In-depth immune profiling reveals advanced B- and T-cell differentiation to be associated with Th1-driven immune dysregulation in common variable immunodeficiency

Common variable immunodeficiency (CVID) is an inborn error of immunity characterized by low levels of antibodies. In addition to infections, many patients also suffer from T-helper 1-driven immune dysregulation, which is associated with increased mortality. The aim of this study was to perform in-depth characterization of the T and the B cell compartments in a well-defined cohort of patients affected by CVID and correlate the findings to the level of clinical immune dysregulation. We used mass cytometry, targeted proteomics, flow cytometry and functional assays to delineate the immunological phenotype of 15 CVID-affected patients with different levels of immune dysregulation. Unbiased clustering of T cell mass cytometry data correlated with CVID-related immune dysregulation and plasma protein profiles. Expanded CXCR3+ T-bet-expressing B cells correlated with effector memory CD4+ T cell clusters, and increased plasma levels of CXCR3-ligands. Our findings indicate an interplay between B cells and T cells in CVID-related immune dysregulation and provide a better understanding of the underlying pathological mechanisms.

Pentameric C-reactive protein is a better prognostic biomarker and remains elevated for longer than monomeric CRP in hospitalized patients with COVID-19

The differing roles of the pentameric (p) and monomeric (m) C-reactive protein (CRP) isoforms in viral diseases are not fully understood, which was apparent during the COVID-19 pandemic regarding the clinical course of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Herein, we investigated the predictive value of the pCRP and mCRP isoforms for COVID-19 severity in hospitalized patients and evaluated how the levels of the protein isoforms changed over time during and after acute illness. This study utilized samples from a well-characterized cohort of Swedish patients with SARS-CoV-2 infection, the majority of whom had known risk factors for severe COVID-19 and required hospitalization. The levels of pCRP were significantly raised in patients with severe COVID-19 and in contrast to mCRP the levels were significantly associated with disease severity. Additionally, the pCRP levels remained elevated for at least six weeks post inclusion, which was longer compared to the two weeks for mCRP. Our data indicates a low level of inflammation lasting for at least six weeks following COVID-19, which might indicate that the disease has an adverse effect on the immune system even after the viral infection is resolved. It is also clear that the current standard method of testing pCRP levels upon hospitalization is a useful marker for predicting disease severity and mCRP testing would not add any clinical relevance for patients with COVID-19.

Adult corrosive ingestions in the Pietermaritzburg Metropolitan Surgical Service

BACKGROUND

There is a paucity of data around corrosive ingestion in South Africa over the last three decades. As such, we set out to review our experience with adult corrosive ingestion in our tertiary gastrointestinal surgical service.

METHODS

A retrospective, quantitative review was performed. The parameters analysed were demographics, substance ingestion, ingestion time to first presentation to a healthcare facility, clinical presentation, severity of injury based on endoscopic classification, computed tomography (CT) findings, management and outcomes. Patients presenting within 72 hours with alarm symptoms underwent flexible upper endoscopy and injury severity grading. In patients presenting after 72 hours, a water-soluble contrast study was obtained prior to upper endoscopy. Patients with signs of sepsis, surgical emphysema or physiological instability were referred for urgent CT to exclude oesophageal perforation and mediastinitis.

RESULTS

Between January 2012 and January 2019, a total of 64 patients presented with a history of corrosive ingestion - 40 (31%) were males and 24 (19%) females. The average time from ingestion to presentation was 72 hours. In 78% of patients, the agents were intentionally ingested, whilst 22% claimed accidental ingestion. A quarter of the patients (21%) presented to the unit clinically unstable, requiring emergent cardiorespiratory support. Eight (12%) patients required urgent surgical intervention due to the extent of injury. Nine (14%) patients demised during the acute admission. Of this group, three patients had undergone surgical intervention, and six were managed conservatively. Eighty-five per cent of all patients survived their initial admission.

