An up-scaled biotechnological approach for phosphorus-depleted rye bran as animal feed

Side streams from the milling industry offer excellent nutritional properties for animal feed; yet their use is constrained by the elevated phosphorus (P) content, mainly in the form of phytate. Biotechnological P recovery fosters sustainable P management, transforming these streams into P-depleted animal feed through enzymatic hydrolysis. The enzymatic P mobilization not only enables P recovery from milling by-products but also supports the valorization of these streams into P-depleted animal feeds. Our study presents the scalability and applicability of the process and characterizes the resulting P-depleted rye bran as animal feed component. Batch mode investigations were conducted to mobilize P from 100 g to 37.1 kg of rye bran using bioreactors up to 400 L. P reductions of 89% to 92% (reducing from 12.7 gP/kg to 1.41-1.28 gP/kg) were achieved. In addition, High Performance Ion Chromatography (HPIC) analysis showed complete depletion of phytate. The successful recovery of the enzymatically mobilized P from the process wastewater by precipitation as struvite and calcium hydrogen phosphate is presented as well, achieving up to 99% removal efficiency. Our study demonstrates a versatile process that is easily adaptable, allowing for a seamless implementation on a larger scale.

Evolution of E. coli Phytase Toward Improved Hydrolysis of Inositol Tetraphosphate

Protein engineering campaigns are driven by the demand for superior enzyme performance under non-natural process conditions, such as elevated temperature or non-neutral pH, to achieve utmost efficiency and conserve limited resources. Phytases are industrial relevant feed enzymes that contribute to the overall phosphorus (P) management by catalyzing the stepwise phosphate hydrolysis from phytate, which is the main phosphorus storage in plants. Phosphorus is referred to as a critical disappearing nutrient, emphasizing the urgent need to implement strategies for a sustainable circular use and recovery of P from renewable resources. Engineered phytases already contribute today to an efficient phosphorus mobilization in the feeding industry and might pave the way to a circular P-bioeconomy. To date, a bottleneck in its application is the drastically reduced hydrolysis on lower phosphorylated reaction intermediates (lower inositol phosphates, ≤InsP4) and their subsequent accumulation. Here, we report the first KnowVolution campaign of the E. coli phytase toward improved hydrolysis on InsP4 and InsP3. As a prerequisite prior to evolution, a suitable screening setup was established and three isomers Ins(2,4,5)P3, Ins(2,3,4,5)P4 and Ins(1,2,5,6)P4 were generated through enzymatic hydrolysis of InsP6 and subsequent purification by HPLC. Screening of epPCR libraries identified clones with improved hydrolysis on Ins(1,2,5,6)P4 carrying substitutions involved in substrate binding and orientation. Saturation of seven positions and screening of, in total, 10,000 clones generated a dataset of 46 variants on their activity on all three isomers. This dataset was used for training, testing, and inferring models for machine learning guided recombination. The PyPEF method used allowed the prediction of recombinants from the identified substitutions, which were analyzed by reverse engineering to gain molecular understanding. Six variants with improved InsP4 hydrolysis of >2.5 were identified, of which variant T23L/K24S had a 3.7-fold improved relative activity on Ins(2,3,4,5)P4 and concomitantly shows a 2.7-fold improved hydrolysis of Ins(2,4,5)P3. Reported substitutions are the first published Ec phy variants with improved hydrolysis on InsP4 and InsP3.

A Screening Method for P450 BM3 Mutant Libraries Using Multiplexed Capillary Electrophoresis for Detection of Enzymatically Converted Compounds

Capillary electrophoresis (CE) is an analytical method in which charged species are separated by attraction or repulsion performed in submillimeter diameter capillaries or micro- and nanofluidic channels through the application of a high voltage electric field. When capillary electrophoresis is assembled in a multicapillary instrument such as 96-well format (multiplexed), it becomes a powerful high-throughput system with the ability to simultaneously screen several types of samples like genetic mutations, metabolomes, kinase inhibitors, or enzymatic activities to name a few. The usage of a 96-multiplexed capillary electrophoresis system (96-MP-CE) represents a new platform for product-specific high-throughput screening of enzyme mutant libraries from directed evolution campaigns providing a comprehensive view on enzyme activity through the detection of all products formed. We describe the application of 96-MP-CE to screen mutant libraries of P450 BM3. MP-CE was used in directed evolution campaigns toward benzo-1,4-dioxane and α-isophorone.

