Replicating viral vectors as HIV vaccines Summary Report from IAVI Sponsored Satellite Symposium, International AIDS Society Conference, July 22, 2007

At the International AIDS Society Conference on Pathogenesis, Treatment and Prevention held in Sydney, Australia, in July 2007, the International AIDS Vaccine Initiative (IAVI) convened a satellite symposium entitled 'Accelerating the Development of Replicating Viral Vectors for AIDS Vaccines.' Its purpose was to highlight the rationale for accelerating the development of replicating viral vectors for use as vaccines against HIV-1, and to bring together vaccine scientists, regulatory officials, and public health specialists from industrialized and developing nations to discuss the major issues facing the development and testing of replicating viral vector-based vaccines.     

Live attenuated HIV as a vaccine for AIDS: pros and cons

Anti-HIV-1 vaccines must be safe and effective. In macaques, live attenuated simian immunodeficiency viruses have provided the best protection to date. Similar results were obtained earlier in murine leukemia virus systems in which protection correlated with cellular immunity but not with neutralizing antibodies. Attenuated primate lentiviruses tested thus far have been replication-impaired but may still harbor genetic determinants encoding virulence. Other safety issues concern insertional oncogenesis, genetic instability, vertical transmission and differential pathogenicity in adults and newborns, and viral persistence with possible reactivation during intercurrent illness. Long term safety studies are needed to assess the risks associated with live attenuated retrovirus vaccines.     

Peptides as viral vaccines: lessons from experiments with foot-and-mouth disease virus

The highly variable sequence encompassing amino acids 141–160 of VP1, one of the four capsid proteins of foot-and-mouth disease virus, elicits neutralizing antibodies in a range of experimental animals. The sequence has been synthesized chemically by Merrifield's solid phase method and biochemically as part of different fusion proteins. By incorporating the peptide into the core protein of hepatitis B virus, particles are produced which elicit levels of neutralizing antibody approaching those obtained with the intact virus particle.This paper was presented at the IUMS Symposium on New Developments in Diagnosis and Control of Infectious Diseases held in conjunction with the Eighth International Congress of Virology, Berlin, Germany, 24–31 August 1990.     

Cross-species transfer of viruses: implications for the use of viral vectors in biomedical research, gene therapy and as live-virus vaccines

All living organisms are continuously exposed to a plethora of viruses. In general, viruses tend to be restricted to the natural host species which they infect. From time to time viruses cross the host-range barrier expanding their host range. However, in very rare cases cross-species transfer is followed by the establishment and persistence of a virus in the new host species, which may result in disease. Recent examples of viruses that have crossed the species barrier from animal reservoirs to humans are hantavirus, haemorrhagic fever viruses, arboviruses, Nipah and Hendra viruses, avian influenza virus (AI), monkeypox virus, and the SARS-associated coronavirus (SARS-CoV). The opportunities for cross-species transfer of mammalian viruses have increased in recent years due to increased contact between humans and animal reservoirs. However, it is difficult to predict when such events will take place since the viral adaptation that is needed to accomplish this is multifactorial and stochastic. Against this background the intensified use of viruses and their genetically modified variants as viral gene transfer vectors for biomedical research, experimental gene therapy and for live-vector vaccines is a cause for concern. This review addresses a number of potential risk factors and their implications for activities with viral vectors from the perspective of cross-species transfer of viruses in nature, with emphasis on the occurrence of host-range mutants resulting from either cell culture or tropism engineering. The issues are raised with the intention to assist in risk assessments for activities with vector viruses.     

The HIV Tat protein transduction domain improves the biodistribution of beta-glucuronidase expressed from recombinant viral vectors.

Treatment of inherited genetic diseases of the brain remains an intractable problem. Methods to improve the distribution of enzymes that are injected or expressed from transduced cells will be required for many human brain therapies. Recent studies showed that a peptide, the protein transduction domain (PTD) from HIV Tat, could improve the distribution of cytoplasmic reporter proteins when administered systemically as fusion proteins or cross-linked chimeras. The utility of this motif for noncytoplasmic proteins has not been determined. Here, we tested how the Tat motif affected uptake and biodistribution of the lysosomal enzyme beta-glucuronidase, the protein deficient in the disease mucopolysaccharidosis VII, when expressed from viral vectors. The Tat motif allowed for mannose-6-phosphate (M6P) independent uptake in vitro and significantly increased the distribution of beta-glucuronidase secreted from transduced cells after intravenous or direct brain injection in mice of recombinant vectors. Thus, enzymes modified to contain protein transduction motifs may represent a general strategy for improving the distribution of secreted proteins following in vivo gene transfer.     

A conference report from "Down Under": Talking autophagy at OzBio2010

OzBio2010 was held at the Melbourne Convention and Exhibition Centre, September 26 to October 1, 2010. This international conference catered to researchers in several fields having complementary interests including biochemistry, molecular biology, cell biology, plant physiology and health-related research. It was held under the auspices of two major international scientific societies, IUBMB and FAOBMB, and the ComBio2010 collective (representing nine professional societies and groupings from Australia). A number of pre-eminent speakers presented at plenary sessions and in a wide array of specialist symposia. One of the plenary sessions and a specialist symposium highlighted autophagy-related topics.     

