Vaccine strategies to enhance immune responses in the aged

Abstract

The elderly population is more susceptible to infections with higher risks of morbidity and mortality. This is caused by the accumulation of immune defects with aging. The best way to protect people against infections is vaccination. Unfortunately, the same immune defects that render the elderly susceptible to infectious diseases also prevent the development of protective immunity following immunization. A good example of this is the influenza vaccine that only protects between 40 and 60% of the vaccinees over 65 years. In the past decade, tremendous efforts have been put toward improving the influenza vaccine for the elderly. We therefore use this example to present various strategies employed to overcome these age-associated immune defects and hence make vaccines more efficacious for the aged.

Figure 1. Adjuvants can enhance the response to vaccination in aged mice

Young (2–4 month) and aged (20–24 months) B10. Br mice were vaccinated with 200 ug nitrophenyl conjugated to pigeon cytochrome c (NP-PCC) in alum alone, alum with proinflammatory (PI) cytokines TNFα, IL-1 and IL-6, poly (I:C) or CpG oligonucleotides. On day 14, the number (mean +/− SD) of NP-specific B cells (left graph) and the number of germinal center (PNA^hiCD38^lo) NP-specific B cells (right graph) was determined by flow cytometry. The only significant difference between young and aged cell numbers was observed when alum alone was used as an adjuvant. *p<0.05 by Student’s t test.