Petronella Muresan

Identification of Ongoing Human Immunodeficiency Virus Type 1 (HIV-1) Replication in Residual Viremia during Recombinant HIV-1 Poxvirus Immunizations in Patients with Clinically Undetectable Viral Loads on Durable Suppressive Highly Active Antiretroviral Therapy

ABSTRACT In most human immunodeficiency virus type 1 (HIV-1)-infected individuals who achieve viral loads of <50 copies/ml during highly active antiretroviral therapy (HAART), low levels of plasma virus remain detectable for years by ultrasensitive methods. The relative contributions of ongoing virus replication and virus production from HIV-1 reservoirs to persistent low-level viremia during HAART remain controversial. HIV-1 vaccination of HAART-treated individuals provides a model for examining low-level viremia, as immunizations may facilitate virus replication and sequence evolution. In a phase 1 trial of modified vaccinia virus Ankara/fowlpox virus-based HIV-1 vaccines in 20 HIV-infected young adults receiving HAART, we assessed the prevalence of low-level viremia and sequence evolution, using ultrasensitive viral load (<6.5 copies/ml) and genotyping (five-copy sensitivity) assays. Viral evolution, consisting of new drug resistance mutations and novel amino acid changes within a relevant HLA-restricted allele (e.g., methionine, isoleucine, glutamine, or arginine for leucine at position 205 of RT), was found in 1 and 3 of 20 subjects, respectively. Sequence evolution was significantly correlated with levels of viremia of between 6.5 and <50 copies/ml (P = 0.03) and was more likely to occur within epitopes presented by relevant HLA alleles (P < 0.001). These findings suggest that ongoing virus replication contributes to low-level viremia in patients on HAART and that this ongoing replication is subject to CD8+ T-cell selective pressures.

HIV-1 vaccine induced immune responses in newborns of HIV-1 infected mothers.

Objective:Breast milk transmission continues to account for a large proportion of cases of mother-to-child transmission of HIV-1 worldwide. An effective HIV-1 vaccine coupled with either passive immunization or short-term antiretroviral prophylaxis represents a potential strategy to prevent breast milk transmission. This study evaluated the safety and immunogenicity of ALVAC HIV-1 vaccine with and without a subunit envelope boost in infants born to HIV-1-infected women. Design:Placebo-controlled, double-blinded study. Methods:Infants born to HIV-1-infected mothers in the US were immunized with a prime-boost regimen using a canarypox virus HIV-1 vaccine (vCP1452) and a recombinant glycoprotein subunit vaccine (rgp120). Infants (n = 30) were randomized to receive: vCP1452 alone, vCP1452 + rgp120, or corresponding placebos. Results:Local reactions were mild or moderate and no significant systemic toxicities occurred. Subjects receiving both vaccines had gp120-specific binding serum antibodies that were distinguishable from maternal antibody. Repeated gp160-specific lymphoproliferative responses were observed in 75%. Neutralizing activity to HIV-1 homologous to the vaccine strain was observed in 50% of the vCP1452 + rgp120 subjects who had lost maternal antibody by week 24. In some infants HIV-1-specific proliferative and antibody responses persisted until week 104. HIV-1-specific cytotoxic T lymphocyte responses were detected in two subjects in each treatment group; the frequency of HIV-1 specific cytotoxic T lymphocyte responses did not differ between vaccine and placebo recipients. Conclusion:The demonstration of vaccine-induced immune responses in early infancy supports further study of HIV-1 vaccination as a strategy to reduce breast milk transmission.

Safety and Immunogenicity of an HIV-1 Recombinant Canarypox Vaccine in Newborns and Infants of HIV-1–Infected Women

Pediatric AIDS Clinical Trials Group protocol 326 is a study of 2 formulations of recombinant canarypox ALVAC vaccine (vCP205) against human immunodeficiency virus type 1 (HIV-1). HIV-1-exposed infants were randomized to receive 1 of 2 formulations of vCP205 or placebo at birth and 4, 8, and 12 weeks. The vaccines were safe. Lymphoproliferative responses were detected at > or =2 time points in 44%-56% of vaccinees and none of the placebo recipients. A cytotoxic T lymphocyte response on at least 1 occasion was detected in 62.5% of infants in cohort 1 (10(6.08) median tissue culture dose [TCID(50)] vaccine formulation) and 44% of infants in cohort 2 (10(6.33) TCID(50) vaccine formulation). Rare mucosal immunoglobulin A responses and no measurable vaccine-elicited serum antibodies were detected. In children, vCP205 appeared to be safe and immunogenic.

