Umami taste perception and preferences of the domestic cat (Felis catus), an obligate carnivore

The domestic cat (Felis catus) is an obligate carnivore, and as such has a meat-based diet. Several studies on the taste perception of cats have been reported, indicating that their sense of taste has evolved based on their carnivorous diet. Here, we propose that umami (mediated by Tas1r1-Tas1r3) is the main appetitive taste modality for the domestic cat by characterizing the umami taste of a range of nucleotides, amino acids, and their mixtures for cats obtained using complementary methods. We show for the first time that cats express Tas1r1 in taste papillae. The cat umami receptor responds to a range of nucleotides as agonists, with the purine nucleotides having the highest activity. Their umami receptor does not respond to any amino acids alone; however, 11 l-amino acids with a range of chemical characteristics act as enhancers in combination with a nucleotide. l-Glutamic acid and l-Aspartic acid are not active as either agonists or enhancers of the cat umami receptor due to changes in key binding residues at positions 170 and 302. Overall, cats have an appetitive behavioral response for nucleotides, l-amino acids, and their mixtures. We postulate that the renowned palatability of tuna for cats may be due, at least in part, to its specific combination of high levels of inosine monophosphate and free l-Histidine that produces a strong synergistic umami taste enhancement. These results demonstrate the critical role that the umami receptor plays in enabling cats to detect key taste compounds present in meat.

Bitter taste sensitivity in domestic dogs (Canis familiaris) and its relevance to bitter deterrents of ingestion

As the most favoured animal companion of humans, dogs occupy a unique place in society. Understanding the senses of the dog can bring benefits to both the dogs themselves and their owners. In the case of bitter taste, research may provide useful information on sensitivity to, and acceptance of, diets containing bitter tasting materials. It may also help to protect dogs from the accidental ingestion of toxic substances, as in some instances bitter tasting additives are used as deterrents to ingestion. In this study we examined the receptive range of dog bitter taste receptors (Tas2rs). We found that orthologous dog and human receptors do not always share the same receptive ranges using in vitro assays. One bitter chemical often used as a deterrent, denatonium benzoate, is only moderately active against dTas2r4, and is almost completely inactive against other dog Tas2rs, including dTas2r10, a highly sensitive receptor in humans. We substituted amino acids to create chimeric dog-human versions of the Tas2r10 receptor and found the ECL2 region partly determined denatonium sensitivity. We further confirmed the reduced sensitivity of dogs to this compound in vivo. A concentration of 100μM (44.7ppm) denatonium benzoate was effective as a deterrent to dog ingestion in a two-bottle choice test indicating higher concentrations may increase efficacy for dogs. These data can inform the choice and concentration of bitter deterrents added to toxic substances to help reduce the occurrence of accidental dog poisonings.

A patient-initiated treatment model for blepharospasm and hemifacial spasm: a randomized controlled trial

Background

To test, in a two-arm, single center, superiority, randomized controlled trial, the effectiveness of and costs associated with a patient-initiated treatment model for people with hemifacial spasm (HFS) and blepharospasm (BEB) in comparison to usual care.

Methods

One hundred and thirty patients with HFS or BEB, aged 18 years or over, were recruited from a nurse-led botulinum toxin type A clinic at an eye hospital in the United Kingdom (UK), completed baseline measures and were randomized (1:1). The intervention group determined their own botulinum toxin type A (BoNT/A) treatment schedule during the trial period (9 months) and received an information leaflet with a “hotline” number to book an appointment. Usual care appointments were scheduled by treating clinicians. Data analysts were blind to study group. The primary outcomes were disease severity and functional disability, as measured by the Jankovic Rating Scale and Blepharospasm Disability Index, respectively. Secondary outcomes included quality of life, anxiety and depression, satisfaction with care, confidence in the service, economic costs and employment days lost.

Results

Sixty-five patients were randomized to each group. The intervention demonstrated no statistically significant difference to usual care for any of primary outcomes. On secondary outcomes the levels of anxiety differed significantly (F_{2, 142.39} = 1.65, p = 0.02), with the intervention arm exhibiting a decrease and the control arm an increase (Hedges’ g = − 0.26 [99% CI -0.83, 0.32]). No other statistically significant differences were found for secondary outcomes. Overall healthcare costs and costs to the patient were on average £198.95 less (95% CI -£256.76, £654.67; p = 0.10) per participant for those in the intervention compared to usual care, although this finding was not significant.

