Scientists have developed a vaccine which provides a strong immune response against HIV in mice, an advance that could lead to potent single-dose vaccines for a range of infectious diseases.
The vaccine candidate, when delivered along with two powerful adjuvants that stimulate the immune system, could produce a wide diversity of antibodies against the HIV virus, according to a new study published in the journal Science Translational Medicine.
Researchers from the Massachusetts Institute of Technology in the US found that the vaccine accumulated in the lymph nodes and remained there for up to a month, allowing mice to build up a much greater number of antibodies against the HIV protein.
This strategy may lead to new vaccines that only need to be taken once for a range of infectious diseases, including HIV or Sars-CoV-2, scientists say.
“This approach is compatible with many protein-based vaccines, so it offers the opportunity to engineer new formulations for these types of vaccines across a wide range of different diseases, such as influenza, Sars-CoV-2, or other pandemic outbreaks,” said Christopher Love, a co-author of the study from MIT.
Adjuvants are commonly given along with vaccines to help stimulate a stronger immune response against proteins present on pathogens.
For instance, protein-based vaccines like those for hepatitis A and B are delivered along with the adjuvant aluminium hydroxide, also known as alum, which helps the body form a stronger memory of the infectious agent.
Scientists previously developed another adjuvant called saponin derived from the bark of the Chilean soapbark tree.
Researchers have shown that a tiny nanoparticle formulation of saponin, along with an inflammation-promoting molecule called MPLA, can be used as an adjuvant for an HIV vaccine under trial.
An alum and SMNP combination used as an adjuvant for the vaccine could generate even more powerful immune responses against HIV or SARS-CoV-2, scientists say.
Scientists suspect this combination boosts the immune response, specifically via the body’s B cells, which produce antibodies.
They found that such a vaccine combination accumulated in the mice lymph nodes, causing their B cells to undergo rapid mutations to generate a mix of antibodies against HIV.
Researchers showed that the SMNP and alum combination helped an HIV protein penetrate through a protective layer of cells around the lymph nodes without being broken down.
“As a result, the B cells that are cycling in the lymph nodes are constantly being exposed to the antigen over that time period, and they get the chance to refine their solution to the antigen,” Dr Love explained.
Scientists liken this process to what occurs during a natural infection, when antigens can remain in the lymph nodes for weeks, giving the body time to mount an immune response.
“What’s potentially powerful about this approach is that you can achieve long-term exposures based on a combination of adjuvants that are already reasonably well-understood, so it doesn’t require a different technology,” Dr Love said.
“It’s just combining features of these adjuvants to enable low-dose or potentially even single-dose treatments,” he said.
