Knowledge, attitude and perception towards COVID-19 among representative educated sub-Saharan Africans: A cross-sectional study during the exponential phase of the pandemic.

Coronavirus disease 2019 (COVID-19) pandemic, caused by the Severe Acute Coronavirus 2 (SARS-CoV-2), is a global health threat with extensive misinformation and conspiracy theories. Therefore, this study investigated the knowledge, attitude and perception of sub-Saharan Africans (SSA) on COVID-19 during the exponential phase of the pandemic. In this cross-sectional survey, self-administered web-based questionnaires were distributed through several online platforms. A total of 1046 respondents from 35 SSA countries completed the survey. The median age was 33 years (18-76 years) and about half (50.5%) of them were males. More than 40% across all socio-demographic categories except the Central African region (21.2%), vocational/secondary education (28.6%), student/unemployed (35.5%), had high COVID-19 knowledge score. Socio-demographic factors and access to information were associated with COVID-19 knowledge. Bivariate analysis revealed that independent variables, including the region of origin, age, gender, education and occupation, were significantly (p < 0.05) associated with COVID-19 knowledge. Multivariate analysis showed that residing in East (odds ratio [OR]: 7.9, 95% confidence interval (CI): 4.7-14, p<0.001), Southern (OR: 3.7, 95% CI: 2.1-6.5, p<0.001) and West (OR: 3.9, 95% CI: 2.9-5.2, p<0.001) Africa was associated with high COVID-19 knowledge level. Apart from East Africa (54.7%), willingness for vaccine acceptance across the other SSA regions was <40%. About 52%, across all socio-demographic categories, were undecided. Knowledge level, region of origin, age, gender, marital status and religion were significantly (p < 0.05) associated with COVID-19 vaccine acceptance. About 67.4% were worried about contracting SARS-CoV-2, while 65.9% indicated they would consult a health professional if exposed. More than one-third of the respondents reported that their governments had taken prompt measures to tackle the pandemic. Despite high COVID-19 knowledge in our study population, most participants were still undecided regarding vaccination, which is critical in eliminating the pandemic. Therefore, extensive, accurate, dynamic and timely education in this aspect is of ultimate priority.

Evolution from covalent conjugation to non-covalent interaction in the ubiquitin-like ATG12 system.

Ubiquitin or ubiquitin-like proteins can be covalently conjugated to multiple proteins that do not necessarily have binding interfaces. Here, we show that an evolutionary transition from covalent conjugation to non-covalent interaction has occurred in the ubiquitin-like autophagy-related 12 (ATG12) conjugation system. ATG12 is covalently conjugated to its sole substrate, ATG5, by a ubiquitylation-like mechanism. However, the apicomplexan parasites Plasmodium and Toxoplasma and some yeast species such as Komagataella phaffii (previously Pichia pastoris) lack the E2-like enzyme ATG10 and the most carboxy (C)-terminal glycine of ATG12, both of which are required for covalent linkage. Instead, ATG12 in these organisms forms a non-covalent complex with ATG5. This non-covalent ATG12-ATG5 complex retains the ability to facilitate ATG8-phosphatidylethanolamine conjugation. These results suggest that ubiquitin-like covalent conjugation can evolve to a simpler non-covalent interaction, most probably when the system has a limited number of targets.

Isolation of invasive Plasmodium yoelii merozoites with a long half-life to evaluate invasion dynamics and potential invasion inhibitors.

Malaria symptoms and pathogenesis are caused by blood stage parasite burdens of Plasmodium spp., for which invasion of red blood cells (RBCs) by merozoites is essential. Successful targeting by either drugs or vaccines directed against the whole merozoite or its antigens during its transient extracellular status would contribute to malaria control by impeding RBC invasion. To understand merozoite invasion biology and mechanisms, it is desired to obtain merozoites that retain their invasion activity in vitro. Accordingly, methods have been developed to isolate invasive Plasmodium knowlesi and Plasmodium falciparum merozoites. Rodent malaria parasite models offer ease in laboratory maintenance and experimental genetic modifications; however, no methods have been reported regarding isolation of high numbers of invasive rodent malaria merozoites. In this study, Plasmodium yoelii-infected RBCs were obtained from infected mice, and mature schizont-infected RBCs enriched via Histodenz™ density gradients. Merozoites retaining invasion activity were then isolated by passing the preparations through a filter membrane. RBC-invaded parasites developed to mature stages in vitro in a synchronous manner. Isolated merozoites were evaluated for retention of invasion activity following storage at different temperatures prior to incubation with uninfected mouse RBCs. Isolated merozoites retained their invasion activity 4h after isolation at 10 or 15 °C, whereas their invasion activity reduced to 0-10% within 30 min when incubated on ice or at 37 °C prior to RBC invasion assay. Images of merozoites at successive steps during RBC invasion were captured by light and transmission electron microscopy. Synthetic peptides derived from the amino acid sequence of the P. yoelii invasion protein RON2 efficiently inhibited RBC invasion. The developed method to isolate and keep invasive P. yoelii merozoites for up to 4h is a powerful tool to study the RBC invasion biology of this parasite. This method provides an important platform to evaluate the mode of action of drugs and vaccine candidates targeting the RBC invasion steps using rodent malaria model.

Expression and localization of rhoptry neck protein 5 in merozoites and sporozoites of Plasmodium yoelii.

Host cell invasion by Apicomplexan parasites marks a crucial step in disease establishment and pathogenesis. The moving junction (MJ) is a conserved and essential feature among parasites of this phylum during host cell invasion, thus proteins that associate at this MJ are potential targets of drug and vaccine development. In both Toxoplasma gondii and Plasmodium falciparum, a micronemal protein, Apical Membrane Antigen 1 (AMA1), and Rhoptry Neck proteins (RONs; RON2 and RON4) form an essential complex at the MJ. A new RON member, RON5, was shown to be important to stabilize RON2 during development and to associate with the MJ complex in T. gondii and also to be immunoprecipitated by anti-AMA1 antibody in P. falciparum. However, the detailed molecular nature of RON5 in Plasmodium is not well understood. In this study, Plasmodium yoelii RON5 gene (pyron5) was identified as an ortholog of P. falciparum and Plasmodium berghei ron5. The pyron5 exon-intron structure was validated by comparing genomic DNA sequences and experimentally determining full-length complementary DNA sequence. PyRON5 was detected in water-insoluble fractions but no reliable transmembrane domain(s) were predicted by transmembrane prediction algorithms. PyRON5 formed a complex with PyRON4, PyRON2, and PyAMA1 in late schizont protein extract. Taken together, we infer that these results suggest that PyRON5 associates with membrane indirectly via other MJ components. Indirect immunofluorescence assay and immunoelectron microscopy localized PyRON5 at the rhoptry neck of the late schizont merozoites and at the rhoptry of sporozoites. The two-stage expression of PyRON5 suggests that PyRON5 plays roles in invasion not only of erythrocytes, but also of mosquito salivary glands and/or mammalian hepatocytes.