5. Two individuals (A and B) were infected with the HIV virus. Cells from indivi

Question

5. Two individuals (A and B) were infected with the HIV virus. Cells from individual A express HLA AlI and HLA-23 proteins, while cells from the individual B have HLA-A30 and HLA-A03. The peptides from the nef protein produced by the HIV virus, which can be presented by these MHC molecules, are shown below. Based on this information, please answer the following questions. INDIVIDUAL A start end peptide IC50(nM) 1 allele INDIVIDUAL B start end peptide IC50(nM) 3 HLAA11 9 17 SVIGWPTVR 144 HLA-A 11 31 39 GAASRDLEK 180 5 HLA-A11 144 152 KLVPVEPDK 361 5 3 HLA-A 03 188 196 RLAFHHVAR 80 HLA-A'03 4 HLAA30 132 140 GVRYPLTFG 82 HLAA23 137 145 LTFGWCYKL 409 6 HLAA'03 163 171 SLLH 7 H,a.sma 1^^ t UDVFpnw 16n a. Assume that these are the only MHC molecules expressed by these individuals, and nef is the only protein expressed by HIV. Given this information is correct, which individual would remain "symptom-free" longer after infection? Please explain your logic briefly

Explanation / Answer

Which individual will remain asymptomatic, we can deduce it by considering the IC50 values for different peptides described in the table. IC50 value is the basically a measure for the effectiveness of drug, substance to inhibit a cellular process. At the IC50 value of a substance, 50% of the process is inhibited. Higher the IC50 value higher the concentration of the drug needed to inhibit the cellular process. In this case higher the IC50 value, higher the protein concentration will be needed to induce a an immune response and thuse symptoms. From the table it can be seen that Individual A encounters peptides with higher IC50. A higher protein titer and thus a high viral titer is needed for the inhibition of HLA receptors. On the other hand, in individual B the IC50 values are low and the inhibition is achieved shortly after the infection. HLA's are present on T cells which induce an immune repsonse producing the symptoms therefore individual B would remains symptom free.

b. No becuase the receptors (HLA) in consideration are same and have same properties.

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