What is Herpes Simplex Virus (HSV) 1?

From the Guidelines

Herpes Simplex Virus Type 1 (HSV-1) is a common viral infection that primarily causes oral herpes, characterized by cold sores or fever blisters around the mouth, and the most effective treatment for active HSV-1 outbreaks is antiviral medications like acyclovir, valacyclovir, or famciclovir, as recommended by the most recent guidelines 1. For active HSV-1 outbreaks, antiviral medications like acyclovir (400mg three times daily for 5-10 days), valacyclovir (1g twice daily for 7-10 days), or famciclovir (250mg three times daily for 7-10 days) are recommended.

• The aim of antiviral therapy is to block viral replication to enable shortening the duration of symptoms and to accelerate healing of the lesions associated with herpes labialis, as stated in the study 1.
• For frequent recurrences (more than 6 per year), suppressive therapy with acyclovir (400mg twice daily) or valacyclovir (500mg daily) may be prescribed.
• During outbreaks, keep the affected area clean and dry, avoid touching or picking at sores, wash hands frequently, and avoid sharing personal items.
• HSV-1 is highly contagious, especially during active outbreaks, and spreads through direct contact with infected saliva or sores.
• While there's no cure for HSV-1, these medications can reduce symptoms, speed healing, and decrease viral shedding, making transmission less likely, as supported by the guidelines 1.
• The virus remains dormant in nerve cells between outbreaks and can reactivate due to triggers like stress, illness, sun exposure, or hormonal changes.
• The episodes of genital HSV-1 infection are indistinguishable from genital HSV-2 infection but genital HSV-1 infection recurs less frequently than genital HSV-2 infection, as noted in the study 1.

From the FDA Drug Label

Acyclovir is a synthetic purine nucleoside analogue with in vitro and in vivo inhibitory activity against herpes simplex virus types 1 (HSV-1), 2 (HSV-2), and varicella-zoster virus (VZV) The inhibitory activity of acyclovir is highly selective due to its affinity for the enzyme thymidine kinase (TK) encoded by HSV and VZV. Using plaque-reduction assays, the IC 50 against herpes simplex virus isolates ranges from 0.02 to 13.5 mcg/mL for HSV-1 and from 0.01 to 9. 9 mcg/mL for HSV-2. Valacyclovir hydrochloride is rapidly converted to acyclovir, which has demonstrated antiviral activity against HSV types 1 (HSV‑1) and 2 (HSV‑2) and VZV both in cell culture and in vivo The EC 50 values against herpes simplex virus isolates range from 0.09 to 60 microM (0.02 to 13.5 mcg/mL) for HSV‑1 and from 0.04 to 44 microM (0.01 to 9. 9 mcg/mL) for HSV‑2.

Acyclovir and valacyclovir are effective against HSV-1.

• The drugs work by inhibiting the replication of herpes viral DNA through competitive inhibition of viral DNA polymerase, incorporation into and termination of the growing viral DNA chain, and inactivation of the viral DNA polymerase 2 3.
• The IC50 values for acyclovir against HSV-1 range from 0.02 to 13.5 mcg/mL, indicating the drug's potency against the virus.
• Valacyclovir, which is converted to acyclovir in the body, also demonstrates antiviral activity against HSV-1.

From the Research

Overview of HSV-1

• Herpes simplex virus type 1 (HSV-1) is a major cause of morbidity and mortality worldwide, giving rise to a variety of clinical disorders 4.
• HSV-1 infections are common in the oral and perioral area, and can cause herpes labialis, herpetic gingivostomatitis, and other conditions 4.

Treatment of HSV-1 Infections

• Systemic antiviral therapy, such as aciclovir (ACV), has been widely accepted as effective for primary herpetic gingivostomatitis 4.
• Topical therapy, such as ACV 5% cream or penciclovir 1% cream, can be effective for herpes labialis 4.
• Suppressive antiviral therapy with ACV, valacyclovir, or famciclovir can decrease the number of patients with at least one recurrence of genital herpes per year 5.
• Current therapies, including episodic treatment and chronic suppressive therapy, are generally well tolerated and effective in shortening the duration of symptoms and improving quality of life 6.

Anti-HSV-1 Agents

• Anti-HSV-1 drugs, such as specific or non-specific nucleotide (nucleoside) analogs and helicase-primase inhibitors, have become the main clinical agents for the treatment of HSV-1 infections 7.
• Development of new anti-HSV-1 compounds or therapies is key to addressing the issue of resistance 7.
• There are no approved commercially available vaccines for HSV-1, making antiviral chemotherapeutic agents the primary intervention for preventing the worst sequelae of recurrent outbreaks 8.