HIV recovery from saliva before and after dental treatment: inhibitors may have critical role in viral inactivation

HIV and SIV in Body Fluids: From Breast Milk to the Genitourinary Tract

HIV-1 is present in many secretions including oral, intestinal, genital, and breast milk. However, most people exposed to HIV-1 within these mucosal compartments do not become infected despite often frequent and repetitive exposure over prolonged periods of time. In this review, we discuss what is known about the levels of cell-free HIV RNA, cell-associated HIV DNA and cell-associated HIV RNA in external secretions. Levels of virus are usually lower than contemporaneously obtained blood, increased in settings of inflammation and infection, and decreased in response to antiretroviral therapy. Additionally, each mucosal compartment has unique innate and adaptive immune responses that affect the composition and presence of HIV-1 within each external secretion. We discuss the current state of knowledge about the types and amounts of virus present in the various excretions, touch on innate and adaptive immune responses as they affect viral levels, and highlight important areas for further study.

Innate immunity in HIV-1 infection: epithelial and non-specific host factors of mucosal immunity- a workshop report

The interplay between HIV-1 and epithelial cells represents a critical aspect in mucosal HIV-1 transmission. Epithelial cells lining the oral cavity cover subepithelial tissues, which contain virus-susceptible host cells including CD4(+) T lymphocytes, monocytes/macrophages, and dendritic cells. Oral epithelia are among the sites of first exposure to both cell-free and cell-associated virus HIV-1 through breast-feeding and oral-genital contact. However, oral mucosa is considered to be naturally resistant to HIV-1 transmission. Oral epithelial cells have been shown to play a crucial role in innate host defense. Nevertheless, it is not clear to what degree these local innate immune factors contribute to HIV-1 resistance of the oral mucosa. This review paper addressed the following issues that were discussed at the 7th World Workshop on Oral Health and Disease in AIDS held in Hyderabad, India, during November 6-9, 2014: (i) What is the fate of HIV-1 after interactions with oral epithelial cells?; (ii) What are the keratinocyte and other anti-HIV effector oral factors, and how do they contribute to mucosal protection?; (iii) How can HIV-1 interactions with oral epithelium affect activation and populations of local immune cells?; (iv) How can HIV-1 interactions alter functions of oral epithelial cells?

Saliva and viral infections

Over the last 10 years there have been only a handful of publications dealing with the oral virome, which is in contrast to the oral microbiome, an area that has seen considerable interest. Here, we survey viral infections in general and then focus on those viruses that are found in and/or are transmitted via the oral cavity; norovirus, rabies, human papillomavirus, Epstein‐Barr virus, herpes simplex viruses, hepatitis C virus, and HIV. Increasingly, viral infections have been diagnosed using an oral sample (e.g. saliva mucosal transudate or an oral swab) instead of blood or urine. The results of two studies using a rapid and semi‐quantitative lateral flow assay format demonstrating the correlation of HIV anti‐IgG/sIgA detection with saliva and serum samples are presented. When immediate detection of infection is important, point‐of‐care devices that obtain a non‐invasive sample from the oral cavity can be used to provide a first line diagnosis to assist in determining appropriate counselling and therapeutic path for an increasing number of diseases.

Infection Transmission by Saliva and the Paradoxical Protective Role of Saliva

Saliva is produced by both major (parotid and submandibular and sublingual) and minor (located in the mouth) glands, with different constituents and properties between the two groups. In the mouth saliva is a colorless, odorless, tasteless, watery liquid containing 99% water and 1% organic and inorganic substances and dissolved gases, mainly oxygen and carbon dioxide. Salivary constituents can be grouped into proteins (e.g., amylase and lysozyme), organic molecules (e.g., urea, lipids, and glucose mainly), and electrolytes (e.g., sodium, calcium, chlorine, and phosphates). Cellular elements such as epithelial cells, leukocytes and various hormones, and vitamins have also been detected. The composition of saliva is modified, depending on factors such as secreted amount, circadian rhythm, duration and nature of stimuli, diet, and medication intake, among others.

Detecting viruses by using salivary diagnostics

BACKGROUND

Diagnostics that involve the use of oral fluids have become increasingly available commercially in recent years and are of particular interest because of their relative ease of use, low cost and noninvasive collection of oral fluid for testing.

