Detection of immunoglobulin G levels produced by oral polio vaccine in HIV infected children in Jos, Plateau State, Nigeria

Introduction Disease eradication requires a long time and efficient management as compared to disease control program. After successful small pox eradication, polio virus causing poliomyelitis is choice for next eradication. The corner stone of the global polio eradication initiative is the immunization of children with multiple doses of Oral Polio Vaccine (OPV) through both Routine Immunization (RI) and Supplemental Immunization Activities (SIAs). This informed our design of this prospective study. Objective is to determine levels of Immunoglobulin G antibodies produced in HIV infected children aged (one to ten years) vaccinated with Oral Polio Vaccine (OPV) in Jos, Plateau State, Nigeria. Methods One hundred and eighty-two children infected with HIV who had received Oral Polio Vaccine (OPV) at least four times had their blood samples collected and assayed for the presence of Polio Specific IgG antibodies using IgG ELISA test kit (DEMEDITEC Diagnostic GmbH, Germany). Three millilitre (3ml) of venous blood samples were collected aseptically by venepuncture. Sera obtained were assayed using Enzyme immunoassay detection and quantitative determination of human IgG antibodies against poliomyelitis virus in serum and plasma (Demeditic Poliomyelitis Virus IgG ELISA DEPOL01-Germany). Results The result showed that 95.6% (174/182) of the tested children had detectable IgG antibodies against polio virus. The high proportion of 95.6% recorded in this study indicates HIV infected children responded effectively to the Oral Polio Vaccine (OPV) being used in the ongoing polio eradication initiative. In this study, 4.4% (8/182) of the HIV infected children were not producing detectable amount of antibodies that could protect them from exposure to wild type of polio virus. Conclusion This study shows that HIV infected children had detectable antibodies (Immunoglobulin G) against polio virus. Despite the overall progress recorded in the fight against poliomyelitis in Nigeria, a lot needs to be done to further strengthen the fight against poliomyelitis in Nigeria.


Introduction
After successful small pox eradication, polio virus causing poliomyelitis became the next focus for eradication [1,2]. Poliomyelitis is a highly infectious disease that mainly affects children under five years of age.
It invades the nervous system and can cause total paralysis in a matter of hours. The wild types are of three (3) known serotypes (1, 2, and 3). The virus is transmitted from person to person and spread mainly through the faecal-oral route or less frequently by a common vehicle (for example contaminated water and food) and multiplies in the intestine [3]. For symptomatic cases, initial symptoms are fever, fatigue, headache, vomiting, stiffness of the neck and pain in the limbs. One in every 200 infections leads to irreversible paralysis. In the presence of paralysis, death occurs in 5 to 10% when their breathing muscle become immobilized. There is no cure for poliomyelitis. It can only be prevented. Polio vaccine given multiple times can protect a child for life [4,5]. generously with massive funding [6]. With this initiative and concerted effort, through the use of immunization with polio vaccine, the world has witnessed a remarkable reduction in paralytic poliomyelitis cases from 350,000 in more than 125 countries in 1988 to 247 cases in 10 countries as at October 2014 [7]. The worldwide sustained use of polio vaccine since 1988 has led to a reduction in the number of cases of poliomyelitis by more than 99% globally.
The corner stone of the global polio eradication initiative is the immunization of children with multiple doses of Oral Polio Virus Vaccine (OPV) [7,8]. The key advantage in the usage of OPV was the ease of administration and the efficient reduction of mucosal colonisation thereby limiting polio shedding and person to person transmission of polio virus [9]. The risk of an adverse event after  Exclusion criteria: HIV infected children whose age did not fall within the age group 1-10 years. Children whose parent or guardians refuse to give consent for their enrolment in the study. Children of HIV negative mothers and children of HIV positive mothers with other debilitating illnesses such as malignancy, diabetes mellitus and sepsis.

Ethical clearance: ethical clearance was obtained from Jos
University Teaching Hospital (JUTH) and Faith Alive Foundation, ethical clearance committees before embarking on the exercise.
Consents obtained from parent/guardian after explaining what the study is all about before enrolling the children for the study. Data/statistical analysis: the data obtained in this study were analysed using Statistical Package for Social Science (SPSS) computer software program. Pearson Chi-square was used to test for association between discrete variables. Statistical significance was accepted at P<0.05 (95%) confidence level.