CONCLUSION

This paper has highlighted the problem of corrosive ingestion in our setting. It remains a complicated problem to manage associated with significant morbidity and mortality rates. The current trend in the assessment of these patients is increased use of CT scan to assess the extent of transmural necrosis. Our algorithms should change to reflect this contemporary approach.

Conformational state of C-reactive protein is critical for reducing immune complex-triggered type I interferon response: Implications for pathogenic mechanisms in autoimmune diseases imprinted by type I interferon gene dysregulation

Presence of autoantibodies targeting nuclear constituents, i.e., double-stranded DNA and small nuclear ribonucleoproteins (snRNPs), remain a cornerstone in systemic lupus erythematosus (SLE). Fcγ receptor IIa (FcγRIIa) dependent uptake of nucleic acid containing immune complexes (ICs) by plasmacytoid dendritic cells (PDCs) can activate toll-like receptors (TLRs) such as TLR7 and TLR9 resulting in type I interferon (IFN) production. Previously, the classical liver-derived acute-phase reactant C-reactive protein (CRP) has been suggested to reduce IC-induced type I IFN production, whereas monomeric (mCRP) vs. pentameric (pCRP) mediated effects have not yet been unraveled. Herein, peripheral blood mononuclear cells (PBMCs) or enriched blood DCs from healthy volunteers were stimulated with SLE sera, snRNP-IgG (ICs), or TLR ligands with or without pCRP, mCRP, or anti-FcγRIIa antibody. Type I IFNs and cytokine responses were investigated using quantitative PCR, ELISA, and flow cytometry. pCRP inhibited IFN gene expression in PBMCs and enriched DCs after incubation with ICs, compared to ICs alone, whereas mCRP had significantly less inhibitory effect. The effect was independent on the order in which IC or CRP was added to the cells. In addition, pCRP inhibited IFN induced by other TLR stimulators, implicating broader inhibitory effects induced by pCRP. We demonstrate pronounced immunoregulatory functions of CRP whereas the inhibitory properties were evidently dependent on CRP's intact conformational state. The inhibition of type I IFNs was not due to competition of FcγRs, or binding of CRP to the ICs. Our findings have implications for autoimmune IC-mediated conditions imprinted by type I IFN gene dysregulation.

Major alterations to monocyte and dendritic cell subsets lasting more than 6 months after hospitalization for COVID-19

Introduction

After more than two years the Coronavirus disease-19 (COVID-19) pandemic continues to burden healthcare systems and economies worldwide, and it is evident that the effects on the immune system can persist for months post-infection. The activity of myeloid cells such as monocytes and dendritic cells (DC) is essential for correct mobilization of the innate and adaptive responses to a pathogen. Impaired levels and responses of monocytes and DC to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is likely to be a driving force behind the immune dysregulation that characterizes severe COVID-19.

Methods

Here, we followed a cohort of COVID-19 patients hospitalized during the early waves of the pandemic for 6-7 months. The levels and phenotypes of circulating monocyte and DC subsets were assessed to determine both the early and long-term effects of the SARS-CoV-2 infection.

Results

We found increased monocyte levels that persisted for 6-7 months, mostly attributed to elevated levels of classical monocytes. Myeloid derived suppressor cells were also elevated over this period. While most DC subsets recovered from an initial decrease, we found elevated levels of cDC2/cDC3 at the 6-7 month timepoint. Analysis of functional markers on monocytes and DC revealed sustained reduction in program death ligand 1 (PD-L1) expression but increased CD86 expression across almost all cell types examined. Finally, C-reactive protein (CRP) correlated positively to the levels of intermediate monocytes and negatively to the recovery of DC subsets.

Conclusion

By exploring the myeloid compartments, we show here that alterations in the immune landscape remain more than 6 months after severe COVID-19, which could be indicative of ongoing healing and/or persistence of viral antigens.

