Malaria kills >1 million people each year, in particular in subSaharan Africa. Although asexual forms are directly responsible for disease and death, sexual stages account for the transmission of Plasmodium parasites from human to the mosquito vector and therefore the spread of the parasite in the population. Development of a malaria vaccine is urgently needed to reduce morbidity and mortality. Vaccines against sexual stages of Plasmodium falciparum are meant to decrease the force of transmission and consequently reduce malaria burden. Pfs48/45 is specifically expressed in sexual stages and is a well established transmissionblocking (TB) vaccine candidate. However, production of correctly folded recombinant Pfs48/45 protein with display of its TB epitopes has been a major challenge. Here, we show the production of a properly folded Pfs48/45 C-terminal fragment by simultaneous coexpression with four periplasmic folding catalysts in Escherichia coli. This C-terminal fragment fused to maltose binding protein was produced at medium scale with >90% purity and a stability over at least a 9-month period. It induces uniform and high antibody titers in mice and elicits functional TB antibodies in standard membrane feeding assays in 90% of the immunized mice. Our data provide a clear perspective on the clinical development of a Pfs48/45-based TB malaria vaccine. M alaria parasites are spread in the population by Plasmodium-infected Anopheles mosquitoes. Successful transmission of malarial parasites from humans to mosquitoes depends on the presence and infectiousness of gametocytes in the peripheral blood and the number of Anopheles mosquitoes in the area. Transmission of Plasmodium falciparum can be blocked inside the mosquito by antibodies that have been ingested together with the gametocytes as part of a blood meal, interrupting the sporogonic cycle inside the mosquito (1).Pfs48/45 is a transmission-blocking (TB) target protein expressed by gametocytes (2-4) and present on the surface of the sporogonic (macrogametes) stages of the malaria parasites. Pfs48/45 plays a key role in parasite fertilization (5) and antibodies that exclusively target conformational epitopes of Pfs48/45 protein prevent fertilization (6, 7). Furthermore, antiPfs48/45 antibodies are present in human sera from endemic areas (8) and correlate with TB activity (8-10). The induction of antibodies after natural infection as observed in the field creates the highly beneficial potential of vaccine boosting in the endemic setting. TB vaccines might be applied alone or more likely as part of a combination vaccine or package of control measures depending on the intensity of malaria transmission (11).A strategy for vaccine development requires the production of correctly folded recombinant Pfs48/45 protein. Proper folding of many cysteine-rich proteins, including Pfs48/45, depends on correct formation of disulphide bridges. In eukaryotes the oxidizing environment of the endoplasmic reticulum (ER) provides a milieu for disulphide bonds formation. Plasmodium p...