How does the polio virus replicate?

The replication cycle of poliovirus is initiated by binding to the cell surface receptor CD155 (1). The virion forms a pore in the cell membrane through which viral RNA is released into the cytoplasm (2). Translation of the viral RNA occurs by an IRES-mediated mechanism (3).

Does polio go through the lytic cycle?

One such virus, poliovirus (PV), is an extremely lytic RNA virus that requires the expression of CD155, the poliovirus receptor (PVR), for infection.

Where does poliovirus replicate in the cell?

At the same time, cellular fractionation studies revealed that poliovirus RNAs are synthesized in replication complexes bound to distinct membranous structures in the cytoplasm of infected cells [9].

How is the polio vaccine attenuated?

OPV is an attenuated vaccine, produced by the passage of the virus through nonhuman cells at a subphysiological temperature, which produces spontaneous mutations in the viral genome. Oral polio vaccines were developed by several groups, one of which was led by Albert Sabin.

Where does polio genome replication occur?

Poliovirus is transmitted primarily by the fecal–oral route and replicates in the pharynx and lower intestinal tract (Table 235-1). Only small amounts of infectious virus are needed to cause infection. Virus is shed in the pharynx for 1 to 3 weeks and in the gut for 4 to 8 weeks after primary infection.

How long does polio virus live on surfaces?

Most viruses from the respiratory tract, such as corona, coxsackie, influenza, SARS or rhino virus, can persist on surfaces for a few days. Viruses from the gastrointestinal tract, such as astrovirus, HAV, polio- or rota virus, persist for approximately 2 months.

What is the pathogenesis of polio?

During intestinal replication, the virus invades local lymphoid tissue and may enter the bloodstream, and then infect cells of the central nervous system. Poliovirus-induced destruction of motor neurons of the anterior horn of the spinal cord and brain stem cells results in distinctive paralysis.

Is the polio virus DNA or RNA?

Poliovirus, the prototypical picornavirus and causative agent of poliomyelitis, is a nonenveloped virus with a single-stranded RNA genome of positive polarity. The virion consists of an icosahedral protein shell, composed of four capsid proteins (VP1, VP2, VP3, and VP4), which encapsidates the RNA genome (1).

Where does poliovirus multiply first?

The virus enters through the mouth and multiplies in the throat and gastrointestinal tract, then moves into the bloodstream and is carried to the central nervous system where it replicates and destroys the motor neuron cells.

Where is poliovirus found in nature?

No new cases of wild poliovirus have been recorded on the continent since 2016, but other types of the virus persist. Africa is free from wild poliovirus, the World Health Organization (WHO) announced on 25 August — leaving just two countries where the virus remains endemic, Afghanistan and Pakistan.

What vaccines are live attenuated?

Live-attenuated vaccines

• Measles, mumps, rubella (MMR combined vaccine)
• Rotavirus.
• Smallpox.
• Chickenpox.
• Yellow fever.

What is the key disadvantage of using the attenuated live vaccine for the eradication of polio?

Disadvantages. OPV is extremely safe and effective. However, in extremely rare cases (at a rate of approximately 2 to 4 events per 1 million births [1]) the live attenuated vaccine-virus in OPV can cause paralysis. In some cases, it is believed that this may be triggered by an immunodeficiency.