Passive transfer of maternal Mycoplasma hyopneumoniae-specific cellular immunity to piglets

Abstract

Immunity in the neonatal animal is primarily maternally derived, either by lymphocytes that pass into the newborn across the placenta or following colostrum ingestion. However, the effect of this passively transferred cellular maternal immunity on the newborn's immune repertoire is not clearly understood. Various studies have shown that colostral lymphocytes are activated and possess functional abilities; however, no studies have shown the transfer of colostral antigen-specific T-cell-specific responses in a newborn. In this study we examined the transfer of vaccine-induced Mycoplasma hyopneumoniae cellular immunity from immune dams to newborn piglets. Newborn piglets from vaccinated and nonvaccinated dams were assessed in two ways for cellular immune responses specific to M. hyopneumoniae: (i) delayed-type hypersensitivity (DTH) testing and (ii) in vitro lymphocyte proliferation, assayed on piglet blood lymphocytes and sow colostral lymphocytes. DTH responses to M. hyopneumoniae were detected only for offspring of vaccinated sows, whereas DTH responses to the nonspecific mitogen phytohemagglutinin were seen for all piglets. M. hyopneumoniae-specific proliferation was seen for colostral lymphocytes from vaccinated sows and for blood lymphocytes from neonatal piglets of vaccinated dams but not for blood lymphocytes from piglets of nonvaccinated sows. Functional antigen-specific T cells were transferred to offspring from vaccinated sows and participated in the neonatal immune response upon stimulation. These data have implications for defining disease intervention strategies.

FIG. 1.

DTH responses to Mycoplasma hyopneumoniae in young pigs. M. hyopneumoniae antigen, PHA, or saline was injected intradermally into the left inguinal area of 3- to 5-day-old pigs. Skin fold thickness and lesion size were measured 36 h later with calipers. (A) Mycoplasma-specific DTH responses in offspring of VS and NVS. (B) DTH responses in offspring of VS. (C) DTH responses in offspring of NVS. M. hyopneumoniae-specific DTH responses were evident only for offspring of VS. All animals responded to the nonspecific mitogen PHA and none responded to saline. * indicates significance at a P value of <0.05; ** indicates significance at a P value of <0.001. DxT, measurement value for orthogonal diameter by skin thickness.

FIG. 2.

Mycoplasma-specific lymphocyte proliferation. Lymphocytes were isolated from sow colostrum and from piglet blood before (PS) and 24 h after (AS) colostrum ingestion and stimulated with M. hyopneumoniae antigen. Average antigen-specific proliferation by lymphocytes isolated from PS and AS piglets and from sow colostrum. Variation is expressed as standard error; * indicates significance at a P value of <0.05.