Although MERS-CoV has not yet acquired extensive distribution, being mainly confined to the Arabic and Korean peninsulas, it could adapt to spread more readily among humans and thereby become pandemic. Therefore, the development of a vaccine is mandatory. The integration of antigen-coding genes into recombinant MV resulting in coexpression of MV and foreign antigens can efficiently be achieved. Thus, in combination with the excellent safety profile of the MV vaccine, recombinant MV seems to constitute an ideal vaccine platform. The present study shows that a recombinant MV expressing MERS-S is genetically stable and induces strong humoral and cellular immunity against MERS-CoV in vaccinated mice. Subsequent challenge experiments indicated protection of vaccinated animals, illustrating the potential of MV as a vaccine platform with the potential to target emerging infections, such as MERS-CoV.

The Middle East respiratory syndrome coronavirus (MERS-CoV In 2012 a novel human betacoronavirus associated with severe respiratory disease emerged in Saudi Arabia (1). Due to its geographic distribution, this new virus was classified as Middle East respiratory syndrome coronavirus (MERS-CoV) (2). MERS-CoV is associated with high fatality rates (3, 4), and case numbers globally have increased to 909 laboratory-confirmed cases with 331 fatalities (as of 21 November 2014 [http://www.who.int/csr/don/ 21-november-2014-mers/en/]). In parallel, the geographic distribution has expanded (4). MERS-CoV is the second emerging CoV with severe pathogenicity in humans within 10 years after the severe acute respiratory syndrome coronavirus (SARS-CoV) that infected approximately 8,000 people worldwide during its spread in 2003 (5). Human-to-human transmissions have been reported for MERS-CoV, but transmissibility seems to be inefficient (6, 7). MERS-CoV persists in animal reservoirs, i.e., dromedary camels (8), and transmission events between camels and contact persons have been reported (7-10). Thus, MERS-CoV infection of men has zoonotic origins, similar to SARS-CoV, but unlike SARS-CoV, where bats have been identified as the original virus reservoir, bats have been reported to host only closely related viruses of MERSCoV (11). However, the only small-animal model developed so far involves type I interferon receptor (IFNAR)-deficient mice expressing human dipeptidyl peptidase 4 (huDPP4; CD26), the entry receptor of MERS-CoV (12), in the lung after intranasal administration of huDPP4-expressing adenoviral vectors (13). MERS-CoV causes symptoms in humans similar to those of SARS-CoV infection, such as severe pneumonia with acute respi-

؉ T lymphocytes are a mainstay of antitumoral immune responses, PTVs could be engineered for the transfer of specific tumor antigens provoking tailored antitumoral immunity. Therefore, PTVs can be used as safe and efficient alternatives to gene transfer vectors or live attenuated replicating vector platforms, avoiding genotoxicity or general toxicity in highly immunocompromised patients, respectively. Thereby, the potential for easy envelope exchange allows the circumventing of neutralizing antibodies, e.g., during repeated boost immunizations. V accination is the administration of one or more immunogens, the vaccine, into patients to trigger antigen-specific adaptive immune responses to prevent (prophylactic vaccination) or to treat (therapeutic vaccination) disease. Vaccines can be classified into several subtypes. Among these are live attenuated replicating vaccines, inactivated vaccines, subunit vaccines, DNA vaccines, or recombinant vector vaccines (for review, see reference 1). Wellknown live attenuated vaccines are, e.g., those against measles (2) or mumps (3). These vaccines replicate but have been attenuated to become apathogenic. The immune responses triggered by live attenuated vaccines are similar to those induced by the pathogenic form of the microbe (4, 5) and involve both the cellular and humoral arms of the immune system. However, attenuated replicating pathogens may carry an inherent risk of reversion to the parental virulent form by in vivo passaging during vaccination, as observed for the Sabin strain used as a polio vaccine (6), or may still be pathogenic in highly immunocompromised patients (7), depending on the respective degree of attenuation of the vaccine strains. On the other hand, inoculation of solely proteinaceous antigens (such as the hepatitis B virus vaccine [8]) or antigenencoding genes (as a DNA vaccine) is regarded as safe but relatively inefficient (9).As an alternative to such vaccines, the genes encoding an antigen can be transferred into cells and thereby presented to the immune system by using recombinant vaccine vectors. For that purpose, an attenuated vector is utilized as a carrier for the antigen-encoding sequences of another pathogen. Thereby, they are

Proteasome catalyzed peptide splicing (PCPS) of cancer-driving antigens could generate attractive neoepitopes to be targeted by TCR-based adoptive T cell therapy. Based on a spliced peptide prediction algorithm TCRs were generated against putative KRASG12V and RAC2P29L derived neo-splicetopes with high HLA-A*02:01 binding affinity. TCRs generated in mice with a diverse human TCR repertoire specifically recognized the respective target peptides with high efficacy. However, we failed to detect any neo-splicetope specific T cell response when testing the in vivo neo-splicetope generation and obtained no experimental evidence that the putative KRASG12V- and RAC2P29L-derived neo-splicetopes were naturally processed and presented. Furthermore, only the putative RAC2P29L-derived neo-splicetopes was generated by in vitro PCPS. The experiments pose severe questions on the notion that available algorithms or the in vitro PCPS reaction reliably simulate in vivo splicing and argue against the general applicability of an algorithm-driven 'reverse immunology' pipeline for the identification of cancer-specific neo-splicetopes.

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