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L N Bhau

Publications and source records attributed to L N Bhau.

12 recordsLinked to original sources
PubMed1994

Introduction of plasmid carrying an incomplete set of genes for aerobactin production alters virulence of Escherichia coli HB101.

The aerobactin-mediated iron uptake system is encoded by pColV-K30 and other ColV plasmids. It has been known to contribute to the ability of Escherichia coli to cause pyelonephritis and cystitis. In the present study an attempt was made to evaluate the contribution of an incomplete set of genes for aerobactin synthesis to the virulence of Escherichia coli HB101. Escherichia coli HB101 was transformed with a recombinant plasmid pJHCV-12 (Tetr and Kanr) carrying aerobactin genes (complete first two genes, iucA and iucB and part of the third gene iucC) from pColV-K30. Both HB101 and a transformant H10 grew equally well when applied to a Vero cell line. These strains were tested for their ability to invade and kill Vero cells in monolayers. Light micrographs showed cell damage by the transformant carrying pJHCV-12 plasmid and this cytotoxic effect correlated with the amount of lactate dehydrogenase (LDH) released. In contrast, strain HB101 and HB101 containing parent vector pVK102 did not produce any cytotoxic effects. When the ability of these strains to produce ascending pyelonephritis in a mouse model was compared, the transformant established itself better in renal tissue than the control strain HB101, when assessed 2h, 4 h and 5 days post-infection.

Animals↗
PubMed1991

Thermostability of Japanese encephalitis vaccine produced in India.

Different batches of bulk vaccine, final bulk at in-process level, finished freeze-dried and reconstituted Japanese encephalitis vaccine were assayed for their stability at temperatures of 22, 37 and 40 degrees C. After ultrazonal purification of 50 times concentrated brain suspension, JE Bulk vaccine was found to be stable for up to 2 years at 4 degrees C, however, the percentage loss in potency (log 10 N antibody titre) after 2.5 years was 24%. Three-times concentrated final bulk showed rapid deterioration by the fourth week at 37 and 40 degrees C. Freeze-dried JE vaccine maintained at 22 degrees C for 28 weeks did not show perceptible deterioration. At 37 degrees C, the same vaccine started showing deterioration (14%) after 8 weeks whereas at 40 degrees C the loss of potency was 24% after 8 weeks. The freeze-dried vaccine was found to be stable for up to 2 weeks duration at 40 degrees C.

Drug Stability↗
PubMed1990

Indirect haemagglutination test for the assay of antibodies against Japanese encephalitis viral antigen in human & animal sera.

The indirect haemagglutination (IHA) test was standardized for the assay of antibodies against Japanese encephalitis (JE) virus. Glutaraldehyde fixed sheep erythrocytes were sensitized with purified and concentrated JE vaccine (200-300% brain concentration). The JE vaccine made from Nakayama-NIH strain of JE virus was purified by protamine sulphate treatment and by ultracentrifugation in a sucrose gradient. The sensitized cells were quite stable in liquid as well as in lyophilized state both at -70 degrees C and 4-8 degrees C. These cells could be used for two years without much loss (4-8 times loss) in titre. The IHA test was as sensitive as the neutralization (N) test performed by plaque reduction method in chick embryo fibroblasts. The sensitivity of the test was influenced by the source of erythrocytes i.e., from the different sheep from which these were drawn. After standardization of the test, 16 human sera and 18 sera of immunized mice were assayed for antibodies against JE virus by N and IHA tests. There were no significant differences between titres of both human and mice sera determined by N and IHA tests (P greater than 0.05). The correlation coefficient between N and IHA titres for human sera was 0.60 (P less than 0.05) and for mice sera 0.82 (P less than 0.01). The IHA test has been found to be very simple, inexpensive, sensitive and reproducible.

Animals↗
PubMed1989

Immune status of volunteers one year after administration of Japanese encephalitis vaccine produced in India.

The immune status of 40 volunteers who received the full course of Japanese encephalitis (JE) vaccine a year earlier and 15 individuals who had received only a booster dose at the same time, was studied by estimating the level of persistence of protective antibody in the sera. All the sera showed persistence of 100 per cent seroconversion rate. Individuals who had the full course of vaccination still had high levels of antibody (mean 2.8 Iog10); however there was a fall of 0.8 Iog10 from the post-booster level. Volunteers who had received only a booster dose, also showed persistence of high level of protective antibody (mean 2.4 Iog10), a drop of 0.9 Iog10 from the post-booster level. Neutralizing (N) antibody estimated using Dibrugarh (7812474) strain of JE virus also demonstrated persistence of high level of protective antibody against this virus (mean 2.4 Iog10). Persistence of high level of protective antibody against homologus and heterologus (Dibrugarh) virus strains and absence of vaccine related side-effects even one year after administration of JE vaccine produced in India, demonstrates the immunizing potency and safety of this new vaccine.

Adolescent↗