TYPES OF STUDIES REVIEWED

The authors discuss the use of salivary diagnostics for virus detection with an emphasis on rapid detection of infection by using point-of-care devices. In particular, they review salivary diagnostics for human immunodeficiency virus, hepatitis C virus and human papillomavirus. Oral mucosal transudate contains secretory immunoglobulin (Ig) A, as well as IgM and IgG, which makes it a good source for immunodiagnostic-based devices.

CLINICAL IMPLICATIONS

Because patients often visit a dentist more regularly than they do a physician, there is increased discussion in the dental community regarding the need for practitioners to be aware of salivary diagnostics and to be willing and able to administer these tests to their patients.

Impact of mucosal inflammation on oral simian immunodeficiency virus transmission

Mucosal tissues are the primary route of transmission for most respiratory and sexually transmitted diseases, including human immunodeficiency virus (HIV). There is epidemiological evidence that genital mucosal inflammation leads to enhanced HIV type 1 (HIV-1) transmission. The objective of this study was to assess the influence of periodontal inflammation on oral HIV transmission using a nonhuman primate model of teeth ligature-induced periodontitis. Simian immunodeficiency virus (SIV) was nontraumatically applied to the gingiva after moderate gingivitis was identified through clinical and immunologic analyses (presence of inflammatory cytokines). Overall oral SIV infection rates were similar in the gingivitis-induced and control groups (5 infections following 12 SIV administrations for each), although more macaques were infected with multiple viral variants in the gingivitis group. SIV infection also affected the levels of antiviral and inflammatory cytokines in the gingival crevicular fluid, and a synergistic effect was observed, with alpha interferon and interferon-inducible protein 10 undergoing significant elevations following SIV infection in macaques with gingivitis compared to controls. These increases in antiviral and inflammatory immune modulators in the SIV-infected gingivitis macaques could also be observed in blood plasma, although the effects at both compartments were generally restricted to the acute phase of the infection. In conclusion, while moderate gingivitis was not associated with increased susceptibility to oral SIV infection, it resulted in elevated levels of cytokines in the oral mucosa and plasma of the SIV-infected macaques. These findings suggest a synergy between mucosal inflammation and SIV infection, creating an immune milieu that impacts the early stages of the SIV infection with potential implications for long-term pathogenesis.

Anti-HIV-1 activity of salivary MUC5B and MUC7 mucins from HIV patients with different CD4 counts

BACKGROUND

We have previously shown that MUC5B and MUC7 mucins from saliva of HIV negative individuals inhibit HIV-1 activity by 100% in an in vitro assay. The purpose of this subsequent study was to investigate whether MUC5B and MUC7 from saliva of HIV patients or with full blown AIDS had a similar inhibitory activity against the virus.

METHODS

Salivary MUC5B and MUC7 from HIV patients with different CD4 counts (< 200, 200-400 and > 400) were incubated with HIV-1 prior to infection of the human T lymphoblastoid cell line (CEM SS cells). Cells were then cultured and viral replication was measured by a qualitative p24 antigen assay. The size, charge and immunoreactivity of mucins from HIV negative and positive individuals was also analysed by SDS-PAGE, Western blot and ELISA respectively.

RESULTS

It was shown that irrespective of their CD4 counts both MUC5B and MUC7 from HIV patients, unlike the MUC5B and MUC7 from HIV negative individuals, did not inhibit HIV-1 activity. Size, charge and immunoreactivity differences between the mucins from HIV negative and positive individuals and among the mucins from HIV patients of different CD4 count was observed by SDS-PAGE, Western blot and ELISA.

CONCLUSIONS

Purified salivary mucins from HIV positive patients do not inhibit the AIDS virus in an in vitro assay. Although the reason for the inability of mucins from infected individuals to inhibit the virus is not known, it is likely that there is an alteration of the glycosylation pattern, and therefore of charge of mucin, in HIV positive patients. The ability to inhibit the virus by aggregation by sugar chains is thus diminished.

