Vaccinated groups were lacking an IgM response and developed a broad serum anti-gC IgG response with an IgG1/3/4/7/5low serum isotype profile after challenge infection, while the non-vaccinated weanlings responded with an initial weak IgM increase followed by a narrow IgG isotype response with an IgG1/3/4low/6low/7low profile and a delayed onset of all these IgG antibodies. The gene discussed is CD40LG; the disease is infection.