Prevalence of Poliovirus Specific Salivary IgA and Serum IgG in Orally Poliovirus Immunized Preschool Children

Abstract

This study was conducted in Omdurman municipality hospitals during the period of February 2007 to February 2008 to study the prevalence of poliomyelitis virus antibodies in the saliva and sera of OPV immunized preschool-aged children using an in-house ELISA. Data concerning history of immunization, other medical information and demographic data that collected using structural questionnaire with informedconsent of the mother or gardian of each participant child. One hundred children of 1year to more than 4 years were included. Blood and saliva were collected from each child.Positive control saliva and sera were obtained from multiple OPV immunized children, whereas negative control saliva and sera were obtained from non-OPV immunized children and tested in pilot ELISA study. OPV was heat inactivated and used as a solid phase antigen for coating the ELISA plates. Goat αFc human IgA and IgG conjugated to (Horse radish peroxidase) HPO were used for the detection of salivary IgA and serum IgG respectively. From ELISA pilot studies we elaborated an in-house ELISA to study the prevalence of (poliovirus) PV specific SIgA and IgG in saliva and seraof OPV immunized children. Several factors that could affect IgA, IgG, and IgA/IgG ratio were investigated in this study such as age, sex, and area of residence. In this study the prevalence of polio virus specific salivary IgA and serum IgG were detected in the various age groups of OPV immunized children. The absorbance values of polio virus specific salivary IgA and serum IgG were very high in all age groups. However, the differences between these values among all age groups were not statistically significant. The Pvalue for IgA was (0.36) and for IgG the Pvalue was (0.20). Furthermore, children who received two or five doses of OPV had the same absorbance values for IgA and IgG. Moreover, salivary IgA /serum IgG absorbance valuesratio in all age groups were also non-statistically significant (P= 0.45). These results clearly demonstrated that iv OPV induced both local and systemic Abs responses in all immunized children. Moreover, the prevalence of polio virus specific salivary IgA and serum IgG was the same in both sex. Absorbance values for PV specific salivary IgA was relatively high in comparison with PV specific IgG in both sex, but these differences were not statistically significant (P= 0.294 for IgA and P= 0.255 for IgG) for both isotypes. However, significantly higher salivary IgA/serum IgG absorbance ratio were found in males than in females (P= 0.03). OPV immunized children from various area of residences had high prevalence PV specific salivary IgA and serum IgG. However, the absorbance values of salivary IgA were relatively higher in comparison with polio virus specific serum IgG. However, these absorbance differences were not statistically significant among children of various area of residences for both isotypes (P= 0.383 for IgA and P= 0.276 for IgG), salivary IgA/ serum IgG absorbance ratio were statistically not significant as well (P= 0.058). A linear relationship between salivary IgA and serum IgG was found and OPV immunization armament children with local and systemic Abs responses that make it difficult for wild virus to escape any of the two lines of defense. In this study we concluded that OPV immunization in childhood produces both local and systemic Abs response. The number of doses of OPV, age, sex and area of residence had no significant effect (P>0.05) on the value of salivary IgA and IgG, whereas sex had a significant effect on the salivary IgA/ serum IgG ratio. Our in-house ELISA is a useful tool for monitoring OPV immunization campaigns for the eradication of poliomyelitis