April 2010

The good news is …

Kimani,  a  Maasai  in  Tanzania,  says  that  ITM  provided  security  for  his  family  by  increasing  his  cows  from  200  to  almost  600  while  ILRI  has  just  produced  more  ITM  with  GALVmed  support.  

And the not so good news is …

Infection and Treatment Method (ITM) The vaccine in use to control ECF

ITM  is  sGll  not  widely  adopted  and  immunizaGon  cost  is  high:  7-­‐14$  per  animal.  

Pelle R., Patel E. and Toye P.!

Abstract  The tick-borne protozoan parasite Theileria parva causes an acute, often fatal disease in cattle

known as East Coast fever (ECF)  The disease is endemic in 11 countries in eastern and southern Africa and kills one million cattle

annually  The disease has a particularly devastating impact on poor small-holder farmers and increasingly

used imported breeds of cattle are highly susceptible  Infection and treatment method (ITM) vaccine is currently used to protect animals against ECF but

poor small-holder farmers often do not have access to it  The ITM vaccine, also known as the Muguga Cocktail contains three stocks, namely, Muguga,

Kiambu 5 and Serengeti-transformed, isolated over 30 years ago  Evidence indicates that CD8 T lymphocytes specific for parasitized cells play a central role in the

protective immunity and recently, 10 antigens recognised by parasite-specific CD8 T cells have been identified

 Genotyping the protective parasites and defining the antigenic composition of the vaccine will help understanding the genetic diversity in the ITM vaccine vis-à-vis the field populations of T. parva

 Using 5 DNA markers, we have genotyped 12 different parasites with 5 epitope variants at 3 antigenic loci in the ITM vaccine.

Genotyping  of  100  sporozoite  clones  from  the  T.  parva  Muguga,  Serenge:  transformed  and  Kiambu  5  isolates  of  the  Muguga  cocktail  vaccine  

VNTR  markers  used   12  T.  parva  genotypes  found  in  the  Muguga  cocktail  vaccine  

           MS7,  ms9,              MS19,  MS25              and  MS39  

1.    A      A      A      A      A   5.    A      A      C      A      B   9.        C      C      C      C      A  2.    A      A      A      A      B   6.    B      A      A      A      A   10.    C      C      C      C      B  3.    A      A      B      A      A   7.    B      A      A      A      B   11.    C      C      A      C      C  4.    A      A      A      A      C   8.    C      C      C      C        C   12.    C      B      C      C      C  

Func:onal  characteriza:on  of  the  Muguga  cocktail  vaccine  CD8  T  cell  an:gens   5  CTL  target  epitope  variants  found  in  3  an:gens  of  the  ITM   Tp1 VGYPKVKEEML Tp2.1 SHEELKKLGML SDEELNKLGML Tp9 AKFPGMKKSK EKFKHMGIGK

Why characterize ITM?  To monitor stabilate production and variability, genetic

composition of T. parva immunization stabilates, and batch quality control that would facilitate registration in different countries

 To monitor origin of persistent infections in vaccinated cattle and recombination of vaccine parasite strains with field parasite populations

 To understand how the vaccine works and investigate presumed vaccine breakdown and breakthrough

 To monitor transmission dynamics and parasite population genetics that sustained use of live vaccination may cause

 To detect super-infections in vaccinated animals: ITM protects against the disease but does not prevent super-infection