Simeprevir: a macrocyclic HCV protease inhibitor.

Simeprevir is a macrocyclic NS3/4A HCV protease inhibitor with potent activity against genotypes 1, 2, 4, 5 and 6 of the hepatitis C virus (HCV). Phase II and III studies of simeprevir combined with pegylated interferon (peg-IFN) and ribavirin (RBV) demonstrated that the combination was safe and effective in HCV genotype 1 patients, with more than 75% of treatment-naive patients attaining a sustained virological response (SVR). Simeprevir is administered once daily as a single 150-mg capsule. It has a moderate drug interaction potential, but less than that of the first-generation HCV protease inhibitors. Based on positive results from the product's phase III clinical program, simeprevir was approved and launched in Japan, the U.S. and Canada in late 2013 for use in combination with peg-IFN/RBV in HCV genotype 1 infections. Phase II interferon-free studies of simeprevir are ongoing.

Current status of treatment for chronic hepatitis C virus infection.

Chronic hepatitis C virus (HCV) infection is responsible for substantial mortality and morbidity worldwide. Until recently, the standard of care for the treatment of chronic HCV infection had been a combination of pegylated interferon (peg-IFN) and ribavirin (RBV). The recent availability of two directly acting agents, telaprevir and boceprevir, has led to significantly improved outcomes for those patients with HCV genotype 1. Unfortunately, each of these agents must be combined with peg-IFN and RBV for optimal efficacy, and substantial treatment-related toxicity continues to challenge clinicians. However, the drug development pipeline for chronic HCV infection is very robust and the emergence of new therapies and therapeutic strategies in the near future for managing chronic HCV infection is eagerly anticipated.

Selective increases in HIV-specific neutralizing antibody and partial reconstitution of cellular immune responses during prolonged, successful drug therapy of HIV infection.

Because the immune response to HIV depends on viral gene expression, we examined the HIV-specific immune responses in persons whose viral load after highly active antiretroviral therapy (HAART) was <400 on at least 3 occasions over a 12-month interval. Eleven patients were identified. While there was little change in mean HIV-binding antibody (Ab) titers in this group, two persons mounted increases in HIV envelope-specific binding antibody. Neutralizing antibody (NAb) titers against a panel of HIV-1 primary isolates (BZ167, US1, and CM237) increased post-HAART (80% neutralization titer against US1, p = 0.06; against CM237, p = 0.04). The two persons with large increases in binding antibody also had increases in primary isolate NAb. Roughly half of HAART recipients had significant increases in neutralizing antibody to the primary isolates US1 and CM237. Compared with CD4-matched, non-HAART controls, there were significant increases in NAb against the subtype B primary isolate US1 (p < 0.0009); no increases were seen against more easily neutralized primary isolate BZ167. There were no differences after HAART in antibody-directed cellular cytotoxicity (ADCC). HAART resulted in a partial restoration of lymphoproliferative responses to recall antigens (tetanus and diphtheria). New responses developed to HIV Gag p24. No patient responded to HIV Env gp160 or gp120 either before or after HAART. The data underscore the lack of functional reconstitution of HIV-specific, CD4-mediated responses despite durable suppression of viral replication. In the setting of stable anti-HIV Ab levels, the development of increased NAb in certain individuals suggests that control of the virus by HAART may assist in immune control of HIV.

Methods of Culturing HIV-1 from Semen.

The predominant mode of transmission of HIV-1 worldwide is sexual intercourse. Therefore, there has been growing interest in studying HIV-1 in genital secretions. Given the urgency to develop a vaccine to protect against HIV-1, techniques have been developed to isolate and quantitate HIV-1 from genital secretions.

Quantitation of HIV-1 RNA in Genital Secretions.

The continuing spread of the HIV-1 epidemic worldwide has stimulated efforts to develop vaccines and decrease transmission of HIV-1 as noted in Chapter 8 . Key to this effort is the characterization of the qualities of HIV-1 in genital secretions. Seminal cell and seminal plasma culture have been used to isolate HIV-1 from semen but have low recovery rates of 9-50% (1-11). Culture of vaginal cells have also had low recovery rates of 0-30% (12-14). In an attempt to overcome this problem, HIV-1 has been evaluated in genital secretions using polymerase chain reaction (PCR) techniques. Compared to culture techniques, PCR techniques, both DNA and RNA, have had a higher recovery rate of HIV-1 from genital secretions (2,3,7,9-11,13-25).

High levels of human immunodeficiency virus type 1 in blood and semen of seropositive men in sub-Saharan Africa.

High levels of human immunodeficiency virus type 1 (HIV-1) replication, as reflected in HIV-1 RNA concentrations in blood and semen, probably contribute to both rapid disease progression and enhanced sexual transmission. Semen and blood were collected from 49 Malawian and 61 US and Swiss (US/Swiss) HIV-1-seropositive men with similar CD4 cell counts and no urethritis or exposure to antiretroviral drugs. Median seminal plasma and blood plasma HIV-1 RNA concentrations were >3-fold (P = .034) and 5-fold (P = .0003) higher, respectively, in the Malawian men. Similar differences were observed in subsets of the Malawian and US/Swiss study groups matched individually for CD4 cell count (P = .035 and P < .002, respectively). These observations may help explain the high rates of HIV-1 sexual transmission and accelerated HIV-1 disease progression in sub-Saharan Africa.

Effect of antiviral treatment on the shedding of HIV-1 in semen.

