Role of Viruses in Periodontal Diseases

50-Mark Postgraduate Theory Examination Answer

INTRODUCTION

"Enhanced bacterial pathogenicity may result from the reactivation of common herpesviruses and their intimate topographic relationship with putative periodontopathogens within diseased periodontal pockets."

• Martinez, Kuraji, Kumar & Hernandez-Kapila (Carranza's Clinical Periodontology, 13th ed., Chapter 27)

I. THE ORAL VIROME AND PERIODONTAL ECOLOGY

II. CLASSIFICATION OF VIRUSES RELEVANT TO PERIODONTAL DISEASES

A. Eukaryotic Viruses

B. Prokaryotic Viruses (Bacteriophages)

• Modulating bacterial composition and fitness
• Mediating horizontal gene transfer (including antibiotic resistance genes)
• Influencing biofilm formation, reorganization, and destruction

III. HERPESVIRUSES AS MAJOR PERIODONTAL PATHOGENS

A. Landmark Conceptual Framework - The Slots Hypothesis

• Proposed that herpesviruses (CMV and EBV) are the major pathogenic determinant of severe periodontitis.
• Four billion individuals worldwide have a history of periodontitis; periodontal herpesviruses that disseminate systemically may represent a major link to ≥57 systemic diseases.
• Argued that current treatment focused exclusively on bacterial biofilm "will require revision."

• CMV and EBV are associated with aggressive and chronic periodontitis.
• CMV and Aggregatibacter actinomycetemcomitans (Aa)/P. gingivalis exercise synergistic pathogenicity in localized aggressive periodontitis.
• Proposed a two-way interaction: herpesviruses promote bacterial upgrowth; bacterial factors reactivate latent herpesviruses.

• Demonstrated cytopathic effects of CMV on gingival fibroblasts over 6 days (a sequential morphological progression from baseline through cellular destruction).

• MicroRNAs elaborated by periodontal tissue cells and herpesviruses play important roles in periodontitis pathogenesis; salivary microRNAs hold diagnostic potential.

IV. EPSTEIN-BARR VIRUS (EBV/HHV-4) IN PERIODONTITIS

Microbiology

Detection in Periodontal Tissues

• EBV DNA has been detected in subgingival plaque from deepened pockets (≥5 mm) at 66% detection rate compared to 48% in shallow pockets and 45% in healthy pockets in Japanese patients with chronic periodontitis (Martinez et al., p.406).
• In the same cohort, 44% of deep pockets were co-infected with EBV and P. gingivalis, versus only 13-14% in healthy or shallow pockets.
• Elevated EBV levels in gingival crevicular fluid (GCF) have been associated with the severity of periodontitis.

Mechanism of EBV-Mediated Periodontal Destruction

1. Immunosuppression of local host defenses: EBV-infected B cells and monocytes exhibit impaired antimicrobial function.
2. Cytokine dysregulation: EBV expresses proteins during lytic and latent cycles that modulate innate and adaptive immune responses, increasing pro-inflammatory cytokine expression to promote osteoclastogenesis.
3. Reactivation by bacterial metabolites: Butyric acid (a short-chain fatty acid produced by P. gingivalis and F. nucleatum) is a potent lytic inducer of EBV via activation of the BZLF-1 transcription factor - the key transactivator switching EBV from latency to lytic replication. This creates a vicious cycle where periodontopathogens create an environment facilitating EBV lytic replication, and EBV in turn amplifies disease (Martinez et al., Fig. 27.6).
4. Tissue repair impairment: EBV infects fibroblasts, affecting tissue turnover and periodontal tissue repair.

Hairy Leukoplakia

V. HUMAN CYTOMEGALOVIRUS (HCMV/HHV-5) IN PERIODONTITIS

Microbiology

Detection in Periodontal Tissues

• CMV is detected at higher frequencies in periodontally diseased sites compared to healthy sites.
• In Sudanese adolescents with aggressive periodontitis, there was a significant association between A. actinomycetemcomitans, P. gingivalis, and CMV (OR = 39.1 for Aa + CMV dual infection, 95% CI 2.0-754.6) (Martinez et al., p.407).
• In Jamaican adolescents, similar strong associations for aggressive periodontitis (OR = 51.4, 95% CI 5.4-486.5) were reported (Martinez et al., p.407).
• CMV isolation in advanced/necrotic periodontal lesions is often accompanied by gram-negative periodontopathogens (Treponema forsythia, Porphyromonas gingivalis, T. denticola).

Mechanism of CMV-Mediated Periodontal Destruction

1. Lytic CPE: CMV causes rounding and enlargement of gingival fibroblasts and epithelial cells, with progressive cellular destruction visible from Day 1 to Day 6 post-infection (Martinez et al., Fig. 27.2, demonstrating temporal progression of CPE on gingival fibroblasts).
2. Immune evasion: CMV immune evasion mechanisms favor local immunosuppression, facilitating bacterial growth in periodontal lesions and impairing CD4+ and CD8+ T-cell responses.
3. Proinflammatory cytokine expression: Lytic proteins increase cytokine production (IL-6, IL-8, TNF-α) that overlap precisely with the cytokine profile in active periodontitis, driving bone destruction through osteoclastogenesis.
4. Bacterial co-infection facilitation: CMV alters host cell surfaces, aiding the colonization and invasion of periodontopathogens.

