Analyses of human vaccine-specific circulating and bone marrow-resident B cell populations reveal benefit of delayed vaccine booster dosing with blood-stage malaria antigens

We have previously reported primary endpoints of a clinical trial testing two vaccine platforms for the delivery of Plasmodium vivax malaria DBPRII: viral vectors (ChAd63, MVA), and protein/adjuvant (PvDBPII with 50µg Matrix-M™ adjuvant). Delayed boosting was necessitated due to trial halts during the pandemic and provides an opportunity to investigate the impact of dosing regimens. Here, using flow cytometry - including agnostic definition of B cell populations with the clustering tool CITRUS - we report enhanced induction of DBPRII-specific plasma cell and memory B cell responses in protein/adjuvant versus viral vector vaccinees. Within protein/adjuvant groups, delayed boosting further improved B cell immunogenicity compared to a monthly boosting regimen. Consistent with this, delayed boosting also drove more durable anti-DBPRII serum IgG. In an independent vaccine clinical trial with the P. falciparum malaria RH5.1 protein/adjuvant (50µg Matrix-M™) vaccine candidate, we similarly observed enhanced circulating B cell responses in vaccinees receiving a delayed final booster. Notably, a higher frequency of vaccine-specific (putatively long-lived) plasma cells was detected in the bone marrow of these delayed boosting vaccinees by ELISPOT and correlated strongly with serum IgG. Finally, following controlled human malaria infection with P. vivax parasites in the DBPRII trial, in vivo growth inhibition was observed to correlate with DBPRII-specific B cell and serum IgG responses. In contrast, the CD4+ and CD8+ T cell responses were impacted by vaccine platform but not dosing regimen and did not correlate with in vivo growth inhibition in a challenge model. Taken together, our DBPRII and RH5 data suggest an opportunity for protein/adjuvant dosing regimen optimisation in the context of rational vaccine development against pathogens where protection is antibody-mediated.

PvDBPII elicits multiple antibody-mediated mechanisms that reduce growth in a Plasmodium vivax challenge trial

The receptor-binding domain, region II, of the Plasmodium vivax Duffy binding protein (PvDBPII) binds the Duffy antigen on the reticulocyte surface to mediate invasion. A heterologous vaccine challenge trial recently showed that a delayed dosing regimen with recombinant PvDBPII SalI variant formulated with adjuvant Matrix-MTM reduced the in vivo parasite multiplication rate (PMR) in immunized volunteers challenged with the Thai P. vivax isolate PvW1. Here, we describe extensive analysis of the polyfunctional antibody responses elicited by PvDBPII immunization and identify immune correlates for PMR reduction. A classification algorithm identified antibody features that significantly contribute to PMR reduction. These included antibody titre, receptor-binding inhibitory titre, dissociation constant of the PvDBPII-antibody interaction, complement C1q and Fc gamma receptor binding and specific IgG subclasses. These data suggest that multiple immune mechanisms elicited by PvDBPII immunization are likely to be associated with protection and the immune correlates identified could guide the development of an effective vaccine for P. vivax malaria. Importantly, all the polyfunctional antibody features that correlated with protection cross-reacted with both PvDBPII SalI and PvW1 variants, suggesting that immunization with PvDBPII should protect against diverse P. vivax isolates.

Superior antibody immunogenicity of a viral-vectored RH5 blood-stage malaria vaccine in Tanzanian infants as compared to adults

BACKGROUND

RH5 is a leading blood-stage candidate antigen for a Plasmodium falciparum vaccine; however, its safety and immunogenicity in malaria-endemic populations are unknown.

METHODS

A phase 1b, single-center, dose-escalation, age-de-escalation, double-blind, randomized, controlled trial was conducted in Bagamoyo, Tanzania (NCT03435874). Between 12th April and 25th October 2018, 63 healthy adults (18-35 years), young children (1-6 years), and infants (6-11 months) received a priming dose of viral-vectored ChAd63 RH5 or rabies control vaccine. Sixty participants were boosted with modified vaccinia virus Ankara (MVA) RH5 or rabies control vaccine 8 weeks later and completed 6 months of follow-up post priming. Primary outcomes were the number of solicited and unsolicited adverse events post vaccination and the number of serious adverse events over the study period. Secondary outcomes included measures of the anti-RH5 immune response.

FINDINGS

Vaccinations were well tolerated, with profiles comparable across groups. No serious adverse events were reported. Vaccination induced RH5-specific cellular and humoral responses. Higher anti-RH5 serum immunoglobulin G (IgG) responses were observed post boost in young children and infants compared to adults. Vaccine-induced antibodies showed growth inhibition activity (GIA) in vitro against P. falciparum blood-stage parasites; their highest levels were observed in infants.

CONCLUSIONS

The ChAd63-MVA RH5 vaccine shows acceptable safety and reactogenicity and encouraging immunogenicity in children and infants residing in a malaria-endemic area. The levels of functional GIA observed in RH5-vaccinated infants are the highest reported to date following human vaccination. These data support onward clinical development of RH5-based blood-stage vaccines to protect against clinical malaria in young African infants.

FUNDING

Medical Research Council, London, UK.

Vaccination with Plasmodium vivax Duffy-binding protein inhibits parasite growth during controlled human malaria infection

There are no licensed vaccines against Plasmodium vivax. We conducted two phase 1/2a clinical trials to assess two vaccines targeting P. vivax Duffy-binding protein region II (PvDBPII). Recombinant viral vaccines using chimpanzee adenovirus 63 (ChAd63) and modified vaccinia virus Ankara (MVA) vectors as well as a protein and adjuvant formulation (PvDBPII/Matrix-M) were tested in both a standard and a delayed dosing regimen. Volunteers underwent controlled human malaria infection (CHMI) after their last vaccination, alongside unvaccinated controls. Efficacy was assessed by comparisons of parasite multiplication rates in the blood. PvDBPII/Matrix-M, given in a delayed dosing regimen, elicited the highest antibody responses and reduced the mean parasite multiplication rate after CHMI by 51% (n = 6) compared with unvaccinated controls (n = 13), whereas no other vaccine or regimen affected parasite growth. Both viral-vectored and protein vaccines were well tolerated and elicited expected, short-lived adverse events. Together, these results support further clinical evaluation of the PvDBPII/Matrix-M P. vivax vaccine.

Delayed boosting improves human antigen-specific Ig and B cell responses to the RH5.1/AS01B malaria vaccine

Modifications to vaccine delivery that increase serum antibody longevity are of great interest for maximizing efficacy. We have previously shown that a delayed fractional (DFx) dosing schedule (0-1-6 month) - using AS01B-adjuvanted RH5.1 malaria antigen - substantially improves serum IgG durability as compared with monthly dosing (0-1-2 month; NCT02927145). However, the underlying mechanism and whether there are wider immunological changes with DFx dosing were unclear. Here, PfRH5-specific Ig and B cell responses were analyzed in depth through standardized ELISAs, flow cytometry, systems serology, and single-cell RNA-Seq (scRNA-Seq). Data indicate that DFx dosing increases the magnitude and durability of circulating PfRH5-specific B cells and serum IgG1. At the peak antibody magnitude, DFx dosing was distinguished by a systems serology feature set comprising increased FcRn binding, IgG avidity, and proportion of G2B and G2S2F IgG Fc glycans, alongside decreased IgG3, antibody-dependent complement deposition, and proportion of G1S1F IgG Fc glycan. Concomitantly, scRNA-Seq data show a higher CDR3 percentage of mutation from germline and decreased plasma cell gene expression in circulating PfRH5-specific B cells. Our data, therefore, reveal a profound impact of DFx dosing on the humoral response and suggest plausible mechanisms that could enhance antibody longevity, including improved FcRn binding by serum Ig and a potential shift in the underlying cellular response from circulating short-lived plasma cells to nonperipheral long-lived plasma cells.

