Cabotegravir for HIV Prevention in Cisgender Men and Transgender Women.

BACKGROUND: Safe and effective long-acting injectable agents for preexposure prophylaxis (PrEP) for human immunodeficiency virus (HIV) infection are needed to increase the options for preventing HIV infection. METHODS: We conducted a randomized, double-blind, double-dummy, noninferiority trial to compare long-acting injectable cabotegravir (CAB-LA, an integrase strand-transfer inhibitor [INSTI]) at a dose of 600 mg, given intramuscularly every 8 weeks, with daily oral tenofovir disoproxil fumarate-emtricitabine (TDF-FTC) for the prevention of HIV infection in at-risk cisgender men who have sex with men (MSM) and in at-risk transgender women who have sex with men. Participants were randomly assigned (1:1) to receive one of the two regimens and were followed for 153 weeks. HIV testing and safety evaluations were performed. The primary end point was incident HIV infection. RESULTS: The intention-to-treat population included 4566 participants who underwent randomization; 570 (12.5%) identified as transgender women, and the median age was 26 years (interquartile range, 22 to 32). The trial was stopped early for efficacy on review of the results of the first preplanned interim end-point analysis. Among 1698 participants from the United States, 845 (49.8%) identified as Black. Incident HIV infection occurred in 52 participants: 13 in the cabotegravir group (incidence, 0.41 per 100 person-years) and 39 in the TDF-FTC group (incidence, 1.22 per 100 person-years) (hazard ratio, 0.34; 95% confidence interval, 0.18 to 0.62). The effect was consistent across prespecified subgroups. Injection-site reactions were reported in 81.4% of the participants in the cabotegravir group and in 31.3% of those in the TDF-FTC group. In the participants in whom HIV infection was diagnosed after exposure to CAB-LA, INSTI resistance and delays in the detection of HIV infection were noted. No safety concerns were identified. CONCLUSIONS: CAB-LA was superior to daily oral TDF-FTC in preventing HIV infection among MSM and transgender women. Strategies are needed to prevent INSTI resistance in cases of CAB-LA PrEP failure. (Funded by the National Institute of Allergy and Infectious Diseases and others; HPTN 083 ClinicalTrials.gov number, NCT02720094.).

The External Morphology of Mythimna (Pseudaletia) sequax (Lepidoptera: Noctuidae).

Mythimna (Pseudaletia) sequax Franclemont, 1951 (Lepidoptera: Noctuidade) is the most important armyworm in the American tropics and subtropics. In this study, we describe the external morphology of the immatures and adults, based on larvae fed on quicuio grass (Pennisetum clandestinum Hochst. ex Chiov - Poaceae). The external morphology of the eggs, larvae, pupae, and adults is described and illustrated. Important taxonomic structures of the larvae are described, including hypopharynx, spinneret, and mandible. Adult structures that allow the differentiation of the species, such as male genitalia and scent brushes, are also described. The results are compared and discussed based on morph functionality and with publications on the congeneric species.

Improving reading comprehension: From metacognitive intervention on strategies to the intervention on working memory executive processes / Mejorando la comprensión lectora: Desde la intervención metacognitiva en estrategias a la intervención en los procesos ejecutivos de la memoria operativa

Many students may read fluently but have difficulties constructing meaning from texts. Difficulties with reading comprehension have many implications at school. In particular, problems understanding texts interfere with studying and learning from text. Reading comprehension has improved in the last 30 years focusing on intervention programs that work with strategies in which metacog-nition plays a crucial role. However, recent years have seen relevant advances in the study of the relationship between working memory (WM), particularly executive processes, and reading comprehension. In this paper, we present how the last 20 years of our research has evolved regarding metacognitive intervention from text comprehension strategies, as the main idea and summarization to the intervention on WM's executive processes during reading. Thus, our more recent empirical data has shown that text comprehension can be improved after specific training on the executive functions of working memory (e.g., focusing, switching, connecting and updating mental representations, and the inhibition of irrelevant information) in Primary school students.

