Holographic stimulation of opposing amygdala ensembles bidirectionally modulates valence-specific behavior via mutual inhibition

The basolateral amygdala (BLA) is an evolutionarily conserved brain region, well known for valence processing. Despite this central role, the relationship between activity of BLA neuronal ensembles in response to appetitive and aversive stimuli and the subsequent expression of valence-specific behavior has remained elusive. Here, we leverage two-photon calcium imaging combined with single-cell holographic photostimulation through an endoscopic lens to demonstrate a direct causal role for opposing ensembles of BLA neurons in the control of oppositely valenced behavior in mice. We report that targeted photostimulation of either appetitive or aversive BLA ensembles results in mutual inhibition and shifts behavioral responses to promote consumption of an aversive tastant or reduce consumption of an appetitive tastant, respectively. Here, we identify that neuronal encoding of valence in the BLA is graded and relies on the relative proportion of individual BLA neurons recruited in a stable appetitive or quinine ensemble.

Pain induces adaptations in ventral tegmental area dopamine neurons to drive anhedonia-like behavior

The persistence of negative affect in pain leads to co-morbid symptoms such as anhedonia and depression-major health issues in the United States. The neuronal circuitry and contribution of specific cellular populations underlying these behavioral adaptations remains unknown. A common characteristic of negative affect is a decrease in motivation to initiate and complete goal-directed behavior, known as anhedonia. We report that in rodents, inflammatory pain decreased the activity of ventral tegmental area (VTA) dopamine (DA) neurons, which are critical mediators of motivational states. Pain increased rostromedial tegmental nucleus inhibitory tone onto VTA DA neurons, making them less excitable. Furthermore, the decreased activity of DA neurons was associated with reduced motivation for natural rewards, consistent with anhedonia-like behavior. Selective activation of VTA DA neurons was sufficient to restore baseline motivation and hedonic responses to natural rewards. These findings reveal pain-induced adaptations within VTA DA neurons that underlie anhedonia-like behavior.

An endogenous opioid circuit determines state-dependent reward consumption

µ-Opioid peptide receptor (MOPR) stimulation alters respiration, analgesia and reward behaviour, and can induce substance abuse and overdose1-3. Despite its evident importance, the endogenous mechanisms for MOPR regulation of consummatory behaviour have remained unknown4. Here we report that endogenous MOPR regulation of reward consumption in mice acts through a specific dorsal raphe to nucleus accumbens projection. MOPR-mediated inhibition of raphe terminals is necessary and sufficient to determine consummatory response, while select enkephalin-containing nucleus accumbens ensembles are engaged prior to reward consumption, suggesting that local enkephalin release is the source of the endogenous MOPR ligand. Selective modulation of nucleus accumbens enkephalin neurons and CRISPR-Cas9-mediated disruption of enkephalin substantiate this finding. These results isolate a fundamental endogenous opioid circuit for state-dependent consumptive behaviour and suggest alternative mechanisms for opiate modulation of reward.

Extended amygdala-parabrachial circuits alter threat assessment and regulate feeding

An animal's evolutionary success depends on the ability to seek and consume foods while avoiding environmental threats. However, how evolutionarily conserved threat detection circuits modulate feeding is unknown. In mammals, feeding and threat assessment are strongly influenced by the parabrachial nucleus (PBN), a structure that responds to threats and inhibits feeding. Here, we report that the PBN receives dense inputs from two discrete neuronal populations in the bed nucleus of the stria terminalis (BNST), an extended amygdala structure that encodes affective information. Using a series of complementary approaches, we identify opposing BNST-PBN circuits that modulate neuropeptide-expressing PBN neurons to control feeding and affective states. These previously unrecognized neural circuits thus serve as potential nodes of neural circuitry critical for the integration of threat information with the intrinsic drive to feed.

