Papiine herpesvirus 2 as a Predictive Model for Drug Sensitivity of Macacine herpesvirus 1 (Monkey B Virus)

Monkey B virus (Macacine herpesvirus 1; BV) is endemic in macaques. BV (a BSL4 agent) is the primary zoonotic concern for persons working with macaques in research, and human BV infections frequently are fatal. We assessed the use of a BSL2 baboon herpesvirus (Papiine herpesvirus 1; HVP2) for predicting the drug sensitivity of BV by comparing the sensitivity of the 2 viruses to 12 antiherpetic drugs. Plaque reduction assays showed that 4 drugs (HBPG, BVdU, PFA, and BrdU) were ineffective against both viruses. Of the 8 effective drugs, both viruses were most sensitive to TFT, whereas sensitivity to the remaining 7 drugs varied between BV and HVP2 as well as between strains of HVP2. In addition, the efficacy of 5 drugs (ACV, PCV, GCV, CDV, and EDU) was tested by using a murine model. ACV and EDU were completely ineffective against both HVP2 and BV, and high doses of PCV only delayed death by a few days. GCV and CDV both protected mice against death, and CDV also prevented the development of neurologic symptoms. When the initiation of drug therapy was delayed until after virus gained access to the CNS, both GCV and CDV were ineffective. The similarity of the drug sensitivities of HVP2 and BV in both models validates the use of HVP2 as a BSL2 level model that can be used to predict drug sensitivity of BV. The greater efficacy of CDV relative to GCV suggests the potential for use of CDV in the treatment of zoonotic BV infections.Abbreviations: ACV, acyclovir; AraA, 9-β-D-arabinofuranosyl-adenine; BrdU, 5-bromo-2′-deoxyuridine; BV, monkey B virus; BVdU, (E)-5-(2-bromovinyl)-2′-deoxyuridine; CDV, cidofovir; EDU, 5-ethyl-2′-deoxyuridine; GCV, ganciclovir; HBPG, 9-(4-hydroxybutyl)-N²-phenylguanine; HSV, herpes simplex virus; HVP2, Herpesvirus papio 2; IUdR, 5-iodo-2’-deoxyuridine; PCV, penciclovir; PFA, phosphonoformic acid; TFT, trifluorothymidineMacacine herpesvirus 1 (monkey B virus; BV) is an alpha-herpesvirus of macaque monkeys and is closely related to human herpes simplex virus (HSV) types 1 and 2.^8,11,27 Although BV primarily causes asymptomatic or mild, self-limiting disease in healthy macaques, the virus is extremely neurovirulent when transmitted via bites or scratches to other nonmacaque primate species, including humans. Although human infections are not common, approximately 80% of untreated patients die of BV infection, and survivors frequently continue to suffer from neurologic sequelae. As a consequence of its lethality in humans, BV is classified as a BSL4 pathogen³ and is the single most serious zoonotic concern for veterinary and research personnel who work with macaques. The increasing popularity of ecotourism to monkey temples in Southeast Asia, where tourists and wild, BV-infected macaque populations come into direct contact, represents another potential concern for zoonotic BV infections.^9,12,13,21The antiviral drugs recommended for use in treating BV infections all were originally developed for treatment of HSV infections.^4,18 Because the genes encoding the enzymes targeted by these drugs are conserved between these viruses, BV is sensitive to many of these anti-HSV drugs. However, compared with HSV, BV is less sensitive to these drugs.^2,10,14 Although more effective drugs are needed for the treatment of BV infections, the biohazardous nature of and facility requirements associated with studying a BSL4 agent severely limit research on BV. A potential solution to this problem is using a closely related virus whose biologic and molecular properties are very similar to those of BV as a surrogate or model system in which preliminary research can be conducted safely, leaving only confirmative testing to be done with infectious BV.Baboons carry an alpha-herpesvirus (Papiine herpesvirus 2; HVP2) that is biologically and genetically very similar to BV and HSV.^7,8,15,26 In mice, most HVP2 isolates are extremely neurovirulent and closely reflect the pathogenesis of BV in mice^20,23 At the antigenic level, HVP2 and BV are so similar that HVP2 has found use as an alternative antigen for diagnostic BV serology.^17,25,28 Despite the virus''s similarity to BV, HVP2 infections have never been reported in humans. Consequently, HVP2 is rated as a BSL2 pathogen and, as such, HVP2 can be used under BSL2/ABSL2 containment. This study was conducted to assess the potential use of HVP2 as a surrogate model system for predicting the sensitivity of BV to antiviral drugs.