Muchos estudiantes pueden leer de forma fluida pero presentan dificultades para construir significados a partir de los textos. Las dificultades de compresión lectora tienen varias implicaciones en la escuela. En particular, los problemas de comprensión de textos interfieren con el estudio y el aprendizaje desde el texto. La comprensión de lectura se ha mejorado en los últimos 30 años enfocándose en los programas de intervención que trabajan con estrategias en las cuales la metacognición juega un papel crucial. Sin embargo, en años recientes han sido relevantes los avances en el estudio de las relaciones entre la memoria de trabajo (WM), particularmente el proceso ejecutivo, y la comprensión de lectura. En este artículo presentamos la manera como se ha desarrollado nuestra investigación en los últimos 20 años, en relación con intervención metacognitiva desde las estrategias de comprensión de textos, tales como la idea principal y el resumen en la intervención sobre el proceso ejecutivo de WM durante la lectura. Así, nuestros datos empíricos recientes han mostrado que la comprensión de textos puede ser mejorada después del tratamiento específico sobre las funciones ejecutivas de memoria de trabajo (e.g., enfocándose, cambiando, conectando y actualizando las representaciones mentales y la inhibición de información irrelevante) en niños de escuela primaria.

Neurological and psychiatric tolerability of rilpivirine (TMC278) vs. efavirenz in treatment-naïve, HIV-1-infected patients at 48 weeks.

OBJECTIVES: The aim of the study was to compare the neuropsychiatric safety and tolerability of rilpivirine (TMC278) vs. efavirenz in a preplanned pooled analysis of data from the ECHO and THRIVE studies which compared the safety and efficacy of the two drugs in HIV-1 infected treatment naïve adults. METHODS: ECHO and THRIVE were randomized, double-blind, double-dummy, 96-week, international, phase 3 trials comparing the efficacy, safety and tolerability of rilpivirine 25 mg vs. efavirenz 600 mg once daily in combination with two background nucleoside/tide reverse transcriptase inhibitors. Safety and tolerability analyses were conducted when all patients had received at least 48 weeks of treatment or discontinued earlier. Differences between treatments in the incidence of neurological and psychiatric adverse events (AEs) of interest were assessed in preplanned statistical analyses using Fisher's exact test. RESULTS: At the time of the week 48 analysis, the cumulative incidences in the rilpivirine vs. efavirenz groups of any grade 2-4 treatment-related AEs and of discontinuation because of AEs were 16% vs. 31% (P<0.0001) and 3% vs. 8% (P=0.0005), respectively. The incidence of treatment-related neuropsychiatric AEs was 27% vs. 48%, respectively (P<0.0001). The incidence of treatment-related neurological AEs of interest was 17% vs. 38% (P<0.0001), and that of treatment-related psychiatric AEs of interest was 15% vs. 23% (P=0.0002). Dizziness and abnormal dreams/nightmares occurred significantly less frequently with rilpivirine vs. efavirenz (P<0.01). In both groups, patients with prior neuropsychiatric history tended to report more neuropsychiatric AEs but rates remained lower for rilpivirine than for efavirenz. CONCLUSIONS: Rilpivirine was associated with fewer neurological and psychiatric AEs of interest than efavirenz over 48 weeks in treatment-naïve, HIV-1-infected adults.

The interpretation of indicative and subjunctive concessives.

Using a priming paradigm in the context of a reading comprehension task, the possibilities that people keep in mind in order to understand indicative and subjunctive concessive sentences were examined and compared to those from factual and counterfactual 'if A, not-B' conditionals. The length of time it took people to read conjunctive descriptions (i.e., A and B, A and not-B, not-A and B, not-A and not-B) after they had been primed by the different types of linguistic form was measured. The results suggest that, whereas indicative 'even though' concessives and 'if, not' conditionals are understood by keeping in mind just a single possibility ('A and B' and 'A and not-B', respectively), the initial representations of subjunctive 'even if' concessive-conditionals and 'if, not' counterfactuals are compatible with a multiple-model representation. The implications of these results are discussed within the mental models framework.

The nuclear orphan receptor TR4 promotes proliferation of myeloid progenitor cells.

Nuclear receptors represent key regulators in cell proliferation, differentiation, and development. Here we demonstrate that the nuclear orphan receptor TR4 is highly expressed in hematopoietic cells and tissues and have analyzed the impact of TR4 in this cell compartment. We show that TR4, when ectopically expressed in bone marrow cells via retrovirus vector, promotes proliferation of myeloid progenitor cells. Cells represent promyelocytes as judged by morphological features, expression of cell surface molecules, and specific markers like Mim-1 and CAAT/enhancer binding protein beta. We also demonstrate that the growth promoting activity of TR4 is not exclusively dependent on its association with DNA, because expression of a mutated TR4 version devoid of its DNA binding domain exhibits a similar proliferative potential as wild-type TR4. In conclusion, these data position the orphan receptor TR4 as an important regulator of myeloid progenitor cell proliferation and development.