The ELFIN Mission

The Electron Loss and Fields Investigation with a Spatio-Temporal Ambiguity-Resolving option (ELFIN-STAR, or heretoforth simply: ELFIN) mission comprises two identical 3-Unit (3U) CubeSats on a polar (∼93^∘ inclination), nearly circular, low-Earth (∼450 km altitude) orbit. Launched on September 15, 2018, ELFIN is expected to have a >2.5 year lifetime. Its primary science objective is to resolve the mechanism of storm-time relativistic electron precipitation, for which electromagnetic ion cyclotron (EMIC) waves are a prime candidate. From its ionospheric vantage point, ELFIN uses its unique pitch-angle-resolving capability to determine whether measured relativistic electron pitch-angle and energy spectra within the loss cone bear the characteristic signatures of scattering by EMIC waves or whether such scattering may be due to other processes. Pairing identical ELFIN satellites with slowly-variable along-track separation allows disambiguation of spatial and temporal evolution of the precipitation over minutes-to-tens-of-minutes timescales, faster than the orbit period of a single low-altitude satellite (T_orbit ∼ 90 min). Each satellite carries an energetic particle detector for electrons (EPDE) that measures 50 keV to 5 MeV electrons with Δ E/E < 40% and a fluxgate magnetometer (FGM) on a ∼72 cm boom that measures magnetic field waves (e.g., EMIC waves) in the range from DC to 5 Hz Nyquist (nominally) with <0.3 nT/sqrt(Hz) noise at 1 Hz. The spinning satellites (T_spin ∼ 3 s) are equipped with magnetorquers (air coils) that permit spin-up or -down and reorientation maneuvers. Using those, the spin axis is placed normal to the orbit plane (nominally), allowing full pitch-angle resolution twice per spin. An energetic particle detector for ions (EPDI) measures 250 keV - 5 MeV ions, addressing secondary science. Funded initially by CalSpace and the University Nanosat Program, ELFIN was selected for flight with joint support from NSF and NASA between 2014 and 2018 and launched by the ELaNa XVIII program on a Delta II rocket (with IceSatII as the primary). Mission operations are currently funded by NASA. Working under experienced UCLA mentors, with advice from The Aerospace Corporation and NASA personnel, more than 250 undergraduates have matured the ELFIN implementation strategy; developed the instruments, satellite, and ground systems and operate the two satellites. ELFIN's already high potential for cutting-edge science return is compounded by concurrent equatorial Heliophysics missions (THEMIS, Arase, Van Allen Probes, MMS) and ground stations. ELFIN's integrated data analysis approach, rapid dissemination strategies via the SPace Environment Data Analysis System (SPEDAS), and data coordination with the Heliophysics/Geospace System Observatory (H/GSO) optimize science yield, enabling the widest community benefits. Several storm-time events have already been captured and are presented herein to demonstrate ELFIN's data analysis methods and potential. These form the basis of on-going studies to resolve the primary mission science objective. Broad energy precipitation events, precipitation bands, and microbursts, clearly seen both at dawn and dusk, extend from tens of keV to >1 MeV. This broad energy range of precipitation indicates that multiple waves are providing scattering concurrently. Many observed events show significant backscattered fluxes, which in the past were hard to resolve by equatorial spacecraft or non-pitch-angle-resolving ionospheric missions. These observations suggest that the ionosphere plays a significant role in modifying magnetospheric electron fluxes and wave-particle interactions. Routine data captures starting in February 2020 and lasting for at least another year, approximately the remainder of the mission lifetime, are expected to provide a very rich dataset to address questions even beyond the primary mission science objective.

A Paranigral VTA Nociceptin Circuit that Constrains Motivation for Reward

Nociceptin and its receptor are widely distributed throughout the brain in regions associated with reward behavior, yet how and when they act is unknown. Here, we dissected the role of a nociceptin peptide circuit in reward seeking. We generated a prepronociceptin (Pnoc)-Cre mouse line that revealed a unique subpopulation of paranigral ventral tegmental area (pnVTA) neurons enriched in prepronociceptin. Fiber photometry recordings during progressive ratio operant behavior revealed pnVTAPnoc neurons become most active when mice stop seeking natural rewards. Selective pnVTAPnoc neuron ablation, inhibition, and conditional VTA nociceptin receptor (NOPR) deletion increased operant responding, revealing that the pnVTAPnoc nucleus and VTA NOPR signaling are necessary for regulating reward motivation. Additionally, optogenetic and chemogenetic activation of this pnVTAPnoc nucleus caused avoidance and decreased motivation for rewards. These findings provide insight into neuromodulatory circuits that regulate motivated behaviors through identification of a previously unknown neuropeptide-containing pnVTA nucleus that limits motivation for rewards.

Epidemic typhus infection in cynomolgus monkeys (Macaca fascicularis)

A nonhuman primate model of clinical Rickettsia prowazekii infections was developed in cynomolgus monkeys (Macaca fascicularis). Monkeys infected intravenously with 10(7) plaque-forming units developed clinical signs of illness and pathological changes characteristic of epidemic typhus infection in humans. Increases in total leukocyte counts, serum alkaline phosphatase, blood urea nitrogen, and serum glutamic pyruvate transaminase values were observed. Microscopic examination revealed typical typhus nodules in the brains of two monkeys that died. These data indicated that the cynomolgus monkey is a suitable model for study of the pathogenesis of epidemic typhus infection and may prove valuable in the evaluation of candidate R. prowazekii vaccines.

