Cell free enveloped virions enter susceptible cells by convention absorption and penetration. Cell to cell transfer of infection via formation of intracellular bridges is the principle mode of virus spread. There are three types of virus cell interaction. Productive Infections Productive infections are those in which the replication of viral DNA occurs, antigens are produced and virus particles are synthesized. There may be more than 1200 particles produced per infected cell.
Productive infections are cytolytic, form intranuclear inclusion bodies.
Two types of Productive infection exist. Fully productive infections result in large numbers of fully infectious enveloped virions. Productive restrictive infections produce non-infective virions due to a lack of envelope. Latent Infections Latent infections are non productive and can only be detected via DNA hybridization techniques or by activation of the viral genome. In vitro cultivation of latently infected cells results in a release from the latency.