Conclusions

We did not observe differences between the patient-initiated treatment model and usual care for people with BEB or HFS, on any primary outcome measure, quality of life, or depression. The patient-initiated treatment model may, however, have the potential to save healthcare costs and reduce anxiety. Patients using this new model were also equally as satisfied in the service and confident in their care as those receiving treatment as usual.

Trial registration

Clinicaltrials.gov ID NCT02577224, 16th October 2015.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02603-7.

Pilot study of a nurse-led adult lacrimal clinic at a tertiary ophthalmic centre

This article provides the reader with an outline of the anatomy and physiology of the lacrimal system and illustrates how a variety of pathologies within this system can result in the development of a watery eye. It describes the role of the nurse consultant in the diagnosis and management of patients with watery eye in the lacrimal clinic, and how the training programme for the development of such skills was implemented. Following training, within the realms of an established pilot study, the nurse consultant began to implement her skills in a newly established nurse-led lacrimal clinic. Patients seen in the lacrimal clinic would previously have been assessed and managed by a doctor. To confirm the accuracy of this approach, an audit was undertaken comparing the nurse-led diagnosis and management plans with that of an oculoplastic doctor. In addition, patient waiting times in the clinic and patient satisfaction were assessed, as important indicators of quality of care.

Which factors impact on quality of life for adults with blepharospasm and hemifacial spasm?

Purpose: Benign essential blepharospasm (BEB) and hemifacial spasm (HFS) are debilitating conditions causing spasms to the eyes and/or face and can significantly impact on quality of life (QoL). Initial research has highlighted potential factors impacting on QoL in BEB, but there remains a wealth of demographic, clinical, and psychosocial factors that may contribute to QoL but have not received attention. Methods: Cross-sectional baseline data were collected before a single-masked randomised controlled trial from 130 adults with BEB and HFS recruited from botulinum toxin clinics at Moorfields Eye Hospital, London. QoL was measured using the 24-item Craniocervical Dystonia Questionnaire (CDQ24), which provides a total score and five subscale scores relating to Stigma, Emotional state, Pain, Activities of daily living (ADL), and Social/family life. Treating clinicians provided clinical data. Hierarchical multiple regressions were performed on this baseline data to identify significant predictors of QoL. Results: ADL and Stigma were the areas most impacted upon whilst patients experienced better adjustment in relation to Pain, Social/family life, and Emotional state. CDQ24 Total scores were explained by the model (80% variance) and were significantly associated with appearance concerns, emotional representations, perceived negative consequences of the condition, mood, and dose of botulinum toxin. Conclusions: Patients with BEB and HFS report a detrimental impact on ADL and perceived stigma in relation to their condition. Predominantly, individual perceptions and mood are associated with QoL in this population, rather than demographic and clinical factors, signifying areas to target in the design of future healthcare services or interventions.

Effectiveness and cost-effectiveness of a patient-initiated botulinum toxin treatment model for blepharospasm and hemifacial spasm compared to standard care: study protocol for a randomised controlled trial

Background

Blepharospasm and hemifacial spasm are debilitating conditions that significantly impact on patient quality of life. Cyclical treatment with botulinum toxin injections offers temporary relief, but the duration of treatment efficacy is variable. The standard model of patient care defines routine fixed-time based scheduled treatment cycles which may lead to unnecessarily frequent treatment for some patients and experience of distressing symptoms in others, if symptoms return before the scheduled follow-up period.

Methods/Design

A randomised controlled trial will compare a patient-initiated model of care, where patients determine botulinum toxin treatment timing, to the standard model of care in which care is scheduled by the clinical team. A sample of 266 patients with blepharospasm or hemifacial spasm will be recruited from Moorfields Eye Hospital (MEH), London. The trial will be accompanied by a mixed-methods evaluation of acceptability of the new service. Patients who meet eligibility criteria will be assessed at baseline and those in the intervention group will be provided with instructions on how to book their own treatment appointments. Patients in both groups will be followed up 3 and 9 months into the trial and all patients will be returned to usual care after 9 months to meet safety protocols. Primary outcome measures include disease severity (questionnaire), functional disability (questionnaire) and patient satisfaction with care (questionnaire). Secondary outcomes include disease-specific quality of life (questionnaire), mood (questionnaire), illness and treatment perceptions (questionnaire and semi-structured interviews), economic impact (questionnaire) and acceptability (questionnaire and semi-structured interviews).

