New insights into the immunology and evolution of HIV

Molecular Epidemiology of HIV-1 Virus in Puerto Rico: Novel Cases of HIV-1 Subtype C, D, and CRF-24BG

HIV-1 subtype B virus is the most prevalent subtype in Puerto Rico (PR), accounting for about 90% of infection in the island. Recently, other subtypes and circulating recombinant forms (CRFs), including F(12_BF), A (01_BF), and CRF-39 BF-like, have been identified. The purpose of this study is to assess the distribution of drug resistance mutations and subtypes in PR. A total of 846 nucleotide sequences from the period comprising 2013 through 2017 were obtained from our "HIV Genotyping" test file. Phylogenetic and molecular epidemiology analyses were performed to evaluate the evolutionary dynamics and prevalence of drug resistance mutations. According to our results, we detected a decrease in the prevalence of protease inhibitor, nucleoside reverse transcriptase inhibitor (NRTI), and non-NRTI (NNRTI) resistance mutations over time. In addition, we also detected recombinant forms and, for the first time, identified subtypes C, D, and CRF-24BG in PR. Recent studies suggest that non-subtypes B are associated with a high risk of treatment failure and disease progression. The constant monitoring of viral evolution and drug resistance mutation dynamics is important to establish appropriate efforts for controlling viral expansion.

Evidence of phenotypic stability after transduction of fluorescent proteins in two human tongue cancer cell lines

OBJECTIVES

This study investigated the phenotypic stability and biological properties of two human tongue cancer cell lines after transduction of fluorescent proteins.

DESIGN

The human tongue cancer cell lines UM1 and UM2 were cultured with GFP and RFP lentiviral particles stock for 72h. Cells with successful transduction of fluorescent proteins were selected in a medium containing G418 antibiotics for two weeks. The proliferation rates of parental and transduced cell lines were evaluated by their population doubling time (PDT). Transduction efficiency was assessed by fluorescence microscope and flow cytometry. The transduced cells in passage 1, 2, 10, 20 and 30 were collected to check the stability of fluorescent protein expression. Phenotypic stability of the transduced cells was detected by means of cell morphology, cell surface markers and cell function evaluating essay.

RESULTS

The proliferation rates of the transduced cell lines showed no significant difference compared to their parental cells. Successful transduction with high efficiency (99% up) was demonstrated. High fluorescence expression on both transduced cells was detected until the thirtieth generation. UM1 and UM1-GFP displayed mesenchymal cell characteristics, while UM2 and UM2-RFP cell lines showed properties characteristic of epithelial.

CONCLUSIONS

Two human tongue cancer cell lines of epithelial and mesenchymal phenotype respectively, have been successfully labelled with green and red fluorescent proteins. The fluorescence maintained a high expression rate over thirty generations without influencing the original morphological phenotype and cadherin expression.

In vivo manipulation of gene expression in non-human primates using lentiviral vectors as delivery vehicles

Non-human primates (NHPs) are an invaluable resource for the study of genetic regulation of disease mechanisms. The main disadvantage of using NHPs as a preclinical model of human disease is the difficulty of manipulating the monkey genome using conventional gene modifying strategies. Lentiviruses offer the possibility of circumventing this difficulty because they can infect and transduce either dividing or nondividing cells, without producing an immune response. In addition, lentiviruses can permanently integrate into the genome of host cells, and are able to maintain long-term expression. In this article we describe the lentiviral vectors that we use to both express transgenes and suppress expression of endogenous genes via RNA interference (RNAi) in NHPs. We also discuss the safety features of currently available vectors that are especially important when lentiviral vectors are used in a species as closely related to humans as NHPs. Finally, we describe in detail the lentiviral vector production protocol we use and provide examples of how the vector can be employed to target peripheral tissues and the brain.

Significance of variation within HIV, EBV, and KSHV subtypes

Since their initial transmission to humans, viruses have diversified extensively through recombination and mutation. The presence of intra- and inter-individual viral diversity influences disease progression, drug resistance, and therapy and presumably explains the conflicting results in many studies, including the failure of peptide-based vaccination strategies. Although HIV is a small RNA virus, coinfection with large DNA viruses, notably the oncogenic gamma-herpesviridae human herpesvirus-8 and Epstein Barr virus, is common. This coinfection occurs secondary to immunosuppression and shared transmission routes with high-risk predisposing behavior. In addition, all 3 of these viruses can lead to chronic infections, long periods of latency, and reactivation characterized by pain and suffering. The efficient targeting of their genetic diversity represents one of the major challenges in their control, both in prophylactic and therapeutic strategies. An understanding of diversity will help delineate whether population-specific vaccine strategies are necessary.