Phytase blends for enhanced phosphorous mobilization of deoiled seeds

Phytases are hydrolytic enzymes capable of a stepwise phosphate release from phytate which is the main phosphorous storage in seeds, cereals and legumes. Limitations such as low enzyme activity or incomplete phytate hydrolysis to inositol are a great challenge in phytase applications in food and feed. Herein we report a phytase blend of two enzymes with additive effects on phytate (InsP6) hydrolysis and its application in the enzymatic phosphorous recovery process. Blending the fast 6-phytase rPhyXT52 with the 3-phytase from Debaryomyces castellii, which is capable of fully hydrolyzing InsP6, we achieved rapid phosphate release with higher yields compared to the individual enzymes and a rapid disappearance of InsP6-3 intermediates, monitored by HPLC. NMR data suggest a nearly complete phytate hydrolysis to inositol and phosphate. The blend was applied for phosphate mobilization from phytate-rich biomass, such as deoiled seeds. For this emerging application, an up to 43% increased phosphate mobilization yield was achieved when using 1000 U of the blend per kg biomass compared to using only the E. coli phytase. Even so, the time of enzyme treatment was decreased by more than half (6 h instead of 16 h) when using 4000 U of blend, we reached a 78-90% reduction of the total phosphorous content in the explored deoiled seeds. In summary, the phytase blend of Dc phyt/rPhyXT52 was proven very efficient to obtain inositol phosphate depleted meal which has its potential application in animal feeding and is concomitant with the production of green phosphate from renewable resources.

Generation of phytase chimeras with low sequence identities and improved thermal stability

Being able to recombine more than two genes with four or more crossover points in a sequence independent manner is still a challenge in protein engineering and limits our capabilities in tailoring enzymes for industrial applications. By computational analysis employing multiple sequence alignments and homology modeling, five fragments of six phytase genes (sequence identities 31-64 %) were identified and efficiently recombined through phosphorothioate-based cloning using the PTRec method. By combinatorial recombination, functional phytase chimeras containing fragments of up to four phytases were obtained. Two variants (PTRec 74 and PTRec 77) with up to 32 % improved residual activity (90 °C, 60 min) and retained specific activities of > 1100 U/mg were identified. Both variants are composed of fragments from the phytases of Citrobacter braakii, Hafnia alvei and Yersinia mollaretii. They exhibit sequence identities of ≤ 80 % to their parental enzymes, highlighting the great potential of DNA recombination strategies to generate new enzymes with low sequences identities that offer opportunities for property right claims.

Insights on intermolecular FMN-heme domain interaction and the role of linker length in cytochrome P450cin fusion proteins

Cytochrome P450s are an important group of enzymes catalyzing hydroxylation, and epoxidations reactions. In this work we describe the characterization of the CinA-CinC fusion enzyme system of a previously reported P450 using genetically fused heme (CinA) and FMN (CinC) enzyme domains from Citrobacter braaki. We observed that mixing individually inactivated heme (-) with FMN (-) domain in the CinA-10aa linker - CinC fusion constructs results in recovered activity and the formation of (2S)-2β-hydroxy,1,8-cineole (174 µM), a similar amount when compared to the fully functional fusion protein (176 µM). We also studied the effect of the fusion linker length in the activity complementation assay. Our results suggests an intermolecular interaction between heme and FMN parts from different CinA-CinC fusion protein similar to proposed mechanisms for P450 BM3 on the other hand, linker length plays a crucial influence on the activity of the fusion constructs. However, complementation assays show that inactive constructs with shorter linker lengths have functional subunits, and that the lack of activity might be due to incorrect interaction between fused enzymes.

KnowVolution of prodigiosin ligase PigC towards condensation of short-chain prodiginines

One round of KnowVolution enhanced the catalytic activity of prodigiosin ligase PigC with short-chain monopyrroles, opening access to anticancer prodiginines.

Understanding substrate binding and the role of gatekeeping residues in PigC access tunnels

Prodigiosin ligase PigC has been engineered by semi-rational design to accept short chain-pyrroles, providing molecular understanding of access tunnels and the substrate-binding pocket.

Reversal of Regioselectivity in Zinc-Dependent Medium-Chain Alcohol Dehydrogenase from Rhodococcus erythropolis toward Octanone Derivatives

The zinc-dependent medium-chain alcohol dehydrogenase from Rhodococcus erythropolis (ReADH) is one of the most versatile biocatalysts for the stereoselective reduction of ketones to chiral alcohols. Despite its known broad substrate scope, ReADH only accepts carbonyl substrates with either a methyl or an ethyl group adjacent to the carbonyl moiety; this limits its use in the synthesis of the chiral alcohols that serve as a building blocks for pharmaceuticals. Protein engineering to expand the substrate scope of ReADH toward bulky substitutions next to carbonyl group (ethyl 2-oxo-4-phenylbutyrate) opens up new routes in the synthesis of ethyl-2-hydroxy-4-phenylbutanoate, an important intermediate for anti-hypertension drugs like enalaprilat and lisinopril. We have performed computer-aided engineering of ReADH toward ethyl 2-oxo-4-phenylbutyrate and octanone derivatives. W296, which is located in the small binding pocket of ReADH, sterically restricts the access of ethyl 2-oxo-4-phenylbutyrate, octan-3-one or octan-4-one toward the catalytic zinc ion and thereby limits ReADH activity. Computational analysis was used to identify position W296 and site-saturation mutagenesis (SSM) yielded an improved variant W296A with a 3.6-fold improved activity toward ethyl 2-oxo-4-phenylbutyrate when compared to WT ReADH (ReADH W296A: 17.10 U/mg and ReADH WT: 4.7 U/mg). In addition, the regioselectivity of ReADH W296A is shifted toward octanone substrates. ReADH W296A has a more than 16-fold increased activity toward octan-4-one (ReADH W296A: 0.97 U/mg and ReADH WT: 0.06 U/mg) and a more than 30-fold decreased activity toward octan-2-one (ReADH W296A: 0.23 U/mg and ReADH WT: 7.69 U/mg). Computational and experimental results revealed the role of position W296 in controlling the substrate scope and regiopreference of ReADH for a variety of carbonyl substrates.

