A long-standing paradigm in virology was that non-enveloped viruses induce cell lysis to release progeny virions. However, emerging evidence indicates that some non-enveloped viruses exit cells without inducing cell lysis, while others engage both lytic and non-lytic egress mechanisms. Enteric viruses are transmitted via the faecal–oral route and are important causes of a wide range of human infections, both gastrointestinal and extra-intestinal. Virus cellular egress, when fully understood, may be a relevant target for antiviral therapies, which could minimize the public health impact of these infections. In this review, we outline lytic and non-lytic cell egress mechanisms of non-enveloped enteric RNA viruses belonging to five families: Picornaviridae, Reoviridae, Caliciviridae, Astroviridae and Hepeviridae. We discuss factors that contribute to egress mechanisms and the relevance of these mechanisms to virion stability, infectivity and transmission. Since most data were obtained in traditional two-dimensional cell cultures, we will further attempt to place them into the context of polarized cultures and in vivo pathogenesis. Throughout the review, we highlight numerous knowledge gaps to stimulate future research into the egress mechanisms of these highly prevalent but largely understudied viruses.

The highly infectious nature of SARS-CoV-2 necessitates using bio-containment facilities to study viral pathogenesis and identify potent antivirals. However, the lack of high-level bio-containment laboratories across the world has limited research efforts into SARS-CoV-2 pathogenesis and the discovery of drug candidates. Previous research has reported that non-replicating SARS-CoV-2 Spike-pseudotyped viral particles are effective tools to screen for and identify entry inhibitors and neutralizing antibodies. To generate SARS-CoV-2 pseudovirus, a lentiviral packaging plasmid p8.91, a luciferase expression plasmid pCSFLW, and SARS-CoV-2 Spike expression plasmids (Wild-type (D614G) or Delta strain) were co-transfected into HEK293 cells to produce a luciferase-expressing non-replicating pseudovirus which expresses SARS-CoV-2 spike protein on the surface. For relative quantitation, HEK293 cells expressing ACE2 (ACE2-HEK293) were infected with the pseudovirus, after which luciferase activity in the cells was measured as a relative luminescence unit. The ACE2-HEK293/Pseudovirus infection system was used to assess the antiviral effects of some compounds and plasma from COVID-19 patients to demonstrate the utility of this assay for drug discovery and neutralizing antibody screening. We successfully produced lentiviral-based SARS-CoV2 pseudoviruses and ACE2-expressing HEK293 cells. The system was used to screen compounds for SARS-CoV-2 entry inhibitors and identified two compounds with potent activity against SARS-CoV-2 pseudovirus entry into cells. The assay was also employed to screen patient plasma for neutralizing antibodies against SARS-CoV-2, as a precursor to live virus screening, using successful hits. This assay is scalable and can perform medium-to high-throughput screening of antiviral compounds with neither severe biohazard risks nor the need for higher-level containment facilities. Now fully deployed in our resource-limited laboratory, this system can be applied to other highly infectious viruses by swapping out the envelope proteins in the plasmids used in pseudovirus production.

