The role of milk-derived antimicrobial lipids as antiviral and antibacterial agents

Alahmari A, A. Alqabbani A, Aldayel AM. Exploring the landscape of Lipid Nanoparticles (LNPs): A comprehensive review of LNPs types and biological sources of lipids

Lipid nanoparticles (LNPs) have emerged as promising carriers for delivering therapeutic agents, including mRNA-based immunotherapies, in various biomedical applications. The use of LNPs allows for efficient delivery of drugs, resulting in enhanced targeted delivery to specific tissues or cells. These LNPs can be categorized into several types, including liposomes, solid lipid nanoparticles, nanostructured lipid carriers, and lipid-polymer hybrid nanoparticles. The preparation of LNPs involves the manipulation of their structural, dimensional, compositional, and physical characteristics via the use of different methods in the industry. Lipids used to construct LNPs can also be derived from various biological sources, such as natural lipids extracted from plants, animals, or microorganisms. This review dives into the different types of LNPs and their preparation methods. More importantly, it discusses all possible biological sources that are known to supply lipids for the creation of LNPs. Natural lipid reservoirs have surfaced as promising sources for generating LNPs. The use of LNPs in drug delivery is expected to increase significantly in the coming years. Herein, we suggest some environmentally friendly and biocompatible sources that can produce lipids for future LNPs production.

Fatty acid composition profiling in the dorsal skin of Sunda porcupine (Hystrix javanica)

The fatty acid composition in the skin of Sunda porcupine (Hystrix javanica) is an interesting topic due to the special features of quills, especially in the dorsal region. Therefore, this study aims to analyze the composition of fatty acids in the dorsal region of Sunda porcupine skin. It was conducted using skin samples of the thoracodorsal and lumbosacral regions taken by biopsies and from frozen specimens. The skin lipid was extracted and then derivatized into fatty acid methyl ester before analyzing with gas chromatography mass spectrometry. The results showed that the skin is composed of up to 25 fatty acids ranging from C12 to C25 with various types but only 16 were found in both regions and sexes. Fatty acids with an antibacterial effect were found abundantly, such as oleic, palmitic, stearic, and linoleic acids. The total abundance in the thoracodorsal region was higher than lumbosacral, while the composition in male was higher than in female. Based on the results, the fatty acid composition in the dorsal skin region of Sunda porcupine consists of at least 16 types ranging from C12-C25. Additionally, the region and sex were observed to contribute significantly to the variation in skin fatty acid composition.

The Effects of Thermal Pasteurisation, Freeze-Drying, and Gamma-Irradiation on the Antibacterial Properties of Donor Human Milk

The most common pasteurisation method used by human milk banks is Holder pasteurisation. This involves thermal processing, which can denature important proteins and can potentially reduce the natural antimicrobial properties found in human milk. This study assesses the application of a hybrid method comprised of freeze-drying followed by low-dose gamma-irradiation for nonthermal donor human milk pasteurisation. Freeze-drying donor human milk followed by gamma-irradiation at 2 kGy was as efficient as Holder pasteurisation in the reduction of bacterial inoculants of Staphylococcus aureus (10⁶ cfu/mL) and Salmonella typhimurium (10⁶ cfu/mL) in growth inhibition assays. These assays also demonstrated that human milk naturally inhibits the growth of bacterial inoculants S. aureus, S. typhimurium, and Escherichia coli. Freeze drying (without gamma-irradiation) did not significantly reduce this natural growth inhibition. By contrast, Holder pasteurisation significantly reduced the milk’s natural antimicrobial effect on S. aureus growth after 6 h (−19.8% p = 0.01). Freeze-dried and then gamma-irradiated donor human milk showed a strong antimicrobial effect across a dose range of 2–50 kGy, with only a minimal growth of S. aureus observed after 6 h incubation. Thus, a hybrid method of freeze-drying followed by 2 kGy of gamma-irradiation preserves antimicrobial properties and enables bulk pasteurisation within sealed packaging of powderised donor human milk. This work forwards a goal of increasing shelf life and simplifying storage and transportation, while also preserving functionality and antimicrobial properties.

Microbial lipases and their industrial applications: a comprehensive review

Lipases are very versatile enzymes, and produced the attention of the several industrial processes. Lipase can be achieved from several sources, animal, vegetable, and microbiological. The uses of microbial lipase market is estimated to be USD 425.0 Million in 2018 and it is projected to reach USD 590.2 Million by 2023, growing at a CAGR of 6.8% from 2018. Microbial lipases (EC 3.1.1.3) catalyze the hydrolysis of long chain triglycerides. The microbial origins of lipase enzymes are logically dynamic and proficient also have an extensive range of industrial uses with the manufacturing of altered molecules. The unique lipase (triacylglycerol acyl hydrolase) enzymes catalyzed the hydrolysis, esterification and alcoholysis reactions. Immobilization has made the use of microbial lipases accomplish its best performance and hence suitable for several reactions and need to enhance aroma to the immobilization processes. Immobilized enzymes depend on the immobilization technique and the carrier type. The choice of the carrier concerns usually the biocompatibility, chemical and thermal stability, and insolubility under reaction conditions, capability of easy rejuvenation and reusability, as well as cost proficiency. Bacillus spp., Achromobacter spp., Alcaligenes spp., Arthrobacter spp., Pseudomonos spp., of bacteria and Penicillium spp., Fusarium spp., Aspergillus spp., of fungi are screened large scale for lipase production. Lipases as multipurpose biological catalyst has given a favorable vision in meeting the needs for several industries such as biodiesel, foods and drinks, leather, textile, detergents, pharmaceuticals and medicals. This review represents a discussion on microbial sources of lipases, immobilization methods increased productivity at market profitability and reduce logistical liability on the environment and user.

