In fact, we were able to observe increased bacterial survival and reduced strain (Figure?7)

In fact, we were able to observe increased bacterial survival and reduced strain (Figure?7). placebo animals demonstrated clinical signs of severe disease. In both groups two piglets had to be euthanized for animal welfare reasons because of signs of polyarthritis. One vaccinated animal showed additional signs of central nervous system Nesbuvir dysfunction (opisthotonus, generalized tremor, ataxia) and had to be euthanized as well. Surviving piglets were sacrificed fourteen days post-infection. Necropsies and histopathological screenings of the indicated tissues were conducted with all 16 piglets as described previously [10]. 13567_2021_981_MOESM6_ESM.pdf (116K) GUID:?91DF8EBF-9F6C-44FC-B116-24B4B2B44F60 Data Availability StatementThe datasets analyzed during the current study are available from the corresponding author on reasonable request. Abstract A vaccine protecting against different serotypes is highly needed in porcine practice to improve animal welfare and reduce the use of antibiotics. We hypothesized that immunogens prominently recognized by convalescence sera but significantly less so by sera of susceptible piglets are putative protective antigens. Accordingly, we investigated immunogenicity and protective efficacy of a multicomponent vaccine including six main conserved immunogens, namely SSU0934, SSU1869, SSU0757, SSU1950, SSU1664 and SSU0187. Flow cytometry confirmed surface expression of all six immunogens in serotypes 2, 9 and 14. Although prime-booster vaccination after weaning resulted in significantly higher specific IgG levels against all six immunogens compared to the placebo-treated group, no significant differences between bacterial survival in blood from either vaccinated or control animals were recorded for serotype 2, 9 and Nesbuvir 14 strains. Furthermore, vaccinated piglets were not protected against morbidity elicited through intranasal challenge with serotype 14. As ~50% of animals in both groups did not develop disease, we investigated putative other correlates of protection. Induction of reactive oxygen species (ROS) in blood granulocytes was not associated with vaccination but correlated with protection as all piglets with? 5% ROS survived the challenge. Based on these findings we discuss that the main immunogens of might actually not be a priori good candidates for protective antigens. On the contrary, expression of immunogens that evoke antibodies that do not mediate killing of this pathogen might constitute an evolutionary advantage conserved in many different strains. Supplementary Information The online version contains supplementary material available at 10.1186/s13567-021-00981-3. is a very successful colonizer of mucosal surfaces in pigs. However, it is also a major porcine pathogen causing severe pathologies such as meningitis, polyarthritis, septicemia and endocarditis. Currently, 29 serotypes (and are associated with diseases and main herd problems in different countries, whereas other serotypes contribute only marginally to morbidity [2]. Worldwide, is most frequently isolated from clinical cases in pigs and humans [2]. However, has become most prevalent among invasive isolates in some European countries with a large pig industry Nesbuvir such as The Netherlands and Spain [2, 3]. In South America ranks third among invasive strains [4, 5]. Furthermore, is also frequently found in the United Kingdom [3, 6] and contributes substantially to severe zoonotic cases in Asia [2]. As no licensed vaccine has convincingly reduced the burden of diseases in the field, different vaccination approaches are currently under investigation. This includes conjugated capsule polysaccharides [7], live attenuated serovar Choleraesuis vectors delivering conserved surface proteins [8, 9] and different recombinant antigens [10, 11]. A multicomponent vaccine including five recombinant antigens, which were identified in a screen for fitness genes important for colonization of the pig nasal epithelium, Nesbuvir elicits partial protection against a homologous challenge [12]. Various groups have been using immunoproteomics to identify conserved immunogens, which are discussed as promising protective antigens. Main immunogens of virulent strains include lipoproteins, muramidase-released protein, surface antigen one and suilysin [13]. However, data demonstrating protective efficacy of these immunogens is very limited or even contradictory. In this study we investigated the protective efficacy of a multicomponent vaccine against in the natural host. The multicomponent vaccine included immunogens expressed by at least three different important (2, 14, 9). Sera drawn from convalescent piglets contained significantly higher levels of immunogen-specific IgG antibodies than sera drawn from susceptible piglets. Although significant differences in specific antibody levels were elicited through vaccination, protection was not observed. The heterogeneity in the clinical outcome between the different animals was used to investigate a new putative correlate of protection: the induction of reactive oxygen species (ROS, also described as oxidative burst) in blood granulocytes. Materials and methods Bacterial IkB alpha antibody strains and growth conditions strain 10 is an and sequence type 1 was originally isolated from the brain of a pig with meningitis. Sequencing of the strain. The latter was kindly conducted by Astrid de Greef (Wageningen Bioveterinary Research, Lelystad, The Netherlands). Strain 7119-1 (strains.