Follow the link and answer the questions in detail and please be as pecific: htt
ID: 216961 • Letter: F
Question
Follow the link and answer the questions in detail and please be as pecific:
http://iai.asm.org/content/80/12/4264.full.pdf
1) In the human population tested, was IgE made predominantly to adult parasite, juvenile stages or egg antigens? Explain how the studies were conducted and the results obtained. Summarize figures 3, 4 and 5. What types of differential antibody responses were observed in the population tested? How are IgE and IgG4 antibodies made in the human host? What cytokines drive the expression of IgE and IgG4 antibody production?
2) What is the major conclusion of the study?
Explanation / Answer
1)
METHODS: At the beginning of the study, blood samples were collected from a village in Uganda twice, firstly before drug treatment and then 9 weeks after drug treatment. S. mansoni TAL1, TAL3, and TAL5 were expressed in E. coli as GST protein and then were isolated and purified. Then ELISA tests were conducted to measure the levels of IgE targeted to TAL proteins. Western blotting is performed with soluble parasite extracts of cercariae and adult worms.
RESULTS: IgE level against TAL1, TAL3, and TAL5 were calculated.
TAL1 IgE:40%
TAL3 IgE: 20%
TAL5 IgE: 5-10%
TAL5 IgE is associated with reduced reinfection even after allowing for age. Infection peaked in subjects between the ages of 10 and 20 years and then decreased
IgE binding to TAL5 is a cross-reactive component of the TAL3 IgE response. there was a degree of cross-reactivity which was also tested by reciprocal inhibition ELISAs.
different TAL proteins are expressed at different stages of life cycle of S. mansoni. TAL3 is expressed in adult worms, and TAL5 is expressed in infectious larvae.
Figure 3 shows cross-reactivity of TAL IgE.
TAL1 IgE has minimal cross-reactivity for the other two antigens.
IgE binding to TAL3 was inhibited 20% by TAL1 and 60% by TAL5.
IgE binding to TAL5 was not influenced by TAL1 but was completely inhibited by TAL3
Figure 4 shows that the amino acid sequences of the three TAL proteins are aligned.
TAL5 and TAL3 have the most sequence similarity. Their full-length sequences are 45% identical and 69% conserved, and the domains containing the EF-hand motifs (residues 1 to 67) are 63% identical and 82% conserved. The same domains in TAL5 and TAL1 are only 39% identical.
Figure 5: TAL3 transcription is largely restricted to adult worms, while TAL5 transcription is high in cercariae and very low in adult worms. These expression patterns were also present at the protein level, as confirmed by Western blotting of parasite extracts.