HLA class II diversity in HIV-1 uninfected individuals from the placebo arm of the RV144 Thai vaccine efficacy trial.

The RV144 HIV vaccine trial in Thailand elicited antibody responses to the envelope of HIV-1, which correlated significantly with the risk of HIV-1 acquisition. Human leukocyte antigen (HLA) class II molecules are essential in antigen presentation to CD4 T cells for activation of B cells to produce antibodies. We genotyped the classical HLA-DRB1, DQB1, and DPB1 genes in 450 individuals from the placebo arm of the RV144 study to determine the background allele and haplotype frequencies of these genes in this cohort. High-resolution 4 and 6-digit class II HLA typing data was generated using sequencing-based methods. The observed diversity for the HLA loci was 33 HLA-DRB1, 15 HLA-DQB1, and 26 HLA-DPB1 alleles. Common alleles with frequencies greater than 10% were DRB1*07:01, DRB1*09:01, DRB1*12:02, DRB1*15:02, DQB1*02:01/02, DQB1*03:01, DQB1*03:03, DQB1*05:01, DQB1*05:02, DPB1*04:01:01, DPB1*05:01:01, and DPB1*13:01:01. We identified 28 rare alleles with frequencies of less than 1% in the Thai individuals. Ambiguity for HLA-DPB1*28:01 in exon 2 was resolved to DPB1*296:01 by next-generation sequencing of all exons. Multi-locus haplotypes including HLA class I and II loci were reported in this study. This is the first comprehensive report of allele and haplotype frequencies of all three HLA class II genes from a Thai population. A high-resolution genotyping method such as next-generation sequencing avoids missing rare alleles and resolves ambiguous calls. The HLA class II genotyping data generated in this study will be beneficial not only for future disease association/vaccine efficacy studies related to the RV144 study, but also for similar studies in other diseases in the Thai population, as well as population genetics and transplantation studies.

HIV viraemia during hepatitis B vaccination shortens the duration of protective antibody levels.

OBJECTIVES: Individuals with HIV infection often have early waning of protective antibody following hepatitis B virus (HBV) vaccination. HIV viraemia at the time of vaccination may limit the durability of serum anti-HBV surface antibody (HBsAb) levels. We investigated the relationship of HIV plasma viral load (VL) and duration of HBsAb among vaccinees enrolled in the US Military HIV Natural History Study. METHODS: We included in the study participants who had no history of prior HBV infection, who had received all HBV vaccine doses after HIV diagnosis, and who had demonstrated an initial vaccine response, defined as HBsAb ≥ 10 IU/L. Responders were retrospectively followed with serial HBV serology from the time of the last vaccine dose until the development of waning (HBsAb < 10 IU/L) or the last HBsAb measurement. Time to and risk for waning were evaluated with Kaplan-Meier survival methods and Cox proportional hazards models, respectively. RESULTS: A total of 186 initial vaccine responders were identified. During 570 person-years of observation, HBsAb waned in 52 of 186 participants (28%). The cumulative proportion maintaining HBsAb ≥ 10 IU/L was 83% at 2 years and 56% at 5 years. Participants with an undetectable VL [hazard ratio (HR) 0.37; 95% confidence interval (CI) 0.18-0.76] or with detectable VL of ≤ 10 000 copies/mL (HR 0.46; 95% CI 0.21-1.00) had reduced risk of waning. Other factors including age, number of vaccine doses, CD4 count, and receipt of highly active antiretroviral therapy (HAART) were not significantly associated with risk of waning HBsAb. CONCLUSIONS: Undetectable or low HIV VL at the time of HBV vaccination is associated with greater durability of vaccine response in patients with HIV infection.

The Colletotrichum destructivum species complex - hemibiotrophic pathogens of forage and field crops.

Colletotrichum destructivum is an important plant pathogen, mainly of forage and grain legumes including clover, alfalfa, cowpea and lentil, but has also been reported as an anthracnose pathogen of many other plants worldwide. Several Colletotrichum isolates, previously reported as closely related to C. destructivum, are known to establish hemibiotrophic infections in different hosts. The inconsistent application of names to those isolates based on outdated species concepts has caused much taxonomic confusion, particularly in the plant pathology literature. A multilocus DNA sequence analysis (ITS, GAPDH, CHS-1, HIS3, ACT, TUB2) of 83 isolates of C. destructivum and related species revealed 16 clades that are recognised as separate species in the C. destructivum complex, which includes C. destructivum, C. fuscum, C. higginsianum, C. lini and C. tabacum. Each of these species is lecto-, epi- or neotypified in this study. Additionally, eight species, namely C. americae-borealis, C. antirrhinicola, C. bryoniicola, C. lentis, C. ocimi, C. pisicola, C. utrechtense and C. vignae are newly described.