Discussion

This trial will assess the effectiveness and cost-effectiveness of a patient-led care model for botulinum toxin therapy. If the new model is shown to be effective in reducing distress and disability in these populations and is found to be acceptable to patients, whilst being cost-effective, this will have significant implications for service organisation across the NHS.

Trial registration

UK Clinical Research Network (UKCRN) Portfolio 18660. Clinicaltrials.gov ID NCT102577224 (registered 29 October 2015)

The flavonoid baicalin exhibits anti-inflammatory activity by binding to chemokines

Baicalin (BA) is a flavonoid compound purified from the medicinal plant Scutellaria baicalensis Georgi and has been reported to possess anti-inflammatory and anti-viral activities. In order to elucidate the mechanism(s) of action of BA, we tested whether BA could interfere with chemokines or chemokine receptors, which are critical mediators of inflammation and infection. We observed that BA inhibited the binding of a number of chemokines to human leukocytes or cells transfected to express specific chemokine receptors. This was associated with a reduced capacity of the chemokines to induce cell migration. Co-injection of BA with CXC chemokine interleukin-8 (IL-8) into rat skin significantly inhibited IL-8 elicited neutrophil infiltration. BA did not directly compete with chemokines for binding to receptors, but rather acted through its selective binding to chemokine ligands. This conclusion was supported by the fact that BA cross-linked to oxime resin bound chemokines of the CXC (stromal cell-derived factor (SDF)-1alpha, IL-8), CC (macrophage inflammatory protein (MIP)-1beta, monocyte chemotactic protein (MCP)-2), and C (lymphotactin (Ltn)) subfamilies. BA did not interact with CX3C chemokine fractalkine/neurotactin or other cytokines, such as TNF-alpha and IFN-gamma, indicating that its action is selective. These results suggest that one possible anti-inflammatory mechanism of BA is to bind a variety of chemokines and limit their biological function.

HIV-specific immunity following immunization with HIV synthetic envelope peptides in asymptomatic HIV-infected patients

OBJECTIVE

A phase I trial was conducted to evaluate the safety and immunogenicity of an HIV synthetic peptide vaccine in HIV-seropositive individuals. The immunogens used in this study were PCLUS 3-18MN and PCLUS 6.1-18MN envelope peptides.

METHODS

Eight HIV-infected patients received six subcutaneous injections of 160 microg PCLUS 3-18MN in Montanide ISA 51 and were followed longitudinally for a year after the first immunization. Peripheral blood mononuclear cells (PBMC) were tested for peptide-specific T helper and cytotoxic T cell (CTL) responses, HIV-1MN neutralizing antibodies and antibodies against HIV PCLUS 3 and P18 MN peptides.

RESULTS

PCLUS 3-1 8MN-specific T helper responses were significantly increased at 36 weeks (P < 0.05, after adjustment for multiple comparisons) following initial immunization with PCLUS 3-18MN. A P18MN-specific CTL response, not present prior to vaccination, was observed after immunization in one patient. Serum HIV-1 MN-neutralizing antibody titers increased in each of the three patients who had low titers prior to immunization. Plasma HIV RNA levels and CD4 cell counts did not change appreciably during the study period.

CONCLUSIONS

This trial demonstrates that both peptides can be safely administered to HIV-infected individuals and that PCLUS 3-18MN induces increases in HIV peptide-specific immune responses.

