Masculinization of the distal tubular and external genitalia in female sheep with prenatal androgen exposure

Prenatal exposure to endogenous or exogenous androgens alters the development of the female reproductive tract. Although lesions in ovaries and external genitalia of androgenized female sheep have been reported, lesions of the tubular genitalia have not. Testosterone propionate (TP) or dihydrotestosterone (DHT) was administered by intramuscular injection twice weekly to 32 ewes from 30 to 90 days of pregnancy. The ewes lambed normally. The reproductive tracts from 24 treated and 13 control postpubertal female offspring were examined at 10 months of age. The ovaries, oviducts, and uteri were grossly and histologically normal in both TP- and DHT-exposed sheep. However, in the DHT-treated sheep, the uterus connected to a misshapen, saccular vagina that opened into the urethra; in the TP-treated sheep, it ended in a blind sac. In both TP- and DHT-treated sheep, the urethra was approximately 5 times longer than that of control sheep, and it resembled a male urethra with bilateral male accessory genital glands. The urethra terminated in a fully developed penis in both TP- and DHT-treated sheep, and a scrotal sac was present (without testes). These results show that prenatal exposure of female sheep to exogenous androgens results in masculinization of the tubular and external genitalia.

epitopes immediately below the base of the V3 loop of gp120 as targets for the initial autologous neutralizing antibody response in two HIV-1 subtype B-infected individuals

Epitopes that drive the initial autologous neutralizing antibody response in HIV-1-infected individuals could provide insights for vaccine design. Although highly strain specific, these epitopes are immunogenic, vulnerable to antibody attack on infectious virus, and could be involved in the ontogeny of broadly neutralizing antibody responses. To delineate such epitopes, we used site-directed mutagenesis, autologous plasma samples, and autologous monoclonal antibodies to map the amino acid changes that led to escape from the initial autologous neutralizing antibody response in two HIV-1 subtype B-infected individuals. Additional mapping of the epitopes was accomplished by using alanine scanning mutagenesis. Escape in the two individuals occurred by different pathways, but the responses in both cases appeared to be directed against the same region of gp120. In total, three amino acid positions were identified that were independently associated with autologous neutralization. Positions 295 and 332 are located immediately before and after the N- and C-terminal cysteines of the V3 loop, respectively, the latter of which affected an N-linked glycan that was critical to the neutralization epitope. Position 415 affected an N-linked glycan at position 413 in the C terminus of V4 that might mask epitopes near the base of V3. All three sites lie in close proximity on a four-stranded antiparallel sheet on the outer domain of gp120. We conclude that a region just below the base of the V3 loop, near the coreceptor binding domain of gp120, can be a target for autologous neutralization.

Lassa hemorrhagic fever in a late term pregnancy from northern Sierra Leone with a positive maternal outcome: case report

Lassa fever (LF) is a devastating viral disease prevalent in West Africa. Efforts to take on this public health crisis have been hindered by lack of infrastructure and rapid field deployable diagnosis in areas where the disease is prevalent. Recent capacity building at the Kenema Government Hospital Lassa Fever Ward (KGH LFW) in Sierra Leone has lead to a major turning point in the diagnosis, treatment and study of LF. Herein we present the first comprehensive rapid diagnosis and real time characterization of an acute hemorrhagic LF case at KGH LFW. This case report focuses on a third trimester pregnant Sierra Leonean woman from the historically non-endemic Northern district of Tonkolili who survived the illness despite fetal demise. Employed in this study were newly developed recombinant LASV Antigen Rapid Test cassettes and dipstick lateral flow immunoassays (LFI) that enabled the diagnosis of LF within twenty minutes of sample collection. Deregulation of overall homeostasis, significant hepatic and renal system involvement, and immunity profiles were extensively characterized during the course of hospitalization. Rapid diagnosis, prompt treatment with a full course of intravenous (IV) ribavirin, IV fluids management, and real time monitoring of clinical parameters resulted in a positive maternal outcome despite admission to the LFW seven days post onset of symptoms, fetal demise, and a natural still birth delivery. These studies solidify the growing rapid diagnostic, treatment, and surveillance capabilities at the KGH LF Laboratory, and the potential to significantly improve the current high mortality rate caused by LF. As a result of the growing capacity, we were also able to isolate Lassa virus (LASV) RNA from the patient and perform Sanger sequencing where we found significant genetic divergence from commonly circulating Sierra Leonean strains, showing potential for the discovery of a newly emerged LASV strain with expanded geographic distribution. Furthermore, recent emergence of LF cases in Northern Sierra Leone highlights the need for superior diagnostics to aid in the monitoring of LASV strain divergence with potentially increased geographic expansion.