Are conjunctive inferences easier than disjunctive inferences? A comparison of rules and models.

We report four experiments investigating conjunctive inferences (from a conjunction and two conditional premises) and disjunctive inferences (from a disjunction and the same two conditionals). The mental model theory predicts that the conjunctive inferences, which require one model, should be easier than the disjunctive inferences, which require multiple models. Formal rule theories predict either the opposite result or no difference between the inferences. The experiments showed that the inferences were equally easy when the participants evaluated given conclusions, but that the conjunctive inferences were easier than the disjunctive inferences (1) when the participants drew their own conclusions, (2) when the conjunction and disjunction came last in the premises, (3) in the time the participants spent reading the premises and in responding to given conclusions, and (4) in their ratings of the difficulty of the inferences. The results support the model theory and demonstrate the importance of reasoners' inferential strategies.

Dendritic cells conditionally transformed by v-relER oncogene express lymphoid marker genes.

The initiation of primary immune responses is the key function of specialized antigen presenting cells, the dendritic cells (DC). DC of myeloid origin capture antigens in tissues, migrate to lymphoid organs and stimulate T cell responses. A subset of DC has been described which expresses lymphoid determinants and has potential regulatory functions. Conditional transformation of chicken bone marrow progenitors with v-relER, a v-rel estrogen receptor (ER) fusion gene, allows expansion of progenitors that can be induced to differentiate into DC in vitro. In this paper we describe that v-relER cells exhibit both myeloid and lymphoid surface markers, while B cell, T cell and NK (natural killer)-specific surface markers are absent. v-relER DC express, however, cytoplasmic CD3 protein and mRNA for CD8alpha and the lymphoid transcription factor GATA-3. These data suggest that v-relER DC might be related to the lymphoid subset of DC described in mammals.

Polarised expression pattern of focal contact proteins in highly motile antigen presenting dendritic cells.

Dendritic cells are professional antigen presenting cells that capture antigens and migrate to lymphoid tissues to elicit specific T cell responses. Here we used an in vitro differentiation system for generating highly motile dendritic cells from chicken bone marrow progenitors by employing the conditional v-Rel estrogen receptor (ER) fusion protein v-RelER. Molecular mechanisms of dendritic cell motility were investigated. Differentiation of v-relER progenitors into dendritic cells is associated with a reduction in cell-cell and cell-extracellular matrix interactions as cells acquire motility. We demonstrate that v-relER progenitors and dendritic cells express several adhesion receptors and components of adhesion complexes. Differentiation of v-relER cells was accompanied by downregulation of focal adhesion kinase (FAK), a key molecule of adhesion complexes, but ectopic FAK expression did not affect cell adhesion and motility. Interestingly, v-relER dendritic cells exhibit a polarised expression pattern of actin and vimentin, with actin being highly concentrated at the leading edge of the cells where lamellipodia are formed. FAK, paxillin and tyrosine phosphorylated proteins are found at both poles of the cell and colocalise with actin at the leading edge, while surface beta1 integrin is confined to the uropod at the rear. CD34(+ )stem cell-derived human dendritic cells also exhibited an elongated bipolar morphology, mode of migration and a polarised pattern of actin-vimentin expression similar to v-relER dendritic cells.

Alterations in tumor necrosis factor-alpha, interferon-gamma, and interleukin-6 production by natural killer cell-enriched peripheral blood mononuclear cells in chronic alcoholism: relationship with liver disease and ethanol intake.

