Treatment-resistant depression: definition,prevalence, detection,management, and investigational interventions

Treatment-resistant depression (TRD) is common and associated with multiple serious public health implications. A consensus definition of TRD with demonstrated predictive utility in terms of clinical decision-making and health outcomes does not currently exist. Instead, a plethora of definitions have been proposed, which vary significantly in their conceptual framework. The absence of a consensus definition hampers precise estimates of the prevalence of TRD, and also belies efforts to identify risk factors, prevention opportunities, and effective interventions. In addition, it results in heterogeneity in clinical practice decision-making, adversely affecting quality of care. The US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) have adopted the most used definition of TRD (i.e., inadequate response to a minimum of two antidepressants despite adequacy of the treatment trial and adherence to treatment). It is currently estimated that at least 30% of persons with depression meet this definition. A significant percentage of persons with TRD are actually pseudo-resistant (e.g., due to inadequacy of treatment trials or non-adherence to treatment). Although multiple sociodemographic, clinical, treatment and contextual factors are known to negatively moderate response in persons with depression, very few factors are regarded as predictive of non-response across multiple modalities of treatment. Intravenous ketamine and intranasal esketamine (co-administered with an antidepressant) are established as efficacious in the management of TRD. Some second-generation antipsychotics (e.g., aripiprazole, brexpiprazole, cariprazine, quetiapine XR) are proven effective as adjunctive treatments to antidepressants in partial responders, but only the olanzapine-fluoxetine combination has been studied in FDA-defined TRD. Repetitive transcranial magnetic stimulation (TMS) is established as effective and FDA-approved for individuals with TRD, with accelerated theta-burst TMS also recently showing efficacy. Electroconvulsive therapy is regarded as an effective acute and maintenance intervention in TRD, with preliminary evidence suggesting non-inferiority to acute intravenous ketamine. Evidence for extending antidepressant trial, medication switching and combining antidepressants is mixed. Manual-based psychotherapies are not established as efficacious on their own in TRD, but offer significant symptomatic relief when added to conventional antidepressants. Digital therapeutics are under study and represent a potential future clinical vista in this population.     

Heat shock in mechanically wounded carrot root disks causes destabilization of stable secretory protein mRNA and dissociation of endoplasmic reticulum lamellae

In many organisms, the synthesis of heat shock proteins during heat shock is concomitant with the cessation of at least a portion of normal cellular protein synthesis. Heat shocked barley aleurone layers selectively stop the synthesis and secretion of secretory proteins. Exposure to 40°C causes a disruption of endoplasmic reticulum (ER) lamellae, which we have hypothesized leads to the destabilization of otherwise stable mRNA previously associated with ER‐bound polyribosomes. We report here that this was also observed in wounded carrot ( Daucus carota L.) root parenchyma tissue which synthesizes and secretes cell wall proteins when mechanically wounded. Nondenaturing cationic polyacrylamide gel electrophoresis of radiolabeled proteins indicated that heat shock caused the cessation of the synthesis and secretion of extensin, a hydroxyproline‐rich cell wall glycoprotein. Northern blot analyses indicated that the mRNA levels for both extensin and another cell wall protein (p33) were rapidly diminished during heat shock. Under nonheat shock conditions extensin mRNA had a half‐life of greater than 4 h, but this appeared to be reduced to less than 30 min during heat shock. There was also a concomitant dissociation of ER lamellae in wounded, heat shocked carrot root tissue, as observed by transmission electron microscopy. These observations indicate that this response may be universal among plant secretory tissues.     

