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Bovine paraplegic syndrome (BPS) is a debilitating cattle disease of unknown origin that is characterized by leukocytosis, lymphocytopenia and monocytopenia. The major clinical signs are difficulties in locomotion affecting hind limbs, hypoalgesia in the hind quarters, posterior paralysis and death within 72 to 96 hours after recumbency. To investigate the aetiological basis of BPS, we examined a possible association of the syndrome with infection by bovine immunodeficiency virus (BIV), a lentivirus implicated in immune system dysfunction and central nervous system lesions in cattle. Serum samples (n = 1,278) were collected from both healthy and BPS-prevalent cattle herds in Venezuela, and organ extracts were prepared from euthanized animals (n = 11) suspected of having BPS. Sera were analysed for reactivity to recombinant BIV and bovine leukaemia virus gag precursor proteins by immunoblot procedures. Serum reactivity to BIV ranged from 12 to 66% between groups of BPS prevalent herds. The percentage of samples reactive to BLV antigen was much lower (2 to 17%). Rabbits inoculated with extracts from BPS-afflicted animals exhibited an anamnestic immune response to BIV antigens as well as the presence of BIV gag antigens in their tissues. We present evidence for a possible association between BPS disease and a viral agent related to BIV. The role of BIV, in combination with malnutrition, in BPS is discussed.

To investigate the effect of bovine immunodeficiency virus (BIV) infection on the rabbit immune system, we studied the proliferative responses of peripheral blood lymphocytes (PBLs) of rabbits experimentally inoculated with BIV. All BIV127-inoculated rabbits seroconverted after 6 weeks and remained seropositive over a prolonged period of time. Assays for specific lymphocyte reactivity to concanavalin A (Con A) were performed monthly for over 1 year. One-hundred percent of infected rabbits developed abnormally low T cell responses, as measured by Con A stimulation. By 3 months postinoculation, the PBL response to Con A was diminished and remained depressed for 6 months. All animals were clinically asymptomatic within 14 months of BIV inoculation. By 15 and 16 months postinoculation, two of three infected rabbits exhibited recurrent lowering of the T cell responsiveness including a decrease in absolute PBL counts. One of these animals died unexpectedly. Our results further confirmed that a functional impairment of lymphocytes was induced early in the course of BIV infection, prior to clinical disease. These findings suggested that BIV infection may mimic asymptomatic infection of human immunodeficiency virus (HIV) and provided further evidence of the importance of BIV-induced disease in rabbits as a relevant model for the study of AIDS.

More than 100 plant extracts from the Amazonian rain forest of Venezuela were evaluated for their cytotoxicity and inhibitory activity against the human immunodeficiency virus type-1 (HIV-1). Aqueous extracts from Fomitella supina (S # 0389-4), Phellinus rhabarbarinus (S # 0389-7), Trichaptum perrottetti (S # 0389-8) and Trametes cubensis (S # 0389-13), Polyporaceae exhibited strong anti-HIV-1 activity, without toxicity for Molt-4 lymphocytic cells. Our results demonstrated, that the compound(s) acted by mechanism of direct virion inactivation and by inhibition of syncytium formation in an in vitro culture system. These results support the suggestion that the test extracts specifically act at the level of CD4-gp120 binding. The active components of these extracts is at present unknown, but anti-AIDS agents, such as those found in this study, individually or in combination, may be of therapeutic relevance.

Fourteen strains of VEEV of diverse origin and antigenicity were classified into five virulence categories according to their efficiency of infection and nature of response in mice. Mice of ages up to 30 days represented distinct levels of responsiveness and were suitable for the differentiation of VEEV strains of highest to lowest virulence. Stepwise changes with age of the susceptibility or responsiveness of mice appeared to determined the type of response as predominantly lethal (D), dual or intermediate (DP) or protective (P).

