Travel and the spread of HIV-1 genetic variants

HIV-1 comprises three groups, the main (M group), O (outlier) and N (non-M, non-O). The M group, divided into 11 subtypes, is responsible for the global HIV-1 pandemic. Recombination between M subtypes has resulted in the generation of multiple circulating recombinant forms (CRFs) consisting of mosaic lineages. Most subtypes and CRFs are represented in Africa, whereas predominance of one or a few subtypes was reported initially elsewhere. This finding reflects the African origin of the epidemic. In western countries, where the B subtype is predominant, there is a steep increase in non B-subtypes and CRFs, while new recombinants emerge worldwide. Travellers contribute to the spread of HIV-1 genetic diversity worldwide, and in the developing world migration of rural populations and civil war are additional contributing factors. The spreading of HIV-1 variants has implications for diagnostic, treatment, and vaccine development

Detection et quantification des acides nucleiques en infectiologie: utilite, certitudes et limites

The amplification of nucleic acids is often used for the diagnosis and the follow-up of infectious diseases. The interpretation of PCR results varies according to the pathogens detected, the site of infection and the clinical presentation. PCR tests might be the reference method or only an help for the diagnosis. With the development of antiviral treatments quantitative PCR tests are now essential for the evaluation of treatment efficacy. A discussion with the laboratory is important for the correct interpretation of PCR results

Early and prolonged decrease of viremia in HIV-1-infected patients treated with didanosine

Fourteen patients previously treated with zidovudine were monitored for laboratory parameters and clinical events during 1 year after introduction of didanosine (ddI) monotherapy. Proviral human immunodeficiency virus type 1 (HIV-1) copy numbers (cell-associated DNA) and concentration of free virions (viremia) were determined using a semiquantitative polymerase chain reaction (PCR). High levels of circulating virus were detected in all patients (range, 17 to 5,934 x 10(3)/ml of serum). Within 4 weeks of therapy, a decrease of viremia (60 to 98%) was observed in nine patients. After 1 year of treatment, eight of these nine patients still had decreased viremia when proviral HIV DNA was decreased or stable, and CD4+ lymphocytes were stable or higher in seven of these eight patients. Antiviral effect was more pronounced in the six patients with CD4+ > 100/mm3 at entry, five of them belonging to the subgroup of the seven responding patients as compared to two of eight patients with CD4+ < 100/mm3. Clinical events in this small group were not statistically correlated with virologic parameters; however, responding patients had a tendency to stabilize or gain weight. This study suggests that measurement of viremia deserves further study as a marker of antiviral efficacy and might predict, even at 4 weeks, the beneficial potential of ddI

Predictive value of codon 215 reverse transcriptase mutation on the efficacy of didanosine in HIV-infected, zidovudine-experienced patients

We investigated whether or not mutations at codon 215 in the HIV reverse-transcriptase-encoding gene predicted a lower efficacy of didanosine therapy, as defined by survival of patients and change in CD4 cell counts in 121 HIV-infected, zidovudine-experienced patients. A trend for shorter survival, although not reaching significance, was observed for patients with HIV strains with the reverse transcriptase codon 215 mutation (P = 0.07), but this trend disappeared after adjustment for initial CD4 cell counts. During the first 3 months on didanosine therapy, the increase in CD4 cell counts was greater in patients who were wild type at codon 215 than in those with the mutation at codon 215 (P = 0.03). These data suggest that there was a better initial CD4 response to didanosine therapy in patients with HIV without the mutation at codon 215, but that this response did not translate into increased survival

Absence of chronic human immunodeficiency virus infection without seroconversion in intravenous drug users: a prospective and retrospective study

It has been reported that human immunodeficiency virus type 1 (HIV-1) infection may exist in persons without specific antibodies for years. To measure the frequency of a silent carrier state, a study was conducted in a cohort of 124 intravenous drug users (IVDUs) without anti-HIV-1 antibodies. All the participants had engaged in high-risk behavior for HIV-1 transmission for a number of years until 1987 or later. Samples were analyzed at 6-month intervals for the presence of HIV-1 provirus using DNA amplification and for the appearance of anti-HIV-1 antibodies. HIV-1 provirus and antibodies were undetectable in 122 participants, whereas seroconversion was observed in 2. In one of these, both amplified HIV-1 pol gene segment and anti-HIV-1 antibodies were detected simultaneously, and in the other, provirus was detected 1 month before seroconversion. This study suggests that long-term HIV-1 infection without anti-HIV-1 antibodies is rare and that repeated antibody testing is sufficient to determine the HIV-1 status of a person no longer at high risk for HIV-1 infection

