Molecular analysis of adenovirus isolates from vaccinated and unvaccinated young adults

Area of Science:

• Virology
• Molecular Biology
• Epidemiology

Background:

• Adenovirus type 4 (Ad4) and Ad7 infections have been observed in military recruit populations.
• Previous vaccination campaigns aimed to prevent adenovirus infections in these settings.

Purpose of the Study:

• To genetically characterize adenovirus isolates from vaccinated and unvaccinated individuals.
• To compare the phylogenetic distribution of adenovirus strains in vaccinated versus unvaccinated populations.
• To identify the predominant adenovirus strains circulating in military recruit camps.

Main Methods:

• Febrile respiratory illness surveillance in military recruit camps.
• Genetic sequencing of the hexon gene from adenovirus isolates.
• Phylogenetic analysis and comparison with reference strains from GenBank.

Main Results:

• Adenovirus isolates from vaccinated individuals showed phylogenetic similarity to those from unvaccinated individuals.
• The most common Ad7 strain was the Ad7d2 hexon genotype.
• A recently discovered Ad4 variant (nearly identical to Z-G 95-873) has been predominantly isolated since 1999, causing most adenovirus morbidity in recruit camps.
• Analysis of substitution rates indicated positive selection in antigenic regions and purifying selection in nonantigenic regions of the hexon gene.

Conclusions:

• Adenovirus strains circulating in vaccinated military recruits are phylogenetically similar to those in unvaccinated individuals.
• A specific Ad4 variant is the primary cause of adenovirus illness in current military recruit populations.
• Evidence of selection pressures on adenovirus hexon gene regions suggests adaptation and immune evasion strategies.