Heterosexual spread of HIV infection

Sexual transmission is the most common route of spread of human immunodeficiency virus (HIV), with heterosexual transmission of HIV infection accounting for 90% of those infected in 1992 and over 75% of the 10–12 million of those infected to date worldwide. Yet, heterosexual transmission is poorly understood. Since HIV can be transmitted from HIV-infected people who are asymptomatic as well as from those who have the acquired immunodeficiency syndrome (AIDS), we must better define the potential for transmission of HIV from HIV-infected individuals as well as the factors which influence the susceptibility of HIV-uninfected individuals.

Oral keratinocytes support non-replicative infection and transfer of harbored HIV-1 to permissive cells

Background

Oral keratinocytes on the mucosal surface are frequently exposed to HIV-1 through contact with infected sexual partners or nursing mothers. To determine the plausibility that oral keratinocytes are primary targets of HIV-1, we tested the hypothesis that HIV-1 infects oral keratinocytes in a restricted manner.

Results

To study the fate of HIV-1, immortalized oral keratinocytes (OKF6/TERT-2; TERT-2 cells) were characterized for the fate of HIV-specific RNA and DNA. At 6 h post inoculation with X4 or R5-tropic HIV-1, HIV-1gag RNA was detected maximally within TERT-2 cells. Reverse transcriptase activity in TERT-2 cells was confirmed by VSV-G-mediated infection with HIV-NL4-3Δenv-EGFP. AZT inhibited EGFP expression in a dose-dependent manner, suggesting that viral replication can be supported if receptors are bypassed. Within 3 h post inoculation, integrated HIV-1 DNA was detected in TERT-2 cell nuclei and persisted after subculture. Multiply spliced and unspliced HIV-1 mRNAs were not detectable up to 72 h post inoculation, suggesting that HIV replication may abort and that infection is non-productive. Within 48 h post inoculation, however, virus harbored by CD4 negative TERT-2 cells trans infected co-cultured peripheral blood mononuclear cells (PBMCs) or MOLT4 cells (CD4+ CCR5+) by direct cell-to-cell transfer or by releasing low levels of infectious virions. Primary tonsil epithelial cells also trans infected HIV-1 to permissive cells in a donor-specific manner.

Conclusion

Oral keratinocytes appear, therefore, to support stable non-replicative integration, while harboring and transmitting infectious X4- or R5-tropic HIV-1 to permissive cells for up to 48 h.

The role of crude human saliva and purified salivary MUC5B and MUC7 mucins in the inhibition of Human Immunodeficiency Virus type 1 in an inhibition assay

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.

METHODS

Following Sepharose CL-4B column chromatography and caesium chloride isopycnic density-gradient ultra-centrifugation, the purity and identity of the mucins was determined by SDS-PAGE and Western blotting analysis respectively. Subsequently an HIV-1 inhibition assay was carried out to determine the anti-HIV-1 activity of the crude saliva and purified salivary mucins by incubating them with subtype D HIV-1 prior to infection of the CD4+ CEM SS cells.

RESULTS

Western blotting analysis confirmed that the mucin in the void volume is MUC5B and the mucin in the included volume is MUC7. The HIV inhibition assay revealed that both the crude saliva and salivary MUC5B and MUC7 mucins inhibited HIV-1 activity by 100%.

CONCLUSION

Although the mechanism of action is not clear the carbohydrate moieties of the salivary mucins may trap or aggregate the virus and prevent host cell entry.

Oral transmission of HIV, reality or fiction? An update

Human immunodeficiency virus (HIV) and many other viruses can be isolated in blood and body fluids, including saliva, and can be transmitted by genital-genital and especially anal-genital sexual activity. The risk of transmission of HIV via oral sexual practices is very low. Unlike other mucosal areas of the body, the oral cavity appears to be an extremely uncommon transmission route for HIV. We present a review of available evidence on the oral-genital transmission of HIV and analyse the factors that act to protect oral tissues from infection, thereby reducing the risk of HIV transmission by oral sex. Among these factors we highlight the levels of HIV RNA in saliva, presence of fewer CD4+ target cells, presence of IgA antibodies in saliva, presence of other infections in the oral cavity and the endogenous salivary antiviral factors lysozyme, defensins, thrombospondin and secretory leucocyte protease inhibitor (SLPI).

