Extensive Genotypic Diversity in the Live Sporozoite
East Coast Fever (ITM) vaccine
Ekta Patel1, Donald Lubembe2,3, James Gachanja1, Stephen Mwaura1, Paul Spooner1, Philip Toye1
1International Livestock Research Institute (ILRI), Nairobi, Kenya; 2University of Nairobi; 3BecA-Hub at ILRI, Nairobi
Summary Outputs
To understand the composition of ITM five mini- and micro- satellite markers were
ITM, •Establish quality control protocols to detect variations in the stabilates produced over
Establish
used to genotype the vaccine and reference stabilates including over 200 cloned cell time.
lines using a high-throughput capillary electrophoresis system. •Understanding the vaccine composition will assist us in identifying possible
breakthrough strains in the field.
Results indicate that the stabilate contains at least 14 different T. parva genotypes •Improve our understanding of the complexity involved in possibly generating a sub-unit
and is more complex that previously reported. vaccine by assessing the cloned cell lines for antigenic diversity of parasites in the vaccine.
Introduction Results
East Coast fever is a fatal bovine disease caused by Theileria parva and is transmitted by
Genotypes ms9 MS7 MS19 MS25 MS39 ILRI 08 FAO 1
the brown ear tick, Rhipicephalus appendiculatus. Over 1 million cattle die per year with an
additional 28 million cattle at risk of contracting the disease. Economic losses exceed Muguga
over $300M per year (Ndegwa, 2005). The disease is found in approximately 11 countries
1 a a a a a 15 (29%) 13 (33%)
in central, eastern and southern Africa. Models to predict the impact of climate change
on tick distribution and tick-borne disease suggest that the number of cattle at risk of 2 a b b a a 13 (25%) 6 (15%)
contracting ECF will increase (Olwoch et al., 2008).
3a a a b a a 7 (13%) 8 (21%)
The current vaccine against East Coast fever, called Infection and Treatment Method 4 a b a a a 7 (13%) 3 (8%)
(ITM) involves immunizing cattle with live T. parva sporozoites and simultaneously
5b a a b b a 3 (6%)
( ) 2 (5%)
( )
administering a dose of oxytetracycline. ITM comprises three T p
d i it i d f t t li i th T. parva stock components,
t k t
namely, Muguga, Serengeti-transformed and Kiambu 5 making this a complex 6 a b b b a 3 (6%) 3 (8%)
composition. In this worrying scenario, the need to have a continued supply of a vaccine
7 a a a b a 2 (4%) 2 (5%)
whose composition is consistent from batch to batch. The current study aimed to address
this by determining the composition of reference stabilates from two vaccine batches 8 a b a b a 2 (4%) 2 (5%)
made 12 years apart from the same seed stabilate by genotyping cloned cell lines derived
52 39
from them.
Serengeti-transformed
Methods 1b a a b b a 30 (45%) 1 (25%)
Parasite material was obtained from vaccine and reference stabilates and from cell lines 2a a a b a a 28 (
(42%)
) 3(
(75%)
)
obtained by in vitro infection and cloning of lymphocytes (Goddeeris and Morrison 3 b c b c b 3 (4%)
1988). Single clones were genotyped using five mini and microsatellite markers, MS7,
ms9, MS19, MS39 and MS 25 which have been previously described (Oura et al., 2003). 4 a a b c a 2 (3%)
PCR amplified products obtained with fluorescently labeled primers from whole cells or 5 a a c b a 1 (1.5%)
purified DNA were analyzed on a high-throughput capillary electrophoresis system.
Typical histograms are shown below. 6 b c c b b 1 (1.5%)
7 b c c a b 1 (1.5%)
Muguga
g g 8c b c c c b 1 (1.5%)
67 4
Kiambu 5
1c b c c c b 52 (100%) 10 (100%)
Serengeti-transformed
a ,b, c Genotypes which are identical are indicated with the same superscript.
Kiambu 5 Discussion
It is important that the antigenic heterogeneity is maintained in the vaccine, and this
can only be achieved through knowledge of the vaccine composition produced in
successive batches and compared to previous batches. With at least 14 genotypes of T.
References
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