The acute phase response in bats (Carollia perspicillata) varies with time and dose of the immune challenge

Abstract

The acute phase response (APR) is a core component of the innate immune response and represents the first line of immune defense used in response to infections. Although several studies with vertebrates reported fever, decrease in food intake and body mass, as well as increase in neutrophil/lymphocyte ratio and total white blood cell count after lipopolysaccharide (LPS) inoculation, there was great variability in the magnitude of these responses. Some of these differences might reflect, to some extent, differences in time of endotoxin inoculation (during activity or resting periods) and dose. Therefore, our study tested the interplay between LPS dose and time of injection on selected physiological (fever and increase in total white blood cell count and neutrophil/lymphocyte ratio), and behavioral (food intake) components of APR using a Neotropical fruit-eating bat (Carollia perspicillata) as a model organism. We predicted that LPS would trigger a dose- and time-dependent response on APR components. APR components were assessed in resting and activity periods after injection of three doses of LPS (5, 10 and 15 mg/kg LPS). The results indicate a more robust decrease in food intake at higher doses during activity period, while increased neutrophil/lymphocyte ratio was more robust during activity period regardless of dose. Furthermore, skin temperature increase lasts longer at higher doses regardless period of injections. Our study offers important insights into the dependence of time as well as the LPS dosage effect in the APR of bats, and how they deal with the magnitude of infections at different time of day.

Combined effects of ambient temperature and food availability on induced innate immune response of a fruit-eating bat (Carollia perspicillata)

“…Moreover, LPS modulates other immunological functions such as bacterial killing ability of plasma, that represents the antimicrobial activity of humoral proteins of the innate immune system [42]. Recent reviews suggested that bats respond selectively to LPS administration, with species-specific differences in the activation of different components of this response [43,44]. Few studies have analyzed how APR is affected by changes in external factors directly related to global changes.…”

“…In this way, we conducted 8 experimental trials on the climatic chamber with 8 individuals at a time, and the bats were assigned to only one thermal-feeding treatments. We decided to inject 10 mg LPS/kg in the nighttime because a recent work with C. perspicillata showed that higher doses of LPS in the activity period elicit a robust response in some components of the APR, such as reduced food intake and increased N/L ratio [44]. Selected ambient temperatures during the experiments were set close to the lower (27˚C) and upper limits (33˚C) of the thermoneutral zone of C. perspicillata (27-35˚C) [47].…”

“…We collected *10 μl of blood from the propatagial vein 24 hours before and 24 hours after injections at around 06:00 pm and prepared two blood smears to estimate total white blood cell count and the neutrophil /lymphocyte ratio changes following Viola et al [44]. Total and differential white blood cell count in blood smears is the most common method used in bat studies that evaluate the acute phase response after LPS immune challenge [43,44,46,[52][53][54][55].…”

“…We collected *10 μl of blood from the propatagial vein 24 hours before and 24 hours after injections at around 06:00 pm and prepared two blood smears to estimate total white blood cell count and the neutrophil /lymphocyte ratio changes following Viola et al [44]. Total and differential white blood cell count in blood smears is the most common method used in bat studies that evaluate the acute phase response after LPS immune challenge [43,44,46,[52][53][54][55]. We assessed changes in total white blood cell count (WBC) and the neutrophil/lymphocyte ratio (N/L) after LPS immune challenge in relative terms as: ΔWBC = (WBC 24 hours after injection − WBC 24 hours before injection) / (WBC 24 hours before injection); and ΔN/L = (N/L 24 hours after injection − N/L 24 hours before injection) / (N/L 24 hours before injection).…”

COMBINED EFFECTS OF AMBIENT TEMPERATURE AND FOOD AVAILABILITY ON INDUCED INNATE IMMUNE RESPONSE OF A FRUIT-EATING BAT (CAROLLIA PERSPICILLATA)

“…Moreover, LPS modulates other immunological functions such as bacterial killing ability of plasma (BKA), that represents the antimicrobial activity of humoral proteins of the innate immune system [41]. In bats, recent reviews suggested that bats respond selectively to LPS administration, with species-specific differences in the activation of different components of this response [42,43]. Few studies have analyzed how APR is affected by changes in external factors directly related to global changes.…”