Immune responses to Rickettsia akari infection in congenitally athymic nude mice

Athymic BALB/c nude mice and euthymic BALB/c mice were infected with Rickettsia akari by the intraperitoneal route. The rickettsialpox infection was terminated in euthymic mice with only two intraperitoneal injections of the antibiotic oxytetracycline, whereas prolonged treatment was necessary to terminate the infection in athymic mice. Both athymic and euthymic mice produced specific antibody, but athymic mice were still susceptible to reinfection. Killed R. akari served as a protective immunogen in euthymic, but no in athymic, mice. When spleen cells from convalescent euthymic mice were transferred to syngeneic athymic mice, recipients showed protection against challenge. This suggests that a T-cell-dependent step is generally necessary to terminate the rickettsialpox infection.

Evaluation of a killed Rocky Mountain spotted fever vaccine in cynomolgus monkeys

A nonhuman primate model of Rocky Mountain spotted fever infection was developed in cynomolgus monkeys (Macaca fascicularis) infected by the subcutaneous route or by aerosol. Clinical responses, hematology and serum chemistry values, and pathological findings were similar to those found in humans ill with Rocky Mountain spotted fever. The clinical model was then used to test the efficacy of a killed Rocky Mountain spotted fever vaccine grown in chicken embryo cells. Monkeys were immunized with varying dilutions of the vaccine with a two-dose schedule and then challenged at 2 months with virulent Rickettsia rickettsii by the subcutaneous route or by aerosol. The undiluted vaccine totally protected monkeys against both challenges, even at extremely high doses.

Breast gross cystic disease fluid analysis. I. Isolation and radioimmunoassay for a major component protein

Human breast gross cystic disease (GCD) fluid was analyzed by sodium dodecyl sulfate-acrylamide gel electrophoresis, and four major proteins (GCDFP-70), GCDFP-44, GCDFP-24, and GCDFP-15) were identified. By fractionation techniques, these proteins were separated from one another. The GCDFP-70 was immunologically identical to human albumin and was present in GCD fluid at approximately a 100-fold lower concentration than in plasma. The GCDFP-44 was immunologically identical to human plasma Zn-alpha2-glycoprotein; however, it was present in GCD fluid at an approximately 50-fold higher concentration than in plasma. The GCDFP-24 was the major component protein of GCD fluid. It had progesterone binding activity, and immunologically it was identical to a component of human plasma; however, antisera that identified 30 separate components of plasma failed to identify the GCDFP-24 as one of these plasma proteins. The GCDFP-24 concentration in GCD fluid was approximately 100-fold higher than the plasma analog. The GCDFP-15 component was immunologically distinct from any plasma components, as judged by Ouchterlony analysis. It was, however, immunologically identical with a component of both human milk and saliva. As revealed by radioimmunoassay, plasma levels in normal subjects were 7-85 ng/ml. In patients with metastatic breast carcinoma, markedly plasma levels (150-30,000 ng/ml) of this protein were detected. Short-term tissue cultures of breast carcinoma explants released this protein into the culture medium.

Cynomolgus monkey model for experimental Q fever infection

A subhuman primate model was developed for study of the pathogenesis of infection with Coxiella burnetii. Cynomolgus monkeys (Macaca fascicularis) that were exposed to 10(5) mouse median infectious intraperitoneal doses of C. burnetii in a small-particle aerosol developed clinical signs of illness and pathologic changes characteristic of Q fever infection in humans. All monkeys had radiologic evidence of pneumonia by day 9. Antibodies to C. burnetii were detectable by the indirect fluorescent antibody test by day 7. These data indicate that the cynomolgus monkey is a suitable model for study of the pathogenesis of Q fever infection and may prove valuable in the evaluation of C. burnetii vaccines.

Suppression of cellular immune responses in guinea pigs infected with spotted fever group rickettsiae

Using a guinea pig model, we demonstrated that infections with pathogenic species of spotted fever group rickettsiae transiently and nonspecifically suppress established cellular immune responses as measured by in vitro lymphocyte transformation and in vivo delayed cutaneous hypersensitivity responses to unrelated, nonrickettsial antigens. The correlation of the duration of this immunosuppression with the virulence of the infecting rickettsial species suggests that this suppression is a pathological effect of the rickettsial infection. Although we did not specifically study the mechanism of this suppression, it is not associated with either lymphocytopenia or leukocytosis.

