Abstract
Background
Africa bears a disproportionately high burden of globally significant disease but has lagged in knowledge production to address its health challenges. In this contribution, we ...discuss the challenges and approaches to health research capacity strengthening in sub-Saharan Africa and propose that the recent shift to an African-led approach is the most optimal.
Methods and findings
We introduce several capacity building approaches and recent achievements, explore why African-led research on the continent is a potentially paradigm-shifting and innovative approach, and discuss the advantages and challenges thereof. We reflect on the approaches used by the African Academy of Sciences (AAS)-funded Sub-Saharan African Network for TB/HIV Research Excellence (SANTHE) consortium as an example of an effective African-led science and capacity building programme. We recommend the following as crucial components of future efforts: 1. Directly empowering African-based researchers, 2. Offering quality training and career development opportunities to large numbers of junior African scientists and support staff, and 3. Effective information exchange and collaboration. Furthermore, we argue that long-term investment from international donors and increasing funding commitments from African governments and philanthropies will be needed to realise a critical mass of local capacity and to create and sustain world-class research hubs that will be conducive to address Africa’s intractable health challenges.
Conclusions
Our experiences so far suggest that African-led research has the potential to overcome the vicious cycle of brain-drain and may ultimately lead to improvement of health and science-led economic transformation of Africa into a prosperous continent.
Many pathogens evade cytotoxic T lymphocytes (CTLs) by downregulating HLA molecules on infected cells, but the loss of HLA can trigger NK cell-mediated lysis. HIV-1 is thought to subvert CTLs while ...preserving NK cell inhibition by Nef-mediated downregulation of HLA-A and -B but not HLA-C molecules. We find that HLA-C is downregulated by most primary HIV-1 clones, including transmitted founder viruses, in contrast to the laboratory-adapted NL4-3 virus. HLA-C reduction is mediated by viral Vpu and reduces the ability of HLA-C restricted CTLs to suppress viral replication in CD4+ cells in vitro. HLA-A/B are unaffected by Vpu, and primary HIV-1 clones vary in their ability to downregulate HLA-C, possibly in response to whether CTLs or NK cells dominate immune pressure through HLA-C. HIV-2 also suppresses HLA-C expression through distinct mechanisms, underscoring the immune pressure HLA-C exerts on HIV. This viral immune evasion casts new light on the roles of CTLs and NK cells in immune responses against HIV.
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•Most primary HIV-1 clones downregulate HLA-C, in contrast to lab-adapted strains•Vpu is responsible for HLA-C downregulation in viruses of multiple HIV-1 subtypes•Primary HIV-1 clones frequently vary in their magnitude of HLA-C reduction•HIV-2 shows a Vpu-independent mechanism of HLA-C downregulation
HIV-1 Nef downregulates HLA-A and -B but not HLA-C molecules on infected cells, presumably allowing viral subversion of CTL responses while preserving NK cell inhibition. Apps et al. determine that Vpu in primary HIV clones downregulates HLA-C, collectively resulting in decreased expression of all classical HLA class I molecules by HIV.
HIV Nef counteracts cellular host restriction factors SERINC3 and SERINC5, but our understanding of how naturally occurring global Nef sequence diversity impacts these activities is limited. Here, we ...quantify SERINC3 and SERINC5 internalization function for 339 Nef clones, representing the major pandemic HIV-1 group M subtypes A, B, C and D. We describe distinct subtype-associated hierarchies for Nef-mediated internalization of SERINC5, for which subtype B clones display the highest activities on average, and of SERINC3, for which subtype B clones display the lowest activities on average. We further identify Nef polymorphisms that modulate its ability to counteract SERINC proteins, including substitutions in the N-terminal domain that selectively impair SERINC3 internalization. Our findings demonstrate that the SERINC antagonism activities of HIV Nef differ markedly among major viral subtypes and between individual isolates within a subtype, suggesting that variation in these functions may contribute to global differences in viral pathogenesis.
