Adenovirus antibodies reduce vector vaccine efficacy

Context

• Studies have shown that using the same adenovirus subtypes for repeated vaccination might result in reduced efficacy.

What is an Adenovirus antibody?

• Adenoviruses(family Adenoviridae) are medium-sized (90–100 nm)viruses.
• They are-enveloped (without an outer lipid bilayer) viruses.
• They are icosahedral nucleocapsid containing a double-stranded DNA genome.
  
  
• Adenoviruses: These are a group of common viruses that infect the lining of the eyes, airways, and lungs, intestines, urinary tract, and nervous system.
  • They're common causes of fever, coughs, sore throats, diarrhea, and pink eye.
  • The immune system generated against the adenovirus infection causes the antibodies formation.

How these antibodies illicit response action against vector-based vaccine?

• Pre-existing antibodies cause the relatively low efficacy of the adenovirus-based vaccine in some people.
  • It affects the development of antibodies against the new target.
  • Pre-existing antibodies against adenoviruses will stop the adenovirus particles from getting into cells and making the SARS-CoV-2 spike protein they carry the code for.

Adenovirus as Vector

• Adenoviruses are excellent vectors for delivering genes or vaccine antigens. Adenovirus-based vectors offer several advantages over other viral vectors such as:
  • a broad range of tissue tropism
  • well-characterized genome
  • ease of genetic manipulation including acceptance of large transgene DNA insertions
  • inherent adjuvant properties
  • ability to induce robust transgene-specific T cell and antibody responses
  • non-replicative nature in host
  • ease of production at large scale

Vector-based Vaccines

• Viral vectors are tools commonly used to deliver genetic material into cells.
  • This process can be performed inside a living organism (in vivo) or in cell culture (in vitro). 
  • As a medium of transport: Viruses have evolved specialized molecular mechanisms to efficiently transport their genomes inside the cells they infect. 
  • Functioning: They are then inserted into the genome of a non-pathogenic organism, where they are expressed on the organism's surface and can elicit an immune response.