Herpes simplex virus type 2 and HIV infection among US military personnel: implications for health prevention programmes.

US military personnel are routinely screened for HIV infection. Herpes simplex virus type 2 (HSV-2) is a risk factor for HIV acquisition. To determine the association between HSV-2 and HIV, a matched case-control study was conducted among US Army and Air Force service members with incident HIV infections (cases) randomly matched with two HIV-uninfected service members (controls) between 2000 and 2004. HSV-2 prevalence was significantly higher among cases (30.3%, 138/456) than among controls (9.7%, 88/912, P < 0.001). HSV-2 was strongly associated with HIV in univariate (odds ratio [OR] = 4.2, 95% confidence interval [CI] = 3.1-5.8) and multiple analyses (adjusted [OR] = 3.9, 95% CI = 2.8-5.6). The population attributable risk percentage of HIV infection due to HSV-2 was 23%. Identifying HSV-2 infections may afford the opportunity to provide targeted behavioural interventions that could decrease the incidence of HIV infections in the US military population; further studies are needed.

Induction of c-fos in hamster accessory olfactory bulbs by natural and cloned aphrodisin.

Male hamsters were exposed to the female pheromone, aphrodisin (APH), its cloned protein backbone (rAPH), and the homologous lipocalin, beta-lactoglobulin (beta-LG). Of these, only APH elicited mating behavior. Enhanced c-fos protein was found in the nuclei of neurons in the accessory olfactory bulb (AOB) after exposure to these stimuli. Relative to beta-LG, both rAPH and APH produced significant increases in AOB labeling. The modest labeling elicited by rAPH was evenly distributed, but the heavier staining elicited by APH was concentrated in the caudal region of the AOB. Thus, pheromone receptor neurons in the basal compartment of the vomeronasal epithelium, which project to the caudal region of the AOB, may respond to APH and provide the input which drives mating behavior.

Ultrastructure of the Infection of Sorghum bicolor by Colletotrichum sublineolum.

ABSTRACT Ultrastructural studies of the infection of susceptible and resistant cultivars of Sorghum bicolor by Colletotrichum sublineolum were conducted. Initial penetration events were the same on both susceptible and resistant cultivars. Germ tubes originating from germinated conidia formed globose, melanized appressoria, that penetrated host epidermal cells directly. Appressoria did not produce appressorial cones, but each penetration pore was surrounded by an annular wall thickening. Inward deformation of the cuticle and localized changes in staining properties of the host cell wall around the infection peg suggests that penetration involves both mechanical force and enzymic dissolution. In compatible interactions, penetration was followed by formation of biotrophic globular infection vesicles in epidermal cells. Filamentous primary hyphae developed from the vesicles and went on to colonize many other host cells as an intracellular mycelium. Host cells initially survived penetration. The host plasma membrane invaginated around infection vesicles and primary hyphae and was appressed tightly to the fungal cell wall, with no detectable matrix layer at the interface. Necrotrophic secondary hyphae appeared after 66 h and ramified through host tissue both intercellularly and intracellularly, forming hypostromatic acervuli by 114 h. Production of secondary hyphae was accompanied by the appearance of electron-opaque material within infected cells. This was thought to represent the host phytoalexin response. In incompatible interactions, infection vesicles and primary hyphae were formed in epidermal cells by 42 h. However, they were encrusted with electron-opaque material and appeared dead. These observations are discussed in relation to the infection processes of other Colletotrichum spp. and the host phytoalexin response.

Responses of olfactory receptor neurons in Utetheisa ornatrix to gender-specific odors.