Antimicrobial Activity of Host-Derived Lipids

Host-derived lipids are increasingly recognized as antimicrobial molecules that function in innate immune activities along with antimicrobial peptides. Sphingoid bases and fatty acids found on the skin, in saliva and other body fluids, and on all mucosal surfaces, including oral mucosa, exhibit antimicrobial activity against a variety of Gram positive and Gram negative bacteria, viruses, and fungi, and reduce inflammation in animal models. Multiple studies demonstrate that the antimicrobial activity of lipids is both specific and selective. There are indications that the site of action of antimicrobial fatty acids is the bacterial membrane, while the long-chain bases may inhibit cell wall synthesis as well as interacting with bacterial membranes. Research in this area, although still sporadic, has slowly increased in the last few decades; however, we still have much to learn about antimicrobial lipid mechanisms of activity and their potential use in novel drugs or topical treatments. One important potential benefit for the use of innate antimicrobial lipids (AMLs) as antimicrobial agents is the decreased likelihood side effects with treatment. Multiple studies report that endogenous AML treatments do not induce damage to cells or tissues, often decrease inflammation, and are active against biofilms. The present review summarizes the history of antimicrobial lipids from the skin surface, including both fatty acids and sphingoid bases, in multiple human body systems and summarizes their relative activity against various microorganisms. The range of antibacterial activities of lipids present at the skin surface and in saliva is presented. Some observations relevant to mechanisms of actions are discussed, but are largely still unknown. Multiple recent studies examine the therapeutic and prophylactic uses of AMLs. Although these lipids have been repeatedly demonstrated to act as innate effector molecules, they are not yet widely accepted as such. These compiled data further support fatty acid and sphingoid base inclusion as innate effector molecules.

Antimicrobial lipids in nano-carriers for antibacterial delivery

Antimicrobial lipids have been recognised as broad-spectrum antibacterial agents. They can directly act on and lyse bacterial cell membrane, and inhibit bacterial growth through a range of mechanisms. Antimicrobial lipids include free fatty acids, monoglycerides, cholesteryl ester, sphingolipids and etc., with the first two being the most extensively studied. Their application is usually hindered by the low solubility of the compounds themselves, and nano-sized lipid-based carriers can endow druggability to these antimicrobial agents for they improve lipid solubility and dispersion in aqueous formulations. Nano-carriers also possess advantages in overcoming drug resistance. In this review we will discuss different kinds of antimicrobial lipids in nano-sized carriers for antibacterial delivery. CAL02 as a promising infection-controlling liposome consisted of cholesterol and sphingomyelin will also be included for it's a unique anti-infection approach, which signifies that the underlying antibacterial roles antimicrobial lipids needs to be further addressed. With the global emergence of antibiotic resistance, antimicrobial lipids formulated in nano-carriers might provide a novel alternative in combatting infectious diseases.

Carrier oils in dermatology

Wounds are a common medical infliction. With the increase in microbial resistance and a shift of interest towards complementary medicines, essential oils have been shown to be beneficial in suppressing microbial growth. However, in practice, essential oils are more often diluted into a base due to the risk of topical adverse effects, such as dermatitis. There is a lack of collated evidence-based information on toxicity and efficacy of carrier oils. The current information on the subject matter is restricted to generic, aroma-therapeutic books and pamphlets, based on anecdotal evidence rather than an experimental approach. Therefore, this review aimed at identifying the recommended carrier oils used in dermatology and thereafter collating the scientific evidence to support the use of carrier oils together with essential oils recommended for dermatological use. Aloe vera gel had multiple studies demonstrating the ability to enhance wound healing; however, several other carrier oils have been largely neglected. It was observed that the extracts for certain plant species had been used to justify the use of the carrier oils of the same plant species. This is an inaccurate cross assumption due to the difference in chemical composition and biological activities. Lastly, despite these carrier oils being recommended as a base for essential oils, very little data was found on the interactive profile of the carrier oil with the essential oil. This review provides a platform for further studies, especially if essential oils are to receive credence in the scientific field.