Organisation of the human PAX4 gene and its exclusion as a candidate for the Wolcott-Rallison syndrome

Neonatal diabetes mellitus is a rare condition, the causes of which are mostly unknown. One well defined though very rare entity is the autosomal recessive Wolcott-Rallison syndrome, in which permanent neonatal diabetes, osteopenia, and epiphyseal dysplasia occur. Only five previous families have been reported, and here we describe the second in which parental consanguinity was present. The proband was born to first cousin parents and died at 2 years from the sequelae of poorly controlled diabetes. To test the hypothesis that mutation of PAX4, required in the mouse for pancreatic islet beta cell development, might cause WRS, the structure of the human PAX4 gene was deduced and DNA from two unrelated WRS patients sequenced. No PAX4 mutation was present, though the entire coding region was sequenced in both patients. It therefore appears unlikely that PAX4 is involved in the aetiology of Wolcott-Rallison syndrome, though it remains a good candidate for other forms of neonatal diabetes mellitus.

Organization of the human glucokinase regulator gene GCKR

Glucokinase plays an important role in regulating insulin secretion in response to changes in blood glucose levels. As a result, one form of maturity onset diabetes of the young (MODY) results from haploinsufficiency of glucokinase. In both liver and pancreatic islet, glucokinase is allosterically regulated by an inhibitory protein (glucokinase regulatory protein, GCKR). GCKR has therefore become an important gene for functional analysis in type 2 diabetes. To allow genetic assessment of any such role, we have determined the structure of the human GCKR gene. Characterization of P1 and YAC clones containing GCKR shows it to consist of 19 exons spanning 27 kb. RT-PCR, RACE, and RNase protection experiments defined a transcriptional start site for GCKR 66 bp upstream of the initiation codon, but provided no evidence for islet cell specific alternative splicing in the rat. By SSCP screening, a common polymorphic sequence variant has been defined within exon 15 of human GCKR, at nt 1400 of the cDNA. This alters amino acid residue 446 from proline, conserved in rat and Xenopus, to leucine.

Dose-limiting neurotoxicity in a phase I study of penclomedine (NSC 388720, CRC 88-04), a synthetic alpha-picoline derivative, administered intravenously

3,5-Dichloro-2,4-dimethoxy-6-(trichloromethyl)pyridine (penclomedine, NSC 338720, CRC 88-04) is an alpha-picoline derivative with anti-tumour activity in preclinical models. Penclomedine administration by 1-h intravenous infusion on 5 consecutive days was repeated 3 weekly in the absence of dose-limiting toxicity (DLT) or disease progression. Five dose levels were investigated (22.5-340 mg m(-2) day[-1]). Eight men and eight women were entered, median age 59 years (range 39-73 years), with good performance status (ECOG 0/1) in 11 patients. A total of 13 out of 16 patients had received previous chemotherapy. Common toxicity criteria grade (CTCg) II vomiting was recorded at all dose levels. Neurotoxicity (cerebellar ataxia and dizziness) was the DLT, CTCg III toxicity occurring in three out of three patients treated at 340 mg m(-2) day(-1). CTCg III dizziness was noted in one out of three patients at 250 mg m(-2) day(-1). Neurotoxicity developed during the 1-h infusion and persisted for a variable period (maximum 5 h) after infusion. Prophylactic antiemetic drugs appeared to reduce associated vomiting but did not prevent ataxia. No antiproliferative toxicities were noted and no anti-tumour responses were documented. Penclomedine pharmacokinetic studies confirmed preclinical evidence of extensive apparent distribution (93 l m[-2]) and rapid clearance (41 l h[-1] m[-2]). Purkinje cell loss has been identified in preclinical models after intraperitoneal administration (O'Reilly et al, 1996a) and further clinical development of penclomedine will focus on oral administration.

Cytokine-in-adjuvant steering of the immune response phenotype to HIV-1 vaccine constructs: granulocyte-macrophage colony-stimulating factor and TNF-alpha synergize with IL-12 to enhance induction of cytotoxic T lymphocytes