Safety and immunogenicity of recombinant poxvirus HIV-1 vaccines in young adults on highly active antiretroviral therapy

A trial to evaluate the safety and immunogenicity of recombinant modified vaccinia Ankara (MVA) and fowlpox (FP) vectors expressing multiple HIV-1 proteins was conducted in twenty HIV-1 infected youth with suppressed viral replication on HAART. The MVA and FP-based multigene HIV-1 vaccines were safe and well tolerated. Increased frequencies of HIV-1 specific CD4+ proliferative responses and cytokine secreting cells were detected following immunization. Increased frequencies and breadth of HIV-1 specific CD8 T-cell responses were also detected. Plasma HIV-1-specific antibody levels and neutralizing activity were unchanged following vaccination. Poxvirus-based vaccines may merit further study in therapeutic vaccine protocols.

Impaired Immunity to Recall Antigens and Neoantigens in Severely Immunocompromised Children and Adolescents during the First Year of Effective Highly Active Antiretroviral Therapy

BACKGROUND We studied whether severely immunocompromised, human immunodeficiency virus (HIV)-infected children who were beginning highly active antiretroviral therapy (HAART) or changing HAART regimens could spontaneously respond to a recall antigen (tetanus toxoid [TT] vaccine) or respond to a recall antigen and neoantigen (hepatitis A virus [HAV] vaccine) after 3 vaccinations. METHODS A total of 46 children who had CD4 cell percentages <15% and who demonstrated a >0.75-log reduction in plasma HIV RNA levels within 4 weeks of starting HAART were randomized to receive vaccinations with either TT or HAV vaccines during the first 6 months of HAART. Study subjects then received the alternate vaccine during the next 6 months of HAART. RESULTS Despite the early decline in viremia and the later increase in the percentage of CD4 T cells, spontaneous recovery of cell-mediated immunity (CMI) was not seen for TT. Serologic responses to TT required 3 vaccinations and were comparable in both groups. Serologic responses to HAV were infrequent and of low titer, although the group that received HAV vaccine after receiving TT vaccine performed somewhat better. CMI to HAV was virtually absent. CONCLUSIONS Severely immunocompromised children who are receiving HAART develop CMI and antibody to a recall antigen independent of the timing of vaccination, but they require a primary series of vaccinations. Antibodies to a neoantigen, HAV, developed when vaccination was delayed after initiation of HAART. CMI to a neoantigen was difficult to establish. TRIAL REGISTRATION Clinicaltrials.gov identifier: NCT00004735/PACTG P1006 .

Effect of therapeutic HIV recombinant poxvirus vaccines on the size of the resting CD4+ T-cell latent HIV reservoir

Objectives:Therapeutic HIV vaccinations may alter the size of the resting memory CD4+ T-cell latent HIV reservoir as HIV establishes latency when memory responses are formed, including those toward HIV. Alternatively, latently infected CD4+ T cells maybe killed, while exiting the reservoir upon activation. Methods:The effect of therapeutic immunization with modified vaccinia Ankara and Fowlpox-based HIV vaccines on the latent reservoir was examined in 19 young adults who were receiving effective antiretroviral therapy. Correlations between size of the reservoir [measured in infectious units per million (IUPM)] resting CD4+ T cells and HIV-specific immune responses, including immune activation were examined. Decay of the reservoir was assessed using random-effects model. Results:A modest transient decrease in the size of the reservoir was observed at week 40 [mean −0.31 log10 IUPM (95% confidence interval: −0.60 to −0.03; P = 0.03] following HIV vaccinations. The estimated half-life (T1/2) of the reservoir during the 40 weeks following vaccination was 9.8 months and statistically different from zero (P = 0.02), but 35.3 months and not different from zero (P = 0.21) over 72 weeks of study. Latent reservoir size at baseline was not correlated with HIV-specific CD4+, CD8+ responses or immune activation, but became correlated with CD4+ IFN&ggr; (r = 0.54, P = 0.02) and IL-2 responses at 6 weeks after immunization (r = 0.48, P = 0.04). Conclusion:Therapeutic HIV vaccinations led to a transient increase in decay of latently infected CD4+ T cells. Further studies of therapeutic HIV vaccines may provide important insights into facilitating decay of the latent reservoir.