The dorsal skin structure contributes to the surface bacteria populations of Sunda Porcupine (Hystrix javanica)

Skin becomes the largest organ in the body and protects its own inner layer. The structure and chemical composition of the skin contribute to skin condition and affect the habitat of certain bacteria. The Sunda Porcupine is one of endemic animals of Indonesia which possesses quill as the main derivate of its skin and as a defence tool against predators. The present study used nine adults (five females and four males) of Sunda Porcupine and aimed to observe the correlation of skin structure with bacterial population at the surface level. The skin was wavy due to the protrusion of quill follicle orifices on the skin surface and formed clusters. The skin of Sunda Porcupine was also wrinkled and had a lot of flakiness. Histologically, the skin was composed of epidermis, dermis, hypodermis and subcutaneous muscle. The quill follicles and their properties were the dominant structure component of the skin. No sweat gland was observed in the skin of the Sunda Porcupine, and sebaceous gland was found only around quill and hair follicles. The bacterias identified in the skin were Staphylococcus aureus, S. epidermidis, Micrococcus sp. and Salmonella sp. When compared, the bacterial population was higher in the lumbosacral region than in the thoracodorsal region, but the difference was not significant. The density of quill clusters was negatively correlated to the bacterial population. It was suggested the structure of the skin has contribution to bacterial population in dorsal trunk of the Sunda Porcupine.

Application of nanotechnology for the development of microbicides

The vaginal route is increasingly being considered for both local and systemic delivery of drugs, especially those unsuitable for oral administration. One of the opportunities offered by this route but yet to be fully utilised is the administration of microbicides. Microbicides have an unprecedented potential for mitigating the global burden from HIV infection as heterosexual contact accounts for most of the new infections occurring in sub-Saharan Africa, the region with the highest prevalent rates. Decades of efforts and massive investment of resources into developing an ideal microbicide have resulted in disappointing outcomes, as attested by several clinical trials assessing the suitability of those formulated so far. The highly complex and multi-level biochemical interactions that must occur among the virus, host cells and the drug for transmission to be halted means that a less sophisticated approach to formulating a microbicide e.g. conventional gels, etc may have to give way for a different formulation approach. Nanotechnology has been identified to offer prospects for fabricating structures with high capability of disrupting HIV transmission. In this review, predominant challenges seen in microbicide development have been highlighted and possible ways of surmounting them suggested. Furthermore, formulations utilising some of these highly promising nanostructures such as liposomes, nanofibres and nanoparticles have been discussed. A perspective on how a tripartite collaboration among governments and their agencies, the pharmaceutical industry and academic scientists to facilitate the development of an ideal microbicide in a timely manner has also been briefly deliberated.

The role of dietary nucleotides in single-stomached animals

The transition from liquid to solid feed during weaning results in morphological, histological and microbial changes in the young animal's intestinal tract and often is associated with diarrhoea. The ban of in-feed antibiotics in pig production in the European Union has led to increasing interest in alternatives to overcome weaning-associated problems. Among others, nucleotides may have the potential to alleviate health impairments due to weaning. Nucleotides are natural components of the non-protein fraction of milk and have important effects on the maintenance of health in young animals. Nucleotides and their related metabolic products play key roles in many biological processes and become essential dietary components when endogenous supply is insufficient for normal function. The present review summarises nucleotide composition of milk from different species, the biology of nucleotides and possible effects of dietary nucleotides on intestinal morphology and function, intestinal microbiota, immune function, nutrient metabolism, hepatic morphology and function as well as growth performance. Special attention is given to data available for pigs, and suggestions are made for inclusion of nucleotides in the diet to benefit piglets' health and reduce the consequences accompanying early weaning.

Effects of Essential Oils and Monolaurin on Staphylococcus aureus: In Vitro and In Vivo Studies

The antimicrobial properties of volatile aromatic oils and medium-chain fatty acids derived from edible plants have been recognized since antiquity. To give examples, Origanum oil, used as a food-flavoring agent, possesses a broad spectrum of antimicrobial activity due, at least in part, to its high content of phenolic derivatives such as carvacrol and thymol. Similarly, lauric acid, present in heavy concentrations in coconuts, forms monolaurin in the body that can inhibit the growth of pathogenic microbes. Using Staphylococcus aureus in broth cultures and a microdilution method, comparative efficacy of Origanum oil, and a constituent carvacrol, other essential oils and monolaurin were examined. Origanum oil was the most potent of the essential oils tested and proved bactericidal in culture to two strains of Staphylococcus aureus (ATCC #14154 and #14775) at 0.25 mg/mL. In vitro, monolaurin's effects mirrored Origanum oil. The combination of both was bactericidal at the 0.125 mg/mL concentration of each. In two separate In vivo experiments, injected Staphylococcus aureus (ATCC #14775) killed all 14 untreated mice within a 1-week period. In treated mice, over one third survived for 30 days when given oral Origanum oil daily for 30 days (6/14). Fifty percent of the mice survived for 30 days when receiving daily vancomycin (7/14) and monolaurin (4/8). Over 60% of mice survived when receiving a daily combination of Origanum oil and monolaurin (5/8). Origanum oil and/or monolaurin may prove to be useful antimicrobial agents for prevention and therapy of Staphylococcus aureus infections.