HIV-1 induction of tolerogenic dendritic cells is mediated by cellular interaction with suppressive T cells

HIV-1 infection gives rise to a multi-layered immune impairment in most infected individuals. The chronic presence of HIV-1 during the priming and activation of T cells by dendritic cells (DCs) promotes the expansion of suppressive T cells in a contact-dependent manner. The mechanism behind the T cell side of this HIV-induced impairment is well studied, whereas little is known about the reverse effects exerted on the DCs. Herein we assessed the phenotype and transcriptome profile of mature DCs that have been in contact with suppressive T cells. The HIV exposed DCs from cocultures between DCs and T cells resulted in a more tolerogenic phenotype with increased expression of e.g., PDL1, Gal-9, HVEM, and B7H3, mediated by interaction with T cells. Transcriptomic analysis of the DCs separated from the DC-T cell coculture revealed a type I IFN response profile as well as an activation of pathways involved in T cell exhaustion. Taken together, our data indicate that the prolonged and strong type I IFN signaling in DCs, induced by the presence of HIV during DC-T cell cross talk, could play an important role in the induction of tolerogenic DCs and suppressed immune responses seen in HIV-1 infected individuals.

T cell perturbations persist for at least 6 months following hospitalization for COVID-19

COVID-19 is being extensively studied, and much remains unknown regarding the long-term consequences of the disease on immune cells. The different arms of the immune system are interlinked, with humoral responses and the production of high-affinity antibodies being largely dependent on T cell immunity. Here, we longitudinally explored the effect COVID-19 has on T cell populations and the virus-specific T cells, as well as neutralizing antibody responses, for 6-7 months following hospitalization. The CD8⁺ TEMRA and exhausted CD57⁺ CD8⁺ T cells were markedly affected with elevated levels that lasted long into convalescence. Further, markers associated with T cell activation were upregulated at inclusion, and in the case of CD69⁺ CD4⁺ T cells this lasted all through the study duration. The levels of T cells expressing negative immune checkpoint molecules were increased in COVID-19 patients and sustained for a prolonged duration following recovery. Within 2-3 weeks after symptom onset, all COVID-19 patients developed anti-nucleocapsid IgG and spike-neutralizing IgG as well as SARS-CoV-2-specific T cell responses. In addition, we found alterations in follicular T helper (TFH) cell populations, such as enhanced TFH-TH2 following recovery from COVID-19. Our study revealed significant and long-term alterations in T cell populations and key events associated with COVID-19 pathogenesis.

Soluble Urokinase Plasminogen Activator Receptor (suPAR) Independently Predicts Severity and Length of Hospitalisation in Patients With COVID-19

Background: Efficient healthcare based on prognostic variables in hospitalised patients with COVID-19 could reduce the risk of complications and death. Recently, soluble urokinase Plasminogen Activator Receptor (suPAR) was shown to predict respiratory failure, kidney injury, and clinical outcome in patients with SARS-CoV-2 infection. The aim of this study was to investigate the value of suPAR as a prognostic tool, in comparison with other variables, regarding disease severity and length of hospital stay in patients with COVID-19. Patients and Methods: Individuals hospitalised with COVID-19 (40 males, 20 females; median age 57.5 years) with a median symptom duration of 10 days and matched, healthy controls (n = 30) were included. Admission levels of suPAR were measured in serum by enzyme-linked immunosorbent assay. Blood cell counts, C-reactive protein (CRP) levels, lactate dehydrogenase (LDH), plasma creatinine and estimated glomerular filtration rates were analysed and oxygen demand, level of care and length of hospitalisation recorded. Results: Patients had significantly higher suPAR levels compared to controls (P < 0.001). Levels were higher in severely/critically (median 6.6 ng/mL) compared with moderately ill patients (median 5.0 ng/mL; P = 0.002). In addition, suPAR levels correlated with length of hospitalisation (rho = 0.35; P = 0.006). Besides suPAR, LDH, CRP, neutrophil count, neutrophil-to-monocyte and neutrophil-to-lymphocyte ratio, body mass index and chronic renal failure were discriminators of COVID-19 severity and/or predictors of length of hospitalisation. Conclusion: Admission levels of suPAR were higher in patients who developed severe/critical COVID-19 and associated with length of hospital stay. In addition, we showed that suPAR functioned as an independent predictor of COVID-19 disease severity.

