Comparing antibody profiles to upper respiratory tract viruses in elite combat soldiers during training and their support staff

During the first year of combat training, soldiers of elite units are under intense physical and mental stress. To investigate the effect of stress and extensive physical training on the immune system, and the interplay between antibodies to different viruses, we longitudinally profiled antibodies to upper respiratory tract viruses and cytokine profiles in a cohort of IDF elite recruits during and headquarters soldiers from the same base.

We used an antigen microarray spotted with recombinant glycoproteins and inactivated viruses of common upper respiratory tract infections including 54 influenza strains to profile antibodies in serum and saliva samples collected at four timepoints (T1-T4), over a period of 15 months from two groups of soldiers: (1) combat soldiers during their first year of training (recruits; n=51), and (2) support staff from the unit’s headquarters (n=34). In both groups some of the soldiers were vaccinated with the seasonal influenza vaccine a few months before the trial began.

Among the unvaccinated recruits, a significant increase in the magnitude of anti-influenza antibodies at T2 suggested influenza infections in this group. Such increase was not observed in the vaccinated recruits or in support soldiers. We also found that CMV seropositivity was associated with higher levels of IgG antibodies to influenza viruses but lower levels of antibodies to recombinant hemagglutinin (HA) proteins following vaccination.

These findings suggest that recruits are at higher risk of influenza infection which may be prevented by vaccination. Furthermore, CMV infection may affect influenza vaccine-induced antibody repertoire differently for whole viruses and proteins.