Comment on Jameson et al.: Prevalence of antibodies against hantaviruses in serum and saliva of adults living or working on farms in Yorkshire, United Kingdom.

This British hantavirus IgG prevalence study, aimed at 119 asymptomatic farmers in England, and using indirect immunofluorescence assay (IFA) as screening technique, concluded that rat-transmitted Seoul virus (SEOV) might be the main suspect as hantaviral pathogen in the UK. Exactly the same conclusion, using the same IFA screening technique, resulted from a 1994 serosurvey in the same country, and in 627 clinical cases plus 100 healthy controls. SEOV-positive study subjects were also mainly farmers with heavy rat-exposure, but residing in Northern-Ireland, a region where all other known rodent reservoirs for pathogenic hantaviruses are known to be absent, except the wild rat. A rodent capture action in and around the farms of eight seropositives confirmed SEOV seropositivity in 21.6% of 51 rats. All SEOV seropositives were patients, hospitalized with an acute feverish condition, a majority of which having the clinical picture of hantavirus-induced nephropathy, known as hemorrhagic fever with renal syndrome (HFRS). Leptospirosis, often mimicking perfectly HFRS, was serologically excluded. Thus, SEOV was established as a human hantaviral pathogen in the UK and in Europe 20 years ago.

A 21-base pair insertion/duplication at codon 69 of the HIV type 1 reverse transcriptase in a patient undergoing multiple nucleoside therapy.

We describe the selection of a previously unreported 21-base pair insertion following codon 69 of the HIV-1 reverse transcriptase (RT) from a patient undergoing multiple nucleoside analogue therapy. This insertion was a direct duplication of the preceding 21 bases of HIV-RT, and was selected in a background of NRTI-resistance mutations including substitutions at RT codons 41, 67, 184, 210, and 215. Longitudinal genotypic and phenotypic resistance tests performed before and after selection of the insertion suggested that the insertion conferred an additional decrease in susceptibility to some nucleoside analogues, most notably didanosine, stavudine, abacavir, and tenofovir. However, phenotypic analysis of an insertion-containing site-directed mutant constructed in an HIV-1 HXB2 background revealed no direct association between the 21-base pair insertion and decreased susceptibility to NRTIs, suggesting that the insert requires the context of the patients' virus in order to confer resistance. These observations may offer new insight into the relative contribution of HIV-RT codon 69 insertion mutations to antiretroviral resistance.

Investigation of baseline susceptibility to protease inhibitors in HIV-1 subtypes C, F, G and CRF02_AG.

OBJECTIVE: To compare baseline susceptibility to protease inhibitors among HIV-1 isolates of subtypes C, F, G and CRF02_AG, and to identify polymorphisms that determine the differences in susceptibility. METHODS: A total of 42 samples of drug-naive patients infected with subtypes G (n=19), CRF02_AG (n = 10), F (n = 6) and C (n = 7) were phenotyped and genotyped with the Antivirogram and the ViroSeq 2.0 genotyping system, respectively. A Bayesian network approach was used for a preliminary analysis of the collected data and the dependencies indicated by the network were statistically confirmed. RESULTS: CRF02_AG samples were found to be more susceptible to nelfinavir and ritonavir than other subtypes. Hypersusceptibility to these drugs was associated with the 70R polymorphism. 37D/S/T was associated with reduced susceptibility to indinavir and 89M with reduced susceptibility to lopinavir. Susceptibility to tipranavir was the lowest among the subtype F samples and the highest for subtype G samples, with samples carrying 57R being more susceptible than samples carrying 57K. CONCLUSIONS: Our study suggests that there are baseline susceptibility differences between subtypes and these differences are due to naturally occurring polymorphisms in these subtypes. The predictive value for phenotype of these polymorphisms was even valid in subtypes where these polymorphisms are less prevalent. Taking into account such polymorphisms should improve current algorithms for interpretation of genotyping results in a subtype-independent way.

Protease mutation M89I/V is linked to therapy failure in patients infected with the HIV-1 non-B subtypes C, F or G.

OBJECTIVE: To investigate whether and how mutations at position 89 of HIV-1 protease were associated with protease inhibitor (PI) failure, and what is the impact of the HIV-1 subtype. METHODS: In a database containing pol nucleotide sequences and treatment history, the correlation between PI experience and mutations at codon 89 was determined separately for subtype B and several non-B subtypes. A Bayesian network model was used to map the resistance pathways in which M89I/V is involved for subtype G. The phenotypic effect of M89I/V for several PIs was also measured. RESULTS: The analysis showed that for the subtypes C, F and G in which the wild-type codon at 89 was M compared to L for subtype B, M89I/V was significantly more frequently observed in PI-treated patients displaying major resistance mutations to PIs than in drug-naive patients. M89I/V was strongly associated with PI resistance mutations at codons 71, 74 and 90. Phenotypically, M89I/V alone did not confer a reduced susceptibility to PIs. However, when combined with L90M, a significantly reduced susceptibility to nelfinavir was observed (P < 0.05) in comparison with strains with L90M alone. CONCLUSIONS: The results of the present study show that M89I/V is associated with PI experience in subtypes C, F and G but not in subtype B. M89I/V should be considered a secondary PI mutation with an important effect on nelfinavir susceptibility in the presence of L90M.

