Application of Microneutralization Test for Detecting Humoral Immunity Against Poliovirus Types 1, 2 and 3 in Pregnant Women

Poliomyelitis is one of the most serious viral diseases caused by any of the polioviruses. The causal agents multiply at mucosal surfaces and accumulate in the draining lymph nodes where some strains may replicate. From there virus seeds peripheral sites, including peripheral nerves, and the viruses generated at the distant sites are the source of the detectable viraemia. Antibodies appear early and are protective even when given as passive immunoglobulin.Immunization against polio saves the lives of children. Countrywide vaccination program is done to produce satisfactory level of immunity among susceptible people, and to stop transmission of the wild poliviruses among children.One of the best available methods for assessing the level of antibodies, induced in people against poliviruses, is serum neutralization test (SNT).This study was designed to evaluate the level of polivirus neutralizing antibodies in the cord blood of pregnant women. Four hundred and twelve sera were collected aseptically and a microneutralization test, using control antisera against polivirus types 1, 2 and 3 was done to measure the antibody titer of each serum against all three types of the virus. Control antisera were prepared in rabbit, and viruses were multiplied in Hela and Vero cells. The data revealed that 6 (1.46%), 16 (3.9%), and 38 (9.2%) sera did not have detectable antibodies against the virus types 1, 2 and 3 respectively. It was also shown that out of 412 sera, 339 (82.3%), 333 (80.8%), and 283 (68.9%) samples contained antibody titers of equal or more than against virus types 1, 2 and 3 respectively. These findings suggest that national immunization days should be continued to maintain the level of herd immunity at highest standard level, among susceptible and at risk hosts, against all three types of the virus.