Background: Despite the continuous shedding of HIV infected blood into the oral cavity and the detectable presence of the AIDS virus at a high frequency, human saliva is reported to inhibit oral transmission of HIV through kissing, dental treatment, biting, and aerosolization. The purpose of this study was to purify salivary MUC5B and MUC7 mucins from crude saliva and determine their anti-HIV-1 activities.

It has been reported that breast-feeding is responsible for approximately 40% of the HIV transmissions from HIV-positive mothers to children. Human breast milk, however, is known to contain numerous biologically active components which protect breast-fed infants against bacteria, viruses, and toxins. The purpose of this study was to purify and characterize breast milk mucin and to determine its anti-HIV-1 activity in an HIV inhibition assay. Sepharose CL-4B column chromatography and caesium chloride isopycnic density gradient purification were used to isolate and purify the mucin. Following Western blotting and amino acid analysis, an HIV-1 inhibition assay was carried out to determine the anti-HIV-1 activity of crude breast milk and purified milk mucin (MUC1) by incubating them with HIV-1 prior to infection of the human T lymphoblastoid cell line (CEM SS cells). SDS-PAGE analysis of the mucin, together with its amino acid composition and Western blotting, suggested that this purified mucin from human breast milk was MUC1. The HIV inhibition assay revealed that while the purified milk mucin (MUC1) inhibited the HIV-1 activity by approximately 97%, there was no inhibition of the HIV-1 activity by crude breast milk. Although the reason for this is not clear, it is likely that because the MUC1 in crude milk is enclosed by fat globules, there may not be any physical contact between the mucin and the virus in the crude breast milk. Thus, there is a need to free the mucin from the fat globules for it to be effective against the virus.

Mucins are high molecular weight glycoproteins with complex oligosaccharide side chains attached to the apomucin protein backbone by O-glycosidic linkage; they are found in crude mucus gels that protect epithelial surfaces in the major tracts of the body and as transmembrane proteins expressed on the apical cell surface of glandular and ductal epithelia of various organs. Changes in the sequence of glycosylation of mucins in different settings generate a variety of epitopes in the oligosaccharide side chains of mucins, including newly expressed blood-group antigens, distinguishing between normal and diseased states. Tumour-associated epitopes on mucins and their antigenicity make them suitable as immunotargets on malignant epithelial cells and their secretions, creating a surge of interest in mucins as diagnostic and prognostic markers for various diseases, and even influencing the design of mucin-based vaccines. This review discusses the emerging roles of mucins such as MUC1 and MUC4 in cancer and some other diseases, and stresses how underglycosylated and truncated mucins are exploited as markers of disease and to monitor widespread metastasis, making them useful in patient management. Furthermore the type, pattern and amount of mucin secreted in some tissues have been considered in the classification and terminology of neoplasia and in specific organs such as the pancreas. These factors have been instrumental in pathological classification, diagnosis and prognostication of neoplasia.

Background/Aims: Gastric cancer, a fatal malignancy, is prevalent in the Western Cape region of South Africa. The aim of this study was a biochemical characterisation of gastric mucins in this disease, compared with gastric ulceration and controls from transplant donors. Methods: Mucins were extracted in a denaturing medium (to prevent endogenous proteolysis) and purified by caesium chloride density gradient ultracentrifugation. Analysis of mucin was by gel filtration, SDS-PAGE and Western blotting methods. Results: All samples of mucin when analysed by gel filtration were found to contain polymeric glycoprotein together with varying amounts of lower-molecular-weight glycoprotein. SDS-PAGE and Western blot analysis showed that diseased stomachs had glycopeptides of a wider range in size and antigenicity with a greater number of smaller fragments immunoreactive to monoclonal antibodies 2–12M1 and 9–13M1. We identified by SDS-PAGE a glycoprotein which co-fractionates in a caesium chloride density gradient with mucins isolated from gastrectomy specimens resected for carcinoma and peptic ulceration and which was absent from mucins of the transplant donor control group. This neuraminidase-sensitive glycoprotein resisted dissociation from mucin during purification in a 3.5 M CsCl density gradient but was partially separable by Sepharose 2B gel chromatography and heat treatment (100°C, 2.0 min) in SDS. Chemical analysis of the glycoprotein by HPLC favours it being an N-linked glycoprotein. Its non-ideal electrophoretic properties make its exact size estimation difficult and we ascribe to it a broad size range of M_r ∼55–65 kD. Conclusion: We conclude that mucins from diseased stomachs were more degraded than those from donors and that the diseased mucosa reproducibly secretes a M_r ∼55–65 kD glycoprotein, the role of which needs to be established.

