Abstract
Vaccines against S. aureus bovine mastitis are scarce and show limited protection only. All currently available vaccines are applied via the parenteral (usually intramuscular) route. It is unknown, however, whether this route is the most suitable to specifically increase intramammary immunity to combat S. aureus at the site of infection. Hence, in the present study, immunization via mucosal (intranasal; IN), intramuscular (triangle of the neck; IM), intramammary (IMM) and subcutaneous (suspensory ligament; SC) routes were analyzed for their effects on the quantity of the antibody responses in serum and milk as well as the neutralizing capacity of the antibodies within serum. The experimental vaccine comprised the recombinant S. aureus immune evasion proteins extracellular fibrinogen-binding protein (Efb) and the leukotoxin subunit LukM in an oil-in-water adjuvant combined with a hydrogel and alginate. The highest titer increases for both Efb and LukM specific IgG1 and IgG2 antibody levels in serum and milk were observed following SC/SC immunizations. Furthermore, the harmful effects of Efb and leukotoxin LukMF’ on host-defense were neutralized by serum antibodies in a route-dependent manner. SC/SC immunization resulted in a significant increase in the neutralizing capacity of serum antibodies towards Efb and LukMF’, shown by increased phagocytosis of S. aureus and increased viability of bovine leukocytes. Therefore, a SC immunization route should be considered when aiming to optimize humoral immunity against S. aureus mastitis in cattle.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-015-0243-7) contains supplementary material, which is available to authorized users.
Highlights
Infections with Staphylococci are common among humans and animals [1,2,3]
The aim of this study was to assess whether the route of immunization impacts the quantity of the antibody response as well as the neutralizing capacity of these antibodies, with an emphasis on intramammary immunity to S. aureus
Antibodies directed against extracellular fibrinogen-binding protein (Efb) and LukM could be detected in all cows prior to immunization
Summary
Infections with Staphylococci are common among humans and animals [1,2,3]. In cattle subclinical intramammary infections with S. aureus are common. Infections may lead to severe mastitis and/or chronic persistent infection with detrimental effects for the cows’ well-being, lifespan and milk production [4,5]. The current treatment of S. aureus infections with antibiotics often fails to completely clear the infection, due to specific cow or pathogen related risk factors [6]. Ineffective treatment may result in increased antibiotic resistance in S. aureus. The availability of an effective vaccine would be of great value [7]. Despite the numerous attempts to develop a Boerhout et al Veterinary Research (2015) 46:115
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