Evaluation of the antiretroviral effects of a PEG-conjugated peptide derived from human CD38

Abstract

Objective: Cell infection by HIV-1 is inhibited by both the expression of CD38 and a soluble peptide (sCD38p) corresponding to its extracellular membrane-proximal amino acid sequence (amino acids 51 – 74). We show here the effects of PEG conjugation to sCD38p and provide new insights into the mechanisms behind the anti-HIV-1 effects of CD38 and derived peptides. Research design/methods: In-vitro and in-silico study. Results: PEGylation of sCD38p increased its ability to inhibit replication of HIV-1 in MT-4 cells and syncytia formation in cocultures of MT-2 and persistently HIV-1_IIIB-infected H9_IIIB cells. In silico modeling suggests that sCD38p and CD4 form stable heterodimers involving, among others, an interaction between lysine 57 (K57) of CD38 and a groove in the CD4 receptor, which, in CD4/gp120 complexes, is partially occupied by a lysine residue of the HIV-1 envelope glycoprotein. K57 substitution with a glycine in sCD38p impaired its ability to inhibit syncytia formation in MT-2/H9_IIIB cell cocultures and gp120 binding to CD4 in a mouse T cell line expressing human but not mouse CD4. Conclusions: PEGylation significantly improves the anti-HIV-1 activity of sCD38p, whose effect is probably due to competition with gp120 for a common binding site on CD4 although other mechanisms cannot be excluded so far. The inhibitory concentrations of the sCD38p-PEG as well as its poor toxicity, merit further consideration in anti-HIV-1 strategies.

Keywords::

• antiretroviral
• CD38
• CD4
• gp120
• MTT assay
• protein–protein interaction
• therapeutic peptide

Acknowledgements

The authors are thankful to Fabiola Mancini, Walter Malorni and Paola Matarrese, ISS, Rome, Italy, for contributing the photographic equipment and Zuleika Michelini, ISS, Rome, Italy, for providing virus 97ZA009. Finally, the authors would like to thank M. Letizia Barreca, for performing the energy minimizations of the docked complexes.