In a study conducted on the Malaria vaccine Plasmodium falciparum (Pf) sporozoite (SPZ) [PfSPZ vaccine] to test whether it offers a durable protection against the disease, it was found that the vaccine offered protection for more than 1 year.
The study was published in the journal Nature Medicine on 9 May 2016.
The findings of the study suggested that the PfSPZ Vaccine conferred durable protection to malaria through long-lived tissue-resident T cells and that administration of higher doses may further enhance protection
The study was conducted by researchers at National Institute of Allergy and Infectious Diseases (NIAID), part of the US National Institutes of Health and collaborators at the University Of Maryland School Of Medicine in Baltimore.
The researchers assessed how vaccine dosage, regimen, and route of administration affected durable protection in malaria-naive adults.
After four intravenous immunizations with 2.7 × 105 PfSPZ, 55% non-parasitemic vaccinated subjects remained without parasitemia following controlled human malaria infection (CHMI) 21 weeks after immunization.
• 45% non-parasitemic subjects from this dosage group underwent repeat CHMI at 59 weeks, and none developed parasitemia.
• Although Pf-specific serum antibody levels correlated with protection up to 21–25 weeks after immunization, antibody levels waned substantially by 59 weeks.
• Pf-specific T cell responses also declined in blood by 59 weeks.
• To determine whether T cell responses in blood reflected responses in liver, researchers vaccinated nonhuman primates with PfSPZ Vaccine and found that Pf-specific interferon-g-producing CD8 T cells were present at ~100-fold higher frequencies in liver than in blood.
The result is significant because previous research showed the PfSPZ Vaccine to be highly protective three weeks after immunisation.
About PfSPZ vaccine
• The vaccine was developed and produced by US-based pharmaceutical company Sanaria in 2013.
• It contains thousands of live, but weakened P. falciparum sporozoites, which is the early developmental form of the parasite.