Albert Bensaïd

Middle East respiratory syndrome coronavirus (MERS-CoV) infections have led to an ongoing outbreak in humans, which was fueled by multiple zoonotic MERS-CoV introductions from dromedary camels. In addition to the implementation of hygiene measures to limit further camel-to-human and human-to-human transmissions, vaccine-mediated reduction of MERS-CoV spread from the animal reservoir may be envisaged. Here we show that a modified vaccinia virus Ankara (MVA) vaccine expressing the MERS-CoV spike protein confers mucosal immunity in dromedary camels. Compared with results for control animals, we observed a significant reduction of excreted infectious virus and viral RNA transcripts in vaccinated animals upon MERS-CoV challenge. Protection correlated with the presence of serum neutralizing antibodies to MERS-CoV. Induction of MVA-specific antibodies that cross-neutralize camelpox virus would also provide protection against camelpox.

In this study, two monoclonal antibodies, IL-A29 and CC15, are described that identify a novel bovine cell surface marker of 215/300 kDa. The antibodies reacted with a discrete population of resting lymphocytes in peripheral blood which, in young animals, constituted about 25% of the mononuclear cells. Thymus, lymph nodes and spleen contained less than 5% positive cells. These cells were negative for surface Ig, a monocyte/granulocyte marker, and the T lymphocyte antigens CD2, CD6, CD4 and CD8. Immunohistological analyses revealed the presence of IL-A29/CC15-positive lymphocytes in the thymic medulla, in the outer cortex of lymph nodes, in the marginal zones of the spleen, in the dermal and epidermal layers of the skin and in the lamina propria of the gut. The IL-A29/CC15+ cells in unfractionated blood mononuclear cells responded in autologous and allogeneic mixed lymphocyte cultures, and when purified they responded to concanavalin A in the presence of recombinant interleukin 2. These observations suggested this population of cells belonged to the T cell lineage. In order to unambiguously define their lineage, cDNA clones encoding bovine T cell receptor (TcR) and CD3 proteins were isolated. Northern blot analyses of IL-A29/CC15+ cell populations and of established cell lines of various lineages demonstrated that they expressed TcR delta and CD3 gamma, delta and epsilon mRNA: TcR alpha was not expressed, whereas only a truncated form of TcR beta mRNA was present. These results indicate that the IL-A29 and CC15 antibodies define a unique population of CD4-CD8-, gamma/delta T cells.

UNLABELLED: African swine fever is one of the most devastating pig diseases, against which there is no vaccine available. Recent work from our laboratory has demonstrated the protective potential of DNA vaccines encoding three African swine fever viral antigens (p54, p30, and the hemagglutinin extracellular domain) fused to ubiquitin. Partial protection was afforded in the absence of detectable antibodies prior to virus challenge, and survival correlated with the presence of a large number of hemagglutinin-specific CD8(+) T cells in blood. Aiming to demonstrate the presence of additional CD8(+) T-cell determinants with protective potential, an expression library containing more than 4,000 individual plasmid clones was constructed, each one randomly containing a Sau3AI restriction fragment of the viral genome (p54, p30, and hemagglutinin open reading frames [ORFs] excluded) fused to ubiquitin. Immunization of farm pigs with the expression library yielded 60% protection against lethal challenge with the virulent E75 strain. These results were further confirmed by using specific-pathogen-free pigs after challenging them with 10(4) hemadsorbing units (HAU) of the cell culture-adapted strain E75CV1. On this occasion, 50% of the vaccinated pigs survived the lethal challenge, and 2 out of the 8 immunized pigs showed no viremia or viral excretion at any time postinfection. In all cases, protection was afforded in the absence of detectable specific antibodies prior to challenge and correlated with the detection of specific T-cell responses at the time of sacrifice. In summary, our results clearly demonstrate the presence of additional protective determinants within the African swine fever virus (ASFV) genome and open up the possibility for their future identification. IMPORTANCE: African swine fever is a highly contagious disease of domestic and wild pigs that is endemic in many sub-Saharan countries, where it causes important economic losses and is currently in continuous expansion across Europe. Unfortunately, there is no treatment nor an available vaccine. Early attempts using attenuated vaccines demonstrated their potential to protect pigs against experimental infection. However, their use in the field remains controversial due to safety issues. Although inactive and subunit vaccines did not confer solid protection against experimental ASFV infection, our DNA vaccination results have generated new expectations, confirming the key role of T-cell responses in protection and the existence of multiple ASFV antigens with protective potential, more of which are currently being identified. Thus, the future might bring complex and safe formulations containing more than a single viral determinant to obtain broadly protective vaccines. We believe that obtaining the optimal vaccine formulation it is just a matter of time, investment, and willingness.

Monoclonal antibody (mAb) IL-A17 characterizes a subset of bovine T lymphocytes. IL-A17 recognizes a 34,000-35,000 MW doublet, designated BoT8, which is expressed on the surface of approximately 20% of peripheral blood mononuclear leucocytes (PBM), a subpopulation of lymphocytes in T-dependent areas of lymph nodes and spleen, and about 70% of thymocytes. This molecule is not expressed on B lymphocytes, monocytes/macrophages or granulocytes. Double labelling of PBM showed that the BoT8+ population is distinct from the T lymphocyte subset expressing BoT4. BoT8+ lymphocytes purified with a fluorescence-activated cell sorter (FACS) proliferated poorly in response to mitogenic and alloantigenic stimulation in the absence of exogenous growth factors. IL-A17 had no inhibitory effect on proliferation of PBM to mitogens (Con A and PHA) or alloantigens and no measurable effect on the in vitro generation of cytolytic effector cells. However, in some experiments IL-A17 was found to block partially allospecific cytolytic function mediated by bulk effector cell populations when included in 51Cr-release assays. Fractionation of effector cells generated in an allogeneic mixed leucocyte culture (MLC) demonstrated that cytotoxic cells specific for class I major histocompatibility complex (MHC) antigens reside within the BoT8+ population. Based on these data, and information reported elsewhere on alloreactive bovine T-cell clones, BoT8 is considered to be analogous to CD8 in humans and equivalent molecules in other species.