Capacity building permitting comprehensive monitoring of a severe case of Lassa hemorrhagic fever in Sierra Leone with a positive outcome: case report

Lassa fever is a neglected tropical disease with a significant impact on the health care system of endemic West African nations. To date, case reports of Lassa fever have focused on laboratory characterisation of serological, biochemical and molecular aspects of the disease imported by infected individuals from Western Africa to the United States, Canada, Europe, Japan and Israel. Our report presents the first comprehensive real time diagnosis and characterization of a severe, hemorrhagic Lassa fever case in a Sierra Leonean individual admitted to the Kenema Government Hospital Lassa Fever Ward. Fever, malaise, unresponsiveness to anti-malarial and antibiotic drugs, followed by worsening symptoms and onset of haemorrhaging prompted medical officials to suspect Lassa fever. A recombinant Lassa virus protein based diagnostic was employed in diagnosing Lassa fever upon admission. This patient experienced a severe case of Lassa hemorrhagic fever with dysregulation of overall homeostasis, significant liver and renal system involvement, the interplay of pro- and anti-inflammatory cytokines during the course of hospitalization and an eventual successful outcome. These studies provide new insights into the pathophysiology and management of this viral illness and outline the improved infrastructure, research and real-time diagnostic capabilities within LASV endemic areas.

Alcohol decreases RhoA activity through a nitric oxide (NO)/cyclic GMP(cGMP)/protein kinase G (PKG)-dependent pathway in the airway epithelium

BACKGROUND

Alcohol has been shown to have a number of harmful effects on the lung, including increasing the risk of pneumonia and bronchitis. How alcohol increases the risk of these diseases is poorly defined. RhoA is a small guanosine triphosphate (GTP)ase that plays an integral role in many basic functions of airway epithelial cells. It is not known how alcohol affects RhoA activity in the airway epithelium. We hypothesized that brief alcohol exposure modulates RhoA activity in the airway epithelium through a nitric oxide (NO)/cyclic GMP (cGMP)/protein kinase G (PKG)-dependent pathway.

METHODS

Primary airway epithelial cells were cultured and exposed to ethanol at various concentrations and times. The cell layers were harvested and RhoA activity was measured.

RESULTS

Alcohol induced a time- and concentration-dependent decrease in RhoA activity in airway epithelial cells. We were able to block this decrease in activity using Nω-nitro-l-arginine methyl ester (L-NAME) hydrochloride, a nitric oxide synthase (NOS) inhibitor. Likewise, we were able to demonstrate the same decrease in RhoA activation using 0.1 μM sodium nitroprusside, an NO donor. To determine the role of cGMP/PKG, we pretreated the cells with a cGMP antagonist analog, Rp-8Br-cGMPS. This blocked the decrease in RhoA activity caused by alcohol, suggesting that alcohol exerts its effect on RhoA activity through cGMP/PKG.

CONCLUSIONS

Alcohol decreases airway epithelial RhoA activity through an NO/cGMP/PKG-dependent pathway. RhoA activity controls many aspects of basic cellular function, including cell morphology, tight junction formation, and cell cycle progression and gene regulation. Dysregulation of RhoA activity can potentially have several consequences, including dysregulation of inflammation. This may partially explain how alcohol increases the risk of pneumonia and bronchitis.