Babesia and Theileria are protozoan parasites belonging to the order piroplasmida, transmitted by hard ticks, and can cause diseases known as piroplasmosis. Human infections are usually asymptomatic, except in immuno-compromised persons who present malaria-like symptoms. Moreover, microscopically, the morphologies of Babesia and Theileria can resemble that of the malaria parasite, Plasmodium. In malaria-endemic areas with limited resources, these similarities can increase the possibility of misdiagnosing a patient as having malaria instead of piroplasmosis, which may further lead to inappropriate choice of disease management. This preliminary investigation aimed at detecting Babesia/Theileria in cattle, dogs and humans in some parts of Accra. Whole blood samples were taken from febrile cattle (n = 30) and dogs (n = 33), as well as humans diagnosed with malaria (n = 150). Blood samples of all study subjects were microscopically screened for possible presence of haemoparasites. Samples whose smears had features suggestive of possible piroplasmic infection were all given the label “suspected Babesia/Theileria-infected” samples. Nested polymerase chain reaction (PCR) was performed on extracted deoxyribonucelic acid (DNA) from all the “suspected” samples of cattle, dogs and humans, with primer sets that can detect 18S rRNA genes of Babesia/Theileria spp. In addition to this, amplification was performed on the “suspected” dog samples using the BcW-A/BcW-B primer set which detects the 18S rRNA genes of B. canis, while the BoF/BoR primer set which targets the rap-1 region of B. bovis and another primer set which detects the 18S rRNA genes of most bovine Babesia spp. (including B. divergens) were used on the suspected cattle samples. For the human samples, however, additional amplification was done on the extracted DNA using primers for the three other Babesia targeted (B. divergens, B. bovis and B. canis). Microscopy showed possible Babesia/Theileria infection suspected in all three groups of subjects in the following proportions: cattle (10/30; 33%), dogs (3/33; 9%) and humans (6/150; 4%). DNA from one-third of the “suspected” dog samples yielded amplification with Babesia canis primers. Moreover, a broad-detecting set of primers (that can amplify some Babesia and Theileria species) amplified DNA from nine (9/30; 30%) of the “suspected” cattle samples, but none from those of the humans. Although for this study conducted in the city, the Babesia/Theileria primers used did not amplify DNA from the six “suspected” human samples; the possibility of Babesia/Theileria infection in humans in other parts of the country cannot be overruled. There is therefore a need for further studies on possible emergence of human babesiosis/theileriosis in other parts of Ghana and sequencing for specific identification of any circulating strain.

Africa reported lower COVID-19-related morbidity and mortality compared to other continents, despite widespread SARS-CoV-2 transmission and limited vaccine access. Proposed immunological explanations include potential pre-existing immunity such as cross-reactive humoral or cellular responses from earlier coronavirus exposures. However, functional immune responses to SARS-CoV-2 in African populations remain poorly characterized. To address this gap, we assessed post-pandemic neutralizing antibody responses against the SARS-CoV-2 D614G variant. We analyzed plasma samples from 989 participants in a cross-sectional survey in Ghana’s Eastern and Greater Accra regions. A live virus neutralization assay using Vero E6 TMPRSS2 cells was employed to quantify SARS-CoV-2 D614G-specific neutralizing antibodies. Responses were assessed across collected demographic data. Urban participants exhibited higher median neutralizing antibody titers than rural counterparts, in both vaccinated and unvaccinated groups (p < 0.0001). Among unvaccinated individuals, median neutralizing antibody titers were comparable across age groups in urban settings. Vaccinated individuals showed elevated median titers across all age groups, with urban residents demonstrating stronger responses. Significant sex-based differences in neutralizing titres were also identified. Our findings reveal marked disparities in functional antibody responses between urban and rural populations, likely shaped by differences in SARS-CoV-2 exposure and vaccination. Continued surveillance and immunological profiling remain key for informing vaccine strategies and future pandemic preparedness.

Background: Africa seemed to have had low SARS-CoV-2 infection and COVID-19 morbidity and mortality. While several studies reported high SARS-CoV-2 seropositivity among healthy Africans, others hypothesized that this could have resulted from pre-existing cross-reactive antibodies. Our study tracks trends in seropositivity across three West African countries during the Delta and Omicron pandemic waves using a validated test kit with 98.9% predictive accuracy, 97% sensitivity, and 99% specificity.Methods: Cross-sectional studies were conducted across three West African countries (Burkina Faso, Ghana, and Nigeria) with study sites conveniently selected in each country. Using the validated immunoassay kits, with already published validation procedures, SARS-CoV-2 antibodies were detected in peripheral blood during the ‘Delta’ and ‘Omicron’ waves. Participants' demographic and clinical data were obtained using a semi-structured questionnaire, and the primary outcome was the proportion of each population with SARS-CoV-2 antibodies.Findings: Across the 3 countries, 20,748 participants were recruited, and the results showed SARS-CoV-2 IgG seropositivity ranging between 24.1% to 77.0%, which increased during the Omicron wave. All sites showed low self-reported vaccination rates, delinking seropositivity and vaccination. While there was a significant positive association between seropositivity and age across all sites, the association with other demographic factors was country-dependent, and most participants expressed positive opinions of vaccination.Interpretation: This is one of the largest population-based SARS-CoV-2 seroepidemiology studies in Africa, confirming widespread mild SARS-CoV-2 infection in West Africa. This confirms a marked disconnect between high population exposure and low reported clinical burden, underscoring the need for strengthened community surveillance.