We recorded the electrophysiological responses of individual olfactory receptor neurons in sensilla trichodea on the antennae of adult arctiid moths, Utetheisa ornatrix, to stimulation with volatiles associated with both sexes. All trichoid sensilla contain at least two receptor neurons, each with distinct action potential amplitudes and waveforms, that respond dichotomously to male and female odors. Although, neither female neuron responds to extracts of coremata or the male-produced pheromone hydroxydanaidal, they do respond in a gender-specific manner to the volatiles emanating from whole pupae, hemolymph, thoracic froth, and adult animals of several ages. Thoracic froth, which contains pyrrolizidine alkaloids, is thought to play a role in defense. Froth from moths reared on diets, with or without added pyrrolizidine alkaloids, were equally effective in eliciting gender-specific patterns of response. Male trichoid receptor neurons respond to these same materials with similar patterns of activation. These receptor neurons provide information about substances, which we have termed "gender odors," that are persistently emitted by nearby animals. These substances do not appear to be the same as those already known to be involved in defense or the sexual dialog between individuals.

Immunomagnetic purification of Colletotrichum lindemuthianum appressoria.

We developed a method to purify appressoria of the bean anthracnose fungus Colletotrichum lindemuthianum for biochemical analysis of the cell surface and to compare appressoria with other fungal structures. We used immunomagnetic separation after incubation of infected bean leaf homogenates with a monoclonal antibody that binds strongly to the appressoria. Preparations with a purity of >90% could be obtained. Examination of the purified appressoria by transmission electron microscopy showed that most had lost their cytoplasm. However, the plasma membrane was retained, suggesting that there is some form of attachment of this membrane to the cell wall. The purified appressoria can be used for studies of their cell surface, and we have shown that there are clear differences in the glycoprotein constituents of cell walls of appressoria compared with mycelium.

The distribution and expression of a biotrophy-related gene, CIH1, within the genus Colletotrichum.

Abstract During the biotrophic phase of the infection process of the hemibiotrophic anthracnose fungus Colletotrichum lindemuthianum, an intracellular hypha develops within epidermal cells of its host, Phaseolus vulgaris. This is followed by the formation of secondary hyphae during the necrotrophic phase. Previous work using a monoclonal antibody, UB25, has identified a glycoprotein that is specific to the interfacial matrix that forms between the wall of the intracellular hypha and the invaginated host plasma membrane. The gene encoding the protein identified by UB25 was cloned by immunoscreening and designated CIH1. The predicted amino acid sequence revealed a proline-rich glycoprotein, and biochemical evidence suggested that it formed a cross-linked structure at the biotrophic interface. Although CIH1 is a fungal gene, its product has several similarities to plant cell wall proteins. In this paper, we have surveyed the distribution and expression of CIH1 within the genus Colletotrichum, encompassing both necrotrophic and hemibiotrophic species. The results show that homologues of the CIH1 gene are present in all the Colletotrichum species tested. Northern blot studies of the time course of the infection process in planta have shown that CIH1 is expressed by both C. lindemuthianum in bean and C. trifolii in alfalfa during the biotrophic phase of fungal development. Immunofluorescence labelling of infected epidermal strips with UB25 revealed that the intracellular hyphae formed by C. destructivum as it infects alfalfa were specifically labelled in a similar way to those formed by C. lindemuthianum in bean. Northern and Western analysis showed that CIH1 was also expressed by C. lindemuthianum in vitro, though not constitutively. Overall, the evidence supports a role for CIH1 in biotrophy within the genus Colletotrichum.

Colletotrichum: A model genus for studies on pathology and fungal-plant interactions.

Species of Colletotrichum use diverse strategies for invading host tissue, ranging from intracellular hemibiotrophy to subcuticular intramural necrotrophy. In addition, these pathogens develop a series of specialized infection structures, including germ tubes, appressoria, intracellular hyphae, and secondary necrotrophic hyphae. Colletotrichum species provide excellent models for studying the molecular basis of infection structure differentiation and fungal-plant interactions. In this review we cover the various stages of the infection processes of Colletotrichum species, including spore adhesion and germination, germ tube and appressorium differentiation and functions, and biotrophic and necrotrophic development. The contribution of molecular, biochemical, and immunological approaches to the identification of genes and proteins relevant to each stage of fungal development will be considered. As well as reviewing results from several groups, we also describe our own work on the hemibiotrophic pathogen, C. lindemuthianum.

Expression cloning of a fungal proline-rich glycoprotein specific to the biotrophic interface formed in the Colletotrichum-bean interaction.