Drug resistance mutations during structured treatment interruptions

BACKGROUND: We assessed whether treatment interruptions induce selection of mutations associated with drug resistance in the Swiss-Spanish Intermittent Treatment Trial (SSITT). Patients had been on HAART without previous failure and had undetectable viraemia for at least 6 months. Their HAART was interrupted for 2 weeks and restarted for 8 weeks. After four of these cycles, treatment was definitively interrupted at week 40. METHODS: Genotypic resistance testing was performed in 87/97 Swiss patients: in those failing treatment before week 40, at the time of first viral rebound > 500 copies/ml off treatment and preceding failure to reach RNA 1000 copies/ml after week 40. RESULTS: Mutations associated with drug resistance were detected in 9/25 (36%) patients with virological failure during the first 40 weeks and in 6/59 (10%) patients after week 40. Overall, drug resistance mutations were detected in 17% of patients, all but two with the 184V/I mutation. Among the 74 patients receiving lamivudine, the M184V/I mutation was detected in 13/74 (17.6%) patients. A wild-type codon at position 184 was detected in previous samples in all but two. The relative risk for virological failure was 2.55-fold higher in patients with the M184V/I mutation than in patients without detectable mutation (P=0.007). CONCLUSIONS: The M184V/I mutation is frequently selected during repeated treatment interruptions

Decay of cell-associated HIV-1 DNA correlates with residual replication in patients treated during acute HIV-1 infection

OBJECTIVES: To evaluate the decay rate of cell-associated HIV-1 RNA and DNA and to identify factors associated with residual viral load in patients treated at the time of primary HIV-1 infection. PATIENTS: A group of 15 patients adherent to highly active antiretroviral therapy (HAART) with sustained undetectable HIV-1 viremia for at least 24 months. METHODS: Viremia, cell-associated HIV-1 RNA and DNA in blood and lymph node mononuclear cells were measured using ultrasensitive assays. RESULTS: Viremia decreased rapidly in all patients; HIV RNA remained < 3 copies/ml in nine patients and fluctuated between 3 and 50 copies/ml in five patients and between 50 and 200 copies/ml in one patient. Decay rates of cell-associated RNA and DNA presented an inflexion point at 1 and 3 months, respectively: first-phase mean half-lives were 0.15 and 0.84 months, respectively, and second-phase mean half-lives were 13.7 and 6.6 months, respectively (95% confidence interval 4.4-13.8). The second phase decay rates were markedly slower, with a DNA decay rate that was highly associated with the mean levels of cell-associated RNA measured in blood from 6 to 33 months (P= 0.001) and in lymph nodes collected at 14 months (P= 0.02). CONCLUSIONS: The clearance of HIV-1 infected cells is correlated with the extent of viral replication as measured by cell-associated RNA levels in both blood and lymph nodes. Quantification of cell-associated RNA and DNA further defines treatment efficacy in 'aviremic' patients

La prophylaxie postexposition dans tous ses états

Every day physicians are confronted with situations that require evaluation concerning the indication for a post-exposition prophylaxis (PEP) for HIV or, less frequently, for hepatitis B (HBV). There is no specific prophylaxis for hepatitis C (HCV). In light of the experience gained in the domain of HIV in the last years, some international guidelines for PEP have been changed with regard to the choice of drugs and when to start PEP. This article attempts to resume the different factors contributing to the evaluation of PEP according to the local guidelines and to introduce the foreseen changes in the new Swiss-guidelines for PEP that will be released in autumn 2013

Response of HIV RNA to didanosine as a predictive marker of survival

OBJECTIVE: To evaluate whether early changes in viraemia in response to didanosine (ddI) predict death and occurrence of new AIDS-defining events. METHODS: Forty-three patients were followed during ddI treatment with sequential determinations of serum viraemia, mutations associated with drug resistance, CD4 counts and clinical evaluation. Patients were stratified into two groups of equal size, responders and nonresponders, using the median of individual changes in viraemia 1 month after initiation of ddI therapy. RESULTS: After 1 month of ddI, mean viraemia decreased by 0.35 log RNA copies/ml of serum (P < 0.001) in the population. A significant difference in survival (median, 14 and 35 months in nonresponders and responders, respectively; log rank, P = 0.004) and in the delay to the occurrence of new AIDS-defining events (median, 8 and 33 months in nonresponders and responders, respectively; log rank, P = 0.018) was observed. After stratification for presence of AIDS before starting ddI, viraemia response at 1 month remained predictive of both overall and AIDS-defining event-free survival (log rank, P = 0.0006 and P = 0.01). After a similar stratification for initial CD4, viraemia response still predicted overall survival (log rank, P = 0.009), but its predictive value for AIDS-defining event-free survival did not reach statistical significance (P = 0.12). High initial levels of HIV RNA, presence of mutation 215 or previous duration of zidovudine therapy were not predictive of survival. CONCLUSIONS: In patients treated with ddI, changes in viraemia at 1 month predict survival independently of initial AIDS diagnosis and initial CD4 counts