Is Lactoferrin More Effective in Reducing Late-Onset Sepsis in Preterm Neonates Fed Formula Than in Those Receiving Mother's Own Milk? Secondary Analyses of Two Multicenter Randomized Controlled Trials.

BACKGROUND: Lactoferrin is the major antimicrobial protein in human milk. In our randomized controlled trial (RCT) of bovine lactoferrin (BLF) supplementation in preterm neonates, BLF reduced late-onset sepsis (LOS). Mother's own milk (MM) contains higher concentrations of lactoferrin than donor milk or formula, but whether BLF is more effective in infants who receive formula or donor milk is uncertain. AIM: To evaluate the incidence of LOS in preterm infants fed MM and in those fed formula and/or donor milk. STUDY DESIGN: This is a (A) post hoc subgroup analysis, in our RCT of BLF, of its effects in preterm infants fed MM, with or without formula, versus those fed formula and/or donor milk (no-MM) and (B) post hoc meta-analysis, in our RCT of BLF and in the ELFIN (Enteral Lactoferrin in Neonates) RCT, of the effect of BLF in subgroups not exclusively fed MM. RESULTS: (A) Of 472 infants in our RCT, 168 were randomized to placebo and 304 were randomized to BLF. Among MM infants, LOS occurred in 22/133 (16.5%) infants randomized to placebo and in 14/250 (5.6%) randomized to BLF (relative risk or risk ratio (RR): 0.34; relative risk reduction (RRR): 0.66; 95% confidence interval (95% CI) for RR: 0.18-0.64; p < 0.0008). Among no-MM infants, LOS occurred in 7/35 (20.0%) randomized to placebo and in 2/54 (3.7%) randomized to BLF (RR: 0.19; RRR: 0.81; 95% CI for RR: 0.16-0.96; p = 0.026). In multivariable logistic regression analysis, there was no interaction between BLF treatment effect and type of feeding (p = 0.628). (B) In 1,891 infants not exclusively fed MM in our RCT of BLF and in the ELFIN RCT, BLF reduced the RR of LOS by 18% (RR: 0.82; 95% CI: 0.71-0.96; p = 0.01). CONCLUSION: Adequately powered studies should address the hypothesis that BLF is more effective in infants fed formula or donor milk than those fed MM. Such studies should evaluate whether a specific threshold of total lactoferrin intake can be identified to protect such patients from LOS.

Exposure to Gastric Acid Inhibitors Increases the Risk of Infection in Preterm Very Low Birth Weight Infants but Concomitant Administration of Lactoferrin Counteracts This Effect.

OBJECTIVE: To investigate whether exposure to inhibitors of gastric acidity, such as H2 blockers or proton pump inhibitors, can independently increase the risk of infections in very low birth weight (VLBW) preterm infants in the neonatal intensive care unit. STUDY DESIGN: This is a secondary analysis of prospectively collected data from a multicenter, randomized controlled trial of bovine lactoferrin (BLF) supplementation (with or without the probiotic Lactobacillus rhamnosus GG) vs placebo in prevention of late-onset sepsis (LOS) and necrotizing enterocolitis (NEC) in preterm infants. Inhibitors of gastric acidity were used at the recommended dosages/schedules based on the clinical judgment of attending physicians. The distribution of days of inhibitors of gastric acidity exposure between infants with and without LOS/NEC was assessed. The mutually adjusted effects of birth weight, gestational age, duration of inhibitors of gastric acidity treatment, and exposure to BLF were controlled through multivariable logistic regression. Interaction between inhibitors of gastric acidity and BLF was tested; the effects of any day of inhibitors of gastric acidity exposure were then computed for BLF-treated vs -untreated infants. RESULTS: Two hundred thirty-five of 743 infants underwent treatment with inhibitors of gastric acidity, and 86 LOS episodes occurred. After multivariate analysis, exposure to inhibitors of gastric acidity remained significantly and independently associated with LOS (OR, 1.03; 95% CI, 1.008-1.067; P = .01); each day of inhibitors of gastric acidity exposure conferred an additional 3.7% odds of developing LOS. Risk was significant for Gram-negative (P < .001) and fungal (P = .001) pathogens, but not for Gram-positive pathogens (P = .97). On the test for interaction, 1 additional day of exposure to inhibitors of gastric acidity conferred an additional 7.7% risk for LOS (P = .003) in BLF-untreated infants, compared with 1.2% (P = .58) in BLF-treated infants. CONCLUSION: Exposure to inhibitors of gastric acidity is significantly associated with the occurrence of LOS in preterm VLBW infants. Concomitant administration of BLF counteracts this selective disadvantage. TRIAL REGISTRATION: isrctn.org: ISRCTN53107700.

