Wrapping polymer nanoparticles in membranes from human lung epithelial type II cells and immune cells creates a biomimetic system that can act as a decoy for SARS-CoV-2 which is at the heart of the global Covid-19 pandemic. Laboratory tests discussed in the journal Nano Letters show how the "nanosponges" can reduce viral infectivity by almost 90 percent. The new study builds on more than a decade of the team's biomimetic nanosponge platform.

"Traditionally, drug developers for infectious diseases dive deep on the details of the pathogen in order to find druggable targets," explains Liangfang Zhang of the University of California San Diego. "Our approach is different. We only need to know what the target cells are." In other words, the approach works regardless of the nature of the virus and so if it works for SARS-CoV-2 it should work for any future emergent virus that attacks the same cells in the body.

The cloaking with the lung cells makes the nanoparticles mimic the target cells of the virus because all of the target receptors are present in the membrane. The outer membrane of immune system white blood cells, known as macrophages, means that they can also mop up inflammatory cytokine proteins. It is the notorious cytokine storm in response to infection that causes many of the most unpleasant and ultimately lethal effects of Covid-19. ? The UCSD team sent their nanosponges to colleagues at Boston University for testing. The Boston team used the same live strain of the virus they are also using in their vaccine and drug development programs. They found that at a concentration of 5 milligrams per milliliter, the lung cell membrane-cloaked sponges inhibited 93% of the viral infectivity of SARS-CoV-2. The macrophage-cloaked sponges inhibited 88% of the viral infectivity of SARS-CoV-2. [Zhang, Q. et al. Nano Lett. (2020); DOI: 10.1021/acs.nanolett.0c02278]

"From the perspective of an immunologist and virologist, the nanosponge platform was immediately appealing as a potential antiviral because of its ability to work against viruses of any kind," explains Boston's Anna Honko. "This means that as opposed to a drug or antibody that might very specifically block SARS-CoV-2 infection or replication, these cell membrane nanosponges might function in a more holistic manner in treating a broad spectrum of viral infectious diseases." This also means that as the current coronavirus mutates, the same therapy should carry on working, again, it is not targeting the virus itself it is mimicking the target the virus aims at.

The next step is to evaluate the putative therapy in laboratory animals and then move on to human trials.