Host immune responses
Within the same species and even within the same breed, the response of a host animal to PPRV depends on its immune status and age. An immunosuppressed animal is susceptible to the virus regardless of its age.
In young animals
In enzootic areas, offspring of seropositive females are immunized up to the age of 3-4 months by the maternal antibodies contained in colostrum. Beyond that point, the maternal protection diminishes but the animal's own immune defences are not yet fully established. Young animals below the age of one year consequently are the most severely affected by the disease.
In adult animals
Adults show cell-mediated and humoral immune responses to 3 viral proteins, N, F, and H, but of these, only the 2 surface proteins, F and H, are involved in the protective immunity.
Over the course of the infection, hemagglutinin H is the preferred target of the neutralizing antibodies behind the humoral defence response.
The F fusion protein engenders cellular immunity involving the T lymphocytes (lysis of infected cells).
The N nucleoprotein, a major antigen of the virus, is the most immunogenic but the antibodies produced by the infected animal are not neutralizing and provide no protection. The nucleoprotein nonetheless intervenes in the immune process by inducing cell death in lymphocytes.
Note :
The serological tests used to diagnose PPR rely on the detection of nucleoprotein-specific or hemagglutinin-specific antibodies in the animal's serum.