A Chewable Pediatric Fixed-dose Combination Tablet of Stavudine, Lamivudine, and Nevirapine: Pharmacokinetics and Safety Compared With the Individual Liquid Formulations in Human Immunodeficiency Virus-infected Children in Thailand

Background: Pediatric fixed-dose combinations (FDCs) are needed to facilitate antiretroviral therapy in children. We evaluated the relative bioavailability, safety, and therapeutic adequacy of a novel chewable pediatric FDC tablet of stavudine (7 mg), lamivudine (30 mg), and nevirapine (50 mg), referred to as GPO-VIR S7, and compared it with the individual original brand-name liquid formulations in human immunodeficiency virus-infected Thai children. Methods: The International Maternal Pediatric Adolescent AIDS Clinical Trials group (IMPAACT) P1056 study was a phase I/II, 2-arm, randomized, open-label, multidose pharmacokinetic cross-over study. Children ≥6 to ≤30 kg receiving nevirapine-based HAART for at least 4 weeks were randomized to receive GPO-VIR S7 chewable tablets or the equivalent liquid formulations. Children were stratified by weight and dosing was weight-based. Intensive 12-hour blood sampling was performed on day 28, and subjects then crossed-over to the alternate formulation at equal doses with identical 12-hour sampling on day 56. Pharmacokinetic indices were determined by noncompartmental analysis. Results: Thirty-four children completed the study. While taking Government Pharmaceutical Organization (GPO)-VIR S7 the geometric mean (90% CI) area under the curve was 1.54 &mgr;g·hr/mL (1.42–1.67) for stavudine, 6.39 (5.82–7.00) for lamivudine, and 74.06 (65.62–83.60) for nevirapine. Nevirapine drug exposure for GPO-VIR S7 was therapeutically adequate. Geometric mean area under the curve ratios (90% CI) of GPO-VIR S7/liquid formulation for stavudine, lamivudine, and nevirapine were 0.97 (0.92–1.02), 1.41 (1.30–1.53), and 1.08 (1.04–1.13), respectively. No serious drug-related toxicity was reported. Conclusions: The chewable FDC was safe and provided therapeutically adequate plasma drug exposures in human immunodeficiency virus-infected children. Substituting the FDC for liquid formulations can simplify antiretroviral therapy.

Pharmacokinetics and safety of a new paediatric fixed-dose combination of zidovudine/lamivudine/nevirapine in HIV-infected children.

BACKGROUND Alternatives to the available stavudine-containing paediatric fixed-dose combination (FDC) tablets are rapidly needed due to concerns regarding the cumulative toxicity of long-term stavudine exposure. We report the bioavailability and short-term safety of a novel paediatric FDC tablet of zidovudine (ZDV)/lamivudine (3TC)/nevirapine (NVP; 30/15/28 mg) in HIV-infected children. METHODS In this Phase I/II open-label pharmacokinetic study, 42 children weighing 6-30 kg treated with NVP-based HAART for ≥4 weeks were randomized to receive the FDC tablets (GPO-VIR Z30) or the liquid formulations. Dosing was weight-based. Intensive 12-h blood sampling was performed after 2 weeks; subjects then crossed-over to the alternate formulation at equal doses and sampling repeated 2 weeks later. Pharmacokinetic parameters were determined by non-compartmental analysis. Buccal-swab samples were collected for cytochrome P450 (CYP)2B6 polymorphism analysis. RESULTS With the FDC tablet, the geometric mean (90% CI) area under the curve (AUC) for ZDV, 3TC and NVP was 1.58 (1.49-1.68), 7.78 (7.38-8.19) and 68.88 (62.13-76.36) μg•h/ml, respectively. Rules for NVP therapeutic inadequacy were defined a priori, and despite lower NVP exposure with the tablet (P<0.001), the levels remained therapeutically adequate. ZDV AUC was similar between formulations. 3TC exposure was significantly higher with the tablet but comparable to historical data in adults and children taking branded tablets. While receiving the tablet, NVP AUC in children with CYP2B 516 GG (45%), GT (45%) and TT (10%) genotypes were 67.0, 74.5 and 106.4 μg•h/ml, respectively (P=0.04). CONCLUSIONS Disparities in drug exposure between formulations were observed; however, the FDC tablet delivered therapeutically adequate exposures of each drug and could well play an important role in simplifying antiretroviral treatment for children.

