Virus-like particle (VLP) vaccines are typically comprised of multiple copies of a protein antigen that, when assembled together, mimic the conformation of a native virus. The protein shell that coats a virus, called the “capsid,” is an important component of a vaccine.

Some viruses are enveloped, meaning that the capsid is coated with a lipid membrane known as the viral envelope. This envelope comes from the infected cell, or host, in a process called "budding." During the budding process, newly formed virus particles become "enveloped" or wrapped in an outer coat that is made from a small piece of the cell's plasma membrane. The envelope may play a role in helping a virus survive and infect other cells.

Examples of enveloped viruses include influenza, respiratory syncytial virus (RSV), herpes viruses and HIV. Examples of non-enveloped viruses include norovirus, rotavirus and human pappillomavirus (HPV). LigoCyte has developed VLP vaccines against both enveloped and non-enveloped viruses.

LigoCyte has developed core technologies to efficiently produce a wide range of virus-like particle vaccines. Virus-like particles, or VLPs, mimic the external protein structure of a virus without including the genetic material (DNA or RNA) that is necessary for viral replication. The human immune system responds to a VLP vaccine as if it is seeing the live virus, which allows the body to build immune defenses capable of fighting infections. Without genetic material, VLP vaccines are incapable of causing infections themselves while at the same time presenting viral antigens in the most authentic configuration possible.

Anti-viral vaccines have traditionally been prepared by using attenuated, or weakened, forms of the infectious virus. This type of vaccine has been effective in preventing many types of diseases, but involves complications in manufacturing and may have limited applications in treating certain populations. Examples of newer VLP-based vaccines include the recently licensed vaccines against human papillomavirus (HPV), Merck’s Gardasil® and GSK’s Cervarix®.

LigoCyte produces VLP vaccines in two ways. In the case of our clinical-stage norovirus vaccine, the capsid protein of norovirus is expressed in cell culture where it spontaneously forms into VLPs, each comprised of 180 copies of the protein. This type of VLP production is relatively straightforward, and is similar to the process used to produce the currently licensed HPV vaccines. For more information on LigoCyte’s norovirus vaccine program based upon this exciting new technology, Click Here

The other method LigoCyte has developed to produce VLP vaccines applies specifically to enveloped viruses. Many viruses (e.g. influenza, herpes simplex and respiratory syncytial virus) have viral envelopes covering their protein capsid shells. The envelopes are typically derived from portions of the host cell membranes, and the unique structure of these enveloped viruses has made them a challenging target for VLP development in the past.

LigoCyte is engineering enveloped virus VLPs using a retroviral core protein called Gag. The use of a common core protein as a scaffold for multiple VLPs has advantages in vaccine manufacturing and purification, allowing LigoCyte to standardize the process for developing enveloped VLP vaccines. This platform VLP technology is applicable to a number of desirable vaccine targets including influenza, herpes simplex, respiratory syncytial virus, cytomegalovirus and parainfluenza virus. For more information on LigoCyte’s influenza vaccine program based upon this exciting new technology, Click Here.