A colourimetric high-throughput screening system for directed evolution of prodigiosin ligase PigC

A colourimetric high-throughput screening system was developed for the first directed evolution campaign on PigC towards production of artificial prodiginines.

Directed Evolution of P450 BM3 towards Functionalization of Aromatic O-Heterocycles

The O-heterocycles, benzo-1,4-dioxane, phthalan, isochroman, 2,3-dihydrobenzofuran, benzofuran, and dibenzofuran are important building blocks with considerable medical application for the production of pharmaceuticals. Cytochrome P450 monooxygenase (P450) Bacillus megaterium 3 (BM3) wild type (WT) from Bacillus megaterium has low to no conversion of the six O-heterocycles. Screening of in-house libraries for active variants yielded P450 BM3 CM1 (R255P/P329H), which was subjected to directed evolution and site saturation mutagenesis of four positions. The latter led to the identification of position R255, which when introduced in the P450 BM3 WT, outperformed all other variants. The initial oxidation rate of nicotinamide adenine dinucleotide phosphate (NADPH) consumption increased ≈140-fold (WT: 8.3 ± 1.3 min-1; R255L: 1168 ± 163 min-1), total turnover number (TTN) increased ≈21-fold (WT: 40 ± 3; R255L: 860 ± 15), and coupling efficiency, ≈2.9-fold (WT: 8.8 ± 0.1%; R255L: 25.7 ± 1.0%). Computational analysis showed that substitution R255L (distant from the heme-cofactor) does not have the salt bridge formed with D217 in WT, which introduces flexibility into the I-helix and leads to a heme rearrangement allowing for efficient hydroxylation.

A hydroquinone-specific screening system for directed P450 evolution

The direct hydroxylation of benzene to hydroquinone (HQ) under mild reaction conditions is a challenging task for chemical catalysts. Cytochrome P450 (CYP) monooxygenases are known to catalyze the oxidation of a variety of aromatic compounds with atmospheric dioxygen. Protein engineering campaigns led to the identification of novel P450 variants, which yielded improvements in respect to activity, specificity, and stability. An effective screening strategy is crucial for the identification of improved enzymes with desired characteristics in large mutant libraries. Here, we report a first screening system designed for screening of P450 variants capable to produce hydroquinones. The hydroquinone quantification assay is based on the interaction of 4-nitrophenylacetonitrile (NpCN) with hydroquinones under alkaline conditions. In the 96-well plate format, a low detection limit (5 μM) and a broad linear detection range (5 to 250 μM) were obtained. The NpCN assay can be used for the quantification of dihydroxylated aromatic compounds such as hydroquinones, catechols, and benzoquinones. We chose the hydroxylation of pseudocumene by P450 BM3 as a target reaction and screened for improved trimethylhydroquinone (TMHQ) formation. The new P450 BM3 variant AW2 (R47Q, Y51F, I401M, A330P) was identified by screening a saturation mutagenesis library of amino acid position A330 with the NpCN assay. In summary, a 70-fold improved TMHQ formation was achieved with P450 BM3 AW2 when compared to the wild type (WT) and a 1.8-fold improved TMHQ formation compared to the recently reported P450 BM3 M3 (R47S, Y51W, A330F, I401M).

Tuberculosis along the continuum of HIV care in a cohort of adolescents living with HIV in Ethiopia

SETTING

Eight health facilities in Ethiopia.

OBJECTIVE

To determine tuberculosis (TB) incidence rates and associated factors among adolescents living with the human immunodeficiency virus (ALHIV).

DESIGN

This was a retrospective cohort study. Adolescents enrolled in HIV care between January 2005 and 31 December 2013 constituted the study population. The main outcome variable was TB diagnosis during follow-up. Baseline World Health Organization (WHO) clinical stage, CD4 count, previous history of TB and use of isoniazid preventive therapy (IPT) were the main independent variables. We estimated TB incidence rates as incident cases per 100 person-years of observation (PYO). Cox regression analysis was used to control for confounders.