Internal pH crisis, lysine decarboxylase and the acid tolerance response of Salmonella typhimurium

Salmonella typhimurium possesses an adaptive response to acid that increases survival during exposure to extremely low pH values. The acid tolerance response (ATR) includes both log-phase and stationary-phase systems. The log-phase ATR appears to require two components for maximum acid tolerance, namely an inducible pH homeostasis system, and a series of acid-shock proteins. We have discovered one of what appears to be a series of inducible exigency pH homeostasis systems that contribute to acid tolerance in extreme acid environments. The low pH-inducible lysine decarboxylase was shown to contribute significantly to pH homeostasis in environments as low as pH 3.0. Under the conditions tested, both lysine decarboxylase and σ^s-dependent acid-shock proteins were required for acid tolerance but only lysine decarboxylase contributed to pH homeostasis. The cadBA operon encoding lysine decarboxylase and a lysine/cadaverine antiporter were cloned from S. typhimurium and were found to be 79% homologous to the cadBA operon from Escherichia coli . The results suggest that S. typhimurium has a variety of means of fulfilling the pH homeostasis requirement of the ATR in the form of inducible amino acid decarboxylases.     

Cell separation from high cell density broths of Alcaligenes eutrophus by using a coagulant

Summary Alcaligenes eutrophus was successfully recovered from high cell density broths by pre-treatment with polyaluminium hydroxide chloride silicate as a coagulant at 36–90 mg Al/l. The optimum pH range for cell coagulation was 10–12. Subsequent centrifugation (45×g) and filtration (pore size 0.5 mm) gave a cell recovery of higher than 90%. The energy demand for cell recovery with the coagulant was only 3–11% of that without it.     

Monoclonal antibody refolding and assembly: Protein disulfide isomerase reaction kinetics

The protein disulfide isomerase (PDI) reaction kinetics has been studied to evaluate its effect on the monoclonal antibody (MAb) refolding and assembly which accompanies disulfide bond formation. The MAbin vitro assembly experiments showed that the assembly rate of heavy and light chains can be greatly enhanced in the presence of PDI as compared to the rate of assembly obtained by the air-oxidation. The reassembly patterns of MAb intermediates were identical for both with and without PDI, suggesting that the PDI does not determine the MAb assembly pathway, but rather facilitates the rate of MAb assembly by promoting PDI catalyzed disulfide bond formation. The effect of growth rate on PDI activities for MAb production has also been examined by using continuous culture system. The specific MAb productivity of hybridoma cells decreased as the growth rate increased. However, PDI activities were nearly constant for a wide range of growth rates except very high growth rate, indicating that no direct correlation between PDI activity and specific MAb productivity exists.     

Translatable RNA Populations Associated with Maintenance of Primary Root Elongation and Inhibition of Mesocotyl Elongation by Abscisic Acid in Maize Seedlings at Low Water Potentials

Previous work indicated that accumulation of abscisic acid (ABA) acts differentially to maintain elongation of the primary root and inhibit elongation of the mesocotyl of maize (Zea mays L.) seedlings at low water potentials ([psi]w). Subsequent results indicated specific locations in the elongation zones where elongation is maintained, inhibited, or unaffected by endogenous ABA at low [psi]w. This information was utilized in this study to identify in vitro translation products of RNA associated with the maintenance or inhibition of elongation in the primary root and mesocotyl, respectively, by endogenous ABA at low [psi]w. The results distinguished products associated specifically with the elongation responses from those nonspecifically associated with ABA accumulation or low [psi]w, as well as normal cell development and maturation. In the primary root, the maintenance of elongation at low [psi]w by ABA was associated with the maintenance of expression of three products that were also expressed during elongation at high [psi]w, the expression of a novel product, and the suppression of two products. In the mesocotyl, the inhibition of elongation by ABA after transplanting to low [psi]w was associated with the induction of a novel translation product. However, the induction of this product, as well as accumulation of ABA and inhibition of elongation, occurred without a decline in tissue water content. The results demonstrate the necessity of examining the association of gene expression with elongation responses to low [psi]w with a high degree of spatial resolution.     

Effect of different donor cells on human immunodeficiency virus type 1 replication and selection in vitro.

