Study on the efficacy of Leptospira vaccines developed from serovars isolated from Trinidad and comparison with commercial vaccines using a hamster model

A hamster model was used to determine the efficacy of commercially prepared canine vaccines against Leptospira serovars circulating in Trinidad and to assess the effectiveness of killed whole-cell vaccines prepared from local isolates. The local isolates used for vaccine preparation and challenge were isolates of serovars Copenhageni and Mankarso obtained from a local dog and rodent. Their estimated lethal dose-50 (LD(50)) were 5 and 10 organisms, respectively and clinical signs observed on infection were consistent with leptospirosis. An unvaccinated control group of hamsters and other groups of hamsters that had been vaccinated with 3 doses of (i) in-house whole-cell Copenhageni vaccine, (ii) in-house whole-cell Mankarso vaccine, (iii) commercial vaccine Brand A or (iv) commercial vaccines Brand B were challenged with 1000 times the LD(50) of the respective challenge serovar. The most commonly used commercial vaccine (Brand A) did not offer protection to challenged hamsters, whereas Brand B facilitated the renal carrier state of the Leptospira organism. In contrast the whole-cell vaccines developed from local strains of serovars Copenhageni and Mankarso, protected all hamsters tested from both clinical disease and renal carrier states.

Recombinant sindbis/Venezuelan equine encephalitis virus is highly attenuated and immunogenic

Venezuelan equine encephalitis virus (VEEV) is an important, naturally emerging zoonotic virus. VEEV was a significant human and equine pathogen for much of the past century, and recent outbreaks in Venezuela and Colombia (1995), with about 100,000 human cases, indicate that this virus still poses a serious public health threat. The live attenuated TC-83 vaccine strain of VEEV was developed in the 1960s using a traditional approach of serial passaging in tissue culture of the virulent Trinidad donkey (TrD) strain. This vaccine presents several problems, including adverse, sometimes severe reactions in many human vaccinees. The TC-83 strain also retains residual murine virulence and is lethal for suckling mice after intracerebral (i.c.) or subcutaneous (s.c.) inoculation. To overcome these negative effects, we developed a recombinant, chimeric Sindbis/VEE virus (SIN-83) that is more highly attenuated. The genome of this virus encoded the replicative enzymes and the cis-acting RNA elements derived from Sindbis virus (SINV), one of the least human-pathogenic alphaviruses. The structural proteins were derived from VEEV TC-83. The SIN-83 virus, which contained an additional adaptive mutation in the nsP2 gene, replicated efficiently in common cell lines and did not cause detectable disease in adult or suckling mice after either i.c. or s.c. inoculation. However, SIN-83-vaccinated mice were efficiently protected against challenge with pathogenic strains of VEEV. Our findings suggest that the use of the SINV genome as a vector for expression of structural proteins derived from more pathogenic, encephalitic alphaviruses is a promising strategy for alphavirus vaccine development.

Serological and ecological study of the genus Leptospira in Jamaica

In a serological and ecological study of the genus Leptospira in Jamaica, 535 sera from three species of livestock animals, bovine, porcine and caprine were serologically tested by the microscopic agglutination technique using live leptospiral antigens. Of the number tested, 316 (59.06 percent) were reactive with titers equalling or greater than 1:100. A total of six serotypes were identified and representative serovars were as follows:- jules (serogroup Hebdomadis) 257 (51.92 percent); icterohemorrhagiae (serogroup Ictero-hemorrhagiae) 140 (28.07 percent); autumnalis (serogroup Autumnalis) 41 (8.3 percent); canicola (serogroup Canicola) 30 (6.06 percent); pomona (serogroup Pomona) 25 (5.19 percent) and abramis (serogroup Pyrogenes) 2 (0.4 percent). The porcine species recorded the highest percentage of reactive sera (65.5 percent) and the caprine the lowest (38.9 percent). The widest distribution of serotypes occurred in pigs. A comparison of the parishes showed that the positive sera from Portland (80.9 percent) and Westmoreland (71.6 percent) topped others and St. Andrew had the lowest 11.0 percent. For the ecological study, 22 soil and 25 water samples collected from five selected livestock farms in the island were cultured initially in enrichment artificial medium (Ellinghausen and McCullough semi-solid), ESS, incorporating 5-fluorouracil, for the isolation of leptospires. A total of 23 (48.9 percent) isolates were obtained:- 16 (72.7 percent) from the soil samples and 7 (28 percent) from the water samples. One water isolate was lost and the 22 parent isolates were subsequently inoculated into weanling hamsters. The kidney tissues and heartblood of the inoculated hamsters on culture yielded 8 leptospiral isolates and the microscopic agglutination test of the sera of inoculated hamsters gave 9 reactive results. There was no positive results either from culture or serological test of the control (uninoculated) hamsters. The investigations revealed that the constituents of Jamaican soil, the heavy rainfall and the various environmental factors are ideal for the survival and distribution of leptospires in the island. Flooding helps to spark off epizootic outbreaks and the leptospiral serotypes mentioned earlier are enzootic and endemic in Jamaica. The predominant serotypes are jules and icterohemorrhagiae. People at high risk are the livestock attendants and milkers. The epidemiological importance of the serotypes identified and suggested means of dealing with their adverse effects are discussed (AU)