Reduced cellular Ca(2+) availability enhances TDP-43 cleavage by apoptotic caspases.

Accumulation of transactive response DNA binding protein (TDP-43) fragments in motor neurons is a post mortem hallmark of different neurodegenerative diseases. TDP-43 fragments are the products of the apoptotic caspases-3 and -7. Either excessive or insufficient cellular Ca(2+) availability is associated with activation of apoptotic caspases. However, as far as we know, it is not described whether activation of caspases, due to restricted intracellular Ca(2+), affects TDP-43 cleavage. Here we show that in various cell lineages with restricted Ca(2+) availability, TDP-43 is initially cleaved by caspases-3 and -7 and then, also by caspases-6 and -8 once activated by caspase-3. Furthermore, we disclose the existence of a TDP-43 caspase-mediated fragment of 15kDa, in addition to the well-known fragments of 35 and 25kDa. Interestingly, with respect to the other two fragments this novel fragment is the major product of caspase activity on murine TDP-43 whereas in human cell lines the opposite occurs. This outcome should be considered when murine models are used to investigate TDP-43 proteinopathies.

Lung ultrasound: a useful tool in diagnosis and management of bronchiolitis.

BACKGROUND: Clinical assessment is the gold standard for diagnosis of bronchiolitis. To date, only one study found LUS (Lung Ultrasound) to be a valuable tool in the diagnosis of bronchiolitis. Aim of this study is to evaluate the accuracy of lung ultrasonography in the diagnosis and management of bronchiolitis in infants. METHODS: This was an observational cohort study of infants admitted to our Pediatric Unit with suspected bronchiolitis. A physical examination and lung ultrasound scans were performed on each patient. Diagnosis and grading of bronchiolitis was assessed according to a clinical and a ultrasound score. An exploratory analysis was used to assess correspondence between the lung ultrasound findings and the clinical evaluation and to evaluate the inter-observer concordance between the two different sonographs. RESULTS: One hundred six infants were studied (average age 71 days). According to our clinical score, 74 infants had mild bronchiolitis, 30 had moderate bronchiolitis and two had severe bronchiolitis. 25 infants composed the control group. Agreement between the clinical and sonographic diagnosis was good (90.6%) with a statistically significant inter-observer ultrasound diagnosis concordance (89.6%). Lung ultrasound permits the identification of infants who are in need of supplementary oxygen with a specificity of 98.7%, a sensitivity of 96.6%, a positive predictive value of 96.6% and a negative predictive value of 98.7%. An aberrant ultrasound lung pattern in posterior chest area was collected in 86% of infants with bronchiolitis. In all patients clinical improvement at discharge was associated with disappearance of the previous LUS findings. Subpleural lung consolidation of 1 cm or more in the posterior area scan and a quantitative classification of interstitial syndrome based on intercostal spaces involved bilaterally, good correlate with bronchiolitis severity and oxygen use. CONCLUSIONS: The lung ultrasound findings strictly correlate with the clinical evaluations in infants with bronchiolitis and permit the identification of infants who are in need of supplementary oxygen with high specificity. Scans of the posterior area are more indicative in ascertaining the severity of bronchiolitis. TRIAL REGISTRATION: Clinical Trial Registration NCT01993797.

Lutein and zeaxanthin supplementation in preterm very low-birth-weight neonates in neonatal intensive care units: a multicenter randomized controlled trial.