A 58-year-old man with a 1 year history of progressive abdominal distension underwent a laparotomy for pseudomyxoma peritonei. The mucin was identified and characterized in the present study. Approximately 6 L of crude mucus in the sol (highly viscous) and gel (semisolid) phases was obtained from the patient's peritoneal cavity. The sol material was briefly homogenized followed by slow stirring at dilutions of up to 1:10 with 6 mol/L guanidinium chloride and proteolytic inhibitors for periods of up to 48 h. Preparative and analytical gel filtration on Sepharose 2B showed some PAS-positive material eluting in the void volume accompanied by equal or larger amounts of protein in the void and included volumes of the columns. Sodium dodecylsulfate-polyacrylamide gel electrophoresis of purified mucin on a 4-20% gradient gel showed PAS-positive material on the top of the running gel and a distinct smaller-sized species of mucin of higher electrophoretic mobility with background material in between the large and small mucin. Western blot (confirmed by immunohistochemical analysis) after agarose gel electrophoresis showed the presence of MUC2, MUC5AC and MUC5B in the mucus. There was no MUC1, MUC1core or MUC6 in the tissue. Histopathological examination confirmed a mucinous appendicular adenocarcinoma. Histology showed the mucin to be predominantly of the sulfated and non-sulfated acidic type. Serine, threonine and proline comprised 21.6% of the total amino acid composition of the sample. The viscous nature of the material is due to the presence of three gel-forming mucins and possibly to its high content of protein.

BackgroundMucins are large O-linked glycosylated proteins which give mucus their gel-forming properties. There are indications that mucus and mucins in saliva, breast milk and in the cervical plug inhibit the human immunodeficiency virus (HIV-1) in an in vitro assay.Main body of abstractCrude mucus gels form continuous layers on the epithelial surfaces of the major internal tracts of the body and protect these epithelial surfaces against aggressive luminal factors such as hydrochloric acid and pepsin proteolysis in the stomach lumen, the movement of hard faecal pellets in the colon at high pressure, the effects of shear against the vaginal epithelium during intercourse and the presence of foreign substances in the respiratory airways. Tumour-associated epitopes on mucins make them suitable as immune-targets on malignant epithelial cells, rendering mucins important as diagnostic and prognostic markers for various diseases, even influencing the design of mucin-based vaccines.Sub-Saharan Africa has the highest prevalence of HIV-AIDS in the world. The main points of viral transmission are via the vaginal epithelium during sexual intercourse and mother-to-child transmission during breast-feeding. There have been many studies showing that several body fluids have components that prevent the transmission of HIV-1 from infected to non-infected persons through various forms of contact.Crude saliva and its purified mucins, MUC5B and MUC7, and the purified mucins from breast milk, MUC1 and MUC4 and pregnancy plug cervical mucus (MUC2, MUC5AC, MUC5B and MUC6), inhibit HIV-1 in an in vitro assay. There are conflicting reports of whether crude breast-milk inhibits HIV-1 in an in vitro assay. However studies with a humanised BLT mouse show that breast-milk does inhibit HIV and that breast-feeding is still advisable even amongst HIV-positive women in under-resourced areas, preferably in conjunction with anti-retroviral treatment.ConclusionThese findings raise questions of how such a naturally occurring biological substance such as mucus, with remarkable protective properties of epithelial surfaces against aggressive luminal factors in delicate locations, could be used as a tool in the fight against HIV-AIDS, which has reached epidemic proportions in sub-Saharan Africa.

Background: The female reproductive tract is amongst the main routes for Human Immunodeficiency Virus (HIV) transmission. Cervical mucus however is known to protect the female reproductive tract from bacterial invasion and fluid loss and regulates and facilitates sperm transport to the upper reproductive tract. The purpose of this study was to purify and characterize pregnancy plug mucins and determine their anti-HIV-1 activity in an HIV inhibition assay.

Human breast milk is known to contain numerous biologically active components which protect breast fed infants against microbes, viruses, and toxins. The purpose of this study was to purify and characterize the breast milk mucin and determine its anti-poxvirus activity. In this study human milk mucin, free of contaminant protein and of sufficient quantity for further analysis, was isolated and purified by Sepharose CL-4B gel filtration and cesiumchloride density-gradient centrifugation. Based on the criteria of size and appearance of the bands and their electrophoretic mobility on sodium dodecyl sulfate polyacrylamide-gel electrophoresis, Western blotting together with the amino acid analysis, it is very likely that the human breast milk mucin is MUC1. It was shown that this breast milk mucin inhibits poxvirus activity by 100% using an inhibition assay with a viral concentration of 2.4 million plaque-forming units/ml. As the milk mucin seems to aggregate poxviruses prior to their entry into host cells, it is possible that this mucin may also inhibit other enveloped viruses such as HIV from entry into host cells.