A hamster-attenuated, temperature-sensitive mutant of Venezuelan encephalitis virus

Krieger, John N.; Scherer, William F.; Wiebe, Michael E.; Pancake, Bette A.; Harsányi, Zsolt

doi:10.1128/iai.25.3.873-879.1979

Cited by 10 publications

(5 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The attenuation of the virulence of the two ts strains was apparently not related to the shut-off temperature of 39.5°C since body temperatures of normal or infected mice remained within the permissive temperature range of the ts mutants (38°C). This result is no different from the results obtained with ts mutants of virus (9,10,12,15).…”

Section: Vol 42 1983contrasting

confidence: 59%

In vitro and in vivo properties of chemically induced temperature-sensitive mutants of Chlamydia psittaci var. ovis: screening in a murine model

Rodolakis¹

1983

Infect Immun

View full text Add to dashboard Cite

Two temperature-sensitive (ts) strains, 1B and 1H, were obtained after nitrosoguanidine treatment of the wild-type virulent abortive ovine strain Chlamydia psittaci AB7. Optimum growth temperature on McCoy cells was 38°C for the three strains, but at the restrictive temperature, 39.5°C, ts strains differed from the parental strain in their total infective yield of chlamydiae, their efficiency of plating, and the morphology of the plaques and cytoplasmic inclusions. Their survival at 51°C was also reduced compared with that of the wild field strains. The virulence of the two ts strains was attenuated for pregnant mice, but these two ts strains were able to multiply in mice and to induce a strong immunity to virulent challenge with either the parental AB7 strain or the caprine or bovine abortive field strains.Chlamydia psittaci, an obligate intracellular bacterium, induces placental infections and abortions in various mammals, in particular ewes. Although the disease induces a good immunity (20,22), vaccines prepared with inactivated chlamydiae emulsified in adjuvant have not really been efficient (11,13,19). An avirulent live vaccine administered before breeding could be the key to control of chlamydial abortion in ewes (20). Attempts to attenuate the chlamydial agent of ovine abortion by serial passages in the yolk sac of chicken embryos or in cell cultures were unsuccessful (2, 3). We then tried to isolate temperature-sensitive (ts) mutants. Two ts mutants were isolated in tissue culture after treatment of a virulent abortive strain of C. psittaci with N-methyl-N'-nitro-N-nitrosoguanidine (NTG). This study describes the in vitro and in vivo properties of these two ts mutants. MATERIALS AND METHODSCell culture. McCoy cells (7) were grown at 38°C in monolayer cultures in Eagle minimum essential medium containing 10o fetal calf serum (MEM).Strains of C. psitai. C. psittaci AB7 (6) in its second passage in chicken embryos after isolation from an aborted lamb was used as the parental strain for isolation of ts mutants. The following C. psittaci strains were used for comparative thermal inactivation studies or as infectious challenge: ovine abortive strains AB4, AB6, AB8, AB9, and AB10; caprine abortive strain AC1; bovine abortive strain AV1; ovine intestinal strains IB1 and IB2; and the ovine pneumonitis strain 109-75, which was a generous gift supplied by P. Russo, Laboratoire National de Pathologie des Petits Ruminants, Nice, France. The abortive strains were isolated in cell culture from vaginal swabs from the aborted animal, and the intestinal strains were obtained from the feces of healthy sheep (5).Stocks of chlamydiae were propagated in the yolk sacs of developing chicken embryos as previously described (16) and stored at -70°C. Infectivity titration. The titration of chlamydial infectivity for McCoy cells was performed by a plaque assay (1). Briefly, it was carried out on McCoy monolayers under a solid overlay medium containing 1.5% Noble agar. Counts were made on day 14 after staining with 1:10,000 neutral r...

show abstract

Section: Vol 42 1983contrasting

confidence: 59%

In vitro and in vivo properties of chemically induced temperature-sensitive mutants of Chlamydia psittaci var. ovis: screening in a murine model

