Editorial: Immune Responses to Persistent or Recurrent Antigens: Implications for Immunological Memory and Immunotherapy

Linked empirical studies reveal the cumulative impact of acquired tick resistance across the tick life cycle

Host defenses affect tick feeding success, and thus survival and reproduction, but defensive traits have rarely been studied relative to tick population dynamics. We explored the effects of anti-tick resistance of three natural hosts against Dermacentor andersoni, the Rocky Mountain wood tick. Larval ticks were fed on Deer mice (Peromyscus maniculatus) and Cottontail rabbits (Sylvilagus nuttallii), and nymph and adult ticks were fed on cattle (Bos taurus). We compared feeding success and fecundity of ticks fed on naïve (never infested by ticks) or exposed (one prior tick infestation) hosts. We used these measures to parameterize simulations of D. andersoni population growth in a discrete time, geometric population model to understand the population-level consequences of anti-tick resistance. Prior infestation triggered tick resistance in all three host species and impacted all tick life stages. On tick-exposed hosts, an average of 23 % fewer ticks reached adulthood and adult females produced 32 % fewer larvae. Modest effects of tick resistance at each life stage had strong cumulative effects across the tick life cycle. Simulated tick population dynamics revealed that mean population growth (λ) is reduced 68 % when the life cycle is completed on hosts with prior tick exposure. Simulated populations feeding on exposed hosts were more likely to decline (λ<1) under conditions of low off-host survival and host-finding. This suggests acquired tick resistance may interact with environmental conditions and host availability to affect tick population dynamics. These data shed new light on naturally occurring biotic factors that may affect tick abundance and tick-borne pathogen transmission.

Unresolved inflammation during hospitalization is associated with post-discharge institutionalization and mortality in geriatric rehabilitation inpatients: The RESORT cohort

BACKGROUND

Inflammation contributes to adverse health outcomes in community-dwelling populations. Little is known about inflammation in hospitalized older adults and its association with adverse outcomes. This study aimed to evaluate the association of the inflammatory markers C-reactive protein (CRP) and albumin measured during acute and geriatric rehabilitation hospitalization with institutionalization and mortality in geriatric rehabilitation inpatients.

METHODS

Within the REStORing health of acutely unwell adulTs (RESORT) cohort, CRP and albumin were measured as part of usual care during acute and geriatric rehabilitation hospitalization. Inflammatory markers are presented as median, peak (CRP: maximum; albumin: minimum), variation (interquartile range) and direction of change (increased CRP or decreased albumin: positive or negative difference between last measurement and median of preceding measurements). Logistic regression was used to determine the associations between inflammatory markers and institutionalization at three-month and all-cause mortality at three- and twelve-month post-discharge.

RESULTS

Geriatric rehabilitation inpatients (n = 1846) with a median age of 83.3 years (interquartile range 77.6-88.3) and 56.6% of female were included. Increased CRP during geriatric rehabilitation was associated with institutionalization. Higher median, peak and increased levels of CRP during geriatric rehabilitation but not during acute hospitalization were associated with higher mortality. Lower CRP variation during acute hospitalization but higher CRP variation during geriatric rehabilitation was associated with higher mortality. Lower median level of albumin during both hospitalizations were associated with higher mortality.

CONCLUSIONS

Inflammation characterized by lower albumin during acute hospitalization and, higher CRP and lower albumin during geriatric rehabilitation was associated with mortality in geriatric rehabilitation inpatients. Increased CRP during geriatric rehabilitation was associated with institutionalization. Unresolved inflammation in geriatric rehabilitation might indicate ongoing disease activity leading to adverse outcomes.