Role for plasmacytoid dendritic cells in anti-HIV innate immunity

The role of plasmacytoid dendritic cells (pDC) in anti-HIV immunity is mostly represented by the production of type I IFN in response to HIV infection in vitro and in vivo. This production is decreased in HIV-1 infected patients at the time of primary infection and during chronic disease in association with progression of disease. Circulating pDC counts are decreased concomitantly with type I IFN, and both factors correlate inversely overall with viral loads and positively with CD4+ T-cell counts. These parameters might be used in clinical immunology to monitor treatment and as predictive factors of immune control of HIV-1 replication to help decide whether to interrupt antiretroviral treatment. They may be related to control of HIV replication as well as to pathogenesis of infection, perhaps in setting the balance between immunity or tolerance to the virus. A better understanding of these parameters is required while attempts to use IFN-alpha or ligands of Toll-like receptors found on pDC are being made.

Type I interferon production in HIV-infected patients

Type I IFNs display multiple biological effects. They have a strong antiviral action, not only directly but also indirectly through activation of the immune system. They may also have actions that are deleterious for the host. The cells that produce type I IFN are mostly plasmacytoid dendritic cells (pDC), but this depends on the viral stimulus. The migration and distribution of pDC into lymphoid organs, driven by chemokine interactions with their ligands, determines interaction with different cell types. In HIV infection, IFN production in vitro is impaired during primary infection and later in association with opportunistic infections. Circulating pDC numbers are decreased in parallel. These parameters may be used to help assess the prognosis of the disease and to monitor treatment.

Lethal mutagenesis of HIV

HIV-1 and other retroviruses exhibit mutation rates that are 1,000,000-fold greater than their host organisms. Error-prone viral replication may place retroviruses and other RNA viruses near the threshold of "error catastrophe" or extinction due to an intolerable load of deleterious mutations. Strategies designed to drive viruses to error catastrophe have been applied to HIV-1 and a number of RNA viruses. Here, we review the concept of extinguishing HIV infection by "lethal mutagenesis" and consider the utility of this new approach in combination with conventional antiretroviral strategies.

Mutations in the RNase H primer grip domain of murine leukemia virus reverse transcriptase decrease efficiency and accuracy of plus-strand DNA transfer

The RNase H primer grip of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) contacts the DNA primer strand and positions the template strand near the RNase H active site, influencing RNase H cleavage efficiency and specificity. Sequence alignments show that 6 of the 11 residues that constitute the RNase H primer grip have functional equivalents in murine leukemia virus (MLV) RT. We previously showed that a Y586F substitution in the MLV RNase H primer grip resulted in a 17-fold increase in substitutions within 18 nucleotides of adenine-thymine tracts, which are associated with a bent DNA conformation. To further determine the effects of the MLV RNase H primer grip on replication fidelity and viral replication, we performed additional mutational analysis. Using either beta-galactosidase (lacZ) or green fluorescent protein (GFP) reporter genes, we found that S557A, A558V, and Q559L substitutions resulted in statistically significant increases in viral mutation rates, ranging from 2.1- to 3.8-fold. DNA sequencing analysis of nonfluorescent GFP clones indicated that the mutations in RNase H primer grip significantly increased the frequency of deletions between the primer-binding site (PBS) and sequences downstream of the PBS. In addition, quantitative real-time PCR analysis of reverse transcription products revealed that the mutant RTs were substantially inefficient in plus-strand DNA transfer relative to the wild-type control. These results indicate that the MLV RNase H primer grip is an important determinant of in vivo fidelity of DNA synthesis and suggest that the mutant RT was unable to copy through the DNA-RNA junction of the minus-strand DNA and the tRNA because of its bent conformation resulting in error-prone plus-strand DNA transfer.

