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Biomedical subjects

B E Lachmi

Publications and source records attributed to B E Lachmi.

12 recordsLinked to original sources
PubMed2000

A live attenuated West Nile virus strain as a potential veterinary vaccine.

This article reviews the development of two attenuated West Nile virus (WNV) variants, WNI-25 and WNI-25A. These variants have lost the neuroinvasion trait of the parental virus. Attenuation was achieved through serial passages in mosquito cells and neutralization escape from WNV-specific monoclonal antibody. Genetic analysis reveals amino acid changes between the parental and each of the variants. The attenuated variants preserve the ability to replicate in mice and geese and to induce a protective immune response. WNI-25A was found to be a genetically stable virus. This variant was successfully used as a live vaccine to protect geese against a wild-type virulent WNV field isolate that closely resembles the WNV isolated during the 1999 New York epidemic.

Animals↗
PubMed1998

Development of RT-PCR for turkey meningoencephalitis virus and partial sequence analysis of the NS5 gene.

Turkey meningoencephalitis virus (TMEV) causes paralysis and mortality in turkeys. Because the classical diagnostic methods are complicated, we developed the RT-PCR as a new molecular diagnostic method. Since the nucleic acid sequence of TMEV is unknown, the first step in developing the RT-PCR relied on conserved sequences of viruses belonging to the Flaviviridae family, in which TMEV has been classified serologically. Using primers from the NS5 gene, three amplification products of TMEV RNA were obtained (125 bp, 181 bp and 800 bp). Their sequences were homologous to one another and to the NS5 gene of other flaviviruses.

Animals↗
PubMed1991

Adjuvant effects of dimethyl dioctadecyl ammonium bromide, complete Freund's adjuvant and aluminium hydroxide on neutralizing antibody, antibody-isotype and delayed-type hypersensitivity responses to Semliki Forest virus in mice.

Outbred mice were inoculated subcutaneously with inactivated Semliki Forest virus (SFV) in saline and combinations of the virus with complete Freund's adjuvant (CFA) aluminium hydroxide (Al) and dimethyl dioctadecyl ammonium bromide (DDA). The immune response was evaluated for delayed-type hypersensitivity, for total ELISA antibodies and antibody-isotypes and for neutralizing antibodies. DDA was the most efficient adjuvant in inducing DTH, CFA the second and Al induced a DTH response that was only slightly higher (statistically not significant) than that induced by the inactivated virus without adjuvants. All adjuvants enhanced the production of ELISA antibodies to similar levels. However, the levels of neutralizing antibodies induced were low in mice which were inoculated with the inactivated SFV alone or mixtures of the virus with Al. DDA induced high levels of neutralizing antibodies and CFA induced intermediate levels. The pattern of antibody-isotypes induced by DDA and CFA was different from the pattern induced by the inactivated virus or by the virus mixed with Al: DDA and CFA induced low amounts of IgG1 antibodies and relatively higher amounts of IgG2a and IgG2b antibodies while the inactivated virus and the mixture of the virus with Al induced higher proportions of IgG1 antibodies. In sera from convalescent mice the majority of antibody activity resided in the IgG2a and IgG2b immunoglobulin subclasses, while IgG1 antibodies were undetectable.

Adjuvants, Immunologic↗
PubMed1989

Semliki Forest virus E2 envelope epitopes induce a nonneutralizing humoral response which protects mice against lethal challenge.

Along the 422 amino acids of the Semliki Forest virus (SFV) E2 envelope glycoprotein, we identified 13 peptide cassettes (ranging in size from 15 to 25 amino acids and designated A through N) that contain hydrophilic sequences flanked by amino acid sequences conserved in the E2 envelopes of the alphavirus family. Six peptide blocks containing either a single cassette or two to three contiguous cassettes (A, BC, DE, FG, HIK, and LMN) were produced in Escherichia coli as recombinant proteins fused to the N terminus of beta-galactosidase. All of the SFV E2 recombinant polypeptides except A-beta-galactosidase were recognized on Western blots (immunoblots) by anti-SFV polyclonal antisera. In addition, these five recombinant proteins induced in mice antibodies that interacted specifically with SFV E2 protein on Western blots as well as with the intact virions in an enzyme-linked immunosorbent assay. The six hybrid proteins were used to vaccinate mice and were tested for the ability to confer resistance against lethal doses of SFV. Peptides BC and HIK, located at amino acid positions 114 to 149 and 216 to 288, respectively, of E2, protected partially (40 to 60%) against SFV challenge. A third peptide, LMN, located between amino acid positions 289 and 352, rendered mice totally resistant to an SFV challenge of 250 50% lethal doses. The partially protective effects of the BC and HIK cassettes and the high efficacy of the LMN cassette were consistently demonstrated, independent of the adjuvant (complete Freund or alum), immunization protocol, and strain of mice used. None of the antisera raised against any given cassette could neutralize the virus in an in vitro tissue culture assay or in a plaque reduction neutralization test. Nevertheless, passive transfer experiments demonstrated that in the case of LMN, the protective effect was mainly of a humoral nature.

