Correct option is D
Explanation-
A. Hepatitis C virus (HCV) → (iv) By evading the action of IFNα/β the major antiviral cytokine
Hepatitis C virus is a RNA virus that infects liver cells (hepatocytes). A key antiviral defense of host cells is the type I interferon (IFN-α/β) system, which induces antiviral gene expression, inhibits viral replication and activates natural killer (NK) cells and cytotoxic T lymphocytes (CTLs).
HCV evades this by producing the NS3/4A protease, which cleaves TRIF and MAVS, key adaptor proteins in the interferon signaling pathway. This blocks interferon production and signaling, allowing the virus to persist.
B. Herpes Simplex Virus (HSV) → (i) By inhibiting antigen delivery to MHC class I receptors on virus infected cells thus preventing presentation of viral antigen to CD8+ T cells.
HSV is a DNA virus that infects epithelial cells and neurons. To be killed by CD8+ T cells, viral peptides must be presented on MHC I molecules. HSV evades this by blocking TAP (Transporter associated with Antigen Processing) function, preventing viral peptide loading onto MHC I, This inhibits antigen presentation, so CD8+ T cells cannot detect infected cells.
C. Vaccinia virus → (ii) By evading antibody-mediated destruction via complement activation
Vaccinia virus is a large DNA virus (used in smallpox vaccine). Complement system is part of the innate immune system, responsible for lysis of pathogens, enhancing phagocytosis, recruiting immune cells. Vaccinia virus evades this by producing vaccinia complement control protein (VCP), This protein mimics host regulators of complement .
D. Human Immunodeficiency Virus (HIV) → (iii) By constantly changing their antigens called antigenic variations.
HIV is a retrovirus that targets CD4+ T cells. The host immune system tries to generate neutralizing antibodies and cytotoxic T cell responses. HIV evades this by high mutation rate during reverse transcription, rapid changes in envelope glycoproteins gp120 and gp41. This leads to antigenic variation — immune system can’t keep up with the evolving virus.
Correct answer: A–iv, B–i, C–ii, D–iii (Option d)