Oral Manifestations in Immunocompromised Patients

VI. HERPES SIMPLEX VIRUS (HSV) AND VARICELLA-ZOSTER VIRUS (VZV)

HSV-1 and Periodontal Disease

• Primary infection (Herpetic Gingivostomatitis): The primary oral infection with HSV-1 produces herpetic gingivostomatitis - characterized by fever, vesicular eruptions of oral mucosa, bleeding, highly painful gingival involvement, and regional lymphadenopathy. This is the most common cause of acute ulcerative gingivitis in children (Samaranayake, p.176-177).
• Latency occurs in the trigeminal ganglion; reactivation produces herpes labialis (cold sores) - triggered by menstruation, stress, sunlight, or local trauma.
• HSV is present in the NUG-like lesions of HIV-infected patients and contributes to the pathogenesis of necrotizing periodontal diseases.

VZV (HHV-3)

VII. HERPESVIRUS-BACTERIA SYNERGISM: THE CORE PATHOGENIC MODEL

Mechanisms of Synergism

1. Herpesviruses promoting bacterial upgrowth:
   • Impair PMN and macrophage antimicrobial function
   • Disrupt cytokine networks (IL-1β, TNF-α, IL-6, IL-8) that normally coordinate antimicrobial defense
   • Suppress cellular immunity against bacterial pathogens
   • Alter periodontal cell surfaces to predispose for bacterial adherence and invasion
2. Bacterial factors reactivating latent herpesviruses:
   • Butyric acid from P. gingivalis and F. nucleatum activates BZLF-1, switching EBV to lytic cycle (Martinez et al., p.406)
   • Bacterial-induced gingivitis may facilitate herpesvirus colonization of the periodontium by creating microbial niches with impaired local immunity
3. Clinical correlation:
   • CMV + Aa synergy: Localized aggressive periodontitis
   • CMV + EBV + P. gingivalis synergy: Adult chronic periodontitis
   • Co-infection with EBV and CMV found more frequently in deep periodontal pockets and associated with bacterial periodontopathogens (Martinez et al., p.406)

Proposed Sequence of Events (Slots Model)

1. Bacterial gingivitis permits herpesvirus colonization
2. Herpesvirus infection impairs local host defenses
3. Overgrowth of periodontopathic bacteria
4. Dysregulated inflammatory-immune response → tissue destruction
5. Deepened pockets create anaerobic niche → more herpesvirus replication and bacterial growth

VIII. VIRUSES IN SPECIFIC PERIODONTAL CONDITIONS

A. Necrotizing Ulcerative Periodontitis (NUP) and Necrotizing Ulcerative Gingivitis (NUG)

1. Bacterial zone (surface biofilm)
2. Neutrophil-rich zone
3. Necrotic zone
4. Spirochetal infiltration zone

• Herpeslike viruses in 56.5% of NUP lesions
• Opportunistic yeasts in 65.6% of NUP lesions
• Mixed microbial flora with spirochetes in 87.5% of specimens

• NUP in HIV-positive patients can cause >10 mm bone loss in 3-6 months (Winkler et al.)
• NUP diagnosis is associated with CD4+ counts below 200 cells/mm³ (20.8 times more likely than HIV-positive patients without NUP)
• NUP may serve as a clinical predictor and marker for AIDS diagnosis and HIV status in undiagnosed patients (NUP.pdf; Martinez et al., p.412)

B. Linear Gingival Erythema (LGE)

C. Kaposi's Sarcoma of the Gingiva

IX. MECHANISMS BY WHICH VIRUSES CONTRIBUTE TO PERIODONTAL DESTRUCTION

1. Direct Cytopathic Effects (CPE)

• CMV: Cell rounding and enlargement (Martinez et al., Table 27.1)
• HSV: Intranuclear inclusion bodies
• EBV: Intranuclear inclusion bodies in epithelium and B lymphocytes

2. Immunosuppression of Host Defense

• Herpesviruses suppress PMN function, macrophage activity, and lymphocyte responses
• In periodontitis lesions, viruses may explain the impaired CD8+ cytotoxic T-cell response (Lindhe 5th ed., p.301: "CD8-positive cells are found in smaller numbers in gingivitis/periodontitis lesions than CD4-positive cells... it may be anticipated that viruses and other invasive microorganisms do not constitute a major part of the antigens in periodontitis")
• This relative paucity of CD8+ cells in periodontal lesions can be exploited by herpesvirus reactivation

3. Cytokine Dysregulation

• These cytokines are simultaneously the key mediators of periodontal bone destruction (Lindhe 5th ed., p.296)
• RANKL/OPG imbalance driven by viral-triggered cytokine release promotes osteoclast differentiation and alveolar bone resorption