Enhancement of the immunogenicity of phase I antigen of Coxiella burnetii

The immunogenicity of the soluble phase I antigen of Coxiella burnetii for guinea pigs was enhanced by a nuclease-resistant complex of polyriboinosinic-polyribocytidylic acid, poly-L-lysine, and carboxymethyl cellulose.

Initial clinical evaluation of a new Rocky Mountain spotted fever vaccine of tissue culture origin

Currently available Rocky Mountain spotted fever (RMSF) vaccines are relatively ineffective in preventing infections in humans and contain considerable amounts of contaminating egg protein. A new formalin-inactivated vaccine was prepared by sucrose density gradient centrifugation of the Sheila Smith strain of Rickettsia rickettsii grown in chick embryo cell tissue culture. The new product has greater protective immunogenicity in rheusus monkeys and guinea pigs than commercial vaccines. Six volunteers without immunologic evidence of prior exposure to RMSF received from one to three inoculations of the vaccine diluted 1:10, and there were two benign local reactions. Titers of antibody (determined by microagglutination and indirect fluorescence techniques) increased in all recipients as did lymphocyte tranformation responses to specific rickettsial antigen. Ten volunteers were immunized twice with vaccine diluted 1:3; there were no local reactions, and immunologic responses were similar to those in the six volunteers in the first group. The proper dosage and immunization schedule for the vaccine must be determined in further studies.

Prophylactic treatment of Rocky Mountain spotted fever

Prophylactic treatment of Rocky Mountain spotted fever with a single dose of oxytetracycline was investigated in guinea pigs. Disease was prevented when treatment was administered shortly before expected onset. Relapses occurred when treatment preceded expected onset by 48 h or more.

Alterations of body fluid compartments and distribution of tissue water and electrolytes in rhesus monkeys with rocky mountain spotted fever

Chair-restrained rhesus monkeys (Macaca mulatta) were inoculated subcutaneously with 10(2)--10(3) plaque-forming units of virulent Rickettsia rickettsii. The latent period for fever and rickettsemia was three to four days; death occurred six to eight days after infection. Total circulatory electrolyte levels and fluid volumes, including plasma, red blood cell, true circulatory blood, and extracellular fluid, increased. The expansion of the extracellular and plasma volumes resembled findings reported during severe Rocky Mountain spotted fever in humans, guinea pigs, and rabbits. Total water content of the liver also increased. Intracellular concentrations of K+, as well as total Na+ and K+, decreased in the diaphragm. Both the lung and medulla oblongata showed increased levels of intracellular Na+ and water with simultaneously decreased levels of extracellular Na+ and water. Such an intracellular overhydration of the medulla oblongata could contribute to death as a result of depression of the cardiovascular and respiratory centers. On the basis of the findings in monkeys, the intravenous infusion of fluids and electrolytes during clinical therapy of severe rickettsial infections should be considered extremely dangerous.

Plaque formation by strains of spotted fever rickettsiae in monolayer cultures of various cell types

Some strains of spotted fever rickettsiae could be distinguished by their ability or inability to form plaques in monolayer cultures of various mammalian and avian cell types.

Cell-mediated immune responses of guinea pigs to an inactivated phase I Coxiella burnetii vaccine

The ability of a killed phase I Coxiella burnetii vaccine to induce cell-mediated immune responses in guinea pigs was studied. Cell-mediated immune responses were assessed by the inhibition of macrophage migration and lymphocyte transformation assays. The macrophage migration response occurred rapidly and was detected at high levels, but was relatively short-lived. In contrast, the lymphocyte transformation response developed more slowly, and persisted for a longer period. The vaccine, given in a single dose or in two doses 1 week apart, protected guinea pigs from a subsequent virulent challenge.