Rodolakis¹

1983

Infect Immun

View full text Add to dashboard Cite

show abstract

“…-The avirulent virus fails to multiply (or multiplies only at a low rate) in the "target" tissue manifesting the virulence. For example, replication in the central nervous system (CNS) is the basis of virulence for many viruses, and attenuation arises from a reduced ability to replicate in the CNS but replication is nearly normal in other tissues (Venezuelan equine encephalitis virus: Krieger et al 1979;Emini and Wiebe 1981;reovirus: Kaye et al 1986;herpes simplex virus: Javier et al 1987).…”

Section: Iic Tissue Tropismsmentioning

confidence: 99%

Perspective: Virulence

Bull¹

1994

Evolution

382

277

View full text Add to dashboard Cite

Why do parasites harm their hosts? Intuition suggests that parasites should evolve to be benign whenever the host is needed for transmission. Yet a growing theoretical literature offers several models to explain why natural selection may favor virulent parasites over avirulent ones. This perspective first organizes these models into a simple framework and then evaluates the empirical evidence for and against the models. There is relatively scant evidence to support any of the models rigorously, and indeed, there are only a few unequivocal observations of virulence actually evolving in parasite populations. These shortcomings are surmountable, however, and empirical models of host-parasite interactions have been developed for many kinds of pathogens so that the relevant data could be acquired in the near future.

show abstract

“…Virus strain tsl26 from three female and three male mosquitoes of experiment A was still temperature sensitive (i.e., plaques developed in CEC at 32°C but not at 40°C). Virus from these six mosquitoes was tested for virulence by subcutaneous inoculation of hamsters (6). Virus in four mosquito suspensions was still attenuated.…”

Section: Resultsmentioning

confidence: 99%

“…MATERIALS AND METHODS Viruses. The seven strains of VE virus studied were selected to represent both epizootic (69Z1) and enzootic (68U201, Fe5-47et, BeAn8, and BeAr35645) sources of virus in nature, as well as attenuated mutants (ts126 and TC83) (1,2,6,13,15,16). The four hemagglutination inhibition subtypes of these strains are listed in the tables.…”

mentioning

confidence: 99%

Sensitivity of Toxorhynchites amboinensis mosquitoes versus chicken embryonic cell cultures for assays of Venezuelan encephalitis virus

Scherer¹,

Chin²

1981

J Clin Microbiol

Self Cite

View full text Add to dashboard Cite

Toxorhynchites amboinensis mosquitoes inoculated intrathoracically with Venezuelan encephalitis virus and tested for infectious virus 12 to 19 days later by inoculation of primary chicken embryonic cell cultures yielded approximately the same titers of virus as did direct inoculation of cultures, with counting of plaques 3 days thereafter. Titers were slightly higher in T. amboinensis for three virus strains, equal for two virus strains, and slightly lower for two virus strains. Comparative titers of four strains were similar, whether virus suspensions came from infectious vertebrate cells or infected invertebrate (T. amboinensis) cells. Each of the seven strains of Venezuelan encephalitis virus reached virus concentrations of 104.2 to 105i1 plaque-forming units in individual T. amboinensis mosquitoes after extrinsic incubation periods of 12 to 19 days. No temperaturesensitive (29 versus 37°C) virus was detected in T. amboinensis mosquitoes infected by six strains of Venezuelan encephalitis virus.

show abstract

A hamster-attenuated, temperature-sensitive mutant of Venezuelan encephalitis virus

Cited by 10 publications

References 16 publications

In vitro and in vivo properties of chemically induced temperature-sensitive mutants of Chlamydia psittaci var. ovis: screening in a murine model

In vitro and in vivo properties of chemically induced temperature-sensitive mutants of Chlamydia psittaci var. ovis: screening in a murine model

Perspective: Virulence

Sensitivity of Toxorhynchites amboinensis mosquitoes versus chicken embryonic cell cultures for assays of Venezuelan encephalitis virus

Contact Info

Product

Resources

About