Isolation of Rio Bravo and a hitherto undescribed agent, tamana bat virus, from insectivorous bats in Trinidad, with serological evidence of infection in bats and man

Between 1972 and 1974, 3,278 bats of 28 species were processed for virus isolation by suckling mouse (SM) inoculation. Two strains each of two related viruses, not hitherto reported from Trinidad, were isolated from insectovorous bats. Rio Bravo (RB) virus was isolated from salivary glands and saliva of the house bat, Molossus ater. The other virus, isolated from salivary glands, saliva and spleen of the molustache bat, Pteronotus parnollii, is a hitherto undescribed agent herein named Tamana bat virus (TBV). This virus has arbovirus characteristics: sensitivity to ether, pathogenicity for SM, and ability to hemagglutinate goose erythrocytes, but no serological relationship with known arboviruses and other viruses could be detected. In inoculation experiments with TBV, fatal illness was produced only in infant mice and rats, salivary virus excretion was demonstrated in a monkey and in Phyllostomus hastatus bats, and virus was passed in bats by subcutaneous inoculation of infected saliva. Sera of humans and 39 species of bats were tested for hemagglutination inhibition (HI): 46 out of 169 human and 125 out of 887 bat sera reacted with RB antigen, and of the positive bat sera reacted with TBV antigen, positives occurring in 15 bat species comprising insectovorous, fruit-eating and vampire bats, with highest incidence in cave-roosting species. In SM neutralization tests, 18 out of 27 HI-positive human sera protected against RB, 1 out of 10 against TBV; bat sera protective against RB were found in 4 insectovorous species, and against TBV in 8 species including the vampire bat, Desmodus rotundus. No evidence of arthropod transmission of either virus was found (AU)

Immunization against leptospirosis: continued vaccine trials in hamsters using strains isolated from Barbados

Heated whole-cell suspensions of L. interrogans serotype copenhageni strains isolated from the field in Barbados have proved to be protective immunogens against experimental leptospirosis (AU)

Enzootic rodent leishmaniasis in Trinidad, West Indies

Human cutaneous leishmaniasis is a zoonotic disease widely distributed in Central and South America. Small mammals play important roles in the natural history of the disease. This article attempts to define more precisely the roles that these mammals play in the ecology of the parasite.(AU)

Studies of Patois group arboviruses in Mexico, Guatemala, Honduras, and British Honduras

Patois, Zegla, and Shark River-like arboviruses in the Patois group were isolaed in Mexico, Guatemala, Honduras, and British Honduras during 1963 to 1968. Twenty-three Patois viruses came from mosquitoes, sentinel hamsters, and suckling mice, 21 Zegla viruses from sentinel hamsters and mice and from a wild cotton rat, and two Shark River-like viruses from sentinel hamsters. Hemagglutination-inhibition(HI) and neutralizing antibody tests with Patois virus were positive with human sera from each country, and HI antibody tests were positive with sera from pigs in Mexico, Guatemala, and British Honduras and from small wild mammals, wild birds, and cattle in Mexico.(AU)

Comparison of two human pathogenic strains with a commensal strain of Herpes Simplex virus isolated at the University Hospital of the West Indies