Human lymphoid tissue sampling for vaccinology

Long-lived plasma cells (LLPCs) - largely resident in the bone marrow - secrete antibody over months and years, thus maintaining serum antibody concentrations relevant for vaccine-mediated immunity. Little is known regarding factors that can modulate the induction of human LLPC responses in draining lymph node germinal centres, or those that maintain LLPCs in bone marrow niches following vaccination. Here, we review human and non-human primate vaccination studies which incorporate draining lymph node and/or bone marrow aspirate sampling. We emphasise the key contributions these samples can make to improve our understanding of LLPC immunology and guide rational vaccine development. Specifically, we highlight findings related to the impact of vaccine dosing regimens, adjuvant/vaccine platform selection, duration of germinal centre reactions in draining lymph nodes and relevance for timing of tissue sampling, and heterogeneity in bone marrow plasma cell populations. Much of this work has come from recent studies with SARS-CoV-2 vaccine candidates or, with respect to the non-human primate work, HIV vaccine development.

Repeat controlled human malaria infection of healthy UK adults with blood-stage Plasmodium falciparum: Safety and parasite growth dynamics

In endemic settings it is known that natural malaria immunity is gradually acquired following repeated exposures. Here we sought to assess whether similar acquisition of blood-stage malaria immunity would occur following repeated parasite exposure by controlled human malaria infection (CHMI). We report the findings of repeat homologous blood-stage Plasmodium falciparum (3D7 clone) CHMI studies VAC063C (ClinicalTrials.gov NCT03906474) and VAC063 (ClinicalTrials.gov NCT02927145). In total, 24 healthy, unvaccinated, malaria-naïve UK adult participants underwent primary CHMI followed by drug treatment. Ten of these then underwent secondary CHMI in the same manner, and then six of these underwent a final tertiary CHMI. As with primary CHMI, malaria symptoms were common following secondary and tertiary infection, however, most resolved within a few days of treatment and there were no long term sequelae or serious adverse events related to CHMI. Despite detectable induction and boosting of anti-merozoite serum IgG antibody responses following each round of CHMI, there was no clear evidence of anti-parasite immunity (manifest as reduced parasite growth in vivo) conferred by repeated challenge with the homologous parasite in the majority of volunteers. However, three volunteers showed some variation in parasite growth dynamics in vivo following repeat CHMI that were either modest or short-lived. We also observed no major differences in clinical symptoms or laboratory markers of infection across the primary, secondary and tertiary challenges. However, there was a trend to more severe pyrexia after primary CHMI and the absence of a detectable transaminitis post-treatment following secondary and tertiary infection. We hypothesize that this could represent the initial induction of clinical immunity. Repeat homologous blood-stage CHMI is thus safe and provides a model with the potential to further the understanding of naturally acquired immunity to blood-stage infection in a highly controlled setting.

Impact of a blood-stage vaccine on Plasmodium vivax malaria

Background

There are no licensed vaccines against Plasmodium vivax , the most common cause of malaria outside of Africa.

Methods

We conducted two Phase I/IIa clinical trials to assess the safety, immunogenicity and efficacy of two vaccines targeting region II of P. vivax Duffy-binding protein (PvDBPII). Recombinant viral vaccines (using ChAd63 and MVA vectors) were administered at 0, 2 months or in a delayed dosing regimen (0, 17, 19 months), whilst a protein/adjuvant formulation (PvDBPII/Matrix-M™) was administered monthly (0, 1, 2 months) or in a delayed dosing regimen (0, 1, 14 months). Delayed regimens were due to trial halts during the COVID-19 pandemic. Volunteers underwent heterologous controlled human malaria infection (CHMI) with blood-stage P. vivax parasites at 2-4 weeks following their last vaccination, alongside unvaccinated controls. Efficacy was assessed by comparison of parasite multiplication rate (PMR) in blood post-CHMI, modelled from parasitemia measured by quantitative polymerase-chain-reaction (qPCR).

Results

Thirty-two volunteers were enrolled and vaccinated (n=16 for each vaccine). No safety concerns were identified. PvDBPII/Matrix-M™, given in the delayed dosing regimen, elicited the highest antibody responses and reduced the mean PMR following CHMI by 51% (range 36-66%; n=6) compared to unvaccinated controls (n=13). No other vaccine or regimen impacted parasite growth. In vivo growth inhibition of blood-stage P. vivax correlated with functional antibody readouts of vaccine immunogenicity.

Conclusions

Vaccination of malaria-naïve adults with a delayed booster regimen of PvDBPII/ Matrix-M™ significantly reduces the growth of blood-stage P. vivax . Funded by the European Commission and Wellcome Trust; VAC069, VAC071 and VAC079 ClinicalTrials.gov numbers NCT03797989 , NCT04009096 and NCT04201431 .

Poor CD4+ T Cell Immunogenicity Limits Humoral Immunity to P. falciparum Transmission-Blocking Candidate Pfs25 in Humans

Plasmodium falciparum transmission-blocking vaccines (TBVs) targeting the Pfs25 antigen have shown promise in mice but the same efficacy has never been achieved in humans. We have previously published pre-clinical data related to a TBV candidate Pfs25-IMX313 encoded in viral vectors which was very promising and hence progressed to human clinical trials. The results from the clinical trial of this vaccine were very modest. Here we unravel why, contrary to mice, this vaccine has failed to induce robust antibody (Ab) titres in humans to elicit transmission-blocking activity. We examined Pfs25-specific B cell and T follicular helper (Tfh) cell responses in mice and humans after vaccination with Pfs25-IMX313 encoded by replication-deficient chimpanzee adenovirus serotype 63 (ChAd63) and the attenuated orthopoxvirus modified vaccinia virus Ankara (MVA) delivered in the heterologous prime-boost regimen via intramuscular route. We found that after vaccination, the Pfs25-IMX313 was immunologically suboptimal in humans compared to mice in terms of serum Ab production and antigen-specific B, CD4⁺ and Tfh cell responses. We identified that the key determinant for the poor anti-Pfs25 Ab formation in humans was the lack of CD4⁺ T cell recognition of Pfs25-IMX313 derived peptide epitopes. This is supported by correlations established between the ratio of proliferated antigen-specific CD4⁺/Tfh-like T cells, CXCL13 sera levels, and the corresponding numbers of circulating Pfs25-specific memory B cells, that consequently reflected on antigen-specific IgG sera levels. These correlations can inform the design of next-generation Pfs25-based vaccines for robust and durable blocking of malaria transmission.