No previous studies have been reported on human alcoholism in which the pattern of cytokine secretion by natural killer (NK) cells is explored. The goal of the present study was to evaluate the role of NK cells in the production of cytokines in patients with chronic alcoholism, analyzing at the same time the possible relationship between cytokine production and both alcoholic liver disease and ethanol (EtOH) intake. A total of 30 chronic alcoholic patients-11 without liver disease [alcoholics without liver disease (AWLD) group] and 19 diagnosed of alcoholic liver cirrhosis-were included in this study. Twenty-five age- and sex-matched healthy volunteers were analyzed as controls. Production of interferon (IFN)-gamma, tumor necrosis factor-alpha (TNF-alpha), and interleukin (IL)-6 was performed on NK-enriched peripheral blood mononuclear cells (PBMC) after stimulation with IL-2 and IFN-alpha. In AWLD patients, the production of TNF-alpha was significantly reduced, compared with normal controls, under both IFN-alpha (p < 0.01) and IL-2 (p < 0.05) stimulation. In patients with cirrhosis, TNF-alpha production by PBMC enriched in NK cells varied depending on the EtOH intake status at the moment of evaluation. Accordingly, an increased concentration of this cytokine was detected in the supernatants of cirrhotic patients and active EtOH intake, particularly after IFN-alpha stimulation (p < 0.05); whereas, in patients with at least 1 year of alcohol withdrawal, TNF-alpha levels remained within normal range. The results on the production of IL-6 and IFN-gamma in AWLD and cirrhotic patients showed that only cirrhotic patients with a prolonged EtOH withdrawal period display abnormal production. Accordingly, in this group of patients, a significantly increased release of IL-6 was observed after both IFN-alpha and IL-2 stimulation (p < 0.01 and p < 0.05, respectively). By contrast, a lower IFN-gamma production (p < 0.005) was detected with respect to the control group. Our results point to the existence of an abnormal cytokine secretion by NK cells from chronic alcoholism patients, which depend on both the existence of liver disease and the status of EtOH intake.

Abnormalities of peripheral blood T lymphocytes and natural killer cells in alcoholic hepatitis persist after a 3-month withdrawal period.

Present information about the behavior of the different lymphoid subsets in alcoholic hepatitis (AH), including cells displaying cytotoxic activity, is scanty and contradictory. The aim of this study was to gain further insight into knowledge of the immunological abnormalities involved in AH and the possible role of ethanol (EtOH) consumption in these changes. We analyzed the distribution of a wide range of peripheral blood (PB) lymphoid subsets, both during active EtOH intake and after a 3-month withdrawal period, using multiple stainings with monoclonal antibodies and flow cytometry, as well as natural killer (NK) cytotoxic activity. AH patients entering the study were selected strictly; only those undergoing their first episode of AH with no other lesions at liver biopsy were enrolled. Regarding the alcohol intake period, the most striking finding was a significant increase of the absolute number of PB T cells affecting both CD4+ and CD8+ lymphocytes. These changes were associated with a higher expression of T-cell activation antigens, such as HLA DR and CD11c. Simultaneously, a significant increase in both NK cells (CD3-/CD56+) and the cytotoxic T cells coexpressing the CD3 and the CD56 molecules together with an increased NK cytotoxic activity were observed. By contrast, the CD19+/CD5+ B-cell subset was significantly decreased. No significant changes were observed with EtOH withdrawal except in CD5+ B lymphocytes, which returned to normal values. Our results show that, in AH patients, a significant expansion of both activated T cells and NK lymphocytes occurs in the PB, which is associated with an increased NK cytotoxic activity. Interestingly these abnormalities persist during the withdrawal period.

Decreased natural killer cytotoxic activity in chronic alcoholism is associated with alcohol liver disease but not active ethanol consumption.

Chronic alcohol intake is associated with an increased incidence of certain neoplasms. Natural killer (NK) cells have been considered to be involved in control tumor development and growth. The goal of the present study was to contribute to a better understanding of the effects of ethanol (EtOH) per se on the NK-cell population. Both patients with chronic alcoholism without liver disease (AWLD) and subjects with alcohol-induced cirrhosis (ALC) were carefully selected for this study. Immunophenotypical and functional studies of peripheral blood (PB) NK-cells were performed during active EtOH intake and after 3 months of a withdrawal period. In the AWLD group a significant increase in number of NK-cells (CD3-/CD56+) (P < .05) associated with a parallel increase in NK-cell lytic activity (P < .01) was observed. In addition, the number of cytotoxic T cells displaying the CD3+/CD56+ phenotype as well as CD8-/CD57+ NK-cell subset was also increased (P < .01 and P < .001, respectively). By contrast, in ALC patients with active EtOH intake (ALCET group), although a significant increase in the number of NK PB lymphocytes was observed (P < .05), NK lytic activity was depressed (P < .05), suggesting the existence of a decreased lytic activity/NK-cell. After 3 months of EtOH withdrawal, PB mononuclear cells (PBMC) from the AWLD group patients still displayed an increased NK cytolytic activity; in addition, the number of PB NK-cells (CD3-/CD56+ and CD8-/CD57+) and CD3+/CD56+ PB T cells continued to be increased. Independently of the duration of withdrawal period, in ALC patients EtOH withdrawal was followed by a slight decrease in the NK lytic activity of PBMC with respect to the values in active alcoholism phase; slight differences observed in the NK lytic activity in ALC patients who quit drinking could be related to the tendency to decrease of the number of NK-cells toward normal values. Furthermore, although an increase in NK cytotoxic activity after stimulation of PBMC with interleukin-2 (IL-2) was observed in ALC, it did not reach the levels observed in healthy subjects. Overall, our results show that the behavior of PB NK-cell population in chronic alcoholism is different according to both the moment of EtOH consumption and the existence or not of ALC. Alcohol by itself induced an increase in the number and lytic activity of NK-cells. By contrast, the NK cytolytic activity is constantly depressed in the stage of alcoholic cirrhosis, supporting the notion that immunosurveillance mechanisms may be affected in these patients.

