Interactions between human immunodeficiency virus type 1 and vaccinia virus in human lymphoid tissue ex vivo

The mark of success: The role of vaccine-induced skin scar formation for BCG and smallpox vaccine-associated clinical benefits

Skin scar formation following Bacille Calmette-Guérin (BCG) or smallpox (Vaccinia) vaccination is an established marker of successful vaccination and 'vaccine take'. Potent pathogen-specific (tuberculosis; smallpox) and pathogen-agnostic (protection from diseases unrelated to the intentionally targeted pathogen) effects of BCG and smallpox vaccines hold significant translational potential. Yet despite their use for centuries, how scar formation occurs and how local skin-based events relate to systemic effects that allow these two vaccines to deliver powerful health promoting effects has not yet been determined. We review here what is known about the events occurring in the skin and place this knowledge in the context of the overall impact of these two vaccines on human health with a particular focus on maternal-child health.

Activation-neutral gene editing of tonsillar CD4 T cells for functional studies in human ex vivo tonsil cultures

The molecular and immunological properties of tissue-resident resting CD4 T cells are understudied due to the lack of suitable gene editing methods. Here, we describe the ex vivo culture and gene editing methodology ediTONSIL for CD4 T cells from human tonsils. Optimized CRISPR-Cas9 RNP nucleofection results in knockout efficacies of over 90% without requiring exogenous activation. Editing can be performed on multiple cell types in bulk cultures or on isolated CD4 T cells that can be labeled and reintroduced into their tissue environment. Importantly, CD4 T cells maintain their tissue-specific properties such as viability, activation state, or immunocompetence following reassembly into lymphoid aggregates. This highly efficient and versatile gene editing workflow for tonsillar CD4 T cells enables the dissection of molecular mechanisms in ex vivo cultures of human lymphoid tissue and can be adapted to other tonsil-resident cell types.

Orbivirus NS4 Proteins Play Multiple Roles to Dampen Cellular Responses

Non-structural protein 4 (NS4) of insect-borne and tick-borne orbiviruses is encoded by genome segment 9, from a secondary open reading frame. Though a protein dispensable for bluetongue virus (BTV) replication, it has been shown to counter the interferon response in cells infected with BTV or African horse sickness virus. We further explored the functional role(s) of NS4 proteins of BTV and the tick-borne Great Island virus (GIV). We show that NS4 of BTV or GIV helps an E3L deletion mutant of vaccinia virus to replicate efficiently in interferon-treated cells, further confirming the role of NS4 as an interferon antagonist. Our results indicate that ectopically expressed NS4 of BTV localised with caspase 3 within the nucleus and was found in a protein complex with active caspase 3 in a pull-down assay. Previous studies have shown that pro-apoptotic caspases (including caspase 3) suppress type I interferon response by cleaving mediators involved in interferon signalling. Our data suggest that orbivirus NS4 plays a role in modulating the apoptotic process and/or regulating the interferon response in mammalian cells, thus acting as a virulence factor in pathogenesis.

Long-term effects of smallpox vaccination on expression of the HIV-1 co-receptor CCR5 in women

Background

Smallpox vaccinations were stopped globally in 1980. Recent studies have shown that in women, being smallpox vaccinated was associated with a reduced risk of HIV infection compared with not being smallpox vaccinated. At the initial infection, HIV-1 most often uses CCR5 as a co-receptor to infect the T-lymphocytes. We therefore investigated whether smallpox vaccination is associated with a down-regulation of CCR5 on the surface of peripheral T-lymphocytes in healthy women in Guinea-Bissau.

Methods

We included HIV seronegative women from Bissau, Guinea-Bissau, born before 1974, with and without a smallpox vaccination scar. Blood samples were stabilised in a TransFix buffer solution and stained for flow cytometry according to a T-cell maturation profile.

Results

Ninety-seven women were included in the study; 52 with a smallpox vaccination scar and 45 without a scar. No association between smallpox vaccination scar and CCR5 expression was found in any T-lymphocyte subtype.

Conclusion

Among HIV seronegative women, being smallpox vaccinated more than 40 years ago was not associated with a down-regulation of CCR5 receptors on the surface of peripheral T-lymphocytes.

