A heat shock protein based polyvalent vaccine targeting HSV-2: CD4+ and CD8+ cellular immunity and protective efficacy
Introduction
Genital herpes, caused primarily by infection with HSV-2, is a persistent condition in humans which has eluded all prophylactic and therapeutic vaccine development efforts. Most recently, an 8000 subject placebo controlled prophylactic vaccine study in HSV-2 seronegative women failed to show clinical activity [1]. While it is possible that the narrow antigen composition of this vaccine which consisted only of glycoprotein D was a key factor contributing to its lack of efficacy, a placebo controlled study of a single gene deletion HSV-2 replication defective virus vaccine also lacked efficacy in the therapeutic setting [2]. These two studies are representative bookends of the approaches to vaccine development in the herpes field. Reasons for their failure can be speculated: the widely tested glycoproteins D (and B) may simply not be protective antigens in humans given the wealth of evidence of their eliciting neutralizing antibodies in humans [3]. Additionally, genetically attenuated live virus vaccines which theoretically could present a vast number of antigens to the immune system may lack sufficient immunogenicity due to the built-in replication blocks which minimize virulence. Recent evidence collected in HSV-2 seropositive as well as in HSV-2 immune seronegative subjects has demonstrated the considerable breadth of viral antigens recognized by T cells [4], [5], [6], [7]. The data point to the distinct possibility that a herpes vaccine based on a single or small number of antigens may be unlikely to be protective in the genetically diverse human population regardless of how effectively it primes antibody and/or T cell responses. Here, we report the results of our attempt to address the twin challenges of finding the protective antigens in HSV-2 and delivering them in a manner which activates the immune system robustly with particular focus on cellular immunity believed to be crucial for viral control [8], [9], [10].
The HSV-2 vaccine described here is the rodent equivalent of a heat shock protein based genital herpes vaccine candidate, also named HerpV, which recently completed Phase 1 clinical testing (A. Wald, see submitted companion manuscript). HSP–peptide complexes isolated from infected or malignant cells represent a natural antigenic fingerprint of those cells [11]. Such complexes can also be reconstituted in vitro which offers the possibility of selecting and synthesizing specific antigen sequences of interest which may be delivered with recombinant HSP [12]. Upon injection into a host, HSP–peptide complexes bind to HSP receptors on antigen presenting cells leading to internalization of the complexes and presentation of the chaperoned peptides by MHC class I and II molecules [13], [14], [15], [16]. In this manner immunization with HSP–peptide complexes primes/boosts T cell responses specific for the chaperoned peptides [11]. Using the approach of reconstituting HSP–peptide complexes in vitro, Rouse and co-workers demonstrated the immunogenicity and protective activity of mouse HSP70 complexed with defined MHC class I and II binding peptides of gD, gB and ICP-27 in the acute and memory phase in mice [17], [18]. Similarly, Navaratnam et al. used gp96, another stress protein, to form in vitro complexes with three mouse cytotoxic T cell (CTL) epitopes of the bovine herpes virus (BHV) serine/threonine protein kinase and glycoprotein H [19]. Such complexes elicited CTLs which killed peptide pulsed as well as BHV infected target cells. HSP vaccines have been widely tested in animal models of other infectious diseases as well, including tuberculosis, listeria and LCMV [20], [21]. Immunization of cancer patients with autologous cancer-derived HSP–peptide complexes has also consistently shown immunological and clinical activity [22], [23], [24], [25], [26], [27]. The saponin QS-21, a component of the HerpV vaccine approach, has also demonstrated potent adjuvant activity in multiple indications over the past 20 years in animal models and human clinical trials [28], [29].
Our results show that vaccination with the multi-valent HerpV candidate vaccine induces an immune response to multiple epitopes and protection from HSV-2 in several animal models. A companion article describes the results of a Phase 1 safety and immunogenicity study of HerpV in HSV-2+ subjects (A. Wald, see submitted companion manuscript).