Controlled human malaria infection with a clone of Plasmodium vivax with high quality genome assembly

Controlled human malaria infection (CHMI) provides a highly informative means to investigate host-pathogen interactions and enable in vivo proof-of-concept efficacy testing of new drugs and vaccines. However, unlike Plasmodium falciparum, well-characterized P. vivax parasites that are safe and suitable for use in modern CHMI models are limited. Here, two healthy malaria-naïve UK adults with universal donor blood group were safely infected with a clone of P. vivax from Thailand by mosquito-bite CHMI. Parasitemia developed in both volunteers and, prior to treatment, each volunteer donated blood to produce a cryopreserved stabilate of infected red blood cells. Following stringent safety screening, the parasite stabilate from one of these donors ("PvW1") was thawed and used to inoculate six healthy malaria-naïve UK adults by blood-stage CHMI, at three different dilutions. Parasitemia developed in all volunteers, who were then successfully drug treated. PvW1 parasite DNA was isolated and sequenced to produce a high quality genome assembly by using a hybrid assembly method. We analysed leading vaccine candidate antigens and multigene families, including the Vivax interspersed repeat (VIR) genes of which we identified 1145 in the PvW1 genome. Our genomic analysis will guide future assessment of candidate vaccines and drugs, as well as experimental medicine studies.

Identification and Immune Assessment of T Cell Epitopes in Five Plasmodium falciparum Blood Stage Antigens to Facilitate Vaccine Candidate Selection and Optimization

The hurdles to effective blood stage malaria vaccine design include immune evasion tactics used by the parasite such as redundant invasion pathways and antigen variation among circulating parasite strains. While blood stage malaria vaccine development primarily focuses on eliciting optimal humoral responses capable of blocking erythrocyte invasion, clinically-tested Plasmodium falciparum (Pf) vaccines have not elicited sterile protection, in part due to the dramatically high levels of antibody needed. Recent development efforts with non-redundant, conserved blood stage antigens suggest both high antibody titer and rapid antibody binding kinetics are important efficacy factors. Based on the central role of helper CD4 T cells in development of strong, protective immune responses, we systematically analyzed the class II epitope content in five leading Pf blood stage antigens (RH5, CyRPA, RIPR, AMA1 and EBA175) using in silico, in vitro, and ex vivo methodologies. We employed in silico T cell epitope analysis to enable identification of 67 HLA-restricted class II epitope clusters predicted to bind a panel of nine HLA-DRB1 alleles. We assessed a subset of these for HLA-DRB1 allele binding in vitro, to verify the in silico predictions. All clusters assessed (40 clusters represented by 46 peptides) bound at least two HLA-DR alleles in vitro. The overall epitope prediction to in vitro HLA-DRB1 allele binding accuracy was 71%. Utilizing the set of RH5 class II epitope clusters (10 clusters represented by 12 peptides), we assessed stimulation of T cells collected from HLA-matched RH5 vaccinees using an IFN-γ T cell recall assay. All clusters demonstrated positive recall responses, with the highest responses – by percentage of responders and response magnitude – associated with clusters located in the N-terminal region of RH5. Finally, a statistically significant correlation between in silico epitope predictions and ex vivo IFN-γ recall response was found when accounting for HLA-DR matches between the epitope predictions and donor HLA phenotypes. This is the first comprehensive analysis of class II epitope content in RH5, CyRPA, RIPR, AMA1 and EBA175 accompanied by in vitro HLA binding validation for all five proteins and ex vivo T cell response confirmation for RH5.

Reduced blood-stage malaria growth and immune correlates in humans following RH5 vaccination

BACKGROUND

Development of an effective vaccine against the pathogenic blood-stage infection of human malaria has proved challenging, and no candidate vaccine has affected blood-stage parasitemia following controlled human malaria infection (CHMI) with blood-stage Plasmodium falciparum.

METHODS

We undertook a phase I/IIa clinical trial in healthy adults in the United Kingdom of the RH5.1 recombinant protein vaccine, targeting the P. falciparum reticulocyte-binding protein homolog 5 (RH5), formulated in AS01B adjuvant. We assessed safety, immunogenicity, and efficacy against blood-stage CHMI. Trial registered at ClinicalTrials.gov, NCT02927145.

FINDINGS

The RH5.1/AS01B formulation was administered using a range of RH5.1 protein vaccine doses (2, 10, and 50 μg) and was found to be safe and well tolerated. A regimen using a delayed and fractional third dose, in contrast to three doses given at monthly intervals, led to significantly improved antibody response longevity over ∼2 years of follow-up. Following primary and secondary CHMI of vaccinees with blood-stage P. falciparum, a significant reduction in parasite growth rate was observed, defining a milestone for the blood-stage malaria vaccine field. We show that growth inhibition activity measured in vitro using purified immunoglobulin G (IgG) antibody strongly correlates with in vivo reduction of the parasite growth rate and also identify other antibody feature sets by systems serology, including the plasma anti-RH5 IgA1 response, that are associated with challenge outcome.

CONCLUSIONS

Our data provide a new framework to guide rational design and delivery of next-generation vaccines to protect against malaria disease.

FUNDING

This study was supported by USAID, UK MRC, Wellcome Trust, NIAID, and the NIHR Oxford-BRC.

Age-Related Dynamics of Circulating Innate Lymphoid Cells in an African Population

Innate lymphoid cell (ILC) lineages mirror those of CD4+ T helper cell subsets, producing type 1, 2 and 3 cytokines respectively. Studies in adult human populations have shown contributions of non-cytotoxic ILC to immune regulation or pathogenesis in a wide range of diseases and have prompted investigations of potential functional redundancy between ILC and T helper cell compartments in neonates and children. To investigate the potential for ILC to contribute to immune responses across the human lifespan, we examined the numbers and frequencies of peripheral blood ILC subsets in a cohort of Gambians aged between 5 and 73 years of age. ILC2 were the most abundant peripheral blood ILC subset in this Gambian cohort, while ILC1 were the rarest at all ages. Moreover, the frequency of ILC1s (as a proportion of all lymphocytes) was remarkably stable over the life course whereas ILC3 cell frequencies and absolute numbers declined steadily across the life course and ILC2 frequencies and absolute numbers declined from childhood until the age of approx. 30 years of age. Age-related reductions in ILC2 cell numbers appeared to be partially offset by increasing numbers of total and GATA3+ central memory (CD45RA-CCR7+) CD4+ T cells, although there was also a gradual decline in numbers of total and GATA3+ effector memory (CD45RA-CCR7-) CD4+ T cells. Despite reduced overall abundance of ILC2 cells, we observed a coincident increase in the proportion of CD117+ ILC2, indicating potential for age-related adaptation of these cells in childhood and early adulthood. While both CD117+ and CD117- ILC2 cells produced IL-13, these responses occurred predominantly within CD117- cells. Furthermore, comparison of ILC frequencies between aged-matched Gambian and UK young adults (25–29 years) revealed an overall higher proportion of ILC1 and ILC2, but not ILC3 in Gambians. Thus, these data indicate ongoing age-related changes in ILC2 cells throughout life, which retain the capacity to differentiate into potent type 2 cytokine producing cells, consistent with an ongoing role in immune modulation.

The Application of Single-Cell RNA Sequencing in Vaccinology

Single-cell RNA sequencing allows highly detailed profiling of cellular immune responses from limited-volume samples, advancing prospects of a new era of systems immunology. The power of single-cell RNA sequencing offers various opportunities to decipher the immune response to infectious diseases and vaccines. Here, we describe the potential uses of single-cell RNA sequencing methods in prophylactic vaccine development, concentrating on infectious diseases including COVID-19. Using examples from several diseases, we review how single-cell RNA sequencing has been used to evaluate the immunological response to different vaccine platforms and regimens. By highlighting published and unpublished single-cell RNA sequencing studies relevant to vaccinology, we discuss some general considerations how the field could be enriched with the widespread adoption of this technology.

