Biology subjects

Alam, M.

Publications and source records attributed to Alam, M..

3 recordsLinked to original sources

bioRxiv2018

Validation of the protein kinase PfCLK3 as a multi-stage cross species malarial drug target

The requirement for next generation anti-malarials to be both curative and transmission blockers necessitate the identification of molecular pathways essential for viability of both asexual and sexual parasite life stages. Here we identify a selective inhibitor to the Plasmodium falciparum protein kinase PfCLK3 which we use in combination with chemogenetics, whole genome sequencing and transcriptomics to validate PfCLK3 as a druggable target acting at multiple parasite life stages. Consistent with the proposed role of PfCLK3 as a regulator of RNA splicing, inhibition results in the down-regulation of >400 genes essential for parasite survival. Through this mechanism, blocking PfCLK3 activity not only results in rapid killing of asexual blood stage parasites but is also effective on sporozoites and gametocytes as well as showing parasiticidal activity in all Plasmodium species tested. Hence, our data establishes PfCLK3 as a target with the potential to deliver both symptomatic treatment and transmission blocking in malaria.

microbiology↗

bioRxiv2018

Competition between mobile genetic elements drives optimization of a phage-encoded CRISPR-Cas system: Insights from a natural arms-race

CRISPR-Cas systems function as adaptive immune systems by acquiring nucleotide sequences called spacers that mediate sequence-specific defense against competitors. Uniquely, the phage ICP1 encodes a Type I-F CRISPR-Cas system that is deployed to target and overcome PLE, a mobile genetic element with anti-phage activity in Vibrio cholerae. Here, we exploit the arms race between ICP1 and PLE to examine spacer acquisition and interference under laboratory conditions to reconcile findings from wild populations. Natural ICP1 isolates encode multiple spacers directed against PLE, but we find that single spacers do not equally interfere with PLE mobilization. High-throughput sequencing to assay spacer acquisition reveals that ICP1 can also acquire spacers that target the V. cholerae chromosome. We find that targeting the V. cholerae chromosome proximal to PLE is sufficient to block PLE and propose a model in which indirect chromosomal spacers are able to circumvent PLE by Cas2-3-mediated processive degradation of the V. cholerae chromosome before PLE mobilization. Generally, laboratory acquired spacers are much more diverse than the subset of spacers maintained by ICP1 in nature, showing how evolutionary pressures can constrain CRISPR-Cas targeting in ways that are often not appreciated through in vitro analyses.

microbiology↗

bioRxiv2018

Household Transmission Study of Cryptosporidiosis in Bangladesh

BackgroundCryptosporidium, an apicomplexan protozoa, is a leading contributor to diarrheal morbidity and mortality in children under five years old worldwide. As there is no vaccine and no approved drug for Cryptosporidium spp. in young children, preventing parasite transmission is crucial. We undertook a pilot case-control study to define the extent of person-to-person transmission of cryptosporidiosis within families in an urban and rural community in Bangladesh.\n\nMethodsWe enrolled 48 case families with a Cryptosporidium-infected child aged 6-18 months. Controls were age-sex matched Cryptosporidium-negative children (n=12). Once children were identified, we enrolled all household members. We then followed these individuals for 8 weeks, with weekly surveillance stools and testing with qPCR for Cryptosporidium spp.\n\nFindingsIn the 48 case families, the rate of secondary infections with Cryptosporidium was 18.6% (22/118) compared to 0 new infections (0/35) in the 12 control families. In the 22 urban Mirpur households, the secondary attack rate was 30% (18/60) in cases compared to 0% (0/14) in controls (chi-square p = 0.018). In contrast, in the 21 rural Mirzapur households, the secondary attack rate was 6.9% (4/58) in case households compared to 0% (0/21) in controls (chi-square p = 0.22). Genotyping by gp60 demonstrated infection with the same subspecies in five of six families. Serologic response to Cryptosporidium infection was associated with younger age, longer duration of infection, and C hominis gp60_IbA9G3R2 infection.\n\nInterpretationThe high rate of secondary infection in Mirpur suggests that person-to-person transmission is likely a major source of Cryptosporidium infection for young children living in this region. GP 60 genotyping demonstrated direction of infection in 2 households, and concurrent infection in five households. Further work is needed to understand the differences in parasite transmissibility and immunity to different genotypes.

microbiology↗