Increased detection of proliferating, polyfunctional, HIV‐1‐specific T cells in DNA‐modified vaccinia virus Ankara‐vaccinated human volunteers by cultured IFN‐γ ELISPOT assay

Abstract

Induction of a long-term immunological memory, which can expand and defend the host upon pathogen encounter, is the ''holy grail'' of vaccinology. Here, using a sensitive cultured IFN-c ELISPOT assay, we show that 50% (15 out of 30) of healthy, HIV-1/2-uninfected volunteers who received pTHr.HIVA DNA prime-modified vaccinia virus Ankara. HIVA boost vaccine regimen 1 to 3 1/2 years ago had detectable HIV-1-specific T-cell responses. These T cells, predominantly of the CD4 1 subtype, could proliferate and produce multiple cytokines in response to in vitro peptide stimulation. Peptide mapping studies showed that the vaccine-induced CD4 1 T cells were mostly directed toward epitopes targeted in HIV-1-infected individuals. In addition, we used the same assay to re-evaluate 51 volunteers from past vaccine trial IAVI-006 and corrected the previously reported 10% of vaccine responders to 50%. Thus, we confirmed that cultured assays are a valuable tool for studying T-cell memory. These results are discussed in the context of the current state-of-affairs of the HIV-1 vaccine field.Key words: Clinical trial . DNA-MVA vaccines . HIV-1 . Memory T cells IntroductionDespite proven methods of prevention and/or decrease of transmission, all efforts to slow the rate of new HIV-1 infections are failing in most countries around the world, including the USA (http://www.unaids.org/). The best solution to control of the HIV-1 epidemic remains the development of a safe, effective and accessible preventive vaccine [1]. The aim of vaccination is induction of long-lived, pathogen-specific circulating antibodies and cellular immunological memory, which together provide a faster and more efficient defense of the host following exposure to the pathogen. A central role in both the T-and B-cell memory development is played by CD4 1 T cells [2,3], the functionality of which is tuned by the non-adaptive innate response [4]. It is the CD4 1 T-cell population that is decimated by HIV-1-infection, which eventually leads to opportunistic infections [5,6].The long-term aim of our effort is development of an effective HIV-1 vaccine. In particular, we explore strategies for eliciting HIV-1-specific T-cell responses, which could on their own, or together with vaccine-induced anti-HIV-1 antibodies, limit tissue damage during HIV-1 infection. Our first vaccine platform was designed as a heterologous DNA prime-modified vaccinia virus Ankara (MVA) boost regimen delivering a common immunogen HIVA, which consists of consensus African clade A Gag p24 and The most sensitive assay employed and validated by the IAVI-016 trial was the IFN-g ELISPOT assay combined with a prior 10-day-culture expansion of PBMC using immunogen-derived peptides and externally supplemented cytokines. This so called cultured IFN-g ELISPOT assay increased the frequencies of specific T cells more than 24-fold compared with the ex vivo assay and detected vaccine-induced HIV-1-specific responses in all (8 out of 8) IAVI-016 subjects who received the pTHr.HIVA DNA-MVA.HIVA regimen [14]. Thes...

Novel RecombinantMycobacterium bovisBCG, Ovine Atadenovirus, and Modified Vaccinia Virus Ankara Vaccines Combine To Induce Robust Human Immunodeficiency Virus-Specific CD4 and CD8 T-Cell Responses in Rhesus Macaques

“…The HIVA construct (21) has been an extremely useful model immunogen both for clinical (14,20,65) and preclinical (30,31,36,48) on May 7, 2018 by guest http://jvi.asm.org/ in mice and Mamu-A*01 ϩ rhesus macaques continue to be mapped, and the corresponding CD8 T-cell responses are being characterized in greater detail. However, there is no appropriate challenge available for the vaccinated animals because HIVA is designed for humans and is, therefore, derived from HIV-1 antigens; HIV-1 does not replicate in rhesus macaques.…”

Enumeration and Characterization of Human Memory T Cells by Enzyme-Linked Immunospot Assays

“…In recent studies, cultured ELISPOT assays have proven to be a valuable tool for studying T-cell memory in HIV-1 vaccine trials [52, 53]. …”

MVA-nef induces HIV-1-specific polyfunctional and proliferative T-cell responses revealed by the combination of short- and long-term immune assays

“…In fact, both the ex vivo IFN-g-based ICS performed in a previous study 4 and the polychromatic ICS performed in this study underestimated the vaccine-induced Nef-specific CD8 T-cell responses clearly detected by the proliferation assay. Recently, Winstone et al 50 used a cultured IFN-g ELISPOT assay to reexamine vaccine-induced T-cell responses in trial IAVI-006. The cultured IFN-g ELISPOT assay detected five times more vaccine-induced responses in study participants as compared with the classical ELISPOT.…”