Biomedical subjects

H H Houng

Publications and source records attributed to H H Houng.

3 recordsLinked to original sources

PubMed2000

Quantitative detection of dengue 2 virus using fluorogenic RT-PCR based on 3'-noncoding sequence.

A fluorescent DNA probe (DV2.P1) specific to the conserved distal 3'-noncoding region (nucleotides 10653-10678) of dengue 2 virus and a pair of flanking primers (DV2.L1 and DV2.U2) were designed to formulate a dengue 2-specific fluorogenic polymerase chain reaction (PCR). In addition, DV2.L1 was also used as a reverse transcription (RT) primer to generate superior cDNA from dengue viral RNA. Optimal assay conditions with zero background were established to detect low levels of dengue 2 virus from clinical specimens. The range of dengue virus detection in spiked human sera was determined to be from 10 to 10(6) infectious virions per milliliter (plaque forming units determined using Vero cell line). Dengue 2 virus isolates from different geographic regions can be detected universally and identified by the fluorogenic RT-PCR assay. Moreover, the assay is specific for dengue 2 virus and does not recognize other related flaviviruses, including dengue serotypes 1, 3 and 4, Japanese encephalitis, St. Louis encephalitis, yellow fever, and Kunjin viruses. The assay also detected efficiently immunocomplexed dengue viruses. In practice, the fluorogenic RT-PCR assay detected readily viremia in sera collected from individuals ill with dengue fever. The rise and fall of dengue 2 virus concentrations in rhesus monkeys, reflecting viral proliferation and clearance, was also clearly illustrated by the assay.

3' Untranslated Regions↗

PubMed1997

Lymphocyte proliferative responses of goats vaccinated with Brucella melitensis 16M or a delta purE201 strain.

The response to a Brucella melitensis purEK deletion mutant, delta purE201 (referred to as strain 201), was compared with the response to its parental strain, 16M, in juvenile goats. Proliferative responses to gamma-irradiated bacteria were detected earlier in strain 201-infected goats. Lymphocytes from strain 16M- or 201-infected goats proliferated in response to one-dimensional polyacrylamide gel electrophoresis-separated proteins of similar mass isolated from strain 16M or Brucella abortus RB51. Data from this study suggest that some antigens stimulating cell-mediated responses are conserved among Brucella species, as 201- and 16M-infected goats recognized similar proteins expressed by RB51 and 16M.

Animals↗

PubMed1996

Deletion of purE attenuates Brucella melitensis infection in mice.

We previously showed that a purE mutant (delta purE201) of Brucella melitensis 16M is attenuated for growth in cultured human monocytes (E. S. Drazek, H. H. Houng, R. M. Crawford, T. L. Hadfield, D. L. Hoover, and R. L. Warren, Infect. Immun. 63:3297-3301, 1995). To determine if this strain is attenuated in animals, we compared the growth of the delta purE201 mutant with that of strain 16M in BALB/c mice. The number of bacteria in the spleen and spleen weight peaked for both strains between 1 and 2 weeks postinfection (p.i.), though the number of delta purE201 cells was significantly less than the number of 16M cells recovered from the spleens of infected mice. During the next 6 weeks, delta purE201 was essentially eliminated from infected mice (three of five mice sterile; < 100 CFU in two of live mice at 8 weeks p.i.), whereas bacteria persisted at a high level in the spleens of 16M-infected mice (about 106 CFU per spleen). The number of bacteria in the livers and lungs of mice infected with either strain paralleled those in the spleen. Mice infected with 16M had a strong inflammatory response, developing dramatic and prolonged splenomegaly (five to eight times normal spleen weight) and producing serum interleukin-6. In contrast, mice infected with delta purE201 developed only mild, transient splenomegaly at 1 week p.i. and produced no interleukin-6 in their serum. We further characterized the host response to infection by measuring changes in immune spleen cell populations by flow cytometry. CD4- and CD8-positive lymphocytes declined by I week in both experimental groups, while MAC-1-positive cells increased. T-cell subpopulations remained low or declined further, and MAC-1 cells increased to three times normal levels during 8 weeks of infection with 16M but returned to normal by 4 weeks after infection with delta purE201. These results document infectivity and attenuation of delta purE201 and suggest that it should be further evaluated as a potential vaccine.

Animals↗