The Effectiveness of Anti-R. equiHyperimmune Plasma againstR. equiChallenge in Thoroughbred Arabian Foals of Mares Vaccinated withR. equiVaccine

Abstract

This study aimed to determine the effectiveness of a pregnant mare immunization of a Rhodococcus equi (R. equi) vaccine candidate containing a water-based nanoparticle mineral oil adjuvanted (Montanide IMS 3012) inactive bacterin and virulence-associated protein A (VapA), as well as the administration of anti-R. equi hyperimmune (HI) plasma against R. equi challenge in the mares' foals. The efficacy of passive immunizations (colostral passive immunity by mare vaccination and artificial passive immunity by HI plasma administration) was evaluated based on clinical signs, complete blood count, blood gas analysis, serological response (ELISA), interleukin-4 (IL-4) and interferon gamma (IFN-γ), total cell count of the bronchoalveolar lavage fluids (BALF) samples, reisolation rate of R. equi from BALF samples (CFU/mL), lung samples (CFU/gr), and lesion scores of the organs and tissue according to pathological findings after necropsy in the foals. The vaccination of pregnant mares and HI plasma administration in the foals reduced the severity of R. equi pneumonia and lesion scores of the organs and tissue by 3.54-fold compared to the control foals. This study thus indicates that immunization of pregnant mares with R. equi vaccine candidate and administration of HI plasma in mares' foals effectively protect foals against R. equi challenge.

Antibody to Poly-N-acetyl glucosamine provides protection against intracellular pathogens: Mechanism of action and validation in horse foals challenged with Rhodococcus equi

“…The disease is of considerable importance to the equine industry [ 5 , 7 ], and while some reports indicate vaccination and/or passive transfer of hyperimmune plasma using bactrin-based or virulence associated protein A vaccines can reduce the severity of R . equi pneumonia [ 8 , 9 ], it is generally felt that most attempts to date to create an effective R . equi vaccine have been unsuccessful [ 10 , 11 ].…”

Current Trends in Understanding and Managing Equine Rhodococcosis

“…Some of the latest papers also indicated that the effectiveness of this strategy might be dose-dependent, because 2 L of HIP was more beneficial than administration of 1 L or less of the same product [ 57 ]. What is more, when two methods: vaccination of mares and administration of HIP were used, clinical sings in the foals occurred later, were less severe and mortality rate was lower [ 65 ]. As it has been previously confirmed, clinical signs of pneumonia in foals can be associated with significantly higher fecal shedding of Rhodococcus equi .…”

“…Vaccinations against R. equi are wildly awaited and often considered a form of prophylaxis. Unfortunately, despite many trials none of them was claimed effective enough to become commercially available [ 65 ]. Up to now there are no vaccinations available neither for mares nor for the foals [ 62 ].…”

Current Understanding of Rhodococcus Equi infection and its Zoonotic Implications

“…Administration of hyperimmune plasma to foals during the first few days and then again at 3 weeks of age is reported to reduce the incidence and severity of the disease. A recent study has shown that the immunization of pregnant mares with R. equi vaccine candidate having aqueous medium based nanoparticle mineral oil adjuvinated inactive bacterin and VapA along with administration of anti-R. equi hyperimmune plasma in foals may be effective in protection of foals from R. equi infection (Erganis et al 2014). Bordin et al (2014) have studied the immunogenicity of an electron beam inactivated R. equi vaccine in foals.…”