Determination the Time of Toxoplasmosis among Pregnant Women by using IgG Avidity to Various Toxoplasma Gondii Antigens

Toxoplasmosis is caused by Toxoplasma gondii, which is an intracellular protozoan parasite. Its main host is the cat. It is one of the most common human parasites. The main objective of this study is to determine the time of T. gondii infection among pregnant women by using avidity test of Toxoplasma IgG to various Toxoplasma antigens. The study period was from August 2017 to February 2018 to study the time of toxoplasmosis among 180 pregnant women and 100 non pregnant married women as control attending to hospitals, primary health care centers and some private medical laboratories. The pregnant women were examined for Toxo-IgG seroprevalence by using ELISA technique, and then examined their avidity of antibodies for specific Toxoplasma antigens by using line immune assay. The rates of Toxo-IgG seropositive were64 (35.56 %) among pregnant women. Regarding the reactivity of determined Toxo-IgG against various Toxoplasma antigens, the rates were 40(62.50%), 39 (60.93%), 63(98.43%) ,55(85.93%) ,63(98.43%), 62(96.87%) ,41(64.04%) and 42(65.62) positive for Toxoplasma ROP1C, MIC3, GRA7, GRA8, p30, MAG1,GRA1,rSAG1 antigens, respectively. Considering the avidity of Toxo-IgG for these antigens, the rates of high avidity were higher than low and intermediate avidity. So, the highest rate of high avidity was 85.0% for ROP1c antigen. It is concluded that the highest rate of predicting Toxoplasma infection among pregnant women was for a period of more than 6 months, which makes it less dangerous for maternal and fetal health.


Introduction:
Toxoplasma gondii (T. gondii) is an obligate intracellular protozoan parasite, infecting a wide range of warm-blooded animals, including humans [1]. Various ways may cause the T. gondii infection to humans, including consumption of: uncooked meat of animals having tissue cysts, food or water contaminated with infected cat feces or by infected environmental samples (e.g. soil, cat litter). Adding to that, the infection of a fetus transplacentally from the mother [2,3].
The T. gondii infection has a major complication represented by congenital infection [4,5]. Fetus may be infected by T. gondii via mother who has this infection for the first time during pregnancy. Because of immature immune response of fetus, it may experience severe sequelae. This includes ocular and/or mental impairment, epilepsy, hydrocephalus or intrauterine death and abortion [6]. As the pregnancy advances to the end, the transplacental transmission risk becomes higher; however, the first trimester of pregnancy is exposed to the highest risk of severe sequelae [7].
These proteins are considered to play an essential role in intracellular parasitism invasion of vertebrate cells by the protozoan T.gondii. Binding to the host cell, triggered apical release of the micronemal protein MIC at the tight attachment zone was formed between the parasite and the host cell. In the second step, invagination of the host cell plasma membrane was initiated by discharging the rhoptry protein ROP to form a nascent parasitophorous vacuole (PV). ROP is fully discharged into the vacuole upon completion of the invasion time. In contrast to these very rapid early events, release of the dense granule markers GRA [8-10].
The net antigen binding force of antibodies population is defined by terms of "avidity" or "functional affinity". These terms are more preferred than the "affinity" term. The IgG avidity can be measured by determining the antigen binding force of specific IgG antibodies [11] by using reagents to remove IgG from the immobilized antigen.

Materials and Methods:
A cross sectional study was carried out in Kirkuk governorate from August 2017 to Comparison carried out using Chi-square ( X 2 ) and Probability ( P value ). The P value ≤ 0.05 was considered to be statistically significant (S), less than 0.01 is considered as highly significant (HS), then greater than 0.05 is considered as non-significant.

Results:
A total 180 pregnant women whose age ranged between (18-42 years old) were examined for seroprevalence of specific Toxo-IgG by using ELISA technique. The seroprevalence of Toxo-IgG was 64(35.56%) among pregnant women. While the seroprevalence among 100 control (non pregnant) married women was 5 (5.0 %), as shown in Table 1. antigens, respectively as shown in Table 2.  Table 3. Considering the time of toxoplasmosis among Toxo-IgG seropositive pregnant women depending on Toxo-IgG avidity to various Toxo-antigens, as described in Table 4. From the total 64 pregnant women whose suspected toxoplasmosis was for more than 6 months were 50.00% .So, 35.95% of them are suspected to probably infection since 3-6 months; while the remain 14.06% of them are suspected to have toxoplasmosis within less than 3 months ago.  than 6 months of infection. This may be due to that most pregnant women are exposed to Toxoplasma infection before pregnancy. So, this reflects the lowering risk of maternal Toxoplasma infection to their fetus as seen in our community, which was few or rare case of fetal Toxoplasma infection and its complication from infected mother. While the rate of infection since less than 3-6months was 35.95% and the lowest was the rate of suspicion to toxoplasmosis since less than 3 months ago, which was 14.09%,as showed in Table 4.

Conclusions:
The highest rate of pregnant women was suspected to be infected by Toxoplasma infection since more than 6months and this makes it less dangerous for maternal and fetal health.