Enterotoxigenic Escherichia coli (ETEC) strains expressing F4 and F18 fimbriae are the most common causative agents of post-weaning diarrhoea (PWD) in pigs. The growing global restriction on the use ...of antibiotics in food animals has encouraged research into the development of nutritional and feeding strategies as well as vaccination against PWD. The aim of this study was to evaluate the efficacy of a live oral F4ac+ F18ac+ non-ETEC vaccine candidate (VAC) to stimulate gut and systemic cellular immunity in 4-week old pigs over 5 weeks following immunization. The onset and duration of protective immunity against on-farm occurring PWD, growth performance, diarrhoea scoring and mortality, as well as the phenotypic proportions of immune cells, were determined. Faecal and ileal samples were taken for determining the microbial composition or phenotyping of naïve/memory T cells. Also, the effect of prebiotic supplement mannan oligosaccharide (MOS) in the prevention of small intestinal colonization by ETEC, and its potential adjuvanticity in combination with the vaccine (VAC+MOS) were assessed. The pigs supplemented with MOS or that received VAC had significantly higher body weight (BW) (P<0.05) on Day 14, whereas the VAC+MOS treated pigs had significantly lower BW on Day 35. Treatment with VAC+MOS resulted in considerably reduced clinical PWD, in particular the incidence and severity of diarrhoea and mortality. The total bacterial load in the ileum was much lower in the pigs from all 3 principal groups (MOS, VAC, and VAC+MOS) than in the control (CON) group (19 x 107, 17 x 107 and 12 x 107 vs. 23 x 108 CFU/mL, respectively) on Day 35. The pigs from the principal groups had significantly higher proportions of tested immune cells (P<0.05) on Days 28 and 35. The localization and frequency of naive CD45RA+ and memory CD45RC+ T lymphocytes indicated their different distribution patterns within particular tissue structures, such as the villi, crypts, epithelium, lamina propria and areas (interfollicular follicular and Peyer’s patches) of ileal mucosa. This may indicate their different functions in intestinal immune responses to intraluminal microbes and their products, vaccinal immunogens and/or immunomodulators/adjuvants. To conclude, active mucosal immunity is needed to protect pigs against PWD. Hence, oral vaccination of pigs against both F4 and F18 ETEC, in combination with prebiotic supplementation represents a sustainable, practical and effective approach in PWD control.
Enterotoksigeni sojevi bakterije Escherichia coli (ETEC), koji proizvode F4 i F18 fimbrije, najuobičajeniji su
uzročnici dijareje nakon odbića (DNO) u prasadi. Rastuće globalno ograničavanje uporabe ...antibiotika u farmskih
životinja usmjeruje istraživanja prema razvijanju nutritivnih i prehrambenih strategija, kao i prema cijepljenju protiv
DNO-a. Cilj ovog istraživanja bio je vrednovanje učinkovitosti živog, oralnog F4ac+ F18ac+ ne-ETEC cjepiva-kandidata
(VAK) u poticanju crijevne i sistemske stanične imunosti u prasadi u dobi od 4 tjedna, tijekom 5 tjedana nakon
imunizacije. U pokusu su određivani početak i trajanje zaštitne imunosti od pojavnosti farmskog DNO-a, proizvodni
rezultati, ocjenjivanje učestalosti i jačine dijareje te mortalitet i fenotipski udjeli imunosnih stanica. Uzimani su uzorci
fecesa i ileuma za određivanje sastava mikrobiota ili za fenotipiziranje naivnih/memorijskih T-limfocita. Procijenjena
je i učinkovitost prebiotika manan-oligosaharida (MOS), kao dodatka hrani, koji bi mogao uspostaviti kompetitivnu
ekskluziju naseljavanja tankog crijeva sojevima ETEC, a mogao bi pokazati i adjuvantnost u testiranoj kombinaciji
(VAK + MOS). Prasad hranjena dodatkom MOS-a u hrani, ili koja je primila VAK, imala je znakovito povećanu (P
< 0,05) tjelesnu masu 14. dan pokusa, dok je prasad tretirana kombinacijom VAK-a i MOS-a imala znakovito nižu
tjelesnu masu 35. dan pokusa. Tretman kombinacijom VAK-a i MOS-a rezultirao je znatno blažom kliničkom slikom
DNO-a, napose u odnosu na pojavnost i jačinu dijareje te na mortalitet. Ukupno bakterijsko opterećenje u ileumu bilo
je mnogo niže u prasadi iz sve tri pokusne skupine (MOS, VAK i VAK + MOS) od onog u kontrolnoj (KON) skupini
(19 x 107, 17 x 107 i 12 x 107 prema 23 x 108 CFU/mL) 35. dan pokusa. Prasad iz pokusnih skupina imala je znakovito
veće udjele testiranih imunosnih stanica (P < 0,05) 28. i 35. dan pokusa. Lokalizacija i učestalost naivnih CD45RA+
te memorijskih CD45RC+ T-limfocita pokazuju njihove različite obrasce smještanja u posebne tkivne strukture, kao
što su crijevne resice, kripte, epitelij i lamina propria te područja u sluznici ileuma, što može specificirati njihove
različite funkcije u crijevnim imunosnim odgovorima na intraluminalne mikrobe i njihove proizvode, vakcinalne
imunogene i/ili imunomodulatore/adjuvanse. Zaključujemo da je radi zaštite prasadi od DNO-a nužno uspostaviti
aktivnu mukoznu imunost. Stoga je oralno cijepljenje prasadi protiv F4 i F18 ETEC-a održiv, praktičan i učinkovit
pristup u pronalaženju odgovarajućega bivalentnog, izrazito imunogenog i sigurnog cjepiva.
