Too tired to think: Relationship between post-COVID-19 fatigue and cognition in a veteran sample

COVID-19 survivors often endorse persistent physical and neuropsychiatric problems following disease recovery, a phenomenon described as "long COVID." Research exploring long-COVID continues to evolve in large-scale studies but remains limited among smaller populations (e.g., veterans). We explored the relationship between persistent post-COVID-19 fatigue and cognition among a sample of 246 veterans who voluntarily enrolled in a COVID-19 Convalescence Programme and completed a mental health evaluation of post-illness mood (depression, anxiety, PTSD), cognition (subjective complaints, Modified Telephone Interview for Cognitive Status [TICS-M] performance), fatigue, pain, and sleep. In concert with our hypotheses, subjective cognitive complaints are not significantly correlated with TICS-M performance, but rather are strongly correlated with long-COVID fatigue. Although cognitive changes are common post-COVID complaints, these are likely better predicted by other factors, (e.g., fatigue, mood, pain, and sleep disruption). Furthermore, comorbid mood, sleep, and pain complaints appeared to mediate the relationship between subjective cognitive complaints and fatigue. Limitations to this study included use of retrospective chart review data, limited access to pre-disease data for comparison, and lack of healthy controls. Clinicians should consider the impact of modifiable conditions associated with cognitive and functional decline, as these conditions may be targets for interdisciplinary treatment in a long-COVID veteran population.

Immune resilience despite inflammatory stress promotes longevity and favorable health outcomes including resistance to infection

Some people remain healthier throughout life than others but the underlying reasons are poorly understood. Here we hypothesize this advantage is attributable in part to optimal immune resilience (IR), defined as the capacity to preserve and/or rapidly restore immune functions that promote disease resistance (immunocompetence) and control inflammation in infectious diseases as well as other causes of inflammatory stress. We gauge IR levels with two distinct peripheral blood metrics that quantify the balance between (i) CD8+ and CD4+ T-cell levels and (ii) gene expression signatures tracking longevity-associated immunocompetence and mortality-associated inflammation. Profiles of IR metrics in ~48,500 individuals collectively indicate that some persons resist degradation of IR both during aging and when challenged with varied inflammatory stressors. With this resistance, preservation of optimal IR tracked (i) a lower risk of HIV acquisition, AIDS development, symptomatic influenza infection, and recurrent skin cancer; (ii) survival during COVID-19 and sepsis; and (iii) longevity. IR degradation is potentially reversible by decreasing inflammatory stress. Overall, we show that optimal IR is a trait observed across the age spectrum, more common in females, and aligned with a specific immunocompetence-inflammation balance linked to favorable immunity-dependent health outcomes. IR metrics and mechanisms have utility both as biomarkers for measuring immune health and for improving health outcomes.

Improving adherence to and effectiveness of a vancomycin continuous infusion protocol, a pilot quality improvement project

Introduction

Vancomycin treats serious Gram-positive infections such as methicillin-resistant Staphylococcus aureus. In St George’s University Hospital’s (SGH) intensive care unit (ICU) settings, vancomycin is administered by continuous infusion. Steady-state serum concentrations are measured daily with a 20-25 mg/L target. Non-therapeutic concentrations are associated with adverse drug reactions/prolonged length of stay.1 A SGH service-evaluation conducted across all three ICUs, revealed variable adherence to/effectiveness of its vancomycin prescribing/administration/monitoring protocol.2 Consequently, multifaceted interventions were devised using the Institute-for-Healthcare-Improvement’s model Plan-Do-Study-Act (PDSA) cycles and piloted on General ICU (GICU).

Aim

(1) To improve adherence to/effectiveness of the vancomycin protocol. (2) To ascertain administration accuracy of paper-fluid-balance-charts compared to the electronic-prescribing-and-medicines-administration (ePMA) system to assist with identifying per protocol treated patients.

Methods

PDSA Cycle-1 was conducted over a 9-month period (09/2021-05/2021) in which a mix of system/person-focused interventions were implemented. Protocol dosing2 was revised, introducing a >90kg patient 2g loading dose, renal-function category revision and increased maintenance dose for creatinine clearance (CLCR) >90ml/min. Protocol accessibility was increased via integration into an ePMA prescribing interface, plus CliniBee/Microguide apps. Educational slides on relevant protocol aspects were incorporated into medical/nursing induction training. Data relating to vancomycin prescribing/administration/monitoring for all non-renal replacement patients was extracted retrospectively from the ePMA system between 09/2021-05/2022. This data was compared to baseline GICU data (07/2020-07/2021).2 The project and associated interventions were approved by Trust Clinical Governance and Audit Teams. Data was collected by pharmacists directly involved in patient’s care and stored/analysed on the Trust’s secure server in line with Data Protection Act principles. Due to local generalisability, ethics approval wasn’t required.

