Question

The Herpes Simplex Virus (HSV) produces a protein that blocks extracellular binding site on the Complement Receptor (CR1). This facilitates HSV evasion of the Complement Pathway by doing which of the following (select one)? Explain

	A.	Prevents formation of Membrane Attack Complex
	B.	Inhibits recruitment of macrophages and neutrophils
	C.	Blocks binding of C1q to antibodies
	D.	Inhibiting phagocytosis of virus
	E.	Blocks formation of reactive thioester moiety in C3 and prevents deposition of C3b on surface of virus.

Answer 1

Answer E

Blocks formation of reactive thioester moiety in C3 and prevents deposition of C3b on surface of virus. Explanation --Whenever there is invasion by Bacteria ,fungi and viruses or tumour cells then Alternate complement pathway is activated .HSV1 and HSV2 produces GC1 and GC2 respectively which block the Extracellular binding site on Complement receptor 1 .Complement receptor is also known as C3b .So it gc protein blocks the formation of reactive thioester moeity on C3b and interaction of gC-1 with C3b blocks its interaction with properdin ,Factor B and C5 resulting in inhibition of complement activation. As interaction between C3b ,factor B and Properidin is required to form activated C5a it doesnt take place and So formation of C5b,6,7,8,9 that is Membrane attack complex is not formed and lysis of virus by Complement doesnt take place.