Plasmodium vivax causes approximately 100 million cases of clinical malaria each year and many more cases of asymptomatic parasitemia. Although not as virulent as P. falciparum, P. vivax nonetheless causes chronic anemia during infancy and life-threatening morbidities, including severe anemia, respiratory distress, renal failure and splenic rupture. After release from hepatocytes, merozoites only infect reticulocytes that in culture rapidly mature to erythrocytes, which limits in vitro culture and laboratory research. Unfortunately current vaccine candidates do not induce strong immunity in non-human primates. New insights are needed to develop an effective vaccine against P. vivax malaria. Previously immunological control of blood stage infection was thought to depend primarily on antibodies rather than on T cells, because mature red blood cells do not express HLA class I. Because reticulocytes, unlike mature erythrocytes, retain RNA and a high capacity for protein expression, we hypothesized that infected reticulocytes might act as antigen-presenting cells and targets for CD8+ T lymphocytes during malaria. Indeed, our preliminary studies, using samples from an endemic area of Amazonia, indicate a high frequency of HLA class I+ reticulocytes circulating in P. vivax-infected patients and a high proportion of activated circulating CD8+ T cells, which, when co-cultured with infected reticulocytes, form an immune synapse, secrete IFN?, release their cytotoxic granules and kill. Thus we hypothesize that CD8+ T cells recognize infected reticulocytes and that CD8 T cell immunity is an unappreciated, but important, component of P. vivax immunity. To test this hypothesis, in Aim 1 we will investigate whether infected reticulocytes present parasite antigens bound to HLA class I that are recognized by P. vivax-specific CD8+ T lymphocytes from malaria patients.
In Aim 2 we will determine whether P. vivax-specific CD8+ T lymphocytes recognize and lyse infected reticulocytes by cytotoxic granule exocytosis and also kill intracellular parasites in a granulysin-dependent manner.
The aim of these experiments is to confirm the preliminary data and begin to define how infected reticulocytes are recognized and destroyed by cytotoxic killer T cells. These data should open a new perspective for development of P. vivax malaria vaccines.

Public Health Relevance

Immunization is one of the most successful and cost-effective health interventions, which prevents millions of deaths every year. However, our knowledge of the mechanisms involved in P. vivax protective immunity is still limited and an effective vaccine is not available. We aim to investigate a novel role for cytotoxic CD8+ T lymphocytes in blood- stage P. vivax malaria immunity, in the hopes of providing new insights for developing an effective vaccine that could contribute to the global effort to eliminate malaria.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21AI131632-01A1
Application #
9453542
Study Section
Immunity and Host Defense (IHD)
Program Officer
Pesce, John T
Project Start
2018-01-09
Project End
2019-12-31
Budget Start
2018-01-09
Budget End
2018-12-31
Support Year
1
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of Massachusetts Medical School Worcester
Department
Type
Overall Medical
DUNS #
603847393
City
Worcester
State
MA
Country
United States
Zip Code
Junqueira, Caroline; Barbosa, Camila R R; Costa, Pedro A C et al. (2018) Cytotoxic CD8+ T cells recognize and kill Plasmodium vivax-infected reticulocytes. Nat Med 24:1330-1336
Galvão-Filho, Bruno; de Castro, Júlia Teixeira; Figueiredo, Maria Marta et al. (2018) The emergence of pathogenic TNF/iNOS producing dendritic cells (Tip-DCs) in a malaria model of acute respiratory distress syndrome (ARDS) is dependent on CCR4. Mucosal Immunol :
Hirako, Isabella Cristina; Assis, Patrícia Aparecida; Hojo-Souza, Natália Satchiko et al. (2018) Daily Rhythms of TNF? Expression and Food Intake Regulate Synchrony of Plasmodium Stages with the Host Circadian Cycle. Cell Host Microbe 23:796-808.e6