The Effect of Smallpox and Bacillus Calmette-Guérin Vaccination on the Risk of Human Immunodeficiency Virus-1 Infection in Guinea-Bissau and Denmark

BACKGROUND

The live smallpox and Bacillus Calmette-Guérin (BCG) vaccinations have been associated with better adult survival in both Guinea-Bissau and Denmark. In Guinea-Bissau, human immunodeficiency virus (HIV)-1 became an important cause of death after smallpox vaccination was phased out globally in 1980. We hypothesised that smallpox and BCG vaccinations were associated with a lower prevalence of HIV-1 infection, and we tested this hypothesis in both Guinea-Bissau and Denmark.

METHODS

We conducted 2 studies: (1) a cross-sectional study of HIV infection and vaccination scars in Guinea-Bissau including 1751 individuals and (2) a case-base study with a background population of 46239 individuals in Denmark. In Guinea-Bissau, HIV-1 transmission was almost exclusively sexually transmitted. In Denmark, we excluded intravenous drug users. Data were analyzed using logistic regression.

RESULTS

Bacillus Calmette-Guérin and/or smallpox vaccination compared with neither of these vaccines was associated with an adjusted odds ratio (aOR) for HIV-1 of 0.62 (95% confidence interval [CI], 0.36-1.07) in Guinea-Bissau and 0.70 (95% CI, 0.43-1.15) in Denmark. We combined the results from both settings in a meta-analysis (aOR = 0.66; 95% CI, 0.46-0.96). Data from Guinea-Bissau indicated a stronger effect of multiple smallpox vaccination scars (aOR = 0.27; 95% CI, 0.10-0.75) as follows: women, aOR = 0.18 (95% CI, 0.05-0.64); men, aOR = 0.52 (95% CI, 0.12-2.33); sex-differential effect, P = .29.

CONCLUSIONS

The studies from Guinea-Bissau and Denmark, 2 very different settings, both suggest that the BCG and smallpox vaccines could be associated with a decreased risk of sexually transmitted HIV-1. It might be informative to pursue this observation and explore possible protective mechanisms as part of the search for an HIV-1 vaccine.

Vaginal Lactobacillus Inhibits HIV-1 Replication in Human Tissues Ex Vivo

Lactobacillus species, which dominate vaginal microbiota of healthy reproductive-age women, lower the risks of sexually transmitted infections, including the risk of human immunodeficiency virus (HIV) acquisition. The exact mechanisms of this protection remain to be understood. Here, we investigated these mechanisms in the context of human cervico-vaginal and lymphoid tissues ex vivo. We found that all six Lactobacillus strains tested in these systems significantly suppressed HIV type-1 (HIV-1) infection. We identified at least three factors that mediated this suppression: (i) Acidification of the medium. The pH of the undiluted medium conditioned by lactobacilli was between 3.8 and 4.6. Acidification of the culture medium with hydrochloric acid (HCl) to this pH in control experiments was sufficient to abrogate HIV-1 replication. However, the pH of the Lactobacillus-conditioned medium (CM) diluted fivefold, which reached ∼6.9, was also suppressive for HIV-1 infection, while in control experiments HIV-1 infection was not abrogated when the pH of the medium was brought to 6.9 through the use of HCl. This suggested the existence of other factors responsible for HIV-1 inhibition by lactobacilli. (ii) Lactic acid. There was a correlation between the concentration of lactic acid in the Lactobacillus-CM and its ability to suppress HIV-1 infection in human tissues ex vivo. Addition of lactic acid isomers D and L to tissue culture medium at the concentration that corresponded to their amount released by lactobacilli resulted in HIV-1 inhibition. Isomer L was produced in higher quantities than isomer D and was mostly responsible for HIV-1 inhibition. These results indicate that lactic acid, in particular its L-isomer, inhibits HIV-1 independently of lowering of the pH. (iii) Virucidal effect. Incubation of HIV-1 in Lactobacillus-CM significantly suppressed viral infectivity for human tissues ex vivo. Finally, lactobacilli adsorb HIV-1, serving as a sink decreasing the number of free virions. In summary, we found that lactobacilli inhibit HIV-1 replication in human tissue ex vivo by multiple mechanisms. Further studies are needed to evaluate the potential of altering the spectra of vaginal microbiota as an effective strategy to enhance vaginal health. Human tissues ex vivo may serve as a test system for these strategies.

