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A vaccine recently developed by the United States National Institute of Allergy and Infectious Diseases (NIAID) is attempting to prepare the world for the next potential pandemic stemming from mosquito-borne diseases. 

Prior to COVID-19 - the respiratory infection that has caused a global pandemic - overwhelming hospitals and healthcare systems across the world, diseases like Zika virus, West Nile and chikungunya took different parts of the world by surprise and have accounted for several fatalities. In India alone, mosquito-borne diseases accounted for 24,000 deaths in 2015, while as many as 435,000 deaths were reported in 2017 due from malaria in the country, according to data from the World Health Organization (WHO).

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Researchers at the NIAID, led by Dr. Jessica Manning, have come up with the concept of using the peptide in mosquito spit to develop immunity against it. This solution is being touted as a universal vaccine that could be the answer to all vector-borne diseases, whose observations were published in the scientific journal Lancet earlier this month, the first clinical trial of its kind. 

When a mosquito bites a human being, it extracts blood and leaves some of its spit in the person’s blood system, containing the peptides which may have the presence of the disease. 

Vector-borne diseases mean the pathogen relies on a vector - in this case a mosquito which doesn't cause the disease itself - to carry the pathogen from one host to infect another. 

For decades, researchers have known the dangers mosquitoes posed to humanity as carriers of disease, but only recently started manipulating it in vaccinations. All the current vaccinations in place attempt to attack the pathogen to lessen or remove the impact of the infection on one’s immune system.

  1. Encouraging results from Phase I of vaccine trial

This new study, however, looks to attack the vector, as mosquito spit is the source for many deadly diseases. Individual vaccines for infections such as malaria exist, but the NIAID is attempting to create a vaccine that would target all mosquito-borne diseases. 

There are currently two vector-based vaccines on the market, both of which are to control cattle tick. The difficulty that arises with vector-based vaccines is the ever-evolving relationship between the vector and vertebrae host. Any action the vertebrae host makes to react to the introduction of the saliva of the vector is counteracted by the proteins and peptides found in the saliva of the vector. 

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Phase I of the trial included 49 patients, a third of whom received a placebo while another third received the AGS-v and the adjuvant (a substance given along with an antigen to produce antibodies), and the final third received the AGS-v without the adjuvant. After receiving doses on Day 0 and 21, patients were exposed to feeding by an uninfected Aedes aegypti mosquito on day 42. 

Immunogenicity (provoking an immune response from the human body) occurred in 33 of the 49 patients who had been exposed to the pathogens and peptides from the Aedes aegypti mosquito. The most severe reaction to the combination of the vaccine and the mosquito was a grade 3 rash (8 cm) near the injection site of one patient who received the adjuvant. 

The 17 patients who received the adjuvant by day 42 had significantly higher levels of immunoglobulin (IgG) antibodies than those with only the AGS-v vaccine. 

This study shows that vector-targeted vaccines have the potential to become a mainstream way of protecting against the increasing burden of vector-borne diseases. At the same time, the batch this trial was tested on is too small to validate such an important vaccine. 

The vaccine created for this study takes the approach of introducing patients to the amino acid peptide structure in the spit, which prevents them from getting infected by it. However, it leaves them susceptible to contracting diseases from other kinds of mosquitoes that aren’t closely related. 

The current method of antipathogen in combination with the vaccination technology being developed by the NIAID is a much safer approach to vaccination. For the time being, keeping up to date for vaccinations of malaria, yellow fever and dengue as we await the vector-borne vaccines to reach a point where it can be safely rolled out to the public.

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