Studies on latent infection of skin and oral mucosa in individuals with recurrent herpes simplex

Herpesviruses and SARS-CoV-2: Viral Association with Oral Inflammatory Diseases

The oral cavity is a niche for diverse microbes, including viruses. Members of the Herpesviridae family, comprised of dsDNA viruses, as well as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), an ssRNA virus, are among the most prevalent viruses infecting the oral cavity, and they exhibit clinical manifestations unique to oral tissues. Viral infection of oral mucosal epithelia triggers an immune response that results in prolonged inflammation. The clinical and systemic disease manifestations of HHV have been researched extensively, and several recent studies have illuminated the relationship between HHV and oral inflammatory diseases. Burgeoning evidence suggests the oral manifestation of SARS-CoV-2 infection includes xerostomia, dysgeusia, periodontal disease, mucositis, and opportunistic viral and bacterial infections, collectively described as oral post-acute sequelae of COVID-19 (PASC). These diverse sequelae could be a result of intensified immune responses initially due to the copious production of proinflammatory cytokines: the so-called "cytokine storm syndrome", facilitating widespread oral and non-oral tissue damage. This review explores the interplay between HHV, SARS-CoV-2, and oral inflammatory diseases such as periodontitis, endodontic disease, and peri-implantitis. Additionally, the review discusses proper diagnostic techniques for identifying viral infection and how viral diagnostics can lead to improved overall patient health.

Molecular analysis of clinical isolates of acyclovir resistant herpes simplex virus

We characterised the antiviral phenotype and genotype of 41 herpes simplex virus (HSV) strains from patients clinically resistant to acyclovir (ACV). Our results confirm recognised mutational sites as being major determinants of thymidine kinase (tk)-associated ACV resistance, in particular insertions and/or deletions at homopolymer stretches of Gs and Cs (59% of all isolates). Previously described amino acid substitutions in functional sites of the tk were also identified (7% of all isolates). In addition, we identified several stop codons in novel locations on the amino acid sequence (7% of all isolates) and amino acid substitutions (15% of all isolates) likely to be directly responsible for conferring resistance to ACV. When there were no mutations detected in the tk gene (12% of all isolates), mutations in the DNA polymerase gene likely to be important in the generation of resistant virus were identified.

HSV-1 antigens and DNA in the corneal explant buttons of patients with non-herpetic or clinically atypical herpetic stromal keratitis

BACKGROUND

Little is known about the role of HSV-1 in keratitis not primarily attributed to herpetic origin. This study therefore aimed to prospectively evaluate the corneal explant buttons of patients with non-herpetic or clinically atypical herpetic stromal keratitis (experimental group: non-HSK) for the presence of HSV-1 antigens and DNA, and to compare the findings with those from individuals with typical herpetic stromal keratitis (positive control group: HSK) or non-inflammatory degenerative keratopathy (negative control group).

METHODS

Corneal buttons derived from 51 patients with HSK, from 72 with non-HSK and from 30 with degenerative keratopathy were prospectively collected and subjected to immunohistochemical analysis for HSV-1 antigens and to HSV-1 DNA amplification.

RESULTS

In corneal buttons derived from patients with non-HSK, viral antigens were detected immunohistochemically in 8/72 cases and DNA amplified in 16/72. Corresponding values for the HSK group were 16/51 and 11/51. Taking viral antigen and DNA findings together, HSV-1 was detected in 18/72 (25%) patients with non-HSK and in 19/51 (37%) with HSK (p=0.2), but in only 2/30 (6%) individuals with non-inflammatory degenerative keratopathy.

CONCLUSION

Since the detection frequencies for HSV-1 antigens and DNA were comparable in the HSK and non-HSK groups, Herpes may play an underestimated and as yet undefined role in non-herpetic and clinically atypical herpetic stromal keratitis, either as a primary trigger of the disease or as a secondary contributor to it. In this category of individuals, early anti-herpetic therapy should be considered if patients do not respond in the expected manner to treatment for non-herpetic stromal keratitis.

