Systemic and Local Antibody Responses after Experimental Infection withActinobacillus pleuropneumoniaein Piglets with Passive or Active Immunity

Abstract

The objectives of the present study was to describe different dynamics of humoral immune responses to experimental infection in piglets of different stages of infection and immunity. Two groups of piglets originating from non-immune (group 1) and immune (group 2) sows at the age of 3 weeks were subdivided as follows: a half of each group of piglets was exposed to a low-dose infection with Actinobacillus pleuropneumoniae (APP) strain 9. At the age of 8 weeks, all four groups of piglets were challenged with a high infection dose of APP of the same strain. Isotype characterization of the specific antibodies in sera and in bronchoalveolar lavage fluids (BALF) to a lipopolysaccharide was carried out, besides monitoring clinical signs and post-mortem examinations. A typical primary immune response was observed in specific antibody-free piglets infected with a challenge infection. Colostrum-derived immunoglobulin-G (IgG) antibodies persisted in sera and BALF of piglets up to the age of 8 weeks. However, they did not prevent induction of specific-primary antibody response, either in 8 or 4 weeks of age, when levels of specific colostrum-derived antibodies were still high. It was demonstrated by the increase of specific IgM antibodies in sera. The infection induced an increase in the levels of IgA antibodies in BALF regardless the severity of infection and presence of specific colostrum-derived antibodies. The specific antibodies of IgG isotype increased only in BALF from piglets without colostrum-derived antibodies.

Responses of pigs to a re‐challenge with Actinobacillus pleuropneumoniae after being treated with different antimicrobials following their initial exposure

“…Similar results have been observed by Smith and others (1991) and Wallgren and others (1999a,b). The results obtained agree with previous studies suggesting that antibody-mediated immunity may play a protective role (Bossé and others 1992, Krejci and others 2005). …”

Update onActinobacillus pleuropneumoniae-knowledge, gaps and challenges

“…Disease in suckling piglets is a rare event, but is especially prevented by proper levels of protective maternal antibodies, which can be induced either by infection or by vaccination (Krejci et al., ). The time until maternal antibodies in the suckling period decrease below detection limits is reported to range between 2 weeks after birth (Vigre, Ersbøll, & Sørensen, ) to the 12th week of age, depending on the level of antibodies in sows and the serological test used, leaving piglets highly susceptible to infection (Chiers et al., ; Cruijsen et al., ; Gardner, Bossé, Sheldrake, Rosendal, & Johnson, ).…”

Evaluation of diagnostic assays for the serological detection ofActinobacillus pleuropneumoniaeon samples of known or unknown exposure

“…30 Actinobacillus pleuropneumoniae immunoglobulin M (IgM) antibodies have been detected as early as 1 week after experimental infection. 25 Seroconversion and detectable levels of A. pleuropneumoniae IgG antibodies have been reported to appear between 1 to 3 weeks 7 or 2 to 4 weeks 25,29 after experimental infection. The levels of IgG antibody typically increase 2 weeks after A. pleuropneumoniae vaccination 21 but titers vary depending on the type of adjuvant utilized.…”