HIV-Infected Individuals on ART With Impaired Immune Recovery Have Altered Plasma Metabolite Profiles

Background

Multiple host factors may influence immune reconstitution in HIV-infected people after the initiation of suppressive antiretroviral therapy (ART). Aberrant metabolic pathways have been reported in people with HIV (PWH) on ART. We hypothesized that alterations in plasma metabolites were associated with immune recovery following ART.

Methods

In this cross-sectional study, the plasma metabolomic profiles of PWH on ART were evaluated. PWH of slow and fast immune recovery were classified by increase in CD4 T cells following 2 years of ART. Targeted plasma metabolite profiling by liquid chromatography–mass spectrometry and gas chromatography–mass spectrometry to determine metabolite signatures for HIV recovery identified >200 metabolites.

Results

Notably, indole-3-propionic acid was downregulated during HIV, possibly reflecting impaired gastrointestinal epithelium homeostasis. The most important metabolite discriminating between the PWH with fast and slow immune recovery was cysteine. Upregulated cysteine and cysteine pathways may contribute to redox-balance maintenance and T-cell function in PWH with fast immune recovery. Additionally, serine and glycine metabolism and bile acid biosynthesis were the most perturbed metabolic pathways in PWH.

Conclusions

These results provide a starting point for developing biomarker candidates for immune recovery in PWH on ART and provide insight into the interplay of metabolism and immune response in HIV infection.

Complement opsonization of HIV affects primary infection of human colorectal mucosa and subsequent activation of T cells

HIV transmission via genital and colorectal mucosa are the most common routes of dissemination. Here, we explored the effects of free and complement-opsonized HIV on colorectal tissue. Initially, there was higher antiviral responses in the free HIV compared to complement-opsonized virus. The mucosal transcriptional response at 24 hr revealed the involvement of activated T cells, which was mirrored in cellular responses observed at 96 hr in isolated mucosal T cells. Further, HIV exposure led to skewing of T cell phenotypes predominantly to inflammatory CD4+ T cells, that is Th17 and Th1Th17 subsets. Of note, HIV exposure created an environment that altered the CD8+ T cell phenotype, for example expression of regulatory factors, especially when the virions were opsonized with complement factors. Our findings suggest that HIV-opsonization alters the activation and signaling pathways in the colorectal mucosa, which promotes viral establishment by creating an environment that stimulates mucosal T cell activation and inflammatory Th cells.

Avoiding the diagnostic pitfalls of a pancreatic cystic lesion

Cystic pancreatic lesions present a diagnostic challenge. Accurate characterisation of an isolated cystic pancreatic lesion is therefore vital as this dictates the management strategy which may vary from radical resection to simple observation. This report describes how a detailed preoperative assessment led to the correct diagnosis of an isolated pancreatic lesion and appropriate safe and curative surgical management.

IL-4Rα Signaling in Keratinocytes and Early IL-4 Production Are Dispensable for Generating a Curative T Helper 1 Response in Leishmania major-Infected C57BL/6 Mice

Experimental infection with the protozoan parasite Leishmania major has been extensively used to understand the mechanisms involved in T helper cell differentiation. Following infection, C57BL/6 mice develop a small self-healing cutaneous lesion and they are able to control parasite burden, a process linked to the development of T helper (Th) 1 cells. The local presence of IL-12 has been reported to be critical in driving Th1 cell differentiation. In addition, the early secretion of IL-4 was reported to potentially contribute to Th1 cell differentiation. Following infection with L. major, early keratinocyte-derived IL-4 was suggested to contribute to Th1 cell differentiation. To investigate a putative autocrine role of IL-4 signaling on keratinocytes at the site of infection, we generated C57BL/6 mice deficient for IL-4Rα expression selectively in keratinocytes. Upon infection with L. major, these mice could control their inflammatory lesion and parasite load correlating with the development of Th1 effector cells. These data demonstrate that IL-4 signaling on keratinocytes does not contribute to Th1 cell differentiation. To further investigate the source of IL-4 in the skin during the first days after L. major infection, we used C57BL/6 IL-4 reporter mice allowing the visualization of IL-4 mRNA expression and protein production. These mice were infected with L. major. During the first 3 days after infection, skin IL-4 mRNA expression was observed selectively in mast cells. However, no IL-4 protein production was detectable locally. In addition, early IL-4 blockade locally had no impact on subsequent Th1 cell differentiation and control of the disease. Taken together, the present data rule out a major role for skin IL-4 and keratinocyte IL-4Rα signaling in the development of a Th1 protective immune response following experimental infection with L. major.