Granulomas are chronic, usually focal, tissue-destructive inflammatory reactions that usually form around slowly degradable, poorly soluble substances. They are dynamic lesions, regulated by complex immune mechanisms. Tachykinins are a family of neuropeptides characterized by the common C-terminal amino acid sequence -Phe-X-Gly-Leu-Met-NH2. One such tachykinin, substance P, has been reported to modulate immunologic responses. In this investigation, granulomas were examined for substance P. Granulomas were isolated from the livers of mice infected with murine schistosomiasis, and substance P was extracted. Immunoreactive substance P was detected by RIA. The authenticity of the molecule was confirmed by elution profile on HPLC. Immunoreactive substance P, identified by immunostaining, localized to eosinophils derived from collagenase-dispersed granulomas. Granulomas were then probed for expression of the gene for substance P (preprotachykinin). Preprotachykinin mRNA was localized to granuloma eosinophils by in situ oligonucleotide hybridization. It is concluded that substance P is present within the granuloma as a result of preprotachykinin production by eosinophils.

Mice of different ages were infected i.p. or i.c. by 23 different strains of VEE virus. The course of the virus host interaction was specified in terms of the efficiency of infection, the outcome of infection as lethality or protection and the survival time. These separately quantifiable features all showed several host-maturation events that combine to provide a multifactorial specification of virus-strains and host-responses. This base-line for correlations with the responses of principal hosts (equidae and man) may be expanded to test correlations with the antigenic or in vitro characteristics of virus-strains.

A high frequency of Hepatitis-B antigen (7%) was found in apparently healthy Yanomama indians living in southern Venezuela. The prevalence in 24 different Yanomama villages varied between 0 and 30%, but only 3 of 938 serum samples showed presence of HB-Ab. The distribution of the HB-Ag was found to be significantly higher in males than in females.

Thermal inactivation of Venezuelan Equine Encephalomyelitis Virus (VEEV) was studied at temperatures from 26 degrees to 55 degrees C. Inactivation of infectivity took place by two thermodynamically different reactions, one of which predominated at temperatures below 44 degrees C and the other at higher temperatures. The presence of 1 or 2 M NaCl stabilized the VEE virus at low temperatures but enhanced the inactivation at high temperatures. This latter effect at temperatures higher than 50 degrees C, is associated with the occurrence of two-component survival curves. The different effects of hypertonic NaCl concentrations at the two ranges of temperature, are related to different mechanisms of inactivation operating at each range (protein denaturation and nucleic acid-RNA breakdown). Different kinetics of thermal inactivation at 55 degrees C were observed between virus strains with different virulence. However, no significant correlations was found between the virulence of the eleven VEE virus strains studied and their thermostability at 37 degres and 55 degrees C.

Increasing utilization of arable land in southwestern Venezuela has led to a potential increase in human exposure to arbovirus infections. Since previous studies in the Catatumbo region of this area documented the presence of eastern equine encephalitis (EEE) and Venezuelan equine encephalitis (VEE) viruses, an attempt was made to study the transmission and maintenance of these viruses from 1973 to 1981. Isolations of EEE, VEE ID strains, Una, Itaqui , and Moju viruses were repeatedly obtained from mosquitoes, mostly Culex ( Melanoconion ) spp. and sentinel hamsters. The results indicate that these viruses constitute a potential hazard to public health in the area. Further, the strategic location of the Catatumbo region, between enzootic tropical foci of arboviruses, may provide circumstances and conditions for study of both enzootic maintenance and movement of these viruses.

Representative strains of Venezuelan equine encephalitis virus (VEEV) and Eastern equine encephalitis virus (EEEV) were compared for their ability to grow in cultures of unstimulated leucocytes and monocytes derived from donkey peripheral blood. Replication of epizootic and vaccine strains of VEEV, but not of enzootic strains was observed in this system. Only a minority of monocytes supported virus replication as detected by immunofluorescence, electron microscopy and infectious center assays. EEEV did not appear to replicate in this cell system although virus attached to and was internalized by monocytes.