Hypothesis links emergence of chloroquine-resistant malaria and other intracellular pathogens and suggests a new strategy for treatment of diseases caused by intracellular parasites

Chloroquine and related anti-malarial drugs appear to promote apoptosis in T-cells by suppressing NF-kappa-B, which enhances the expression of anti-apoptotic proteins (e.g., Bcl-2). Thus, chloroquine has found applications in autoimmune diseases where it apparently facilitates apoptosis of abnormally persistent T-cell clones. The mode of action of chloroquine in prevention of malaria is not known, but it may be to minimize replication of the parasite in the liver cells, which occurs before invasion of the erythrocytes, by facilitating premature apoptosis of the infected host cells. After introduction of chloroquine in the 1950s world-wide for prophylactic use, chloroquine-resistant malaria emerged. Here it is hypothesized that concurrent with emergence of chloroquine-resistant malaria (presumably with enhanced anti-apoptotic capabilities), other intracellular parasites have evolved to enhance their ability to prevent apoptosis in host cells. Two examples of viral diseases that have emerged from areas of high incidence of chloroquine-resistant malaria are AIDS from HIV and SARS from coronavirus. The hypothesis holds that prophylactic exposure to pro-apoptotic chloroquine drugs caused natural selection for strains of viruses and other parasites that have enhanced anti-apoptotic abilities. When transmitted to host organisms that are not under the influence of the pro-apoptotic drug, the new "anti-apoptotic" strains may cause unexpected diseases. In the case of SARS, the coronavirus appears to have accessed a new niche where it proves to be lethal to its host. In the case of AIDS, the HIV (which has had a long-term symbiotic relationship with primates) has run amuck because the infected cells are now substantially more tolerant to the toxins (i.e., resistant to apoptosis) that they secrete than the uninfected bystander cells, which are not unusually resistant to apoptosis. A corollary to the hypothesis is that if the level of resistance to apoptosis in the infected cells were no higher than the level of resistance in the bystander cells, then the infected cells would preferentially kill themselves through apoptosis. It appears that in the case of HIV, the increased resistance to apoptosis is provided by expression of Bcl-2 and suppression of p53. Hence, drugs that suppresses Bcl-2 or restore p53 function might be effective in restoring the parity of resistance to apoptosis between infected and uninfected cells. Currently, an antisense drug targeting Bcl-2 (G3139/Genasense(TM), Genta, Inc.) is in late-stage cancer trials and may be on the market for those indications in months. It would be interesting to try these drugs against various intracellular parasites including HIV. This approach to prevent or eliminate active infections might be particularly attractive against a range of parasites (virus, bacteria, protozoa, fungus) when safe and effective vaccines are not available.

Therapeutic polypeptides based on HBV core 18-27 epitope can induce CD8+ CTL-mediated cytotoxicity in HLA-A2+ human PBMCs

AIM: To explore how to improve the immunogenicity of HBcAg CTL epitope based polypeptides and to trigger an HBV-specific HLA I-restricted CD₈⁺ T cell response in vitro.

METHODS: A new panel of mimetic therapeutic peptides based on the immunodominant B cell epitope of HBV PreS2 18-24 region, the CTL epitope of HBcAg18-27 and the universal T helper epitope of tetanus toxoid (TT) 830-843 was designed using computerized molecular design method and synthesized by Merrifield’s solid-phase peptide synthesis. Their immunological properties of stimulating activation and proliferation of lymphocytes, of inducing T_H1 polarization, CD₈⁺ T cell magnification and HBV-specific CD₈⁺ CTL mediated cytotoxicity were investigated in vitro using HLA-A2⁺ human peripheral blood mononuclear cells (PBMCs) from healthy donors and chronic hepatitis B patients.

RESULTS: Results demonstrated that the therapeutic polypeptides based on immunodominant HBcAg18-27 CTL, PreS2 B- and universal T_H epitopes could stimulate the activation and proliferation of lymphocytes, induce specifically and effectively CD₈⁺ T cell expansion and vigorous HBV-specific CTL-mediated cytotoxicity in human PBMCs.

CONCLUSION: It indicated that the introduction of immunodominant T helper plus B-epitopes with short and flexible linkers could dramatically improve the immunogenicity of short CTL epitopes in vitro.

Therapeutic polypeptides based on HBcAg18-27 CTL epitope can induce antigen-specific CD8+ CTL-mediated cytotoxicity in HLA-A2 transgenic mice

AIM: To explore how to trigger an HLAI-restricted CD8⁺ T cell response to exogenously synthesized polypeptides in vivo.

