Collection of cells to isolate monoclonal antibodies to placental malaria antigens

Placental malaria causes adverse outcomes such as maternal anaemia and poorly grown or premature babies who are at risk of dying in infancy. These adverse outcomes occur most often in first time mothers who lack antibody to the placental binding parasite antigen VAR2CSA. Our recent work highlighted the critical importance of functional antibodies to VAR2CSA in protection from placental malaria . Monoclonal antibodies to VAR2CSA which recognize multiple variants, and which are functional (i.e., elicit parasite clearance by leukocytes and/or inhibit binding) could become effective therapeutics and will be important tools to identify epitopes to be included in improved vaccines. There are only eight human monoclonals to VAR2CSA which have been previously characterized, their sequences are not publicly available, they recognize only two of the six domains which make up the antigen and they do not inhibit the parasite binding the placental receptor. There is a need for more, better (i.e. functional) and publicly available sequences of monoclonal antibodies to VAR2CSA to be used as tools for vaccine development and therapeutics. This application is for funding for the screening of women and collection and initial processing of samples which can be used to sequence and express monoclonals to placental malaria. Due to the volumes of blood required the use of samples collected through other studies is not possible.

To have the best chance to isolate monoclonals, suitable samples are needed. Suitable samples are relatively large volumes of blood from individuals who have strong antibody responses to the antigen of interest. We must first screen pregnant women for antibody responses, to increase the chances of collecting samples containing memory B cells to the antigen of interest. We will collect samples post-partum, to reduce concerns of taking larger volumes (up to 60 mL) from participants while pregnant. Methods: With increasing pregnancy numbers, women acquire higher levels of antibody to VAR2CSA. In collaboration with Investigator Unger, we will enroll up to 100 women in their third or later pregnancy and in their third trimester in malaria-endemic Madang, Papua New Guinea. Women are participants in a trial of intermittent preventive treatment in pregnancy (GNT2000780; AI Rogerson is CIB) which starts recruitment in July 2022.

Plasma from recruited women will be screened for high levels of IgG antibody to full length VAR2CSA by ELISA. After delivery, up to 10 women with high levels of antibody will be consented for 50-60 ml blood draws, from each of which ~ 5-6 x 107 peripheral blood mononuclear cells (PBMC) will be isolated and cryopreserved for shipping to University of Melbourne. Based on a similar study led by Investigator Rogerson in Madang [3](NCT01136850) we expect seven women attending antenatal care who would fit the proposed criteria for enrolment for antibody screening per week. After blood draws, PBMC will be isolated and stored at -80°C before being shipped to Melbourne where we have collaborations with Amy Chung and Adam Wheatley to sequence, express and characterize monoclonal antibodies to placental binding malaria antigen VAR2CSA. Note, along with Wheatley and Chung- we have already expressed and characterized an anti-VAR2CSA antibody using a sequence shared by collaborator Lars Hviid (Damelang et al in preparation). The existing antibody engages leukocytes leading to phagocytosis and cellular activation, but it does not, however, block placental binding.

Enabling Technologies & Assays

Jun 2022 — Oct 2023

$15,000

Papua New Guinea

Australian Centre for Research Excellence in Malaria Elimination (ACREME)