Better Epitope Discovery, Precision Immune Engineering, and Accelerated Vaccine Design Using Immunoinformatics Tools

Computational vaccinology includes epitope mapping, antigen selection, and immunogen design using computational tools. Tools that facilitate the in silico prediction of immune response to biothreats, emerging infectious diseases, and cancers can accelerate the design of novel and next generation vaccines and their delivery to the clinic. Over the past 20 years, vaccinologists, bioinformatics experts, and advanced programmers based in Providence, Rhode Island, USA have advanced the development of an integrated toolkit for vaccine design called iVAX, that is secure and user-accessible by internet. This integrated set of immunoinformatic tools comprises algorithms for scoring and triaging candidate antigens, selecting immunogenic and conserved T cell epitopes, re-engineering or eliminating regulatory T cell epitopes, and re-designing antigens to induce immunogenicity and protection against disease for humans and livestock. Commercial and academic applications of iVAX have included identifying immunogenic T cell epitopes in the development of a T-cell based human multi-epitope Q fever vaccine, designing novel influenza vaccines, identifying cross-conserved T cell epitopes for a malaria vaccine, and analyzing immune responses in clinical vaccine studies. Animal vaccine applications to date have included viral infections of pigs such as swine influenza A, PCV2, and African Swine Fever. “Rapid-Fire” applications for biodefense have included a demonstration project for Lassa Fever and Q fever. As recent infectious disease outbreaks underscore the significance of vaccine-driven preparedness, the integrated set of tools available on the iVAX toolkit stand ready to help vaccine developers deliver genome-derived, epitope-driven vaccines.

IL-15 Promotes Polyfunctional NK Cell Responses to Influenza by Boosting IL-12 Production

IL-15 is a key regulator of NK cell maintenance and proliferation and synergizes with other myeloid cell–derived cytokines to enhance NK cell effector function. At low concentrations, trans-presentation of IL-15 by dendritic cells can activate NK cells, whereas at higher concentrations it can act directly on NK cells, independently of accessory cells. In this study, we investigate the potential for IL-15 to boost responses to influenza virus by promoting accessory cell function. We find that coculture of human PBMCs with inactivated whole influenza virus (A/Victoria/361/2011) in the presence of very low concentrations of IL-15 results in increased production of myeloid cell–derived cytokines, including IL-12, IFN-α2, GM-CSF, and IL-1β, and an increased frequency of polyfunctional NK cells (defined by the expression of two or more of CD107a, IFN-γ, and CD25). Neutralization experiments demonstrate that IL-15–mediated enhancement of NK cell responses is primarily dependent on IL-12 and partially dependent on IFN-αβR1 signaling. Critically, IL-15 boosted the production of IL-12 in influenza-stimulated blood myeloid dendritic cells. IL-15 costimulation also restored the ability of less-differentiated NK cells from human CMV-seropositive individuals to respond to influenza virus. These data suggest that very low concentrations of IL-15 play an important role in boosting accessory cell function to support NK cell effector functions.

Human vaccination against RH5 induces neutralizing antimalarial antibodies that inhibit RH5 invasion complex interactions

The development of a highly effective vaccine remains a key strategic goal to aid the control and eventual eradication of Plasmodium falciparum malaria. In recent years, the reticulocyte-binding protein homolog 5 (RH5) has emerged as the most promising blood-stage P. falciparum candidate antigen to date, capable of conferring protection against stringent challenge in Aotus monkeys. We report on the first clinical trial to our knowledge to assess the RH5 antigen - a dose-escalation phase Ia study in 24 healthy, malaria-naive adult volunteers. We utilized established viral vectors, the replication-deficient chimpanzee adenovirus serotype 63 (ChAd63), and the attenuated orthopoxvirus modified vaccinia virus Ankara (MVA), encoding RH5 from the 3D7 clone of P. falciparum. Vaccines were administered i.m. in a heterologous prime-boost regimen using an 8-week interval and were well tolerated. Vaccine-induced anti-RH5 serum antibodies exhibited cross-strain functional growth inhibition activity (GIA) in vitro, targeted linear and conformational epitopes within RH5, and inhibited key interactions within the RH5 invasion complex. This is the first time to our knowledge that substantial RH5-specific responses have been induced by immunization in humans, with levels greatly exceeding the serum antibody responses observed in African adults following years of natural malaria exposure. These data support the progression of RH5-based vaccines to human efficacy testing.

Calorie Restriction Attenuates Terminal Differentiation of Immune Cells

Immune senescence is a natural consequence of aging and may contribute to frailty and loss of homeostasis in later life. Calorie restriction increases healthy life-span in C57BL/6J (but not DBA/2J) mice, but whether this is related to preservation of immune function, and how it interacts with aging, is unclear. We compared phenotypic and functional characteristics of natural killer (NK) cells and T cells, across the lifespan, of calorie-restricted (CR) and control C57BL/6 and DBA/2 mice. Calorie restriction preserves a naïve T cell phenotype and an immature NK cell phenotype as mice age. The splenic T cell populations of CR mice had higher proportions of CD11a^-CD44^lo cells, lower expression of TRAIL, KLRG1, and CXCR3, and higher expression of CD127, compared to control mice. Similarly, splenic NK cells from CR mice had higher proportions of less differentiated CD11b^-CD27⁺ cells and correspondingly lower proportions of highly differentiated CD11b⁺CD27^-NK cells. Within each of these subsets, cells from CR mice had higher expression of CD127, CD25, TRAIL, NKG2A/C/E, and CXCR3 and lower expression of KLRG1 and Ly49 receptors compared to controls. The effects of calorie restriction on lymphoid cell populations in lung, liver, and lymph nodes were identical to those seen in the spleen, indicating that this is a system-wide effect. The impact of calorie restriction on NK cell and T cell maturation is much more profound than the effect of aging and, indeed, calorie restriction attenuates these age-associated changes. Importantly, the effects of calorie restriction on lymphocyte maturation were more marked in C57BL/6 than in DBA/2J mice indicating that delayed lymphocyte maturation correlates with extended lifespan. These findings have implications for understanding the interaction between nutritional status, immunity, and healthy lifespan in aging populations.

Influenza Vaccination Generates Cytokine-Induced Memory-like NK Cells: Impact of Human Cytomegalovirus Infection

Human NK cells are activated by cytokines, immune complexes, and signals transduced via activating ligands on other host cells. After vaccination, or during secondary infection, adaptive immune responses can enhance both cytokine-driven and Ab-dependent NK cell responses. However, induction of NK cells for enhanced function after in vitro exposure to innate inflammatory cytokines has also been reported and may synergize with adaptive signals to potentiate NK cell activity during infection or vaccination. To test this hypothesis, we examined the effect of seasonal influenza vaccination on NK cell function and phenotype in 52 previously unvaccinated individuals. Enhanced, IL-2–dependent, NK cell IFN-γ responses to Influenza A/California/7/2009 virus were detected up to 4 wk postvaccination and higher in human CMV (HCMV)-seronegative (HCMV⁻) individuals than in HCMV-seropositive (HCMV⁺) individuals. By comparison, robust NK cell degranulation responses were observed both before and after vaccination, due to high titers of naturally occurring anti-influenza Abs in human plasma, and did not differ between HCMV⁺ and HCMV⁻ subjects. In addition to these IL-2–dependent and Ab-dependent responses, NK cell responses to innate cytokines were also enhanced after influenza vaccination; this was associated with proliferation of CD57⁻ NK cells and was most evident in HCMV⁺ subjects. Similar enhancement of cytokine responsiveness was observed when NK cells were cocultured in vitro with Influenza A/California/7/2009 virus, and this was at least partially dependent upon IFN-αβR2. In summary, our data indicate that attenuated or live viral vaccines promote cytokine-induced memory-like NK cells and that this process is influenced by HCMV infection.