Comparision has been made between two human "neuropathogenic" and one "commensal" strains of herpes simplex virus. These terms are assigned to these viruses on the basis of their origin. The first two were related from patients with encephalitis and the third from a benign recurrent lesion. A number of physiochemical characteristics of these three strains were studied. The major differences observed between the "pathogens" and the "commensal" virus are: 1. The ability of the commensal herpes virus to infect adult mice while the pathogenic herpes could not. 2. The commensal herpes virus could not be neutralized by the hyperimmune sera of the pathogenic herpes and vice versa, although all crossreacted in complement fixation tests. 3. The commensal virus was significantly inactivated by chloroform, while the pathogens were not significantly affected under the same conditions. 4. Freezing and thawing followed by differential centrifugation rendered the commensal herpes vulnerable to inactivation of DNAse. Inactivation of the pathogens by this enzyme could only be acheived after chromatography on the anion exchanger, Diethyl aminoethyl. 5. The absorbtion spectrum gave a maximum peak at wave lenghts between 260-270 mu for the pathogenic virus. The peak absorption of the commensal herpes was at 280 mu. The peak at 260-270 mu by the pathogens is most likely due to the presence of nucleic acid. The peak absorption of the commensal virus is similar to that given by a typical protein. The relatively high concentration of protein which accompanies the commensal virus might account for the behaviour of this virus. 6. The "pathogenic" and "commensal" strains could be distinguished with respect to susceptibility to interferon. The commensal strain being more susceptible and also more effective in inducing interferon synthesis. 7. The method of comparision used in this investigation, and the results which reflect the marked difference between the strains of herpes simplex studied here produce some methods which may be used for differentiating between pathogenic and commensal strains of herpes simplex virus. It would appear that the methods used here are valuable to the study of viral genetics and the physiochemical study of herpes viruses. Evidence has been presented to show that there is molecular structural difference between the pathogenic and the commensal strains of herpes simplex virus. Such a difference or such differences may provide tools to probe into the pathogenic physiology of infected cells, or help to elucidate the factors responsible for neurotropicity and commensalism in herpes virus. The author is convinced that the differences cited above are genetically based. However, until further investigations are carried out, it is a subjective choice whether to consider the differences as sufficient basis for the subgrouping of herpes simplex virus. No claim is made that the distinction cited are attributes of other strains associated with encephalitis or limited lesions of recurrent herpes (AU)

A comparitive study of virulences, plaque morphologies and antigenic characteristics of Venezuelan encephalitis virus strains

Virulences of VE virus strains from tropical regions of the North and South American continents were studied in adult Syrian hamsters, Swiss albino mice and cotton rats. Virulence profiles were based on frequency and time of illness and death following subcutaneous inoculation of small doses of virus as collected in nature or after only a few passages in laboratory hosts. Forty-one strains from Mexico, USA-Florida, Panama, Colombia, and Venezuela uniformity killed hamsters inoculated s.c. with 4-1000 PFU; incubation periods were usually 3-6 days, but some Panamanian and USA-Florida strains had incubation periods 1-2 days longer than strains from other countries. All of 37 strains from these countries regularly produced illness in adult mice, but killed only 71-82 percent; in adult cotton rats, signs of illness were not recognized, but death occurred in 18-30 percent. Variations in virulence profiles for mice and cotton rats among 28 Mexican strains were ogten as great as those seen among 9 strains from USA-Florida, Panama, Colombia and Venezuela. Virus strains from the Bush Bush areas of Trinidad, however, had distinctive virulence profiles. All 5 of these strains killed hamsters only after prolonged incubation periods of more than 5 days, and killed only 1 of 25 mice; neither of two strains killed cotton rats. Young and Johnson reported (Amer. J. Epid., 1969, 89 286-307) that these Trinidad strains should antigenically be classified as Mucambo rather than VE virus. The TC 83 attenuated strain of VE virus in a dose of 500 PFU given s.c. killed no hamsters, mice or cotton rats, but in some experiments employing larger doses, up to 20 percent hamsters became ill and 5-10 percent died without apparent relationship to dose. Plaque sizes and morophologies of 19 VE and 5 Trinidad Mucambo virus strains in primary chicken embryonic cell cultures did not correlate with virulence for hamsters, mice, cotton rats or man, nor with geographic, host or tissue source or year of collection. In sera of cotton rats and mice 3-4 weeks after s.c. inoculation, titers of VE virus HI antibody measured with hemagglutinin from a Mexican virus strain were similar for strains from Mexico, Colombia and Venezuela. However they were lower with USA-Florida and TC 83 virus strains and with Trinidad Mucambo virus strains, suggesting that these viruses differ antigenically from Mexican, Colombian and Venezuelan strains. Nevertheless the attenuated TC 83 vaccine virus protected adult mice against s.c. challenge by 28 Mexican and 8 other VE virus strains from USA-Florida, Panama, Colombia and Venezuela, suggesting that immunologically distinct types of VE virus based on cross-protection do not exist in these countries. (AU)