The continued burden of HIV in resource-limited regions such as parts of sub-Saharan Africa, combined with adverse effects and potential risks of resistance to existing antiretroviral therapies, ...emphasize the need to identify new HIV inhibitors. Here we performed a virtual screen of molecules from the pan-African Natural Product Library, the largest collection of medicinal plant-derived pure compounds on the African continent. We identified eight molecules with structural similarity to reported interactors of Vpu, an HIV-1 accessory protein with reported ion channel activity. Using in vitro HIV-1 replication assays with a CD4+ T cell line and peripheral blood mononuclear cells, we confirmed antiviral activity and minimal cytotoxicity for two compounds, ixoratannin A-2 and boldine. Notably, ixoratannin A-2 retained inhibitory activity against recombinant HIV-1 strains encoding patient-derived mutations that confer resistance to protease, non-nucleoside reverse transcriptase, or integrase inhibitors. Moreover, ixoratannin A-2 was less effective at inhibiting replication of HIV-1 lacking Vpu, supporting this protein as a possible direct or indirect target. In contrast, boldine was less effective against a protease inhibitor-resistant HIV-1 strain. Both ixoratannin A-2 and boldine also inhibited in vitro replication of hepatitis C virus (HCV). However, BIT-225, a previously-reported Vpu inhibitor, demonstrated antiviral activity but also cytotoxicity in HIV-1 and HCV replication assays. Our work identifies pure compounds derived from African plants with potential novel activities against viruses that disproportionately afflict resource-limited regions of the world.
The human leukocyte antigens HLA-B27 and HLA-B57 are associated with protection against progression of disease that results from infection with human immunodeficiency virus type 1 (HIV-1), yet most ...people with alleles encoding HLA-B27 and HLA-B57 are unable to control HIV-1. Here we found that HLA-B27-restricted CD8(+) T cells in people able to control infection with HIV-1 (controllers) and those who progress to disease after infection with HIV-1 (progressors) differed in their ability to inhibit viral replication through targeting of the immunodominant epitope of group-associated antigen (Gag) of HIV-1. This was associated with distinct T cell antigen receptor (TCR) clonotypes, characterized by superior control of HIV-1 replication in vitro, greater cross-reactivity to epitope variants and enhanced loading and delivery of perforin. We also observed clonotype-specific differences in antiviral efficacy for an immunodominant HLA-B57-restricted response in controllers and progressors. Thus, the efficacy of such so-called 'protective alleles' is modulated by specific TCR clonotypes selected during natural infection, which provides a functional explanation for divergent HIV-1 outcomes.
Nearly 90% of flowering plants depend on animals for reproduction. One of the main rewards plants offer to pollinators for visitation is nectar.
(Campanulaceae) produces a blood-red nectar that has ...been proposed to serve as a visual attractant for pollinator visitation. Here, we show that the nectar's red color is derived from a previously undescribed alkaloid termed nesocodin. The first nectar produced is acidic and pale yellow in color, but slowly becomes alkaline before taking on its characteristic red color. Three enzymes secreted into the nectar are either necessary or sufficient for pigment production, including a carbonic anhydrase that increases nectar pH, an aryl-alcohol oxidase that produces a pigment precursor, and a ferritin-like catalase that protects the pigment from degradation by hydrogen peroxide. Our findings demonstrate how these three enzymatic activities allow for the condensation of sinapaldehyde and proline to form a pigment with a stable imine bond. We subsequently verified that synthetic nesocodin is indeed attractive to
geckos, the most likely pollinators of
We also identify nesocodin in the red nectar of the distantly related and hummingbird-visited
and provide molecular evidence for convergent evolution of this trait. This work cumulatively identifies a convergently evolved trait in two vertebrate-pollinated species, suggesting that the red pigment is selectively favored and that only a limited number of compounds are likely to underlie this type of adaptation.
Eight new sesterterpenoids, alotaketals D (8) and E (9), ansellones D (10), E (11), F (12), and G (13), and anvilones A (14) and B (15), have been isolated from extracts of the marine sponge Phorbas ...sp. collected in Howe Sound British Columbia, and their structures have been elucidated by analysis of NMR and MS data. Ansellone F (12) contains a rare 1,2-3,4-bis-epoxydecalin substructure. Anvilones A (14) and B (15) have an unprecedented tetracylic anvilane terpenoid carbon skeleton. Using a cell culture model of latent HIV-1 infection, ansellone A (3), alotaketal D (8), and anvilone A (14) were found to induce HIV proviral gene expression similar to the control compound prostratin (1), while the known sesterterpenoid alotaketal C (2), isolated from the same extract, was more potent and gave a stronger response than prostratin (1). Like prostratin (1), all of the Phorbas sesterterpenoids with latency reversal agent properties appear to activate protein kinase C signaling.