BACKGROUND: Human milk feeding protects against oxidative stress-induced damage in preterm neonates, including severe multifactorial diseases such as retinopathy of prematurity (ROP), necrotizing enterocolitis (NEC), and bronchopulmonary dysplasia (BPD). The carotenoids, which are not found in formula milk, might play a key role in these actions. METHODS: A multicenter, double-blind, randomized controlled trial was conducted in three tertiary Italian neonatal intensive care units. All preterm infants < 32(+6) weeks' gestational age were eligible and were randomized to a single, oral, daily 0.5-mL dose of carotenoid supplementation (0.14 mg lutein + 0.0006 mg zeaxanthin) or placebo (5% glucose solution) from birth till 36 weeks' corrected gestational age. Primary outcomes were threshold ROP, NEC > second stage, and BPD. Surveillance for detection of these diseases and for intolerance/adverse effects was performed. RESULTS: No treatment-related adverse effect was documented in the 229 analyzed infants, whose clinical/demographical characteristics were similar in the two groups. Threshold ROP incidence did not significantly differ in treated (6.2%) versus not treated infants (10.3%; p = 0.18). The same occurred for NEC (1.7% versus 5.1%; p = 0.15) and BPD (4.5% versus 10.3%; p = 0.07). Noteworthy, the progression rate from early ROP stages to threshold ROP was decreased by 50% (0.30 versus 0.44; p = 0.23). CONCLUSION: Lutein/zeaxanthin supplementation in preterm infants is well tolerated. No significant effect was seen on threshold ROP, NEC, or BPD. The decreasing trends of these outcomes in the treatment group need to be assessed and confirmed on larger sample-sizes.

Prevention of nosocomial infections in neonatal intensive care units.

Neonatal sepsis causes a huge burden of morbidity and mortality and includes bloodstream, urine, cerebrospinal, peritoneal, and lung infections as well as infections starting from burns and wounds, or from any other usually sterile sites. It is associated with cytokine - and biomediator-induced disorders of respiratory, hemodynamic, and metabolic processes. Neonates in the neonatal intensive care unit feature many specific risk factors for bacterial and fungal sepsis. Loss of gut commensals such as Bifidobacteria and Lactobacilli spp., as occurs with prolonged antibiotic treatments, delayed enteral feeding, or nursing in incubators, translates into proliferation of pathogenic microflora and abnormal gut colonization. Prompt diagnosis and effective treatment do not protect septic neonates form the risk of late neurodevelopmental impairment in the survivors. Thus prevention of bacterial and fungal infection is crucial in these settings of unique patients. In this view, improving neonatal management is a key step, and this includes promotion of breast-feeding and hygiene measures, adoption of a cautious central venous catheter policy, enhancement of the enteric microbiota composition with the supplementation of probiotics, and medical stewardship concerning H2 blockers with restriction of their use. Additional measures may include the use of lactoferrin, fluconazole, and nystatin and specific measures to prevent ventilator associated pneumonia.

Lactoferrin for prevention of neonatal infections.

PURPOSE OF REVIEW: Sepsis-related morbidity and mortality is an increasing concern in all neonatal ICUs (NICUs). Sepsis occurs in 20-40% of all preterm patients, and although much is known on the origin, the incidence is reported to be constantly increasing. Many risk factors account for the increased risk of sepsis in preterms, including use of broad-spectrum antibiotics selecting resistant microflora and pathogenic gut colonization, parenteral nutrition, acid inhibitors and steroids, as well as the systematic and long-lasting use of invasive management and in-dwelling lines. As treatment does not prevent severe long-term neurodevelopmental impairment and sequelae in septic premature neonates, the best strategy is to avoid infections rather than to treat them. RECENT FINDINGS: Published results from several recent randomized controlled trials currently show a level I evidence that fluconazole for prevention of fungal sepsis, probiotics for prevention of necrotizing enterocolitis, and bovine lactoferrin for prevention of bacterial sepsis should be considered as preventive strategies in NICUs. SUMMARY: In this article, the current evidence in favour of lactoferrin use in preterm neonates will be reviewed and the areas of further research and future improvements will be discussed in order to illustrate the implications of the recent findings for clinical practice or research.