The monoclonal antibody, UB25, recognises a glycoprotein specifically located at the biotrophic interface formed in the Colletotrichum lindemuthianum-bean interaction. The antibody labels the walls of intracellular hyphae and the interfacial matrix which separates them from the invaginated host plasma membrane. In Western blots, UB25 recognises a ladder of bands which are multiples of M(r) 40.5 kDa. A full length cDNA encoding the glycoprotein recognised by UB25 has been isolated by expression cloning and designated CIH1 (Colletotrichum Intracellular Hypha 1). In vitro transcription/translation of CIH1, and transfection of mammalian COS cells, showed that UB25 recognized the expressed product in both procedures confirming that the clones isolated were true positives. Southern analysis of bean and C. lindemuthianum genomic DNA indicated that the CIH1 glycoprotein is fungally encoded and Northern analysis showed that it is only expressed in planta. Analysis of the deduced amino acid sequence of CIH1 indicates the presence of an N-terminal signal sequence and two possible sites for N-glycosylation. The N-terminal domain of the mature protein is rich in proline and contains several short repetitive motifs. CIH1 is thus a fungal proline-rich glycoprotein which appears to form a cross-linked structure in planta and, as such, resembles plant cell wall proline- and hydroxyproline-rich proteins. Possible functions for the CIH1 protein in the establishment and maintenance of biotrophy are discussed.

Pemenone and androstenone do not cross-adapt reciprocally.

Explorations of the qualitative and quantitative differences between the odors of pemenone (PEM), androstenone (AND) and isovaleric acid (IVA) show that they share a number of common perceptual characteristics. Among these are similarities in their odor quality and relative intensity ratings. PEM is also an efficient cross-adaptor and modulator of a subject's AND sensitivity. Here we evaluate the reciprocal efficacy of AND adaptation to alter the perceived intensity and quality of PEM, IVA and AND. Twenty-three people, including both those osmic and allosmic (n = 11) for the putrid odor quality of PEM, were tested. Following training in odor quality and intensity rating techniques, subjects sampled a selected substance for 2 min to obtain adaptation and then reported quality and intensity ratings for the three test stimuli. There was significant self-adaptation by PEM and IVA in all subjects, but self-adaptation by AND was only observed in the PEM-osmic subjects. AND did not cross-adapt PEM or IVA to any significant extent. Collectively, these results contrast with our earlier study in which PEM was an efficient cross-adaptor of AND. Here, AND was no more efficient than the control as an adapting substance for PEM, despite significant self-adaptation of PEM by itself. This lack of reciprocity in the effectiveness of PEM and AND as cross-adapters is not related to differences in odor intensity, as the PEM and AND concentrations were adjusted for each subject to elicit comparable intensity reports. These results support the notion that PEM, AND and IVA share certain perceptual characteristics, but interact differentially with three or more sets of perceptual channels that are now thought to result in a putrid odor quality.

Pheromone-induced second messenger signaling in the hamster vomeronasal organ.

Compounds present in estrous hamster vaginal discharge modulate male attraction and mounting behavior. These compounds are differentially processed by chemosensory neurons in the main olfactory epithelium (MOE) and vomeronasal organ (VNO). The transduction cascade responsible for this processing is unclear in the VNO, although studies of the MOE suggest that the second messengers cAMP or IP3 may be involved. Here we demonstrate that purified aphrodisin, a hamster mounting pheromone, modulates IP3 production in male VNO membranes without altering cAMP production. Aphrodisin does not alter the concentration of either second messenger in membranes from the MOE. These results confirm the specificity of the VNO in the processing of mounting pheromones and establishes the importance of IP3 cascades in mammalian reproductive behavior.

Semantic-free scaling of odor quality.

The validity of the odor quality reports given by naive human subjects is often questionable. On the one hand, social conventions can influence the labeling of odorants, especially those that have putrid or uncommon odor qualities, and on the other, semantic differences exist for odor descriptors among individuals. We are interested in the individual differences in the quality reports elicited by two nominally putrid odorants, androstenone (AND) and pemenone (PEM). Here we sought to establish empirical support for the individual differences previously obtained in studies of their odor quality, using a nonverbal, semantic-free method of classification. Undergraduate volunteers sniffed a moderate concentration (390 microM) of PEM, rated its intensity, and provided a verbal odor descriptor. The subjects were then classified as PEM osmic (n = 42) if the quality report was putrid (rancid, urinous, sweaty), allosmic (n = 23), if the quality was nonputrid, and anosmic (n = 39) if no odor was detected. The subjects then sorted 15 odorants matched for intensity, five selected from each of three nominal odor quality types, into as many odor groups as they wished, as long as each group contained all of the compounds with similar odors. The number of times each odorant was paired with another was used as data for an independent multidimensional scaling with ALSCAL, for each class of subject. Three-dimensional solutions showed that this nonverbal, semantic-free scaling method produced odor classifications consistent with those found when each class of subject reported odor qualities from a defined list of quality descriptors. Cluster analysis of the MDS coordinates revealed that these solutions also retained the individual odor quality differences thought to be characteristic of osmic, allosmic and anosmic subjects.

