Mucosal vaccination with a live recombinant rhinovirus followed by intradermal DNA administration elicits potent and protective HIV-specific immune responses

www.nature.com/scientificreports OPEN received: 04 July 2016 accepted: 18 October 2016 Published: 17 November 2016 Mucosal vaccination with a live recombinant rhinovirus followed by intradermal DNA administration elicits potent and protective HIVspecific immune responses Khamis Tomusange1, Danushka Wijesundara1, Jason Gummow1, Steve Wesselingh2, Andreas Suhrbier3, Eric J. Gowans1,* & Branka Grubor-Bauk1,* Mucosal immunity is deemed crucial to control sexual transmission of human immunodeficiency virus (HIV). Herein we report the efficacy of a mucosal HIV vaccine strategy comprising intranasal (IN) vaccination with a cocktail of live recombinant human rhinoviruses (HRVs) encoding overlapping fragments of HIV Gag and full length Tat (rHRV-Gag/Tat) followed by intradermal (ID) vaccination with DNA vaccines encoding HIV Gag and Tat (pVAX-Gag-Tat). This heterologous prime-boost strategy will be referred to hereafter as rHRV-DNA. As a control, IN vaccination with wild type (wt)-HRV-A1 followed by a single ID dose of pVAX (wt-HRV-A1/pVAX vaccination) was included. rHRV-DNA vaccination elicited superior multi-functional CD8+T cell responses in lymphocytes harvested from mesenteric lymph nodes and spleens, and higher titres of Tat-specific antibodies in blood and vaginal lavages, and reduced the viral load more effectively after challenge with EcoHIV, a murine HIV challenge model, in peritoneal macrophages, splenocytes and blood compared compared with wt-HRV-A1/pVAX vaccination or administration of 3 ID doses of pVAX-Gag-Tat (3X pVAX-Gag-Tat vaccination). These data provide the first evidence that a rHRV-DNA vaccination regimen can induce HIV-specific immune responses in the gut, vaginal mucosa and systemically, and supports further testing of this regimen in the development of an effective mucosally-targeted HIV-1 vaccine. A potential reason why previous HIV vaccine trials were ineffective1–3 or modestly effective4 is the failure to generate effective mucosal immunity5. A majority of HIV transmissions occur via genito-urinary or genito-rectal mucosal surfaces6 and extensive CD4+ T cell depletion occurs in the gastrointestinal mucosa after infection7. This highlights the need to develop vaccines capable of eliciting protective HIV-specific immune responses at these surfaces. Moreover, previous HIV vaccine strategies focused on systemic vaccination, which induced little or no protective immune responses at the mucosa5. Therefore, mucosal vaccination strategies able to elicit HIV-specific immunity both systemically and at mucosal surfaces are being actively pursued8. Ideally, mucosal HIV vaccines should generate broadly neutralizing antibodies (bNAbs) against the envelope proteins to prevent primary HIV infection as has been observed in animal studies involving passive transfer of broadly neutralizing antibodies9. However, due to the recognised difficulties in designing vaccines capable of eliciting Env-specific bNAbs10, a vaccine capable of eliciting high titre anti-Tat NAb might be a feasible alternative to controlling HIV replication and delaying disease onset11. An effective HIV vaccine should also induce robust poly-functional T cell mediated immunity (CMI) against the relatively conserved Gag proteins, viz. responses similar to those seen in long-term non-progressors12,13. Among the several strategies that have been developed to generate mucosal HIV vaccines is the use of mucosally transmitted replication-competent viral vectors14. These vectors usually establish an infection that 1 Virology Laboratory, Basil Hetzel Institute, Discipline of Surgery, University of Adelaide, Adelaide, South Australia, Australia. 2South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia. 3QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia. *These authors jointly supervised this work. Correspondence and requests for materials should be addressed to B.G-B (email: ) Scientific Reports | 6:36658 | DOI: 10.1038/srep36658 1 www.nature.com/scientificreports/ mimics a natural viral infection, efficiently deliver immunogens to mucosal antigen presenting cells (APCs), and facilitate the development of long-lasting humoral and CMI15 without the need for addition of adjuvants14. Several replication-competent viral vectors including adenovirus, poliovirus, influenza virus, poxvirus and cytomegalovirus vectors have been developed and tested as HIV vaccines, with promising results in large animal models14,15, particularly when used in heterologous prime-boost vaccination regimens. Previously, polioviruses, which are transmitted via mucosal surfaces16, were studied as potential viral vectors for HIV vaccine development16,17 and vaccination with a cocktail of live recombinant polioviruses generated protective immunity against intravaginal challenge with SIVmac251 in 4/7 (57%) vaccinated macaques17. However, replication-competent poliovirus vectors have not advanced to human clinical trials mainly due to the high level of pre-existing vaccine-induced immunity in the community18 which has been shown to limit the efficacy of virus-vectored vaccines1. Like polioviruses, human rhinoviruses (HRVs) are classified in the Picornaviridae and share many characteristics, including their genome organisation and mode of transmission19. HRVs are transmitted via the nasal mucosa20 making them potential vaccine vectors to elicit mucosal immunity. We have previously developed a series of replication-competent, genetically stable recombinant HRV serotype-A1 viruses (rHRV-Gag 1–5 and rHRV-Tat) by inserting discrete overlapping fragments of the HIV gag gene or the full length tat gene, into the junction of the genes encoding the structural proteins and the non-structural proteins (the P1/P2 junction)21. We have now mixed these rHRVs into a single cocktail vaccine suitable for intranasal (IN) administration, a route that has been shown to generate pan-mucosal and systemic immunity8. Furthermore, IN vaccination is considered to be safe, well tolerated, easily administered and inexpensive8, and consequently, the rHRV-Gag/Tat vaccine represents a potential cost-effective HIV vaccine candidate for use in low-income countries. Herein we describe the immune responses against Gag and Tat after vaccination of mice IN with rHRV-Gag/Tat followed by ID delivery of DNA encoding Gag and Tat, and evaluate the efficacy of this regimen after challenge with ecotropic murine leukaemia HIV (EcoHIV). Results rHRV-DNA prime-boost vaccination elicits robust CMI. A robust CMI to HIV Gag appears to correlate with control of HIV infection in humans12 and non-human primates22,23. We previously showed that vaccination of mice with 3 doses of pVAX-Gag-PRF elicited broad, poly-functional Gag-specific CMI able to control EcoHIV after challenge24, and that vaccination with pVAX-sTat-IMX313 elicited high titre anti-Tat responses that also controlled EcoHIV infection post challenge25. 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