We sought to determine the effects of different host cells on human immunodeficiency virus type 1 (HIV-1) infection in vitro. First, 17 primary viruses of various phenotypes were examined for replicative capacity in peripheral blood mononuclear cells (PBMC) from 10 healthy donors. While the range of infection was variable over a 40-fold range, it was substantially less than that previously reported (L. M. Williams and M. W. Cloyd, Virology 184:723-728, 1991). In particular, no donor cells demonstrated total resistance to HIV-1 infection. We next cocultured PBMC from an HIV-1-infected patient with stimulated PBMC from three healthy donors to determine the effect of host cells on selection for a particular HIV-1 quasispecies. By using DNA sequencing, it was found that the dominant quasispecies (AD30-15) after culture was nearly identical in the cells of different donors. Furthermore, after 6 months in vivo, the patient developed a dominant proviral population in PBMC that was most closely related to the quasispecies preferentially selected in vitro, although this quasispecies was only a minor fraction of the sequences present earlier in PBMC. In subsequent biological characterizations, it was found that AD30-15 grew much better in PBMC and macrophages than did other related quasispecies. Hence, we conclude that the primary mechanism of in vitro selection for a particular HIV-1 variant in this case is mediated by the phenotypic properties of the virus and is less dependent on host cell origin. The findings reported here have important practical implications for studies of HIV-1 replication in primary cells derived from healthy donors.     

A human monoclonal antibody to a complex epitope in the V3 region of gp120 of human immunodeficiency virus type 1 has broad reactivity within and outside clade B.

We have used virus neutralization and antibody-binding techniques to define the epitope for a human monoclonal antibody, designated 19b, within the V3 region of the gp120 surface glycoprotein of human immunodeficiency virus type 1. Unusually, the 19b epitope encompasses residues on both flanks of the V3 loop. However, 19b binding to gp120 is independent of sequences at the crown of the V3 loop, provided that they are compatible with the formation of a type II beta turn that is presumably necessary to juxtapose the antigenic residues on the V3 flanks. By comparing the V3 sequences of virus gp120s able and unable to bind 19b, we were able to define the canonical 19b epitope as -I----G--FY-T, where residues at the positions indicated by the gaps do not contribute directly to the 19b-binding site. A few conservative substitutions at the more critical residues are also compatible with 19b binding. Inspection of V3 sequences in the human immunodeficiency virus database indicated that the canonical 19b epitope is well conserved among isolates from the North American-European clade B and also among clade E isolates from Thailand and clade F isolates from Brazil. A minority of gp120s from clades A and C also possess the 19b epitope. Consistent with the theoretical predictions of its cross-clade reactivity, 19b was found to bind to gp120s from clades A, B, C, E, and F in immunoassays. However, 19b was not able to reduce the infectivity of primary viruses from clades A, E, and F that were predicted to possess the 19b epitope and only modestly reduced the infectivity of a clade C virus at low input virus concentrations. Cross-clade neutralization via V3-directed antibodies may, therefore, be difficult, even if the antibodies show broad reactivities in binding assays and the viruses theoretically possess the relevant binding site.     

Sequence diversity of V1 and V2 domains of gp120 from human immunodeficiency virus type 1: lack of correlation with viral phenotype.

We analyzed by PCR and direct sequencing 57 viral sequences from 47 individuals infected with human immunodeficiency virus type 1, focussing on the V1 and V2 regions of gp120. There was extensive length polymorphism in the V1 region, which rendered sequence alignment difficult. The V2 hypervariable locus also displayed considerable length variations, whereas flanking regions were relatively conserved. Two-thirds of the amino acid residues in these flanking regions were highly conserved (> 80%), presumably reflecting their critical contribution to V2 structure or function. We also characterized the syncytium-inducing properties of the isolates from which we derived sequence information. There was no correlation between V1 or V2 sequences and the viral phenotype, contrary to a previous report (M. Groenink, R. A. M. Fouchier, S. Broersen, C. H. Baker, M. Koot, A. B. van't Wout, H. G. Huisman, F. Miedema, M. Tersmette, and H. Schuitemaker, Science 260:1513-1516, 1993). The sequence heterogeneity described in this study provides information to suggest that it would be most difficult to exploit the V1 and V2 domains for vaccine development.