Histocultures (tissue explants) in human retrovirology

Viral pathogenesis is studied predominantly in cultures of primary isolated cells or cell lines. Many retroviruses efficiently replicate only in activated cells. Therefore, in order to become efficient viral producers cells should be artificially activated, a procedure which significantly changes cell physiology. However, for many viral diseases, like HIV-1 and other retroviruses' diseases, critical pathogenic events occur in tissues. Therefore, cell isolation from their native microenvironment prevents single-cell cultures from faithfully reflecting important aspects of cell-cell and cell-pathogen interactions that occur in the context of complex tissue cytoarchitecture. Tissue explants (histocultures) that retain tissue cytoarchitecture and many aspects of cell-cell interactions more faithfully represent in vivo tissue features. Human histocultures constitute an adequate model for studying viral pathogenesis under controlled laboratory conditions. Protocols for various human histocultures as applied to study retroviral pathogenesis, in particular of HIV-1, have been refined by our laboratory and are described in the present publication. Histocultures of human tonsils and lymph nodes, as well as of recto-sigmoid and cervicovaginal tissues can be used to study viral transmission, pathogenesis and as a preclinical platform for antivirals evaluation.

Cervico-vaginal tissue ex vivo as a model to study early events in HIV-1 infection

Vaginal intercourse remains the most prevalent route of infection of women. In spite of many efforts, the detailed mechanisms of HIV-1 transmission in the female lower genital tract remain largely unknown. With all the obvious restrictions on studying these mechanisms in humans, their understanding depends on the development of adequate experimental models. Isolated cell cultures do not faithfully reproduce important aspects of cell-cell interactions in living tissues and tissue responses to pathogens. Explants and other types of ex vivo tissue models serve as a bridge between cell culture and tissues in vivo. Herein, we discuss various cervico-vaginal tissue models and their use in studying HIV vaginal transmission and consider future directions of such studies.

Contrasting roles for TLR ligands in HIV-1 pathogenesis

The first line of a host's response to various pathogens is triggered by their engagement of cellular pattern recognition receptors (PRRs). Binding of microbial ligands to these receptors leads to the induction of a variety of cellular factors that alter intracellular and extracellular environment and interfere directly or indirectly with the life cycle of the triggering pathogen. Such changes may also affect any coinfecting microbe. Using ligands to Toll-like receptors (TLRs) 5 and 9, we examined their effect on human immunodeficiency virus (HIV)-1 replication in lymphoid tissue ex vivo. We found marked differences in the outcomes of such treatment. While flagellin (TLR5 agonist) treatment enhanced replication of CC chemokine receptor 5 (CCR 5)-tropic and CXC chemokine receptor 4 (CXCR4)-tropic HIV-1, treatment with oligodeoxynucleotide (ODN) M362 (TLR9 agonist) suppressed both viral variants. The differential effects of these TLR ligands on HIV-1 replication correlated with changes in production of CC chemokines CCL3, CCL4, CCL5, and of CXC chemokines CXCL10, and CXCL12 in the ligand-treated HIV-1-infected tissues. The nature and/or magnitude of these changes were dependent on the ligand as well as on the HIV-1 viral strain. Moreover, the tested ligands differed in their ability to induce cellular activation as evaluated by the expression of the cluster of differentiation markers (CD) 25, CD38, CD39, CD69, CD154, and human leukocyte antigen D related (HLA)-DR as well as of a cell proliferation marker, Ki67, and of CCR5. No significant effect of the ligand treatment was observed on apoptosis and cell death/loss in the treated lymphoid tissue ex vivo. Our results suggest that binding of microbial ligands to TLRs is one of the mechanisms that mediate interactions between coinfected microbes and HIV-1 in human tissues. Thus, the engagement of appropriate TLRs by microbial molecules or their mimetic might become a new strategy for HIV therapy or prevention.

Toxoplasma gondii inhibits R5 HIV-1 replication in human lymphoid tissues ex vivo

Critical events of HIV-1 pathogenesis occur in lymphoid tissues where HIV-1 is typically accompanied by infections with other pathogens (HIV co-pathogens). Co-pathogens greatly affect the clinical course of the disease and the transmission of HIV. The apicomplexan parasite Toxoplasma gondii is a common HIV co-pathogen associated with AIDS development. Here, we examined the interaction of T. gondii and HIV in coinfected human lymphoid tissue ex vivo. Both pathogens readily replicate in ex vivo infected blocks of human tonsillar tissue. Surprisingly, we found that live T. gondii preferentially inhibits R5 HIV-1 replication in coinfected tissues. This effect is reproduced by treatment of the tissue blocks with recombinant C-18, a T. gondii-encoded cyclophilin that binds to CCR5. These ex vivo findings raise the possibility that, in addition to being a co-factor in HIV disease, T. gondii may influence the outcome of viral infection by preferentially suppressing R5 variants.