Electrophysiological responses from receptor neurons in mosquito maxillary palp sensilla.

We recently completed an electrophysiological study of the receptor neurons found in the sensilla basiconica on the maxillary palps of mosquitoes. Our results describe a class of receptor neurons whose properties could provide the afferent input required for some aspects of CO2-modulated host-locating behaviour. First, these neurons have apparent thresholds (150-300 ppm) which are at, or below, the concentration of CO2 (300-330 ppm) normally reported for ambient air. Second, their concentration-response functions are steep, such that small (50 ppm) fluctuations in concentration elicit reliable changes in activity. Third, they behave like absolute CO2 detectors in that their ability to respond to step increases in CO2 concentration is little influenced by the background concentration of CO2. And fourth, a linear extrapolation of the observed response function to the levels that might be expected near vertebrate hosts suggests that these neurons have sufficient dynamic range to cover those CO2 concentrations that should be encountered during a large portion of the behaviour likely involved in host location. The mosquito CO2 receptor neuron thus has an appropriately low threshold and a steep concentration-response function, it is not desensitized by ambient levels of stimulation, and it has a dynamic range appropriate for the distribution of CO2 concentrations expected in the environment. In addition, this sensillum contains two other receptor neurons, neither of which respond to CO2. One of these neurons responds to stimulation with very low doses of another behaviourally relevant compound, 1-octen-3-ol.

Electrophysiological responses of receptor neurons in mosquito maxillary palp sensilla to carbon dioxide.

Sensilla basiconica on the maxillary palps of female Aedes aegypti contain a receptor neuron which produces a phasic-tonic pattern of action potential response to low concentrations (150-300 ppm) of carbon dioxide (CO2), a stimulus known to be involved with host seeking behavior. These receptor neurons respond reliably to small increments in CO2 concentration (e.g., 50 ppm). We were particularly interested in evaluating the possibility that the sensitivity to step increases in CO2 concentration could be modulated by alterations in the background levels of CO2, over a range which might be encountered during host-seeking behavior. We report here that the response (impulses/s) to a single pulse of a given concentration of CO2 appears to be independent of the background level of CO2, unless that level is equal to or greater than the concentration of the stimulus pulse. Females of other mosquito species, including: Anopheles stephensi, Culex quinquefasciatus, Culiseta melanura, and Aedes taeniorhynchus, also possess sensilla with receptor neurons that respond with comparable sensitivity to CO2 stimulation. However, there is much interspecific variation in both the external morphology of the maxillary palp and the distribution of sensilla along the palp. Male Ae. aegypti have morphologically similar sensilla which also contain a receptor neuron that responds to CO2.

Enhanced sensitivity to androstenone following regular exposure to pemenone.

The responses elicited by olfactory stimuli may be modified throughout an organism's life. For example, Wysocki et al. found that regular presentations of 5a-androst-16-en-3-one (androstenone) to anosmic subjects resulted in a graded increase in the perceived intensity of this substance in about half of their subjects (Wysocki et al., 1989). The increased sensitivity they observed appeared to be specific to the exposed odorant and was presumed to occur only in anosmic subjects. Here, we continue our explorations of the individual differences in olfactory capabilities among subjects initially classified by their ability to detect and identify the odor of the diastereoisomeric ketone, cis-4-(4'-t-butylcyclo-hexyl)-4-methyl-2-pentanone (pemenone) which shares with androstenone a pronounced urine-sweaty odor. We asked if regular pemenone exposure enhances the sensitivity of human subjects to pemenone, androstenone, isovaleric acid, or phenylethyl alcohol and, if shifts in threshold occurred, were they specific to particular odorants and classes of subject? Detection thresholds for the four substances were determined before and after 7-8 weeks of regular, biweekly, exposure to pemenone (n = 18 subjects) or a control substance (22 subjects). Significant decreases in threshold were seen in the experimental group, relative to the control group, for androstenone, but not for the other compounds evaluated. Neither gender nor initial pemenone osmicity significantly affected the frequency of subjects with enhanced sensitivity. These findings show that a subject's sensitivity to one odorant can be enhanced by exposure to another, chemically distinct compound.(ABSTRACT TRUNCATED AT 250 WORDS)

Continent-ocean chemical heterogeneity in the mantle based on seismic tomography.