Human epithelial beta-defensins 2 and 3 inhibit HIV-1 replication

OBJECTIVE

Mechanisms underlying mucosal transmission of HIV-1 are incompletely understood. We describe the anti-HIV-1 activity of human beta-defensins (hBD), small cationic molecules that provide protection at mucosal surfaces.

METHODS AND RESULTS

HIV-1 induced expression of hBD-2 and -3 mRNA (but not that of hBD-1) 4- to 78-fold, respectively, above baseline in normal human oral epithelial cells. HIV-1 failed to infect these cells, even after 5 days of exposure. Recombinant hBD-1 had no antiviral activity, while rhBD-2 and rhBD-3 showed concentration-dependent inhibition of HIV-1 replication without cellular toxicity. Inhibition was greater against CXCR4-tropic than against the CCR5-tropic HIV-1 isolates. hBD-2 and hBD-3 induced an irreversible effect on virion infectivity, with electron microscopy confirming binding of hBDs to viral particles. Finally, hBD-2 and -3 induced downmodulation of the HIV-1 coreceptor CXCR4 (but not CCR5) in peripheral blood mononuclear cells and T lymphocytic cells as shown by confocal microscopy and flow cytometry.

CONCLUSIONS

This study shows for the first time that HIV-1 induces beta-defensin expression in human oral epithelial cells and that beta-defensins block HIV-1 replication via a direct interaction with virions and through modulation of the CXCR4 coreceptor. These properties may be exploited as strategies for mucosal protection against HIV-1 transmission.

Measurements of HIV viral loads from different levels of the respiratory tract

BACKGROUND

The lung is a common site of disease in HIV infection. Virus has been detected in BAL fluid (BALF) and saliva. However, the relationship between viral loads detected at different levels of the respiratory tract is unknown.

METHOD

We measured simultaneous HIV viral loads in parotid saliva (PS), bronchial fluid (BF), BALF, and plasma by reverse transcription polymerase chain reaction in 20 HIV-infected individuals.

RESULTS

HIV was detected in 53% of BALF samples, 15% of BF samples, 5% of PS samples, and 88% of plasma samples. Viral loads in plasma and BALF samples were positively correlated. There were significantly higher levels of HIV viral load in both plasma and BALF in subjects with CD4 counts of < 200 cells/ microL compared to those with higher counts. Antiretroviral therapy (ART) was associated with lower BALF and plasma viral loads, and the effect in BALF was independent of the plasma viral load. Interestingly, smoking also was associated with lower levels of both BAL and BF viral loads, independent of the plasma viral load.

CONCLUSION

These data demonstrate that while HIV can be detected in the respiratory tract, the viral load is influenced by both local factors (ie, level of the respiratory tree and cigarette smoking) and systemic factors (ie, ART and peripheral CD4 count).

Inhibition of HIV-1 IIIB and clinical isolates by human parotid, submandibular, sublingual and palatine saliva

Human saliva is known to possess components that decrease the HIV-1 infectivity in vitro. The mechanism of how these components inhibit the infectivity is still not clear on the molecular level. The purpose of this study was to discriminate between serous and mucous components with respect to inhibitory capacity and site of action. We have used total saliva and saliva from the major (sero)mucous glands: submandibular gland, sublingual glands, and glands in the palate, in comparison with the serous parotid glands. HIV-1 IIIB and primary variants were incubated with saliva, and inhibition of HIV-1-infection was determined by analysing the cytopathic effect on MT-2 cells. Mucous saliva, as well as serous saliva, contained high molecular weight components that reduced HIV-1-infectivity, at least partially by entrapment of the virus particles. Lower molecular weight components in all types of saliva possessed strong HIV-1 neutralizing capacity. Using pro-viral DNA synthesis by reverse transcription as a discrimination point in the replication cycle, the results indicated that part of the saliva samples acted before, but others after, this point. In conclusion, saliva inhibits HIV-1-infection by the action of high molecular weight components in combination with low molecular weight components from serous as well as mucous saliva, affecting different stages of the infection cycle.

