Academic journal article Bulletin of the World Health Organization

Diagnosis of Human Herpesviruses: Memorandum from a WHO Meeting

Academic journal article Bulletin of the World Health Organization

Diagnosis of Human Herpesviruses: Memorandum from a WHO Meeting

Article excerpt

INTRODUCTION

The discussions of the participants at the WHO Meeting on Diagnosis of Human Herpesvirus Infections, which was held in Berlin, Germany, in August 1990, (a) complemented and updated a previous WHO Meeting held in 1983 [1].

The herpesvirus family contains several important human pathogens. They possess a large number of genera, some of which have proved to be susceptible to antiviral chemotherapy. The outstanding property of herpesviruses is their ability to establish lifelong persistent infections in their hosts and to undergo periodic reactivation. It is their frequent reactivation in immunosuppressed patients which now particularly poses serious health complications. The reactivated infection may be clinically quite different from the disease caused by the primary infection. The growing epidemic of human immunodeficiency virus (HIV) infection leading to AIDS (acquired immunodeficiency syndrome) has been associated with an increased incidence of herpesvirus diseases in these immunocompromised patients.

Herpesviruses of human include herpes simplex virus types 1 and 2 (HSV1 and HSV2), varicella-zoster virus (VZV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), and human herpesvirus 6 (HHV-6). Monkey B virus (cercopithecine herpesvirus 1) is also a human pathogen.

Classification

A useful division of Herpesviridae into subfamilies is based on the biological properties of the agents (Table 1). Alphaherpesviruses (HSV, VZV) are fast-growing cytolytic viruses that tend to establish latent infections in neurons. Betaherpesviruses (CMV) are slow-growing and cytomegalic (involving massive enlargements of infected cells) and become latent in salivary glands and kidneys. Gammaherpesviruses (EBV) infect lymphoid cells. Another herpesvirus, human B-lymphotropic cells. Another herpesvirus, human B-lymphotropic virus (HBLV), has been recovered recently from patients with lymphoproliferative disorders and has been designated as human herpesvirus 6 (HHV-6); its genome resembles that of cytomegalovirus.

There is little antigenic relatedness among the Herpesviradae. Only herpes simplex virus types 1 and 2 share a significant number of common antigens. This is not surprising, since there is approximately 50% homology between those two viral genomes.

Diseases caused by Herpesviridae

Although infection is usually inapparent, a wide range of diseases are associated with the Herpesviridae. Disease caused by primary or reactivated infection by a given virus may involve different cell types and present different clinical pictures, as described below.

(1) HSV1 and HSV2 infect epithelial cells and establish latent infections in neurons. Type 1 virus is classically associated with oropharyngeal lesions and

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causes recurrent attacks of "fever blisters". Type 2 virus primarily infects the genital mucosa and is mainly responsible for genital herpes. Both viruses also cause neurological disease; HSV1 is one of the main causes of sporadic encephalitis in temperate climates.

(2) VZV causes chickenfox (varicella) on primary infection and establishes latent infection in neurons. Upon reactivation, the virus causes "shingles" (zoster). Adults infected for the first time with VZV often develop serious pneumonia. Encephalitis has also been reported as a complication of VZV infection.

(3) CMV replicates in the epithelial cells of the respiratory tract, salivary glands, kidneys and in lymphocytes. CMV may cause infectious mononucleosis and cytomegalic inclusion disease (in new-borns); it is in an important cause of congenital defects and mental retardation.

(4) EBV replicates in epithelial cells of the oropharynx and parotid gland, and establishes latent infections in lymphocytes. It causes infectious mononucleosis and appears to be the cause of or closely associated with two human cancers, one of lymphoma and the other a carcinoma. …

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