Reexamining AIDS research priorities

HIV infection and depression

Major depression is highly prevalent among HIV-positive patients (HIVpp). The prevalence of depression ranges between 18% and 81%, depending on the population studied and the methodology of the study. The etiology of depression in HIVpp is likely determined by: (i) biological factors (alterations in the white matter structure, hypothalamic-pituitary-thyroid dysfunction, Tat-protein-induced depressive behavior); (ii) psychosocial factors (HIV stigma, occupational disability, body image changes, isolation and debilitation); (iii) history or comorbidity of psychiatric illness; and (iv) the perinatal period in HIVpp women. Symptomatology of depression differs between HIVpp and HIV-negative patients (HIVnp). Depression may also alter the function of lymphocytes in HIVpp and decrease natural killer cell activity, contributing to the increased mortality in these patients. Selective serotonin re-uptake inhibitors are considered the first-line treatment. Treatment of depression can improve quality of life and lead to a better prognosis of HIV infection.

Progress towards the use of Listeria monocytogenes as a live bacterial vaccine vector for the delivery of HIV antigens

Listeria monocytogenes is a facultative intracellular bacterium that enters the cell by phagocytosis after which it colonizes the cytosol of the host cell. It is thus a potent vaccine vector for the presentation of passenger antigens to the major histocompatability complex class II and class I pathways of antigen processing and presentation. This article shall review the progress made in developing this unusual bacterium as a vaccine vector. In mouse models, recombinant Listeria carrying a number of different antigens have been shown to provide protective immunity against infectious organisms and therapeutic immunity directed towards tumor-associated antigens. Listeria has been engineered to express a number of HIV/SIV antigens. Measurements of immune responses using these recombinant strains in the mouse, after oral and parenteral immunization, and in the rhesus macaque after oral immunization indicate that strong cell-mediated immunity can be induced against these antigens. This review also discusses safety issues associated with live bacterial vaccine vectors and problems to be overcome in developing Listeria as a HIV vaccine for human use.

The effects of stressful life events, coping, and cortisol on HIV infection

What is the role of stress and coping in changes in immunologic and clinical indicators of human immunodeficiency virus disease progression? There is substantial evidence that stressful life events and passive coping strategies, such as denial, may have a detrimental effect on HIV disease progression. Given the harmful effects of stress and passive coping, the author reviews the limited research testing the efficacy of interventions, such as cognitive-behavioral therapies for HIV-infected persons. Finally, in trying to understand psychoimmune relationships in HIV, the evidence is examined for the mediating and direct effects of cortisol, a hormone associated with stress, on HIV disease progression. Delineating the role of psychosocial factors and cortisol on HIV disease progression may aid in the development of new interventions for this devastating disease.

Induction of cross clade reactive specific antibodies in mice by conjugates of HGP-30 (peptide analog of HIV-1(SF2) p17) and peptide segments of human beta-2-microglobulin or MHC II beta chain

HGP-30, a 30 amino acid synthetic peptide homologous to a conserved region of HIV-1(SF2) p17 (aa86-115), has previously been shown to elicit both cellular and humoral immune responses when conjugated to KLH and adsorbed to alum. However, the free HGP-30 peptide is not immunogenic in animals. In order to improve the immunogenicity of HGP-30, peptide conjugates consisting of a modified HGP-30 sequence (m-HGP-30/aa82-111) and a peptide segment, residues 38-50, of the MHC I accessory molecule, human beta-2-microglobulin (beta-2-M), referred to as Peptide J, or a peptide from the MHC II beta chain (peptide G) were evaluated in mice. The effects of carriers and adjuvants on serum antibody titers, specificities to various HIV-1 clade peptides similar to HGP-30 and isotype patterns were examined. Peptides J or especially G conjugated to modified-HGP-30 (LEAPS 102 and LEAPS 101, respectively) generated comparable or better immune responses to modified HGP-30 than KLH conjugates as judged by the induction of: (1) similar antibody titers; (2) broader HIV clade antigen binding; and (3) antibody isotype response patterns indicative of a TH1 pathway (i.e. increased amounts of IgG2a and IgG2b antibodies). The ISA 51 and MPL(R)-SE adjuvants induced higher antibody responses than alum, with the ISA 51 being more potent. Immune responses to LEAPS 102, as compared to LEAPS 101, were weaker and slower to develop as determined by antibody titers and cross clade reactivity of the antibodies induced. Compared to KLH conjugates which induced significant anti-KLH antibody titers, minimal antibody responses were observed to peptide G, the more immunogenic conjugate, and peptide J. These results suggest that modified HGP-30 L.E.A.P.S. constructs may be useful as HIV vaccine candidates for preferential induction of TH1 directed cell mediated immune responses.