Synergy between Common γ Chain Family Cytokines and IL-18 Potentiates Innate and Adaptive Pathways of NK Cell Activation

Studies to develop cell-based therapies for cancer and other diseases have consistently shown that purified human natural killer (NK) cells secrete cytokines and kill target cells after in vitro culture with high concentrations of cytokines. However, these assays poorly reflect the conditions that are likely to prevail in vivo in the early stages of an infection and have been carried out in a wide variety of experimental systems, which has led to contradictions within the literature. We have conducted a detailed kinetic and dose-response analysis of human NK cell responses to low concentrations of IL-12, IL-15, IL-18, IL-21, and IFN-α, alone and in combination, and their potential to synergize with IL-2. We find that very low concentrations of both innate and adaptive common γ chain cytokines synergize with equally low concentrations of IL-18 to drive rapid and potent NK cell CD25 and IFN-γ expression; IL-18 and IL-2 reciprocally sustain CD25 and IL-18Rα expression in a positive feedback loop; and IL-18 synergizes with FcγRIII (CD16) signaling to augment antibody-dependent cellular cytotoxicity. These data indicate that NK cells can be rapidly activated by very low doses of innate cytokines and that the common γ chain cytokines have overlapping but distinct functions in combination with IL-18. Importantly, synergy between multiple signaling pathways leading to rapid NK cell activation at very low cytokine concentrations has been overlooked in prior studies focusing on single cytokines or simple combinations. Moreover, although the precise common γ chain cytokines available during primary and secondary infections may differ, their synergy with both IL-18 and antigen-antibody immune complexes underscores their contribution to NK cell activation during innate and adaptive responses. IL-18 signaling potentiates NK cell effector function during innate and adaptive immune responses by synergy with IL-2, IL-15, and IL-21 and immune complexes.

Reinfection with varicella-zoster virus in immunocompromised patients

A small epidemic of varicella/atypical generalized zoster among 6 immunocompromised patients and one previously healthy person is described. The 6 immunocompromised patients suffered from lymphoproliferative diseases in terminal stages treated with chemotherapy and reported varicella in their childhood. They developed a generalized maculopapular rash with hemorrhagic bullae and necroses. The infection passed from one patient to another during a 3-month period in the department. They were placed in adjacent rooms and nursed by the same staff. The most specific diagnostic tool was the detection of varicella-zoster virus antigen from vesicles by ELISA technique. The epidemic was supposed to be caused by exogenous reinfection with varicella-zoster virus, and illustrated that generalized zoster may be even so infectious as varicella and that immunocompromised patients should be protected against reinfection.

Impaired NK Cell Responses to Pertussis and H1N1 Influenza Vaccine Antigens in Human Cytomegalovirus-Infected Individuals

NK cells contribute to postvaccination immune responses after activation by IL-2 from Ag-specific memory T cells or by cross-linking of the low-affinity IgG receptor, CD16, by Ag–Ab immune complexes. Sensitivity of NK cells to these signals from the adaptive immune system is heterogeneous and influenced by their stage of differentiation. CD56^dimCD57⁺ NK cells are less responsive to IL-2 and produce less IFN-γ in response to T cell–mediated activation than do CD56^bright or CD56^dimCD57⁻ NK cells. Conversely, NK cell cytotoxicity, as measured by degranulation, is maintained across the CD56^dim subsets. Human CMV (HCMV), a highly prevalent herpes virus causing lifelong, usually latent, infections, drives the expansion of the CD56^dimCD57⁺NKG2C⁺ NK cell population, skewing the NK cell repertoire in favor of cytotoxic responses at the expense of cytokine-driven responses. We hypothesized, therefore, that HCMV seropositivity would be associated with altered NK cell responses to vaccine Ags. In a cross-sectional study of 152 U.K. adults, with HCMV seroprevalence rate of 36%, we find that HCMV seropositivity is associated with lower NK cell IFN-γ production and degranulation after in vitro restimulation with pertussis or H1N1 influenza vaccine Ags. Higher expression of CD57/NKG2C and lower expression of IL-18Rα on NK cells from HCMV seropositive subjects do not fully explain these impaired responses, which are likely the result of multiple receptor–ligand interactions. This study demonstrates for the first time, to our knowledge, that HCMV serostatus influences NK cell contributions to adaptive immunity and raises important questions regarding the impact of HCMV infection on vaccine efficacy.

Differential activation of CD57-defined natural killer cell subsets during recall responses to vaccine antigens

Natural killer (NK) cells contribute to the effector phase of vaccine-induced adaptive immune responses, secreting cytokines and releasing cytotoxic granules. The proportion of responding NK cells varies between individuals and by vaccine, suggesting that functionally discrete subsets of NK cells with different activation requirements may be involved. Here, we have used responses to individual components of the DTP vaccine [tetanus toxoid (TT), diphtheria toxoid (DT), whole cell inactivated pertussis] to characterize the NK cell subsets involved in interleukin-2-dependent recall responses. Culture with TT, DT or pertussis induced NK cell CD25 expression and interferon-γ production in previously vaccinated individuals. Responses were the most robust against whole cell pertussis, with responses to TT being particularly low. Functional analysis of discrete NK cell subsets revealed that transition from CD56bright to CD56dim correlated with increased responsiveness to CD16 cross-linking, whereas increasing CD57 expression correlated with a loss of responsiveness to cytokines. A higher frequency of CD56dim CD57− NK cells expressed CD25 and interferon-γ following stimulation with vaccine antigen compared with CD56dim CD57+ NK cells and made the largest overall contribution to this response. CD56dim CD57int NK cells represent an intermediate functional phenotype in response to vaccine-induced and receptor-mediated stimuli. These findings have implications for the ability of NK cells to contribute to the effector response after vaccination and for vaccine-induced immunity in older individuals.

Functional Significance of CD57 Expression on Human NK Cells and Relevance to Disease

Historically, human NK cells have been identified as CD3(-)CD56(+)CD16(±) lymphocytes. More recently it has been established that CD57 expression defines functionally discrete sub-populations of NK cells. On T cells, CD57 expression has been regarded as a marker of terminal differentiation and (perhaps wrongly) of anergy and senescence. Similarly, CD57 expression seems to identify the final stages of peripheral NK cell maturation; its expression increases with age and is associated with chronic infections, particularly human cytomegalovirus infection. However, CD57(+) NK cells are highly cytotoxic and their presence seems to be beneficial in a number of non-communicable diseases. The purpose of this article is to review our current understanding of CD57 expression as a marker of NK cell function and disease prognosis, as well as to outline areas for further research.

Trend towards Decreased Survival in Patients Infected with HIV Resistant to Zidovudine

The survival of 35 patients with AIDS or advanced HIV infection on treatment with zidovudine was related to the viral sensitivity to the drug and to the CD4+ cell count. 14 patients died, the survivors were followed up for an average of 804 days. In a univariate Cox model, survival was strongly related to log IC90 (p = 0.0003) and to the CD4+ count (p = 0.0002). In a bivariate model, log IC90 and the CD4+ count contributed to the prediction of survival (p = 0.12 and 0.06, respectively). Large studies of combination or alternation therapy with several anti-HIV drugs should be given high priority.