Development of a liposome microbicide formulation for vaginal delivery of octylglycerol for HIV prevention

The feasibility of using a liposome drug delivery system to formulate octylglycerol (OG) as a vaginal microbicide product was explored. A liposome formulation was developed containing 1% OG and phosphatidyl choline in a ratio that demonstrated in vitro activity against Neisseria gonorrhoeae, HSV-1, HSV-2 and HIV-1 while sparing the innate vaginal flora, Lactobacillus. Two conventional gel formulations were prepared for comparison. The OG liposome formulation with the appropriate OG/lipid ratio and dosing level had greater efficacy than either conventional gel formulation and maintained this efficacy for at least 2 months. No toxicity was observed for the liposome formulation in ex vivo testing in a human ectocervical tissue model or in vivo testing in the macaque safety model. Furthermore, minimal toxicity was observed to lactobacilli in vitro or in vivo safety testing. The OG liposome formulation offers a promising microbicide product with efficacy against HSV, HIV and N. gonorrhoeae.

The macronutrients in human milk change after storage in various containers

BACKGROUND

The concentrations of macronutrients in human milk can be influenced by various processes, such as storage, freezing, and thawing, that are performed by lactating working mothers and breast milk banks. We evaluated the impact of various containers on the nutrient concentrations in human milk.

METHODS

A total of 42 breast milk samples from 18 healthy lactating mothers were collected. A baseline macronutrient concentration was determined for each sample. Then, the breast milk samples were divided and stored in nine different commercial milk containers. After freezing at -20°C for 2 days, the milk samples were thawed and analyzed again. A midinfrared human milk analyzer (HMA) was used to measure the protein, fat, and carbohydrate contents.

RESULTS

There was a significant decrease in the fat content following the storage, freezing, and thawing processes, ranging from 0.27-0.30 g/dL (p=0.02), but no significant decrease in energy content (p=0.069) was noted in the nine different containers. There were statistically significant increases in protein and carbohydrate concentrations in all containers (p=0.021 and 0.001, respectively), however there were no significant differences between the containers in terms of fat, protein, carbohydrate, or energy contents.

CONCLUSION

Human milk, when subjected to storage, freezing, and thawing processes, demonstrated a significant decrease in fat content (up to 9% reduction) in various containers. It is better for infants to receive milk directly from the mother via breastfeeding. More studies are warranted to evaluate the effects of milk storage on infant growth and development.

Long-term health outcomes and mechanisms associated with breastfeeding

Breastfeeding is superior to formula feeding because it has factors that have long term consequences for early metabolism and disease later in life. In this paper, the scientific evidence in support of why breast milk is beneficial for infants is summarized and the mechanisms in which breastfeeding impacts on disease are explored. Human milk may show a reduced occurrence of disease because mammalian evolution promotes survival, and because of specific factors in milk that promote active stimulation of the infant's immune system and gastrointestinal mucosal maturation decrease the incidence of infection and alter the gut microflora. Bioactive factors, including: hormones, growth factors, colony-stimulating factors and specific nutrients, may have such far-reaching effects on the infant's immune response that normal development depends heavily on its provision. All mothers should be encouraged and supported to continue breastfeeding for 6 months and beyond in order to promote the good health of their infants.

Evaluation of WLBU2 peptide and 3-O-octyl-sn-glycerol lipid as active ingredients for a topical microbicide formulation targeting Chlamydia trachomatis

Topical microbicides for prevention of sexually transmitted diseases (STDs) would be especially useful for women who are not able to persuade their partner(s) to take precautions. Many topical microbicides are in various stages of development, based on a variety of active ingredients. We investigated the in vitro activity of an engineered antimicrobial peptide (WLBU2) and a lipid (3-O-octyl-sn-glycerol [3-OG]) which could potentially be used as active ingredients in such a product. Using commercially available cytotoxicity reagents [Alamar Blue, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT), and lactate dehydrogenase (LDH)], we first determined the toxicity of WLBU2 and 3-OG to the host cells in our assay procedure and excluded toxic concentrations from further testing. To determine activity against Chlamydia trachomatis, we used an assay previously developed by our laboratory in which chlamydial elementary bodies (EBs) were exposed to microbicides prior to contact with epithelial cells: the minimum (microbi)cidal concentration (MCC) assay. To further simulate conditions of transmission, we carried out the same assay in the presence of a simulated vaginal fluid, a simulated seminal fluid, human serum albumin, and a range of pH values which might be found in the human vagina at the time of exposure. Last, we tested WLBU2 and 3-OG in combination to determine if adding them together resulted in synergistic activity. We found that WLBU2 and 3-OG both have excellent activity in vitro against C. trachomatis and significantly more activity when added together. The simulated fluids reduced activity, but the synergy seen is good evidence that they would be effective when combined in a microbicide formulation.