Results

Compared to baseline, the proportion of patients receiving per protocol prescribing/administration of loading/maintenance doses with daily monitoring, nearly doubled (39% (7/18) to 68% (15/22)). 48-hour vancomycin serum concentrations in all patients increased therapeutically by 21% (3/9 to 7/13). In per protocol treated patients, concentrations increased 15% (2/7 to 4/9) therapeutically, decreased 21% (3/7 to 2/9) supra-therapeutically and increased 4% (2/7 to 3/9) sub-therapeutically. Supra-therapeutic concentrations were associated with CLCR<50ml/min. Sub-therapeutic concentrations were associated with CLCR>90ml/min and obesity. Compared to the ePMA system, there was 36% (8/22) less paper-fluid-balance-charts recording both loading/maintenance doses. Maintenance dose administration times in 9% (2/22) of cases differed by >60 minutes.

Discussion/Conclusion

Staff-turnover periods were associated with decreased protocol compliance. Observations suggest further education is required around prescribing/administration of standardised infusion bags for maintenance dosing. Pharmacist integration into daily Microbiology ward rounds may increase protocol compliance. Higher 20mg/kg loading doses for obese patients and maintenance dose revision should be considered to reduce non-therapeutic concentrations.3 Limitations include heterogenous/small sample sizes due to data paucity and vancomycin requirement. This can be addressed by involving all ICU’s in PDSA Cycle-2. Due to disparities, both the ePMA system and paper-fluid-balance-charts should be used to identify protocol adherence. Utilisation of digital-infusion-pump data to quantify administration accuracy may offer a promising solution. Piloted multifaceted interventions were successful at improving adherence to/effectiveness of the vancomycin protocol. Findings have informed further interventions and data capture methods for PDSA Cycle-2 implementation across all ICUs.

References

1. Perin N, Roger C, Marin G, Molinari N, Evrard A, Lavigne J et al. Vancomycin Serum Concentration after 48 h of Administration: A 3-Years Survey in an Intensive Care Unit. Antibiotics. 2020;9(11):793. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7698174/

2. Oakley R, Bakrania P, Yau T, Standing J, Lonsdale D. P37 Variable adherence to and effectiveness of a vancomycin continuous infusion protocol within ICUs at a London tertiary-care hospital: a single-centre retrospective service evaluation. JAC-Antimicrobial Resistance. 2022;4(Supplement_1). Available from: https://academic.oup.com/jacamr/issue/4/Supplement_1

3. Rybak M, Le J, Lodise T, Levine D, Bradley J, Liu C et al. Therapeutic monitoring of vancomycin for serious methicillin-resistant Staphylococcus aureus infections: A revised consensus guideline and review by the American Society of Health-System Pharmacists, the Infectious Diseases Society of America, the Pediatric Infectious Diseases Society, and the Society of Infectious Diseases Pharmacists. American Journal of Health-System Pharmacy. 2020;77(11):835-864. Available from: https://academic.oup.com/ajhp/article/77/11/835/5810200?login=false

A Learning Health System Approach to Long COVID Care

BACKGROUND

Global initiatives to mitigate COVID-19 transmission have shifted health system priorities to management of patients with prolonged long COVID symptoms. To better meet the needs of patients, clinicians, and systems, a learning health system approach can use rapid-cycle methods to integrate data and real-world experience to iteratively evaluate and adapt models of long COVID care.

OBSERVATIONS

Employees in the Veterans Health Administration formed a multidisciplinary workgroup. We sought to develop processes to learn more about this novel long COVID syndrome and innovative long COVID care models that can be applied within and outside of our health care system. We describe our workgroup processes and goals to create a mechanism for cross-facility communication, identify gaps in care and research, and cocreate knowledge on best practices for long COVID care delivery.

CONCLUSIONS

The learning health system approach will be critical in reimagining health care service delivery after the COVID-19 pandemic.