RESULTS

Of the 1221 adolescents screened, 1072 were studied; 60.1% were girls. TB incidence rate was 16.32 per 100 PYO during pre-antiretroviral therapy (pre-ART) follow-up but declined to 2.25 per 100 PYO after initiation of ART. Advanced WHO clinical stage (adjusted hazard ratio [aHR] 2.71, 95%CI 1.69-4.33) and CD4 count <350 cells/μl (aHR 2.28, 95%CI 1.10-4.81) predicted TB incidence in the pre-ART cohort. IPT use was associated with a significant reduction in TB incidence in the ART cohort, but not in the pre-ART group.

CONCLUSION

Although TB was a significant problem in ALHIV, timely administration of ART and IPT had a significant protective effect.

An Enzymatic Route to α-Tocopherol Synthons: Aromatic Hydroxylation of Pseudocumene and Mesitylene with P450 BM3

Aromatic hydroxylation of pseudocumene (1 a) and mesitylene (1 b) with P450 BM3 yields key phenolic building blocks for α-tocopherol synthesis. The P450 BM3 wild-type (WT) catalyzed selective aromatic hydroxylation of 1 b (94 %), whereas 1 a was hydroxylated to a large extent on benzylic positions (46-64 %). Site-saturation mutagenesis generated a new P450 BM3 mutant, herein named "variant M3" (R47S, Y51W, A330F, I401M), with significantly increased coupling efficiency (3- to 8-fold) and activity (75- to 230-fold) for the conversion of 1 a and 1 b. Additional π-π interactions introduced by mutation A330F improved not only productivity and coupling efficiency, but also selectivity toward aromatic hydroxylation of 1 a (61 to 75 %). Under continuous nicotinamide adenine dinucleotide phosphate recycling, the novel P450 BM3 variant M3 was able to produce the key tocopherol precursor trimethylhydroquinone (3 a; 35 % selectivity; 0.18 mg mL^-1 ) directly from 1 a. In the case of 1 b, overoxidation leads to dearomatization and the formation of a valuable p-quinol synthon that can directly serve as an educt for the synthesis of 3 a. Detailed product pattern analysis, substrate docking, and mechanistic considerations support the hypothesis that 1 a binds in an inverted orientation in the active site of P450 BM3 WT, relative to P450 BM3 variant M3, to allow this change in chemoselectivity. This study provides an enzymatic route to key phenolic synthons for α-tocopherols and the first catalytic and mechanistic insights into direct aromatic hydroxylation and dearomatization of trimethylbenzenes with O₂ .

Directed evolution of P450cin for mediated electron transfer

Directed evolution is a powerful method to optimize enzyme properties for application demands. Interesting targets are P450 monooxygenases which catalyze the stereo- and regiospecific hydroxylation of chemically inert C-H bonds. Synthesis employing P450s under cell-free reaction conditions is limited by low total turnover numbers, enzyme instability, low product yields and the requirement of the expensive co-factor NADPH. Bioelectrocatalysis is an alternative to replace NADPH in cell-free P450-catalyzed reactions. However, natural enzymes are often not suitable for using non-natural electron delivery systems. Here we report the directed evolution of a previously engineered P450 CinA-10aa-CinC fusion protein (named P450cin-ADD-CinC) to use zinc/cobalt(III)sepulchrate as electron delivery system for an increased hydroxylation activity of 1,8-cineole. Two rounds of Sequence Saturation Mutagenesis (SeSaM) each followed by one round of multiple site-saturation mutagenesis of the P450 CinA-10aa-CinC fusion protein generated a variant (Gln385His, Val386Ser, Thr77Asn, Leu88Arg; named KB8) with a 3.8-fold increase in catalytic efficiency (28 µM^-1 min^-1) compared to P450cin-ADD-CinC (7 µM^-1 min^-1). Furthermore, variant KB8 exhibited a 1.5-fold higher product formation (500 µM µM^-1 P450) compared to the equimolar mixture of CinA, CinC and Fpr using NADPH as co-factor (315 µM µM^-1 P450). In addition, electrochemical experiments with the electron delivery system platinum/cobalt(III)sepulchrate showed that the KB8 variant had a 4-fold higher product formation rate (0.16 nmol (nmol) P450^-1 min^-1 cm^-2) than the P450cin-ADD-CinC (0.04 nmol (nmol) P450^-1 min^-1 cm^-2). In summary, the current work shows prospects of using directed evolution to generate P450 enzymes suitable for use with alternative electron delivery systems.

