An antigen-detection assay to diagnose Babesia microti infection

Project Summary
Human babesiosis is a malaria like multisystem disease caused primarily by Babesia microtian emerging
apicomplexan parasite that infects and develops within human erythrocytesThe parasite is transmitted to
humans by the tick vector Ixodes scapularis and can also be introduced through blood transfusionInfection can
cause flu like symptomsand severe infection can be fatalin particular in the immunosuppressed and the elderlyCurrent methods for babesiosis diagnosis include microscopyPCRIFA and ELISA based methods that detect
antibodies in serum from patients or donorsEach of these methods has major limitationsPCR detection of the
parasite DNA is the most sensitive of all current diagnostic methods usedHoweverPCR only tests for the
presence of parasites within a fraction of a sample being testedtypicallyml out ofmlThusat very low
parasitemiasa false negative result is possible when the test sample happens to be devoid of infected red blood
cellsIn sumcurrent screening criteria reduce the probability of blood contamination but do not completely
eliminate the risk of transmission by transfusion to individuals with a weakened immune systemHere we
propose to develop a capture ELISA assay that can detect the most highly expressed and immunogenic antigen
of the parasiteBmGPIBmSAOur preliminary studies using short term in vitro culture as well as controlled
mouse infections demonstrated that a capture assay targeting this antigen detects infection before the parasite
is detectable by microscopy or PCRwith parasitemia levels lower thanBecause each infected cell
releases thousands of BmGPIBmSAmolecules into the serumwe expect that our antigen detection assay
will prove more sensitive than any method detecting the parasite itselfincluding PCRBuilding upon our
preliminary datawe propose the following two specific aims towards the development of a test that could be
implemented for high throughput detection of Bmicroti in blood donationsIn Aimwe will optimize the assay
procedure using a set of well characterized blood and sera from infected and non infected laboratory miceTo
achieve regulatory standards of reproducibility in a commercial assaywe will develop monoclonal antibodies
against BmGPIBmSAto replace the polyclonal serum used in preliminary experimentsIn Aimwe will
use the optimized assay to screen a collection ofhuman serum samples available at Yale University and LDiagnosticsThese samples have previously been characterized by Bmicroti PCR detection and serologyOur
experiments will provide proof of feasibility needed for future efforts and collaborations with major blood
organizations to use the assay in large scale blood screeningThe success of the proposed studies will set the
stage for use of this assay to screen the blood supply to prevent transfusion transmitted babesiosis PROJECT NARRATIVEHuman babesiosisa potentially fatal malaria like disease reported worldwide and endemic in the United Statesis caused by Babesia microtia parasite that is transmitted by ticks or by blood transfusionThe parasite is the
leading cause of transfusion transmitted diseases in the United StatesThis proposal aims to develop an assay
that can detect the most highly expressed and secreted antigen of the parasite in infected individuals at levels
below those detected by the current gold standard techniques