Polioviruses

Introduction

Poliomyelitis is first known to have occurred nearly 6000 years ago, caused by poliovirus. Poliovirus is highly infectious and damages the central nervous system (CNS). Poliovirus most commonly affects children under the age of 5. Universal vaccination in early childhood is the best way to prevent and eradicate poliomyelitis. Today, poliomyelitis is very rare in all developed and many developing countries, owing to the success of polio vaccination campaigns.

Poliovirus Genome

Poliovirus belongs to the genus Enterovirus of the Picornaviridae family. Poliovirus consists of a single-stranded RNA genome (7.5kb) of positive polarity surrounded by a non enveloped icosahedral protein capsid. The capsid of the mature virion is approximately 30 nm in diameter and consists of 60 copies of each of four coat proteins, VP1, VP2, VP3, and myrVP4. The shell is formed by VP1, VP2, and VP3, while VP4 lies on its inner surface. Polioviruses occur as serotypes 1, 2 and 3, and immunity to one type is believed not to protect against the other two. Poliovirus type 1 has the highest rate of paralysis and commonly causes epidemics.

Fig.1 Poliovirus genome organization and morphogenesis. (Adeyemi, 2017)

Pathogenesis

Infection with poliovirus begins when the virus is ingested and multiplies in the oropharyngeal and intestinal mucosa, where it causes few if any symptoms. Poliovirus replication begins with the attachment of virus particles to a cell surface receptor, CD155. Intestinal M cells in humans are the site of poliovirus penetration of the intestinal epithelial barrier, spreading to the blood through the lymph nodes, leading to viremia. It is estimated that poliovirus entry into the CNS in two routes which are not mutually exclusive: the virus enters the CNS from the blood, or enters a peripheral nerve and is carried to the CNS by axonal transport. In the CNS, the main target cell of poliovirus is the motor neuron of the spinal cord and the brain stem. The destruction of motor neurons, a consequence of poliovirus replication, results in paralysis.

Fig.2 Dissemination pathways of poliovirus in humans. (Ohka, 2001)

Epidemiology

Humans are the only natural host of poliovirus, and poliovirus infection results in poliomyelitis in only 1 to 2% of cases. Poliovirus is usually spread from person to person via the fecal-oral route or oral-oral route. 350,000 annual polio cases occurred worldwide in 1988, the beginning of the vaccine campaign. Between April 2005 and April 2006 it was reported 1815 cases worldwide. In 2015, 72 cases of wild poliovirus were reported in only 2 countries: 54 from Pakistan and 20 from Afghanistan. By 2019, only 125 cases caused by wild poliovirus were reported globally. Mass immunization campaigns have reduced polio cases by > 99%. Vaccine-associated paralytic poliomyelitis occurs in an estimated 1 in 2.7 million children receiving their first dose of oral polio vaccine.

Symptoms

Severity of poliomyelitis symptoms varies. It may range from being asymptomatic to experiencing a paralytic attack. Non-paralytic poliomyelitis symptoms go away without any type of intervention, they may include:

• Sore throat
• Fever
• Fatigue
• Stomach discomfort
• Nausea
• Headache
• Stiffness in the neck

Paralytic poliomyelitis is classified into 3 types: spinal poliomyelitis, bulbar poliomyelitis and bulbospinal poliomyelitis. Paralytic poliomyelitis is characterized by severe muscle pain and spasms, followed by weakness. In a small proportion of cases, the disease causes paralysis, which is often permanent.

Prevention and Treatment

There's no cure for poliomyelitis, and the focus of treatment is on increasing comfort, speeding recovery and preventing complications. But a vaccine allows the body to fight off the virus. Permanent eradication of poliovirus through vaccination is theoretically possible. There are two different types of vaccinations that can prevent poliomyelitis. Inactivated poliomyelitis vaccine (IPV) is the only polio vaccine that has been given in the United States since 2000. Oral poliomyelitis vaccine (OPV) is used in other countries. OPV is known to be associated with a rare complication known as vaccine-associated paralytic poliomyelitis and is no longer used in the US.

Anti-Poliovirus Products and Services

The studies on poliomyelitis and other paralytic diseases possibly also caused by polioviruses are still very important. Anti-Poliovirus antibodies can be used in the study of poliomyelitis diseases. Creative Biolabs provides a large number of anti-Poliovirus antibodies for hot targets: VP1 and VP3. Except for primary antibodies, we also provide secondary antibodies, isotype controls, pseudovirus and pseudohost. In addition, our services include ViroAntibody neutralization, discovery, engineering, customized. If you are interested in any details in ViroAntibody products and services, please feel free to contact us for further information.

References

1. Adeyemi, O.O.; et al. Increasing Type 1 Poliovirus Capsid Stability by Thermal Selection. J Virol. 2017, 91(4).
2. Ohka, S.; Nomoto, A. Recent insights into poliovirus pathogenesis. Trends in Microbiology. 2001, 9(10): 501-506.

All products and services are intended for Research Use Only, and NOT to be used in diagnostic or therapeutic procedures.