Staphylococcus aureus is the leading cause of clinical mastitis and is associated with persistent subclinical infections in ewes, significantly compromising the quality and quantity of milk productions. To date, vaccines intended for use in sheep have been mainly focused on biofilm production traits, but many S. aureus pathogenic isolates do not produce biofilm, including those circulating in Sardinia, one of the leading sheep milk producers in Europe. The aim of this work was to identify suitable immunodominant, alternative candidates to biofilm components for vaccine and diagnostic development. An immunoproteomics study was carried out by testing sera from naturally infected sheep with a prevalent S. aureus lineage against cellular and secreted antigens, followed by tandem mass spectrometry identification of the most prominent immunogens. Four cellular and three secreted S. aureus antigens elicited a strong humoral host immune response. The four cellular antigens were the housekeeping proteins pyruvate kinase, elongation Factor Tu, dihydrolipoyl dehydrogenase, and alpha-keto acid dehydrogenase. The three secreted antigens were the bifunctional autolysin (Atl) and the two components of the Panton-Valentine leukocidin, lukF-PV/lukM, demonstrating the carriage of prophage phiPV83 in a sheep isolate and the strong response of the sheep host against them. In consideration of the key role played by these secreted proteins in S. aureus replication and immune evasion, these antigens may represent suitable candidates for developing vaccines eliciting a more successful immunological protection in areas where non-biofilm forming Staphylococcus spp. are the most widespread intramammary pathogens.

金黄色葡萄球菌是临床乳腺炎的主要原因，并且与母羊的持续性亚临床感染有关，大大损害了牛奶生产的质量和数量。迄今为止，用于绵羊的疫苗主要集中在生物膜的生产特性上，但是许多金黄色葡萄球菌的致病性分离株并未产生生物膜，包括在撒丁岛（欧洲主要的羊奶生产商之一）流通的那些。这项工作的目的是为疫苗和诊断开发确定生物膜成分的合适免疫优势替代候选物。免疫蛋白质组学研究是通过测试自然流行的金黄色葡萄球菌感染绵羊的血清来进行的针对细胞和分泌的抗原的谱系，然后通过串联质谱鉴定最突出的免疫原。四个细胞和三个分泌的金黄色葡萄球菌抗原引起强烈的体液宿主免疫反应。四种细胞抗原是管家蛋白丙酮酸激酶，延伸因子Tu，二氢脂酰脱氢酶和α-酮酸脱氢酶。三种分泌的抗原是双功能自溶素（Atl）和Panton-Valentine白细胞抑制素的两个成分lukF-PV / lukM，这表明在绵羊分离物中携带噬菌体phiPV83，并且绵羊宿主对它们的强烈反应。考虑到这些分泌蛋白在金黄色葡萄球菌中的关键作用复制和免疫逃避，这些抗原可能代表开发疫苗的合适候选物，从而在非生物膜形成葡萄球菌属物种的地区引发更成功的免疫学保护。是最广泛的乳房内病原体。