4. Impairment of Tissue Repair

5. MicroRNA-Mediated Pathogenesis (Emerging Concept)

• Both periodontal tissue cells and herpesviruses elaborate microRNAs
• Aberrant microRNA expression has been associated with several systemic diseases
• Herpesvirus microRNAs can silence host immune effector genes
• Salivary microRNAs offer diagnostic potential as biomarkers of disease activity
• MicroRNA technology represents a promising future preventive and therapeutic possibility in periodontics

X. HIV AND PERIODONTAL DISEASE - THE VIRAL PARADIGM MODEL

Periodontal Manifestations of HIV

1. Linear Gingival Erythema - earliest marker
2. NUG - acute necrotizing phase
3. NUP - destructive with bone and attachment loss (specific marker for CD4 <200 cells/mm³)
4. Necrotizing Ulcerative Stomatitis (NUS) - extension into vestibular and palatal soft tissues
5. Kaposi's Sarcoma (HHV-8 mediated)
6. Oral Hairy Leukoplakia (EBV mediated)
7. Increased frequency of herpetic lesions and aphthous stomatitis

HAART and Periodontal Disease

XI. DIAGNOSIS OF VIRAL PERIODONTAL INFECTIONS

Clinical Methods

• Cytopathic effects in cell cultures (gold standard for CMV)
• Intranuclear inclusion bodies (HSV, EBV)
• Tzanck smear: multinucleated giant cells (VZV, HSV)
• Immunofluorescence and neutralization tests

Molecular Methods (Current Standard)

• Real-time quantitative PCR: Preferred for clinical samples (GCF, subgingival plaque, gingival biopsy, saliva) - distinguishes latent from active infection
• Next-Generation Sequencing (NGS): Allows metagenomic analysis of the entire viral community; detects novel and uncultivable viruses
• Enzyme immunoassay (EIA): For viral antigen detection
• ELISA + Western Blot: For HIV (antibody to p24, gp41, gp120)

Samples for Viral Identification in Periodontics

XII. TREATMENT OF VIRUS-ASSOCIATED PERIODONTAL DISEASES

Anti-herpesviral Therapy

• Acyclovir (200-800 mg, 5 times daily for ≥10 days): First-line for HSV and VZV infections. Maintenance therapy (200 mg, 2-5 times daily) may prevent recurrence.
• Ganciclovir (IV): Treatment of choice for oral CMV ulcerations; typically resolves in 14 days. HIV-associated CMV may require longer duration and higher dosage.
• Foscarnet: For ganciclovir-resistant CMV strains
• Valacyclovir: For resistant viral strains

Periodontal Management

• Debridement, scaling and root planing, local antimicrobial irrigation (chlorhexidine gluconate 0.12% or povidone-iodine)
• Systemic antibiotics (metronidazole preferred for NUG/NUP due to narrow spectrum minimizing candidal superinfection)
• Prophylactic antifungals if antibiotics are prescribed (immunocompromised patients)
• Recall at 2-3 month intervals for HIV-positive patients

Slots' Proposed Anti-Infective Model

Emerging Therapy: Bacteriophage Therapy

XIII. VIRUSES AND SYSTEMIC IMPLICATIONS OF PERIODONTITIS

SUMMARY TABLE

CONCLUSION

KEY REFERENCES

1. Martinez AG, Kuraji R, Kumar PS, Hernandez-Kapila YL (2023). "Pathology and Management of Periodontal Problems Associated With Viral Infection, Including HIV, COVID, and Others." Carranza's Clinical Periodontology, 13th ed., Chapter 27.
2. Chen C, Feng P, Slots J (2020). "Herpesvirus-bacteria synergistic interaction in periodontitis." Periodontology 2000, 82:93-130. [PMID: 31850623]
3. Slots J, Slots H (2019). "Periodontal herpesvirus morbidity and treatment." Periodontology 2000, 79:26-51. [PMID: 30892761]
4. Naqvi AR, Slots J (2021). "Human and herpesvirus microRNAs in periodontal disease." Periodontology 2000, 87:59-80. [PMID: 34463985]
5. Contreras A, Mardirossian A, Slots J (2001). "Herpesviruses in HIV-periodontitis." J Clin Periodontol, 28:96-102.
6. Contreras A, Falkler WA, Enwonwu CO et al. (1997). "Human Herpesviridae in acute necrotizing ulcerative gingivitis in children in Nigeria." Oral Microbiol Immunol, 12:259-265.
7. Cobb CM, Ferguson BL, Keselyak NT et al. (2003). "A TEM/SEM study of the microbial plaque overlying necrotic gingival papillae of HIV-seropositive NUP." J Periodontal Res, 38:147.
8. Samaranayake LP (2012). "Viruses of Relevance to Dentistry." Essential Microbiology for Dentistry, Chapter 21 & 33.
9. Lindhe J, Berglundh T, Kinane DF (2008). Clinical Periodontology and Implant Dentistry, 5th ed., Chapter 11 (Pathogenesis of Periodontitis).
10. Kinane DF, Berglundh T, Lindhe J (2008). Host-Parasite Interactions. Lindhe's Clinical Periodontology, 5th ed., pp. 285-306.