The B cell response is redundant and highly focused on V1V2 during early subtype C infection in a Zambian seroconverter

High-titer autologous neutralizing antibody responses have been demonstrated during early subtype C human immunodeficiency virus type 1 (HIV-1) infection. However, characterization of this response against autologous virus at the monoclonal antibody (MAb) level has only recently begun to be elucidated. Here we describe five monoclonal antibodies derived from a subtype C-infected seroconverter and their neutralizing activities against pseudoviruses that carry envelope glycoproteins from 48 days (0 month), 2 months, and 8 months after the estimated time of infection. Sequence analysis indicated that the MAbs arose from three distinct B cell clones, and their pattern of neutralization compared to that in patient plasma suggested that they circulated between 2 and 8 months after infection. Neutralization by MAbs representative of each B cell clone was mapped to two residues: position 134 in V1 and position 189 in V2. Mutational analysis revealed cooperative effects between glycans and residues at these two positions, arguing that they contribute to a single epitope. Analysis of the cognate gp120 sequence through homology modeling places this potential epitope near the interface between the V1 and V2 loops. Additionally, the escape mutation R189S in V2, which conferred resistance against all three MAbs, had no detrimental effect on virus replication in vitro. Taken together, our data demonstrate that independent B cells repeatedly targeted a single structure in V1V2 during early infection. Despite this assault, a single amino acid change was sufficient to confer complete escape with minimal impact on replication fitness.

Neutralizing and non-neutralizing monoclonal antibodies against dengue virus E protein derived from a naturally infected patient

Background

Antibodies produced in response to infection with any of the four serotypes of dengue virus generally provide homotypic immunity. However, prior infection or circulating maternal antibodies can also mediate a non-protective antibody response that can enhance the course of disease in a subsequent heterotypic infection. Naturally occurring human monoclonal antibodies can help us understand the protective and pathogenic roles of the humoral immune system in dengue virus infection.

Results

Epstein-Barr Virus (EBV) transformation of B cells isolated from the peripheral blood of a human subject with previous dengue infection was performed. B cell cultures were screened by ELISA for antibodies to dengue (DENV) envelope (E) protein. ELISA positive cultures were cloned by limiting dilution. Three IgG1 human monoclonal antibodies (HMAbs) were purified and their binding specificity to E protein was verified by ELISA and biolayer interferometry. Neutralization and enhancement assays were conducted in epithelial and macrophage-like cell lines, respectively. All three HMAbs bound to E from at least two of the four DENV serotypes, one of the HMAbs was neutralizing, and all were able to enhance DENV infection.

Conclusions

HMAbs against DENV can be successfully generated by EBV transformation of B cells from patients at least two years after naturally acquired DENV infections. These antibodies show different patterns of cross-reactivity, neutralizing, and enhancement activity.

Epitopes for broad and potent neutralizing antibody responses during chronic infection with human immunodeficiency virus type 1

Neutralizing antibody (nAb) response is sporadic and has limited potency and breadth during infection with human immunodeficiency virus type 1 (HIV-1). In rare cases, broad and potent nAbs are actually induced in vivo. Identifying specific epitopes targeted by such broad and potent nAb response is valuable in guiding the design of a prophylactic vaccine aimed to induce nAb. In this study, we have defined neutralizing epitope usage in 7 out of 17 subjects with broad and potent nAbs by using targeted mutagenesis in known neutralizing epitopes of HIV-1 glycoproteins and by using in vitro depletion of serum neutralizing activity by various recombinant HIV-1 glycoproteins. Consistent with recent reports, the CD4 binding site (CD4BS) is targeted by nAbs in vivo (4 of the 7 subjects with defined neutralizing epitopes). The new finding from this study is that epitopes in the gp120 outer domain are also targeted by nAbs in vivo (5 of the 7 subjects). The outer domain epitopes include glycan-dependent epitopes (2 subjects), conserved nonlinear epitope in the V3 region (2 subjects), and a CD4BS epitope composed mainly of the elements in the outer domain (1 subject). Importantly, we found indication for epitope poly-specificity, a dual usage of the V3 and CD4BS epitopes, in only one subject. This study provides a more complete profile of epitope usage for broad and potent nAb responses during HIV-1 infection.

Alcohol up-regulates TLR2 through a NO/cGMP dependent pathway

BACKGROUND

Heavy alcohol consumption is associated with severe bronchitis. This is likely related to increased inflammation in the airways of alcohol abusers. Toll-like receptor 2 (TLR2) is an important mediator of inflammation in the airway epithelium. TLR2 initiates an inflammatory cascade in response to gram-positive bacteria. We have previously shown that alcohol up-regulates TLR2 in the airway epithelium. However, the mechanism of alcohol-mediated up-regulation of TLR2 has not been identified.

