COVID-19 antibody testing: From hype to immunological reality.

The potential role for serological tests in the current COVID-19 pandemic has generated very considerable recent interest across many sectors worldwide, inter alia pathologists seeking additional weapons for their armoury of diagnostic tests; epidemiologists seeking tools to gain seroprevalence data that will inform improved models of the spread of disease; research scientists seeking tools to study the natural history of COVID-19 disease; vaccine developers seeking tools to assess vaccine efficacy in clinical trials; and companies and governments seeking tools to aid return-to-work decision-making. However, much of the local debate to date has centred on questions surrounding whether regulatory approval processes are limiting access to serological tests, and has not paused to consider the intrinsically limiting impact of underlying fundamental biology and immunology on where and how different COVID-19 serological tests can usefully be deployed in the response to the current pandemic. We review, from an immunological perspective, recent experimental evidence on the time-dependency of adaptive immune responses following SARS-CoV-2 infection and the impact of this on the sensitivity and specificity of COVID-19 antibody tests made at different time points post infection. We interpret this scientific evidence in terms of mooted clinical applications for current COVID-19 antibody tests in identifying acute infections, in confirming recent or past infections at the individual and population level, and in detecting re-infection and protective immunity. We conclude with guidance on where current COVID-19 antibody tests can make a genuine impact in the pandemic.

National expenditure on health research in South Africa: How has the landscape changed in the past decade?

BACKGROUND: Over the past 18 years, the South African (SA) Ministry of Health has committed to allocate 2% of the national health budget to research, while the National Health Research Policy (2001) proposed that the health research budget should be 2% of total public sector health expenditure. A review was conducted by the National Health Research Committee (NHRC) in 2014 to determine whether these goals had been met, using available data up to 2009/10. It revealed that public sector health research funding remained below 2% of the national health budget, supporting the perception of reduced public sector health research funding. OBJECTIVES: To provide an update on the previous review to investigate changes in the health research landscape since 2009/10 and whether goals have been met. METHODS: Various publicly available sources of information on public and private expenditure on health research in SA were used to investigate health research funding and expenditure. In addition, questionnaires were sent to 35 major national and international funders of health research in SA to obtain data on the level of funding provided and the fields of research funded. RESULTS: Total health research expenditure in SA was ZAR6.9 billion in 2016/17, or 19.2% of gross expenditure on research and development, with 1.7% of the ZAR38.6 billion National Department of Health budget from National Treasury being spent on health research through the South African Medical Research Council (ZAR658 million), corresponding to 0.4% of the consolidated government expenditure on health. However, although the total government plus science council spend on health research in 2016/17 was ZAR1.45 billion, this represents just 0.033% of the gross domestic product (GDP), thus remaining well below the aspirational target of 0.15% of the GDP set by the NHRC in 2014. Based on feedback from the funders, the estimated baseline health research funding in 2016/17 was in excess of ZAR4.1 billion, which is considerably higher than many researchers may realise. Three-quarters of this funding originated from foreign sources, suggesting both strengths and opportunities for health research in SA, but also highlighting increasing dependence on foreign funding. Notably, the majority of funders approached were not able to readily break down expenditure according to disease area. CONCLUSIONS: Health research funding has changed significantly since our previous review, although the government's own commitments to it remain unmet. Improved mechanisms to track health research expenditure are urgently required for better alignment of funding priorities and increased co-ordination between science councils in health research funding.

Mutational analysis of the kinetics and thermodynamics of transcription factor NF-kappaB homodimerisation.

