CD4 and CD8 T Cell Responses to the M. tuberculosis Ag85B-TB10.4 Promoted by Adjuvanted Subunit, Adenovector or Heterologous Prime Boost Vaccination Tara Elvang1,2, Jan P. Christensen2, Rolf Billeskov1, Truc Thi Kim Thanh Hoang 1 , Peter Holst2, Allan Randrup Thomsen2, Peter Andersen1, Jes Dietrich1* 1 Department of Infectious Disease Immunology, Statens Serum Institute, Copenhagen, Denmark, 2 Institute of Medical Microbiology and Immunology, the Panum Institute, Copenhagen, Denmark Abstract Background: Although CD4 T cells are crucial for defense against M.tb, it is still not clear whether the optimal response against M.tb in fact involves both CD4 and CD8 T cells. To test this, we used a new vaccine strategy that generated a strong balanced T cell response consisting of both CD4 and CD8 T cells. Methods and Findings: To compare CD4 and CD8 responses against Ag85B-TB10.4 (H4), H4 was delivered as a subunit vaccine in cationic liposomes (CAF01), expressed in Ad5 (Ad-H4) or as a heterologous prime boost vaccination. H4/CAF01 induced primarily CD4 T cells and Ad-H4 gave predominantly a CD8 T cell response. In contrast, the heterologous prime boost combination resulted in augmentation of both the CD4 and CD8 response. The majority (.40%) of the CD4 T cells induced by the heterologous prime boost protocol were polyfunctional, and expressed IFN-c+, IL-2+, and TNF-a+, whereas most of the CD8 T cells expressed IFN-c+ and TNF-a+ and possessed strong cytotoxic potential. The heterologous prime boost protocol also gave an increase in protective efficacy against M.tb challenge compared to H4/CAF01 and Ad-H4. Both the H4 specific CD4 and CD8 T cells were recruited to the site of infection, at the onset of infection. However, compared to CD8 T cells, CD4 T cells showed more extensive recruitment and were the main T cell subset proliferating at the site of infection. Conclusions/Significance: Heterologous prime boost based on H4, produced an additive effect on the priming of CD4 and CD8 cells and in terms of the protective capacity of the vaccine, and therefore represent an interesting new vaccine strategy against M.tb. However, CD4 and CD8 T cells respond very differently to live M.tb challenge, in a manner which supports the consensus that CD4 T cells do play the major role during the early stages of an M.tb infection. Citation: Elvang T, Christensen JP, Billeskov R, Thi Kim Thanh Hoang T, Holst P, et al. (2009) CD4 and CD8 T Cell Responses to the M. tuberculosis Ag85B-TB10.4 Promoted by Adjuvanted Subunit, Adenovector or Heterologous Prime Boost Vaccination. PLoS ONE 4(4): e5139. doi:10.1371/journal.pone.0005139 Editor: Leonardo A. Sechi, Universita di Sassari, Italy Received February 10, 2009; Accepted March 16, 2009; Published April 9, 2009 Copyright: 2009 Elvang et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported in part by the Danish Medical Research Council, the Lundbeck Foundation, and the Novo Nordisk Foundation. Tara Elvang and Rolf Billeskov are recipients of PhD scholarships from the Danish Graduate School of Immunology. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: JDI@ssi.dk Introduction Approximately one-third of the world’s population is latently infected with Mycobacterium tuberculosis (M.tb), and understanding the immune mechanisms involved in controlling this chronic disease is of high priority. The major mechanisms of cell-mediated immunity include CD4 Th1-cell mediated activation of macro- phages to destroy intracellular bacterial pathogens, and the central role of IFN-c in the control of tuberculosis has been clearly demonstrated by the susceptibility to mycobacterial infections in mice with a disrupted IFN-c gene and in humans with mutations in genes involved in the IFN-c and IL-12 pathways [1–4].Unlike CD4 T cells, which are crucial in the defence against M.tb, the role of CD8 T cells is not fully resolved. However, numerous studies have indicated that cytotoxic CD8 T cell-mediated killing of infected host cells do play a role in the defence against a M.tb infection [5–10]. Other results in favour of the protective effect of CD8 T cells come from recent studies, showing that lack of the RD-1 region in BCG (compared to M.tb) is responsible for the reduced CD8 T cell response induced by BCG compared to M.tb, and that re-introducing RD-1 into BCG selectively restored the CD8 T cell response and importantly also increased the protective efficacy of the vaccine [11–14]. As a consequence there has recently been increased focus on the CD8 T cells and several new vaccine strategies that target these T cells are currently pursued in many laboratories involved in TB vaccine research. Viral vectors, such as adeno- or vaccinia virus, trigger a Th1-dominated immune response, characterized by potent induction of IFN-c, and are also efficient in inducing a robust CD8 T cell response against their target antigens. One M.tb vaccine of this type is MVA-85A, a replication-deficient recombinant vaccinia virus, expressing anti- gen 85A from M.tb. This vaccine has performed well in animal models where it induces not only CD8 T cells, but also CD4 T cells, and significant protection against M.tb. Results from clinical PLoS ONE | www.plosone.org 1 April 2009 | Volume 4 | Issue 4 | e5139