High levels of discordance between sequencing and serological subtyping in a predominantly non-B subtype HIV-1 infected cohort.

Samples from 457 randomly selected HIV-1 infected patients attending King's College Hospital were analysed using a subtype specific enzyme immunoassay. All serotyped non-Bs that provided unambiguous sequence and for which sufficient sample was available (n=100), which included three serotyped subtype B samples were further analysed by env sequencing and subtyping using neighbour joining phylogenetic analysis, the NCBI Retrovirus Genotyping tool and the Los Alamos BLAST search tool. Of the serotyped viruses, 45% (n=204) samples were subtype B. Specifically serotyped non-B strains (n=130) accounted for 28% of the total, of which the largest proportion were subtype C (n=66). Twenty-seven samples (6%) were classified as non-B, 9% (n=40) were multiply-reactive and 12% were non-reactive (n=56). Of the 100 samples subtyped by sequencing the majority were subtype C (n=32), followed by subtype A (n=20). There was little concordance between the two methods. Although a 100% match was found among the serotyped and sequenced non-B viruses (n=13), only 16 of the sequenced subtype C specimens matched the 29 obtained by serotyping. Of the 20 multiply-reactive samples analysed by serotyping, only 1 sample consisted of a subtype mixture by sequencing. Of the 14 serologically non-reactive samples analysed, all were successfully sequenced, with subtype B strains (57%) the most common. Sequencing 15 samples in both env and pol regions revealed differences in subtype assignment for the same sample in some cases. Only 1/6 env subtype A and 4/5 env subtype C samples were concordant in pol sequence subtype. Differences were also found in subtyping by the different methods used. The overall agreement between the three methods was 89%. Four out of 11 samples agreed between the phylogenetic and Los Alamos methods, 1/11 between phylogenetic and BLAST and 2/11 between Los Alamos and BLAST.

HIV incidence appears constant in men who have sex with men despite widespread use of effective antiretroviral therapy.

OBJECTIVE: To estimate the trend in HIV incidence between 1995 and 2001 in men who have sex with men (MSM) attending sexually transmitted infection (STI) clinics in the UK. DESIGN: The Serological Testing Algorithm for Recent HIV Seroconversion (STARHS) was applied to serum specimens from MSM attending 15 STI clinics collaborating in an HIV unlinked anonymous prevalence serosurvey. METHODS: STARHS was performed on anti-HIV-1 positive specimens and HIV incidence rates determined. Specimens from MSM with previously diagnosed HIV or an AIDS defining condition were excluded. National data on uptake of antiretroviral therapy (ART), AIDS mortality and diagnoses of gonorrhoea in MSM were used to aid interpretation of the HIV incidence findings. RESULTS: Of 43,100 specimens collected from MSM 3565 were anti-HIV-1 positive. Of these, 1645 were eligible and available for STARHS testing, of which 317 were deemed to come from recently acquired infections. The overall estimated annual incidence ranged from 1.5% (1999) to 3.3% (1996). In 2001 it was 2.45%, with a 3.1% incidence in London and 1.0% elsewhere. No significant trends in HIV incidence were found. CONCLUSIONS: Despite the widespread use of ART there was no significant decline in HIV incidence. Individuals whose HIV infection has been diagnosed should be less infectious. However, over 20% of infections in MSM remain undiagnosed, many with acute STI, and this pool of unmanaged HIV infection may be an important driver of the ongoing epidemic. Initiatives to diagnose and treat a greater proportion of HIV infections may be the key to reducing HIV incidence in MSM.

Reconciling HIV incidence results from two assays employed in the serological testing algorithm for recent HIV seroconversion (STARHS).

The Abbott HIVAB and Vironostika HIV-1 Microelisa assays have both been validated for use in the serological testing algorithm for recent HIV seroconversion (STARHS). This ability to identify recently-acquired infection provides valuable insight into the epidemic. The availability of each assay during different periods led to longitudinal studies of annual HIV incidence being based on a mixture of results from each. We investigated whether results from both assays could be reconciled. Using statistical methods, the correlation of the two assays' results and other performance characteristics were examined. Of 378 anti-HIV-1 positive specimens examined by both assays, the Abbott assay flagged 40 as from recent infections, whereas Vironostika flagged 50. The correlation coefficient between screening reactivities in each assay was 0.84, and 0.77 in confirmatory mode. Abbott screening results were significantly higher than its confirmatory results, and some specimens from recent infections may consequently have gone undetected by that assay. This problem was not found with the Vironostika assay. Observational data indicated that the estimated HIV incidence derived from HIVAB results increased as the assay threshold, with its pre-defined seroconversion window, was increased. For Vironostika, the estimated HIV incidence remained stable over a wide range of thresholds. Modelling of the observed relationship between the two assays allowed an estimate of the equivalent threshold in the alternative assay, thus providing a means of reconciling results. Our findings suggest that the Vironostika assay is more reliable than the HIVAB, is easier to use, and is able to allow processing of more specimens per run.

Evidence for onward transmission of HIV-1 non-B subtype strains in the United Kingdom.

An increasing proportion of new HIV diagnoses in the United Kingdom and other European countries are attributable to non-B subtype infections, mainly among black Africans with infections heterosexually acquired in sub-Saharan Africa. We examined whether there was evidence for onward transmission of non-B subtypes within an ethnically diverse HIV-1-infected cohort in South London. Three hundred eighty-four HIV-1-infected patients attending Kings College Hospital were subtyped using an in-house enzyme-linked immunoassay and env sequencing. Epidemiologic data were obtained from medical chart review and the patients' physician and were used to establish the most likely source and country of infection. Overall, 344 patients (154 black African, 148 white UK-born, and 42 black Caribbean) had an identifiable subtype. The prevalence of non-B subtypes among the black African, white, and black Caribbean patients was 96.8%, 14.2%, and 31%, respectively. Most non-B subtype infections were identified in black Africans (149 of 183 cases) and were mainly acquired in sub-Saharan Africa, but 22.9% (42 of 183 cases) of all non-B infections were probably acquired in the United Kingdom. Among the 21 white UK-born patients infected with a non-B subtype, 15 probably acquired the infection in the United Kingdom and only 6 of these patients reported a source sexual partner from an HIV endemic area. All 13 black Caribbean patients with a non-B infection most likely acquired their infection in the United Kingdom, most of whom (8 of 13 patients) were probably infected by a partner from an HIV endemic area. Potential acquisition of HIV infection in the United Kingdom was lowest among black African patients with a non-B infection, and most of these infections were probably acquired from a partner originating from an HIV endemic area. This study provides the first evidence for onward transmission of non-B subtypes in the United Kingdom, particularly among the black Caribbean population.