To enhance and steer immune responses to synthetic peptide vaccines toward selected functional types and to understand the cooperative action of cytokines in fine-tuning the immune response, we attempted to influence the in vivo cytokine environment by delivering cytokines directly to the microenvironment in which the immune response is initiated. Here we study the effects of IL-2, IL-4, IL-7, IL-1beta, IL-12, IFN-gamma, TNF-alpha, and granulocyte-macrophage CSF (GM-CSF) incorporated with peptide in adjuvant on a variety of responses elicited: CTL, T cell proliferation, cytokine production and message, and Ab isotype. We show GM-CSF to be the single most effective cytokine for enhancing both cellular and humoral immunity to two previously characterized HIV-1 MN vaccine constructs. Novel synergies were also detected. GM-CSF synergized with IL-12 for CTL induction in BALB/c mice concomitant with suppression of Th2 cytokines IL-4 and IL-10. TNF-alpha also synergized with IL-12, but by a different mechanism, inducing IFN-gamma production in BALB/c mice and thus shifting the response to a Th1 phenotype. The results presented here suggest that in addition to IL-2, optimum induction of CD8+ CTL in vivo requires a combination of cytokines, including GM-CSF (probably acting to enhance Ag presentation and CD4+ cell help) and IL-12 (steering the Th response toward Th1 cytokines).

Cytokine-in-adjuvant steering of the immune response phenotype to HIV-1 vaccine constructs: granulocyte-macrophage colony-stimulating factor and TNF-alpha synergize with IL-12 to enhance induction of cytotoxic T lymphocytes

To enhance and steer immune responses to synthetic peptide vaccines toward selected functional types and to understand the cooperative action of cytokines in fine-tuning the immune response, we attempted to influence the in vivo cytokine environment by delivering cytokines directly to the microenvironment in which the immune response is initiated. Here we study the effects of IL-2, IL-4, IL-7, IL-1beta, IL-12, IFN-gamma, TNF-alpha, and granulocyte-macrophage CSF (GM-CSF) incorporated with peptide in adjuvant on a variety of responses elicited: CTL, T cell proliferation, cytokine production and message, and Ab isotype. We show GM-CSF to be the single most effective cytokine for enhancing both cellular and humoral immunity to two previously characterized HIV-1 MN vaccine constructs. Novel synergies were also detected. GM-CSF synergized with IL-12 for CTL induction in BALB/c mice concomitant with suppression of Th2 cytokines IL-4 and IL-10. TNF-alpha also synergized with IL-12, but by a different mechanism, inducing IFN-gamma production in BALB/c mice and thus shifting the response to a Th1 phenotype. The results presented here suggest that in addition to IL-2, optimum induction of CD8+ CTL in vivo requires a combination of cytokines, including GM-CSF (probably acting to enhance Ag presentation and CD4+ cell help) and IL-12 (steering the Th response toward Th1 cytokines).

Characterization of the microsomal epoxide hydrolase of hepatic microsomes of the common dab,Limanda limanda

Epoxide hydrolase of microsomal membranes of the common dab (Limanda limanda) has been characterized using p-nitrostyrene oxide as substrate. Under the conditions of assay used, the turnover number with this substrate was higher than found for the more frequently used styrene oxide and steady state kinetics were observed. The enzyme had a KM of 0.12 mM and optima for pH and temperature between pH 8-10.2 and 50-60°C respectively. Enzyme activity was unaffected by low concentrations of ionic and non-ionic detergents but was inhibited by higher concentrations of Lubrol and Brij. The enzyme protein did not react with monospecific antibodies to rat or human microsomal epoxide hydrolase during Western blotting. Large inter-individual variation in enzyme activity was found but the enzyme does not appear to be expressed in a gender-specific way. Fish were administered a wide range of hydrocarbons which are known to alter the expression of cytochrome P450 1A but these had no effect other than benzothiophene which caused a small increase in enzyme activity.

Candidate HIV type 1 multideterminant cluster peptide-P18MN vaccine constructs elicit type 1 helper T cells, cytotoxic T cells, and neutralizing antibody, all using the same adjuvant immunization

Cytotoxic T lymphocytes and Th1 cells have been suggested to play a critical role in the control of HIV infection. It is therefore considered that a vaccine that induces a strong Th1 response and CTL response would be more efficacious than one that does not in providing protection against infection and progression toward AIDS. In this study we show that immunization with vaccine constructs consisting of multideterminant cluster peptides containing Th epitopes from the HIV-1IIIB envelope colinearly synthesized to peptide 18MN, is capable of inducing a Th1 response in mice and, dependent on this help, both cytotoxic T cell responses and neutralizing antibody toward the homologous strain of HIV. Moreover, the cytotoxic T cell response elicited by immunization with a mixture of cluster peptide-P18MN vaccine constructs was at least as cross-reactive against known viral variant P18 target sequences as a CTL line produced by immunization with a vaccinia construct expressing recombinant gp160 MN. Four adjuvants were compared to optimize both CTL and antibody responses. A single adjuvant formulation of peptide in ISA 51 could elicit all three: Th1 cells, CTLs, and neutralizing antibody. Thus, immunization directed toward the development of a cytotoxic T cell response does not preclude the development of neutralizing antibody and vice versa, i.e., the responses are not mutually exclusive. The immunization protocol described here should be directly applicable for study in clinical trials aimed at HIV-1 immunotherapy or prophylaxis.