Screening through the PLICable promoter toolbox enhances protein production in Escherichia coli

Escherichia coli is a common host for recombinant protein production in which production titers are highly dependent on the employed expression system. Promoters are thereby a key element to control gene expression levels. In this study, a novel PLICable promoter toolbox was developed which enables in a single cloning step and after a screening experiment to identify out of ten IPTG-inducible promoters (T7, A3, lpp, tac, pac, Sp6, lac, npr, trc and syn) the most suitable one for high level protein production. The target gene is cloned under the control of different promoters in a single and efficient cloning step using the ligase-free cloning method PLICing (phosphorothioate-based ligase-independent gene cloning). The promoter toolbox was firstly validated using three well producible proteins (a cellulase from a metagenome library, a phytase from Yersinia mollaretii and an alcohol dehydrogenase from Pseudomonas putida) and then applied to two enzymes (3D1 DNA polymerase and glutamate dehydrogenase mutant) which are poorly produced in E. coli. By applying our PLICable pET-promoter toolbox, the authors were able to increase production by two-fold for 3D1 DNA polymerase (lac promoter) and 29-fold for glutamate dehydrogenase mutant H52Y (trc promoter).

What's My Substrate? Computational Function Assignment of Candida parapsilosis ADH5 by Genome Database Search, Virtual Screening, and QM/MM Calculations

Zinc-dependent medium chain reductase from Candida parapsilosis can be used in the reduction of carbonyl compounds to pharmacologically important chiral secondary alcohols. To date, the nomenclature of cpADH5 is differing (CPCR2/RCR/SADH) in the literature, and its natural substrate is not known. In this study, we utilized a substrate docking based virtual screening method combined with KEGG, MetaCyc pathway, and Candida genome databases search for the discovery of natural substrates of cpADH5. The virtual screening of 7834 carbonyl compounds from the ZINC database provided 94 aldehydes or methyl/ethyl ketones as putative carbonyl substrates. Out of which, 52 carbonyl substrates of cpADH5 with catalytically active docking pose were identified by employing mechanism based substrate docking protocol. Comparison of the virtual screening results with KEGG, MetaCyc database search, and Candida genome pathway analysis suggest that cpADH5 might be involved in the Ehrlich pathway (reduction of fusel aldehydes in leucine, isoleucine, and valine degradation). Our QM/MM calculations and experimental activity measurements affirmed that butyraldehyde substrates are the potential natural substrates of cpADH5, suggesting a carbonyl reductase role for this enzyme in butyraldehyde reduction in aliphatic amino acid degradation pathways. Phylogenetic tree analysis of known ADHs from Candida albicans shows that cpADH5 is close to caADH5. We therefore propose, according to the experimental substrate identification and sequence similarity, the common name butyraldehyde dehydrogenase cpADH5 for Candida parapsilosis CPCR2/RCR/SADH.

A high-throughput screening method to reengineer DNA polymerases for random mutagenesis

A screening system for directed evolution of DNA polymerases employing a fluorescent Scorpion probe as a reporter has been developed. The screening system has been validated in a directed evolution experiment of a distributive polymerase from the Y-polymerase family (Dpo4 from Sulfolobus solfataricus) which was improved in elongation efficiency of consecutive mismatches. The engineering campaign yielded improved Dpo4 polymerase variants one of which was successfully benchmarked in a sequence saturation mutagenesis experiment especially with regard to the desirable consecutive transversion mutations ([2.5-fold increase in frequency relative to a reference library prepared with Dpo4 WT). The Scorpion probe screening system enables to reengineer polymerases with low processivity and fidelity, and no secondary activities (i.e. exonuclease activity or strand displacement activity) to match demands in diversity generation for directed protein evolution.

P-LinK: A method for generating multicomponent cytochrome P450 fusions with variable linker length

Fusion protein construction is a widely employed biochemical technique, especially when it comes to multi-component enzymes such as cytochrome P450s. Here we describe a novel method for generating fusion proteins with variable linker lengths, protein fusion with variable linker insertion (P-LinK), which was validated by fusing P450cin monooxygenase (CinA) to the flavodoxin shuttle protein (CinC). CinC was fused to the C terminus of CinA through a series of 16 amino acid linkers of different lengths in a single experiment employing 3 PCR amplifications. Screening for 2-β-hydroxy-1,8-cineole production by CinA-CinC fusion proteins revealed that enzymatically active variants possessed linker lengths of more than 5 amino acids, reaching optimum enzyme activity at a linker length of 10 amino acids. Our P-LinK method not only minimizes experimental effort and significantly reduces time demands but also requires only a single cloning and transformation step in order to generate multiple linker variants (1 to 16 amino acids long), making the approach technically simple and robust.

The Sequence Saturation Mutagenesis (SeSaM) method

Sequence Saturation Mutagenesis (SeSaM) is a random mutagenesis method developed to overcome the limitations of existing error-prone PCR (epPCR) protocols. SeSaM is advantageous with respect to (1) elimination of mutagenic "hot spots", (2) increase in frequency of subsequent nucleotide substitutions, (3) control over the mutational bias through the utilization of universal base analogs, and, consequently, (4) the prospect of generating transversion-enriched mutant libraries. These advanced features lead to chemically diverse mutant libraries on the protein level, essentially making SeSaM a complementary technology to transition biased epPCR mutagenesis methods.