In vitro guinea pig leukocyte reactions to Rickettsia rickettsii

The presence of cell-mediated immunity in Rocky Mountain spotted fever-infected guinea pigs was determined by two in vitro assays: whole blood lymphocyte transformation (LT) and macrophage migration inhibition. Increased LT was detected as early as 1 week in guinea pigs infected with Rickettsia rickettsii and treated with oxytetracycline and was detected by two weeks in infected but untreated guinea pigs. Elevated LT was still detectable at 10 weeks postinfection. Guinea pigs vaccinated with killed rickettsiae failed to develop lymphocyte responsiveness; however, there was a rapid lymphocyte response after challenge with live organisms, suggesting potentiation by the vaccine. Vaccinated guinea pigs that were challenged and then treated with antibiotic failed to develop LT, suggesting that infection is necessary for the observed response. Macrophage migration inhibition was detected in both infected and vaccinated guinea pigs by 1 week after infection, but this response was no longer detected 4 to 5 weeks later. Antibody appeared at 2 to 3 weeks postinfection and was present at low levels through week 10. Antibody-treated rickettsiae were phagocytized and destroyed by guinea pig peritoneal macrophages, whereas normal serum-treated rickettsiae replicated and eventually destroyed the phagocytes.

Laboratory-acquired Rocky Mountain spotted fever. The hazard of aerosol transmission

Nine patients with laboratory-acquired Rocky Mountain spotted fever were seen during the period 1971 to 1976. Investigation of each case revealed either definite or probable exposure to an aerosol containing infectious rickettsiae; in no case was there evidence of parenteral exposure either by accidental self-inoculation or by tick bite. These illnesses are believed to represent infection acquired via the respiratory route. This report emphasizes the aerosol hazard of Rickettsia rickettsii in the laboratory and discusses the possibility of respiratory transmission of Rocky Mountain spotted fever in nature. The illness occurred only in personnel who had received either no vaccination or the primary series of the commercial (Lederie) vaccine against this infection. Other personnel who had received the primary series with multiple booster vaccinations demonstrated increased immunity as measured by humoral antibody titers and rickettsial antigen-induced lymphocyte transformation; no cases of clinical disease developed in these multiply-vaccinated personnel.

Lesions in guinea pigs infected with Coxiella burnetii strain M-44

Guinea pigs inoculated with the live M-44 vaccine strain of Coxiella burnetii were examined grossly and microscopically for the presence of Q fever-related lesions. Mild myocarditis was observed in 38% of the infected animals but in none of the control animals. Livers showed significant incidence of hepatitis, necrosis, and granuloma formation, especially during the first eight days of the infection. A much lower incidence of splenitis was also found but was considered to be of borderline significance. Generally, lesions were mild in nature, and none seemed to endanger the life of the animal or to cause observable distress.

Studies on Macaca mulatta infected with Rocky Mountain spotted fever

Acid-base alterations and changes in other selected serum constituents (free fatty acids, triglycerides, cholesterol, copper, cortisol, alpha1-acid glycoprotein, haptoglobin, and albumin) were measured during a study of Rocky Mountain spotted fever in 16 male rhesus macaques. Blood samples were taken from nonanesthetized macaques conditioned to repeated handling. Arterial pH increased and PCO2 decreased during the febrile period. Free fatty acids, triglycerides, copper, cortisol, alpha1-acid glycoprotein, and haptoglobin increased, whereas albumin decreased during the disease. Significant changes were not observed in arterial PO2. Cholesterol remained unchanged. The increase in arterial pH and decrease in PaCO2 indicated that respiratory alkalosis was present in macaques acutely affected with Rocky Mountain spotted fever.

Scanning and transmission electron microscopy of Rickettsia rickettsii propagated in cell culture

Scanning electron microscopy utilizing critical-point drying and transmission electron microscopy employing air-dried agar pseudoreplicas and critical-point dried carbon replicas were used to study the surface of Rickettsia rickettsii propagated in cell culture.

Susceptibility of laboratory animals to infection by spotted fever group rickettsiae

An attempt was made to find a suitable animal model for studies of spotted fever group rickettsiae. Inbred and outbred mice, the guinea pig, ferret, gerbil, hamster, wild rabbit, cotton rat, sheep, and miniature swine were tested. Of these, only certain strains of the mouse [Mai:(S) and BALB/cJ] and the guinea pig [Hla:(HA)] exhibited, overtly, the desired characteristics of disease. Other laboratory animals (such as sheep or rabbits) can be used for the production of antiserum against the spotted fever group of rickettsiae; however, these rickettsiae apparently have little or no effect on several other animal species. The lack of overt disease might explain the role of these animals or related genera as reservoirs for the tick-borne spotted fever rickettsiae.

Differences in buoyant-density properties of Coxiella burnetii and Rickettsia rickettsii

The pronounced change in the buoyant density of Coxiella burnetii in CsCl gradients that was caused by treatment with formalin or ultraviolet radiation was not observed with Rickettsia rickettsii.

