Generation of Anti-Giardia Antibodies by Bacteriophage Antibody Display

Giardia intestinalis is a protozoan parasite which infects the gastrointestinal tract of man and animals. It is endemic throughout the world and is transmitted via faecal contamination of drinking water and food. Giardia intestinalis has a relatively simple life cycle alternating between the trophozoite (proliferative form) and the cyst (resting form). The nature of symptoms associated with Giardia infections varies between individuals with many cases being asymptomatic, however in symptomatic cases diarrhoea, weight loss, and abdominal cramps are commonly reported [1]. Treatment of Giardia typically involves a number of drugs belonging to the 5 ′ nitroimidazoles. Metronidazole (1-β-hydroxyethyl-2-methyl-5-nitroimidazole ) is the most commonly used as it is generally well tolerated [2]. In most cases Giardia responds well to treatment, however in 1– 4% of cases drug resistance is responsible for treatment failure. Several mechanisms of drug resistance have been investigated in the parasitic protozoa, including drug inactivation via redox cycling and improved drug efflux. Here we describe the use of phage antibody technology to probe the surface of Giardia to identify changes between metronidazole resistant and sensitive trophozoites, and to identify molecules which may confer resistance. We have also used this technology to generate antibodies against Giardia cysts.