Comparative Virulence and Cytopathic Profiles of Sabin Poliovirus Vaccine Strains and Acute Flaccid Paralysis-Associated Isolates from Iraqi Children
Virulence and Cytopathic Effects of Sabin and AFP
DOI:
https://doi.org/10.65329/wjeb.v14.01.08Keywords:
Acute flaccid paralysis, Cytopathic effects, Oral polio vaccine, Poliovirus, Vaccine-derived poliovirus, Vaccine-associated paralytic poliomyelitis (VAPP).Abstract
The use of oral poliovirus vaccine (OPV), which consists of attenuated Sabin strains, is a key component to achieving worldwide poliovirus eradication. However, many people view vaccine-associated paralytic poliomyelitis (VAPP) and vaccine-derived polioviruses (VDPV) as significant problems, particularly in regions with low sanitation and vaccine coverage rates. This study describes a comparison of virulence and cytopathic effects of OPV and AFP-associated Sabin isolates obtained from Iraqi children. A total of 250 fecal samples obtained from suspected AFP cases and 50 from healthy controls were screened for the presence of poliovirus. Viral isolation was performed using RD and L20B cell lines (the viral cell type is not important) and serotyping was performed using neutralization testing. The cytopathic effects (CPE) and viral titer (TCID₅₀) values were compared to those of OPV and AFP-associated isolates. Poliovirus (Sabine, not wild type) was isolated from 35 of the 105 (33.33%) suspected AFP cases and 3 out of the 13 (23%) control subjects. Sabin type 3 predominated (51.42%), followed by mixed type 1+3 (28.57%) and type 1 (20%), with no type 2 isolates detected. Notably, AFP-associated isolates demonstrated significantly higher viral titers than the original vaccine strains, and distinctive cytopathic patterns characterized by rapid, complete monolayer destruction within 1-2 days, in contrast to the slower, focal degeneration observed with vaccine strains. The present study reported increased cytopathic characteristics in AFP-associated Sabin isolates compared with vaccine strains. These findings emphasize the importance of continuous virological surveillance and support the strategic transition toward inactivated poliovirus vaccine (IPV).
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