A multicenter, randomized trial of prophylactic fluconazole in preterm neonates.

BACKGROUND: Invasive candida infections are a major cause of morbidity and mortality in preterm infants. We performed a multicenter, randomized, double-blind, placebo-controlled trial of fluconazole for the prevention of fungal colonization and infection in very-low-birth-weight neonates. METHODS: During a 15-month period, all neonates weighing less than 1500 g at birth from eight tertiary Italian neonatal intensive care units (322 infants) were randomly assigned to receive either fluconazole (at a dose of either 6 mg or 3 mg per kilogram of body weight) or placebo from birth until day 30 of life (day 45 for neonates weighing <1000 g at birth). We performed weekly surveillance cultures and systematic fungal susceptibility testing. RESULTS: Among infants receiving fluconazole, fungal colonization occurred in 9.8% in the 6-mg group and 7.7% in the 3-mg group, as compared with 29.2% in the placebo group (P<0.001 for both fluconazole groups vs. the placebo group). The incidence of invasive fungal infection was 2.7% in the 6-mg group and 3.8% in the 3-mg group, as compared with 13.2% in the placebo group (P=0.005 for the 6-mg group and P=0.02 for the 3-mg group vs. the placebo group). The use of fluconazole did not modify the relationship between colonization and the subsequent development of invasive fungal infection. Overall mortality was similar among groups, as was the incidence of cholestasis. No evidence for the emergence of resistant candida species was observed, but the study did not have substantial power to detect such an effect. CONCLUSIONS: Prophylactic fluconazole reduces the incidence of colonization and invasive candida infection in neonates weighing less than 1500 g at birth. The benefit of treating candida colonization is unclear. (Current Controlled Trials number, ISRCTN85753869 [controlled-trials.com]).

[Recent advances in prevention of sepsis in the preterm neonate]. / Nuove strategie di prevenzione delle infezioni nel neonato pretermine.

An episode of sepsis occurs in 20 to 40% of all preterm patients, and such figures have been reported constantly increasing in Neonatal Intensive Care Units. Neonatal sepsis include bloodstream, urine, cerebrospinal, peritoneal infections, infections starting from burns and wounds, or from any other usually sterile sites. Many specific risk factors account for the increased risk of sepsis, including employment of broad-spectrum antibiotics selecting resistant microflora, parenteral nutrition, acid inhibitors and steroids, as well as the systematic and long-lasting use of invasive management. In preterm neonates, loss of gut commensals such as bifidobacteria and lactobacilli, due to the difficulties in oral feeding, or a slower acquisition of them, translates into an increased susceptibility to pathogenic gut colonization. Prompt diagnosis, effective treatment, and specific prophylaxis with antibacterial and antifungal drugs are the milestones of management of these life-threatening events. This article discusses the recent advances in prevention and shows how fluconazole for prevention of fungal sepsis, probiotics for prevention of necrotizing enterocolitis, and bovine lactoferrin for prevention of bacterial sepsis may be considered as effective preventive strategies.

Detection of SARS-CoV-2 in Milk From COVID-19 Positive Mothers and Follow-Up of Their Infants.

Background: In the current SARS-Coronavirus-2 (SARS-CoV-2) pandemic little is known about SARS-CoV-2 in human milk. It is important to discover if breast milk is a vehicle of infection. Objective: Our aim was to look for the presence of SARS-CoV-2 RNA in the milk of a group of SARS-CoV-2 positive mothers from North-West Italy. Methods: This is a prospective collaborative observational study where samples of human milk from 14 breastfeeding mothers positive for SARS-CoV-2 were collected. A search of viral RNA in breast milk samples was performed by RT-PCR (Real-Time reverse-transcriptase-Polymerase-Chain-Reaction) methodology tested for human milk. All the newborns underwent a clinical follow up during the first month of life or until the finding of two sequential negative swabs. Results: In 13 cases the search for SARS-CoV-2 RNA in milk samples resulted negative and in one case it was positive. Thirteen of the 14 newborns were exclusively breastfed and closely monitored in the first month of life. Clinical outcome was uneventful. Four newborns tested positive for SARS-CoV-2 and were all detected in the first 48 h of life, after the onset of maternal symptoms. Also the clinical course of these 4 infants, including the one who received mother's milk positive for SARS-CoV-2, was uneventful, and all of them became SARS-CoV-2 negative within 6 weeks of life. Conclusion: Our study supports the view that SARS-CoV-2 positive mothers do not expose their newborns to an additional risk of infection by breastfeeding.