Interactions between viral and prokaryotic pathogens in a mixed infection with cardiovirus and mycoplasma

In the natural environment, animal and plant viruses often share ecological niches with microorganisms, but the interactions between these pathogens, although potentially having important implications, are poorly investigated. The present report demonstrates, in a model system, profound mutual effects of mycoplasma and cardioviruses in animal cell cultures. In contrast to mycoplasma-free cells, cultures contaminated with Mycoplasma hyorhinis responded to infection with encephalomyocarditis virus (EMCV), a picornavirus, but not with poliovirus (also a picornavirus), with a strong activation of a DNase(s), as evidenced by the TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) immunofluorescence assay and electrophoretic analysis of host DNA. This degradation was reminiscent of that observed upon apoptosis but was caspase independent, judging by the failure of the specific pan-caspase inhibitor Q-VD-OPh to prevent it. The electrophoretic mobility of the enzyme responsible for DNA degradation and dependence of its activity on ionic conditions strongly suggested that it was represented by a DNase(s) of mycoplasma origin. In cells not infected with EMCV, the relevant DNase was dormant. The possibility is discussed that activation of the mycoplasma DNase might be linked to a relatively early increase in permeability of plasma membrane of the infected cells caused by EMCV. This type of unanticipated virus-mycoplasma "cooperation" may exemplify the complexity of pathogen-host interactions under conditions when viruses and microorganisms are infecting the same host. In the course of the present study, it was also demonstrated that pan-caspase inhibitor zVAD(OMe).fmk strongly suppressed cardiovirus polyprotein processing, illustrating an additional pitfall in investigations of viral effects on the apoptotic system of host cells.

Use of human tissue explants to study human infectious agents

The study of human cell-cell and cell-pathogen interactions that occur in the context of complex tissue cytoarchitecture is critical for deciphering the mechanisms of many normal and pathogenic processes. This protocol describes methods for culturing and infecting explants of human tissues to study the pathogenesis of human infectious agents and their local interactions. The protocol relies on the use of fresh human tissues dissected into small blocks or biopsies that are cultured at the liquid-air interface on collagen rafts. These tissue blocks retain their cytoarchitecture and support productive infection of various pathogens without exogenous stimulation. Experimental details for setting up cultures of human tonsils, lymph nodes and cervicovaginal and rectosigmoid tissues, including protocols for their infection with HIV-1 and other pathogens, are described here. Using this protocol, culture and infections can be set up in 3-6 h and be maintained for 2-3 weeks, depending on the tissue used.

Characterization of a peptide domain within the GB virus C NS5A phosphoprotein that inhibits HIV replication

Background

GBV-C infection is associated with prolonged survival in HIV-infected people and GBV-C inhibits HIV replication in co-infection models. Expression of the GBV-C nonstructural phosphoprotein 5A (NS5A) decreases surface levels of the HIV co-receptor CXCR4, induces the release of SDF-1 and inhibits HIV replication in Jurkat CD4+ T cell lines.

Methodology/Principal Findings

Jurkat cell lines stably expressing NS5A protein and peptides were generated and HIV replication in these cell lines assessed. HIV replication was significantly inhibited in all cell lines expressing NS5A amino acids 152–165. Substitution of an either alanine or glycine for the serine at position 158 (S158A or S158G) resulted in a significant decrease in the HIV inhibitory effect. In contrast, substituting a phosphomimetic amino acid (glutamic acid; S158E) inhibited HIV as well as the parent peptide. HIV inhibition was associated with lower levels of surface expression of the HIV co-receptor CXCR4 and increased release of the CXCR4 ligand, SDF-1 compared to control cells. Incubation of CD4+ T cell lines with synthetic peptides containing amino acids 152–167 or the S158E mutant peptide prior to HIV infection resulted in HIV replication inhibition compared to control peptides.

Conclusions/Significance

Expression of GBV-C NS5A amino acids 152–165 are sufficient to inhibit HIV replication in vitro, and the serine at position 158 appears important for this effect through either phosphorylation or structural changes in this peptide. The addition of synthetic peptides containing 152–167 or the S158E substitution to Jurkat cells resulted in HIV replication inhibition in vitro. These data suggest that GBV-C peptides or a peptide mimetic may offer a novel, cellular-based approach to antiretroviral therapy.