The mycotoxin deoxynivalenol (DON) can deteriorate vaccination efficacy against porcine reproductive and respiratory syndrome virus (PRRSV) at subtoxic levels

Abstract

Background Feedgrain contamination with mycotoxins, including deoxynivalenol (DON, “vomitoxin”) is relatively frequently encountered. Pigs are particularly sensitive to the toxicity of DON. To assess the interplay between DON and porcine reproductive and respiratory syndrome virus (PRRSV), we performed an experimental DON exposure–PRRSV vaccination–challenge infection trial. Three-week-old piglets were divided into four groups. Groups I, II and III (10 animals/group) were vaccinated with a PRRSV modified live vaccine and 2 weeks later challenged with a heterologous field strain. While group I was not supplemented with DON, animals in groups II and III received DON for 4 weeks prior to challenge infection at levels that can be encountered in pig feed, employing a low-dose or high-dose regime (group II: 40 µg DON/kg body weight per day; group III: 80 µg DON/kg body weight per day, corresponding to approx. 1 or 2 mg DON/kg feed, respectively). Eight animals (group IV; unvaccinated, not DON exposed) served as control animals for the challenge infection. Results We assessed clinical signs, virus load in serum and various organs as well as antibody titres in the animals. All vaccinated animals mounted an efficient PRRSV-specific antibody response within 2 weeks, except for 20% of the animals receiving the higher DON dose. Upon virus challenge, the vaccinated animals in group I were protected from clinical signs. Vaccinated DON-exposed animals in group II and III were protected from clinical signs to a lesser extent. Clinical signs in group III receiving the higher dose of DON were as severe as in the (unvaccinated, not DON exposed) control group IV. The animals of group III also displayed lower antibody titres compared with the animals in group I and II. Conclusions The experimental vaccination/challenge study therefore revealed that exposure of pigs to DON for a period of 4 weeks deteriorates the efficacy of vaccination against clinical signs of PRRS.

Influence of deoxynivalenol-contaminated feed on the immune response of pigs after PRRSV vaccination and infection

“…Hence, one common finding of the three studies addressing PRRSV-specific antibodies following vaccination (Sarvard et al 2015 ; Rückner et al 2022 ; this study) is a reduction in antibody S/P ratios at DON concentrations of 2 ppm or higher. The time point of this effect post-vaccination seems to vary (Sarvard et al 2015 and Rückner et al 2022 : day 13/14 onwards, our study: day 28) but may also be influenced by the type of PRRSV vaccine. Sarvard et al ( 2015 ) and Rückner et al ( 2022 ) used a PRRSV-2 MLV, whereas in our study a PRRSV-1 MLV was used.…”

“…The time point of this effect post-vaccination seems to vary (Sarvard et al 2015 and Rückner et al 2022 : day 13/14 onwards, our study: day 28) but may also be influenced by the type of PRRSV vaccine. Sarvard et al ( 2015 ) and Rückner et al ( 2022 ) used a PRRSV-2 MLV, whereas in our study a PRRSV-1 MLV was used. Following challenge infection, in our study and in Rückner et al ( 2022 ) reduced antibody S/P ratios persisted 7–14 days post-challenge infection onwards with DON doses of 2.81 ppm or 2 mg/kg, respectively, in comparison to pigs on DON free diets.…”

“…A more recent study by Rückner et al ( 2022 ) investigated the effect of 1 and 2 mg/kg DON in feed on PRRSV vaccination and challenge infection in the same animals. Different to our study, a PRRSV-2 MLV vaccine was used.…”

“…So far, few in vitro and in vivo studies investigated the effects of DON on vaccine efficacy, comprising experimental vaccines against ovalbumin (OVA) (Lessard et al 2015 ; Pinton et al 2008 ) and tetanus toxoid (Overnes et al 1997 ), against PRRSV in pigs (Rückner et al 2022 ; Savard et al 2015 ) and porcine parvovirus in mice (Choi et al 2013 ). It has been noted that DON can cause either immunostimulatory or immunosuppressive effects (Payros et al 2016 ).…”

Protective and detoxifying effects conferred by selenium against mycotoxins and livestock viruses: A review

“…Similarly, when vaccinated mice were exposed to 2.0 mg/L of DON through drinking water, the toxin disrupted their immune response by regulating the secretion of chemokines and cytokines which form part of their defensive mechanism against porcine parvovirus ( 119 ). An experimental study further showed that, in pigs, a 4-week exposure to DON reduced the efficiency of vaccines against the clinical signs of PRRSV ( 120 ). Antibody titers against porcine circovirus in the serum were also shown to decrease by 33–40% at day 28 after including 1.0 and 3.0 mg/kg of DON in diets ( 121 ).…”