Effect of vaccination schedule on immune response of Macaca mulatta to cell culture-grown Rocky Mountain spotted fever vaccine

The effect of vaccination schedule on the immune response of Macaca mulatta to formalin-inactivated chicken embryo cell culture (CEC)-grown Rickettsia rickettsii vaccine was studied. Schedules consisted of inoculation on day 1 only, on days 1 and 15, on days 1 and 30, on days 1, 8, and 15, or on days 1, 15, and 45. Humoral antibody measured by microagglutination and indirect immunofluorescence and resistance to challenge with 10(4) plaque-forming units of yolk sac-grown R. rickettsii were assessed. Seroconversion was noted in all monkeys after the first dose of vaccine. A second dose administered 8 or 15 days after the primary infection, or a third given 7 or 30 days after the second, produced no long-term effect on antibody titer. Only monkeys given two doses of vaccine at a 30-day interval showed an increase in antibody titer during the period before challenge. Vaccination with one, two, or three doses of CEC vaccine prevented development of rash and rickettsemia after challenge. The two-dose schedules appeared to induce the highest degree of resistance to challenge, as indicated by unaltered hematological parameters and body temperature in monkeys. The one- and three-dose schedules were somewhat less effective, in that some challenged monkeys within each group displayed febrile and leukocyte responses associated with Rocky Mountain spotted fever infection. Our data suggest that administration of two doses of CEC vaccine at 15- or 30-day intervals is the immunization schedule of choice.

Prompt confirmation of Rocky Mountain spotted fever: identification of rickettsiae in skin tissues

Rickettsia rickettsii were identifiable by the immunofluorescence technique in skin specimens obtained by biopsy on days 4 and 8 of illness from patients with Rocky Mountain spotted fever. The immunofluorescence technique is regarded as a practical means of confirming the diagnosis during the early stages of illness before positive serologic reactions can be obtained.

Changes in blood serum constituents and hematologic values in Macaca mulatta with Rocky Mountain spotted fever

Forty-seven male Macaca mulatta, 3 to 4 kg weight, were inoculated intravenously or subcutaneously with various doses of yolk sac-grown Rickettsia rickettsii. Thirty-four macaques became febrile and exhibited signs of infection ranging from transient illness with a few days of fever to severe illness with subsequent death. The rash appeared more frequently in the macaques inoculated subcutaneously. Febrile macaques that survived had leukocytosis, with concomitant neutrophilia. Febrile macaques that died had, in addition, marked terminal leukopenia and thrombocytopenia. Packed cell volume of all febrile macaques decreased. In almost all of the febrile macaques, there were increased serum urea nitrogen, glutamic-oxaloacetic transaminase, and lactate dehydrogenase and decreased total serum protein and amylase concentrations. A few febrile macaques had increased bilirubin values and decreased sodium, chloride, phosphorus, and alkaline phosphatase concentrations. Changes did not occur in serum glucose, potassium, calcium, and glutamic-pyruvic transaminase values. The experimental form of Rocky Mountain spotted fever in the macaque provides a subhuman primate model for studying the pathophysiology of this disease.

Antibody response to Rocky Mountain spotted fever

Various techniques were compared to determine the most sensitive method for detection of rocky Mountain spotted fever antibody. A radiometabolic technique for detection of Rocky Mountain spotted fever antibody is also described. In infected monkeys, the fluorescent antibody technique yielded the earliest evidence of seroconversion; with some monkeys the microagglutination procedure was equally effective. The fluorescent antibody and microagglutination measurements showed higher titers than those for complement fixation, Weil-Felix, or the radiometabolic techniques.

Improved method for production of attenuated Venezuelan equine encephalomyelitis (TC-83 strain) vaccine

Primary chicken embryo cell cultures were evaluated a s an alternate cell system for the production of attenuated Venezuelan equine encephalomyelitis (TC-83 strain) vaccine. The TC-83 strain virus was shown to remain stable during 10 serial passages in chicken embryo cell culture with regard to plaque size and morphology, virus yield, potency, and virulence for mice and hamsters.