Rare mutations at codon 103 of HIV-1 reverse transcriptase can confer resistance to non-nucleoside reverse transcriptase inhibitors.

BACKGROUND: The K103N mutation in HIV-1 reverse transcriptase (RT) confers high-level resistance to current non-nucleoside reverse transcriptase inhibitors (NNRTI). The prevalence and resistance profile of HIV-1 with other substitutions at RT codon 103 is less well documented. METHODS: K103 substitutions among over 70,000 clinical samples submitted for routine antiretroviral resistance testing at two independent centres were examined. Phenotypic resistance profiles of isolates harboring rare K103 variants in the absence of known NNRTI-associated resistance mutations were retrieved from Virco's correlative genotype/phenotype database. Genotyped samples with known treatment histories were retrieved from the British Columbia Centre for Excellence in HIV/AIDS database. Site-directed mutants containing K103 variants were constructed and phenotyped. RESULTS: K103N, R and S were observed in 29, 1.8, and 0.9% of Virco isolates and in 16, 1.5 and 0.4% of British Columbia isolates. K103T/Q/H substitutions were observed only rarely (<0.2%). The prevalence of unusual codon 103 substitutions remained stable over 5 years, except K103S, which increased over fourfold in both datasets. K103R/Q-containing clinical isolates remained phenotypically susceptible to NNRTI, whereas K103S/T/H-containing isolates showed over 10-fold decreased NNRTI susceptibility. Among patients with a known treatment history, K103S/T/H were observed primarily in individuals failing NNRTI-containing regimens. Site-directed mutants confirmed decreased susceptibility to NNRTI in K103S/T/H-containing recombinants. CONCLUSION: Variants at HIV RT codon 103 other than K103N are observed relatively rarely in clinical isolates, but K103 S, T and H confer decreased susceptibility to NNRTI. These data are relevant for interpretive genotype algorithms and in the design of assays specific to RT codon 103 mutations.

Long-term efficacy of routine access to antiretroviral-resistance testing in HIV type 1-infected patients: results of the clinical efficacy of resistance testing trial.

The long-term efficacy of making resistance testing routinely available to clinicians has not been established. We conducted a clinical trial at 6 US military hospitals in which volunteers infected with human immunodeficiency virus type-1 were randomized to have routine access to phenotype resistance testing (PT arm), access to genotype resistance testing (GT arm), or no access to either test (VB arm). The primary outcome measure was time to persistent treatment failure despite change(s) in antiretroviral therapy (ART) regimen. Overall, routine access to resistance testing did not significantly increase the time to end point. Time to end point was significantly prolonged in the PT arm for subjects with a history of treatment with > or =4 different ART regimens or a history of treatment with nonnucleoside reverse-transcriptase inhibitors before the study, compared with that in the VB arm. These results suggest that routine access to resistance testing can improve long-term virologic outcomes in HIV-infected patients who are treatment experienced but may not impact outcome in patients who are naive to or have had limited experience with ART.

Genotype and phenotype at baseline and at failure in human immunodeficiency virus-infected antiretroviral-naive patients in a randomized trial comparing zidovudine and lamivudine plus nelfinavir or nevirapine.

For the 127 Spanish patients enrolled in the Combine Study, a resistance substudy was performed with 100 (79%) plasma samples obtained at baseline and with 18 samples obtained from 19 patients at the time they experienced treatment failure. At baseline, primary mutations to nonnucleoside reverse-transcriptase inhibitors and protease inhibitors were not detected, whereas mutations to nucleoside reverse-transcriptase inhibitors were observed in 10% of patients. At failure, mutations were detected in 7 of 16 patients. An agreement in the results of virtual and real phenotypes was observed in the 93 samples in which both tests were performed.

A mutation in the 3' region of the human immunodeficiency virus type 1 reverse transcriptase (Y318F) associated with nonnucleoside reverse transcriptase inhibitor resistance.

The Y318F substitution in the 3' region of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) has been linked to nonnucleoside RT inhibitor (NNRTI) resistance in vitro. A systematic search of a large phenotypic-genotypic database (Virco) linked the Y318F substitution with a >10-fold decrease in NNRTI susceptibility in >85% of clinically derived isolates. There was a significant association between Y318F and use of delavirdine (P = 10(-11)) and nevirapine (P = 10(-6)) but not efavirenz (P = 0.3). Site-directed HIV-1 Y318F mutants in an HXB2 background displayed 42-fold-decreased susceptibility to delavirdine but <3-fold-decreased susceptibility to nevirapine or efavirenz. Combinations of Y318F with K103N, Y181C, or both resulted in decreased efavirenz susceptibility of 43-, 3.3-, and 84-fold, respectively, as well as >100- and >60-fold decreases in delavirdine and nevirapine susceptibility, respectively. These results indicate the importance of the Y318F substitution in HIV-1 drug resistance.