EIF4B and viral infectious disease: Little is known about these in primary tissue: both Eif4a1 and Eif4b are essential for mouse development (13, 14); mice with conditional Eif4b deletion in adulthood had increased mortality and susceptibility to viral infection (13); Eif4a2 and Eif4h knock-out mice are viable, but have growth and developmental abnormalities (14, 15).