New Single-dose Intranasal Vaccine Shows Promise
A new, single dose intranasal vaccine has shown ability to protect Macaques against COVID, as reported in a preprint article on bioRxiv. If it proves effective and safe in humans, it could be a radically effective and simple to administer vaccine against COVID.
Currently, most COVID vaccines are administered intramuscularly and require two doses. However, after immunisation, an infected person can still shed the virus from the upper airways because they do not have local or mucosal immunity, as demonstrated by intramuscular vaccination in non-human primates.
The SARS-CoV-2 virus enters the target the host cell by the spike (S) protein antigen locking on to the cell’s angiotensin-converting enzyme 2 (ACE2) receptor. Thus, the S protein is a critical target for vaccine development.The researchers developed the new vaccine uses a chimpanzee adenovirus which expresses the S protein (ChAd-SARS-CoV-2-S). The chimpanzee adenovirus (also used in the AstraZeneca vaccine) is ideal as an antigen carrier for vaccines as the prevalence of neutralising antibodies against it is low.
In the researchers’ previous work, the vaccine had been administered intranasally to mice with expressed human ACE2 receptors, producing a detectable immune response. The researchers then moved experimentation on to macaques, administering a single intranasal dose of vaccine, followed by intranasal and intrabroncheal challenge with SARS-CoV-2.
A detectable immune response was detected by the presence of anti-S, anti-RBD, and neutralising antibodies, as well as T cell responses. Viral RNA loads measured by nasal swabs were lower in immunised animals, with only one having detectable virus presence, compared to four of six control animals. These results suggest that local infection is prevented, with reduced viral RNA levels and faster viral clearing.
Infection was also measured in broncheal alveolar lavage fluid (BALF)At day seven, immunised animals showed lower viral DNA than controls, corresponding to increased neutralising antibody levels.
Administering the vaccine intranasally could allow protection of the local and surrounding tissues, while reducing disease severity and spread to others. However, the lack of severe pathologies in both sets of animals means that no conclusions can be drawn about the vaccine’s effectiveness in preventing against COVID.
Further research is required to compare the effects of intramuscular and intranasal administration of the vaccine, and the work is yet to be peer reviewed.
Source: News-Medical.Net
Journal information: Hassan, A. O. et al. (2021). A single intranasal dose of chimpanzee adenovirus-vectored vaccine protects against SARS-CoV-2 infection in rhesus macaques. bioRxiv preprint. doi: https://doi.org/10.1101/2021.01.26.428251. https://www.biorxiv.org/content/10.1101/2021.01.26.428251v1