Seismic models of global-scale lateral heterogeneity in the mantle show systematic differences below continents and oceans that are too large to be purely thermal in origin. An inversion of the geoid, based on a seismic model that includes viscous flow in the mantle, indicates that the differences beneath continents and oceans can be accounted for by differences in composition in the upper mantle superposed on mantle-wide thermal heterogeneities. The net continent-ocean density differences, integrated over depth, are small and cause only a low flux of mass and heat across the asthenosphere and mantle transition zone.

Individual differences in the perceived intensity and quality of specific odors following self- and cross-adaptation.

Adaptation techniques have traditionally been employed in sensory physiology and psychology to characterize afferent pathways and to dissect the quantitative and, to a lesser degree, the qualitative aspects of perception. We continue to explore the individual differences in olfactory capabilities among subjects initially classified by their ability to detect and identify the diastereoisomeric ketone, cis-4-(4'-t-butylcyclohexyl)-4-methyl-2-pentanone (pemenone) which shares with 5 alpha-androst-16-en-3-one (androstenone) a pronounced urine-sweaty odor. Our previous studies of these and other compounds for which specific anosmias were said to exist revealed significant relationships between intensity scores and a corresponding clustering of the odor quality descriptors used to characterize these materials by subjects judged to be specifically anosmic for the urinous note. Here, we attempt to dissect the web of interactions which give rise to individual differences in perceived odor quality by evaluating the effects of self- and cross-adaptation on the intensity and quality reports elicited by pemenone, androstenone and four other odors in 18 human subjects including both pemenone-osmic and non-osmic (n = 6) individuals. Intensity and quality ratings for the six compounds were obtained before and after an adaptation sequence in which subjects sniffed a test odorant, pemenone or the diluent. For each odorant, intensity ratings under the different adapting conditions were compared by ANOVA. Self-adaptation was universal but cross-adaptation by pemenone was only found in the intensity ratings of androstenone. The intensity ratings of isovaleric acid, which shares the urinous note with pemenone and androstenone, were unaffected by pemenone adaptation. Most of the subjects judged to be osmic still reported a urinous odor quality for androstenone and isovaleric acid following pemenone adaptation. Except for shifts to the no-odor category, adaptation did not significantly alter the odor quality reports of osmic or non-osmic individuals. This suggests that the odor quality reports engendered by these substances are multidimensional and that compounds which share the same odor quality label may interact with different perceptual channels.

Temporal analysis of adaptation in moth (Trichoplusia ni) pheromone receptor neurons.

The temporal pattern of response in chemoreceptor neurons reflects both the temporal distribution of stimuli and the timing of signal transduction, action potential generation and propagation. Here we analyze the temporal characteristics of the responses elicited in pheromone receptor neurons by computer-controlled rectangular pulses of odorant. Extracellular recordings from the HS sensilla trichodea on the antenna of male Trichoplusia ni reveal the activity of two neurons: the "A" neuron, which responds to the major component of the female pheromone blend, (Z)7-dodecenyl acetate and the "B" neuron, which responds to (Z)7-dodecenol. "B" neurons were divided into two classes (HR, LR), based on the magnitude and temporal pattern of their response to (Z)7-dodecenol. Most "A" and HR "B" neurons responded to rectangular pulses of various durations (0.1-40 s) with an initial phasic burst (approximately 100 ms), followed by a slowly declining tonic component. At moderate and elevated pheromone doses, prolonged stimulation resulted in significant reductions in the tonic response levels (adaptation); stimuli of increasing duration effected greater adaptation. Most LR "B" neurons lacked a phasic response component and showed virtually no adaptation with prolonged stimulation. Pheromone receptor neurons may differ in both their spectral and temporal response properties which may provide the animal with additional sensory information for blend discrimination and spatial orientation in complex natural pheromone plumes. The potential functional value of adaptation in the moth pheromone communication system is discussed.