Cellular immune responses in peripheral blood lymphocytes of Giardia infected squirrel monkey (Saimiri boliviensis boliviensis) treated with Fenbendazole.

Pramod N Nehete,Sriram Chitta,Lawrence E Williams,Bharti P Nehete,John A Vanchiere,Gregory Wilkerson,Henrieta Scholtzova,Julio C Ruiz,Christian R Abee,Isabelle Chemin

doi:10.1371/journal.pone.0198497

Abstract

Cellular immune responses were tested to determine the effect of fenbendazole on the function of lymphocytes from Bolivian squirrel monkeys (Samiri boliviensis boliviensis). Giardia-infected squirrel monkeys were treated with commercially available fenbendazole (FBZ)-medicated monkey chow. Immune responses were compared between historical controls (Giardia naïve, untreated with FBZ (control animals)) and Giardia-infected, FBZ-treated squirrel monkeys (study animals). Peripheral blood lymphocytes from study monkeys had significantly lower stimulation indices compared to control animals when cultured in vitro with concanavalin A (Con A) (p<0.0001), phytohaemagglutinin (PHA) (p<0.0001) and lipopolysaccharide (LPS) (p<0.0001). PBMCs were also analyzed for IFN-γ producing cells in response to stimulation with Con A, PHA, PWM, and LPS by the cytokine ELISPOT assay. Significantly higher responses to Con A- (p<0.0001), and PHA- (p<0.001) stimulated cultures from Giardia-infected and fenbendazole treated compared to controls. Flow cytometric analysis for expression of cell surface markers revealed a significant increase in B- and NKT-lymphocytes and significant decrease in CD14+CD16+ monocytes after FBZ treatment. Also, circulating plasma cytokines IFN-γ, TNF-α, IL-12p40, IL-1β, IL-10, IL-13, IL-1ra, IL-6 and IL-4 were significantly decreased after FBZ treatment. Comparison of hematologic parameters between controls and FBZ-treated squirrel monkeys revealed significantly lower numbers of total leukocytes, neutrophils, monocytes, and eosinophils compared to controls. However, erythrocyte indices (red cell count, hemoglobin and hematocrit were significantly higher in FBZ-treated monkeys. Our findings suggest that fenbendazole treatment may alter sensitive immune and molecular measures of inflammation. Postponing the experimental use of squirrel monkeys until at least 6 weeks after FBZ treatment should be considered.

Highlights

The genus Giardia consists of protozoan parasites known to infect a wide range of amphibian, reptilian, avian, and mammalian hosts
The Control group consisted of fifteen untreated Giardia-negative animals (identified as FBZ(-) Giardia(-)) that were 3–5 year old female squirrel monkeys randomly selected from the colony for blood screening in 2015, prior to the identification of Giardiasis in the colony
Study animals included ten female squirrel monkeys, 3–5 years of age that were randomly selected from social groups known to be infected with Giardia (identified as Giardia (+) FBZ (+)

Summary

Introduction

The genus Giardia consists of protozoan parasites known to infect a wide range of amphibian, reptilian, avian, and mammalian hosts. Despite the availability of efficacious antiparasitic drugs, Giardia-infections (Giardiasis) are currently considered to be a re-emerging parasitic disease of humans and some animals. Fenbendazole (FBZ) is a highly efficacious broad-spectrum anthelmintic drug that is used for treatment of numerous helminth and protozoan intestinal parasites including Giardia, of domesticated and laboratory animals [5, 6]. FBZ is effective for treatment of Giardia, lungworms, and flukes, but higher doses are needed for treatment of helminths and failure rates as high as 50% [5]. FBZ typically is administered to laboratory animals species through commercially available FBZ medicated (600 ppm) lab diets to reach a target dose of 8 to 12 ppm daily [6, 9]

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