Lactobacilli-Expressed Single-Chain Variable Fragment (scFv) Specific for Intercellular Adhesion Molecule 1 (ICAM-1) Blocks Cell-Associated HIV-1 Transmission across a Cervical Epithelial Monolayer

Abstract

The vaginal and cervical epithelia provide an initial barrier to sexually acquired HIV-1 infection in women. To study the interactions between HIV-1-infected cells or cell-free HIV-1 and the reproductive epithelium, the transmission of HIV-1 by infected cells or cell-free virus across human cervical epithelial cells was examined using a Transwell culture system. Cell-associated HIV-1 was transmitted more efficiently than cell-free virus, and monocyte-associated virus was transmitted most efficiently. Abs to ICAM-1 added to the apical side of the epithelium blocked cell-mediated transepithelial HIV-1 transmission in vitro. When used in a previously described model of vaginal HIV-1 transmission in human PBL-SCID mice, anti-murine ICAM-1 Abs (0.4 μg/10 μl) also blocked vaginal transmission of cell-associated HIV-1 in vivo. To evaluate a candidate delivery system for the use of this Ab as an anti-HIV-1 microbicide, anti-ICAM single-chain variable fragment Abs secreted by transformed lactobacilli were evaluated for their protective efficacy in the Transwell model. Like the intact Ab and Fab derived from it, the single-chain variable fragment at a concentration of 6.7 μg/100 μl was able to reduce HIV-1 transmission by 70 ± 5%. These data support the potential efficacy of an anti-ICAM Ab delivered by lactobacilli for use as an anti-HIV-1 microbicide.

Engineering of a Human Vaginal Lactobacillus Strain for Surface Expression of Two-Domain CD4 Molecules

“…Numerous avenues to curtail the HIV epidemic are currently being investigated (9,26,27,37,42,47,49). While an effective HIV vaccine remains the most important goal, the ability of HIV to mutate rapidly and evade the immune response has made the development of a vaccine problematic, necessitating the pursuit of additional innovative approaches.…”

Reducing Urogenital Infections Including HIV in Sub-Saharan Africa - Can Probiotics Be a Viable Paradigm?

“…FI-1, FI-2, and FI-3 are also peptides that can interfere with gp41 and were cloned into L. plantarum and L. gasseri [Pusch et al 2006]. L. reuteri RC-14, which has been studied as a potential probiotic, was modified to produce 3 HIV entry and fusion inhibitors: CD4D1D2IgKLC, MIP-1, and T-1249 Antibody to the cellular adhesion molecule intercellular adhesion molecule has been shown to inhibit cellmediated trans-epithelial HIV-1 transmission in vitro and was functionally excreted by a bioengineered strain of L. casei [Chancey et al 2006]. Some of these products have been used in rodent models, but none has been tested in humans.…”

Enhanced Neutralization of HIV by Antibodies Displayed on the S-Layer of Caulobacter crescentus

“…It is reasoned that, being a normal component of the vaginal flora, engineered lactobacilli will provide long-term stable expression of anti-HIV inhibitors. Engineered lactobacilli have been shown to inhibit HIV infection when tested in vitro (5,6,36); however, it is unclear that stable expression of inhibitors by the engineered lactobacilli will be maintained in vivo given the abundant and dynamic normal flora of the female genital tract. We propose to develop an alternative bacterial expression system using a nonpathogenic bacterium that presents HIV-blocking agents efficiently, is inexpensive to produce as a killed, stabilized agent, and is likely to be compatible with exposure to human mucosal tissue.…”