Self-Expanding Metal Stent (SEMS) insertion: Fluoroscopy versus pure endoscopic technique - A cost comparison

Oesophageal cancer is a disease with significant morbidity and mortality, and in South Africa most patients present with advanced disease.1 Self-expanding metal stents (SEMS) are now widely used in the palliation of oesophageal cancer, and in most institutions SEMS are deployed under fluoroscopic guidance. In our institution, we use an exclusive endoscopic deployment technique which is comparable to the traditional fluoroscopic technique in terms of safety and efficacy.2-4 We undertook a study to compare the two techniques with respect to their time- and cost-effectiveness.

It's not inside, it's on top! - An unusual cause of right iliac fossa pain

Rectus sheath haematoma (RSH) is an uncommon cause of acute abdominal pain, but can mimic a variety of acute surgical conditions. Computed tomography (CT) provides the diagnosis and avoids unnecessary procedures.

Practices employed by audiologists in the management of adult patients with multidrug-resistant tuberculosis in South Africa

Introduction: Aminoglycosides used for treating multidrug-resistant (MDR) tuberculosis are ototoxic, leading to a need for audiological monitoring. While audiologists monitor ototoxicity, currently there are no guidelines on monitoring in the South African context. Therefore, the findings of this study might help to motivate the establishment of a more in-depth ototoxicity monitoring policy, which facilitates uniformity among audiologists managing patients with MDR tuberculosis. Therefore, the study aimed to describe the audiological practices employed by audiologists in the management of adult patients with MDR tuberculosis in South Africa.Method: A descriptive survey design was used. A questionnaire was developed and included elements of the American Speech-Language and Hearing Association (1994) guidelines for monitoring ototoxicity. Ninety-three audiologists contributed data to this study. Descriptive statistics were used in the analysis of the data.Results: Sixty-eight percent (%) of the respondents were aware of the international guidelines, 93% provided pre-treatment counselling and 87% conducted a baseline assessment. Nineteen per cent of the respondents conducted high-frequency audiometry, while 74% carried out a monthly evaluation, 72% performed a full audiological assessment after the cessation of the MDR tuberculosis treatment, and 96% conducted post-treatment counselling. Modifications to the international guidelines include not conducting speech and immittance audiometry, as well as testing certain frequencies. The reasons for these modifications include limited specialised equipment, time constraints, large caseloads and understaffed departments.Conclusion: There are no explicit guidelines on ototoxicity monitoring in South Africa. Consequently, audiologists are having to modify the international guidelines. Thus, there is no consistency in managing patients with MDR tuberculosis. This highlights the need for South Africa to develop context-relevant ototoxicity monitoring guidelines to appropriately manage patients with MDR tuberculosis.

Current management of large bowel injuries and factors influencing outcome

BACKGROUND

Colonic and intra-peritoneal rectal injuries may be managed by primary repair and extra-peritoneal rectal injuries by diverting colostomy. This study was undertaken to document our experience with this approach and to identify factors which might impact on outcome.

PATIENTS AND METHODS

Prospective study of all patients treated for colon and rectal injuries in one surgical ward at King Edward VIII hospital, Durban, over a 7-year period (1998-2004). Demographic data, clinical presentation, findings at laparotomy and outcome were documented.