Efficient neutralization of primary isolates of HIV-1 by a recombinant human monoclonal antibody

The ability of antibodies to neutralize diverse primary isolates of human immunodeficiency virus-type 1 in vitro has been questioned, with implications for the likely efficacy of vaccines. A recombinant human antibody to envelope glycoprotein gp120 was generated and used to show that primary isolates are not refractory to antibody neutralization. The recombinant antibody neutralized more than 75 percent of the primary isolates tested at concentrations that could be achieved by passive immunization, for example, to interrupt maternal-fetal transmission of virus. The broad specificity and efficacy of the antibody implies the conservation of a structural feature on gp120, which could be important in vaccine design.

In vitro evolution of a neutralizing human antibody to human immunodeficiency virus type 1 to enhance affinity and broaden strain cross-reactivity

A method is described that allows for the improvement of antibody affinity. This method, termed complementary-determining region (CDR) walking, does not require structural information on either antibody or antigen. Complementary-determining regions are targeted for random mutagenesis followed by selection for fitness, in this case increased binding affinity, by the phage-display approach. The current study targets a human CD4-binding-site anti-gp120 antibody that is potently and broadly neutralizing. Evolution of affinity of this antibody demonstrates in this case that affinity can be increased while reactivity to variants of human immunodeficiency virus type 1 is broadened. The neutralizing ability of this antibody is improved, as assayed with laboratory and primary clinical isolates of human immunodeficiency virus type 1. The ability to produce human antibodies of exceptional affinity and broad neutralizing ability has implications for the therapeutic and prophylactic application of antibodies for human immunodeficiency virus type 1 infection.

Construction of an HIV-1 peptide vaccine containing a multideterminant helper peptide linked to a V3 loop peptide 18 inducing strong neutralizing antibody responses in mice of multiple MHC haplotypes after two immunizations

Peptide constructs comprised of multideterminant Th peptides from the envelope glycoprotein of HIV previously identified to induce proliferative responses in four different haplotypes of mice and IL-2 responses in 52 to 73% of HIV positive, Ag-responsive patients, were colinearly synthesized with the peptide 18 of the V3 loop of HIV-1 gp 160, corresponding to the principal neutralizing determinant of HIV-IIIB. The segments containing clusters of overlapping Th epitopes were called cluster peptides. Cognate help for peptide 18 antibody was elicited after a single immunization in all strains of mice that had previously responded to a T cell epitope encompassed by the cluster peptides. Animals boosted with cluster peptide-peptide 18 constructs 36 to 52 wk later displayed secondary antibody responses. Cluster peptide 3-peptide 18 induced antibody that neutralized homologous virus in one strain of mice although strong peptide 18 antibody responses were detected in all four strains of mice. The most promising construct, cluster peptide 6-peptide 18, induced neutralizing antibody in all strains of mice tested, and in two strains the level of neutralizing antibody achieved was comparable to levels adequate for protection from homologous viral challenge in chimpanzees. After a single boost, antibody titers for 90% neutralization in the range of 1/1000 to 1/16,000 were achieved. These neutralizing titers against the homologous viral strain, after just two immunizations, are at least four- to eightfold higher than the highest titered other polyclonal V3-specific immune sera we have ever observed in our laboratories. We also asked why some sera neutralized and others with similar ELISA titers did not. No correlation was found between neutralization and isotype or affinity for peptide or gp 120. We could not account for neutralization by antibodies to the helper sites. Substitutions made in the central loop region of peptide 18, amino acid residues PGRAF, dramatically reduced binding of both neutralizing and non-neutralizing sera although some fine specificity differences between neutralizing and nonneutralizing sera were noted. These results have implications for the design of synthetic peptide vaccines for HIV.

