Antibody Responses to Hydatid Cyst in Experimentally Infected Lambs

By now, very little is known about events occurring during early infection and innate immunity to infection with E. granulosus following ingestion of the infective egg stage and establishment of the primary cyst. In this study, ten lambs of 4 6 months old of mixed sexes were divided into 2 groups of 5 lambs (one test and one control group). Each lamb in test group received 2000 intraperitoneally protoscolices and each lamb in the control group was injected only PBS. Sera were collected every two weeks until 24 weeks after challenge from each group and serum antibodies were tested by ELISA. Also white blood cells were measured every 2 weeks during this trial. All lambs were killed after 6 months and the internal organs were inspected for hydatid cysts. The results showed that the production of antibody was higher in three lambs of the test group in comparison with control group. In these lambs, hydatid cysts were observed in internal organs. The number and also the average size of hydatid cysts in these lambs were different. In two lambs of the test group, the level of antibody was increased gradually for a few weeks and was then constant. No cyst was observed in these lambs. The numbers of leukocytes including: eosinophils, lymphocytes, neutrophils and monocytes were increased in all of the lambs challenged with protoscolices in comparison with control group. The number of these cells was higher in lambs of test group with no cyst. In conclusion, this study showed that the production of antibody is not able to completely to protect against hydatid cyst and humoral immunity might be correlated with susceptibility to disease in lambs. Key word: Innate immunity Humoral immunity Protoscolices ELISA Lamb INTRODUCTION responses. Antibody responses are weak and are, Cystic echinococcosis (CE) is a widespread following infection. In experimentally infected sheep, chronic endemic helminthic disease caused by antibodies to hydatid antigens can be detected as early as infection with metacestodes (larval stage) of the 4 to 6 weeks postinfection and persist for at least 4 years tapeworm Echinococcus granulosus. CE affects [3]. It has been shown that sheep produce specific humans and a wide range of livestock species [1, 2]. immunological response during natural E. granulosus Although the host-parasite interplay, in most cases of infections [4]. However, it seems that these responses do echinococcosis appears to be harmonious and clinically not lead to raised serum antibody level in many animal or asymptomatic for a long period after infection, the host they are not maintained throughout the course of the does produce a significant immune response against the infection [5]. The understanding of the mechanisms on early stages of infection, while the parasite adapts highly the polarization of different subsets of immune cells may effective evasive strategies to aid in survival. After the be relevant for the rational design of immune intervention oncosphere locates a target organ, the small hydatid cyst and vaccination protocols [6]. The established parasite that commences development is immediately confronted produces significant quantities of antigens that modulate by the host immune responses, which are mainly cellthe immune responses and these include polarized Th2 mediated, especially involving infiltration of macrophages responses, balanced with Th1 responses. The coexistence and eosinophil cells and low-level polarized Th1 of elevated Th1 cytokines, especially interferon (IFN)normally, undetectable in the early two to three weeks World Appl. Sci. J., 8 (8): 1001-1006, 201