Infection and Immunity. What does a pathogen have to do?. Infect (infest) a host Reproduce (replicate) itself Ensure that its progeny are transmitted to another host. Mechanisms of Transmission.
Virus Primary ReplicationSecondary Replication
Intestinal epithelium Lymphoid
Oropharynx or Lymphoid cells,
Lymphoid tissues, C.N.S.
Oropharynx or G.U.tract
Lymphoid cells, C.N.S.
Slow virus infections
The Virus persists in an occult, or cryptic, from most of the time. There will be intermittent flare-ups of clinical disease , Infectious virus can be recovered during flare-ups . Latent virus infections typically persist for the entire life of the host
Type Virus production Fate of cell
Abortive - No effect
Cytolytic + Death
Productive + Senescence
Latent - No effect
DNA viruses - Immortalization
RNA viruses + Immortalization
Long term persistence of virus results from two main mechanisms:
complement, interferon, TNF etc.
T cells; other effectors cells
Intact skin / Mucus membrane
Temperature /Acidity of gastric juices
NK cells are Activated by IFN-alpha/beta
NK cells are Activated by IFN-alpha and IL-2 and
NK cells target and kill virus infected cells