Theoretical implications of a pre-erythrocytic Plasmodium vivax vaccine for preventing relapses

Preventing malaria infection through vaccination requires preventing every sporozoite inoculated by mosquito bite: a major challenge for Plasmodium falciparum. Plasmodium vivax sporozoites consist of tachysporozoites causing primary infection and bradysporozoites leading to relapses.We hypothesise that a candidate P. vivax vaccine with low efficacy against primary infection may substantially reduce transmission by preventing relapses

TRSP is dispensable for the Plasmodium pre-erythrocytic phase

Plasmodium sporozoites deposited in the skin following a mosquito bite must migrate and invade blood vessels to complete their development in the liver. Once in the bloodstream, sporozoites arrest in the liver sinusoids, but the molecular determinants that mediate this specific homing are not yet genetically defined. Here we investigate the involvement of the thrombospondin-related sporozoite protein (TRSP) in this process using knockout Plasmodium berghei parasites and in vivo bioluminescence imaging in mice. Resorting to a homing assay, trsp knockout sporozoites were found to arrest in the liver similar to control parasites. Moreover, we found no defects in the establishment of infection in mice following inoculation of trsp knockout sporozoites via intravenous and cutaneous injection or mosquito bite. Accordingly, mutant sporozoites were also able to successfully invade hepatocytes in vitro. Altogether, these results suggest TRSP may have a redundant role in the completion of the pre-erythrocytic phase of the malaria parasite. Nonetheless, identifying molecules with paramount roles in this phase could aid in the search for new antigens needed for the design of a protective vaccine against malaria.We would like to thank: Prof. Anabela Cordeiro da Silva from the IBMC/i3S for the exceptional hosting conditions; Dr. Ana Xavier Carvalho from the IBMC/i3S for the critical reading of the manuscript; the team of the CEPIA from Institut Pasteur, Paris, for providing the Anopheles stephensi female mosquitos. The following reagents were obtained through BEI Resources, NIAID, NIH: (a) Plasmid pL0001, for Transfection in Plasmodium berghei, MRA-770, contributed by Andrew P. Waters; (b) Hybridoma 3D11 Anti-Plasmodium berghei 44-Kilodalton Sporozoite Surface Protein (Pb44), MRA-100, contributed by Victor Nussenzweig. This work was supported by funds from project Norte-01-0145-FEDER-000012 - Structured program on bioengineered therapies for infectious diseases and tissue regeneration, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through FEDER. This work also received funds from the Fundação para a Ciência e Tecnologia (FCT)/Ministério da Educação e Ciência (MEC) co-funded by FEDER (EXPL/JTAVARES-IF/00881/2012/CP0158/CT0005,EXPL/IMI-MIC/1331/ 2013) under the Partnership agreement PT2020, through the Research Unit No. 4293. J.T. is an Investigator FCT funded by National funds through FCT and co-funded through European Social Fund within the Human Potential Operating Programme. D.M.C., M.S. and A.R.T. are funded by FCT individual fellowships SFRH/ BD/123734/2016, SFRH/BD/133485/2017 and SFRH/BD/133276/2017 respectively). The authors acknowledge the support of the BioSciences Screening i3S Scientific Platform, member of the PPBI (PPBI-POCI-01-0145-FEDER-022122)

Analysis of an insertion mutation in a cohort of 94 patients with spinocerebellar ataxia type 31 from Nagano, Japan

Spinocerebellar ataxia type 31 (SCA31) is a recently defined subtype of autosomal dominant cerebellar ataxia (ADCA) characterized by adult-onset, pure cerebellar ataxia. The C/T substitution in the 5′-untranslated region of the puratrophin-1 gene (PLEKHG4) or a disease-specific haplotype within the 900-kb SCA31 critical region just upstream of PLEKHG4 has been used for the diagnosis of SCA31. Very recently, a disease-specific insertion containing penta-nucleotide (TGGAA)n repeats has been found in this critical region in SCA31 patients. SCA31 was highly prevalent in Nagano, Japan, where SCA31 accounts for approximately 42% of ADCA families. We screened the insertion in 94 SCA31 patients from 71 families in Nagano. All patients had a 2.6- to 3.7-kb insertion. The size of the insertion was inversely correlated with the age at onset but not associated with the progression rate after onset. (TAGAA)n repeats at the 5′-end of the insertion were variable in number, ranging from 0 (without TAGAA sequence) to 4. The number of (TAGAA)n repeats was inversely correlated to the total size of the insertion. The number of (TAGAA)n repeats was comparatively uniform within patients from the three endemic foci in Nagano. Only one patient, heterozygous for the C/T substitution in PLEKHG4, had the insertions in both alleles; they were approximately 3.0 and 4.3 kb in size. Sequencing and Southern hybridization using biotin-labeled (TGGAA)5 probe strongly indicated that the 3.0-kb insertion, but not the 4.3-kb insertion, contained (TGGAA)n stretch. We also found that 3 of 405 control individuals (0.7%) had the insertions from 1.0 to 3.5 kb in length. They were negative for the C/T substitution in PLEKHG4, and neither of the insertions contained (TGGAA)n stretch at their 5′-end by sequencing. The insertions in normal controls were clearly detected by Southern hybridization using (TAAAA)5 probe, while they were not labeled with (TGGAA)5 or (TAGAA)5 probe. These data indicate that control alleles very rarely have a nonpathogenic large insertion in the SCA31 critical region and that not only the presence of the insertion but also its size is not sufficient evidence for a disease-causing allele. We approve of the view that (TGGAA)n repeats in the insertion are indeed related to the pathogenesis of SCA31, but it remains undetermined whether a large insertion lacking (TGGAA)n is nonpathogenic