METHODS

A human airway epithelial cell line, 16HBE14o-, was exposed to biologically relevant concentrations of alcohol (100 mM) in the presence and absence of N(omega)-Nitro-l-arginine methyl ester hydrochloride, a nitric oxide (NO) synthase inhibitor; and Rp-8-Br-cGMP-S, an antagonist analogue of cGMP. TLR2 was measured using real-time PCR and Western blots. In addition, 16HBE14o- cells were incubated with sodium nitroprusside (SNP), an NO donor, and 8-Br-cGMP, a cGMP analogue. TLR2 was measured using real-time PCR.

RESULTS

N(omega)-Nitro-l-arginine methyl ester hydrochloride blocked the alcohol-mediated up-regulation of TLR2. This indicates that NO plays a key role in alcohol's up-regulation of TLR2. SNP, a NO donor, up-regulated TLR2. Rp-8-Br-CGMP-S attenuated alcohol's up-regulation of TLR2, suggesting that NO was working through cGMP/PKG. 8-Br-cGMP up-regulated TLR2, also demonstrating the importance of cGMP/PKG.

CONCLUSIONS

Alcohol up-regulates TLR2 through a NO/cGMP/PKG dependent pathway in the airway epithelium. This is an important observation in the understanding how alcohol modulates airway inflammation. In addition, this is the first time that cyclic nucleotides have been shown to play a role in the regulation of TLR2.

Escape from autologous neutralizing antibodies in acute/early subtype C HIV-1 infection requires multiple pathways

One aim for an HIV vaccine is to elicit neutralizing antibodies (Nab) that can limit replication of genetically diverse viruses and prevent establishment of a new infection. Thus, identifying the strengths and weaknesses of Nab during the early stages of natural infection could prove useful in achieving this goal. Here we demonstrate that viral escape readily occurred despite the development of high titer autologous Nab in two subjects with acute/early subtype C infection. To provide a detailed portrayal of the escape pathways, Nab resistant variants identified at multiple time points were used to create a series of envelope (Env) glycoprotein chimeras and mutants within the background of a corresponding newly transmitted Env. In one subject, Nab escape was driven predominantly by changes in the region of gp120 that extends from the beginning of the V3 domain to the end of the V5 domain (V3V5). However, Nab escape pathways in this subject oscillated and at times required cooperation between V1V2 and the gp41 ectodomain. In the second subject, escape was driven by changes in V1V2. This V1V2-dependent escape pathway was retained over time, and its utility was reflected in the virus's ability to escape from two distinct monoclonal antibodies (Mabs) derived from this same patient via introduction of a single potential N-linked glycosylation site in V2. Spatial representation of the sequence changes in gp120 suggested that selective pressure acted upon the same regions of Env in these two subjects, even though the Env domains that drove escape were different. Together the findings argue that a single mutational pathway is not sufficient to confer escape in early subtype C HIV-1 infection, and support a model in which multiple strategies, including potential glycan shifts, direct alteration of an epitope sequence, and cooperative Env domain conformational masking, are used to evade neutralization.

Ethanol blocks adenosine uptake via inhibiting the nucleoside transport system in bronchial epithelial cells

BACKGROUND

Adenosine uptake into cells by nucleoside transporters plays a significant role in governing extracellular adenosine concentration. Extracellular adenosine is an important signaling molecule that modulates many cellular functions via 4 G-protein-coupled receptor subtypes (A(1), A(2A), A(2B), and A(3)). Previously, we demonstrated that adenosine is critical in maintaining airway homeostasis and airway repair and that airway host defenses are impaired by alcohol. Taken together, we hypothesized that ethanol impairs adenosine uptake via the nucleoside transport system.