Is thrombocytopenia suggestive of organism-specific response in neonatal sepsis?

BACKGROUND: It is controversial whether thrombocytopenia is suggestive of one (or more) causative agents of neonatal sepsis: a low platelet count has been related in turn to Gram-positive, Gram-negative or fungal sepsis. METHODS: A retrospective, cohort study on 514 very low-birthweight (VLBW) neonates admitted over a 9 year period to a large tertiary neonatal intensive care unit (NICU) in Italy was carried out. Through database search, data on platelet counts, sepsis, clinical course, and microbiological culture were collected and analyzed. Statistical analysis was performed to look for significant association between thrombocytopenia and sepsis caused by different (Gram-positive, Gram-negative or fungal) organisms. RESULTS: Sepsis diagnosed on microbiological criteria occurred in 197 of 514 VLBW neonates (38.3%), and thrombocytopenia (at least one finding of platelet count <80,000/mm(3)) was detected in 34 (17.2%) of the 197 septic infants. Thrombocytopenia occurred in 10 of 51 neonates with fungal sepsis (19.6%), and in 24 of 146 with bacterial sepsis (16.4%; P = 0.37). The difference was not significant when clustering for sepsis caused by Gram-positive (nine thrombocytopenic of 51 with Gram-positive sepsis, 17.6%; P = 0.40) and Gram-negative organisms (15/95, 15.7%; P = 0.22), or when considering only coagulase-negative Staphylococcus sepsis (6/37, 16.2%; P = 0.25). CONCLUSIONS: In contrast with previous reports, thrombocytopenia might not be an organism-specific marker of sepsis. Caution should be maintained in relating a low platelet count to any infectious agent (or group of agents) in preterm VLBW neonates.

Bovine lactoferrin supplementation for prevention of late-onset sepsis in very low-birth-weight neonates: a randomized trial.

CONTEXT: Sepsis is a common and severe complication in premature neonates, particularly those with very low birth weight (VLBW) (<1500 g). Whether lactoferrin, a mammalian milk glycoprotein involved in innate immune host defenses, can reduce the incidence of sepsis is unknown. In animal models, the probiotic Lactobacillus rhamnosus GG (LGG) enhances the activity of lactoferrin but has not been studied in human infants. OBJECTIVE: To establish whether bovine lactoferrin (BLF), alone or in combination with LGG, reduces the incidence of late-onset sepsis in VLBW neonates. DESIGN, SETTING, AND PATIENTS: Prospective, multicenter, double-blind, placebo-controlled, randomized trial conducted in 11 Italian tertiary neonatal intensive care units. Patients were 472 VLBW infants enrolled from October 1, 2007, through July 31, 2008, and assessed until discharge for development of sepsis. INTERVENTION: Infants were randomly assigned to receive orally administered BLF (100 mg/d) alone (n = 153), BLF plus LGG (6 x 10(9) colony-forming units/d) (n = 151), or placebo (n = 168) from birth until day 30 of life (day 45 for neonates <1000 g at birth). MAIN OUTCOME MEASURE: First episode of late-onset sepsis, ie, sepsis occurring more than 72 hours after birth with isolation of any pathogen from blood or from peritoneal or cerebrospinal fluid. RESULTS: Demographic, clinical, and management characteristics of the 3 groups were similar, including type of feeding and intake of maternal milk. Incidence of late-onset sepsis was significantly lower in the BLF and BLF plus LGG groups (9/153 [5.9%] and 7/151 [4.6%], respectively) than in the control group receiving placebo (29/168 [17.3%]) (risk ratio, 0.34; 95% confidence interval, 0.17-0.70; P = .002 for BLF vs control and risk ratio, 0.27; 95% confidence interval, 0.12-0.60; P < .001 for BLF plus LGG vs control). The decrease occurred for both bacterial and fungal sepsis. No adverse effects or intolerances to treatment occurred. CONCLUSION: Compared with placebo, BLF supplementation alone or in combination with LGG reduced the incidence of a first episode of late-onset sepsis in VLBW neonates. TRIAL REGISTRATION: isrctn.org Identifier: ISRCTN53107700.