The malaria circumsporozoite protein has two functional domains, each with distinct roles as sporozoites journey from mosquito to mammalian host

Conformational changes influence functional properties of circumsporozoite protein expressed on the surface of Plasmodium sporozoites

The Puf-Family RNA-Binding Protein Puf2 Controls Sporozoite Conversion to Liver Stages in the Malaria Parasite

Malaria is a vector-borne infectious disease caused by unicellular, obligate intracellular parasites of the genus Plasmodium. During host switch the malaria parasite employs specialized latent stages that colonize the new host environment. Previous work has established that gametocytes, sexually differentiated stages that are taken up by the mosquito vector, control expression of genes required for mosquito colonization by translational repression. Sexual parasite development is controlled by a DEAD-box RNA helicase of the DDX6 family, termed DOZI. Latency of sporozoites, the transmission stage injected during an infectious blood meal, is controlled by the eIF2alpha kinase IK2, a general inhibitor of protein synthesis. Whether RNA-binding proteins participate in translational regulation in sporozoites remains to be studied. Here, we investigated the roles of two RNA-binding proteins of the Puf-family, Plasmodium Puf1 and Puf2, during sporozoite stage conversion. Our data reveal that, in the rodent malaria parasite P. berghei, Puf2 participates in the regulation of IK2 and inhibits premature sporozoite transformation. Inside mosquito salivary glands puf2(-) sporozoites transform over time to round forms resembling early intra-hepatic stages. As a result, mutant parasites display strong defects in initiating a malaria infection. In contrast, Puf1 is dispensable in vivo throughout the entire Plasmodium life cycle. Our findings support the notion of a central role for Puf2 in parasite latency during switch between the insect and mammalian hosts

Prevalence of pre- and postpartum depression in Jamaican women

BACKGROUND: Maternal depression during pregnancy has been studied less than depression in postpartum period. The aims of this study were to find out the prevalence of prepartum and postpartum depression and the risk factors associated in a cohort of Afro-Jamaican pregnant women in Jamaica. METHODS: The Zung self-rating depression scale instrument was administered to 73 healthy pregnant women at 28 weeks gestation and at 6 weeks postpartum for quantitative measurement of depression. Blood samples were collected at 8, 28, 35 weeks gestation and at day 1 and 6 weeks postpartum to study the thyroid status. RESULTS: Study demonstrated depression prevalence rates of 56% and 34% during prepartum and postpartum period, respectively. 94% women suffering depression in both periods were single. There were significant variations in both FT(3 )and TT(4 )concentrations which increased from week 8 to week 28 prepartum (p < 0.05) and then declined at the 35(th )week (p < 0.05 compared with week 28) and 1 day post delivery study (p < 0.05 compared with week 35). The mean values for TSH increased significantly from week 8 through week 35. The mean values at 1 day postpartum and 6 week postpartum were not significantly different from the 35 week values. For FT(3), TT(4 )and TSH there were no significant between group differences in concentrations. The major determinants of postpartum depression were moderate and severe prepartum depression and change in TT(4 )hormone concentrations. CONCLUSION: High prevalence of depression was found during pre- and postpartum periods. Single mothers, prepartum depression and changes in TT(4 )were factors found to be significantly associated with postpartum depression

Environmental Constraints Guide Migration of Malaria Parasites during Transmission

Migrating cells are guided in complex environments mainly by chemotaxis or structural cues presented by the surrounding tissue. During transmission of malaria, parasite motility in the skin is important for Plasmodium sporozoites to reach the blood circulation. Here we show that sporozoite migration varies in different skin environments the parasite encounters at the arbitrary sites of the mosquito bite. In order to systematically examine how sporozoite migration depends on the structure of the environment, we studied it in micro-fabricated obstacle arrays. The trajectories observed in vivo and in vitro closely resemble each other suggesting that structural constraints can be sufficient to guide Plasmodium sporozoites in complex environments. Sporozoite speed in different environments is optimized for migration and correlates with persistence length and dispersal. However, this correlation breaks down in mutant sporozoites that show adhesion impairment due to the lack of TRAP-like protein (TLP) on their surfaces. This may explain their delay in infecting the host. The flexibility of sporozoite adaption to different environments and a favorable speed for optimal dispersal ensures efficient host switching during malaria transmission