Treatment of viral infections with 5-aminolevulinic acid and light

Molluscum contagiosum: recent advances in pathogenic mechanisms, and new therapies

Two poxviruses, Molluscum contagiosum virus (MCV) and Variola virus are specific to humans. MCV is present worldwide and is directly passed by direct skin to skin contact to produce cutaneous and, rarely, mucosal lesions. It occurs predominantly in preadolescent children, sexually active adults, participants in sports with skin to skin contact, and in individuals with impaired cellular immunity. MCV characteristically proliferates within the follicular epithelium, and with routine fixation produces an area of retraction artifact separating layers 1 to 3 of CD34+ stromal cells that immediately surround the follicle from the surrounding dermis. This feature may be obscured when the lesions are inflamed, usually after rupture into the surrounding dermis. MCV is a cytoplasmically replicating virus. MCV-infected cells grow in size, while internal organelles are dislocated and eventually obliterated by a large intracytoplasmic inclusion. Rupture and discharge of the virus-packed cells occurs in a process similar to membrane debris and MCV accumulate in the crater-like ostium; MCV infection is spread by contact with infectious debris. In HIV-1-positive patients the histologic features, as well as the clinical features, may be atypical in patients with MCV infections. Not only are the lesions often large, but they may be verrucous and markedly hyperkeratotic. Recent sequencing of the MCV genome has increased our understanding and investigations into its mechanisms for avoiding host defense mechanisms. These include regions which encode for homologues of cellular chemokines and chemokine-binding proteins, a homolog of MHC1 and a viral FLICE-like inhibitory protein. Treatment, until recently, has depended upon tissue destruction including curettage, cryotherapy, CO(2) laser, electrodesiccation, trichloracetic acid and cantharadin. Recently, topical immune modulators have been used with some success. Understanding of the MCV genome is providing the basis for the development of drugs for therapy and prevention of MCV infections.

Non-oncologic indications for ALA-PDT

Topical photodynamic therapy with 5-aminolevulinic acid (ALA-PDT) is a well-established treatment regimen for superficial epithelial skin tumours, but it is evident that inflammatory diseases of the skin and virus-induced lesions can also profit from PDT. Depending on the light dose applied, either cytotoxic effects resulting in tumour destruction or immunomodulatory effects resulting in improvement of inflammatory conditions occur. Patients with localized scleroderma that had been unresponsive to various treatments, including PUVA or bath-PUVA therapy, respond very well to topical ALA-PDT performed repeatedly. In contrast to PUVA therapy, no carcinogenic potential is being discussed for PDT. Also, HPV-induced skin lesions might provide a possible indication for topical ALA-PDT. The rapidly proliferating cells in viral acanthomas accumulate ALA-induced protoporphyrin IX (PPIX) selectively when compared to the surrounding non-infected cells. The efficacy of topical ALA-PDT in the treatment of recalcitrant foot and hand warts has been shown in a placebo-controlled, randomized, double-blind trial. Furthermore, case reports describe a good response of other virus-induced diseases, for example condylomata acuminata and epidermodysplasia verruciformis, to topical PDT with ALA. However, controlled clinical trials are still needed to demonstrate more fully the effectiveness of PDT for inflammatory skin diseases.

Topical 5-aminolevulinic acid and photodynamic therapy in dermatology: a minireview

Photodynamic therapy (PDT) is a treatment modality using a photosensitizer, light and oxygen to cause photochemically induced selective cell death. When exposed to light with the proper wavelength, the topically applied photosensitizer or photosensitizer precursor can activate a biomolecule through electron transfer to yield free radicals or produce singlet oxygen from energy transferred from the excited sensitizer to molecular oxygen. The tissue damage is the result of the activation of reactive singlet oxygen or free radical production. Photodynamic therapy with topical application of 5-aminolevulinic acid (ALA) is a new technique and although it remains largely experimental, it has potential application for treatment of malignant skin tumors, various precancerous and selected benign skin diseases. This technique yields not only a high percentage of good therapeutic results but also excellent cosmetic outcome. This paper reviews the recently published data on clinical ALA-based PDT in dermatology.