Routine use of fluconazole prophylaxis in a neonatal intensive care unit does not select natively fluconazole-resistant Candida subspecies.

BACKGROUND: We have previously demonstrated efficacy against fungal colonization and infection of fluconazole prophylaxis that was routinely administered since 2001 in our ICU for preterm infants <1500 g at birth (VLBW). With prolonged use, concerns exist for the emergence of acquired fungal resistance and of Candida subspecies that are natively fluconazole-resistant (NFR), mostly Candida glabrata and Candida krusei. METHODS: We evaluated retrospectively all clinical and surveillance fungal isolates obtained from VLBW infants in our NICU during a 10-year period (1997-2006). Each fungal isolate was speciated, infants colonized or infected with NFR-Candida spp were identified and the incidence rates of colonization and infection by these fungal species were calculated. A comparison was made of the 6-year (2001-2006) prophylaxis period with the 4-year (1997-2000) preprophylaxis period. RESULTS: Overall, colonization by NFR-Candida spp ranged between 2.8% and 6.6% of VLBW infants yearly admitted, without any increasing trend during the study period. There were 18 of 434 (4.1%) neonates colonized by these species. Five episodes of systemic fungal infections caused by NFR-Candida spp occurred (incidence rate, 1.1%). No significant differences were detected when compared with the preprophylaxis period, when 11 of 295 infants (3.7%) were colonized by NFR-Candida spp and 4 episodes of infection occurred (1.4%) (P = 0.84 and 0.76, respectively). CONCLUSIONS: Fluconazole prophylaxis administered to VLBW neonates in 4- to 6-week courses after birth does not lead to the emergence of natively fluconazole-resistant Candida spp.

The HIV protease inhibitors nelfinavir and saquinavir, but not a variety of HIV reverse transcriptase inhibitors, adversely affect human proteasome function.

BACKGROUND: In HIV-infected patients some clinical and immunological benefits of antiretroviral therapy, which frequently include a combination of HIV protease inhibitors (PIs) and reverse transcriptase inhibitors (RTIs), cannot be solely explained by the drugs' action on viral enzymes. Proteasomes constitute the central protease of the ubiquitin ATP-dependent pathway involved in many cellular processes, as well as in HIV maturation and aggressiveness. OBJECTIVE: To explore whether the PIs nelfinavir and saquinavir and the RTIs abacavir, nevirapine, delavirdine, stavudine and didanosine affect proteasome function in vitro and in vivo. METHODS: Peptidase activity of purified human 26S and 20S proteasomes was assayed with and without the drugs at different concentrations. Intracellular proteasome proteolytic activity was evaluated by searching for ubiquitin-tagged proteins in HL60 cells incubated with and without the drugs. RESULTS: At therapeutic dosages, nelfinavir and saquinavir inhibited proteasome peptidase activity and caused intracellular accumulation of polyubiquitinated proteins, a hallmark of proteasome proteolytic inhibition in vivo; the RTIs failed to evoke either effect. CONCLUSION: Proteasomes are targeted by the two PIs but not the RTIs. Therefore, in HIV-infected patients the beneficial effect of a therapy including one of the two PIs should partly rely on inhibition of host proteasome function.

Pyogenic Granuloma of the Sigmoid Colon causing Intussusception in an Infant.

Pyogenic granuloma is a benign vascular tumor that may affect the gastrointestinal tract. This report describes a rare case of sigmoid-colon pyogenic granuloma in a 4-month-old boy causing intussusception. Resection and anastomosis were curative. The mother had history of high dose of progesterone exposure during initial weeks of conception for vaginal bleeding. This may point towards etiology of the lesion.