High versus low basal cortisol secretion in asymptomatic, medication-free HIV-infected men: differential effects of severe life stress on parameters of immune status

The authors hypothesized that HIV-infected men with high basal cortisol secretion would exhibit greater stress-related reductions in the ratio of Th1/Th2 cell-derived cytokines and numbers of CD8+ T and NK lymphocytes than low basal cortisol secretors. A semistructured interview was used to assess life stress during the preceding 6 months of 94 HIV-infected men classified as high and low cortisol secretors (n = 47/group). Increased levels of severe life stress were highly correlated with lower numbers of CD8+ T cells, CD16+ and CD56+ NK cells, CD57+ cells, and higher DHEA-S concentrations in the high cortisol group. Conversely, no significant correlations were found in the low cortisol group. No correlations were found between stress and CD4+ T helper/inducer cell counts, cytokine production, or testosterone levels in either participating group. These data suggest that severe stress in combination with high glucocorticoid activity may modify select parameters of immune status in HIV-infected men.

Irreversible inhibition of human immunodeficiency virus type 1 integrase by dicaffeoylquinic acids

Human immunodeficiency virus type 1 (HIV-1) and other retroviruses require integration of a double-stranded DNA copy of the RNA genome into the host cell chromosome for productive infection. The viral enzyme, integrase, catalyzes the integration of retroviral DNA and represents an attractive target for developing antiretroviral agents. We identified several derivatives of dicaffeoylquinic acids (DCQAs) that inhibit HIV-1 replication in tissue culture and catalytic activities of HIV-1 integrase in vitro. The specific step at which DCQAs inhibit the integration in vitro and the mechanism of inhibition were examined in the present study. Titration experiments with different concentrations of HIV-1 integrase or DNA substrate found that the effect of DCQAs was exerted on the enzyme and not the DNA. In addition to HIV-1, DCQAs also inhibited the in vitro activities of MLV integrase and truncated variants of feline immunodeficiency virus integrase, suggesting that these compounds interacted with the central core domain of integrase. The inhibition on retroviral integrases was relatively specific, and DCQAs had no effect on several other DNA-modifying enzymes and phosphoryltransferases. Kinetic analysis and dialysis experiments showed that the inhibition of integrase by DCQAs was irreversible. The inhibition did not require the presence of a divalent cation and was unaffected by preassembling integrase onto viral DNA. The results suggest that the irreversible inhibition by DCQAs on integrase is directed toward conserved amino acid residues in the central core domain during catalysis.

HIV vaccines

In summary, the development of HIV vaccines has progressed from simple first-generation env subunit vaccines to second-generation vaccines containing multiple subunits. Vaccines with epitopes for CMI and Ab responses have broadened the immune response and the potential efficacy of these vaccines. It is hoped that newer technologies including the development of adjuvants, new types of vaccines, such as naked DNA, and new delivery systems, such as liposomes, will evoke stronger immune responses with longer duration. Improved schedules for dosing and combinations of HIV vaccines may result in longer lasting immune responses. A phase III trial is anticipated to begin within the next 2 years. After a temporary lull, the outlook for HIV vaccine development is being met once again with strong enthusiasm and encouragement for the future.

Booster immunization of HIV-1 negative volunteers with HGP-30 vaccine induces protection against HIV-1 virus challenge in SCID mice

Eleven HIV-1 seronegative subjects previously injected with an HIV-1 p17 synthetic peptide vaccine (HGP-30) were given two booster immunizations to evaluate memory cell responses and the ability to boost cellular and humoral immune responses. Five of 11 subjects showed a significant increase in their antibody titres to HGP-30 or p17 and 6/11 had T-cell proliferation responses to either HGP-30 or p17. HIV-1 virus challenge studies in SCID mice demonstrated that 39 of 50 mice (78%) receiving PBMC from 5 of the HGP-30 immunized subjects were protected from infection with a different strain of HIV-1 compared to 4 of 30 mice (13%) that received PBMC from 3 non-immunized subjects (p < 0.001). These studies show that booster immunizations with HGP-30 vaccine are safe and non-toxic and induce protective cell mediated immune responses.