Influence of dietary components on development of the microbiota in single-stomached species

After birth, development of a normal microbial community occurs gradually, and is affected by factors such as the composition of the maternal gut microbiota, the environment, and the host genome. Diet also has a direct influence, both on composition and activity of this community. This influence begins with the milk, when specific components exert their growth-promoting effect on a beneficial microbiota, thereby suppressing potential pathogens. For example, breast-fed infants compared with formula-fed babies usually have a microbial community dominated by bifidobacteria. When solid food is introduced (weaning), dramatic changes in microbial composition occur, so pathogens can gain access to the disturbed gastrointestinal (GI) ecosystem. However, use of specific dietary components can alter the composition and activity of the microbiota positively. Of all dietary components, fermentable carbohydrates seem to be most promising in terms of promoting proliferation of beneficial bacterial species. Carbohydrate fermentation results in the production of SCFA which are known for their trophic and health-promoting effects. Fermentation of proteins, on the other hand, is often associated with growth of potential pathogens, and results in production of detrimental substances including NH3and amines. In terms of the GI microbiota, lipids are often associated with the antimicrobial activity of medium-chain fatty acids and their derivatives. The present review aims to provide deeper insights into the composition and development of the neonatal GI microbiota, how this microbiota can be influenced by certain dietary components, and how this might ultimately lead to improvements in host health.

The role of microbicidal lipids in host defense against pathogens and their potential as therapeutic agents

Lipids such as fatty alcohols, free fatty acids and monoglycerides of fatty acids are known to be potent antimicrobial/microbicidal agents in vitro and to kill enveloped viruses, Gram-positive and Gram-negative bacteria and fungi on contact. For over half a century several studies have tried to answer the question of whether or not lipids play a role in the natural host defense against pathogens. A comprehensive review is given of these studies, particularly concerning infections in skin and in mucosal membranes of the respiratory tract, and of the role of lipids in the antimicrobial activity of breast milk. Based on studies of the microbicidal activities of lipids, both in vitro and in vivo, the possibility of using such lipids as active ingredients in prophylactic and therapeutic dosage forms is considered and examples are given of studies of such pharmaceutical dosage forms in experimental animal models and in clinical trials.

Identifying the components in eggshell membrane responsible for reducing the heat resistance of bacterial pathogens

The biological activity (D-value determination) of eggshell membrane (ESM) was examined to determine the membrane components and mechanisms responsible for antibacterial activity. Biological and enzymatic activities (i.e., beta-N-acetylglucosaminidase [beta-NAGase], lysozyme, and ovotransferrin) of ESM denatured with trypsin, lipases, or heat were compared with those of untreated ESM. Trypsin-treated ESM lost all biological activity (D-values at 54 degrees C were 5.12 and 5.38 min for immobilized and solubilized trypsin, respectively) but showed no significant loss of enzymatic activities. Treatments with porcine lipase and a lipase cocktail did not impact biological or enzymatic activities. Heat denaturation of ESM (at 80 and 100 degrees C for 15 min) resulted in significant decreases in biological activity (D-values of 3.99 and 4.43 min, respectively) and loss of beta-NAGase activity. Lysozyme and ovotransferrin activities remained but were significantly reduced. Purified ESM and hen egg white components (i.e., beta-NAGase, lysozyme, and ovotransferrin) were added to Salmonella Typhimurium suspensions (in 0.1% peptone water) at varying concentrations to evaluate their biological activity. D-values at 54 degrees C were 4.50 and 3.68 min for treatment with lysozyme or beta-NAGase alone, respectively, and 2.44 min for ovotransferrin but 1.47 min for a combination of all three components (similar to values for ESM). Exposure of Salmonella Typhimurium cells to a mixture of ovotransferrin, lysozyme, and beta-NAGase or ESM resulted in significant increases in extracellular concentrations of Ca2+, Mg2+, and K+. Transmission electron microscopic examination of Salmonella Typhimurium cells treated with a combination of ovotransferrin, lysozyme, and beta-NAGase revealed membrane disruption and cell lysis. The findings of this study demonstrate that ovotransferrin, lysozyme, and beta-NAGase are the primary components responsible for ESM antibacterial activity. The combination of these proteins and perhaps other ESM components interferes with interactions between bacterial lipopolysaccharides, sensitizing the outer bacterial membrane to the lethal affects of heat and possibly pressure and osmotic stressors.

Alternative modified infant-feeding practices to prevent postnatal transmission of human immunodeficiency virus type 1 through breast milk: past, present, and future

Preventing mother-to-child transmission (MTCT) of human immunodeficiency virus type 1 (HIV-1) through breastfeeding is important to reduce the number of infected children. Research on making breastfeeding safer is a high priority. The authors reviewed the attempts to develop alternative methods, other than antiretroviral (ARV) therapy of mothers and/or babies, to decontaminate breast milk of infectious HIV-1 (free and associated with lymphocytes). They also review how these methods affect milk constituents, as well as their current and prospective status. A PubMed search for English publications on methods to prevent MTCT through breast milk was completed. Methods that have been tested, other than systemicuse or ARV or immunoprophylaxis, to reduce or prevent MTCT of HIV-1 through breast milk were broadly classified into 5 groups: (1) modified feeding practices, (2) heat treatment of milk, (3) lipolysis, (4) antimicrobial treatment of the breastfeeding mother, and (5) microbicidal treatment of infected milk. Their advantages and disadvantages are discussed, as well as future directions in the prevention of MTCT through breastfeeding.