Sequential immunophenotypic analysis of mast cells in a case of systemic mast cell disease evolving to a mast cell leukemia.

The immunophenotypic characteristics of both bone marrow (BM) and peripheral blood (PB) mast cells (MC), from a patient suffering from an aggressive systemic mast cell disease (SMCD), were sequentially analyzed by flow cytometry using direct immunofluorescence. Analysis was carried out at diagnosis, during clinical response induced by interferon alfa-2h/prednisone therapy, and later at relapse. Our results show that together with the CD117 and IgE characteristic markers, at diagnosis BM MC showed strong expression of CD11c, CD13, CD29, CD33, CD44, CD45, CD63, and CD71, and they were also positive for CD2, CD22, CD25, and CD54 although at a lower level. PB MC displayed similar immunophenotypic characteristics although they had a lower expression of CD11c, CD25, CD33, CD63, CD69, and CD71 with a higher reactivity for CD117. Unlike BM MC, PB MC were weakly positive for CD41a and CD61. Sequential studies showed decreased numbers of both BM and PB MC during clinical response associated with a higher expression of the CD29 and CD54 adhesion molecules. In turn, clinical relapse was related to increased numbers of PB and BM MC together with lower CD2, CD11c, CD45, and and CD54 expression and a higher reactivity for the CD117 and CD25 antigens. CD2 had become negative at the last follow-up study. In addition, an increased proportion of S-phase MC was observed at relapse. These findings suggest that the assessment of the quantitative expression of cell-adhesion molecules and growth-factor receptors together with cell cycle studies of mast cells could be of value for monitoring therapy and predicting clinical outcome in aggressive SMCD.

Long lasting immunological effects of ethanol after withdrawal.

The aim of the present study was to analyze on chronic alcoholic patients the effect of ethanol (EtOH) withdrawal on the immune system through the investigation of the distribution of PB lymphoid subsets, using multiple-stainings with monoclonal antibodies and flow cytometry. For this purpose a group of 20 patients with active alcoholism without liver disease, negative for hepatitis virus, and without malnutrition was analyzed and followed for 9 months after alcohol consumption had been discontinued. Twenty-five age- and sex-matched healthy volunteers were included in the study. The following panel of monoclonal antibodies combinations (FITC/PE/PerCP or PE-Cy5) was used: TCR alpha beta/CD3/HLA DR, CD25/CD56/CD3, TCR gamma delta/CD3/HLA DR, CD45RA/CD45R0/CD4, CD3/CD8, CD19/CD5, and CD3/CD11c. Analysis was performed on at least 1,500 events/tube at flow cytometry using the Lysys II software program. During the alcohol intake period, the most striking findings were a significant (P < 0.05) expansion of the CD8+ T-lymphocyte subset, which coexpresses the activation associated antigens HLA DR and CD11c, as well as a significant increase in both NK-cells (CD3-/CD56+) and the T-cell subset with NK activity coexpressing CD3 and CD56 (P < 0.05 and P < 0.01, respectively). In addition, a decrease in the CD5+ B-cells (P < 0.05), associated with reduced serum gamma-globulin levels, was also observed. During alcohol withdrawal, a rapid decrease towards normal values of activated CD8+/HLA DR+ and CD11c+ T-lymphocytes was observed as well as a normalization of CD19+/CD5+ B-cells and gamma-globulin serum levels; these changes might be directly related to EtOH suppression. Surprisingly, however, new immunological imbalances emerged in spite of the absence of alcohol intake. Thus, a progressive and significant expansion (P < 0.05) of CD4+ T-cells associated with an increased expression of the CD25 activation-related antigen and a preferential use of the CD45R0 isoform by CD4+ T-cells were observed. In parallel, there was an even more evident increase (P < 0.01) in the number of PB NK-cells. Our results show that EtOH consumption induces changes in the immune system, its effects persisting or even becoming more evident after suppression of EtOH intake for a 9 month period.

