The use of stochastic model in this study of HIV infection, transmission the spread of AIDS is quite common .The time to seroconversion from the point of infection depends upon what is known as antigenic diversity which act against the immune ability of an individuals. If the antigenic diversity causes a particular level which is known as the antigenic diversity threshold, the immune system collapses and seroconversion takes place at once. To propose a stochastic model to study the damage process acting on the immune system is non- linear. The mean time to seroconversion and its variance are derived and the numerical illustrations are provided.