OBJECTIVE: The potential role of antiretroviral treatment on the infectiousness of HIV-1-infected men was examined by studying the effect of antiviral treatment on the shedding of HIV-1 in semen. METHODS: Forty-four patients enrolled in various treatment protocols were asked to donate a semen sample before they began a new antiviral treatment and at a follow-up visit after 6 to 15 weeks of treatment. Since most patients were on blinded protocols, patients were stratified by response of blood viral load. The effect of each patient's treatment was classified as good (n = 24), fair (n = 8) and marginal (n = 13) by measurement of the HIV RNA reduction in blood plasma (> 1.0 log10; 0.5-1.0 log10 and < 0.5 log10 HIV RNA copies/ml reduction, respectively). The effect of treatment on shedding of HIV-1 in semen was documented by the reduction of HIV RNA concentration in seminal plasma and by quantitative HIV-1 seminal cell culture. RESULTS: Overall, antiviral treatment resulted in a significant fall in the viral load in semen (RNA and culture) that paralleled the reduction of viral load in blood. More pronounced reductions of HIV RNA in semen were observed as the effectiveness of treatment on blood HIV RNA levels increased (median drop from baseline 0, 0.3 log10 and 0.8 log10 RNA copies/ml in patients with marginal, fair and good treatment effect, respectively). Thirteen patients lost detectable HIV RNA in blood on treatment and all of these had undetectable levels of HIV-1 in semen by culture and RNA analysis at follow-up. In 19 of the 31 patients (62%) who still had HIV RNA in their blood during treatment, semen HIV levels were below detection in semen at follow-up. CONCLUSIONS: Treatment-induced changes of HIV RNA concentration in blood are generally associated with a corresponding change in seminal HIV RNA: If confirmed in larger studies, potent antiretroviral therapy might reduce the spread of HIV-1.

Quantification of HIV in semen: correlation with antiviral treatment and immune status.

OBJECTIVE: This study examined the concentration of HIV in semen and the effects of biological factors on HIV excretion. METHODS: Semen samples from 101 men at different stages of the disease were evaluated by quantitative HIV culture and HIV RNA detection. Blood plasma samples were available from 56 patients. The effects of CD4 and CD8 count, blood plasma RNA levels, treatment status and clinical staging on the shedding of HIV were evaluated. RESULTS: HIV RNA levels in semen correlated with quantitative HIV culture of seminal cells and a strong association of positive seminal cell culture with high RNA levels was observed. CD4 count and antiviral treatment were inversely correlated with the concentration of HIV in semen. Blood plasma HIV RNA values were correlated with HIV RNA levels in semen, although some patients had highly discrepant results. CONCLUSIONS: The strong correlation between seminal cell culture and concentration of HIV RNA in seminal plasma suggested that HIV detected in seminal plasma was released by productively infected cells in the male genital tract. The study showed that the concentration of HIV in semen, which was likely to be correlated with HIV infectivity, was a function of the immune status of the HIV-infected individual. The results suggested that antiviral therapy may have reduced the concentration of HIV in semen.

Effects of reverse transcriptase inhibitor therapy on the HIV-1 viral burden in semen.

HIV-1 infection continues to spread worldwide, primarily through sexual intercourse. Because semen is a major vehicle for transmission of HIV-1, we evaluated the effects of reverse transcriptase inhibitor therapy on the amount of HIV-1 in semen. The semen and blood of 11 HIV-1-infected men (i.e. treatment group) were collected before the initiation of reverse transcriptase inhibitor therapy and then 8 to 18 weeks after initiation of therapy. The semen and blood of another 11 HIV-1-infected men (i.e., longitudinal group), who were not on or had no change in antiretroviral therapy for at least 2 months before study entry, were collected at approximately 2-week intervals for 10 to 26 weeks. In the treatment group, 82% of the seminal plasma HIV-1 RNA levels decreased from baseline after 8 to 18 weeks of therapy (median reduction of 1.01 log10, p = 0.01), and 100% of the blood plasma RNA levels decreased from baseline over the same period (median reduction of 0.92 log10, p = 0.003). Five of these patients were followed for at least 52 weeks and had a median seminal plasma HIV-1 RNA level of 0.66 log10 below baseline at 1 year. All subjects in the treatment group with positive cultures at baseline (50%) had negative cultures or a lower infectious units per ejaculate at the 8- to 18-week follow-up examinations. The HIV-1 RNA levels in blood and semen of the longitudinal group did not change significantly over 10 to 26 weeks. Initiation of reverse transcriptase inhibitor therapy effectively reduces shedding of HIV-1 in semen and may therefore reduce the spread of infection within populations.

Quantitation of human immunodeficiency virus type 1 RNA in cell free seminal plasma: comparison of NASBA with Amplicor reverse transcription-PCR amplification and correlation with quantitative culture.

Human immunodeficiency virus type 1 (HIV-1) is transmitted by infected males in semen. However, the inoculum required for infection is unknown. The ability to collect such information will rely on the availability of reliable quantitative assays of HIV-1 in semen. We examined the comparative performance of NASBA and Amplicor Monitor RT-PCR in quantifying HIV-1 RNA in cell free seminal plasma from seropositive men and correlated the results obtained with viral titres measured by a seminal cell quantitative microculture (QMC) assay. Of samples analysed, 68% and 56% by both NASBA and RT-PCR contained measurable HIV-1 RNA, respectively. Amplification inhibition frequently affected RT-PCR but not NASBA. Excluding samples with complete RT-PCR inhibition, there was 90% qualitative concordance and a strong positive correlation (r = 0.86) of RNA levels measured by the two methods. Comparison of the concentration of HIV-1 RNA in seminal plasma samples, as measured by NASBA, with QMC viral titres indicated that RNA levels probably reflect the infectiousness of whole semen. NASBA is a reliable technique for quantitating HIV-1 RNA in seminal plasma and should become a valuable tool in the study of factors that influence the sexual transmission of HIV.