A human Phase I/IIa malaria challenge trial of a polyprotein malaria vaccine.
Porter DW., Thompson FM., Berthoud TK., Hutchings CL., Andrews L., Biswas S., Poulton I., Prieur E., Correa S., Rowland R., Lang T., Williams J., Gilbert SC., Sinden RE., Todryk S., Hill AVS.
We examined the safety, immunogenicity and efficacy of a prime-boost vaccination regime involving two poxvirus malaria subunit vaccines, FP9-PP and MVA-PP, expressing the same polyprotein consisting of six pre-erythrocytic antigens from Plasmodium falciparum. Following safety assessment of single doses, 15 volunteers received a heterologous prime-boost vaccination regime and underwent malaria sporozoite challenge. The vaccines were safe but interferon-γ ELISPOT responses were low compared to other poxvirus vectors, despite targeting multiple antigens. There was no vaccine efficacy as measured by delay in time to parasitaemia. A number of possible explanations are discussed, including the very large insert size of the polyprotein transgene.