RESULTS

Of 488 patients undergoing laparotomy, 177 (36%) had injuries to the colon and rectum with age 29.8+/-10.9 years. Injury mechanisms were firearms (118) stabs (54) and blunt trauma (5). Delay before laparotomy was 10+/-9.3 h. Complication and mortality rates were 36% and 17%, respectively. 68 patients (38%) required ICU management. Shock on admission and increased transfusion requirements were associated with a significantly increased mortality. Patients with delay < or = 12 h before laparotomy had a higher mortality rate than those with delay >12 h. The mortality rate increased with the number of associated injuries and it was higher the higher the Injury Severity Score (ISS); it was similar for stabs, firearms and blunt trauma. Hospital stay was 9.5+/-9.2 days.

CONCLUSION

We reaffirm that primary repair is appropriate for colonic and intra-peritoneal rectal injuries and that extra-peritoneal rectal injuries require diverting colostomy. Shock on admission, increased blood transfusion requirements, associated organ injury and severity of the injury were associated with high mortality.

Post-dispensing stability surveillance: Stavudine

Background

Stavudine, a thymidine nucleoside, is a reverse transcriptase inhibitor, which is extensively used in the treatment of HIV infected patients. According to the World Health Organization (2006), stavudine must be stored in well closed containers and be protected from light. In addition, the manufacturer recommends that stavudine be stored below 25°C in a tightly closed container. However, because of the stigma associated with the disease condition, patients may attempt to hide their medication by storing the drug in more anonymous packaging, which may not comply with these storage requirements. Furthermore, the high temperature and humidity conditions found in sub-tropical areas such as Durban, KwaZulu-Natal, place additional environmental stress on the drug. Research has shown that stavudine can degrade to thymine under hydrolytic, oxidative and photolytic conditions. Therefore, this study investigated the stability of stavudine in packaging other than that used by the manufacturer and under temperature and humidity conditions that were higher than those recommended by the manufacturer.

Method

Stavudine capsules were placed in different types of packaging and then subjected to different temperature and humidity conditions. At two week intervals the capsules were analysed using HPLC (high pressure liquid chromatography).

Results

Stavudine capsules stored in packaging other than that used by the manufacturer and under temperature and humidity conditions that are higher than those recommended by the manufacturer showed significant degradation.

Conclusion

Patients taking stavudine stored under sub-optimal conditions may ingest less than the required dose of stavudine. This can lead to drug resistance and treatment failure.

Notification of occupational diseases by general practitioners in the Western Cape

BACKGROUND

Notification of occupational diseases to the Department of Labour (and in limited situations to other agencies) is an important aspect of surveillance and planning for interventions as well as compensation. A survey of general practitioners (GPs) was conducted to assess their knowledge and practice with regard to reporting of occupational diseases.

DESIGN

Descriptive telephonic survey.

SETTING

Independent general practices in the Western Cape.

PARTICIPANTS

One hundred and forty GPs were randomly selected from a provincial sampling frame of 1,000 GPs.

MAIN OUTCOME MEASURES

Knowledge of notification procedures for occupational diseases, and problems encountered with the reporting system.

RESULTS

Of a total of 109 GPs interviewed, 75% had diagnosed more than one case of occupational disease in the last 6 months. Twenty-four per cent of the total (95% confidence interval (CI) 16-32%) indicated that they were aware of the notification requirements, and 5% (95% CI 0.8-9%) knew the appropriate legislation. Only one GP notified the appropriate authority once the diagnosis was made. Factors influencing their reporting practice included lack of guidelines for diagnosis of common work-related conditions, lack of information regarding referral channels, problems with communicating with the patient and employer, and poor knowledge of the reporting process itself. Lack of motivation as a result of poor feedback on cases reported and the labour-intensive administration required, were also cited as factors.

CONCLUSION

Although the majority of GPs diagnose occupational diseases, knowledge and practice regarding notification are poor. Recommendations to overcome obstacles to notification include a simplified, uniform notification system, adequate training and support of GPs, and timeous feedback to GPs.

Factors influencing phenytoin-induced gingival enlargement

AIM

To ascertain the prevalence and severity of phenytoin-induced gingival enlargement (PIGE) as well as the relationship between PIGE and risk factors.