The human 26S proteasome is a target of antiretroviral agents.

BACKGROUND: Proteasomes constitute the degradative machinery of the ubiquitin/adenosine triphosphate-dependent proteolytic pathway, which is involved in many cell functions, including immune response and apoptosis, and in HIV maturation and infectivity. OBJECTIVE: To examine whether proteasomes are targeted by antiretroviral agents. METHODS: Chymotrypsin-like, trypsin-like and peptidyl-glutamyl-peptide hydrolysing activities of purified human 26S and 20S proteasomes, the latter depleted or enriched in 11S regulator, were assayed after incubation with indinavir, lamivudine and zidovudine at 1-80 microM alone and in combination. To assess the drug effects on cellular functions regulated by proteasomes, the accumulation of ubiquitin-tagged proteins, the processing of the nuclear factor kappa B precursor p105, and the degradation of the inhibitor of nuclear factor kappa B, isoform alpha (IkappaBalpha) were evaluated by Western immunoblotting in Jurkat cells after incubation for 6 h with the drugs above. RESULTS: Trypsin-like and mostly chymotrypsin-like activities of purified 26S proteasome were inhibited by each drug from 10 to 80 microM, more by double combinations and mostly by the triple combination. The peptidyl-glutamyl-peptide hydrolysing activity of the 26S proteasome and the three peptidase activities of the 20S proteasome, depleted or enriched in 11S regulator, were unaffected. The accumulation of ubiquitin-tagged proteins, reduced IkappaBalpha degradation and p105 processing were appreciable in intact cells with the triple drug combination. CONCLUSION: The human 26S proteasome is a target of antiretroviral agents. This suggests that the antiviral action and some clinical and immunological benefits of combined antiretroviral therapy rely not only on its known effects on viral enzymes, but also on host cell components.

Proteasomes as drug targets.

The ubiquitin-proteasome pathway plays a role in the degradation of the bulk of proteins in the cytoplasmic and nuclear compartments. In this pathway proteins are targeted for degradation by covalent ligation with ubiquitin, a reaction that requires ATP. Following the binding of the first ubiquitin molecule with the epsilon-amino group of a lysine residue of the substrate protein, a polyubiquitin chain is usually formed, in which the C-terminus of each ubiquitin unit is linked to a specific Lys residue of the previous ubiquitin. Central to this pathway is the 26S proteasome, a high molecular mass multifunctional protease which requires ATP for its catalytic activity. Substrates of the 26S proteasome are not only old or damaged proteins, but also short lived proteins functioning as regulatory factors in a large array of cellular processes, such as cell cycle progression, cell growth and gene expression, inflammatory response and immune surveillance. A number of inhibitors of the catalytic activity of proteasomes have been developed and successfully employed in the study of their functional and structural properties, as well as of their involvement in different cellular processes. Some of these molecules due to their toxicity are used only as experimental research tools; others instead are now in clinical trials for treatment of a variety of hematologic malignancies and solid tumors and of reperfusion injury occurring after cerebral ischemia and myocardial infarction. Furthermore, proteasome inhibitors are described to interfere with HIV maturation, budding and aggressiveness, and cytostatic drugs, as well as antiretroviral agents used in HAART, have been shown to behave in vitro and in cultured cell lines as inhibitors of proteasome proteolytic activity at therapeutic dosages.

Interferon-gamma-inducible subunits are incorporated in human brain 20S proteasome.

In most tissues expressing MHC class I molecules, proteasomes incorporating IFN-gamma-inducible subunits, defined immuno-proteasomes, exist together with constitutive proteasomes. In physiological conditions, the central nervous system expresses neither MHC class I molecules nor TAP1 and TAP2 transporters but besides being constitutive, it is unknown whether immuno-proteasomes are also present in this tissue. We present evidence that in human brain, the two types of proteasome exist suggesting that under physiological conditions, the mechanisms regulating expression of IFN-gamma-inducible subunits as well as of MHC class I molecules and TAP1 and TAP2 transporters in nervous tissue, are not entirely coordinated.