A simplified vaccinologists' vaccinology and the pursuit of a vaccine against AIDS

Vaccinology is the science and engineering of developing vaccines to prevent infectious diseases. Guidelines come from knowledge of pathogenesis and from successful past vaccines. The vaccine enterprise relies on the evolution of appropriate science and technology. Governmental support and industrial participation are key to successful development of new vaccines. A large challenge for vaccinology is a vaccine which protects against AIDS. Though misguided in its first decade, current vaccine research is directed to use of any and all viral antigens and to elicit both cell-mediated and humoral immune responses that are resident, with memory, at the mucosal sites of viral entry. Recent seminal discoveries guiding the future include selective elicitation of both Type 1 and Type 2 immune responses, and prime-boosting using recombinant viral or DNA vectors and expressed antigens. Success in vaccinology depends on simplification of the complex and on iterative processes in a well-defined pathway. The present and future of vaccinology are discussed in depth.

Social separation, housing relocation, and survival in simian AIDS: a retrospective analysis

OBJECTIVE

To test the hypothesis that changes in housing, particularly those involving social separations, would have a negative impact on survival in rhesus monkeys experimentally inoculated with the simian immunodeficiency virus (SIV).

METHODS

An archival methodology was used. Colony records at four Regional Primate Research Centers were screened, and data pertaining to demographics, contents of the inoculum, medical history before and after inoculation, and housing relocations and social companions were coded. The final sample size totaled 298 individuals.

RESULTS

Following statistical control of covariates, housing relocations and social separations in the 90-day period before SIV inoculation and in the 30-day period after inoculation were associated with decreased survival. There was evidence that housing disruptions occurring earlier after inoculation were associated with shorter survival. Finally, a subset of animals was found to have been socially housed after SIV inoculation; such experience had negative consequences for survival.

CONCLUSIONS

The results indicate that psychosocial experiences that likely produce a stressful state are associated with shorter survival in SIV-infected monkeys.

Co-evolution of human immunodeficiency virus and cytotoxic T-lymphocyte responses

After more than a decade of intensive research, the precise role of human immunodeficiency virus (HIV)-specific cytotoxic T lymphocytes (CTL) in determining the course of the infection remains open to argument. It is established that HIV-specific CTL appear early in the infection and are temporally associated with the clearance of culturable virus from the blood; that CTL are generally detectable at very high levels throughout the asymptomatic phase and decline at the time of progression to AIDS; and that CTL-mediated killing is sufficiently fast to prevent production of new virions by HIV-infected cells. However, viral turnover is high throughout the course of the infection, and infected individuals progress inexorably to disease in spite of the CTL response. In order to address the question of whether CTL play an active part in influencing the course of HIV infection, one approach has been to seek evidence for CTL-mediated selection pressure on the virus. Several clear examples of CTL epitope-specific mutations selected to fixation are described. We argue that CTL escape is a common event which occurs at all stages of the infection. Detailed longitudinal studies are required to detect CTL escape and to understand the complexities contributed by factors such as a polyvalent CTL response and the presence of epitope variants which antagonise the CTL response. In conclusion, there is strong evidence of a dynamic process in which CTL impose important selection constraints upon HIV from which the virus attempts to escape; ultimately, at the time of disease progression, the tenuous control of CTL over the virus is lost.

In vitro assays for activities of retroviral integrase

Integration of retroviral DNA, an essential step during the retroviral life cycle, is mediated by the viral protein integrase. Simple in vitro assays for measuring integrase activities are described, including catalysis (3'-end processing, 3'-end joining, disintegration), juxtaposition of viral DNA ends, DNA binding, and target site selection. The described assays will be useful in elucidating the molecular mechanism of retroviral integration and screening for integrase inhibitors as potential anti-retroviral drugs.

Progress and challenges toward an AIDS vaccine: Brother, can you spare a paradigm?

The development of a safe and effective vaccine for prevention of AIDS has thus far proven to be exceedingly difficult due to the complexities associated with HIV pathogenesis including but not limited to antigenic hypervariability, multiple routes and modes of transmission, a lack of defined correlates of protective immunity, and a tropism for infection of immunoregulatory cells which are essential for orchestrating an effective host immune response. Recent observations, including the identification of significant differences between primary isolates of HIV circulating in the population and laboratory-adapted isolates, animal model protection studies demonstrating prevention of AIDS-like disease progression in nonhuman primates in the absence of sterilizing immunity, and epidemiologic studies which question the current dogma surrounding HIV variation and control, have led to the development of novel approaches for antigen presentation and adjuvant development targeted at AIDS vaccine development. The goal of developing a safe and effective AIDS vaccine will likely occur when continued advances in understanding the immunopathogenesis of HIV is balanced with a healthy dose of empirical testing of innovative candidate AIDS vaccines.