AIDS, policy and bioethics: ethical dilemmas facing China in HIV prevention: a report from China

The present situation of the HIV/AIDS epidemic is very grim in China. The probability of China becoming a country with a high prevalence of HIV/AIDS cannot be excluded because there have been factors which promote the wide spread of HIV if we fail to take timely action to prevent it at the opportune moment. However, China's HIV prevention policy is inadequate. Health professionals and programmers believed that they could take a conventional public health approach to cope with the HIV epidemic. They simply ignored the fact that HIV infection is an epidemic so special that their approach is not effective to deter the epidemic. Many health professionals and programmers bypassed ethical issues that had emerged in the prevention of the HIV epidemic. Even some health educators, sexologists and officials believe that `AIDS is the punishment for promiscuity', and this belief has led to discrimination and stigmatization of AIDS patients, HIV positive people, their family members and high risk groups. Although homosexuality is not illegal, the police can always find any reason to detain homosexuals. A difficult ethical issue is about the laws prohibiting prostitution and drug use in China which force prostitutes and intravenous drug users underground, giving them no chance to access information, education and the services needed to protect them. The dilemma facing China is whether to stay with a restrictive policy for the reason of ideology cleansing or to turn to a more supportive policy. It is necessary to have some change in the ethical framework to evaluate the action in HIV prevention. Tolerance should be the first ethical principle.     

Randomized controlled trials of HIV/AIDS prevention and treatment in Africa: results from the Cochrane HIV/AIDS Specialized Register

Introduction

To effectively address HIV/AIDS in Africa, evidence on preventing new infections and providing effective treatment is needed. Ideally, decisions on which interventions are effective should be based on evidence from randomized controlled trials (RCTs). Our previous research described African RCTs of HIV/AIDS reported between 1987 and 2003. This study updates that analysis with RCTs published between 2004 and 2008.

Objectives

To describe RCTs of HIV/AIDS conducted in Africa and reported between 2004 and 2008.

Methods

We searched the Cochrane HIV/AIDS Specialized Register in September 2009. Two researchers independently evaluated studies for inclusion and extracted data using standardized forms. Details included location of trials, interventions, methodological quality, location of principal investigators and funders.

Results

Our search identified 834 RCTs, with 68 conducted in Africa. Forty-three assessed prevention-interventions and 25 treatment-interventions. Fifteen of the 43 prevention RCTs focused on preventing mother-to-child HIV transmission. Thirteen of the 25 treatment trials focused on opportunistic infections. Trials were conducted in 16 countries with most in South Africa (20), Zambia (12) and Zimbabwe (9). The median sample size was 628 (range 33-9645). Methods used for the generation of the allocation sequence and allocation concealment were adequate in 38 and 32 trials, respectively, and 58 reports included a CONSORT recommended flow diagram. Twenty-nine principal investigators resided in the United States of America (USA) and 18 were from African countries. Trials were co-funded by different agencies with most of the funding obtained from USA governmental and non-governmental agencies. Nineteen pharmaceutical companies provided partial funding to 15 RCTs and African agencies co-funded 17 RCTs. Ethical approval was reported in 65 trials and informed consent in 61 trials.

Conclusion

Prevention trials dominate the trial landscape in Africa. Of note, few principal investigators and funders are from Africa. These findings mirror our previous work and continue to indicate a need for strengthening trial research capacity in Africa.     

Tracking the evolution of HIV/AIDS in China from 1989-2009 to inform future prevention and control efforts

Background

To determine policy implications, this analysis tracks the evolution of HIV/AIDS infection across China to understand current trends and potential risk factors.

Methods and Principal Findings

A retrospective study with spatial analytical model and multilevel spatial models was conducted among 326,157 HIV/AIDS cases reported from 1989–2009. The results indicate that the distribution of HIV/AIDS was clustered at the county level with different directional distributions across China from 2003 to 2009. Compared to 2003, by 2009 there was a 122% increase in HIV cases among rural residents, 294% increase among urban residents, 211% increase among migrants, and 237% increase among permanent residents. The overall proportion of HIV by different routes of transmission showed dramatic changes with a 504% increase in sexual transmission of HIV, 90% decrease in blood/plasma transmission, and 35% decrease in injecting drug user transmission. Sexual transmission was the major transmission route among women (44%) and the elderly (59% in men, 44% in women) as well as among permanent (36%) and urban residents (33%). Among those <65 years old, women increased more than men, but among those ≥65 years, men increased more than women. Migrants contributed to the variance of HIV infection between counties but not within counties. The length of highway and urbanization combined with illiteracy were risk factors for HIV/AIDS.

Conclusions/Significance

Rates of HIV/AIDS among permanent urban residents, particularly women and elderly men, have increased significantly in recent years. To prevent HIV from spreading further among the general population, additional attention should be paid to these populations as well as to migrants.     

