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A variety of proteins have been identified that restrict infection by different viruses. One such restriction factor is the rhesus macaque variant of TRIM5α (rhTRIM5α), which potently blocks infection by HIV-1. The block to infection mediated by rhTRIM5α occurs early after entry into the host cell, generally prior to reverse transcription. However, proteasome inhibitors reveal an intermediate step of restriction in which virus can complete reverse transcription, but still fails to infect the cell. While proteasome inhibitors have been a useful tool in understanding how restriction takes place, the role of the proteasome itself during restriction has not yet been examined. Here, we characterize the interaction of rhTRIM5α and incoming virions with the proteasome. We show that proteasomes localize to rhTRIM5α cytoplasmic bodies, and this localization is more evident when the activity of the proteasome is inhibited pharmacologically. We also show that restricted virus associates with complexes of proteasomes and rhTRIM5α, suggesting that rhTRIM5α utilizes the proteasome during restriction. Finally, live cell imaging experiments reveal that virus associates with proteasomes, and proteasome inhibition affects the duration of association. Taken together, these studies implicate the proteasome as playing a functional role during rhTRIM5α restriction of incoming virions.

Materials that respond to physiological stimuli are important in developing advanced biomaterials for modern therapies. The reversibility of covalent-crosslinks formed by phenylboronate (PBA) and salicylhydroxamate (SHA) has been exploited to provide a pH-responsive gel for application to the vaginal tract. Dynamic rheology reveals that the gel frequency-dependent viscoelastic properties are modulated by pH. At pH 4.8 the viscous component dominates throughout most of the frequency range. As the pH increases, the characteristic relaxation time continues to increase while the G'Plateau levels off above pH 6. At pH 7.5, the elastic component dominates throughout the frequency sweep and is predominately independent of frequency. Particle tracking assessed the transport of both fluorescently labeled HIV-1 and 100 nm latex particles in the PBA-SHA crosslinked gel as a function of pH. At pH 4.8 the ensemble-averaged mean squared displacement at lag times greater than three seconds reveals that transport of the HIV-1 and 100 nm particles becomes significantly impeded by the matrix, exhibiting diffusion coefficients less than 0.0002 μm2 s−1. This pH responsive gel thus displays properties that have the potential to significantly reduce the transport of HIV-1 to susceptible tissues and thus prevent the first stage of male-to-female transmission of HIV-1.