Synthesis, chromatographic resolution, and anti-human immunodeficiency virus activity of (+/-)-calanolide A and its enantiomers

The anti-HIV agent (+/-)-calanolide A (1) has been synthesized in a five-step approach starting with phloroglucinol [-->5-->6-->11-->18-->(+/-)-1], which includes Pechmann reaction, Friedel-Crafts acylation, chromenylation with 4,4-dimethoxy-2-methylbutan-2-ol, cyclization, and Luche reduction. Cyclization of chromene 11 to chromanone 18 was achieved by employing either acetaldehyde diethyl acetal or paraldehyde in the presence of trifluoroacetic acid and pyridine or PPTS. Luche reduction of chromanone 18 at lower temperature preferably yielded (+/-)-1. Reduction of chromone 12, synthesized by Kostanecki-Robinson reaction from chromene 11, failed to afford (+/-)-1. The synthetic (+/-)-1 has been chromatographically resolved into its optically active forms, (+)- and (-)-1. The anti-HIV activities for synthetic (+/-)-1, as well as resultant (+)- and (-)-1, have been determined. Only (+)-1 accounted for anti-HIV activity, which was similar to the data reported for the natural product, and (-)-1 was inactive.

HIV preventive vaccines. Progress to date

The major conceptual problem for HIV vaccine development has been the lack of information on immune responses known to correlate with protection against HIV infection in humans. In this regard, studies on the natural history of HIV infection and AIDS, especially of people with apparent resistance to HIV infection and of patients with HIV infection who have long term survival without disease progression, may provide important information for vaccine development. In addition, a major concern for the development of broadly effective vaccines has been the extensive genetic variability which is characteristic of HIV. In spite of these unknowns, the first generation of HIV candidate vaccines has been developed and evaluated. HIV candidate vaccines based on the subunit recombinant envelope concept (gp120 or gp160) have been shown to protect chimpanzees from HIV infection on challenge, and have now been evaluated in humans in phase I and phase II trials. These products are well tolerated, and capable of inducing neutralising antibodies, but not cytotoxic T lymphocytes. A second vaccine concept, currently in phase I trials, is based on live recombinant vectors, especially using poxvirus vectors followed by boosting with subunit recombinant envelope vaccines. This concept is theoretically very attractive because preliminary data suggest that these vaccines induce both humoral and cell-mediated immunity. However, no published information is available on the ability of live recombinant vector vaccines to protect chimpanzees from HIV infection. The next step in HIV vaccine development is to proceed carefully to expanded phase II and phase III trials to assess the protective efficacy of these candidate vaccines in humans. These trials will be extremely complex from the logistical, scientific and ethical points of view, and will require close collaboration between clinical, basic science and behavioural researchers, national and international organisations, and the pharmaceutical industry.

Inhibition of the integrase of human immunodeficiency virus (HIV) type 1 by anti-HIV plant proteins MAP30 and GAP31

MAP30 (Momordica anti-HIV protein of 30 kDa) and GAP31 (Gelonium anti-HIV protein of 31 kDa) are anti-HIV plant proteins that we have identified, purified, and cloned from the medicinal plants Momordica charantia and Gelonium multiflorum. These antiviral agents are capable of inhibiting infection of HIV type 1 (HIV-1) in T lymphocytes and monocytes as well as replication of the virus in already-infected cells. They are not toxic to normal uninfected cells because they are unable to enter healthy cells. MAP30 and GAP31 also possess an N-glycosidase activity on 28S ribosomal RNA and a topological activity on plasmid and viral DNAs including HIV-1 long terminal repeats (LTRs). LTRs are essential sites for integration of viral DNA into the host genome by viral integrase. We therefore investigated the effect of MAP30 and GAP31 on HIV-1 integrase. We report that both of these antiviral agents exhibit dose-dependent inhibition of HIV-1 integrase. Inhibition was observed in all of the three specific reactions catalyzed by the integrase, namely, 3' processing (specific cleavage of the dinucleotide GT from the viral substrate), strand transfer (integration), and "disintegration" (the reversal of strand transfer). Inhibition was studied by using oligonucleotide substrates with sequences corresponding to the U3 and U5 regions of HIV LTR. In the presence of 20 ng of viral substrate, 50 ng of target substrate, and 4 microM integrase, total inhibition was achieved at equimolar concentrations of the integrase and the antiviral proteins, with EC50 values of about 1 microM. Integration of viral DNA into the host chromosome is a vital step in the replicative cycle of retroviruses, including the AIDS virus. The inhibition of HIV-1 integrase by MAP30 and GAP31 suggests that impediment of viral DNA integration may play a key role in the anti-HIV activity of these plant proteins.