Long-acting injectable medications, such as atovaquone, offer the prospect of a "chemical vaccine" for malaria, combining drug efficacy with vaccine durability. However, selection and transmission of ...drug-resistant parasites is of concern. Laboratory studies have indicated that atovaquone resistance disadvantages parasites in mosquitoes, but lack of data on clinically relevant Plasmodium falciparum has hampered integration of these variable findings into drug development decisions. Here we generate atovaquone-resistant parasites that differ from wild type parent by only a Y268S mutation in cytochrome b, a modification associated with atovaquone treatment failure in humans. Relative to wild type, Y268S parasites evidence multiple defects, most marked in their development in mosquitoes, whether from Southeast Asia (Anopheles stephensi) or Africa (An. gambiae). Growth of asexual Y268S P. falciparum in human red cells is impaired, but parasite loss in the mosquito is progressive, from reduced gametocyte exflagellation, to smaller number and size of oocysts, and finally to absence of sporozoites. The Y268S mutant fails to transmit from mosquitoes to mice engrafted with human liver cells and erythrocytes. The severe-to-lethal fitness cost of clinically relevant atovaquone resistance to P. falciparum in the mosquito substantially lessens the likelihood of its transmission in the field.
Trypanosoma brucei gambiense is the primary causative agent of human African trypanosomiasis (HAT), a vector-borne disease endemic to West and Central Africa. The extracellular parasite evades ...antibody recognition within the host bloodstream by altering its variant surface glycoprotein (VSG) coat through a process of antigenic variation. The serological tests that are widely used to screen for HAT use VSG as one of the target antigens. However, the
expressed during human infection have not been characterized. Here, we use VSG sequencing (VSG-seq) to analyze the
expressed in the blood of patients infected with T. b. gambiense and compared them to VSG expression in Trypanosoma brucei rhodesiense infections in humans as well as Trypanosoma brucei brucei infections in mice. The 44
expressed during T. b. gambiense infection revealed a striking bias toward expression of type B N termini (82% of detected VSGs). This bias is specific to T. b. gambiense, which is unique among T. brucei subspecies in its chronic clinical presentation and anthroponotic nature. The expressed T. b. gambiense
also share very little similarity to sequences from 36 T. b. gambiense whole-genome sequencing data sets, particularly in areas of the VSG protein exposed to host antibodies, suggesting the antigen repertoire is under strong selective pressure to diversify. Overall, this work demonstrates new features of antigenic variation in T. brucei
and highlights the importance of understanding
repertoires in nature.
Human African trypanosomiasis is a neglected tropical disease primarily caused by the extracellular parasite Trypanosoma brucei gambiense. To avoid elimination by the host, these parasites repeatedly replace their variant surface glycoprotein (VSG) coat. Despite the important role of VSGs in prolonging infection,
expression during human infections is poorly understood. A better understanding of natural
gene expression dynamics can clarify the mechanisms that T. brucei uses to alter its VSG coat. We analyzed the expressed
detected in the blood of patients with trypanosomiasis. Our findings indicate that there are features of antigenic variation unique to human-infective T. brucei subspecies and that natural
repertoires may vary more than previously expected.
Renal medullary carcinoma (RMC) is a rare and deadly kidney cancer in patients of African descent with sickle cell trait. We have developed faithful patient-derived RMC models and using whole-genome ...sequencing, we identified loss-of-function intronic fusion events in one
allele with concurrent loss of the other allele. Biochemical and functional characterization of these models revealed that RMC requires the loss of
for survival. Through integration of RNAi and CRISPR-Cas9 loss-of-function genetic screens and a small-molecule screen, we found that the ubiquitin-proteasome system (UPS) was essential in RMC. Inhibition of the UPS caused a G2/M arrest due to constitutive accumulation of cyclin B1. These observations extend across cancers that harbor
loss, which also require expression of the E2 ubiquitin-conjugating enzyme,
. Our studies identify a synthetic lethal relationship between
-deficient cancers and reliance on the UPS which provides the foundation for a mechanism-informed clinical trial with proteasome inhibitors.
What genes determine
growth and nutrient utilization in asexual blood-stage malaria parasites? Competition experiments between NF54, clone 3D7, a lab-adapted African parasite, and a recently isolated ...Asian parasite (NHP4026) reveal contrasting outcomes in different media: 3D7 outcompetes NHP4026 in media containing human serum, while NHP4026 outcompetes 3D7 in media containing AlbuMAX, a commercial lipid-rich bovine serum formulation. To determine the basis for this polymorphism, we conducted parasite genetic crosses using humanized mice and compared genome-wide allele frequency changes in three independent progeny populations cultured in media containing human serum or AlbuMAX. This bulk segregant analysis detected three quantitative trait loci (QTL) regions on chromosome (chr) 2 containing aspartate transaminase
; chr 13 containing
and chr 14 containing cysteine protease
linked with differential growth in serum or AlbuMAX in each of the three independent progeny pools. Selection driving differential growth was strong (
= 0.10 - 0.23 per 48-hour lifecycle). We conducted validation experiments for the strongest QTL on chr 13: competition experiments between ΔEBA-140 and 3D7 wildtype parasites showed fitness reversals in the two medium types as seen in the parental parasites, validating this locus as the causative gene. These results (i) demonstrate the effectiveness of bulk segregant analysis for dissecting fitness traits in
genetic crosses, and (ii) reveal intimate links between red blood cell invasion and nutrient composition of growth media. Use of parasite crosses combined with bulk segregant analysis will allow systematic dissection of key nutrient acquisition/metabolism and red blood cell invasion pathways in
The cumulative outcomes of health research in the modern times had a huge effect on human health and longevity. The primary care physicians are the first point of contact between the health system ...and the society. Therefore their responsibility is higher to provide the latest information to their patients, in the context of rapidly changing field of medical science. Doctors are expected to have a basic knowledge of research methodology in order to develop a critical thinking and this is the rationale to include the research activity is an integral part of post-graduate medical training.
We aimed to assess the previous involvement in research activities and knowledge in basic research methods among primary care physicians in central region, Saudi Arabia.
It was a cross sectional descriptive study conducted on a conveniently selected sample of doctors (N=80) working under general directorate of health affairs in Riyadh region, Ministry of Health. The data was collected through a pre-designed, self-administered survey instrument containing closed ended questions.
The mean age of the physicians was observed to be 44.7 ± 9.6 years. About 32% doctors had previous experience of writing a research proposal while only 20% had any publication in a scientific journal. About 45% had attended workshop on research methodology within last five years. Only one item related to 'consent in medical research' was answered correctly by 60% respondents. The correct responses in other knowledge items scored less than 50% (ranging from 18.8% to 37.5%). The proportion of doctors having any publication was observed to significantly higher among younger age (p<0.05). Significantly higher proportion was observed for "having experience of proposal writing" and "paper presentation in a scientific conference" among family medicine and other specialties as compared to general practice (p<0.05).
We found low previous engagement with research among doctors with low level of knowledge regarding basic research methods. This was particularly evident among general practitioners as compared specialist doctors. Regular conduction of research workshop with encouragement to undertake small research activities at the primary care should be promoted.
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