Biology subjects

Francis, A. C.

Publications and source records attributed to Francis, A. C..

3 recordsLinked to original sources

bioRxiv2025

Structural, biophysical, and virological mechanistic characterization of HIV-1 capsid-targeting antivirals

Due to its significant role in virus replication, the HIV capsid is an attractive antiviral target. This is validated by the recent clinical approval of lenacapavir for both treatment and pre-exposure prophylaxis (PrEP). PF74 is a well-characterized capsid-targeting antiviral that was discontinued in further study due to potency and metabolic issues. We hypothesized that making chemical modifications at certain sites of PF74 could result in capsid-targeting antivirals with improved potency and bioavailability. Our cumulative studies show that making changes at the R1 and R3 positions of PF74 results in compounds with increased antiviral potency, increased stability of wild-type HIV capsid hexamers and virions, tighter binding to wild-type HIV capsid hexamer compared to PF74, and different interactions at the "FG" binding site of capsid compared to PF74. These data provide insights into the design of future capsid-targeting antivirals relevant for clinical use.

biochemistry↗

bioRxiv2025

The host protein cyclophilin A inhibits HIV-1 nuclear entry by decreasing capsid elasticity

Binding of the host protein cyclophilin A (CypA) to the HIV-1 capsid exerts a variety of effects on infection, including enhancement of reverse transcription, stabilization of the capsid, and promotion of nuclear entry. For several HIV-1 mutants, CypA binding inhibits nuclear entry by an unknown mechanism. We recently demonstrated that HIV-1 cores are elastic and that HIV-1 mutants with inelastic capsids are impaired for nuclear entry and infection of nondividing cells. Here we show that CypA prevents infection of nondividing cells by such mutants and inhibits their entry into the nucleus. CypA binding to mutant cores further reduced their elasticity in vitro, and this effect was reversed by suppressor mutations that restored nuclear entry. We suggest that HIV-1 nuclear entry involves temporal modulation of capsid elasticity by host proteins prior to and during traversal of the nuclear pore.

microbiology↗

bioRxiv2024

The primary mechanism for highly potent inhibition of HIV-1 maturation by lenacapavir

Lenacapavir (LEN) is a highly potent, long-acting antiretroviral medication for treating people infected with muti-drug-resistant HIV-1 phenotypes. The inhibitor targets multifaceted functions of the viral capsid protein (CA) during HIV-1 replication. Previous studies have mainly focused on elucidating LENs mode of action during viral ingress. Additionally, the inhibitor has been shown to interfere with mature capsid assembly during viral egress. However, the mechanism for how LEN affects HIV-1 maturation is unknown. Here, we show that pharmacologically relevant LEN concentrations do not impair proteolytic processing of Gag in virions. Instead, we have elucidated the primary mechanism for highly potent inhibition of HIV-1 maturation by sub-stoichiometric LEN:CA ratios. The inhibitor exerts opposing effects on formation of CA pentamers versus hexamers, the key capsomere intermediates in mature capsid assembly. LEN impairs formation of pentamers, whereas it induces assembly of hexameric lattices by imposing an opened CA conformation and stabilizing a dimeric form of CA. Consequently, LEN treatment results in morphologically atypical virus particles containing malformed, hyper-stable CA assemblies, which fail to infect target cells. Moreover, we have uncovered an inverse correlation between inhibitor potency and CA levels in cell culture assays, which accounts for LENs ability to potently (with pM EC50 values) inhibit HIV-1 maturation at clinically relevant drug concentrations. Author SummaryLenacapavir (LEN) is the first-in-class HIV-1 capsid targeting antiretroviral that exhibits multimodal modality to inhibit both early and late steps of viral replication. Our studies here have elucidated previously undescribed structural and mechanistic bases for a highly potent antiviral activity of LEN during viral egress. These findings will inform clinical applications of LEN as a potent HIV-1 maturation inhibitor and aid the development of second-generation inhibitors targeting assembly of the mature viral capsid.

microbiology↗