The role of parainfluenza viruses in respiratory diseases in Trinidad

Studies in other countries have shown that the parainfluenza viruses play an important role in respiratory disease especially among infants and children. Serologic evidence of infection with parainfluenza three was found to be widespread reaching up to 90 percent in children and 100 percent in adults. This study, conducted in Trinidad, W.I. shows that the parainfluenza viruses are not the major cause of respiratory disease in that country. Serological tests, hemagglutination inhibition, neutralization tests and complement fixation tests show that the incidence of antibody in Trinidad is much lower than that in other countries of temperate climate. Parainfluenza 1, 2, and 3 viruses were isolated from cases of respiratory disease during the course of the study but no epidemics caused by these viruses were seen. That is, no real increase of respiratory disease reflected in increased admissions to hospital or attendance at clinics was seen that could be traced to parainfluenza virus infections. These viruses seem to be the sporadic cause of respiratory disease in Trinidad. The incidence seems to be spaced over a period of months in a given year (AU)

Experimental transmission of Leishmania mexicana by Lutzomyia cruciata

A rodent strain of Leishmania mexicana was transmitted to man by the bites of two experimentally infected specimens of Lutzomyia cruciata. Some factors infleuncing the transmission of the parasite to mammalian hosts, and the significance of transmission experiments are discussed briefly. Despite the experimental evidence, further evidence is needed before Lu. cruciata can be considered a natural vector of dermal leishmaniasis in British Honduras.(Summary)

Nariva virus, a hitherto undescribed agent isolated from the Trinidadian rat, Zygodontomys b. brevicauda (J. A. Allen & Chapman)

Nariva virus is a new, ether-sensitive agent isolated on four separate occasions from rodents, Zygodontomys b. brevicauda, caught in Bush Bush forest in the Nariva swamp, eastern Trinidad, in 1962 and 1963. Identification of the virus and its behavior in various animals and tissue cultures are reported. Limited studies disclose no evidence of human infection with Nariva virus. Twenty-three of 29 Zygodontomys captured during the period the isolations were made had Nariva virus neutralizing antibodies. (AU)

Aruac virus, a new agent isolated from Trinidadian mosquitoes

A previously undescribed virus has been isolated from Culex spp., Psorophora ferox and sabethine mosquitoes in Trinidad. The name Aruac is proposed for this agent. Aruac virus has not been isolated from any source other than mosquitoes. Neutralizing antibody to the virus has not been demonstrated in human serum. Some of the physical and biological properties of the virus are described. (AU)

Oropouche virus: a new human disease agent from Trinidad, West Indies

The isolation and laboratory studies of a new virus isolated from a human fever case in Trinidad, West Indies, are described. The virus has been named Oropouche virus after the region from which it was obtained. Oropouche virus has been to be related to Simbu virus, an agent isolated in South Africa. Neutralizing antibodies were found in the blood of a few forest workers, 8 of 26 native cebus monkeys in the Nariva Swamp and 9 of 26 howler monkeys widely distributed over the island. (Summary)

Triniti virus, a new agent isolated from Trinidadian mosquitoes

A previously undescribed agent has been isolated from Trichoprosopon mosquitoes captured in the Arena Forest in central Trinidad. The name Triniti virus is proposed for this agent neutralizing antibody to the virus has been demonstrated in human serum. Some of the physical and biological properties of the virus are described.(AU)

Dermal leishmaniasis in British Honduras - the vector

Flies of genus Phlebotomus, analogous to those which are vectors of leishmaniasis in the Old World, were studied in forest areas in British Honduras in order to determine whether they also were vectors of leishmaniasis. The disease was transmitted from an infected hamster to a human volunteer by a phlebotomus sandfly. It was also found possible to infect hamsters by injections of suspensions of triturated wild-caught man-biting Phlebotomes (AU)