Respiratory syncytial virus (RSV) causes acute lower respiratory tract infections and is the leading cause of infant hospitalizations. Recently, a promising vaccine antigen based on the RSV fusion protein (RSV F) stabilized in the native prefusion conformation has been described. Here we report alternative strategies to arrest RSV F in the prefusion conformation based on the prevention of hinge movements in the first refolding region and the elimination of proteolytic exposure of the fusion peptide. A limited number of unique mutations are identified that stabilize the prefusion conformation of RSV F and dramatically increase expression levels. This highly stable prefusion RSV F elicits neutralizing antibodies in cotton rats and induces complete protection against viral challenge. Moreover, the structural and biochemical analysis of the prefusion variants suggests a function for p27, the excised segment that precedes the fusion peptide in the polypeptide chain.

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Equine sarcoids, the most common skin tumours in horses, are induced by bovine papillomavirus (BPV). Their clinical appearance varies from small stable patches to aggressively growing masses. Differences in BPV load and mRNA expression and Ki67 and p53 immunostaining among four clinical types (fibroblastic, occult, nodular and verrucous sarcoids) were evaluated to test the hypothesis that the clinical behaviour of equine sarcoids correlates with BPV activity. Viral load and expression of the BPV E2, E5, E6 and E7 genes were determined using quantitative real-time PCR. The proliferative fraction (PF) of the tumours was determined by Ki67 immunostaining and expression of p53 was analysed by immunohistochemistry. Nodular sarcoids showed a significantly higher viral load than the other types. A significant overall difference among the four types was observed for E2, E5, E6 and E7 mRNA expression. Nodular sarcoids showed the highest expression level for each BPV gene examined, followed by verrucous, fibroblastic and occult tumours. Viral DNA and mRNA outcomes correlated with each other, indicating a similar transcription pattern in each type of sarcoid. The PF was significantly higher in the superficial layers of verrucous and fibroblastic sarcoids compared with occult and nodular types. No significant difference was observed for the PF in the deep layers and for p53 expression. These results clearly demonstrate the omnipresence and active transcription of BPV in equine sarcoids. However, the hypothesis that the clinical behaviour of an equine sarcoid can be explained on the basis of differences in BPV activity could not be demonstrated. INTRODUCTIONEquine sarcoid is the most common skin tumour in horses. The clinical aspect can vary remarkably, ranging from small, stable patches to aggressively growing tumours up to more than 10 cm in diameter. A sarcoid can appear as a single tumour, but horses often show multiple lesions. Although equine sarcoids do not metastasize, they recur frequently if not treated properly. Different clinical types have been described (Pascoe & Knottenbelt, 1999). The fibroblastic type, with a typically ulcerated epidermis, usually presents an aggressive clinical behaviour (Fig. 1a). Occult types are flat, alopecic patches, sometimes with hyperkeratosis or small nodules on their surface (Fig. 1b). These tumours will often not evolve, even over several years. Nodular sarcoids are round masses with an intact epithelium (Fig. 1c). The overlying skin can be loose from the stromal tissue or (partially) attached to the fibroblastic portion of the tumour. Verrucous sarcoids have a typically warty appearance (Fig. 1d). Nodular and verrucous sarcoids display a clinical behaviour in between the fibroblastic and the occult sarcoid, mostly with moderate growth. Mixed sarcoids, composed of two or more of the described types, are also commonly observed. Occult sarcoids, and even nodular and verrucous sarcoids, can remain stable for many years and then suddenly, without any apparent reason, change dramatica...

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RSV is an important cause of lower respiratory tract infections in children, the elderly and in those with underlying medical conditions. Although the high disease burden indicates an urgent need for a vaccine against RSV, no licensed RSV vaccine is currently available. We developed an RSV vaccine candidate based on the low-seroprevalent human adenovirus serotypes 26 and 35 (Ad26 and Ad35) encoding the RSV fusion (F) gene. Single immunization of mice with either one of these vectors induced high titers of RSV neutralizing antibodies and high levels of F specific interferon-gamma-producing T cells. A Th1-type immune response was indicated by a high IgG2a/IgG1 ratio of RSV-specific antibodies, strong induction of RSV-specific interferon-gamma and tumor necrosis factor-alpha cytokine producing CD8 Tcells, and low RSV-specific CD4 T-cell induction. Both humoral and cellular responses were increased upon a boost with RSV-F expressing heterologous adenovirus vector (Ad35 boost after Ad26 prime or vice versa). Both single immunization and prime-boost immunization of cotton rats induced high and long-lasting RSV neutralizing antibody titers and protective immunity against lung and nasal RSV A2 virus load up to at least 30 weeks after immunization. Cotton rats were also completely protected against challenge with a RSV B strain (B15/97) after heterologous prime-boost immunization. Lungs from vaccinated animals showed minimal damage or inflammatory infiltrates post-challenge, in contrast to animals vaccinated with formalin-inactivated virus. Our results suggest that recombinant human adenoviral Ad26 and Ad35 vectors encoding the RSV F gene have the potential to provide broad and durable protection against RSV in humans, and appear safe to be investigated in infants.

Background: Real-time quantitative PCR can be a very powerful and accurate technique to examine gene transcription patterns in different biological conditions. One of the critical steps in comparing transcription profiles is accurate normalisation. In most of the studies published on realtime PCR in horses, normalisation occurred against only one reference gene, usually GAPDH or ACTB, without validation of its expression stability. This might result in unreliable conclusions, because it has been demonstrated that the expression levels of so called "housekeeping genes" may vary considerably in different tissues, cell types or disease stages, particularly in clinical samples associated with malignant disease. The goal of this study was to establish a reliable set of reference genes for studies concerning normal equine skin and equine sarcoids, which are the most common skin tumour in horses.

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