Photodynamic therapy with topical delta-aminolaevulinic acid for the treatment of plantar warts

Treatments currently employed for plantar warts are often painful (electrosurgery, cryotherapy) and not always effective (keratolytic agents). In this paper we investigate the effect of photodynamic therapy (PDT) with topical delta-aminolaevulinic acid (ALA) on plantar warts. In order to remove the superficial hyperkeratotic layer of the warts an ointment containing 10% urea and 10% salicylic acid was applied for 7 days. After gentle curettage, a cream containing 20% ALA was applied under an occlusive dressing for 5 h on 64 warts, while 57 warts (controls) received only the vehicle. Both the ALA-treated warts and the controls were irradiated using a visible light lamp (with a range of 400-700 nm, peaking at 630 nm). The light dose was 50 J/cm(2). Patients were followed-up for 22 months. Two months after the last irradiation session 48 (75.0%) out of 64 ALA-PDT treated warts had resolved. By contrast only 13 (22.8%) of the 57 control warts had done so. During the treatment a few patients complained of a mild burning sensation. The absorption of ALA by the verrucous tissue was demonstrated by in vivo fluorescence spectroscopy. This study shows that topical ALA-PDT can be an alternative treatment for plantar warts. Further studies will be necessary in order to optimize the concentration of ALA and duration of treatment.

Aminolevulinic acid: pharmacological profile and clinical indication

The role of aminolevulinic acid hydrochloride (ALA) in photodynamic therapy (PDT) of in situ neoplasias and tumours of epithelial tumours is steadily increasing and it has been shown to be the drug with most clinical use in PDT. In dermatology, topical PDT with ALA is already postulated to be the treatment of choice for actinic keratoses and superficial basal cell carcinomas. In gastroenterology, pulmonology, uro- and nephrology, neurology and gynaecology ALA has an important role as a photosensitiser not only in the diagnosis of neoplastic tissue but as therapy; first experiences have been made with PDT in these organs. Besides the therapeutic efficacy of this technique, the fluorescence of ALA-induced porphyrins can be effectively used to detect and delineate epithelial and endothelial neoplasms. In dermatology, other indications for ALA-treatment are non-tumoural applications, especially psoriasis, viral-induced diseases, or acne vulgaris. ALA is an effective compound in the diagnosis or therapy of various epithelial and endothelial neoplastic lesions.

Migraine and beyond: cardiovascular therapeutic potential for CGRP modulators

CGRP is a potent vasodilator that has been shown to have a physiological and/or pathological role in neurogenic inflammation, headaches including migraine, thermal injury, circulatory shock, pregnancy and menopause, hypertension and heart failure and is known to be cardioprotective. CGRP is also a positive inotrope and increases heart rate. Clinical trials have shown beneficial effects of the vasodilatory action of CGRP in hypertension, angina, heart failure, Raynaud's disease and venous stasis ulcers. However, the clinical potential of CGRP is limited as it has to be given by infusion and is quickly broken down. Oral long acting CGRP-mimetics may have potential in disorders in which CGRP has been shown to be beneficial. CGRP-mimetics include capsaicin/vanilloid receptor agonists and gene transfer of an adenoviral vector that encodes prepro-CGRP. CGRP inhibitors have therapeutic potential in conditions in which excessive CGRP-mediated vasodilatation is present; neurogenic inflammation, migraine and other headaches, thermal injury, circulatory shock and flushing in menopause. CGRP inhibitors include capsaicin, antagonists at capsaicin/vanilloid receptors, civamide, CGRP receptor antagonists and 5-HT1D-receptor agonists. Drugs that are 5-HT1D-receptor agonists, the 'triptans' are already commonly used in migraine and the first small molecule CGRP antagonist, BIBN4096BS, is under clinical investigation for the treatment of migraine.

An overview of poxviruses

The poxvirus family is a diverse and interesting group of viruses that affect both humans and animals. Poxviruses are epitheliotropic and therefore are of interest to the dermatologist. The genera of poxviruses known to affect humans are Orthopoxvirus, Parapoxvirus, Molluscipoxvirus, and Yatapoxvirus. The different poxviruses are reviewed, including their history, incidence, clinical presentation, and treatment.

Photodynamic therapy for in situ squamous cell carcinoma on chronic radiation dermatitis after photosensitization with 5-aminolaevulinic acid

The accessibility of the skin to light treatment, as well as the developments made by dermatologists in photodynamic therapy (PDT), creates an exciting apportunity to include it as a part of our standard therapeutic armamentarium. We report a 63-year-old man with an in situ squamous cell carcinoma located on a chronic radiodermitis area in a finger, treated successfully with PDT. PDT appears to be a viable alternative to conventional therapy for in situ squamous cell carcinoma as well as for other superficial tumours of the skin.