[Survival of patients with zidovudine resistant HIV]

The survival of 35 patients with AIDS or advanced HIV infection on zidovudine treatment was related to the viral sensitivity to the drug and to the CD4+ cell count. Fourteen patients died, the survivors were followed up for an average of 804 days. In a univariate Cox model, survival was strongly related to log IC90 (p = 0.0003) and to the CD4+ count (p = 0.0002). In a bivariate model, log IC90 and the CD4+ count contributed to the prediction of survival (p = 0.12 and 0.06, respectively). Large studies of combination or alternation therapy with several anti-HIV-drugs should be given high priority.

[Pneumococcal bacteremia in Hvidovre Hospital 1986-1990]

The study describes 156 consecutive cases of pneumococcal bacteraemia among patients admitted to Hvidovre Hospital during the five-year period 1986-1990. Pneumococcal bacteraemia was most common in the age groups 0-4 and 50-99 years. The most common focus of infection was the lungs (84%). 81% had preexisting diseases and the most common were: Immunosuppression due to drugs, alcoholism, cardiovascular disease, chronic obstructive lung disease, diabetes and myelomatosis. Patients over 65 years of age had a higher case fatality (35%) than younger (12%). The overall case fatality rate was 24%. Twenty-three percent of cases were hospital-acquired, and associated with a case fatality of 37%. Pneumococcal bacteraemia was most common during the winter season and unrelated to influenza. Eighty-four percent of the examined isolates represented capsular types included in the 23-valent pneumococcal vaccine. Three percent of the tested strains were relatively resistant to penicillin (MIC > 0.1 microgram/ml). Despite antibiotic treatment, the mortality from pneumococcal bacteraemia, particularly in elderly, remains high. With this in mind, one may consider offering pneumococcal vaccination to persons over 65 years of age with chronic predisposing diseases.

Synthesis and anti-HIV activity of 5-alkoxymethyl-3'-azido-2',3- dideoxyuridines

Methyl 3-azido-5-O-tert-butyldiphenylsilyl-2,3-dideoxy-D-erythro-furanosi de (3) was coupled with silylated 5-hydroxymethyluracil (1a) and its C1-C6 alkyl ethers 1b-g to give the corresponding protected nucleosides 4a-g which were deprotected with Bu4NF to afford 3-azido nucleosides 5a-g and 6a-g. The alpha-anomers 6f,g show moderate activity against HIV. No significant activity against HSV-1 was found for the compounds 5 and 6.

Hepatitis C virus antibodies in homosexual men and intravenous drug users in Denmark

In order to evaluate the role of sexual transmission and parenteral transmission of hepatitis C virus (HCV) in homosexual men and intravenous drug users (IVDU) serum samples from 147 homosexual men and 126 IVDU were tested for anti-HCV. Anti-HCV was found in two (1.4%) of the homosexual men and in 123 (98%) of IVDU. The presence of anti-HCV could not be correlated to the presence of HBV markers or HIV-antibodies. HCV is widespread among Danish IVDU. Risk of sexual transmission seems low even though sexual contact is a much more prevalent risk factor than needle sharing.

Development of resistance to zidovudine in HIV strains isolated from CD4+ lymphocytes and plasma during therapy

An assay based on production of HIV antigen in cultures of CD4+ lymphocytes infected 'in vitro' with cell-free virus was established. Using this assay it was possible to isolate, propagate and reliably determine the zidovudine susceptibility of HIV isolates from all patients despite differences in cellular tropism and syncytium inducing capacity. Using this assay, differences in zidovudine susceptibility of 52 serial isolates obtained from 16 patients before and after initiation of therapy were examined. HIV with a 10- to 100-fold reduced susceptibility to zidovudine were isolated from 13 patients as early as 4 months after initiation of therapy. Number of months of zidovudine treatment was strongly associated with development of viral resistance, and high CD4 cell counts tended to be associated with lower rates of development of resistance. That patients can harbor mixtures of virus strains with different susceptibility to zidovudine was confirmed by the differences in susceptibility between isolates obtained simultaneously from CD4+ lymphocyte and plasma, and by the differences in susceptibility between virus strains isolated from clones of CD4+ lymphocytes.

HIV-2 infection in Denmark

A collection of 3019 selected serum samples (ss), comprising 329 ss from intravenous drug abusers, 558 ss from homosexual men, 682 samples from persons attending a STD clinic, 100 ss from individuals of African origin, 300 ss from sexual contacts to Africans, 650 ss from Danish blood donors who resided in Africa greater than 2 years prior to donating the ss, and 400 ss with equivocal antibody reactions in an HIV-1 Western blot was tested for antibodies against HIV-2 by in-house HIV-2 ELISA and Western blot. Four ss were positive for antibodies against HIV-2. Three of the ss originated from West African men, the fourth belonged to the spouse of one of these men. Three of the samples presented with an uncharacteristic reaction in a HIV-1 Western blot. The study indicates that HIV-2 infection is not yet widespread in Denmark and that it remains closely related to West Africa.

Neutralizing antibodies against two HIV-1 strains in consecutively collected serum samples: cross neutralization and association to HIV-1 related disease

97 sera collected during a 10-year period from 10 HIV-1 infected individuals were tested for neutralizing capacity against a virus isolate FICPH-22 obtained from a Danish AIDS patient, and the laboratory strain HTLV-IIIB. Three patterns of serum neutralizing activity were demonstrated: (a) patients developing high neutralizing activity against both HIV strains; (b) patients developing high neutralizing activity against the Danish virus isolate; and (c) patients developing only low titers of neutralizing antibodies (NA) against both HIV strains. The HTLV-IIIB strain was less sensitive to serum neutralization than the FICPH-22 isolate and the appearance of NA against HTLV-IIIB was typically lacking several years behind that against FICPH-22 indicating a broadening of the NA response over time. No difference in clinical outcome was observed comparing patients reaching high titers of NA and patients with low titers. Development of AIDS among patients reaching high titers of NA was preceded by a decline in NA titers, indicating an association of high titers of NA with the healthy carrier state and of declining or low titers of NA with disease progression. The majority of the neutralizing activity was mediated by IgG, but some neutralizing activity was demonstrated in the IgG depleted serum, indicating the presence of additional neutralizing substances in serum.

Synthesis of 5-alkoxymethyl derivatives of 3'-amino-2',3'-dideoxyuridine and evaluation of their activity against HIV and cancer

5-Alkoxymethyluracils 2a-c have been prepared by acid-catalyzed etherification of 5-hydroxymethyluracil (1). Compounds 1, 2a-c, 5-methoxymethyl- and 5-benzyloxymethyl-uracil were silylated and coupled with 1,5-di-O-acetyl-3-phthalimido-2,3-dideoxy-beta- D-erythro-pentofuranose (3), in the presence of trimethylsilyl triflate as a catalyst, to give the corresponding 3'-phthalimido-2',3'-dideoxynucleosides 5a-f and 6 which on treatment with 33% methylamine-ethanol afforded the corresponding 3'-amino-2',3'-dideoxynucleosides 7a-f and 8 in high yields. Compound 7d showed colony inhibition when tested against human epidermoid cervical cancer cells. Nucleosides 5a-e, 7a-f and 8 did not show any significant activity against HIV-1.