Construction of an HIV-1 peptide vaccine containing a multideterminant helper peptide linked to a V3 loop peptide 18 inducing strong neutralizing antibody responses in mice of multiple MHC haplotypes after two immunizations

Peptide constructs comprised of multideterminant Th peptides from the envelope glycoprotein of HIV previously identified to induce proliferative responses in four different haplotypes of mice and IL-2 responses in 52 to 73% of HIV positive, Ag-responsive patients, were colinearly synthesized with the peptide 18 of the V3 loop of HIV-1 gp 160, corresponding to the principal neutralizing determinant of HIV-IIIB. The segments containing clusters of overlapping Th epitopes were called cluster peptides. Cognate help for peptide 18 antibody was elicited after a single immunization in all strains of mice that had previously responded to a T cell epitope encompassed by the cluster peptides. Animals boosted with cluster peptide-peptide 18 constructs 36 to 52 wk later displayed secondary antibody responses. Cluster peptide 3-peptide 18 induced antibody that neutralized homologous virus in one strain of mice although strong peptide 18 antibody responses were detected in all four strains of mice. The most promising construct, cluster peptide 6-peptide 18, induced neutralizing antibody in all strains of mice tested, and in two strains the level of neutralizing antibody achieved was comparable to levels adequate for protection from homologous viral challenge in chimpanzees. After a single boost, antibody titers for 90% neutralization in the range of 1/1000 to 1/16,000 were achieved. These neutralizing titers against the homologous viral strain, after just two immunizations, are at least four- to eightfold higher than the highest titered other polyclonal V3-specific immune sera we have ever observed in our laboratories. We also asked why some sera neutralized and others with similar ELISA titers did not. No correlation was found between neutralization and isotype or affinity for peptide or gp 120. We could not account for neutralization by antibodies to the helper sites. Substitutions made in the central loop region of peptide 18, amino acid residues PGRAF, dramatically reduced binding of both neutralizing and non-neutralizing sera although some fine specificity differences between neutralizing and nonneutralizing sera were noted. These results have implications for the design of synthetic peptide vaccines for HIV.

HIV experimental vaccines based on the iscom technology using envelope and GAG gene products

In previous experiments gp160 incorporated into iscom was shown to induce neutralizing antibodies to the homologous as well as the heterologous isolates of HIV-1 (Akerblom et al., AIDS Res., 1991). In the present work we have incorporated into iscoms three defined recombinant DNA products of HIV-1. The carboxy-terminal part of gp120 expressed in E. Coli-PB-1; a chimera containing parts of both p24 and p15 expressed in E. coli-GAG; and baculovirus gp160 cloned in baculovirus and produced in insect cells. Immune responses were induced by the iscom preparations to the homologous antigen as well as to defined recombinant products and to the synthetic peptide RP135 (aa 304-328) harboring a neutralizing epitope. Sera from mice immunized with PB1-iscoms and gp160 (baculo) iscoms were tested in a syncytie inhibition assay. The serum from a mouse immunized with PB1 iscoms reacted strongly with the synthetic peptide RP135 and also neutralized the homologous isolate HIV-1/IIIB with a neutralization titer of 1/64. Three gp160 (baculo) iscom antisera were tested, of which two reacted strongly with the synthetic peptide RP135 but did not neutralize the homologous isolate HIV-1/IIIB. High serum titers were induced in mice by the gp160 iscoms (2 micrograms) to homologous antigen and the recombinant DNA E. coli construct p121 covering part of gp41. The ceilings of the antibody responses were reached after two immunizations. The PB1- and GAG-iscoms required three immunizations to reach the ceiling of the antibody response.