The purpose of this report is to describe isolations of Venezuelan (VEE) and Eastern (EEE) Equine Encephalitis virus made in the lowland moist tropical forest of the Catatumbo region on the southwestern part of the State of Zulia, Venezuela. We have isolated four strains of EEEV from sentinel hamsters exposed at Caño Mocho and Madre Vieja sites in 1973 and 1974, and three strains of EEEV in Hacienda (Hda.) Las Nubes in 1975. Both viruses were recovered during silent interepidemic periods and we believe these viruses are maintained in this region in sylvatic conditions. The recovered virus strains were detected within 24 to 48 hours, both in SMB and Vero Cell monolayer cultures and the sentinel hamsters yielded virus infectivities up to 10(4) PFU ml. Our VEEV isolate (IVIC PAn 23645-47), recovered during the silent interepizodemic period had an elution profile on the hydroxylapatite column corresponding to that of a I-D (VEEV-3880) or a I-E (VEEV-63A216) 'enzootic' subtype. However, considering other in vitro criteria (KHI; HA pH 5.8-6.0; small plaque size in Vero monolayers with suitable overlay media), this later and other previous isolates had some very distinct properties of the 'epizootic' strains. Thus, the evidence suggests that in Venezuela the VEEV cycle in nature is maintained either by the so called 'enzootic' and/or 'epizootic' virus types, or the virus population of the isolates have particular in vitro properties which do not correlate to the virulence markers in vivo. We consider this important question must be further clarified, and in addition, the isolation of three strains of EEEV are reported; this is the first report of the presence of this virus in Venezuela. Although the EEEV isolates may be of the South American type, they must be considered as potentially dangerous in the case of outbreaks.

Repeated outbreaks of Venezuelan equine encephalitis (VEE) in humans and equines in the Guajira region of Venezuela suggested a sylvatic focus of an epizootic subtype of VEE virus. A surveillance system was established, and virus isolations were attempted from 67,760 mosquitoes as well as sentinel hamsters. Sixteen isolates of eastern equine encephalitis (EEE) and a strain of Itaqui virus were recovered from mosquitoes, and 60 isolates of EEE, two of VEE, and two of Itaqui viruses were recovered from tissues of sentinel hamsters. The VEE virus isolates were shown to be closely related antigenically to prototype VEE ID and the EEE virus isolates were shown to be more closely related to the South American than the North American variety of EEE virus. Evidence for the presence of VEE and EEE viruses in small wild vertebrates was obtained from serologic testing. This study showed, for the first time, the enzootic presence of both VEE ID and EEE viruses during a nonepizoodemic period in the Guajira region.

Virulent and attenuated strains of yellow fever virus were compared for their ability to grow in cultures of unstimulated leucocytes and monocytes derived from human peripheral blood, and of a macrophage-like cell line of human origin, U937. The extent of virus growth in leucocyte cultures varied depending on the strain of virus, multiplicity of infection, presence of diluted antibody in the culture medium but independently of the flavivirus immune status of the donor. The same pattern of differential growth was observed in the three types of cultures used. Although strain related variation in growth occurred within both virulent and attenuated strains, most of the attenuated strains produced higher virus yields than the virulent ones, suggesting that replication in this cell system is not related to the expression of virulence for the host. Replication in human monocytes as an in vitro marker of immunogenity for substrains of 17 D vaccine virus is discussed.

Comparative analysis of structural virion polypeptides of 24 selected EEE virus strains, representing North and South American types, was performed by one-dimensional discontinuous sodium dodecyl sulfate (SDS)-polyacrylamide-gel electrophoresis (PAGE). The structural proteins of different EEE virus isolates, resolved by this method, exhibited mol.wts. values in the range of 57-60 X 10(3) for (E-1), 51-54 X 10(3) for (E-2) and 35-38 X 10(3) daltons for the core (NP) nucleocapsid. The exception was the South American human lethal virus, TRVL-89287 strain, which was shown to possess only a single envelope glycoprotein. The high molecular weight envelope (E-1) glycoprotein species was absent or co-migrated adjacent to the smaller envelope (E-2) glycoprotein. Results indicated similarities in the core (NP) proteins, however greater variability in the envelope (E-/ and/or E-2) glycoproteins. Based on these variations seven distinct profiles could be observed among the EEE virus strain studied. The classification based on the patterns of structural polypeptides obtained by SDS-PAGE of these strains does not correlate well with any other previously reported in vitro characteristics (antigenic subtypes, HTP elution profiles) nor with the in vivo virulence markers.