Serum Antibody Activity against Poly- N -Acetyl Glucosamine (PNAG), but Not PNAG Vaccination Status, Is Associated with Protecting Newborn Foals against Intrabronchial Infection with Rhodococcus equi

Abstract

Pneumonia caused by R. equi is an important cause of disease and death in foals worldwide for which a licensed vaccine is lacking. Foals are exposed to R. equi in their environment from birth, and they appear to be infected soon after parturition at an age when innate and adaptive immune responses are diminished.

Rhodococcus equifoal pneumonia: Update on epidemiology, immunity, treatment and prevention

“…67 Vaccination per se failed to protect foals, but serum activity against PNAG was significantly associated with protection. 67 These data indicate that further work to optimise the formulation (including the adjuvant and antigen-dose) and schedule/ timing of vaccination against PNAG are needed. Thus, the search for an effective vaccine to protect foals against R. equi continues.…”

“…162 Moreover, transfusion of foals with PNAG hyperimmune plasma protected foals against intrabronchial infection with R. equi, whereas transfusion with standard plasma did not. 67 Some veterinarians recommend transfusing foals within 1 or 2 days after birth to provide protection at the age when they are most susceptible to R. equi, 57 and some veterinarians recommend transfusing foals once shortly after birth and again around 3 to 4 weeks of age, when maternal antibodies begin to wane and corresponding to the earliest age of onset of disease for most foals.…”

“…This susceptibility at a young age is likely related to their immature immune system, similar to neonates of other species 58 . During the first month after birth, several age‐related changes have been described in both the innate and adaptive immune responses of foals that likely influence the outcome of infection 57–68 . Importantly, the period during which foals are highly susceptible overlaps with the period when they lack mature immune responses.…”

“…Moreover, transfusion of foals within 36 hours of birth with plasma from donors hyperimmunised against PNAG protected foals against intrabronchial infection at age 28 days 84 . Because foals are exposed to R. equi from birth 1,2,22–25,55,56 and because epidemiological evidence suggests foals are infected soon after birth 56 when they are more susceptible to infection, 57 the ability of maternal vaccination against PNAG to infect foals against intrabronchial infection was investigated 67 . Vaccination per se failed to protect foals, but serum activity against PNAG was significantly associated with protection 67 .…”

“…Because foals are exposed to R. equi from birth 1,2,22–25,55,56 and because epidemiological evidence suggests foals are infected soon after birth 56 when they are more susceptible to infection, 57 the ability of maternal vaccination against PNAG to infect foals against intrabronchial infection was investigated 67 . Vaccination per se failed to protect foals, but serum activity against PNAG was significantly associated with protection 67 . These data indicate that further work to optimise the formulation (including the adjuvant and antigen‐dose) and schedule/timing of vaccination against PNAG are needed.…”