Virucidal effect of lipids on visna virus, a lentivirus related to HIV

Natural lipids and fatty alcohols show virucidal activities against enveloped viruses. A virucidal profile of these compounds against visna virus (VV), a lentivirus related to HIV, or against other viruses of the genus Lentivirus has not been established before and could help elucidate how lipids inactivate enveloped viruses and assist in the development of virucidal drugs. The activity profile for VV may not exactly reflect the profile for HIV or for the lentivirus subgroup in general, but the results for VV are in agreement with earlier studies, which have shown that lipids become generally more virucidal at low pH.

Vernix caseosa as a multi-component defence system based on polypeptides, lipids and their interactions

Vernix caseosa is a white cream-like substance that covers the skin of the foetus and the newborn baby. Recently, we discovered antimicrobial peptides/proteins such as LL-37 in vernix, suggesting host defence functions of vernix. In a proteomic approach, we have continued to characterize proteins in vernix and have identified 20 proteins, plus additional variant forms. The novel proteins identified, considered to be involved in host defence, are cystatin A, UGRP-1, and calgranulin A, B and C. These proteins add protective functions to vernix such as antifungal activity, opsonizing capacity, protease inhibition and parasite inactivation. The composition of the lipids in vernix has also been characterized and among these compounds the free fatty acids were found to exhibit antimicrobial activity. Interestingly, the vernix lipids enhance the antimicrobial activity of LL-37 in vitro, indicating interactions between lipids and antimicrobial peptides in vernix. In conclusion, vernix is a balanced cream of compounds involved in host defence, protecting the foetus and newborn against infection.

The effects of saturated fatty acids on Giardia duodenalis trophozoites in vitro

Giardia duodenalis is a protozoal, intestinal parasite that is a common aetiological agent of infectious diarrhoea in humans worldwide. Chemotherapeutic intervention presently offers a limited range of drugs and these are usually only employed after clinical diagnosis. Moreover, these drugs are ineffective against the infectious cysts, can produce unpleasant side effects, and are expensive with limited availability in developing countries. Frequent reports of drug toxicity, treatment failure and parasite drug resistance have, in some instances, also resulted in the increasing reluctance to over-prescribe synthetic anti-microbials. Alternatively, there is now mounting evidence to suggest that some of the naturally derived, medium-chain, saturated fatty acids (MCSFAs) possess anti-microbial and anti-parasitic properties. We have therefore examined the effects of four different fatty acids on G. duodenalis trophozoites in vitro. Cytotoxicity was determined using fluorescence, scanning and transmission electron microscopic techniques and standard cytotoxicity assays. Our studies have confirmed that the MCSFA, dodecanoic acid (C: 12) (common name: lauric acid), is anti-giardial, with an LD50 concentration comparable to that of metronidazole, the drug of choice in the treatment of giardiasis. Dodecanoic acid appeared to induce trophozoite death by accumulating within the parasite cytoplasm resulting in rupture of the cell membrane. This study has opened fresh avenues for development of natural drug therapy in which food supplementation may augment, or even replace, some of the standard chemotherapeutic agents presently employed in the treatment of giardiasis and possibly other infectious intestinal diseases.

Minimum inhibitory concentrations of herbal essential oils and monolaurin for gram-positive and gram-negative bacteria

New, safe antimicrobial agents are needed to prevent and overcome severe bacterial, viral, and fungal infections. Based on our previous experience and that of others, we postulated that herbal essential oils, such as those of origanum, and monolaurin offer such possibilities. We examined in vitro the cidal and/or static effects of oil of origanum, several other essential oils, and monolaurin on Staphylococcus aureus, Bacillus anthracis Sterne, Escherichia coli, Klebsiella pneumoniae, Helicobacter pylori, and Mycobacterium terrae. Origanum proved cidal to all tested organisms with the exception of B. anthracis Sterne in which it was static. Monolaurin was cidal to S. aureus and M. terrae but not to E. coli and K. pneumoniae. Unlike the other two gram-negative organisms, H. pylori were extremely sensitive to monolaurin. Similar to origanum, monolaurin was static to B. anthracis Sterne. Because of their longstanding safety record, origanum and/or monolaurin, alone or combined with antibiotics, might prove useful in the prevention and treatment of severe bacterial infections, especially those that are difficult to treat and/or are antibiotic resistant.