Reactivation of latent herpes simplex virus-1 (HSV) from mouse footpad cells demonstrated by in situ hybridization

HSV-1 specific RNA sequences became detectable by in situ hybridization 5-6 days after culture of footpads (FP) explanted from latently infected mice. HSV-specific RNA first appeared in basal cells of hair follicles and cells of the hair root sheath, in epithelial cells of sebaceous glands and in cells within the epidermis. When first detected graining was light and usually present over individual cells, subsequently graining became heavy and present over large groups of cells. HSV reactivation from latency could be demonstrated in individual cells and therefore identified those cells in which the virus has been latent. The heavy graining over clumps of cells characteristic of a lytic infection was seen at later times after explantation; we infer that the infection had spread progressively from the initial foci of reactivation from latency.

[Herpetic brain stem encephalitis: report of an autopsied case with immunohistochemical and electron microscopy studies]

A post-mortem examined case of herpetic brainstem encephalitis is presented. Clinically, the patient had cephalalgia followed by ataxia, drowsiness and multiple palsies of some cranial nerves, developing into death in eight days. The pathologic examination of the brain showed necrotizing encephalitis in multiple foci limited to the brainstem, more distinctly in the pons and medulla oblongata. The technique of immunoperoxidase revealed rare glial cells with intranuclear immunoreactivity for herpes antigen. Rare viral particles with the morphological characteristics of the herpesvirus were identified in the nuclei of neurons in 10% formol fixed material. This is the second reported case of herpetic brainstem encephalitis confirmed by post-mortem examination. The pathway used by the virus to reach the central nervous system and its posterior dissemination to the oral cavity, the orbitofrontal region and the temporal lobes as well as to the brainstem, after a period of latency and reactivation, are discussed.

Herpes simplex virus type 2 establishes latency in the mouse footpad and in the sensory ganglia

Three mouse strains as well as wt and 7 ts mutants of herpes simplex virus (HSV) type 2 (strain HG52) have been used to investigate latency. The mice were inoculated in the right rear footpad. Virus reactivation following explanation and culture of the dorsal root ganglia and the footpad was scored. The results show that: HSV-2 can be maintained in the mouse footpad in a state indistinguishable from latency; virus gene functions necessary for latency can be identified by the use of ts mutants; and mouse strains differ in their ability to support latent infection. An infectious center assay was used to quantitate virus reactivation from dissociated dorsal root ganglia. HSV-1 strain 17 wt spread after inoculation at doses of greater than or equal to 5.0 X 10(5) plaque-forming units (pfu), producing latency also in contralateral ganglia but with lower efficiency.

A proposed biologic cure for recurrent genital herpes simplex through injection of neurolytic agents into cutaneous sensory nerves

It may be possible to eliminate Herpes simplex virus (HSV) from the skin of patients with chronic recurrent genital infections through destruction of the cutaneous sensory nerves of the genitals by injecting absolute alcohol into the affected areas. In so doing the latency of the virus in the sensory ganglia may be influenced, the immediate source of reinfection suppressed, and reactivation of HSV inhibited in the skin.

Persistence of herpes simplex virus (HSV) infection in ganglia and peripheral tissues of guinea pigs

HSV infections in guinea pigs are shown to persist independently in dorsal root ganglia and skin at the site of initial inoculation. The same may also hold for ganglia and vagina after genital infections. Evidence is presented that the state of persistent virus might be different in ganglia and peripheral tissue.

Persistence in herpes simplex virus infections

Diseases of man caused by the virus of herpes simplex fall into two broad categories. The primary disease occurs only once in any individual's life and is caused by transmission of virus from an already infected human. Thereafter, the individual may be subject to recurrent herpetic disease, the manifestations of which are different from the primary disease. Recurrent disease varies in severity from trivial, to incapacitating and frankly lethal (as in diseases resulting from the virus's neurotropic and oncogenic properties). The source of the virus in recurrent herpetic disease has never been conclusively resolved, but is almost certainly endogenous to the patient. Theories, case reports and experiments exist to show that endogenous virus may, in periods of clinical quiescence, be latent (or persistent) at the site of the recurrent lesions itself, or more remotely in nerve tissues related to the site of recurrence.

Recurrent herpes in the rabbit and man

Herpesvirus was present in secretory glands and frequently in tears of rabbits with recurrent herpetic keratitis even in the absence of corneal lesions. In normal people, herpesvirus could be cultured from saliva and tears. Chronic virus multiplication in structures such as the lacrimal and salivary glands, rather than latency, may cause recurrent herpetic disease.