Section snippets
Selection of HSV-2 peptides in HerpV
HerpV used in the rodent studies consists of 32 synthetic HSV-2 derived peptides (each 35 amino acids long) non-covalently complexed with HSP70 purified from normal tissue (described below). The peptide sequences are derived from 10 tegument, 8 envelope and 4 other HSV-2 proteins, representative of proteins expressed during all phases of viral replication [30] (Table 1). The rationale by which the ∼85 known HSV-2 proteins were winnowed to 22 proteins from which the 32 peptides in HerpV are
Discussion
This study is the first demonstration of immunogenicity and protective efficacy of a polyvalent herpes vaccine comprising a large array of long synthetic viral peptides, which do not contain any previously defined protective T cell epitopes. The finding that HerpV stimulates not only CD4+ but also CD8+ T cells fulfills what are likely to be key requirements for a successful herpes vaccine. Biological activity of the peptides was shown to be dependent on HSP70, to which the peptides were
HSP70 and peptides
Mouse and guinea pig HSP70 was purified from mouse and guinea pig liver and kidney tissue lysate by ATP agarose affinity and DEAE Sepharose anion exchange chromatography columns, concentrated and subjected to 0.22 μM filtration. Human Hsc70 cDNA was sourced directly from ATCC (IMAGE Consortium Code 612844), sequenced to confirm identity and expressed in BL21 (DE3) E. coli using the pET-24a(+) expression vector (Novagen). rh-Hsc70 protein was purified from lysed E. coli cell paste by Q Sepharose
Acknowledgements
For technical expertise and insightful discussions: Nicholas Messinese, Aaron Wilson, Erik Devereaux, Hao Tang and Andrei Varnavski.
Conflict of interest statement: AM, CM, HC, JP, KL, AL, RMC, AT, SM and DLL each had/have direct ownership of stock of Agenus, Inc. PKS was a consultant to Agenus, Inc. and has direct ownership of Agenus, Inc. stock.
References (45)
- et al.
A randomized controlled trial of a replication defective (gH deletion) herpes simplex virus vaccine for the treatment of recurrent genital herpes among immunocompetent subjects
Vaccine
(2006) - et al.
CD91 is a common receptor for heat shock proteins gp96, hsp90, hsp70, and calreticulin
Immunity
(2001) - et al.
Involvement of LOX-1 in dendritic cell-mediated antigen cross-presentation
Immunity
(2002) - et al.
Heat shock protein-peptide complexes elicit cytotoxic T-lymphocyte and antibody responses specific for bovine herpesvirus 1
Vaccine
(2001) - et al.
An adjuvant autologous therapeutic vaccine (HSPPC-96; vitespen) versus observation alone for patients at high risk of recurrence after nephrectomy for renal cell carcinoma: a multicentre, open-label, randomised phase III trial
Lancet
(2008) - et al.
Advances in saponin-based adjuvants
Vaccine
(2009) - et al.
Immunity induced by DNA immunization with herpes simplex virus type 2 glycoproteins B and C
Vaccine
(1999) Biochemical, cell biological and immunological issues surrounding the endoplasmic reticulum chaperone GRP94/gp96
Curr Opin Immunol
(1998)- [1] GSK provides update on Herpevac trial for women evaluating Simplirix™ (Herpes Simplex Vaccine) 2010. Available...
- et al.
A recombinant glycoprotein vaccine for herpes simplex virus type 2: safety and immunogenicity
Ann Intern Med
(1995)
Diversity of the CD8+ T-cell response to herpes simplex virus type 2 proteins among persons with genital herpes
J Virol
Diversity in CD8(+) T cell function and epitope breadth among persons with genital herpes
J Clin Immunol
Detailed characterization of T cell responses to herpes simplex virus-2 in immune seronegative persons
J Immunol
T cell immunity to herpes simplex viruses in seronegative subjects: silent infection or acquired immunity?