Co-lethality studied as an asset against viral drug escape: the HIV protease case

Background  

Co-lethality, or synthetic lethality is the documented genetic situation where two, separately non-lethal mutations, become lethal when combined in one genome. Each mutation is called a “synthetic lethal” (SL) or a co-lethal. Like invariant positions, SL sets (SL linked couples) are choice targets for drug design against fast-escaping RNA viruses: mutational viral escape by loss of affinity to the drug may induce (synthetic) lethality.     

Worldwide survey of AIDS vaccine challenge studies in nonhuman primates: vaccines associated with active and passive immune protection from live virus challenge.

An AIDS Vaccine Surveillance System (AVSS) was designed and implemented to track the rapidly growing international database supporting the development of promising AIDS vaccines. Both preclinical nonhuman primate (NHP) and clinical human trials are tracked by the AVSS. This report presents summary data generated from the AVSS on the NHP AIDS vaccine/live virus challenge studies only. Summary data on more than 100 preclinical HIV/SIV vaccines are presented within the framework of 1) 13 arbitrary Vaccine Types, 2) studies grouped by animal model (i.e., chimpanzee/HIV-1, and macaque/SIV, HIV-2), and 3) immunization approach (i.e., active and passive). Systematic and timely presentations of these summary data, both here and in future reports, aim to promote a clearer understanding of both earlier and more recent preclinical AIDS vaccine developments.     

Therapeutic DNA vaccine induces broad T cell responses in the gut and sustained protection from viral rebound and AIDS in SIV-infected rhesus macaques

Immunotherapies that induce durable immune control of chronic HIV infection may eliminate the need for life-long dependence on drugs. We investigated a DNA vaccine formulated with a novel genetic adjuvant that stimulates immune responses in the blood and gut for the ability to improve therapy in rhesus macaques chronically infected with SIV. Using the SIV-macaque model for AIDS, we show that epidermal co-delivery of plasmids expressing SIV Gag, RT, Nef and Env, and the mucosal adjuvant, heat-labile E. coli enterotoxin (LT), during antiretroviral therapy (ART) induced a substantial 2-4-log fold reduction in mean virus burden in both the gut and blood when compared to unvaccinated controls and provided durable protection from viral rebound and disease progression after the drug was discontinued. This effect was associated with significant increases in IFN-γ T cell responses in both the blood and gut and SIV-specific CD8+ T cells with dual TNF-α and cytolytic effector functions in the blood. Importantly, a broader specificity in the T cell response seen in the gut, but not the blood, significantly correlated with a reduction in virus production in mucosal tissues and a lower virus burden in plasma. We conclude that immunizing with vaccines that induce immune responses in mucosal gut tissue could reduce residual viral reservoirs during drug therapy and improve long-term treatment of HIV infection in humans.     

Adeno-associated viral vectors as agents for gene delivery: application in disorders and trauma of the central nervous system

The use of viral vectors as agents for gene delivery provides a direct approach to manipulate gene expression in the mammalian central nervous system (CNS). The present article describes in detail the methodology for the injection of viral vectors, in particular adeno-associated virus (AAV) vectors, into the adult rat brain and spinal cord to obtain reproducible and successful transduction of neural tissue. Surgical and injection procedures are based on the extensive experience of our laboratory to deliver viral vectors to the adult rat CNS and have been optimized over the years. First, a brief overview is presented on the use and potential of viral vectors to treat neurological disorders or trauma of the CNS. Next, methods to deliver AAV vectors to the rat brain and spinal cord are described in great detail with the intent of providing a practical guide to potential users. Finally, some data on the experimental outcomes following AAV vector-mediated gene transfer to the adult rat CNS are presented as is a brief discussion on both the advantages and limitations of AAV vectors as tools for somatic gene transfer.     

Expression vectors for quatitating in vivo translational ambiguity: Their potential use to analyse frameshifting at the HIV gag-pol junction

Translational errors are necessary so as to allow gene expression in various organisms. In retroviruses, synthesis of pol gene products necessitates either readthrough of a stop codon or frameshifting. Here we present an experimental system that permits quantification of translational errors in vivo. It consists of a family of expression vectors carrying different mutated versions of the luc gene as reporter. Mutations include both an in-frame stop codon and 1-base-pair deletions that require readthough or frameshift, respectively, to give rise to an active product. This system is sensitive enough to detect background errors in mammalian cells. In addition, one of the vectors contains two unique cloning sites that make it possible to insert any sequence of interest. This latter vector was used to analyse the effect of a DNA fragment, proposed to be the target of high level slippage at the gag-pol junction of HIV. The effect of paromomycin and kasugamycin, two antibiotics known to influence translational ambiguity, was also tested in cultured cells. The results indicate that paromomycin diversely affects readthrough and frameshifting, while kasugamycin had no effect.This family of vectors can be used to analyse the influence of structural and external factors on translational ambiguity in both mammalian cells and bacteria.