Free-radical synthesis of 3-(2-cyanoethyl)- and 3-(2-methoxycarbonylethyl)-2,3-dideoxy-alpha-D-erythro-pentofu ranoside and their application in the synthesis of potential antiviral nucleosides

Free-radical reaction of different carbohydrate educts 2, 5, and 7 with acrylonitrile in the presence of tributyltin hydride and a radical initiator (AIBN) gave the methyl 3-(2-cyanoethyl)-2,3-dideoxypentofuranosides 3a and 6. Similar reaction of 2 with methyl acrylate gave 3-(2-methoxycarbonylethyl)-2,3-dideoxypentofuranose 3b. Nucleoside coupling of 3a with silylated uracil gave an anomeric mixture of beta- and alpha-nucleoside 8 and 9 which were deprotected to give 10 and 11, respectively. Similar reaction of 3b with silylated N4-isobutyrylcytosine gave 12 and 13 which were deprotected to give the final nucleosides 16 and 17, respectively. None of the compounds 10a, 11, 14-17 showed significant activity against HIV.

Isolation of HIV from cultures of purified CD4+ lymphocytes

Isolation of HIV from cultures of CD4+ lymphocytes purified from peripheral blood by indirect panning was optimized and evaluated. Infectious HIV was isolated by single isolation attempts in 98% of 102 HIV-antibody-positive patients (55 had AIDS or ARC and 47 were clinically healthy). The average culture time required for positive cultures was largely independent of the CD4 count of the patients and 87% of the positive isolation cultures from both groups of patients became positive within 14 days of culture. An evaluation of the possible influence of media additives on propagation of HIV showed that: amphotericin-B had a suppressive effect on HIV replication at concentrations recommended for anti-fungal activity; recombinant and human interleukin-2 were equally suitable for both isolation cultures and for propagation of HIV, and polybrene, at a concentration of 2 micrograms/ml in the culture medium had a beneficial effect.

New synthesis of 2',3'-didehydro-2',3'-dideoxynucleosides

The 3'-iodonucleoside 4 and the 3'-O-methylsulfonylthymidine 9 have been synthesized by condensation of silylated uracils 2 with methyl 5-O-tert-butyldiphensilyl-2,3-dideoxy-3-iodo-D-threo-pentofuran oside (3) and methyl 5-O-tert-butyldiphenylsilyl-2-deoxy-3-methylsulfonyl-D-erythro- pentofuranoside (8), respectively. The nucleoside 4 and 9 produced the corresponding 2',3'-didehydro-2',3'-dideoxynucleosides 5 in an elimination reaction on treatment with sodium methoxide. The compounds 5b showed no antiviral activity against HIV-1.

Synthesis and evaluation of antiviral activity of L-acosamine and L-ristosamine nucleosides of furanose configuration

Mercuric-catalyzed hydrolysis of acetylated L-rhamnal 1 gives an alpha,beta-unsaturated aldehyde 2. 1,4-Addition of DBU-phthalimide salt with concomitant acetyl shift resulted in L-ribo and L-arabino isomers of 5-O-acetyl-2,3,6-trideoxy-3-phthalimido-hexofuranose 3 and 4. After acetylation at the anomeric center, coupling with silylated thymine resulted in three new nucleosides, with L-acosamine and L-ristosamine of furanose configuration as the carbohydrate moiety. The target compounds have been evaluated for their antiviral activity against HIV and HSV-1.

HIV antigen-induced release of histamine from basophils from HIV infected patients. Mechanism and relation to disease progression and immunodeficiency

Basophil leukocytes from 39 HIV-infected patients with various degrees of immunodeficiency and disease progression were stimulated with an HIV antigen preparation. Cells from 19 of 22 patients with AIDS and all of six patients with milder degrees of HIV-related disease showed significant histamine release. In contrast, cells from 11 asymptomatic HIV-infected patients and 11 healthy control persons released no histamine. The histamine release induced by HIV antigen was found to be inversely correlated to the number of CD4 positive T lymphocytes. These results indicate that the histamine release was related to both the clinical stage of disease and the degree of immunodeficiency. Passive sensitization experiments showed that IgE, but not IgG, was responsible for the induction of histamine release, indicating the reaction to be type 1 allergic. The histamine release caused by HIV might be involved in the development of disease because of the immunomodulating properties of this mediator.

Detection of human immunodeficiency virus DNA in cultured human glial cells by means of the polymerase chain reaction

This report describes the use of the polymerase chain reaction (PCR) for the detection of viral genomic sequences in latently infected cells. Infection with human immunodeficiency virus in cultures of human glial cells was demonstrated, using nucleic acid amplification followed by dot blot hybridization. It was not possible to detect any viral antigen production in the cultures, and attempts to recover virus by highly sensitive coculture techniques were unsuccessful, indicating that the infection was latent. The PCR technique provides a simple approach to the study of viral infection in cases where viral replication is absent, or where genomic copies are present at such low numbers that they are otherwise undetectable.

Synthesis of 3'-amino-2',3'-dideoxy-hexofuranose nucleosides with potential anti-viral activity

Michael type addition of DBU (1,8-diazabicyclo[5,4,0]undec-7-ene) phthalimide salt to 4,6-di-O-acetyl-2,3-dideoxy-aldehydo-D-erythro-trans-hex-2-enos e 2 and concomitant acetyl shift give an anomeric mixture of arabino and ribo isomers of 5,6-di-O-acetyl-2,3-dideoxy-3-phthalimido-D-hexofuranose 3 which after acetylation at the anomeric hydroxy group is separated to give 4 and 5. Subsequent reaction with 5'-substituted silylated uracil in the presence of TMS-triflate results in three different 5',6'-di-O-acetyl-2',3'-dideoxy-3'-phthalimido-D-hexofuranose nucleosides 7, 9, and 10 which were deprotected to give the corresponding 3'-amino nucleosides 8, 11, and 12. The compounds 7-12 were investigated for their activity against HSV-1 and HIV-1.

Synthesis of N-substituted 3'-amino-3'-deoxythymidines and their biological evaluation against HIV

Treatment of 3'-amino-3'-deoxythymidine (1) with carboxylic acid anhydrides afforded the corresponding acylamino derivatives 2a-f. Reaction of 1 with a variety of isothiocyanates led to the corresponding thioureido derivatives 3a-i. Also, conversion of 1 into 3'-carbylamino-3'-deoxythymidine (7) is reported. The compounds 2, 3, and 8 were evaluated for their anti-HIV activity in MT-4 cells, but did not show sufficient efficacy.

Synthesis of 3'-(4-nitroimidazol-1-yl)-2',3'-dideoxynucleosides of pyrimidine analogues and their biological evaluation against HIV

Reaction of 1,5-di-O-acetyl-2,3-dideoxy-3-phthalimido-beta-D-erythro-pento-fur anose (1) with silylated pyrimidinediones 2a-c using the Lewis acid trimethylsilyl triflate as catalyst afforded nucleosides 3a-c and 4a,c which were deprotected with 33% methylamine/ethanol to give the corresponding 3-aminonucleosides 5a-c and 6. These were reacted with 1,4-dinitroimidazoles 7a,b to give the 3-imidazolyldideoxynucleosides 8a,b and 9a-f. At sub-toxic concentrations these compounds were ineffective against HIV-1.