Positive and negative aspects of the human immunodeficiency virus protease: development of inhibitors versus its role in AIDS pathogenesis

In this review we summarize multiple aspects of the human immunodeficiency virus (HIV) protease from both structural and functional viewpoints. After an introductory overview, we provide an up-to-date status report on protease inhibitors (PI). This proceeds from a discussion of PI structural design, to how PI are optimally utilized in highly active antiretroviral triple therapy (one PI along with two reverse transcriptase inhibitors), the emergence of PI resistance, and the natural role of secretory leukocyte PI. Then we switch to another focus: the interaction of HIV protease with other genes in acute and persistent infection, which in turn may have an effect on AIDS pathogenesis. We conclude with a discussion on future directions in HIV treatment, involving multiple-target anti-HIV therapy, vaccine development, and novel reactivation-inhibitory reagents.

Innate antiviral defenses in body fluids and tissues

Innate, non-specific, resistance mechanisms are important barriers to pathogens, particularly delaying virus multiplication at the onset of infections. These innate defense mechanisms include a series of mechanical barriers, pre-existing inhibitory molecules, and cellular responses with antimicrobial activity. The antiviral activities of these innate inhibitors reside in a variety of partly characterized substances. This review presents the innate antiviral inhibitors in cell cultures, urine, serum, the gastrointestinal tract, the nervous system, tissues of crustaceans, and saliva. Medical adaptation of the innate antiviral defense mechanisms may be useful for prevention and treatment of viral infections.

HIV topic update: oro-genital transmission of HIV

Several viruses, including the human immunodeficiency virus (HIV), can be found in blood and many body fluids including saliva, and are transmissible sexually across genital and particularly anal mucosae. A persisting concern has been the question of transmission of HIV by oral sexual practices. This review discusses the evidence for oro-genital transmission of HIV, detailing the presence and infectivity of HIV in genital fluids and saliva, the case reports and epidemiology of oro-genital HIV transmission, and the evidence from animal studies. Oral intercourse is not risk-free. The evidence suggests that the risk of HIV transmission from oro-genital sexual practices is substantially lower than that from penile-vaginal or penile-anal intercourse, that exposure to saliva presents a considerably lower risk than exposure to semen, and that oral trauma and ulcerative conditions might increase the risk of HIV transmission.

Enhanced secretory leukocyte protease inhibitor in human immunodeficiency virus type 1-infected patients

Secretory leukocyte protease inhibitor (SLPI) has been found to possess activity against the human immunodeficiency virus type 1 (HIV-1) in vitro at physiological concentrations. A study was undertaken to evaluate SLPI levels in human saliva and plasma among HIV-positive (HIV(+)) patients with various HIV-1 viral loads in comparison to uninfected controls. Whole blood in EDTA and unstimulated saliva samples were collected from 37 HIV(+) patients, of whom 20 had a history of intravenous drug abuse (IVDA). Control samples were collected from 20 appropriate age- and sex-matched HIV-1-negative individuals. SLPI was estimated from both saliva and serum samples by an enzyme-linked immunosorbent assay. HIV viral load was determined using a quantitative reverse transcription-PCR. SLPI levels were increased 16.7% in plasma and 10.3% in saliva among HIV(+) patients in comparison to uninfected controls. SLPI levels were increased 5.9% in saliva and 3.9% in plasma among HIV(+) patients with a high viral load (>10,000 copies/ml) as compared to patients with a low viral load (<400 copies/ml). Only 23% of patients with a high viral load used combination therapy with protease inhibitor drugs, whereas 92.9% of HIV(+) patients with a low viral load used protease inhibitors. SLPI levels did not differ significantly among the IVDA patients, patients with different viral loads, or patients using protease inhibitor drugs. There was a statistically significant increase in SLPI levels in saliva among HIV patients in comparison to non-HIV-infected controls. An increase in SLPI levels among HIV(+) patients may be a natural consequence of HIV pathogenesis and an important factor in preventing oral transmission of HIV, but this increase may not be evident during plasma viremia in patients with a high viral load.