Recombinant human Fab fragments neutralize human type 1 immunodeficiency virus in vitro

A panel of 20 recombinant Fab fragments reactive with the surface glycoprotein gp120 of human type 1 immunodeficiency virus (HIV-1) were examined for their ability to neutralize MN and IIIB strains of the virus. Neutralization was determined as the ability of the Fab fragments to inhibit infection as measured in both a p24 ELISA and a syncytium-formation assay. One group of closely sequence-related Fab fragments was found to neutralize virus in both assays with a 50% neutralization titer at approximately 1 micrograms/ml. Another Fab neutralized in the p24 ELISA but not in the syncytium assay. The other Fab fragments showed weak or no neutralizing ability. The results imply that virion aggregation or crosslinking of gp120 molecules on the virion surface is not an absolute requirement for HIV-1 neutralization. Further, all of the Fab fragments were shown to be competitive with soluble CD4 for binding to gp120 and yet few neutralized the virus effectively, implying that the mechanism of neutralization in this case may not involve receptor blocking. The observation of a preponderance of high-affinity Fab fragments with poor or no neutralizing ability could have implications for vaccine strategies.

Native but not denatured recombinant human immunodeficiency virus type 1 gp120 generates broad-spectrum neutralizing antibodies in baboons

The protection of individuals from human immunodeficiency virus type 1 (HIV-1) infection with an envelope subunit derived from a single isolate will require the presentation of conserved epitopes in gp120. The objective of the studies presented here was to test whether a native recombinant gp120 (rgp120) immunogen would elicit responses to conserved neutralization epitopes that are not present in a denatured recombinant gp120 antigen from the same virus isolate. In a large study of 51 baboons, we have generated heterologous neutralizing activity with native, glycosylated rgp120SF2 but not with denatured, nonglycosylated env 2-3SF2. After repeated exposure to rgp120SF2 formulated with one of several adjuvants, virus isolates from the United States, the Caribbean, and Africa were neutralized. The timing of the immunization regimen and the choice of adjuvant affected the virus neutralization titers both quantitatively and qualitatively. These results suggest that vaccination with native, glycosylated rgp120 from a single virus isolate, HIV-SF2, may elicit a protective immune response effective against geographically and sequentially distinct HIV-1 isolates.

Cross-neutralizing antibodies to HIV-1 in mice after immunization with gp160 iscoms. Dissection of the immune response

Gp160 expressed in vaccinia and produced in vero cells was integrated into iscoms. Gp160 iscoms elicited a high serum antibody response in mice, and after two immunizations a ceiling was reached. The serum antibody response was dissected by the use of defined recombinant DNA products, representing different regions of the gp160 molecule. High antibody titers to the peptid RP135 (a.a. 296-332) correlated with induction of neutralizing serum antibodies. In some animals, gp160 (IIIB) iscoms elicited cross-neutralizing antibodies that also neutralized the distantly related RF isolate.

Emergence of viruses resistant to neutralization by V3-specific antibodies in experimental human immunodeficiency virus type 1 IIIB infection of chimpanzees

Emergence in two chimpanzees of human immunodeficiency virus type 1 (HIV-1) IIIB variants resistant to neutralization by the preexisting antibody is described. Viruses isolated from the HIV-1 IIIB gp120-vaccinated and -challenged animal were more resistant to neutralization by the chimpanzee's own serum than viruses isolated from the naive infected animal, indicating immune pressure as the selective mechanism. However, all reisolated viruses were 16- to 256-fold more neutralization resistant than the inoculum virus to antibodies binding to the third variable domain (V3) of the HIV-1 external envelope. Early chimpanzee serum samples that neutralized the inoculum strain but not the reisolated viruses were found to bind an HIV-1 IIIB common nonapeptide (IQRGPGRAF) derived from the gp120 isolate-specific V3 domain shown to induce isolate-specific neutralization in other animals. Amplification of the V3 coding sequence by polymerase chain reaction and subsequent sequence analysis of the neutralization-resistant variants obtained from in vivo-infected animals indicated that early resistance to neutralization by an HIV-1 IIIB monoclonal antibody (0.5 beta) was conferred by changes outside the direct binding site for the selective neutralizing antibody. The reisolated neutralization-resistant isolates consisted of the lower-replication-competent virus subpopulations of the HIV-1 IIIB stock, as confirmed by biological and sequence analyses. In vitro passage of the HIV-1 IIIB stock through chimpanzee and human peripheral blood mononuclear cell cultures void of HIV-specific antibody resulted in homogenic amplification of the more-replication-competent subpopulation preexisting in the original viral stock, suggesting a role for the immune system in suppressing the more-replication-competent viruses.