Which HIV viral enzyme is targeted by integrase strand transfer inhibitors (INSTIs), and what is the mechanism of action of raltegravir?

• A HIV reverse transcriptase; raltegravir blocks DNA-dependent DNA synthesis
• B HIV integrase; raltegravir blocks the strand transfer step preventing integration of viral DNA into host genome ✓
• C HIV protease; raltegravir prevents cleavage of Gag-Pol polyprotein
• D HIV gp41; raltegravir blocks six-helix bundle formation inhibiting viral fusion

Explanation

Integrase strand transfer inhibitors (INSTIs) like raltegravir, dolutegravir, bictegravir, and elvitegravir block HIV integrase — specifically the strand transfer step in which the pre-integration complex inserts viral double-stranded DNA into the host chromosome. INSTIs chelate the divalent metal ions (Mg2+) in the integrase active site. Dolutegravir has a higher genetic barrier to resistance than raltegravir and is preferred in current WHO first-line ART. Reverse transcriptase is targeted by NRTIs/NNRTIs; protease by PIs; gp41 fusion by enfuvirtide.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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