Biological properties of the M-44 strain of Coxiella burneti

The attenuated M-44 strain of Coxiella burneti was investigated for biological characteristics affecting its use as a live vaccine. After 25 serial passages in guinea pigs, the strain did not develop phase I properties detectable by the microagglutination test. Infectious organisms were not detected in untreated guinea pigs later than 12 weeks after inoculation; however, infection could be reactivated at later times by the production of stress (by pregnancy or drug treatment) in guinea pigs that had recovered. Evidence of reactivated infection was observed in recovered pregnant animals just before parturition at 46 weeks after infection, in methyl prednisolone-treated animals at 56 weeks, and in cyclophosphamide-treated guinea pigs at 96 weeks. A low rate of intercage and intracage infection was recorded.

Preparation and testing of vaccines prepared from the envelopes of Venezuelan, eastern, and western equine encephalomyelitis viruses

Envelope components were separated from Venezuelan, Eastern, and Western equine encephalomyelitis viruses after treatment of the virions with detergent. Vaccines prepared from the envelope component were capable of stimulating mice to produce humoral antibodies. Protective efficacy studies were performed using mono-, di-, and trivalent vaccine combinations. These elicited varying degrees of homologous protection, and Eastern and Venezuelan equine encephalomyelitis envelope products appeared to confer protection to mice challenged with Western equine encephalomyelitis virus.

Comparison of three rocky mountain spotted fever vaccines

Growth of Rocky Mountain spotted fever (RMSF) rickettsiae in duck embryo cell (DEC) cultures and chicken embryo cell (CEC) cultures was evaluated. Experimental lots of duck embryo cell- and chicken embryo cell-grown Rocky Mountain spotted fever vaccines and a commercial lot of yolk sac-grown vaccine were compared for protective efficacy in rhesus monkeys. Incidence and magnitude of antibody response, febrile response, and rickettsemia, as well as incidence of fatalities, suggested that both cell culture-derived vaccines were more immunogenic than the yolk sac-grown vaccine.

Demonstration of Rickettsia rickettsii in the rhesus monkey by immune fluorescence microscopy

Indirect immune fluorescence was used to detect rickettsiae in the tissues of a primate inoculated subcutaneously with Rickettsia rickettsii. Rickettsiae were identified by indirect immuno fluorescence predominantly in skin, skeletal muscle, scrotum, testicles, nares, heart, kidney, liver, brain, spleen, pancreas, and larynx. Cell culture assay confirmed the presence of infectious organisms in those specimens.

Changes in buoyant density relationships of two cell types of Coxiella burneti phase I

Coxiella burneti phase I, purified from a formalin-inactivated yolk-sac vaccine, was separated into two bands of morphologically distinct cell types when subjected to sucrose gradient centrifugation. Recycling of the less dense, rod-shaped cells in unbuffered sucrose gradients (pH 5.5 to 6.0) resulted in the formation of bands having the location and appearance of the original two bands. Recycling of the denser band of larger ovoid-shaped cells yielded a single band, suggesting that the larger cell type arose from the smaller cell. In contrast to vaccine-derived rickettsiae, live, cell culture-propagated phase I organisms formed a single band in unbuffered sucrose gradients, at the same density as the upper band of the vaccine preparation. Centrifugation of cell culture-derived rickettsiae for 26 to 48 h in sucrose gradients of pH 5.5 resulted in the formation of a second band, at the same density as the lower band of the vaccine preparation. This did not occur in gradients of pH 7.0. Treatment of cell culture-propagated rickettsiae with formalin or germicidal ultraviolet radiation induced a total shift of the less dense cell population to a zone of higher density when centrifuged isopycnically in CsC1 gradients. This density change did not occur in sucrose gradients, suggesting a difference in the effect of these treatments on the permeability of the cell membrane to sucrose and CsC1.

Paramagnetic spin label interactions with the envelope of a group A arbovirus. Lipid organization

Electron paramagnetic resonance observations were made on nitroxide spin- labeled molecules which were bound to the TC-83 vaccine strain of Venezuelan equine-encephalomyelitis virus. Paramagnetic resonance parameters derived from the observations and their dependence on sample temperature were similar but not identical to those which have been reported for these labels dissolved in lipid bilayer membranes of mammalian and bacterial origin. The data has a mechanical rigidity substantially greater than that of bilayers in cellular membranes. A model is presented which assumes the location of the lipid bilayer outside the nucleoprotein capsid and inside a spherical layer of envelope proteins. The model is in accord with Harrison's X-ray diffraction results for Sindbis virus. The model is discussed in terms of its implications with respects to the role played by lipid in viral maturation and infectivity.