Impaired HIV-1 Gag, Pol, and Env function has been described in elite controllers (EC) who spontaneously suppress plasma viremia to < 50 RNA copies/mL; however, activity of the accessory protein Nef ...remains incompletely characterized. We examined the ability of 91 Nef clones, isolated from plasma of 45 EC and 46 chronic progressors (CP), to down-regulate HLA class I and CD4, up-regulate HLA class II invariant chain (CD74), enhance viral infectivity, and stimulate viral replication in PBMC.
In general, EC Nef clones were functional; however, all five activities were significantly lower in EC compared to CP. Nef clones from HLA-B*57-expressing EC exhibited poorer CD4 down-regulation function compared to those from non-B*57 EC, and the number of EC-specific B*57-associated Nef polymorphisms correlated inversely with 4 of 5 Nef functions in these individuals.
Results indicate that decreased HIV-1 Nef function, due in part to host immune selection pressures, may be a hallmark of the EC phenotype.
Abstract
Background
The magnitude and durability of immune responses to coronavirus disease 2019 (COVID-19) mRNA vaccines remain incompletely characterized in the elderly.
Methods
Anti-spike ...receptor-binding domain (RBD) antibodies, angiotensin-converting enzyme 2 (ACE2) competition, and virus neutralizing activities were assessed in plasma from 151 health care workers and older adults (range, 24–98 years of age) 1 month following the first vaccine dose, and 1 and 3 months following the second dose.
Results
Older adults exhibited significantly weaker responses than younger health care workers for all humoral measures evaluated and at all time points tested, except for ACE2 competition activity after 1 vaccine dose. Moreover, older age remained independently associated with weaker responses even after correction for sociodemographic factors, chronic health condition burden, and vaccine-related variables. By 3 months after the second dose, all humoral responses had declined significantly in all participants, and remained significantly lower among older adults, who also displayed reduced binding antibodies and ACE2 competition activity towards the Delta variant.
Conclusions
Humoral responses to COVID-19 mRNA vaccines are significantly weaker in older adults, and antibody-mediated activities in plasma decline universally over time. Older adults may thus remain at elevated risk of infection despite vaccination.
COVID-19 mRNA vaccines induce weaker antibody responses in older adults. Age was a significant predictor of spike binding antibody concentration and SARS-CoV-2 neutralizing activity after correcting for participant demographics, including chronic health conditions.
Limited data exist regarding the immune benefits of fourth COVID-19 vaccine doses in people with HIV (PWH) receiving antiretroviral therapy (ART), particularly now that most have experienced a ...SARS-CoV-2 infection. We quantified wild-type, Omicron-BA.5 and Omicron-BQ.1-specific neutralization up to 1 month post-fourth COVID-19 vaccine dose in 63 (19 SARS-CoV-2-naive and 44 SARS-CoV-2-experienced) PWH.
A longitudinal observational cohort.
Quantification of wild-type-, Omicron-BA.5, and Omicron-BQ.1-specific neutralization using live virus assays.
Participants received monovalent (44%) and bivalent (56%) mRNA fourth doses. In COVID-19-naive PWH, fourth doses enhanced wild-type and Omicron-BA.5-specific neutralization modestly above three-dose levels ( P = 0.1). In COVID-19-experienced PWH, fourth doses enhanced wild-type specific neutralization modestly ( P = 0.1) and BA.5-specific neutralization substantially ( P = 0.002). Consistent with humoral benefits of 'hybrid' immunity, COVID-19-experienced PWH exhibited the highest neutralization post-fourth dose, wherein those with Omicron-era infections displayed higher wild-type specific ( P = 0.04) but similar BA.5 and BQ.1-specific neutralization than those with pre-Omicron-era infections. Nevertheless, BA.5-specific neutralization was significantly below wild-type in everyone regardless of COVID-19 experience, with BQ.1-specific neutralization lower still (both P < 0.0001). In multivariable analyses, fourth dose valency did not affect neutralization magnitude. Rather, an mRNA-1273 fourth dose (versus a BNT162b2 one) was the strongest correlate of wild-type specific neutralization, while prior COVID-19, regardless of pandemic era, was the strongest correlate of BA.5 and BQ.1-specific neutralization post-fourth dose.
Fourth COVID-19 vaccine doses, irrespective of valency, benefit PWH regardless of prior SARS-CoV-2 infection. Results support recommendations that all adults receive a fourth COVID-19 vaccine dose within 6 months of their third dose (or their most recent SARS-CoV-2 infection).
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