METHODS: Three mimetic therapeutic polypeptides based on the immunodominant CTL epitope of HBcAg, the B- epitope of HBV PreS₂ region and a common T helper sequence of tetanus toxoid were designed and synthesized with Merrifield’s solid-phase peptide synthesis method. Their immunological properties of inducing T_H1 polarization, CD8⁺ HBV-specific CTL expansion and CD8⁺ T cell mediated cytotoxicity were investigated in HLA-A2 transgenic mice.

RESULTS: Results demonstrated that the mimetic polypeptides comprised of the immunodominant CTL, B-, and T helper epitopes could trigger specifically and effectively vigorous CD8⁺ HBV-specific CTL-mediated cytotoxicity and T_H1 polarization of T cells in HLA-A2 transgenic mice.

CONCLUSION: A designed universal T helper plus B-epitopes with short and flexible linkers could dramatically improve the immunogenicity of CTL epitopes in vivo. And that the mimetic therapeutic peptides based on the reasonable match of the above CTL, B- and T helper epitopes could be a promising therapeutic peptide vaccine candidate against HBV infection.

Kaposi's sarcoma as a model for cancer immunotherapy

Physicians have, for over a century, attempted to harness the potential therapeutic power of the immune system to treat patients with cancer. The discovery that cancer regression can be achieved by immune rejection of tumour antigens theoretically allows the eradication of neoplastic cells without toxicity to normal tissues. An understanding of the mode of presentation of tumour antigens, including those complexed to heat shock proteins by major histocompatibility complex (MHC) class I and class II molecules, and their recognition by CD8(+) and CD4(+) T cells, respectively, has further delineated the potential cancer rejection pathways involved. This also enables the sustained induction and expansion of specific anti-tumour T cells with cytolytic activity.

Antibody-targeted MHC complex–directed expansion of HIV-1– and KSHV-specific CD8+ lymphocytes: a new approach to therapeutic vaccination

The ability of therapeutic vaccines to generate large numbers of CD8+ T lymphocytes that have specificity for HIV-1 or other virally infected cells has enormous potential clinical value. However, approaches to produce cytotoxic T lymphocytes (CTLs) in vivo via vaccine technology have thus far been disappointing and the ex vivo production of cells for adoptive transfer is labor intensive and expensive. We describe the results of a 2-step antibody-targeting system for the production of CD8+ T lymphocytes specific for HIV-1 and Kaposi sarcoma–associated herpesvirus (KSHV), suitable for use in vivo. In 8 consecutive human leukocyte antigen–A2 (HLA-A2)–positive HIV-1–infected individuals with Kaposi sarcoma, 2 cycles of this system resulted in more than 1 Log increases of specific anti-HIV and anti-KSHV CD8+ lymphocytes. These expanded cells have an effector phenotype that includes the ability to produce interferon-γ and CD45Ra+/CD69+ staining. We have shown that antibody-targeted B cells can function as effective antigen-presenting molecules and lead to sustained specific T-lymphocyte expansion from peripheral blood mononuclear cells (PBMCs) of immunosuppressed individuals. This approach, which offers an easy and effective protocol for the amplification of specific antiviral and antitumor CTLs, may offer significant advances for in vivo T-cell immunotherapeutic protocols.

Purification and characterization of Moschatin, a novel type I ribosome-inactivating protein from the mature seeds of pumpkin (Cucurbita moschata), and preparation of its immunotoxin against human melanoma cells

A novel ribosome-inactivating protein designated Moschatin from the mature seeds of pumpkin (Cucurbita moschata) has been successively purified to homogeneity, using ammonium sulfate precipitation, CM-cellulose 52 column chromatography, Blue Sepharose CL-6B Affinity column chromatography and FPLC size-exclusion column chromatography. Moschatin is a type 1 RIP with a pI of 9.4 and molecular weight of approximately 29 kD. It is a rRNA N-glycosidase and potently blocked the protein synthesis in the rabbit reticulocyte lysate with a IC50 of 0.26 nM. Using the anti-human melanoma McAb Ng76, a novel immunotoxin Moschatin-Ng76 was prepared successfully and it efficiently inhibited the growth of targeted melanoma cells M21 with a IC50 of 0.04 nM, 1500 times lower than that of free Moschatin. The results implied that Moschatin could be used as a new potential anticancer agent.