Amino Acid Sequence↗
PubMed1985

Determination of human IgG and IgM class antibodies to West Nile virus by enzyme linked immunosorbent assay (ELISA).

An enzyme-linked immunosorbent assay (ELISA) was developed and used for the detection of IgG and IgM antibodies to West Nile virus in human sera. Thirteen paired sera of clinical cases and 24 control sera taken randomly from a blood bank repository were tested. The sera were reacted in microtiter plates coated with PEG-treated WNV antigen. IgG or IgM antibodies were quantitated by the use of alkaline-phosphatase-conjugated anti-human IgG or IgM antibodies. Of the 24 randomly collected serum samples, 7 were positive in the IgG-ELISA test. One positive by the IgM-ELISA was found to contain rheumatoid factor. In 12 of 13 paired sera of clinical cases, IgM as well as IgG antibodies were detected in the second serum sample taken about 3 wk after the onset of clinical signs. The IgM positive sera were screened for rheumatoid factor (RF) on IgG-coated plates. None of them contained RF. Antibody titers obtained by ELISA showed a good correlation with titers obtained by hemagglutination inhibition, complement fixation, and neutralization tests. The ELISA tests for detection of IgM and IgG antibodies to WNV therefore can replace the other serological methods for epidemiological surveillance and diagnostic purposes.

Antibodies, Viral↗
PubMed1976

Sequential translation of nonstructural proteins in cells infected with a Semliki Forest virus mutant.

Four nonstructural proteins with apparent molecular weights of 70,000 (ns-70), 86,000 (ns-86), 78,000 (ns-78), and 60,000 (ns-60) were translated in cells infected with Semliki Forest virus ts-1 mutant and maintained at the restrictive temperature. After synchronization of the initiation of protein synthesis these proteins were synthesized in the above order, suggesting that they are translated as a polyprotein starting from one initiation site. Two short-lived intermediates with apparent molecular weights of 155,000 and 135,000 were regularly detected. The former is presumably the precursor of proteins ns-70 and ns-86 and the latter of ns-78 and ns-60. The sequence of the structural proteins in their polyprotein was confirmed to be capsid-envelope E-2 (and E-3)-envelope E-1, beginning from the NH2-terminal end. We conclude that in Semliki-Forest-virus-infected cells two polyproteins are synthesized, one for the structural (130,000 daltons), the other for the nonstructural proteins (close to 300,000 daltons).

Mutation↗
PubMed1976

Transitional control in Semliki forest virus infected cells.

The cistron of the 42 S RNA, which codes for other than structural proteins, is poorly translated in the middle of the growth cycle. The translational control operating in the infected cells is not expressed in cell-free protein synthesising systems programmed with the 42 S RNA, since mostly non-structural proteins are made in vitro. One of our temperature-sensitive mutants of SFV, ts-1, directs the synthesis of two non-structural proteins with molecular weights of 78,000 (ns-78) and 86,000 (ns-86) but only at the restrictive temperature. This indicates that the synthesis of the non-structural proteins is controlled by viral rather than cellular factor(s). Temperature shift experiments revealed that the control mechanism was only slowly affected by the change of the temperature.

Cell Line↗
PubMed1975

Tryptic peptide analysis on nonstructural and structural precursor proteins from Semliki Forest virus mutant-infected cells.

Analysis of [35S]methionine-labeled tryptic peptides of the large proteins induced by temperature-sensitive mutants of Semliki Forest virus was carried out. The 130,000-molecular-weight protein induced by ts-2 and ts-3 mutants contained the peptides of capsid protein and of both major envelope proteins E1 and E2. The ts-3-induced protein with molecular weight of 97,000 contained peptides of the capsid and envelope protein E2 but not those of E1. Two proteins with molecular weights of 78,000 and 86,000 from ts-1-infected cells did not contain the peptides of the virion structural proteins. They are evidently expressions of the nonstructural part of the 42S RNA genome of Semliki Forest virus.

Autoradiography↗