Recently, significant numbers of individuals with primary human immunodeficiency virus (HIV) infectionhave been found to harbor viral strains with reduced susceptibility to antiretroviral drugs. In one study, HIV from 16% of such antiretroviral-naive individuals was shown to have a susceptibility to nonnucleoside reverse transcriptase (RT) inhibitors (NNRTIs) between 2.5-and 10-fold lower than that of a wild-type control. Mutations in the RT domain that had previously been associated with antiretroviral resistance were not shared by these strains. We have analyzed by logistic regression 46 variable amino acid sites in RT for their effect on susceptibility and have identified two novel sites influencing susceptibility to NNRTIs: amino acids 135 and 283 in RT. Eight different combinations of amino acids at these sites were observed among these patients. These combinations showed a 14-fold range in mean susceptibility to both nevirapine and delavirdine. In vitro mutagenesis of the control strain combined with a phenotypic assay confirmed the significance of amino acid variation at these sites for susceptibility to NNRTIs.

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Historically, subtype B viruses in men who have sex with men (MSM) and injecting drug users (IDU) dominated the HIV epidemic in the United Kingdom, whereas non-B heterosexual infections dominate globally. Heterosexual contact is now the most common route of transmission in the United Kingdom. Here we monitor HIV subtype in Scotland, and link it to origin of infection. HIV-1 sequence was generated from new diagnoses and the subtype thus obtained linked with demographic data. Virus was subtyped from 80% (137/171) of all new diagnoses in Scotland. Of 58 individuals infected by heterosexual contact, 74% (43) harboured non-B viruses, contrasting with 7% (5/68) of those infected by IDU or MSM. Eighty-four per cent of non-Bs (46/55) were probably acquired outside the United Kingdom, but nine individuals probably acquired their non-B infection in the United Kingdom. Non-B subtypes of HIV-1 predominate in recently diagnosed, heterosexually acquired infections in Scotland and are present in all risk groups, even those with no exposure outside the United Kingdom.

Genetically engineered herpes simplex virus ICP34.5 null mutants replicate only in dividing cells and have shown potential for the treatment of malignant disease, including glioma. Phase I trials have demonstrated the safety of these viruses in various clinical settings but it is envisaged that for full efficacy they will be used in combination with other therapeutic modalities. To enhance virus-induced tumour cytotoxicity, we have engineered an ICP34.5 null mutant (HSV1716) of HSV1 which expresses the noradrenaline transporter gene (NAT). This virus is designated HSV1716/NAT. We have shown previously that introduction of the NAT gene into a range of tumour cells, via plasmid-mediated transfection, conferred the capacity for active uptake of the radiopharmaceutical [131I]MIBG and resulted in dose-dependent toxicity. In this study, combination therapy utilising HSV1716/NAT and [131I]MIBG was assessed in vitro by the MTT assay. We demonstrate that the NAT gene, introduced by HSV1716/NAT into cultured glioma cells, was expressed 1 h after viral infection, enabling active uptake of [131I]MIBG. The combination of viral oncolysis and induced radiopharmaceutical uptake resulted in significantly enhanced cytotoxicity compared to either agent alone and the response was dose- and time-dependent. These studies show that the combination of oncolytic HSV therapy with targeted radiotherapy has the potential for effective tumour cell kill and warrants further investigation as a treatment for malignant glioma.

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