Abstract: An isolated antigen against a Mycoplasma, prepared by a method including providing a sample of a Mycoplasma and an antibody probe, probing the Mycoplasma sample with the antibody probe to detect at least one antigen, and isolating the antigen detected. The antibody probe includes at least one antibody against the Mycoplasma that is produced by a method including (a) providing a biological sample taken a short time after an immune animal has been challenged with a Mycoplasma or Mycoplasma extract taken from the infection site or an area of a lesion or an area close to the infection site or lesion; (b) isolating cells from the biological sample; (c) culturing the cells in vitro in a suitable culture medium; and (d) harvesting antibodies produced from the cell.

Abstract: The present invention relates to a putative protective antigen against a Mycoplasma, prepared by a method including a sample of a Mycoplasma; an antibody probe including at least one antibody against a Mycoplasma produced by a method including: providing a biological sample taken a short time after an immune animal has been challenged with a Mycoplasma or Mycoplasma extract taken from the infection site or an area of a lesion or an area close to the infection site or lesion; isolating cells from the biological sample; culturing cells in vitro in a suitable culture medium; and harvesting antibodies produced from said cells; probing the Mycoplasma sample with the antibody probe to detect at least one antigen; and isolating the antigen detected, also including diagnostic antigens, the preparation thereof, and their use in the formation of vaccine compositions, particularly vaccine compositions against Mycoplasma hyopneumoniae infections.