METHODS

To examine ethanol-induced alteration on adenosine transport, we used a human bronchial epithelial cell line (BEAS-2B). Cells were preincubated for 10 minutes in the presence and absence of varying concentrations of ethanol (EtOH). In addition, some cells were pretreated with S-(4-Nitrobenzyl)-6-thioinosine (100 microM: NBT), a potent adenosine uptake inhibitor. Uptake was then determined by addition of [(3)H]-adenosine at various time intervals.

RESULTS

Increasing EtOH concentrations resulted in increasing inhibition of adenosine uptake when measured at 1 minute. Cells pretreated with NBT effectively blocked adenosine uptake. In addition, short-term EtOH revealed increased extracellular adenosine concentration. Conversely, adenosine transport became desensitized in cells exposed to EtOH (100 mM) for 24 hours. To determine the mechanism of EtOH-induced desensitization of adenosine transport, cAMP activity was assessed in response to EtOH. Short-term EtOH exposure (10 minutes) had little or no effect on adenosine-mediated cAMP activation, whereas long-term EtOH exposure (24 hours) blocked adenosine-mediated cAMP activation. Western blot analysis of lysates from unstimulated BEAS-2B cells detected a single 55 kDa band indicating the presence of hENT1 and hENT2, respectively. Real-time RT-PCR of RNA from BEAS-2B revealed transcriptional expression of ENT1 and ENT2.

CONCLUSIONS

Collectively, these data reveal that acute exposure of cells to EtOH inhibits adenosine uptake via a nucleoside transporter, and chronic exposure of cells to EtOH desensitizes the adenosine transporter to these inhibitory effects of ethanol. Furthermore, our data suggest that inhibition of adenosine uptake by EtOH leads to an increased extracellular adenosine accumulation, influencing the effect of adenosine at the epithelial cell surface, which may alter airway homeostasis.

Profiling the specificity of neutralizing antibodies in a large panel of plasmas from patients chronically infected with human immunodeficiency virus type 1 subtypes B and C

Identifying the viral epitopes targeted by broad neutralizing antibodies (NAbs) that sometimes develop in human immunodeficiency virus type 1 (HIV-1)-infected subjects should assist in the design of vaccines to elicit similar responses. Here, we investigated the activities of a panel of 24 broadly neutralizing plasmas from subtype B- and C-infected donors using a series of complementary mapping methods, focusing mostly on JR-FL as a prototype subtype B primary isolate. Adsorption with gp120 immobilized on beads revealed that an often large but variable fraction of plasma neutralization was directed to gp120 and that in some cases, neutralization was largely mediated by CD4 binding site (CD4bs) Abs. The results of a native polyacrylamide gel electrophoresis assay using JR-FL trimers further suggested that half of the subtype B and a smaller fraction of subtype C plasmas contained a significant proportion of NAbs directed to the CD4bs. Anti-gp41 neutralizing activity was detected in several plasmas of both subtypes, but in all but one case, constituted only a minor fraction of the overall neutralization activity. Assessment of the activities of the subtype B plasmas against chimeric HIV-2 viruses bearing various fragments of the membrane proximal external region (MPER) of HIV-1 gp41 revealed mixed patterns, implying that MPER neutralization was not dominated by any single specificity akin to known MPER-specific monoclonal Abs. V3 and 2G12-like NAbs appeared to make little or no contribution to JR-FL neutralization titers. Overall, we observed significant titers of anti-CD4bs NAbs in several plasmas, but approximately two-thirds of the neutralizing activity remained undefined, suggesting the existence of NAbs with specificities unlike any characterized to date.

Use of tissue culture cell lines to evaluate HIV antiviral resistance

Most current assays of HIV antiviral resistance are based on either sequencing of viral genes (genotypic assays) or amplification and insertion of these genes into standardized virus backbones and culture. These latter are called phenotypic assays. But the only generally accepted phenotypic assay is based upon culture of intact patient virus, performed in phytohemagglutinin-activated peripheral blood mononuclear cells (PHA blasts) in the presence of differing drug concentrations. However, PHA blast culture is difficult and not always reproducible. Therefore we have sought cell lines that may produce more predictable results, yet faithfully mirror results in PHA blasts. We have compared 10 different cell lines for receptor and coreceptor expression, growth of laboratory-adapted strains of HIV, growth by direct inoculation of PBMC from infected patients, and in assays of antiviral drug effects. One of these cell lines, C8166-R5, is statistically not inferior to CD8-depleted PHA blasts for culturing HIV from the peripheral blood cells of patients. The effective concentrations of antiviral drugs of all classes were similar when assayed in C8166-R5 or PHA blasts. Known drug-resistant isolates grown in C8166-R5 demonstrated the predicted effects. We followed a patient longitudinally and demonstrated that resistance testing in C8166-R5 was predictive of clinical outcome. These experiments represent the first steps in developing a clinically useful phenotypic drug resistance assay based upon culturing the patient's own virus.