Dimeric transcription factors of the NF-kappaB/Rel family are sequence-specific DNA-binding proteins that mediate the inducible expression of immunologically important eukaryotic genes by competing for kappaB sites. The kinetic and thermodynamic components of these interactions were probed by mutation of the subunit interface of the p50 homodimer, a paradigm for other family members. Guided by the crystal structure, we selected the side chains of five key residues (R255, Y270, L272, A311 and V313) for individual and combinatorial truncation, with the aim of generating a mutant panel. Homodimerisation was assessed indirectly by measurement of DNA binding with an optical biosensor in order to unmask the relative contributions of each residue. Surface plasmon resonance revealed that a unanimous bias for a palindromic kappaB site over an asymmetric one was mainly the result of a slower dissociation rate for the DNA/homodimer complex in the case of the palindromic kappaB site. Y270 and L272 were individually the most critical residues in homodimerisation. DNA binding was abolished when all five residues were substituted, which reinforces the notion that only a subset of residues contributes crucial dimer-forming contacts. The role of Y270 was unique, since its mutation to glycine dramatically slowed both the association and dissociation rates for DNA binding. Surprisingly, R255 was shown to be of little importance in the stability of the p50 homodimer, despite its apparent participation in a salt bridge at the dimer interface. Our results suggest that binding modes inferred from structural data should be treated cautiously.

A new plasmid display technology for the in vitro selection of functional phenotype-genotype linked proteins.

BACKGROUND: Display technologies which allow peptides or proteins to be physically associated with the encoding DNA are central to procedures which involve screening of protein libraries in vitro for new or altered function. Here we describe a new system designed specifically for the display of libraries of diverse, functional proteins which utilises the DNA binding protein nuclear factor kappa B (NF-kappa B) p50 to establish a phenotype-genotype link between the displayed protein and the encoding gene. RESULTS: A range of model fusion proteins to either the amino- or carboxy-terminus of NF-kappa B p50 have been constructed and shown to retain the picomolar affinity and DNA specificity of wild-type NF-kappa B p50. Through use of an optimal combination of binding buffer and DNA target sequence, the half-life of p50-DNA complexes could be increased to over 47 h, enabling the competitive selection of a variety of protein-plasmid complexes with enrichment factors of up to 6000-fold per round. The p50-based plasmid display system was used to enrich a maltose binding protein complex to homogeneity in only three rounds from a binary mixture with a starting ratio of 1:10(8) and to enrich to near homogeneity a single functional protein from a phenotype-genotype linked Escherichia coli genomic library using in vitro functional selections. CONCLUSIONS: A new display technology is described which addresses the challenge of functional protein display. The results demonstrate that plasmid display is sufficiently sensitive to select a functional protein from large libraries and that it therefore represents a useful addition to the repertoire of display technologies.

Direct and quantitative detection of bacteriophage by "hearing" surface detachment using a quartz crystal microbalance.

We show that it is possible to detect specifically adsorbed bacteriophage directly by breaking the interactions between proteins displayed on the phage coat and ligands immobilized on the surface of a quartz crystal microbalance (QCM). This is achieved through increasing the amplitude of oscillation of the QCM surface and sensitively detecting the acoustic emission produced when the bacteriophage detaches from the surface. There is no interference from nonspecifically adsorbed phage. The detection is quantitative over at least 5 orders of magnitude and is sensitive enough to detect as few as 20 phage. The method has potential as a sensitive and low-cost method for virus detection.

Deposition of conformal copper and nickel films from supercritical carbon dioxide.

Device-quality copper and nickel films were deposited onto planar and etched silicon substrates by the reduction of soluble organometallic compounds with hydrogen in a supercritical carbon dioxide solution. Exceptional step coverage on complex surfaces and complete filling of high-aspect-ratio features of less than 100 nanometers width were achieved. Nickel was deposited at 60 degrees C by the reduction of bis(cyclopentadienyl)nickel and copper was deposited from either copper(I) or copper(II) compounds onto the native oxide of silicon or metal nitrides with seed layers at temperatures up to 200 degrees C and directly on each surface at temperatures above 250 degrees C. The latter approach provides a single-step means for achieving high-aspect-ratio feature fill necessary for copper interconnect structures in future generations of integrated circuits.

Analysis of the NF-kappaB p50 dimer interface by diversity screening.