Immunologic resilience and COVID-19 survival advantage

BACKGROUND

The risk of severe coronavirus disease 2019 (COVID-19) varies significantly among persons of similar age and is higher in males. Age-independent, sex-biased differences in susceptibility to severe COVID-19 may be ascribable to deficits in a sexually dimorphic protective attribute that we termed immunologic resilience (IR).

OBJECTIVE

We sought to examine whether deficits in IR that antedate or are induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection independently predict COVID-19 mortality.

METHODS

IR levels were quantified with 2 novel metrics: immune health grades (IHG-I [best] to IHG-IV) to gauge CD8⁺ and CD4⁺ T-cell count equilibrium, and blood gene expression signatures. IR metrics were examined in a prospective COVID-19 cohort (n = 522); primary outcome was 30-day mortality. Associations of IR metrics with outcomes in non-COVID-19 cohorts (n = 13,461) provided the framework for linking pre-COVID-19 IR status to IR during COVID-19, as well as to COVID-19 outcomes.

RESULTS

IHG-I, tracking high-grade equilibrium between CD8⁺ and CD4⁺ T-cell counts, was the most common grade (73%) among healthy adults, particularly in females. SARS-CoV-2 infection was associated with underrepresentation of IHG-I (21%) versus overrepresentation (77%) of IHG-II or IHG-IV, especially in males versus females (P < .01). Presentation with IHG-I was associated with 88% lower mortality, after controlling for age and sex; reduced risk of hospitalization and respiratory failure; lower plasma IL-6 levels; rapid clearance of nasopharyngeal SARS-CoV-2 burden; and gene expression signatures correlating with survival that signify immunocompetence and controlled inflammation. In non-COVID-19 cohorts, IR-preserving metrics were associated with resistance to progressive influenza or HIV infection, as well as lower 9-year mortality in the Framingham Heart Study, especially in females.

CONCLUSIONS

Preservation of immunocompetence with controlled inflammation during antigenic challenges is a hallmark of IR and associates with longevity and AIDS resistance. Independent of age, a male-biased proclivity to degrade IR before and/or during SARS-CoV-2 infection predisposes to severe COVID-19.

Socioeconomic Factors Associated with the Receipt of Contralateral Prophylactic Mastectomy in Women with Breast Cancer

Background: Contralateral prophylactic mastectomy (CPM) treatments have been on the rise among white women with early stage unilateral breast cancer who have a higher socioeconomic status (SES) and private insurance. Low income and uninsured women are not choosing CPM at the same rate. The purpose of this study was to evaluate the socioeconomic factors related to the choice of surgical treatment in women diagnosed with unilateral breast cancer in the state of New Jersey. Materials and Methods: This retrospective study of 10 years of breast cancer data abstracted from the New Jersey State Cancer Registry utilized bivariate analyses and two multivariate logistic regression models to analyze the effect of socioeconomics on choice of surgical treatment. Results: In New Jersey, 52,529 women were treated for breast cancer from 2004 to 2014. CPM rates increased gradually over time from 3.72% in 2004 to 10.82% in 2014 with women more likely to choose CPM if they were younger, white, and had private insurance (p < 0.001). The single factor that was most predictive of choosing CPM was access to immediate reconstruction (odds ratio 2.36, confidence interval 2.160-2.551). Women with low SES were much less likely to choose CPM. Conclusions: Results of this study may provide incentive for researchers to assess the impact of culture, race/ethnicity, and socioeconomics on a woman's interactions with health care providers so as to allow all women regardless of SES to express their needs, concerns, and wishes when confronted with a breast cancer diagnosis.

Reduction of chronic hepatitis B-related hepatocellular carcinoma with anti-viral therapy, including low risk patients

BACKGROUND

Anti-viral therapy in chronic hepatitis B (CHB) is associated with a reduced risk of hepatocellular carcinoma (HCC) primary described in patients with cirrhosis.

AIM

To examine the effects of treatment on HCC incidence in CHB with and without cirrhosis, after adjustment for background risks.

METHODS

A total of 2255 CHB patients from a US cohort (973 received anti-viral therapy) and 3653 patients from the community-based Taiwanese REVEAL-HBV study, none of whom received treatment. We used Cox proportional hazard models to calculate the risk of developing HCC after adjustment with the previously validated REACH-B risk score.

