Beginning with the Surgeon General's report on oral health in 2000, the mouth has been identified as a portal of entry for microbial infections, including those caused by bacteria, viruses, and fungi. Diseases caused by these microorganisms include dental caries, periodontal diseases, herpes labialis, and candidiasis. In addition, viruses, such as human immunodeficiency virus (HIV) and human papillomavirus (HPV) may enter the oral cavity. Although acquisition or transmission of viral infections is multifactorial and complex, involving interplay among genetic, environmental, and behavioral factors, the mouth may provide a protective barrier to some key viral infections. Dentists may not be trained on how to talk to patients about risks and the acquisition of these oral viral infections through oral sex.
Gigi Meinecke, BSN, DMD, is an expert consultant on oral pathophysiology, which includes those of viral etiology. Currently, Dr. Meinecke is a faculty member of the University of Maryland School of Dentistry in the Department of Diagnostic Sciences and Pathology and has a private practice in Potomac, Maryland. Margaret Scarlett, DMD, Clinical Editor, Dentistry and Oral Health, spoke with Dr. Meinecke about the evolving science of the mouth as a protective barrier for oral viral infections.
Medscape: What do we know about the mouth as a protective barrier for viral infections?
Gigi Meinecke, BSN, DMD: We know from various studies that HIV is not readily transmitted through oral fluids.Scientists have found that a salivary component, called salivary leukocyte protease inhibitor (SLPI), is a major protective factor that inhibits transmission of HIV in the mouth.[3,4]
However, the same mechanism by which SLPI activates Langerhans cells to inhibit transmission of HIV produces a protective action in inhibiting HPV infection in the mouth. SLPI binds to annexin 2 (ANXA2) on the surface of human macrophages, which disrupts the binding of the surface phosphatidylserine of the HIV membrane to this receptor. Furthermore, Langerhans cells express ANXA2 and are the initial cellular targets of HIV and a major route of viral dissemination. By the same mechanism, HPV interacts with Langerhans cells in the suprabasal mucosa.
In fact, research is now being conducted to investigate optimal methods to up-regulate production of SLPI in the oral cavity to inhibit acquisition of both HIV and HPV in the mouth.[5,6,7] This work is derived from our understanding of the binding of SLPI with ANXA2. ANXA2 has been implicated in the acquisition of cytomegalovirus and respiratory syncytial virus.
Medscape: What do we know about SLPI?
Dr. Meinecke: Our understanding of SLPI is evolving, with knowledge emerging about the impact of SLPI levels that influence the potential for viral infection. For example, SLPI levels are lower in people with herpes simplex virus (HSV) infection. About 90% of the population has a history of HSV infection, so this is a priority issue for research.Persons with HSV infection are at greater risk for acquisition of HIV and HPV infection in the mouth. In addition, SLPI is found in lower than normal levels in people with pulmonary disease and in those with lower genital tract infections. We are learning more about SLPI every day.
SLPI is a hormonally regulated protein produced by many cell types. A key research issue is the innate property of SLPI as a natural ligand for ANXA2. Since its original classification as a protease inhibitor, we have identified many properties of SLPI that can protect the host from infection.
Medscape: How does SLPI work?
Dr. Meinecke: Two mediators have been found to be helpful to adaptive immunity. This type of immunity is phylogenetically "younger" than innate immunity. Scientists have found that the antileukocyte protease factors (known as alarm antiproteases) facilitate the communication between innate and adaptive immunity through SLPI, along with another compound found in submandibular fluid (called elafin) with which they interact. It appears that these "alarm antiproteases" can communicate with adaptive immunity, essentially telling that system whether an epitope is worthy of mounting an adaptive response.
Elafin (elastase-specific inhibitor) has properties that are antibacterial, antifungal, and anti-inflammatory, which are involved in tissue repair in the mouth. Salivary factors, such as lactoferrin, statins and lysozymes, hinder oral infection caused by some invasive bacteria. Both SLPI and elafin are becoming important in understanding oral immunity because of their joint potential to reduce the risk of acquiring both HIV and HPV in the oral cavity. Investigations are continuing as to whether these compounds could mitigate the potential of HPV to develop into oral cancers.
Medscape: So the bottom line -- are HPV and HIV transmitted through oral sex?