An in vivo screen has been devised for NF-kappaB p50 activity in Escherichia coli exploiting the ability of the mammalian transcription factor to emulate a prokaryotic repressor. Active intracellular p50 was shown to repress the expression of a green fluorescent protein reporter gene allowing for visual screening of colonies expressing active p50 on agar plates. A library of mutants was constructed in which the residues Y267, L269, A308 and V310 of the dimer interface were simultaneously randomised and twenty-five novel functional interfaces were selected which repressed the reporter gene to similar levels as the wild-type protein. The leucine-269 alanine-308 core was repeatedly, but not exclusively, selected from the library whilst a diversity of predominantly non-polar residues were selected at positions 267 and 310. These results indicate that L269 and A308 may form a hot spot of interaction and allow an insight into the processes of dimer selectivity and evolution within this family of transcription factors.

Directed evolution of new catalytic activity using the alpha/beta-barrel scaffold.

In biological systems, enzymes catalyse the efficient synthesis of complex molecules under benign conditions, but widespread industrial use of these biocatalysts depends crucially on the development of new enzymes with useful catalytic functions. The evolution of enzymes in biological systems often involves the acquisition of new catalytic or binding properties by an existing protein scaffold. Here we mimic this strategy using the most common fold in enzymes, the alpha/beta-barrel, as the scaffold. By combining an existing binding site for structural elements of phosphoribosylanthranilate with a catalytic template required for isomerase activity, we are able to evolve phosphoribosylanthranilate isomerase activity from the scaffold of indole-3-glycerol-phosphate synthase. We find that targeting the catalytic template for in vitro mutagenesis and recombination, followed by in vivo selection, results in a new phosphoribosylanthranilate isomerase that has catalytic properties similar to those of the natural enzyme, with an even higher specificity constant. Our demonstration of divergent evolution and the widespread occurrence of the alpha/beta-barrel suggest that this scaffold may be a fold of choice for the directed evolution of new biocatalysts.

The salt dependence of DNA recognition by NF-kappaB p50: a detailed kinetic analysis of the effects on affinityand specificity.

The binding kinetics of NF-kappaB p50 to the Ig-kappaB site and to a DNA duplex with no specific binding site were determined under varying conditions of potassium chloride concentration using a surface plasmonresonance biosensor. Association and dissociation rate constants were measured enabling calculation of the dissociation constants. Under previously established high affinity buffer conditions, the k a for both sequences was in the order of 10(7) M-1s-1whilst the k d values varied 600-fold in a sequence-dependent manner between 10(-1) and 10(-4 )s-1, suggesting that the selectivity of p50 for different sequences is mediated primarily through sequence-dependent dissociation rates. The calculated K D value for the Ig-kappaB sequence was 16 pM, whilst the K D for the non-specific sequence was 9.9 nM. As the ionic strength increased to levels which are closer to that of the cellular environment, the binding of p50 to the non-specific sequence was abolished whilst the specific affinity dropped to nanomolar levels. From these results, a mechanism is proposed in which p50 binds specific sequences with high affinity whilst binding non-specific sequences weakly enough to allow efficient searching of the DNA.

Killing two birds with one stone: a chemically plausible scheme for linked nucleic acid replication and coded peptide synthesis.

To understand how life began, we must explain the origins of nucleic acid replication and genetically coded peptide synthesis. Neither of these is easy to explain individually; here, we propose a chemically plausible scheme for the evolution of a process that simultaneously produced both polymers. Later, two separate machineries could have evolved from the linked process.

Incorporation of glutamine repeats makes protein oligomerize: implications for neurodegenerative diseases.