Derivatives of amphotericin inhibit infection with human immunodeficiency virus in vitro by different modes of action

Three water-soluble derivatives of amphotericin B were tested for inhibition of HIV infection in vitro. The compounds amphotericin B methyl ester (AME) and N-(N'-(2-(4'-methylmorpholinio)ethyl)N"-cyclohexyl guanyl) amphotericin B methyl ester (MCG) inhibited HIV infection by 50% at 1 microgram/ml; N-(N'-(3-dimethylaminopropyl)N"-ethyl guanyl) amphotericin B (DAPEG) did so at 5-11 micrograms/ml. While the virus-inhibitory effect of AME was due to an interaction with target lymphocytes, the effect of MCG was due to a direct anti-viral action. AME increased the potential of infected cells to fuse with uninfected cells, but MCG had no significant effect on cell fusion. All compounds had a lower cellular toxicity than amphotericin B and were not toxic at concentrations below 20 micrograms/ml.

Inhibition of human immunodeficiency virus (HIV) infection in vitro by anticarbohydrate monoclonal antibodies: peripheral glycosylation of HIV envelope glycoprotein gp120 may be a target for virus neutralization

Carbohydrate structures are often involved in the initial adhesion of pathogens to target cells. In the present study, a panel of anticarbohydrate monoclonal antibodies (MAbs) was tested for their ability to inhibit in vitro human immunodeficiency virus infectivity. MAbs against three different N- and O-linked carbohydrate epitopes (LeY, A1, and sialyl-Tn) were able to block infection by cell-free virus as well as inhibit syncytium formation. Inhibition of virus infectivity was independent of virus strain (HTLVIIIB or patient isolate SSI-002), the cell line used for virus propagation (H9 or MT4), and the cell type used as the infection target (MT4, PMC, or selected T4 lymphocytes). Inhibition was observed when viruses were preincubated with MAbs but not when cells were preincubated with MAbs before inoculation, and the MAbs were shown to precipitate 125I-labeled gp120. The MAbs therefore define carbohydrate structures expressed by the viral envelope glycoprotein gp120, indicating that glycans of the viral envelope are possible targets for immunotherapy or vaccine development or both.

Oral candidiasis and hairy leukoplakia correlate with HIV infection in Tanzania

We report a detailed study on oral lesions and their association with the WHO revised provisional case definition of AIDS as well as serologic signs of HIV infection among 186 patients in Dar Es Salaam, Tanzania. The patient material consisted of 39 hospitalized suspected AIDS patients, 44 medical nonsuspected patients, 53 dental outpatients, and 50 patients with sexually transmitted diseases. The male:female ratio was 2.1:1 on average. Oral examination was done without knowledge of the HIV status of the patients. Among 39 suspected AIDS patients 97% had WHO AIDS criteria and 90% were seropositive for HIV. Among the 147 patients not suspected of having AIDS 18 (12%) had AIDS criteria and 15% had serologic evidence of HIV infection. The presence of WHO AIDS criteria correlated significantly with the presence of HIV antibodies, but not with HIV antigen. Oral lesions were found in 54% of those with AIDS criteria and 52% of HIV-infected patients, as compared to 3% and 6% of the patients without AIDS criteria and HIV infection, respectively (p less than 0.01). Among patients with AIDS atrophic candidiasis occurred in 21%, pseudomembranous candidiasis in 23%, hairy leukoplakia in 36%, herpetic stomatitis in 2%, Kaposi's sarcoma in 4%, and nonspecific ulcer in 4%. The presence of oral lesions had a high predictive value for presence of AIDS criteria as well as for presence of HIV infection in this hospital setting. All patients should have a thorough oral examination and the presence of the aforementioned oral lesions should lead to testing for HIV infection.

Immunofluorescence assay for detection of antibodies to human immunodeficiency virus type 2

A total of 215 serum samples were tested for antibodies against human immunodeficiency virus type 2 (HIV-2) with an immunofluorescence assay (IFA). Some samples originated from Denmark and some originated from Guinea-Bissau. The IFA results were compared with enzyme-linked immunosorbent assay (ELISA) and Western (immuno-) blot (WB) results. Twenty-nine serum samples were found to be true positive for HIV-2 antibodies as judged from WB and radioimmunoprecipitation results; all of these were also found to be positive in the HIV-2 IFA. Of 80 serum samples originating from HIV-1-infected persons, 60% showed reactivity in the HIV-2 ELISA, and 51% cross-reacted with at least one band in the HIV-2 WB. None of the sera cross-reacted in the HIV-2 IFA. A total of five serum samples (three African and two Danish) gave unspecific results in the HIV-2 IFA. It is concluded that the HIV-2 IFA is more specific and at least as sensitive as a first-generation ELISA and that IFA is superior to WB in discriminating between HIV-1 and HIV-2 infections.

Isolation of HIV using T-lymphocyte 'panning': methodological aspects

A technique for isolation of HIV using selective cultures of T4 cells obtained from peripheral blood by immunochemical separation was developed and optimized. Using this method infectious virus could be isolated in single isolation attempts from 89% of 35 HIV-infected patients in different stages of immunodeficiency. This isolation frequency was virtually independent of the stage of the disease, in contrast to the results obtained by the conventional isolation technique based on peripheral mononuclear cells (PMC). It is concluded that isolation of HIV from selected T4 cells is superior to other methods when isolation is attempted from healthy HIV-infected individuals.

Explants of human oral epithelium exposed to viruses and cancer chemotherapeutics

Cultures of proliferating epithelial cells were established from explants of normal human oral epithelium from healthy young volunteers. The epithelial cells were found permissive for herpes simplex virus type 1 and type 2, coxsackie virus A-4 and A-16, adenovirus type 5, measles vaccine, rubella and influenza type A virus-. Medium from DEAE-pretreated epithelial cultures infected with two subtypes of human immunodeficiency virus-1 showed an increasing content of virusprotein with time by antigen ELISA testing. In contrast there was no evidence of infection with coxsackie virus type B-2, cytomegalovirus, Epstein-Barr virus and varicella zoster virus. Treatment of the epithelial cells with a non-cytotoxic dose of cancer chemotherapeutic prior to or after infection with coxsackie virus A-4 or herpes simplex virus type 1 influenced the virus production dependent on both compound, mode of application, and virus. Adriamycin (doxorubicin) in low dose was found to stimulate the production of the two viruses.

Antigen-antibody reaction in solution in capture competition immunoassay for human immunodeficiency virus antibodies

In the capture competition immunoassay, undiluted serum was reacted in solution with purified human immunodeficiency virus (HIV) antigen in wells of microtest plates coated with anti-HIV immunoglobulin G antibodies (HIV capture antibodies). HIV antibodies present in the serum being tested combined with the HIV antigen and thus blocked (completely or partially) the fixation of the antigen to the capture layer. Unblocked antigenic activity was measured in subsequent steps by the use of biotinylated anti-HIV immunoglobulin G and peroxidase-conjugated avidin. The assay was evaluated in comparison with indirect enzyme-linked immunosorbent assay and Western (immuno-) blot (WB). A total of 180 serum samples which reacted repeatedly as positive in indirect enzyme-linked immunosorbent assay but negative in WB were found to be negative by the capture competition assay. Of 54 serum samples showing dubious reactions (single p24 bands in WB), 53 were clearly separated into positive or negative reactions, whereas 1 serum sample gave a borderline reaction. It was concluded that a characteristic feature of this kind of inhibition assay is a very low frequency of equivocal results.