Endogenous salivary inhibitors of human immunodeficiency virus

The human immunodeficiency virus type 1 (HIV-1) is rarely transmitted through salivary secretions, due in part to the presence of endogenous inhibitors. Here, the protective characteristics of the intraoral environment are summarized and inhibitory factors that reduce HIV-1 infectivity in vitro described, focusing on secretory leucocyte protease inhibitor (SLPI), a 12-kDa mucosal protein that blocks HIV infection in several cell-culture systems. SLPI appears to interact with a cellular surface molecule to limit viral entry into target cells. To determine whether the inhibitor has a similar role in vivo, the contribution of salivary SLPI to anti-HIV-1 activity was assessed. Whole unstimulated filtered salivas from infected and uninfected donors contained similar concentrations of the inhibitor. Depletion from SLPI filtered saliva produced a corresponding loss of inhibitory activity. In general, filtered whole salivas obtained from 10 donors had antiviral activities that correlated positively with SLPI concentrations. However, some samples having SLPI well below the concentration required for inhibitory activity in vitro exhibited modest inhibition, suggesting the presence of other anti-HIV-1 components in oral fluids. Thus, SLPI is a major but not sole inhibitor of this virus in saliva.

Submandibular salivary proteases: lack of a role in anti-HIV activity

Whole human saliva contains a number of proteolytic enzymes, mostly derived from white blood cells and bacteria in the oral cavity. However, less information is available regarding proteases produced by salivary glands and present in salivary secretions. In the present study, we have analyzed submandibular saliva, collected without contaminating cells, and identified multiple proteolytic activities. These have been characterized in terms of their susceptibility to a series of protease inhibitors. The submandibular saliva proteases were shown to be sensitive to both serine and acidic protease inhibitors. We also used protease inhibitors to determine if salivary proteolytic activity was involved in the inhibition of HIV infectivity seen when the virus is incubated with human saliva. This anti-HIV activity has been reported to occur in whole saliva and in ductal saliva obtained from both the parotid and submandibular glands, with highest levels of activity present in the latter fluid. Protease inhibitors, at concentrations sufficient to block salivary proteolytic activity in an in vitro infectivity assay, did not block the anti-HIV effects of saliva, suggesting that the salivary proteases are not responsible for the inhibition of HIV-1 infectivity.

Identification of a CD36-related thrombospondin 1-binding domain in HIV-1 envelope glycoprotein gp120: relationship to HIV-1-specific inhibitory factors in human saliva

Human and non-human primate salivas retard the infectivity of HIV-1 in vitro and in vivo. Because thrombospondin 1 (TSP1), a high molecular weight trimeric glycoprotein, is concentrated in saliva and can inhibit the infectivity of diverse pathogens in vitro, we sought to determine the role of TSP1 in suppression of HIV infectivity. Sequence analysis revealed a TSP1 recognition motif, previously defined for the CD36 gene family of cell adhesion receptors, in conserved regions flanking the disulfide-linked cysteine residues of the V3 loop of HIV envelope glycoprotein gp120, important for HIV binding to its high affinity cellular receptor CD4. Using solid-phase in vitro binding assays, we demonstrate direct binding of radiolabeled TSP1 to immobilized recombinant gp120. Based on peptide blocking experiments, the TSP1-gp120 interaction involves CSVTCG sequences in the type 1 properdin-like repeats of TSP1, the known binding site for CD36. TSP1 and fusion proteins derived from CD36-related TSP1-binding domains were able to compete with radiolabeled soluble CD4 binding to immobilized gp120. In parallel, purified TSP1 inhibited HIV-1 infection of peripheral blood mononuclear cells and transformed T and promonocytic cell lines. Levels of TSP1 required for both viral aggregation and direct blockade of HIV-1 infection were physiologic, and affinity depletion of salivary TSP1 abrogated >70% of the inhibitory effect of whole saliva on HIV infectivity. Characterization of TSP1-gp120 binding specificity suggests a mechanism for direct blockade of HIV infectivity that might be exploited to retard HIV transmission that occurs via mucosal routes.