Many transcription factors and some other proteins contain glutamine repeats; their abnormal expansion has been linked to several dominantly inherited neuro-degenerative diseases. Having found that poly(L-glutamine) alone forms beta-strands held together by hydrogen bonds between their amide groups, we surmised that glutamine repeats may form polar zippers, an unusual motif for protein-protein interactions. To test this hypothesis, we have engineered a Gly-Gln10-Gly peptide into the inhibitory loop of truncated chymotrypsin inhibitor 2 (CI2), a small protein from barley seeds, by both insertion and replacement. Gel filtration resolved both mutant inhibitors into at least three fractions, which analytical ultracentrifugation identified as monomers, dimers, and trimers of the recombinant protein; the truncated wild-type CI2 formed only monomers. CD difference spectra of the dimers and trimers versus wild type indicated that their glutamine repeats formed beta-pleated sheets, while those of the monomers versus wild type were more suggestive of type I beta-turns. The CD spectra of all three fractions remained unchanged even after incubation at 70 degrees C; neither the dimers nor the trimers dissociated at this temperature. We argue that the stability of all three fractions is due to the multiplicity of hydrogen bonds between extended strands of glutamine repeats in the oligomers or within a beta-hairpin formed by the single glutamine repeat of each monomer. Pathological effects may arise when expanded glutamine repeats cause proteins to acquire excessively high affinities for each other or for other proteins with glutamine repeats.

A heuristic approach to the analysis of enzymic catalysis: reaction of delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-alpha-aminobutyrate and delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-allylglycine catalyzed by isopenicillin N synthase isozymes.

Isopenicillin N synthase (IPNS) catalyzes the oxidative cyclization of delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine to isopenicillin N. It is proposed that the multiple products produced from certain substrate analogues result from pathway branching after formation of a ferryl oxene intermediate. We have been interested in ascertaining the reasons for multiple product formation. One possibility is that the products are predisposed toward formation once the beta-lactam ring and the ferryl oxene are produced. Alternately, the products may be persuaded into being by the enzyme restricting conformations such that otherwise less favorable chemistry can take place. With the existing description of the IPNS catalytic cycle, this fundamental question has not been answerable. We describe here the application of a heuristic method to resolve this key issue. It was reasoned that by comparing the ratios of products formed by a set of perturbed IPNS variants it might be possible to generate qualitative information about the relative magnitude of certain activation parameters. If certain product ratios are affected but others are not, then it should be possible to say which steps in the reaction are dictated merely by chemical fundamentals and which steps are directly effected by the enzyme. In this paper we report the high-level expression, purification, and characterization of four IPNS isozymes. Comparison of the product ratios obtained on incubation of unnatural substrate analogues with four IPNS isozymes corresponding to perturbed active site variants shows substantial variation in some cases and little in others. Interpretation of the results obtained with delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-alpha-aminobutyrate (ACAB) allows conclusions to be drawn regarding the role of the enzyme in restricting available conformations of the natural substrate to disfavor certain otherwise chemically favorable pathways and hence products. The results obtained with delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-allylglycine, while rather more complex, substantiate the conclusions drawn from the ACAB data. A major conclusion is that, in the oxidation of ACV, IPNS is a negative catalyst of cepham formation but a positive catalyst of penam formation.

High level expression in Escherichia coli of a fungal gene under the control of strong promoters.

A recent report (Patino et al., (1989) FEMS Microbiol. Lett. 58, 139-144) described the low level expression, in Escherichia coli, of the Isopenicillin N Synthase (IPNS) gene from Cephalosporium acremonium under the control of strong promoters. We report here our work on the expression of the IPNS gene. Plasmids containing the IPNS gene under the control of the trp or trc promoters directed synthesis of high levels of active IPNS in E. coli. Constitutive and inductive high level IPNS expression systems have been developed. Importantly, the expression vectors do not encode beta-lactamase so IPNS activity can be determined directly by biological assays. Analysis by nmr verified that the IPNS produced from these expression systems catalysed the conversion of delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (LLD-ACV) to isopenicillin N in high yield.

Marketing audit in group practice.

The marketing audit, whether large-scale or small-scale, will soon be critical to the success of every medical group practice. This dynamic process, in which the many components of a group's marketing efforts are analyzed, is examined from the perspective of ideal circumstances and unlimited resources, and more pragmatically, from the perspective of various-sized groups, with different resources and marketing talent. The audit components are prioritized, possible adaptations and combinations are presented, and reasonable implementation mechanisms, designed to address audit outcomes, are suggested.