Infant HIV Type 1 gp120 Vaccination Elicits Robust and Durable Anti-V1V2 Immunoglobulin G Responses and Only Rare Envelope-Specific Immunoglobulin A Responses

BACKGROUND Infant responses to vaccines can be impeded by maternal antibodies and immune system immaturity. It is therefore unclear whether human immunodeficiency virus type 1 (HIV-1) vaccination would elicit similar responses in adults and infants. METHOD HIV-1 Env-specific antibody responses were evaluated in 2 completed pediatric vaccine trials. In the Pediatric AIDS Clinical Trials Group (PACTG) 230 protocol, infants were vaccinated with 4 doses of Chiron rgp120 with MF59 (n=48), VaxGen rgp120 with aluminum hydroxide (alum; n=49), or placebo (n=19) between 0 and 20 weeks of age. In PACTG 326, infants received 4 doses of ALVAC-HIV-1/AIDSVAX B/B with alum (n=9) or placebo (n=13) between 0 and 12 weeks of age. RESULTS By 52 weeks of age, the majority of maternally acquired antibodies had waned and vaccine Env-specific immunoglobulin G (IgG) responses in vaccinees were higher than in placebo recipients. Chiron vaccine recipients had higher and more-durable IgG responses than VaxGen vaccine recipients or ALVAC/AIDSVAX vaccinees, with vaccine-elicited IgG responses still detectable in 56% of recipients at 2 years of age. Remarkably, at peak immunogenicity, the concentration of anti-V1V2 IgG, a response associated with a reduced risk of HIV-1 acquisition in the RV144 adult vaccine trial, was 22-fold higher in Chiron vaccine recipients, compared with RV144 vaccinees. CONCLUSION As exemplified by the Chiron vaccine regimen, vaccination of infants against HIV-1 can induce robust, durable Env-specific IgG responses, including anti-V1V2 IgG.

Infant HIV-1 gp120 vaccination elicits robust and durable anti-V1V2 IgG responses and only rare Envelope-specific IgA responses

BACKGROUND Infant responses to vaccines can be impeded by maternal antibodies and immune system immaturity. It is therefore unclear whether human immunodeficiency virus type 1 (HIV-1) vaccination would elicit similar responses in adults and infants. METHOD HIV-1 Env-specific antibody responses were evaluated in 2 completed pediatric vaccine trials. In the Pediatric AIDS Clinical Trials Group (PACTG) 230 protocol, infants were vaccinated with 4 doses of Chiron rgp120 with MF59 (n=48), VaxGen rgp120 with aluminum hydroxide (alum; n=49), or placebo (n=19) between 0 and 20 weeks of age. In PACTG 326, infants received 4 doses of ALVAC-HIV-1/AIDSVAX B/B with alum (n=9) or placebo (n=13) between 0 and 12 weeks of age. RESULTS By 52 weeks of age, the majority of maternally acquired antibodies had waned and vaccine Env-specific immunoglobulin G (IgG) responses in vaccinees were higher than in placebo recipients. Chiron vaccine recipients had higher and more-durable IgG responses than VaxGen vaccine recipients or ALVAC/AIDSVAX vaccinees, with vaccine-elicited IgG responses still detectable in 56% of recipients at 2 years of age. Remarkably, at peak immunogenicity, the concentration of anti-V1V2 IgG, a response associated with a reduced risk of HIV-1 acquisition in the RV144 adult vaccine trial, was 22-fold higher in Chiron vaccine recipients, compared with RV144 vaccinees. CONCLUSION As exemplified by the Chiron vaccine regimen, vaccination of infants against HIV-1 can induce robust, durable Env-specific IgG responses, including anti-V1V2 IgG.