Inhibition of Human Immunodeficiency Virus Type 1 Infectivity by Secretory Leukocyte Protease Inhibitor Occurs Prior to Viral Reverse Transcription

Infection of monocytes with human immunodeficiency virus type 1Ba-L (HIV-1Ba-L ) is significantly inhibited by treatment with the serine protease inhibitor, secretory leukocyte protease inhibitor (SLPI). SLPI does not appear to act on virus directly, but rather the inhibitory activity is most likely due to interaction with the host cell. The current study was initiated to investigate how SLPI interacts with monocytes to inhibit infection. SLPI was found to bind to monocytes with high affinity to a single class of receptor sites (∼7,000 receptors per monocyte, KD = 3.6 nmol/L). The putative SLPI receptor was identified as a surface protein with a molecular weight of 55 ± 5 kD. A well-characterized function of SLPI is inhibition of neutrophil elastase and cathepsin G. However, two SLPI mutants (or muteins) that contain single amino acid substitutions and exhibit greatly reduced protease inhibitory activity still bound to monocytes and retained anti–HIV-1 activity. SLPI consists of two domains, of which the C-terminal domain contains the protease inhibiting region. However, when tested independently, neither domain had potent anti–HIV-1 activity. SLPI binding neither prevented virus binding to monocytes nor attenuated the infectivity of any virus progeny that escaped inhibition by SLPI. A polymerase chain reaction (PCR)-based assay for newly generated viral DNA demonstrated that SLPI blocks at or before viral DNA synthesis. Therefore, it most likely inhibits a step of viral infection that occurs after virus binding but before reverse transcription. Taken together, the unique antiviral activity of SLPI, which may be independent of its previously characterized antiprotease activity, appears to reside in disruption of the viral infection process soon after virus binding.

Inhibition of Human Immunodeficiency Virus Type 1 Infectivity by Secretory Leukocyte Protease Inhibitor Occurs Prior to Viral Reverse Transcription

Infection of monocytes with human immunodeficiency virus type 1Ba-L (HIV-1Ba-L ) is significantly inhibited by treatment with the serine protease inhibitor, secretory leukocyte protease inhibitor (SLPI). SLPI does not appear to act on virus directly, but rather the inhibitory activity is most likely due to interaction with the host cell. The current study was initiated to investigate how SLPI interacts with monocytes to inhibit infection. SLPI was found to bind to monocytes with high affinity to a single class of receptor sites (∼7,000 receptors per monocyte, KD = 3.6 nmol/L). The putative SLPI receptor was identified as a surface protein with a molecular weight of 55 ± 5 kD. A well-characterized function of SLPI is inhibition of neutrophil elastase and cathepsin G. However, two SLPI mutants (or muteins) that contain single amino acid substitutions and exhibit greatly reduced protease inhibitory activity still bound to monocytes and retained anti–HIV-1 activity. SLPI consists of two domains, of which the C-terminal domain contains the protease inhibiting region. However, when tested independently, neither domain had potent anti–HIV-1 activity. SLPI binding neither prevented virus binding to monocytes nor attenuated the infectivity of any virus progeny that escaped inhibition by SLPI. A polymerase chain reaction (PCR)-based assay for newly generated viral DNA demonstrated that SLPI blocks at or before viral DNA synthesis. Therefore, it most likely inhibits a step of viral infection that occurs after virus binding but before reverse transcription. Taken together, the unique antiviral activity of SLPI, which may be independent of its previously characterized antiprotease activity, appears to reside in disruption of the viral infection process soon after virus binding.

Secretory leukocyte protease inhibitor (SLPI) in mucosal fluids inhibits HIV-I

Despite the presence of HIV-1 in the oral cavity, transmission of the virus through saliva has not been proven. Consistent with these observations, we recently identified an endogenous 12 kD protein, secretory leukocyte protease inhibitor (SLPI), in saliva which blocks HIV-1 infection in vitro. Whereas other salivary proteins tested were inactive, purified native or recombinant SLPI inhibited HIV-1 infection of human monocytes at 100 ng ml-1. Levels of SLPI quantitated by ELISA in saliva from control and HIV-1 infected individuals exceeded this level, consistent with in vivo antiviral activity. As in saliva, levels of SLPI mRNA determined by Northern hybridization, and protein as assessed by immunohistochemistry in the salivary glands of control and infected populations were comparable. In contrast to adults, oral transmission occurs in infants, possibly due to their lack of fully developed salivary glands. To determine whether the inadequate antiviral protection might be compensated for by maternal sources, we evaluated breast milk samples obtained 6 months postpartum. Levels of SLPI were significantly lower than in saliva and not sufficient to provide antiviral protection in contrast to colostrum samples in which SLPI levels were equivalent to those in saliva and able to inhibit HIV-1 infection when tested in vitro. These data suggest that breast milk may provide transient antiviral activity in the newborn, but that this maternal source of SLPI is of insufficient duration to maintain protection against mucosal transmission of the virus over time. The high functional levels of SLPI in saliva and the low levels in mature breast milk correlate with negligible rates of HIV-1 transmission by saliva and higher rates by breast feeding.