Short-term effects of large-dose vitamin A supplementation on viral load and immune response in HIV-infected women

Vitamin A supplementation has been suggested for treatment and prevention of HIV infection. However, some in vitro data indicate that vitamin A may activate HIV. Randomly, 40 HIV-seropositive women of reproductive age were allocated to receive a single oral dose of 9900 micromol (300,000 IU) vitamin A or placebo. Plasma HIV-1 RNA concentration, total lymphocytes, selected lymphocyte subsets and activation markers, and in vitro lymphocyte proliferation to phytohemagglutinin (PHA) and Candida were measured before dosing and at various time points over an 8-week follow-up period. No differences were found between treatment groups in the frequency of signs or symptoms of acute vitamin A toxicity, nor were differences evident in any lymphocyte subset or activation marker at any time during follow-up. Mean and median viral load concentration at each time point and change in viral load from baseline to each follow-up point did not differ between treatment groups. No difference was measured between treatment groups in the proportion of women who responded to PHA or Candida. This study provides no evidence that high dose vitamin A supplementation of HIV-infected women is associated with significant clinical or immunologic adverse effects.

Cultural feasibility studies in preparation for clinical trials to reduce maternal-infant HIV transmission in Haiti

A cultural feasibility study is defined as one that investigates scientific as well as ethical, behavioral, and social issues in the design of clinical trials. The value of such a broadly defined assessment is illustrated through the presentation of two case studies conducted to prepare for clinical trials to reduce maternal-infant HIV transmission on Cité Soleil, Haiti. The first study addressed issues surrounding a trial of breast-feeding and exclusive bottle-feeding among HIV seropositive mothers. The second study focused on the implementation of a double-blind trial of HIV immune globulin and standard immune globulin to be administered to infants of seropositive mothers shortly after birth. Both cases used focus group interviews with mothers and in-depth interviews with key informants to investigate AIDS-related beliefs, acceptability of trial participation, risks to subjects, and community reactions and repercussions to the trial. Findings point to the difficulties posed by attempts to conduct trial involving complex research designs in socially disadvantaged populations. Recommendations highlight the need to consider the community-wide impact of a trial, and the need to undertake extensive educational preparation of participants to ensure informed consent and adherence to protocols.

Parasitic infections of the central nervous system in children. Part III: Space-occupying lesions

In the last part of this three-part review of parasitic infections of the central nervous system in children, we consider parasites which due to their size, distribution, or the nature of the host response, tend to cause focal lesions in the brain and spinal cord and therefore present as space-occupying lesions which occasionally mimic malignant tumors. As in Parts I and II, infections are grouped according to their predominant geographic area. Such infections include cysticercosis, one of the more common and important infections of the central nervous system.

Parasitic infections of the central nervous system in children. Part II: Disseminated infections

In the second segment of this three-part review of parasitic infections of the central nervous system in children, we consider parasitic infections which typically involve various tissues and organs in addition to the brain and spinal cord. Parasites capable of dissemination in immunocompetent hosts are discussed first, and, as in Part I, organisms are grouped according to their predominant geographic location. This is followed by a discussion of the unique aspects of toxoplasmosis, strongyloidiasis and infection with microsporidia in immunocompromised patients, with an emphasis on the central nervous system.

Bacillus Calmette-Guérin complications in children born to HIV-1-infected women with a review of the literature

OBJECTIVE

To compare the risk of complications following Bacillus Calmette-Guérin (BCG) vaccination among children by maternal and infant HIV-1 infection status as part of an investigation of an outbreak of BCG complications.

METHODS

A nonconcurrent cohort study of BCG complications among 125 infants born to HIV-1 seropositive and 166 infants born to HIV-1 seronegative mothers was conducted in Cité Soleil, Haiti. Infants were examined at regular intervals until 15 months of age, and complications from BCG were documented. An investigation of BCG vaccination practices was conducted.

RESULTS

Mild or moderate complications occurred among 16 of 166 (9.6%) infants born to HIV-1 seronegative mothers compared with 4 of 13 HIV-1-infected infants (30.8%, P = .04) and 10 of 75 (13.3%, P = .39) uninfected infants born to HIV-1-infected mothers. No serious complications were noted. The outbreak of complications was associated with administration of 2.0 to 2.5 times the recommended dose of BCG vaccine.

CONCLUSIONS

This and five other cohort studies indicate that there may be a small increased risk of complications following BCG vaccination among HIV-1-infected children, but the reactions are usually mild and the risk does not outweigh the benefits of BCG vaccination in populations at high risk of tuberculosis during infancy and childhood.