Photodynamic therapy with 5-aminolaevulinic acid or placebo for recalcitrant foot and hand warts: randomised double-blind trial

BACKGROUND

Photodynamic therapy (PDT) with topical 5-aminolaevulinic acid (ALA) followed by irradiation with incoherent light (ALA-PDT) for recalcitrant warts have had beneficial results. Therefore, we undertook a randomised, parallel, double-blind clinical trial of ALA-PDT versus placeboPDT for recalcitrant foot and hand warts.

METHODS

Recalcitrant foot and hand warts were randomly assigned to six repetitive ALA-PDT or placebo-PDT interventions combined with standard treatment encompassing paring followed by a keratolytic (Verucid). Standardised photographs of each wart were taken before, during (week 7) and after treatment (weeks 14 and 18). The area of each wart compared with entry area was the primary outcome variable, measured from photographs by an evaluator unaware of treatment allocation for intervention. Pain intensity immediately and 24 h after each intervention was assessed by a five-point scale.

FINDINGS

A total of 232 foot and hand warts in 45 patients were entered into the trial: 117 warts were allocated to ALA-PDT and 115 warts to placebo-PDT. In week 14, the median relative reduction in wart area was 98% in the ALA-PDT group (interquartile range 100%, 55%) versus 52% (100%, 0) in the placebo group (p=0.0006). In week 18, the median relative reduction in wart area was 100% in the ALA-PDT group (100%, 57%) versus 71% (100%, 0) in the placebo-PDT arm (p=0.008). Both the number of vanishing warts and the difference in relative wart area of persisting warts at week 14 and 18 were significant (p<0.05) in favour of ALA-PDT. Significantly more ALA-PDT warts were graded at a higher pain intensity after treatment than placebo-PDT warts.

INTERPRETATION

ALA-PDT is superior to placebo-PDT when both wart area and number of vanishing warts are considered.

Photodynamic therapy in dermatology

The combination of light and chemicals to treat skin diseases is widely practiced in dermatology. Within this broad use of light and drugs, in recent years the concept of photodynamic therapy (PDT) has emerged. PDT is a promising modality for the management of various tumors and nonmalignant diseases, based on the combination of a photosensitizer that is selectively localized in the target tissue and illumination of the lesion with visible light, resulting in photodamage and subsequent cell death. Moreover, the fluorescence of photosensitizing compounds is also utilized as a helpful diagnostic tool for the detection of neoplastic tissue. Intensive basic and clinical research culminated in the worldwide approval of PDT for bladder, esophageal, and lung cancer. The expanding use of this relatively new therapeutic modality in dermatology at many centers around the world has revealed its efficacy for the treatment of cutaneous precancer and cancer, as well as selected benign skin disorders. The following article summarizes the main principles of PDT considering the most recent developments and provides a comprehensive synopsis of the present status of the use of PDT in dermatology. (J Am Acad Dermatol 2000;42:389-413.)

LEARNING OBJECTIVE

At the conclusion of this learning activity, participants should be able to describe the basic concepts of PDT, including fundamental knowledge of the most relevant photosensitizers, the light sources, the mechanisms involved in PDT-mediated cell destruction, as well as the indications and limitations of photodynamic treatment of skin diseases.

Combination therapy of resistant warts in a patient with AIDS

BACKGROUND

An AIDS patient on anti-HIV therapy consisting of two reverse transcriptase inhibitors had a low CD4+ lymphocyte count, a high HIV viral RNA load, and facial warts that were resistant to ablative therapy.

OBJECTIVE

To find a regimen to treat resistant warts in an AIDS patient with a depressed CD4 count and high HIV viral load.

METHODS

A protease inhibitor was added to his regimen and he was treated with ablative therapy using a 585 nm flashlamp-pumped pulsed dye laser (FPPDL).

RESULTS

Observed resolution of the warts one month later, with no recurrence at seven-month follow-up.

CONCLUSIONS

Treatment of resistant warts in patients with AIDS may be enhanced by triple-drug therapy which includes a protease inhibitor, used in combination with ablative therapy, such as the FPPDL.