Immunology of Varicella Immunization in the elderly

Infections in Older Adults

Infections in elderly patients can prove diagnostically challenging. Age-related factors affecting the immune system in older individuals contribute to nonspecific presentations. Other age-related factors and chronic conditions have symptoms that may or may not point to an infectious diagnosis. Delay in administration of antimicrobials can lead to poor outcomes; however, unnecessary administration of antimicrobials can lead to increased morbidity and contribute to the emergence of multidrug-resistant organisms. Careful clinical assessment and consideration of patient history and risk factors is crucial. When necessary, antimicrobials should be chosen that are appropriate for the diagnosis and deescalated as soon as possible.

Insights into the role of immunosenescence during varicella zoster virus infection (shingles) in the aging cell model

Varicella zoster virus (VZV) is the etiological agent of shingles, a painful skin rash that affects a significant proportion of the elderly population. In the present study, we used two aging cell models, Hutchinson-Gilford progeria syndrome (HGPS) fibroblasts and stress or replicative senescence-induced normal human dermal fibroblasts (NHDFs), to investigate age-associated susceptibility to VZV infection. VZV infectivity titers were significantly associated with donor age in HGPS fibroblasts and senescence induction in NHDFs. High throughput RNA-sequencing (RNA-seq) analysis was performed to assess global and dynamic changes in the host transcriptomes of VZV-infected aging cells. Analysis of differentially expressed genes (DEGs) indicated that VZV infection in aged HGPS fibroblasts resembled that in senescent NHDFs, particularly in terms of genes associated with pattern recognition receptors in virus sensing network, providing novel insights into the mechanisms of senescence-associated susceptibility to VZV infection. Additionally, we identified stimulator of interferon genes (STING) as a potential VZV sensing receptor. Knockdown of STING expression resulted in increased viral replication in primary fibroblasts, whereas STING overexpression led to suppression of VZV plaque formation. In conclusion, our findings highlight the important role of immunosenescence following VZV infection and provide significant insights into the mechanisms underlying cellular sensing of VZV infection and the induction of immune responses in aged skin cells.

Prevention of shingles by varicella zoster virus vaccination

Herpes zoster is caused by reactivation from previous varicella zoster virus (VZV) infection, and affects millions of people worldwide. It primarily affects older adults and those with immune system dysfunction, most likely as a result of reduced or lost VZV-specific cell-mediated immunity. Complications include post-herpetic neuralgia, a potentially debilitating and chronic pain syndrome. Current treatment of herpes zoster and post-herpetic neuralgia involves antiviral agents and analgesics, and is associated with significant economic cost. Results from several clinical trials have determined that a live, attenuated VZV vaccine using the Oka/Merck strain (Zostavax) is safe, elevates VZV-specific cell-mediated immunity, and significantly reduces the incidence of herpes zoster and post-herpetic neuralgia in people over 60 years of age. Regulatory approval has recently been obtained and once launched, it is expected that this vaccine will significantly reduce the morbidity and financial costs associated with herpes zoster. Durability of vaccine response and possible booster vaccination will still need to be determined.

Skin infections and ageing

Elderly individuals have an increased susceptibility to skin infections due to age-related anatomical, physiological and environmental factors. The types of organisms that cause primary skin and soft tissue infections are diverse, and include bacterial, viral and fungal pathogens as well as parasites. In the elderly, these infections and infestations may present with atypical signs and symptoms or may complicate underlying chronic skin disorders. Clinical features, investigations and management of the following important and common skin infections are described in more detail: cellulitis, erysipelas, necrotizing fasciitis, impetigo, folliculitis, furunculosis and carbunculosis, erythrasma, herpes zoster and postherpetic neuralgia, herpes simplex, warts, molluscum contagiosum, dermatophytosis of the skin, hair and nails, candidiasis, and scabies. Treatment should be based on the results of the appropriate diagnostic tests. Correct diagnosis and therapy of skin infections lead to satisfactory outcome in the majority of elderly patients.

Clinical manifestations of varicella-zoster virus infection

Infections by VZV, the virus that causes chickenpox and herpes zoster, usually are diagnosed by the classic clinical presentations. In immunocompromised patients, however, the atypical presentation can make the diagnosis more challenging. Although varicella typically follows an uncomplicated course in children, adults and immunocompromised patients can develop complications involving several organs; some complications may be fatal. Prevention of disease with the vaccine is ideal. When varicella or zoster infection does occur, proper treatment should be initiated, depending on the age and immune status of the patient.