Relationship of HIV-1 and SIV envelope glycoprotein trimer occupation and neutralization

Insights into the process of HIV-1 neutralization may assist rational vaccine design. Here, we compared antibody neutralization against the JR-FL primary isolate and trimer binding affinities judged by native PAGE. Monovalent Fab-trimer binding and neutralization showed a direct quantitative relationship, implying that neutralization begins as each trimer is occupied by one antibody. At saturation, three Fab or soluble CD4 molecules engaged each trimer. In contrast, a maximum of one soluble CD4 molecule bound to functional SIV trimers with a truncated a gp41 tail. Remarkably, soluble CD4 was found to trigger dramatic enhancement of this virus. Unlike Fabs, a quantitative correlation between JR-FL trimer binding and neutralization was unclear for some, but not all IgGs, as neutralization was markedly increased, but trimer affinity was largely unchanged. In addition, only one molecule of certain gp41-specific IgGs appeared to be able to bind each trimer. We discuss the implications of these findings in weighing the relative contributions of size, multivalent binding and other possible effects of IgGs to explain their increased potency.

Distribution of galanin receptor-2 immunoreactive neurones in the ovine hypothalamus: no evidence for involvement in the control of gonadotrophin-releasing hormone secretion

Galanin is a small neuropeptide that mediates its effects via three receptor isoforms: galanin receptor-1, galanin receptor-2 and galanin receptor-3 (Gal-R1, Gal-R2 and Gal-R3). Galanin is thought to be an important intermediate in signalling in the hypothalamic-pituitary-gonadal axis and has been widely detected in the ovine hypothalamus. The expression of galanin and Gal-R1 has been reported to fluctuate during the reproductive cycle. Although the distribution of Gal-R1 has been determined in the ovine hypothalamus, the distribution of Gal-R2 was hitherto unknown. Using immunohistological and immunofluorescence techniques, we have mapped the distribution of Gal-R2 in the ovine hypothalamus, collected during the follicular phase of the oestrous cycle and examined colocalisation of Gal-R2 with oestrogen receptor alpha (ERalpha) and gonadotrophin-releasing hormone (GnRH). Gal-R2 was expressed in several regions of the hypothalamus (supraoptic nucleus, paraventricular nucleus, ventromedial nucleus, arcuate nucleus) but not as widely expressed as Gal-R1. Areas of Gal-R2 expression overlapped with those reported for Gal-R1. We observed that, in certain defined regions of the hypothalamus, up to 50% of neurones that express Gal-R2 also express ERalpha. No neurones coexpressed Gal-R2 and GnRH. Thus, we conclude that, in follicular phase animals, this receptor plays little or no role in direct intermediary signal transmission in GnRH-mediated control of the reproductive cycle.

A Ramberg–Bäcklund route to the stilbenoid anti-cancer agents combretastatin A-4 and DMU-212

A concise route to combretastatin A-4, a potent inhibitor of tubulin polymerisation, using a Ramberg-Bäcklund reaction to form the key (Z)-stilbene unit has been developed; this Ramberg-Bäcklund approach has also been extended to prepare the (E)-stilbene DMU-212, which also possesses interesting growth inhibitory properties.