Feline immunodeficiency virus is concentrated in milk early in lactation

We studied mother-to-offspring transmission of feline immunodeficiency virus (FIV), focusing on milk-borne virus transmission in order to assess its similarities to perinatal HIV transmission. We also attempted to evaluate the influence of intragestational treatment with 9-[2-(phosphono-methoxy)-propyl]adenine (PMPA) on virus transmission to offspring. Eleven female cats (queens), chronically infected with FIV-B-2542 and bred to an FIV-negative male, produced a total of 25 viable and 18 nonviable term kittens. Overall, the vertical transmission rate by untreated queens was 22%, similar to that for HIV, which unfortunately precluded adequate assessment of PMPA efficacy. However, at delivery 9 of 10 queens (90%) had higher viral RNA loads in milk (4 x 10(4) to 4 x 10(8) viral copies/ml) than in plasma (5 x 10(3) to 2.5 x 10(6) viral copies/ml). Conversely, 10 of 11 queens (91%) had lower proviral loads in milk cells (0 to 10(2) proviral copies/microg DNA) than blood cells (10(2) to 10(4) proviral copies/microg DNA). Thus, FIV is concentrated in early milk despite relatively low proviral loads in milk cells, suggesting that virus may be actively secreted by the mammary gland for dissemination to offspring. FIV provides a model for the study of milk-borne lentivirus transmission and assessment of strategies to reduce postnatal HIV vertical transmission.

The antimicrobial properties of milkfat after partial hydrolysis by calf pregastric lipase

Studies on the kinetic characteristics of calf pregastric lipase (EC 3.1.1.3) have shown that it preferentially releases short chain fatty acids (SCFAs) from bovine milkfat. The released fatty acids form mixed micelle structures. The aim of this investigation has been to test whether hydrolysed milkfat is antimicrobial, and how the state of the emulsion alters the bactericidal or bacteriostatic effects. Partial hydrolysis of milkfat by pregastric lipase was carried out in two types of emulsion systems, containing either Triton X-100 or casein/lecithin, plus milkfat in citrate/phosphate buffer (pH 5.0-6.0). The concentrations and compositions of fatty acids were determined by gas chromatography. The minimum percentages of hydrolysed milkfat which affected growth and survival of selected Gram-positive and Gram-negative bacteria were measured. The bacterial experiments were repeated using pure fatty acids at similar concentrations. Lauric acid (C12:0) was found to be the most potent bactericidal fatty acid against Enterococcae (Gram-positive), and caprylic acid (C8:0) was the most potent against coliforms (Gram-negative). Use of Triton X-100 for milkfat emulsification provided a more compatible medium for studying bacterial growth in the hydrolysed milkfat than did use of casein/lecithin. The results also show that the antimicrobial effects of individual fatty acids released from hydrolysed milkfat were at least additive and suggest that hydrolysis of milkfat may be a significant factor in controlling growth of organisms imbibed with food in pre-weaned animals. The amount of pregastric catalyzed triglyceride hydrolysis in the digestive tract is sufficient to produce an antibacterial concentration of fatty acids and monoglycerides.

Shedding of porcine reproductive and respiratory syndrome virus in mammary gland secretions of sows

OBJECTIVE

To document shedding of porcine reproductive and respiratory syndrome (PRRS) virus in mammary gland secretions of experimentally inoculated sows, to evaluate effects of vaccination during gestation on virus shedding during the subsequent lactation, and to evaluate shedding of PRRS virus in milk of sows in commercial herds.

ANIMALS

6 sows seronegative for PRRS virus were used for experiment 1, and 2 sows were retained for experiment 2. For experiment 3, 202 sows in commercial herds were used.

PROCEDURE

In experiment 1, 2 sows were inoculated with PRRS virus, 2 sows were vaccinated with modified-live PRRS virus vaccine, and 2 sows served as control pigs. Mammary gland secretions were assayed for PRRS virus. In experiment 2, pregnant vaccinated sows from experiment 1 were vaccinated with another modified-live PRRS virus vaccine. Mammary gland secretions were assayed in the same manner as for experiment 1. For experiment 3, milk collected from 202 sows in commercial herds was assayed for PRRS virus.

RESULTS

In experiment 1, PRRS virus was detected in mammary gland secretions of both vaccinated and 1 of 2 virus-inoculated sows. In experiment 2, virus was not detected in samples from either vaccinated sow. In experiment 3, all samples yielded negative results.

CONCLUSIONS AND CLINICAL RELEVANCE

Naïve sows inoculated late in gestation shed PRRS virus in mammary secretions. Previous vaccination appeared to prevent shedding during the subsequent lactation. Results for samples obtained from sows in commercial herds suggested that virus shedding in mammary gland secretions of such sows is uncommon.

Immune components in porcine mammary secretions

Immune components present in mammary secretions are reviewed. In swine, the histological structure of the placenta prevents in utero transfer of immunoglobulins and mammary secretions are the sole source of maternal antibody for the neonate. In addition to immunoglobulins, porcine mammary secretions contain significant numbers of maternal cells of various types that may contribute to neonatal immunity, including phagocytes (neutrophils and macrophages), lymphocytes (B and T cells), and epithelial cells. Immunomodulating and/or antimicrobial substances, including lactoferrin, lysozyme, lactoperoxidase, and cytokines, are also present in mammary secretions and may contribute to the protection of the neonate. While the role of immunoglobulins in mammary secretions is well understood, the contribution of cellular components and non-specific immune factors to neonatal immunity remains to be defined.

