Chapter 5. Picornaviruses - Part I Infection with Poliovirus may produce a sub-clinical illness, a mild illness or severe illness. Compare and contrast the three forms of infection in the table below. Virus is replicating in patient Abortive Non-paralytic Paralytic Post- poliomyelitis Virus establishes a latent infection Reactivation of virus occurs Antibodies may be present No symptoms are present Symptoms can be mistaken for other illness like "flu" Motor neurons are damaged Patient has complete recovery Vaccine induces production of antibodies to repair damage
Vaccines stimulate the immune system by exposing it to a "non-pathogenic" form of the virus. Ideally, the patient does not suffer the consequence of illness after being vaccinated. Fill in the following table that compares the different basic vaccine forms, and the immunity that is induced in the host. Attenuated Inactivated Subunit Contains intact virus particles Contains purified proteins Can replicate in host Induces Ab- mediated immunity Induces cell- mediated immunity What is the difference between an active virus and an attenuated virus? Can an attenuated virus ever cause disease?
Two types of vaccines are available to provide immunity against poliovirus. Both vaccines have advantages and disadvantages. In North America, the IPV is used initially, and OPV may be administered if the person is to travel to areas where poliovirus in present in the environment. Virus replicates in host IPV OPV Virus can be shed from the vaccinated host and spread to others Vaccine induces Ab-mediated immunity Vaccine induces Ab in the blood Vaccine induces Ab in the gut secretions Vaccine induces cell-mediated immunity Vaccine in injected Vaccine is ingested as a syrup or on sugar cube Virus in vaccine may revert to virulence and cause disease Vaccine is safe to administer to people with compromised immune systems Vaccine induces antibodies to VP1, VP2 and VP3 proteins of poliovirus capsid