Key Determinants of Cell-Mediated Immune Responses: A Randomized Trial of High Dose Vs. Standard Dose Split-Virus Influenza Vaccine in Older Adults

Markers of systemic inflammation are positively associated with influenza vaccine antibody responses with a possible role for ILT2(+)CD57(+) NK-cells

Background

With increasing age, overall health declines while systemic levels of inflammatory mediators tend to increase. Although the underlying mechanisms are poorly understood, there is a wealth of data suggesting that this so-called “inflammaging” contributes to the risk of adverse outcomes in older adults. We sought to determine whether markers of systemic inflammation were associated with antibody responses to the seasonal influenza vaccine.

Results

Over four seasons, hemagglutination inhibition antibody titres and ex vivo bulk peripheral blood mononuclear cell (PBMC) responses to live influenza viruses assessed via interferon (IFN)-γ/interleukin (IL)-10 production, were measured pre- and 4-weeks post-vaccination in young adults (n = 79) and older adults randomized to standard- or high-dose inactivated vaccine (n = 612). Circulating tumour necrosis factor (TNF), interleukin (IL)-6 and C-reactive protein (CRP) were also measured pre-vaccination. Post-vaccination antibody titres were significantly associated with systemic inflammatory levels; specifically, IL-6 was positively associated with A/H3N2 titres in young adults (Cohen’s d = 0.36), and in older high-dose, but not standard-dose recipients, all systemic inflammatory mediators were positively associated with A/H1N1, A/H3N2 and B titres (d = 0.10–0.45). We further show that the frequency of ILT2(+)CD57(+) CD56-Dim natural killer (NK)-cells was positively associated with both plasma IL-6 and post-vaccination A/H3N2 titres in a follow-up cohort of older high-dose recipients (n = 63). Pathway analysis suggested that ILT2(+)CD57(+) Dim NK-cells mediated 40% of the association between IL-6 and A/H3N2 titres, which may be related to underlying participant frailty.

Conclusions

In summary, our data suggest a complex relationship amongst influenza vaccine responses, systemic inflammation and NK-cell phenotype in older adults, which depends heavily on age, vaccine dose and possibly overall health status. While our results suggest that “inflammaging” may increase vaccine immunogenicity in older adults, it is yet to be determined whether this enhancement contributes to improved protection against influenza disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12979-022-00284-x.

Advanced biological age is associated with improved antibody responses in older high-dose influenza vaccine recipients over four consecutive seasons

Background

Biological aging represents a loss of integrity and functionality of physiological systems over time. While associated with an enhanced risk of adverse outcomes such as hospitalization, disability and death following infection, its role in perceived age-related declines in vaccine responses has yet to be fully elucidated. Using data and biosamples from a 4-year clinical trial comparing immune responses of standard- and high-dose influenza vaccination, we quantified biological age (BA) prior to vaccination in adults over 65 years old (n = 292) using a panel of ten serological biomarkers (albumin, alanine aminotransferase, creatinine, ferritin, free thyroxine, cholesterol, high-density lipoprotein, triglycerides, tumour necrosis factor, interleukin-6) as implemented in the BioAge R package. Hemagglutination inhibition antibody titres against influenza A/H1N1, A/H3N2 and B were quantified prior to vaccination and 4-, 10- and 20- weeks post-vaccination.

Results

Counter to our hypothesis, advanced BA was associated with improved post-vaccination antibody titres against the different viral types and subtypes. However, this was dependent on both vaccine dose and CMV serostatus, as associations were only apparent for high-dose recipients (d = 0.16–0.26), and were largely diminished for CMV positive high-dose recipients.

Conclusions

These findings emphasize two important points: first, the loss of physiological integrity related to biological aging may not be a ubiquitous driver of immune decline in older adults; and second, latent factors such as CMV infection (prevalent in up to 90% of older adults worldwide) may contribute to the heterogeneity in vaccine responses of older adults more than previously thought.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12979-022-00296-7.

Granzyme B: a double-edged sword in the response to influenza infection in vaccinated older adults

Background

Influenza-specific cytolytic T lymphocytes (CTL) have a critical role in clearing the virus from the lungs, but are poorly stimulated by current inactivated influenza vaccines. Our previous work suggests that granzyme B (GrB) activity predicts protection against laboratory-confirmed influenza infection (LCII) in older adults. However, basal GrB (bGrB) activity increases with age and the frequency of GrB+ CTL that do not co-express perforin increases following influenza infection, thereby acting as a potential contributor to immune pathology.

Objectives

Using data from a 4-year randomized trial of standard- versus high-dose influenza vaccination, we sought to determine whether measurements of GrB activity alone indicate a protective vs. pathologic response to influenza infection. We compared LCII to No-LCII subsets according to: pre-vaccination bGrB activity; and induced GrB activity in ex vivo influenza-challenged peripheral blood mononuclear cells (PBMC) at 4- and 20-weeks post-vaccination.

Results

Over four influenza seasons (2014-2018), 27 of 608 adult participants aged 65 years and older developed influenza A/H3N2-LCII (n=18) or B-LCII (n=9). Pre-vaccination, there was a significant correlation between bGrB and ex vivo GrB activity in each of the H3N2-LCII, B-LCII, and No-LCII subsets. Although pre-vaccination ex vivo GrB activity was significantly higher in B-LCII vs. No-LCII with a trend for H3N2-LCII vs. No-LCII, there was no difference in the response to vaccination. In contrast, there was a trend toward increased pre-vaccination bGrB activity and LCII: Odds Ratio (OR) (95% confidence intervals) OR = 1.46 (0.94, 2.33). By 20-weeks post-vaccination, there were significant fold-increases in ex vivo GrB activity specific for the infecting subtype in H3N2-LCII: OR = 1.63 (1.35, 2.00) and B-LCII: OR = 1.73 (1.34, 2.23).

Conclusions

Our results suggest that the poor GrB responses to influenza vaccination that led to development of LCII can be attributed to inactivated formulations rather than the aging immune system since LCII cases generated robust ex vivo GrB responses following natural infection. Further, we identified bGrB as a biomarker of those who remain at risk for LCII following vaccination. Future studies will focus on understanding the mechanisms responsible for the shift in GrB-mediated protection vs. potential immune pathology caused by GrB release.