A single vaccine may not help in the control of malaria and this major health nuisance has to be tackled through specific vaccines for different strains of malarial parasite

By Syed Akbar
Hyderabad: A single vaccine may not help in the control of malaria
and this major health nuisance has to be tackled through specific vaccines
for different strains of malarial parasite.
A study by the city-based Centre for Cellular and Molecular Biology and the
National Institute for Malaria Research revealed that different vaccines need
to be developed to prevent different isolates of Plasmodium falciparum, the
causative agent of malaria.
"The C-terminal region of merozoite surface protein-1 is one of the leading
candidates for vaccination against the erythrocytic stages of malaria.
However, a major concern in the development of MSP-1 based malaria
vaccine is the polymorphism observed in different geographical Plasmodium
falciparum isolates," the study points out.
The results from the study also revealed predominance of a particular type of
allele among Indian field isolates. Seven such variant forms were isolated in
a singe geographical location. This simply means there should be seven
different vaccines each targeting a particular isolate, in the Indian
context.
The study demonstrated the existence of allele specific antibodies in
Plasmodium falciparum-infected patient sera. The scientists suggested the
importance of a multi-allelic based vaccine for an effective malaria
control in the country.
Malaria is one of the major causes of death from infection in India as in
other developing countries.  Development of an effective malaria vaccine may
reduce malaria-associated severe morbidity and mortality in malaria-endemic
areas.
A number of parasite surface antigens of asexual blood stages are being
investigated as vaccine candidate antigens. Among these antigens, merozoite
surface protein-1 is a leading candidate antigen.
"A substantial proportion of antibodies directed to MSP-119 in Plasmodium
falciparum-infected human sera have been shown to inhibit erythrocyte
invasion in vitro. Sequence comparison of Plasmodium falciparum msp1
sequences among different geographical isolates shows a great deal of
variations," the study said.
Malaria transmission is perennial in the country but is markedly low in the
plain area than forest area. Plasmodium falciparum accounted for 85 per cent
of total malaria cases during the study period. In forest and plain areas,
the number of falciparum cases per thousand populations were 284.1 and 31.2
respectively, whereas the parasite rate was 14 per cent and 1.7 per cent
respectively.
In forest areas, clinical malaria occurred more frequently in children
aged 0-5 years and declined gradually with increasing age.