RESULTS

We found 273 incident cases of HCC. After adjustment, therapy lowered the risk of HCC development in the US treated cohort when compared to the US untreated cohort (HR 0.31; 95% CI: 0.15-0.66; P = 0.002). HCC risk reduction was also confirmed when compared to the REVEAL cohort (HR 0.22; 95% CI: 0.12-0.40; P < 0.001). Each REACH-B point was associated with a 53% increased risk of HCC (HR 1.53; 95% CI 1.46-1.59; P < 0.001). We found a significant statistical reduction in HCC incidence with therapy regardless of gender, age, cirrhosis status, HBeAg serology, alanine aminotransferase level, REACH-B score or treatment medication. Therapy was beneficial to those with mildly- to moderately elevated HBV DNA levels (>2000 IU/mL) and of even greater benefit to those with levels >200 000 IU/mL.

CONCLUSION

After adjustment for background risk, anti-viral therapy was associated with a significant reduction in HCC incidence in both community and real-life clinical cohorts, including in those patients previously thought to be at low risk.

Partial state estimation for linear systems with output and input time delays

This paper deals with the problem of partial state observer design for linear systems that are subject to time delays in the measured output as well as the control input. By choosing a set of appropriate augmented Lyapunov-Krasovskii functionals with a triple-integral term and using the information of both the delayed output and input, a novel approach to design a minimal-order observer is proposed to guarantee that the observer error is ε-convergent with an exponential rate. Existence conditions of such an observer are derived in terms of matrix inequalities for the cases with time delays in both the output and input and with output delay only. Constructive design algorithms are introduced. Numerical examples are provided to illustrate the design procedure, practicality and effectiveness of the proposed observer.

Response to pegylated interferon and ribavirin in Asian American patients with chronic hepatitis C genotypes 1 vs 2/3 vs 6

Chronic hepatitis C is generally underappreciated in Asian Americans, and most pivotal studies were conducted in western countries and only included a small numbers of Asian patients. Our goal was to examine and compare treatment outcomes in these patients with genotypes 1 vs 2/3 vs 6. We performed a retrospective cohort study of 167 consecutive treatment-naïve Asian American patients treated with pegylated interferon (PEG IFN) plus ribavirin (RBV) at two community clinics in Northern California from 12/00 to 1/08. Primary outcome was sustained virological response rate by intention-to-treat analysis. The overall completion rate was 76%, and treatment adherence (completion of ≥ 75-80% PEG IFN + RBV dose for ≥ 75-80% of intended duration) was 74%. Significant depression was noted in only 4% of patients. Sustained virologic response in patients with genotype 6 treated for 48 weeks was similar to that seen in those with genotype 2/3 (74%vs 75%, P = 0.89) and significantly higher than those with genotype 1 (74%vs 49%, P = 0.016). On multivariate analysis inclusive of sex, age, body mass index (≤ 25 vs > 25) and viral load, only treatment adherence and genotype (2/3 and 6 treated for 48 weeks) were found to be significant predictors of sustained virologic response. We conclude that significant depression is rare in Asian American patients (4%). Patients with genotype 6 treated for 48 weeks appear to have a similar treatment response rate as patients with genotype 2/3 and a significantly higher response rate than those with genotype 1.

Clinical course of hepatitis B virus infection during pregnancy

BACKGROUND

For women with hepatitis B virus (HBV) infection, little is known about the natural progression of the disease during pregnancy or its impact on pregnancy outcomes.

OBJECTIVES

To investigate the natural progression of HBV infection during pregnancy or its impact on pregnancy outcomes.

METHODS

In this retrospective cohort study, we reviewed medical records of all patients who were pregnant and presented with HBsAg-positivity between 2000 and 2008 at a community gastroenterology practice and a university hepatology clinic. Maternal characteristics were analysed according to maternal and perinatal outcomes.

RESULTS

A total of 29 cases with at least 2 measurements of either HBV DNA or alanine aminotransferase (ALT) levels were included. Older age was the only predictor of a trend towards higher risk of an adverse clinical outcome [OR = 1.21 (0.97-1.51), P = 0.089], defined as either a negative foetal outcome (premature delivery, spontaneous abortion), or a negative maternal outcomes (gestational diabetes mellitus, pre-eclampsia, hepatic flare, liver failure). This trend for age remained even after adjusting for baseline ALT. Baseline serum HBV DNA, ALT, hepatitis B e antigen status, gravida and parity were not significant predictors for adverse clinical outcomes. Four patients developed liver failure.