J Immunol
Clearance of HSV-2 from recurrent genital lesions correlates with infiltration of HSV-specific cytotoxic T lymphocytes
J Clin Invest
Severe genital herpes infections in HIV-infected individuals with impaired herpes simplex virus-specific CD8+ cytotoxic T lymphocyte responses
Proc Natl Acad Sci USA
The ‘immunologic advantage’ of HIV-exposed seronegative individuals
AIDS
Roles of heat-shock proteins in innate and adaptive immunity
Nat Rev Immunol
Heat shock protein-peptide complexes, reconstituted in vitro, elicit peptide-specific cytotoxic T lymphocyte response and tumor immunity
J Exp Med
A mechanism for the specific immunogenicity of heat shock protein-chaperoned peptides
Science
High efficiency CD91- and LOX-1-mediated re-presentation of gp96-chaperoned peptides by MHC II molecules
Cancer Immun
Immunization with chaperone-peptide complex induces low-avidity cytotoxic T lymphocytes providing transient protection against herpes simplex virus infection
J Virol
Cited by (40)
Biologic interactions between HSV-2 and HIV-1 and possible implications for HSV vaccine development
2019, VaccineCitation Excerpt :While an effective prophylactic vaccine is the ultimate goal, past trials were not successful [11,12]. A deeper understanding of the mucosal immune response to HSV-2 [8,13,14], and development of vaccine candidates eliciting broad immunologic responses [15–18], has stoked optimism that a prophylactic vaccine may be possible. In addition to benefits for those infected, therapeutic vaccines are a likely first step in the pathway towards a prophylactic vaccine and have shown partial efficacy in Phase II trials [18–21].
Genital ulcers caused by herpes simplex virus
2019, Enfermedades Infecciosas y Microbiologia ClinicaEvolution of rational vaccine designs for genital herpes immunotherapy
2016, Current Opinion in VirologyCitation Excerpt :Similarly, Agenus Inc. is developing HerpV, a vaccine comprised of 32 HSV-2 peptides, complexed with an HSP70 chaperone and QS-21 adjuvant; peptides were selected based on algorithms predicting HLA binding, synthesis feasibility, and proteasomal processing. Although the selected peptide epitopes originate from proteins spanning all classes of herpes proteins (immediate early to late and capsid to envelope proteins), the algorithms were not entirely unbiased, since 32 proteins were rationally chosen as input for the in silico analysis [37]. HerpV significantly induced CD4+, and at a lesser frequency, CD8+ T cell responses to HSV-2 antigens in humans, validating the computational approach [38•].
Status of prophylactic and therapeutic genital herpes vaccines
2014, Current Opinion in VirologyCitation Excerpt :HerpV is another immunotherapeutic vaccine in clinical trials. The vaccine contains recombinant human heat shock protein-70 combined with thirty-two HSV-2 peptide antigens and QS-21 Stimulon, which is a T-cell and antibody adjuvant derived from the soap bark (Quillaja saponaria) tree [73,74••]. Subjects with a history of herpes recurrences will receive 3 injections of HerpV or placebo at two-week intervals.
Generating protective immunity against genital herpes
2013, Trends in ImmunologyCitation Excerpt :This vaccine elicits IFN-γ-producing cells in mice. When tested for therapeutic activity in guinea pigs, although there was no significant decrease in lesion score or mean duration, there was a significant decrease in the frequency of recurrences [71]. Testing in humans during a Phase I trial shows that the vaccine is safe and well-tolerated, and can induce T cell responses [72].
- 1
Current address: National Institute of Allergy and Infectious Diseases.
- 2
Current address: Pfizer Vaccine Research.
- 3
Current address: Novartis.
- 4
Current address: GlaxoSmithKline.
- 5
Current address: Sanofi Pasteur.
- 6
Current address: NKT Therapeutics Inc.
- 7
These authors contributed equally to this work.