Dr. Meinecke: Yes, although the exact risk is not known. We know more about HPV in other mucosal surfaces in the body. For example, intracervical cancer is 5 times more likely to develop in HPV-infected women. Similar risks for anal cancer occur for men who have sex with men with multiple partners. We don't know everything about the natural history of oral HPV, but we do know that at least 80% of sexually active adults have at least 1 type of HPV during their lifetime. Having more than 6 oral sex partners over a lifetime carries an 8 times greater risk of acquiring HPV-related head or neck cancer than having fewer than 6 partners.
Repeated unprotected oral sex and multiple oral sex partners increase the risk for acquisition of oral HPV. Trauma can increase risk as well because it can facilitate entry of HPV beyond the oral mucosa, which is usually a pretty good physical barrier to viral entry.
Medscape: How can dentists talk to patients about oral sex?
Dr. Meinecke: This is a tough issue for dentists, and some patients are caught off-guard or become uncomfortable with a conversation about oral sex and transmission of oral viruses. Dentists should be trained about leading this conversation in school or in continuing education courses.
One way to broach this topic is to tell the patient that you are looking for oral cancer when you perform a head and neck examination. Women, especially when they go to have a pap smear, know that their clinician doesn't look in their mouth -- the dentist may be the only one doing so. The subject of oral sex can be introduced in a broad, nonspecific way, by beginning to discuss oral viral infections, such as HPV. Given the changing demographics of oral cancer, we should educate our patients and explain that any man over the age of 40 years, even one without a history of alcohol or tobacco abuse, is at risk.
With oral cancer affecting younger people, dentists need to become more comfortable discussing this disease with their patients, and its associations with oral sex. When all dentists collectively decide to practice this way, it will become "normal” and countless lives will be saved. Most oral pathology continuing education courses discuss the identification of lesions and the pathophysiology, completely losing sight of the crucial aspect of discussing this sensitive subject with the patients who entrust us with their care. If, as a group, we want to have an impact on this fatal disease, we need to be able to discuss oral risk factors with our patients to reduce these risks.
Rather than asking questions of a sensitive nature, the dentist can begin the conversation by explaining why he or she does a head and neck evaluation, which includes examining the tongue and mucosal tissues. That can provide a lead in to statistics on how many people are infected by HSV and HPV and how sexual behavior is a factor in those statistics.
Medscape: What should the dentists do about oral warts caused by low-risk types of HPV?
Dr. Meinecke: HPV is common as either oral warts or condyloma. These are easy to remove and send for a biopsy. When removing these lesions, it is a good time to talk to the patient about risk, as well as the importance of oral hygiene.
Medscape: Vaccines against HPV are available. Should the dentist refer patients to medical colleagues to administer the HPV vaccine to prevent oral cancer?
Dr. Meinecke: The HPV vaccine is recommended for adolescent -- boys and girls, aged 12-14 years.Many pediatricians are already routinely vaccinating adolescents against HPV. The main reason is to prevent cervical cancer, the second most common cancer affecting women worldwide. The HPV vaccine prevents this type of cancer, and it also prevents penile warts in men.
Vaccine manufacturers currently do not demonstrate interest in seeking US Food and Drug Administration approval for marketing HPV vaccines against oral cancer. Perhaps, the National Institutes of Health will undertake a proof of concept study of the HPV vaccine to reduce the risk for oral cancer.
Worldwide, oral cancer is not in the top 5 cancers. So, from the pharmaceutical industry's perspective, the case for market approval for an HPV vaccine to prevent oral cancer doesn't make economic sense.
Medscape: What other factors influence the effectiveness of the mouth as a barrier to viral infection?
Dr. Meinecke: Any time that you have a disease or infection process that affects host resistance, you have lowered immunity to any kind of oral viral infection. There are too many of these processes to list every one. However, chronic obstructive pulmonary disease, uncontrolled diabetes, and other chronic infections are some examples of diseases that can lower immunity.
Medscape: Thank you for discussing the mouth as a barrier for the acquisition of viral infections, such as HPV and HIV.
Medscape Dental & Oral Health © 2011 WebMD, LLC
Cite this: Talking to Patients About Oral Sex Risks - Medscape - Sep 15, 2011.