CONCLUSIONS

Maternal and neonatal outcomes are highly variable in this clinic-based patient cohort. Severe complications due to HBV infection can occur during pregnancy in previously asymptomatic patients. It is unclear how generalizable the results observed in this cohort would be to the general population; therefore, further studies are needed to identify reliable predictors for significant adverse outcomes and until more data are available, pregnant patients with HBV infection should be monitored with periodic serum HBV DNA and ALT levels.

Rapid inactivation of the maize transposable element En/Spm in Medicago truncatula

Transposable elements have been widely used as mutagens in many organisms. Among them, the maize transposable element En/Spm has been shown to transpose efficiently in several plant species including the model plant Arabidopsis, where it has been used for large-scale mutagenesis. To determine whether we could use this transposon as a mutagen in the model legume plant Medicago truncatula, we tested the activity of the autonomous element, as well as two defective elements, in this plant, and in Arabidopsis as a positive control. In agreement with previous reports, we observed efficient excision of the autonomous En/Spm element in A. thaliana. This element was also active in M. truncatula, but the transposition activity was low and was apparently restricted to the tissue culture step necessary for the production of transgenic plants. The activity of one of the defective transposable elements, dSpm, was very low in A. thaliana and even lower in M. truncatula. The use of different sources of transposases suggested that this defect in transposition was associated with the dSpm element itself. Transposition of the other defective element, I6078, was also detected in M. truncatula, but, as observed with the autonomous element, transposition events were very rare and occurred during tissue culture. These results suggest that the En/Spm element is rapidly inactivated in the regenerated plants and their progeny, and therefore is not suitable for routine insertion mutagenesis in M. truncatula.

Dexamethasone increases the expression of membrane macrophage colony stimulating factor from retrovirally transduced tumor cells expressing macrophage colony stimulating factor

Many different tumor cell types (breast, ovarian, glioma, liver and colon) were retrovirally transduced with the human macrophage colony stimulating factor (M-CSF) gene (either the membrane associated form [mM-CSF] or the secreted form [sM-CSF]). These cells were tested for their ability to display increased amounts of mM-CSF in response to dexamethasone. M-CSF-transfected tumor cells expressed additional mM-CSF in response to 18-72 h incubations with 3-15 microg/ml dexamethasone, while non-transfected parental cells were unaffected by this treatment. Increased mM-CSF protein expression on the M-CSF transduced cells was observed by flow cytometry and Western blotting using M-CSF specific antibodies. Northern blot analysis revealed an increase in the mM-CSF specific transcripts within the dexamethasone-treated mM-CSF transduced cells, but this was not seen within the non-transfected tumor cells that were treated with dexamethasone. ICAM-1 expression was unaffected by dexamethasone treatment, indicating that this response is mM-CSF specific. All trans-retinal and 1,25-dihydroxy vitamin D3 compounds that have been reported to induce M-CSF expression failed to increase mM-CSF. When dexamethasone-treated mM-CSF transfected clones were used as target cells for macrophage-mediated cytotoxicity assays, an increased killing with the dexamethasone-treated cells was seen. The macrophage-mediated cytotoxicity of these mM-CSF expressing tumor cells was blocked with excess recombinant M-CSF by saturating M-CSF receptors on the macrophage that is required for this form of tumor cell killing. This work suggests the possibility that dexamethasone may prove useful for vaccination purposes using mM-CSF retrovirally transfected tumor cells.

Membrane macrophage colony-stimulating factor on MADB106 breast cancer cells does not activate cytotoxic macrophages but immunizes rats against breast cancer

Weakly immunogenic, but highly malignant, rat MADB106 breast cancer cells were retrovirally transduced with the membrane form of macrophage colony-stimulating factor (mM-CSF). The cloned mM-CSF-transfected MADB106 cells physically conjugated with macrophages, but were not killed by the macrophages in 48-h cytotoxicity assays. Macrophages killed the mM-CSF-expressing tumors in the presence of noncytotoxic doses of either taxol or taxol plus cisplatin. This indicated that macrophages bind to the mM-CSF expressed on the tumor cells, but for successful macrophage cytotoxicity to occur against mM-CSF-transduced tumor cells other factors must be present. The mM-CSF-transfected tumor cells were rejected when inoculated subcutaneously into normal rats. Cloned MADB106 tumor cells which expressed high amount of mM-CSF were rejected, while tumor cells that displayed lower levels of mM-CSF grew in 60% of the inoculated rats. The mM-CSF-transfected tumors that grew were smaller and had a greater amount of necrosis, compared to the viral vector tumors. Rats that spontaneously rejected the mM-CSF-transfected MADB106 cells showed rechallenge resistance to unmodified parental MADB106 and R3230Ac breast cancers, but not to the F98 glioma. These observations suggest that breast cancer-specific immunity was induced by the inoculation of mM-CSF-expressing MADB106 tumor cells.