Protective function of human milk: the milk fat globule

Human milk contains many components that protect the newborn against infection at a time when the infant's own defense mechanisms are poorly developed. Fat is one of the major nutrients in human milk. The fat is contained within milk fat globules composed of a core of triglyceride and a membrane consisting of phospholipids, cholesterol, proteins, and glycoproteins. Both the membrane and the core components can provide protection against microorganisms. The major protective membrane glycoproteins, mucin, and lactadherin are resistant to conditions in the newborn's stomach and maintain their structure and function even at low pH and in the presence of the proteolytic enzyme pepsin. The core triglycerides upon hydrolysis by digestive lipases (especially gastric lipase, which is well developed in the newborn) produce free fatty acids and monoglycerides, amphiphylic substances able to lyse enveloped viruses, bacteria, and protozoa. Therefore, in addition to its nutritional value, the fat in human milk has a major protective function.

The effect of pH on the inhibition of bacterial growth by physiological concentrations of butyric acid: implications for neonates fed on suckled milk

Butyric acid is released from milk by pre-intestinal lipases during suckling. It is also known to inhibit bacterial growth. To investigate whether butyric acid may be a significant factor in controlling bacterial growth in the stomach of pre-weaned animals, the ability of butyric acid to inhibit growth of selected bacteria was tested over physiological ranges of pH and butyric acid concentrations. Six enteric and environmental strains of bacteria were used: two strains of Escherichia coli, Klebsiella pneumoniae, Enterococcus faecium, Enterococcus faecalis, and Enterococcus casseliflavus. At pH 4.5 and 5.0, the growth of all organisms was significantly inhibited in the presence of butyrate, and in some cases growth was completely arrested. At pH 6.0, butyric acid did not affect bacterial growth until the concentration reached 40 mM. The maximum concentration of butyric acid available in cow's milk after incubation with pre-gastric lipase is approximately 16 mM, which would be sufficient to prevent growth of the organisms tested at pH values occurring in the stomach. Therefore, butyric acid inhibition of bacterial growth may explain in part, the role of pre-intestinal lipases in young animals' natural defenses against bacteria in ingested food prior to weaning.

Killing of Chlamydia trachomatis by novel antimicrobial lipids adapted from compounds in human breast milk

The development of new methods for prevention of sexually transmitted Chlamydia trachomatis infection is a top public health priority. Topical self-administered vaginal microbicides represent one such approach in which the organism is eradicated at the time of initial exposure. To this end, we examined the activity of five synthetic lipids adapted from naturally occurring compounds found in human breast milk. C. trachomatis serovar D or F elementary bodies were added to serial dilutions of the lipids and incubated for various times. Aliquots were then cultured in monolayers of McCoy cells, and inclusions were counted. A 7.5 mM concentration of 2-O-octyl-sn-glycerol completely prevented growth of C. trachomatis after 120 min of contact with the organism. The remaining lipids, 1-O-octyl-, 1-O-heptyl-, 2-O-hexyl-, and 1-O-hexyl-sn-glycerol, showed less activity. On electron microscopic examination, the lipids were shown to have disrupted the chlamydial inner membrane, allowing leakage of the cytoplasmic contents from the cell. Lipid activity was unaffected by the presence of 10% human blood or alterations in pH from 4.0 to 8.0, conditions reflecting those sometimes found in the vagina. Our results suggest that these lipids, especially 2-O-octyl-sn-glycerol, may be effective as topical microbicides in preventing the transmission of C. trachomatis. Further efficacy and toxicity studies with these lipids and assessment of their activity against other sexually transmitted disease pathogens are in progress.

Special properties of human milk

In this review, several nutritional and nonnutritive differences between mothers' milk and formula and their relationship to neonatal gastrointestinal and immune processes are discussed. The dynamic relationship of human milk as evidenced by its changing composition, unique bioactive and immunologic properties, and specialized cellular components is further delineated. The clinical significance and relevance of these findings to the clinician are then presented. Lastly, educational strategies, their effectiveness in promoting breastfeeding, and an approach that might be taken by the clinician to encourage breastfeeding are outlined.

Inactivation of enveloped viruses in human bodily fluids by purified lipids

Antimicrobial lipids are found in mucosal secretions and are one of a number of nonimmunologic and nonspecific protective factors found at mucosal surfaces. Lipids can inactivate enveloped viruses, bacteria, fungi, and protozoa. Lipid-dependent antimicrobial activity at mucosal surfaces is due to certain monoglycerides and fatty acids that are released from triglycerides by lipolytic activity. Medium chain length antiviral lipids can be added to human blood products that contain HIV-1 and HIV-2 and reduce the cell-free virus concentration by as much as 11 log10 TCID50/ml. The presence of lipids does not interfere with most clinical assays performed on human blood samples. Antimicrobial lipids can disrupt cell membranes and therefore lyse leukocytes which potentially carry virus. Genital mucosal epithelial cells should be protected from damage by the mucous layer. Preliminary studies indicate that lipids decrease sperm motility and viability suggesting that lipids may potentially be used as combination spermicidal and virucidal agents.