Distribution of peripheral blood lymphoid subsets in alcoholic liver cirrhosis: influence of ethanol intake.

The aim of the present study was to investigate the effect of chronic ethanol (EtOH) consumption on the immune system in patients with alcoholic liver cirrhosis (ALC), as analyzed by the distribution of peripheral blood (PB-) T, B, and NK lymphoid subsets using multiple stainings with monoclonal antibodies and flow cytometry. For that purpose, we have analyzed a group of patients with ALC and active EtOH intake (ALCET group) which were re-evaluated 3 months after alcohol withdrawal. As controls, both ALC patients with at least 1 year of alcohol withdrawal (ALCAW group) and healthy subjects were used. Regarding the alcohol intake period, the most relevant findings were a significant activation of the PB T-cell compartment, and specifically of the TCR alpha beta + subset, as reflected by an increased expression of both the HLA DR and CD11c antigens as well as a significant increase of both the PB NK cells (CD3-/CD56+) and the cytotoxic T cells coexpressing the CD3 and CD56 molecules. In addition, a decrease of both the numbers of total B cells and their CD5+/CD19+ subset were observed. After a relatively short withdrawal period (3 months), the abnormalities of T, P, and NK cells disappeared. These findings suggest the existence of a close relationship between EtOH consumption and the abnormalities of the immune system observed during active alcoholism. Nevertheless, ALCAW individuals displayed marked alterations on the immunophenotypic profile, as reflected by a significantly decreased number of total T cells, due to reduced levels of the CD3+/TCR alpha beta+, CD4+, CD8+, and CD4+/CD45RA+ T-cell subsets. In addition, a significantly decreased number of total PB B cells was observed in this group of patients. Our results show that in patients suffering from ALC, the abnormalities of the immune system due to a direct effect of EtOH intake (or its metabolites) should be distinguished from the immunological alterations related to the liver disease itself.

Beyond belief bias: reasoning from conceptual structures by mental models manipulation.

Mental models constitute an alternative to the rule-based systems in the explanation of human reasoning (Johnson-Laird, 1983). In this paper, we claim that the concept of believability generally used to categorize content and context effects is of little use within a semantic theory. Thus, we propose the use of categories that are directly extracted from subjective relations among concepts within the reasoning problem. We demonstrate that manipulations based on this kind of categorization produce predictable patterns of responses in reasoning problems. We present two experiments to test our predictions, using conditional and syllogistic reasoning problems, and in both cases, we demonstrate the influence of conceptual knowledge not only in natural contexts, but also in experimentally created artificial contexts.

Dendritic cell progenitor is transformed by a conditional v-Rel estrogen receptor fusion protein v-RelER.

A conditional v-Rel estrogen receptor fusion protein, v-RelER, causes estrogen-dependent but otherwise unaltered v-rel-specific transformation of chicken bone marrow cells. Here, we demonstrate that such v-relER-transformed cells exhibit B lymphoid determinants in line with earlier studies on v-rel-transformed cells. However, following inactivation of v-RelER oncoprotein activity by administration of an estrogen antagonist, cells differentiate into antigen-presenting dendritic cells as judged by several morphological and functional criteria. Additionally, under yet different culture conditions, v-relER cells differentiate into cells resembling polymorphonuclear neutrophils. Our studies therefore suggest that the conditional v-RelER, and probably also the authentic v-Rel, transform a common progenitor for neutrophils and dendritic cells.

Adsorption-desorption of recombinant hepatitis B surface antigen (r-HBsAg) from P. pastoris on a diatomaceous earth matrix: Optimization of parameters for purification.

Recombinant hepatitis B surface antigen (r-HBsAg) produced in yeast is adsorbed on a diatomaceous earth matrix for purification purposes. A pH dependence in the adsorption-elution behavior was found. The capacity of celite (Hyflo Super Cei) for adsorbing r-HBsAg increased with decreasing pH. Nonspecific proteins were also adsorbed, but a low pH dependence was found. Elution from the matrix was performed using a basic pH buffer, in which r-HBsAg is more specifically adsorbed/desorbed than contaminant proteins, permitting the purification of the r-HBsAg. A pH of 4.0 was used for adsorption and pH 8.2 was used for desorption. The described protocol allows a purification factor between three- and fivefold with respect to contaminant proteins and sixfold with respect to contaminant DNA. Finally, the adsorption step was successfully scaled-up for production purposes.