Minimal tumor necrosis factor receptor binding protein: optimum biological activity of a truncated p55 soluble tumor necrosis factor receptor-IgG fusion protein

We have previously demonstrated, using expressed deletion constructs, that the fourth membrane proximal cysteine-rich repeat of the p55 TNF receptor (TNF-R) is not required for binding of tumour necrosis factor-alpha (TNF) or lymphotoxin-alpha (LT; tumour necrosis factor-beta). We and others have also shown that the soluble p55 TNF-R, rendered dimeric by fusion to an IgG backbone is extremely effective at neutralizing the harmful effects of TNF overproduction, such as in toxic shock. Here we address the question of how the TNF binding properties of the truncated TNF-R comprising the three distal cysteine-rich repeats (delta4 TNF-R), when fused with an IgG backbone, compare with those of the full length soluble receptor. We constructed several versions of the soluble delta4 TNF-R, on a complete IgG heavy chain backbone and on an IgG lacking the CH1 (first constant region) domain. The constructs were expressed with an Ig or native TNF receptor leader sequence and altered or native N terminal sequence, to compare efficiency of expression. When compared with a full length, soluble receptor Ig fusion protein, the affinity of all for TNF was identical, as were their activities in in vitro binding and cytotoxicity assays. In vivo studies showed that the delta4 and wild type fusion proteins afforded equivalent protection against LPS-induced lethality. However, the delta4 proteins exhibited a significantly lower affinity for LT, and reduced activity in LT binding and cytotoxicity assays. We conclude that the truncated TNF receptor IgG fusion protein is as effective at neutralizing TNF activity as the full length soluble receptor fusion protein. Its lower affinity for LT may make it a more selective agent in blocking the action of TNF, while causing less interference with the action of LT. Also its smaller size may make it a more useful therapeutic agent as it may be less immunogenic than the full length receptor.

Functional comparisons of different tumour necrosis factor receptor/IgG fusion proteins

Nine different IgG fusion proteins and one non-fusion protein, all containing sequences from the extracellular domain of either of two human TNF receptors, were compared for their ability to bind and inhibit human TNF-alpha or TNF-beta. The fusion proteins differed with respect to TNF receptor type (p55 or p75 TNF receptor), receptor valency (one, two or four receptor domains per molecule), the presence or absence of a CH1 domain in the IgG constant region, and the proportion of the extracellular domain included in the construct. In vitro TNF binding assays and cytotoxicity assays indicated that, of the constructs that bound TNF, the greatest difference in affinity and neutralizing capability was between monovalent and bivalent receptor constructs. Differences were also noted between tetravalent and bivalent versions of p55 fusion proteins, as well as between a p75 fusion protein comprising the complete extracellular domain and one lacking the C-terminal 53 amino acids of the extracellular domain. p55 constructs that included only the second cysteine-rich domain (CRD) or only the second and third CRDs showed no TNF binding activity. The presence or absence of an IgG CH1 domain made no difference in the ability of fusion proteins to neutralize TNF-alpha or TNF-beta. Animal experiments comparing the tetravalent and bivalent p55 fusions and the effects of the CH1 domain did not show significant differences in their ability to protect mice from endotoxin-induced lethality, although the p55 fusion proteins appeared to be more protective than the p75 fusion proteins. Thus, this study has identified structural modifications to TNF receptor/IgG fusion proteins which have differing effects on their neutralizing ability towards TNF-alpha or TNF-beta.