Breastmilk, breastfeeding, and transmission of viruses to the neonate

The benefits of breast milk have been well delineated, and breastfeeding should be encouraged whenever possible. However, the potential transmission of HIV-1, HTLV-1, and possibly HTLV-II warrant the recommendation that women in industrialized countries who are infected with these viruses not breastfeed their infants. These recommendations reflect what is currently known about the risks of viral transmission through breastfeeding; ongoing and future studies may provide additional data, enabling a better definition of the precise risks and factors associated with the transmission of viruses through breastfeeding.

HIV risk behavior and medical status of underprivileged youths in Belo Horizonte, Brazil

METHODS

From June 1989 to April 1991, 394 adolescents aged 10-18 years randomly selected upon admission at a state shelter in Belo Horizonte, Brazil underwent health history interview, physical examination, serology for HIV, hepatitis B, and syphilis, and stool examination. Participants were classified as street-based youths (n = 195) or home-based youths (n = 199). The age distribution was similar in both groups, although males were overrepresented among street-based youths (79.5% versus 62.3%).

RESULTS

Compared with home-based youths, street-based youths reported earlier onset (p = 0.009) and higher rates of sexual activity (odds ratio [OR], 2.1; 95% confidence interval [CI], 1.4-3.3), sexual abuse (OR, 3.7; 95% CI, 1.2-10.1), and sexually transmitted diseases (OR, 2.9; 95% CI, 1.3-6.6). Overall condom use was low in both groups. Street-based youths were 7.8 times more likely to use drugs than home-based youths (95% CI, 4.9-12.7). Inhalants and marijuana were the more commonly used drugs. Intravenous drug use was low.

CONCLUSIONS

Although chronic malnutrition and multiple parasitosis were common findings in both groups, street-based youths were more likely to present disorders related to trauma and poor hygienic conditions. Antibodies to HIV were detected in four (2%) street-based youths and in none of the home-based youths. This study confirms that street youths are at higher risk for HIV infection than their home-based peers and indicates a need for HIV prevention programs targeting this population.

Maternal IgG1 and IgA antibody to V3 loop consensus sequence and maternal-infant HIV-1 transmission

Maternal-infant transmission of HIV-1 occurs in 13-40% of pregnancies. Studies on transmission of maternal immunity to HIV antigens have used antigens from viruses not representative of clinical isolates and have been conflicting. Using a consensus peptide sequence based on HIV isolates found in Haiti, we found that Haitian mothers who transmitted infection to their offspring had significantly higher mean concentrations of IgG1 antibodies to the V3 loop of the primary neutralising domain of the viral envelope (gp 160) than non-transmitters (p = 0.02). Concentrations of IgA antibody to this domain were similar in transmitters and non-transmitters.

Prevalence of HIV-1 DNA and p24 antigen in breast milk and correlation with maternal factors

Breast milk specimens from human immunodeficiency virus type 1 (HIV-1)-seropositive and HIV-1-seronegative women were examined for the presence of HIV-1 p24 antigen by the antigen capture method and for viral DNA using the polymerase chain reaction. HIV-1 DNA was present in 70% of milk specimens collected from 47 HIV-seropositive women 0-4 days after delivery and in approximately 50% of specimens collected 6 and 12 months postpartum. p24 antigen, present in 24% of milk specimens collected from 37 seropositive women within the first 4 days postpartum, was not detected in any of the subsequent specimens. The presence of HIV-1 DNA or p24 antigen in milk was not significantly associated with maternal CD4 lymphocyte count, beta 2-microglobulin level, or fulfillment of the AIDS clinical case definition. Although the correlation of either HIV-1 proviral DNA or p24 antigen with the presence of infectious virus is not known, these data indicate the need for additional studies examining the role of breastfeeding in maternal-infant transmission of HIV-1.

The utility of verbal autopsies for identifying HIV-1-related deaths in Haitian children

OBJECTIVE

To determine whether deaths among Haitian infants born to HIV-1-seronegative women could be distinguished from deaths among children born to HIV-1-seropositive women using the verbal autopsy technique.

METHODS

Mothers of 315 Haitian children who died were interviewed about events leading to the child's death. Three physicians independently reviewed interview data and determined the probable cause of death without knowledge of maternal HIV-1 status or hospital records. The underlying causes of death assigned to the infants were analyzed to determine whether maternal HIV status could be predicted.

RESULTS

There was good agreement among the physicians (kappa = 0.62) and 90% agreement between hospital records and the verbal autopsy diagnosis. Compared with children born to HIV-1-seronegative women, deaths in children born to HIV-1-seropositive mothers were more likely to be ascribed to a presumptive diagnosis of AIDS (37 versus 21%; P = 0.01). The sensitivity and specificity of verbal autopsies for identifying deaths associated with maternal HIV-1 infection ranged from 37 to 59% and from 69 to 79%, respectively, depending on the classification system used. The predictive positive value of a death believed to be consistent with pediatric HIV-1 infection was 26-30% and the predictive negative value was 85-90%.