Accuracy of oral specimen testing for human immunodeficiency virus

Antibodies to human immunodeficiency virus (HIV) can be detected in oral fluid with great accuracy, due to technical advances in both the collection of oral samples and assays. Reported sensitivities of 97.2-100% and specificities of 97.7-100% compare well with those of serum-based assays and qualify oral fluid for the screening and diagnosis of HIV infection in both high- and low-risk populations. In addition, oral fluid offers several advantages over serum as a testing medium for HIV, including greater safety, ease of collection, and patient acceptability.

The anti-HIV-1 activity associated with saliva

This review summarizes the data on the anti-human immunodeficiency virus (HIV) activity associated with saliva and the possible routes of oral transmission of HIV. Saliva can be passed from an HIV-infected individual to an uninfected person via sexual or non-sexual activities. The relative risk of HIV transmission through saliva is a subject of continuing concern for dental practitioners. HIV-infected individuals frequently have oral lesions that can cause bleeding and release of the virus into the oral cavity. In addition, viral p24 and HIV-1 RNA were detected in tonsils and adenoids even in asymptomatic seropositive individuals. Nevertheless, the potential HIV-infectivity of saliva is low, although both infectious HIV-1 and HIV DNA have been detected in saliva. This observation has led to the suggestion that saliva may contain factors that inhibit HIV-1 infectivity. At least two anti-HIV activities have been partially characterized: (i) physical entrapment of HIV by high-molecular-weight molecules (e.g., mucins), and (ii) inhibition of viral infection by soluble proteins. Several studies have indicated that, of the salivary proteins evaluated, recombinant secretory leukocyte protease inhibitor (rSLPI) could inhibit HIV-1 infection in macrophages at physiological concentrations. The anti-HIV activity of the serine protease inhibitor rSLPI is most likely due to its interaction with a cell-surface molecule(s) other than the primary HIV-1 receptor, CD4, and may involve (i) inhibition of cell-surface serine protease(s), and/or (ii) interaction with other human-specific co-factors essential for viral entry.

The management of human bite injuries of the hand

Human bites of the hand cause small wounds that are often incorrectly treated as "minor' injuries. We reviewed the management and outcome of patients with human bite or "punch' injuries of the hand. Significant morbidity resulted from late presentation and inadequate initial management. We propose a treatment protocol, in which all patients are immediately referred and admitted to hospital for surgical debridement.

Secretory leukocyte protease inhibitor: a human saliva protein exhibiting anti-human immunodeficiency virus 1 activity in vitro

Infection of adherent primary monocytes with HIV-1Ba-L is significantly suppressed in the presence of human saliva. By reverse transcriptase (RT) levels, saliva, although present for only 1 h during monocyte viral exposure, inhibited HIV-1 infectivity for 3 wk after infection, whereas human plasma and synovial fluid failed to inhibit HIV-1 infectivity. Antiviral activity was identified in the saliva soluble fraction, and to determine the factor(s) responsible, individual saliva proteins were examined. Of those proteins examined, only secretory leukocyte protease inhibitor (SLPI) was found to possess anti-HIV-1 activity at physiological concentrations. SLPI anti-HIV-1 activity was dose dependent, with maximal inhibition at 1-10 micrograms/ml (> 90% inhibition of RT activity). SLPI also partially inhibited HIV-1IIIB infection in proliferating human T cells. SLPI appears to target a host cell-associated molecule, since no interaction with viral proteins could be demonstrated. However, SLPI anti-HIV-1 activity was not due to direct interaction with or downregulation of the CD4 antigen. Partial depletion of SLPI in whole saliva resulted in decreased anti-HIV-1 activity of saliva. These data indicate that SLPI has antiretroviral activity and may contribute to the important antiviral activity of saliva associated with the infrequent oral transmission of HIV-1.