Genetic and neutralization properties of subtype C human immunodeficiency virus type 1 molecular env clones from acute and early heterosexually acquired infections in Southern Africa

A standard panel of subtype C human immunodeficiency virus type 1 (HIV-1) Env-pseudotyped viruses was created by cloning, sequencing, and characterizing functional gp160 genes from 18 acute and early heterosexually acquired infections in South Africa and Zambia. In general, the gp120 region of these clones was shorter (most evident in V1 and V4) and less glycosylated compared to newly transmitted subtype B viruses, and it was underglycosylated but no different in length compared to chronic subtype C viruses. The gp120s also exhibited low amino acid sequence variability (12%) in V3 and high variability (39%) immediately downstream of V3, a feature shared with newly transmitted subtype B viruses and chronic viruses of both subtypes. When tested as Env-pseudotyped viruses in a luciferase reporter gene assay, all clones possessed an R5 phenotype and resembled primary isolates in their sensitivity to neutralization by HIV-1-positive plasmas. Results obtained with a multisubtype plasma panel suggested partial subtype preference in the neutralizing antibody response to infection. The clones were typical of subtype C in that all were resistant to 2G12 (associated with loss of N-glycosylation at position 295) and most were resistant to 2F5, but all were sensitive to 4E10 and many were sensitive to immunoglobulin G1b12. Finally, conserved neutralization epitopes in the CD4-induced coreceptor binding domain of gp120 were poorly accessible and were difficult to induce and stabilize with soluble CD4 on Env-pseudotyped viruses. These results illustrate key genetic and antigenic properties of subtype C HIV-1 that might impact the design and testing of candidate vaccines. A subset of these gp160 clones are suitable for use as reference reagents to facilitate standardized assessments of vaccine-elicited neutralizing antibody responses.

Studies on GM-CSF DNA as an adjuvant for neutralizing Ab elicited by a DNA/MVA immunodeficiency virus vaccine

Here, we use a vaccine consisting of DNA priming followed by MVA boosting in rhesus macaques to investigate the ability of GM-CSF DNA to serve as an adjuvant for the elicitation of neutralizing Ab against an HIV-1 Env. The trial used Gag, Pol, and Env sequences from SHIV-89.6 in the immunogens and a neutralization escape variant of SHIV-89.6, SHIV-89.6P, for challenge. Co-delivery of GM-CSF and vaccine DNAs enhanced the temporal appearance of neutralizing Ab and broadened the specificity of the neutralizing activity to include SHIV-89.6P. Two long-term SHIV-89.6 infections elicited neutralizing activity for SHIV-89.6 but not SHIV-89.6P. Studies on the avidity of the anti-Env antisera revealed that the GM-CSF-adjuvanted vaccine had elicited higher avidity Ab than the non-adjuvanted vaccine or the infection. The GM-CSF-adjuvanted group showed a trend towards better control of the challenge infection and had better control of re-emergent virus (P < 0.01) than the non-adjuvanted group.

Kinetic rates of antibody binding correlate with neutralization sensitivity of variant simian immunodeficiency virus strains

Increasing evidence suggests that an effective AIDS vaccine will need to elicit both broadly reactive humoral and cellular immune responses. Potent and cross-reactive neutralization of simian immunodeficiency virus (SIV) and human immunodeficiency virus type 1 (HIV-1) by polyclonal and monoclonal antibodies is well documented. However, the mechanisms of antibody-mediated neutralization have not been defined. The current study was designed to determine whether the specificity and quantitative properties of antibody binding to SIV envelope proteins correlate with neutralization. Using a panel of rhesus monoclonal antibodies previously characterized for their ability to bind and neutralize variant SIVs, we compared the kinetic rates and affinity of antibody binding to soluble envelope trimers by using surface plasmon resonance. We identified significant differences in the kinetic rates but not the affinity of monoclonal antibody binding to the neutralization-sensitive SIV/17E-CL and neutralization-resistant SIVmac239 envelope proteins that correlated with the neutralization sensitivities of the corresponding virus strains. These results suggest for the first time that neutralization resistance may be related to quantitative differences in the rates but not the affinity of the antibody-envelope interaction and may provide one mechanism for the inherent resistance of SIVmac239 to neutralization in vitro. Further, we provide evidence that factors in addition to antibody binding, such as epitope specificity, contribute to the mechanisms of neutralization of SIV/17E-CL in vitro. This study will impact the method by which HIV/SIV vaccines are evaluated and will influence the design of candidate AIDS vaccines capable of eliciting effective neutralizing antibody responses.