# Pfs48/45 nanobodies block Plasmodium falciparum transmission

## TL;DR

Scientists developed nanobodies that block malaria parasite fertilization in mosquitoes, potentially reducing transmission.

## Contribution

Nanobodies targeting Pfs48/45 were developed and shown to reduce malaria transmission in mosquitoes.

## Key findings

- Nanobodies against Pfs48/45 significantly reduced parasite transmission in Anopheles mosquitoes.
- The crystal structure of the nanobody-Pfs48/45 complex reveals a distinct epitope compared to TB31F.
- Nanobodies show potential as a versatile antibody format for transmission-blocking interventions.

## Abstract

Malaria parasite fertilisation occurs within the Anopheles mosquito midgut. Interventions that inhibit parasite fertilisation prevent ongoing transmission and are important for malaria elimination efforts. Pfs48/45 and Pfs230 are two leading transmission-blocking vaccine candidates. Both proteins form a complex on the surface of sexual stage parasites and are essential for male fertility. Here we have identified nanobodies against Pfs48/45 that recognise gametocytes and have strong transmission-reducing activity. The crystal structure of our most potent nanobody in complex with Pfs48/45 reveals it binds a distinct epitope to TB31F, a leading transmission-blocking monoclonal antibody but to similar epitopes as RUPA-44 and RUPA-117. These results demonstrate the potential of nanobodies as a versatile antibody format that can reduce malaria transmission.

Malaria is spread when an infected Anopheles mosquito bites a human. Within the female Anopheles mosquito, malaria parasite fertilisation occurs in the mosquito midgut. If you inhibit parasite fertilisation in the mosquito, you can prevent onward transmission of the malaria parasite from mosquito to humans. Transmission blocking vaccines work by stopping parasite fertilisation and development in the mosquito and are key for malaria elimination by preventing community spread. Pfs48/45 and Pfs230 are two leading transmission-blocking vaccine candidates, and both are critical for male fertility. Here we describe the generation of nanobodies that target Pfs48/45. We show that when nanobodies against Pfs48/45 were added to infected blood meals for Anopheles mosquitoes, the nanobodies significantly reduced parasite transmission. Our work demonstrates the potential of nanobodies as a versatile antibody format that can reduce malaria transmission.