METHOD

An outpatient population of patients on phenytoin treatment and attending the epilepsy clinic at Prince Mshiyeni Memorial Hospital (PMMH) in Durban, South Africa, was requested to participate. A structured questionnaire was used to collect data on patients' demographics, social habits (e.g., drinking and smoking), dental and oral hygiene practices and medication history. Gingival enlargement, dental plaque and gingival bleeding was also measured to assess gingival health. Venous blood was collected for serum folate and phenytoin serum levels measurements. A regression analyses was then undertaken to ascertain the association between PIGE and the risk factors. Factors tested for correlation were serum phenytoin and folate levels, age, bacterial plaque, gingival inflammation, toothbrushing, smoking and alcohol consumption. The association between PIGE and the risk factors was assessed either individually, i.e., as a single entity or in combination--multifactorially.

RESULTS

Of the 134 patients studied, 62% had PIGE scores > or = 1, while 8% had a PIGE score of zero. With the exception of plaque, which showed a moderate association with PIGE (r=0.4), no other factor on its own was statistically significantly related to PIGE. In the multiple linear regression analysis, factors which on their own did not have a strong influence became more important. Bacterial plaque (p=0.0001), younger age (p=0.01) and higher free serum phenytoin levels (p= 0.03), were associated with PIGE. Although known to be associated with periodontal diseases, smoking and alcohol, (p=0.03 and p=0.04 respectively), appeared to give some protection against PIGE.

CONCLUSION

Risk factors associated with PIGE may have a synergistic effect. Bacterial plaque, however, appears the most important determinant of PIGE severity. This latter finding emphasises the importance of instituting a preventive plaque-control programme, particularly in young patients on phenytoin therapy.

Safer blood--supplementation of blood products with anti-HBs

An enzyme-linked immunosorbent assay (ELISA) was developed for the detection and quantitation of antibodies (anti-HBs) to the surface antigen of the hepatitis B virus (HBsAg). The ELISA uses HBsAg as the solid phase, and, after conjugation to horseradish peroxidase, also as the conjugate. Conditions for this assay were optimized and a rapid (1.5 hours) ELISA has evolved which works very satisfactorily for the large-scale screening of donated blood. We have used this ELISA to examine donated blood in Natal and concluded that we cannot initiate a programme of anti-HBs supplementation of parenteral blood products without hyperimmunization and plasmapheresis of selected, voluntary donors.

Rapid purification of HBsAg from human plasma

A method is described for the rapid isolation of purified HBsAg from infected donor plasma. This method uses polyethylene glycol precipitation and a single isopycnic ultracentrifugation step in which the gradient is formed in situ. It works equally well using a small swingout rotor or a zonal rotor.

Mouse monoclonal anti-HBs and its use in the screening of donated blood by Elisa

A method is described for the production of mouse monoclonal antibodies to HBsAg. 4 clones produced antibodies directed at the a and one at the d determinant of HBsAg. These antibodies were conjugated to horse radish peroxidase and used in an Elisa for the detection of HBsAg in donated blood. Antibody C10 produced conjugate which rendered the Elisa as sensitive as a commercially obtainable immunoradiometric assay with which it was compared. Conditions for this assay were optimised and it may be used as a rapid (1 h) test for detecting HBsAg-positive blood. It is practicable to read this Elisa by eye instead of photometrically and it can be thus used under field conditions or in emergencies.

ELISA solid phase: partial denaturation of coating antibody yields a more efficient solid phase

We have examined conditions which will improve the solid phase in ELISAs for HBsAg and ferritin in human serum. Sheep and rabbit antibodies were used. It was found that pre-exposure of antibody to low pH, 3 M urea and temperatures as high as 82 degrees C will enhance ELISA colour in these assays. Further experiments indicate that these conditions perturb the structure of the antibody molecules and results in the exposure of new hydrophobic regions. It is speculated that these more hydrophobic molecules can bind to regions on the plastic surface normally not coated by non-perturbed molecules.