immunity. 1993; 61 :3351-3359 - 42.
Webb JR et al. Human and murine immune responses to a novel Leishmania major recombinant protein encoded by members of a multicopy gene family. Infection and Immunity. 1998; 66 :3279-3289 - 43.
Melby PC, Yang J, Zhao W, Perez LE, Cheng J. Leishmania donovani p36(LACK) DNA vaccine is highly immunogenic but not protective against experimental visceral leishmaniasis. Infection and Immunity. 2001; 69 :4719-4725 - 44.
Matos DCS et al. Kinetoplastid membrane protein-11 is present in promastigotes and amastigotes of Leishmania amazonensis and its surface expression increases during metacyclogenesis. Memórias do Instituto Oswaldo Cruz. 2010; 105 :341-347 - 45.
Carson C et al. A prime/boost DNA/modified vaccinia virus Ankara vaccine expressing recombinant Leishmania DNA encoding TRYP is safe and immunogenic in outbred dogs, the reservoir of zoonotic visceral leishmaniasis. Vaccine. 2009; 27 :1080-1086 - 46.
Jayakumar A, Castilho TM, Park E, Goldsmith-Pestana K, Blackwell JM, McMahon-Pratt D. TLR1/2 activation during heterologous prime-boost vaccination (DNA-MVA) enhances CD8+ T cell responses providing protection against Leishmania (Viannia). PLoS Neglected Tropical Diseases. 2011; 5 :e1204 - 47.
Ramos I et al. Heterologous prime-boost vaccination with a non-replicative vaccinia recombinant vector expressing LACK confers protection against canine visceral leishmaniasis with a predominant Th1-specific immune response. Vaccine. 2008; 26 :333-344 - 48.
Pérez-Jiménez E, Kochan G, Gherardi MM, Esteban M. MVA-LACK as a safe and efficient vector for vaccination against leishmaniasis. Microbes and Infection. 2006; 8 :810-822 - 49.
Sánchez-Sampedro L, Gómez CE, Mejías-Pérez E, Sorzano CO, Esteban M. High quality long-term CD4+and CD8+effector memory populations stimulated by DNA-LACK/MVA-LACK regimen in Leishmania major BALB/C model of infection. PLoS One. 2012; 7 :e38859 - 50.
Sanchez-Sampedro L, Gomez CE, Mejias-Perez E, Perez-Jimenez E, Oliveros JC, Esteban M. Attenuated and replication-competent Vaccinia virus strains M65 and M101 with distinct biology and immunogenicity as potential vaccine candidates against pathogens. Journal of Virology. 2013; 87 :6955-6974 - 51.
Fernández L et al. Antigenicity of leishmania-activated C-kinase antigen (LACK) in human peripheral blood mononuclear cells, and protective effect of prime-boost vaccination with pCI-neo-LACK plus attenuated LACK-expressing vaccinia viruses in hamsters. Frontiers in Immunology. 2018; 9 :843 - 52.
Sánchez-Sampedro L, Mejías-Pérez E, S Sorzano CÓ, Nájera JL, Esteban M. NYVAC vector modified by C7L viral gene insertion improves T cell immune responses and effectiveness against leishmaniasis. Virus Research. 2016; 220 :1-11 - 53.
Guha R et al. Heterologous priming-boosting with DNA and vaccinia virus expressing kinetoplastid membrane protein-11 induces potent cellular immune response and confers protection against infection with antimony resistant and sensitive strains of Leishmania (Leishmania) donovani. Vaccine. 2013; 31 :1905-1915