Preparation of Rocky Mountain spotted fever vaccine suitable for human immunization

Rocky Mountain spotted fever vaccine was produced from rickettsiae grown in chicken embryo cells in roller bottle cultures. The rickettsiae were concentrated and purified by passage through a sucrose gradient and inactivated with formalin. This vaccine satisfactorily passed preinactivation and final container testing and is believed to be superior to the presently available yolk sac vaccine.

Comparative analyses of members of the Venezuelan equine encephalomyelitis virus complex

Polyacrylamide gel electrophoretic examination of viruses selected from the Venezuelan equine encephalomyelitis (VEE) complex revealed distinct strain to strain differences in profiles of the two virion envelope proteins. The core protein was identical in all viruses tested. We detected five electrophoretic patterns into which the virus strains could be classified and these were designated alpha (alpha), beta (beta), gamma (gamma), delta (delta), and episolon (episolon). Isolates representing variant E of subtype I exhibited a profile characterized by only one apparent envelope band. The epizootic subtypes I-A, I-B, I-C and the sylvatic subtype II viruses contained at least two envelope proteins which differed in molecular weight according to virus strain but which were not necessarily specific for antigenic variety. These results generally, though not uniformly, support the serologic classification of the VEE virus complex and suggested that the usefulness of the classification scheme could be complemented by the inclusion of biochemical criteria.

A microprecipitation test for rapid detection and identification of Venezuelan, eastern and western equine encephalomyelitis viruses

The development of a new diagnostic procedure for the identification of Venezvelan, eastern and western equine encephalomyelitis (VEE, EEE, WEE) viruses is described. The procedure utilizes virus precipitation with reference fluorescein-conjugated gamma globulin, followed by cellulose acetate electrophoresis. Clinical specimens containing varying concentrations of virus yielded, in primary duck embryo cell culture, sufficient virus for detection within 22 to 44 hours. Identification of VEE, EEE and WEE virus in specimens was accomplished by microprecipitation within this time. In contrast to conventional identification methods, our procedure eliminates the cost of utilizing laboratory animals and considerably reduces the time required for virus identification.

Separation, isolation, and immunological studies of the structural proteins of Venezuelan equine encephalomyelitis virus

Three viral proteins were separated from the TC-83 strain of Venezuelan equine encephalomyelitis virus by discontinuous polyacrylamide gel electrophoresis after disruption with sodium dodecyl sulfate and beta-2-mercaptoethanol. These proteins were inoculated into rabbits and the resultant antisera were tested for immunological activity by gel precipitation, plaque reduction neutralization, hemagglutination inhibition (HI), complement fixation, fluorescence microscopy, and mouse protection studies. All proteins were capable of stimulating precipitating antibody in rabbits, but the largest protein (VP 1), which is contained in the envelope, stimulated the production of detectable neutralizing and HI antibody against the intact virion. The other two proteins yielded little or no neutralizing or HI antibody.

Effects of antigen-antibody complexes on the primary immune response in Rhesus monkeys

A model for the enhancement of the primary humoral immune response of rhesus monkeys to marginal or weakly antigenic vaccines is presented. Our procedure used the complexing of formalin-inactivated Venezuelan equine encephalomyelitis (VEE) virus vaccine with specific, homologous, immune gamma globulin (IgG) at equivalence. Equivalence was determined by combining the concentrated, isotopically labeled ((3)H) virus with various concentrations of specific Sephadex-fractionated IgG. Enhancement of VEE virus antibody response in monkeys was obtained from preparations containing a marginal concentration of antigen that was complexed at equivalence with homologous IgG as compared with antigen alone. Protection in Swiss mice closely paralleled the antibody response pattern observed in monkeys, since complexes at equivalence provided 30 to 50% greater protection against challenge than antigen alone.

Immunological studies on the envelope component of Venezuelan equine encephalomyelitis virus

Treatment of purified Venezuelan equine encephalomyelitis virus with the nonionic detergent Triton X-100 permitted spearation of the envelope from the core component. The isolated envelope was a noninfectious immunogen which reacted in hemagglutination, hemagglutination inhibition, complement fixation, and neutralization serological reactions.

Comparative studies of plaque variantes derived from a Florida strain of Venezuelan equine encephlomyelitis virus

Small- and large-plaque variants of a Florida strain (Fe 3-7c) of Venezuelan equine encephalomyelitis virus were studied in vivo and in vitro. The small-plaque variant was less virulent in mice, hamsters, and guinea pigs than the large-plaque variant. The variants could be distinguished by calcium phosphate chromatography. The implications of plaque variants within a mixed virus population are discussed.