DNA Vaccine Is Immunogenic But Falls Short of Full Protection.(Brief Article)

2001 JUN 20 - (NewsRx.com & NewsRx.net) --

by N.R. Saltmarsh, staff medical writer - A DNA vaccine consisting of Plasmodium yoelii heat shock protein 60 (PyHsp60) offers enough protection against the sporozoite in mice to warrant further investigation, but cannot currently be considered reliable, say researchers at the U.S. Naval Medical Research Center, Johns Hopkins University, and the University of Maryland.

G.I. Sanchez and associates cloned PyHsp60 into VR1012 and VR1020 mammalian expression vectors. They vaccinated mice intramuscularly at zero, three and nine weeks with 100 (micro)g of PyHsp60 alone or combined with 30 (micro)g of pmur granulocyte-macrophage colony-stimulating factor (GM-CSF).

In vitro experiments with sera from immunized mice, but not from controls, showed recognition of P. yoelii sporozoites, liver stages, and infected erythrocytes. Nevertheless, when mice were challenged two weeks later with P. yoelii, the pPyHsp60-VR1012 plus pmurGM-CSF vaccine conferred only 40% protection, as determined by Fisher's exact test. In a second experiment, the vaccine offered no protection but did delay progression to parasitemia, said Sanchez and colleagues.

The researchers reported that neither experiment showed protection against the asexual erythrocytic stage of P. yoelii's life cycle. Nor did PyHsp60 DNA limit blood-stage infection or parasite development in hepatocytes when used to ...