Chimeric anti-TNF-alpha monoclonal antibody cA2 binds recombinant transmembrane TNF-alpha and activates immune effector functions

Results of clinical trials have indicated that cA2, a neutralizing mouse/human IgG1 chimeric anti-human TNF-alpha monoclonal antibody, may have therapeutic benefit for rheumatoid arthritis patients. Arthritic joints contain, in addition to elevated levels of soluble TNF-alpha, high numbers of CD4+ T cells and macrophages, cells known to express transmembrane TNF-alpha upon activation. For that reason, we sought to determine if cA2 binds to transmembrane TNF-alpha and what effects such binding may have on TNF-alpha-expressing cells. A cell line expressing a cell-surface, mutant form of transmembrane TNF-alpha was prepared for these studies. Analysis of these TNF+ cells by flow cytometry, direct binding, and competitive binding assays showed that cA2 binds to the transmembrane form of TNF-alpha with high avidity. Binding of the IgG1 isotype of cA2, but not an IgG4 version of cA2, resulted in efficient killing of the TNF+ cells by both antibody-dependent cellular toxicity and complement-dependent cytotoxicity effector mechanisms. These findings indicate that, in addition to blocking soluble TNF-alpha activity, cA2 can bind to transmembrane TNF-alpha in vitro and suggest that cA2 binding may lead to lysis of TNF-alpha-expressing cells in vivo.

Construction and initial characterization of a mouse-human chimeric anti-TNF antibody

Tumor necrosis factor-alpha (TNF) has been implicated in the pathogenesis of a variety of human diseases including septic shock, cachexia, graft-versus-host disease and several autoimmune diseases. Monoclonal antibodies directed against TNF provide an attractive mode of therapeutic intervention in these diseases. We have generated a murine monoclonal antibody (A2) with high affinity and specificity for recombinant and natural human TNF. To increase its therapeutic usefulness, we used genetic engineering techniques to replace the murine constant regions with human counterparts while retaining the murine antigen binding regions. The resulting mouse-human chimeric antibody should have reduced immunogenicity and improved pharmacokinetics in humans. Molecular analysis of light chain genomic clones derived from the murine hybridoma suggests that two different alleles of the same variable region gene have rearranged independently and coexist in the same hybridoma cell. The chimeric A2 antibody (cA2) exhibits better binding and neutralizing characteristics than the murine A2 which was shown to contain a mixture of two kappa light chains. The properties of cA2 suggest that it will have advantages over existing murine anti-TNF antibodies for clinical use.

High-level expression and characterization of a mouse-human chimeric CD4 antibody with therapeutic potential

The use of murine anti-CD4 monoclonal antibodies (MAbs) has shown considerable promise for the treatment of allograft rejection and rheumatoid arthritis. We have constructed mouse-human anti-CD4 antibodies with the goal of increasing their clinical potential by decreasing immunogenicity and improving effector functions. The chimeric antibodies were constructed by cloning the heavy and light chain variable regions of M-T412, a murine antibody raised against the human CD4 antigen, and joining them to the human G1, G4, or kappa constant regions in mammalian expression vectors. After transfection into mouse myeloma cells, stable cell lines were isolated that secrete up to 140 micrograms/ml chimeric antibody in static culture. The chimeric antibodies were equivalent to the murine antibody in their binding characteristics and relative affinities. However, the chimeric M-T412 MAbs have enhanced activity when compared to the murine G2a MAb in mediating antibody-dependent cell-mediated cytotoxicity using human CD4+ target and effector cells.

Evidence for carrier-mediated transport of glutathione across the blood-brain barrier in the rat

Information on the origin of brain glutathione and the possibility of its transport from blood to brain is limited. We found a substantial uptake of 35S-labeled glutathione by the rat brain using the carotid artery injection technique. The brain uptake index of glutathione with and without an irreversible gamma-glutamyl transpeptidase inhibitor, acivicin, was similar. No significant differences in the regional uptake of labeled glutathione were found in rats pretreated with acivicin. The brain uptake index of tracer glutathione was similar to that of cysteine tracer and was lower than that of phenylalanine. The transport of oxidized glutathione (glutathione disfulfide) across the blood-brain barrier was not significantly different from that of sucrose, an impermeable marker. Brain radioactivity 15 s after carotid artery injection of labeled glutathione to rats pretreated with acivicin was predominantly in the form of glutathione. The in vivo glutathione uptake was saturable with an apparent Km of 5.84 mM. Amino acids, amino acid analogues, and other compounds [cysteine, phenylalanine, glutathione disulfide, gamma-glutamylglutamate, gamma-glutamyl p-nitroanilide, 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid (BCH)] did not affect glutathione transport. Our data suggest that glutathione is transported across the blood-brain barrier by a saturable and specific mechanism.