CONCLUSION

Verbal autopsies may be useful for distinguishing certain causes of death, but have limited utility for distinguishing deaths associated with maternal HIV-1 infection from deaths among children born to HIV-1-seronegative women.

Herpes simplex virus type 2 infection, syphilis, and hepatitis B virus infection in Haitian women with human immunodeficiency virus type 1 and human T lymphotropic virus type I infections. The Johns Hopkins University (JHU)/Centre pour le Developpement et la Santé (CDS) HIV Study Group

Antibodies to herpes simplex virus type 2 (HSV-2), antibodies to hepatitis B virus (HBV) core antigen (anti-HBc), and VDRL antibodies (serologic evidence of syphilis) were evaluated in women known to be infected with human immunodeficiency virus type 1 (HIV-1) (n = 95) or human T lymphotropic virus type I (HTLV-I) (n = 45) and controls (n = 89). HIV-1-seropositive women were more likely than controls to have antibodies to HSV-2 (88% vs. 54%; P less than .001), anti-HBc (67% vs. 43%; P = .008), and VDRL antibodies (21% vs. 8%; P = .02). Similarly, HTLV-I-seropositive women were more likely than controls to have antibodies to HSV-2 (82% vs. 54%; P = .003) and anti-HBc (67% vs. 43%; P = .008). There was no evidence that HIV-1 or HTLV-I predisposed to chronic hepatitis B virus infection. The stronger associations between HIV-1 and HTLV-I with HSV-2 than the associations with syphilis or HBV are consistent with the hypothesis that recurrent disruptions of mucous membranes caused by HSV-2 infections predispose to sexual transmission of HIV-1 and HTLV-I.

Tuberculin skin test reactivity among adults infected with human immunodeficiency virus

Infection with the human immunodeficiency virus type 1 (HIV-1) results in decreased cell-mediated immunity, which includes decreased delayed hypersensitivity to skin test antigens. HIV-1 seropositivity and skin test reactivity to purified protein derivative (PPD) were determined among 2042 healthy Haitian adults with normal chest radiographs. Among HIV-1-seropositive individuals, 52.3% (146/279) had PPD reactions greater than or equal to 10 mm compared with 67.2% (1184/1763) of the seronegative adults (P less than .001). However, the percentage of HIV-1-seropositive individuals with PPD reactions greater than or equal to 5 mm was similar to the percentage of seronegative adults with PPD reactions greater than or equal to 10 mm (180/279 [64.5%] vs. 1184/1763 [67.2%]). Assuming that the rate of prior infection with Mycobacterium tuberculosis was similar for HIV-1-seronegative and -seropositive populations, these data provide support for the recent recommendations to use induration of greater than or equal to 5 mm as evidence of past infection with M. tuberculosis in HIV-1 seropositive adults.

Failure of the H2 antagonist cimetidine to reverse parasite antigen-specific lymphocyte unresponsiveness in experimental filariasis

Histamine is known to mediate potent immunosuppressive effects on lymphocyte function. In jirds infected with Brugia pahangi decreased mitogen and parasite antigen responsiveness are associated with the presence of histamine binding regulatory cells. The present study was thus designed to investigate the immunoregulatory role of histamine in experimental filariasis. Spleen cells from normal or B. pahangi infected jirds were incubated with BSA or histamine coupled Sepharose beads and the degree of cell-bead binding was quantitated. Cells from infected jirds demonstrated increased levels of histamine, but not BSA binding relative to normal cells, and this binding was blocked by soluble histamine or by the histamine receptor antagonist cimetidine. Cimetidine failed to restore the in vitro responsiveness of spleen cells from infected jirds to phytohemagglutinin or to a soluble extract of B. pahangi. Cimetidine did, however, reverse histamine-induced suppression of normal spleen cell responses to PHA. The present results suggest that histamine does not play a major role in the immunoregulatory alterations induced by B. pahangi infection.

Bancroftian filariasis in Haiti: preliminary characterization of the immunological responsiveness of microfilaremic individuals

Patent infections with the lymphatic filariae, Wuchereria bancrofti and Brugia malayi, are associated with suppressed in vitro cellular responsiveness to filarial antigens. In studies of bancroftian filariasis in Haiti, a significant number of microfilaremic individuals can be characterized as "responders" to filarial antigens. Cells from 37/74 untreated microfilaremic subjects responded to B. pahangi antigen (stimulation ratio greater than 2) as detected by in vitro blastogenesis. A comparison of responders to nonresponders revealed a significant difference in mean B. pahangi reactivity (15,822 vs. 4,538 cpm, P less than 0.001), but no significant differences with respect to age, microfilaremia, PPD or PHA reactivity, or B. pahangi-specific antibody levels. Subtle differences may exist between these groups with respect to recognition of specific antigens on Western blots.