Results
A total of 182 children aged 1-10 years' male and female infected with HIV had their blood samples collected and analysed for the presence of polio specific IgG antibodies using IgG ELISA test kit (DEMEDITEC Diagnostic GmbH, Germany) ( Table 1). The proportion of HIV infected children aged 1 to 10 years who developed IgG antibodies to polio virus following vaccination from the two clinics tested showed that APIN/JUTH had positive prevalence of 96.7%, while FAITH ALIVE clinic had 94.5%. The overall percentage prevalence of polio specific IgG antibody among the study population was found to be 95.6% ( Table 2). The result of the distribution of Polio IgG antibodies concentration among HIV infected children shows that concentration <10 u/ml were negative, while those ≥10 u/ml were positive (Table 3). The result for concentration 10-19 u/ml was 83(45.6%), 20-29 u/ml was 78(42.9%) and concentration <30u/ml was 13(7.1%), all were positive (Table 3). This difference in the seropositivity could be due to the number of children sampled and analysed with concentration <30 having the lowest seropositivity and concentration 10-19 u/ml having the highest seropositivity.
The result of gender as a risk factor was also determined in this study as shown in Table 4. The highest prevalence of 96.7% (87/90) was observed among female children as compared to 94.6% (87/92) recorded among the male counterpart. But, there was no statistically significant association between sex and seropositivity to the polio virus. Age as a risk factor for polio virus infection was also determined in this study ( Table 5). The higher seropositivity of 95.9% (140/146) was found among older children aged 6-10 years as compared to seropositivity of 94.4% (34/36) found among younger children aged 1-5 years ( Table 5). The result of the association between polio IgG and level of father's education: χ 2 = 1.95; df = 3; p-value = 0.58: thus P > 0.05 and association between polio IgG and level of mother's education: χ 2 = 1.67; df = 3; p-value = 0.64: thus, P > 0.05 were not statistically significant as shown in Table 6. The result from Table 7, shows the association between Polio IgG and sources of drinking water and association between Polio IgG and type of toilet facility.

Discussion
From the results obtained from the proportion of HIV infected children who developed IgG antibodies to polio virus following vaccination. The high prevalence of 95.6% recorded in this study indicates children responded effectively to the OPV being used in the polio eradication initiative ( Table 2). This finding was higher than the 73.6% prevalence  Table 4. The result showed that gender had no effect on the overall prevalence of polio virus antibody. This is to say that both male and female children had equal chances of being immunized during routine immunization sessions and also equal chances of exposure to natural infection. This agrees well with what had been observed by [13].
The result of age as a risk factor shows that the higher seropositivity was found among older children as compared to seropositivity found among younger children aged 1-5 years ( Table 5). The result could be deduced to more doses of the oral polio vaccine and to declining exposure to circulating oral polio vaccine. Also, age naturally determines the number of doses taken either through routine immunization or during campaigns. This finding is in agreement with [14] who stated that increase in immunity level has earlier been associated with age. The result of the association between polio IgG and level of father's and mother's education were not statistically significant. The result is dissimilar to the work of [12]. This might be because of intense campaign through immunization plus days where children are followed in homes, schools, churches, and play grounds with the oral polio vaccine. As a result, parents whose children never had any form of formal education had detectable antibodies to polio virus. This reflects that fact that irrespective of educational status, the general population has been sensitized on the immunization of children and may be attributed to the high level of antibody production as showed in this study. The association between polio IgG and sources of drinking water and between polio IgG and type of toilet facility were not statistically significant at P > 0.05. All these are

Conclusion
This study shows that HIV infected children had detectable antibodies What is known about this topic • All studied population had appreciable levels of protection against polio virus due to levels of antibodies detected; • No significant association between detection of IgG in children in relation to gender and age; • Educational status of parent had statistically significant relationship with detection of antibodies in children. • This research work demonstrated the progress that has been made towards the eradication of poliomyelitis in Nigeria.