Pricha Singharaj

Mahidol University, Siayuthia, Bangkok, Thailand

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Publications (10)25.82 Total impact

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    ABSTRACT: ALVAC-HIV (vCP1521) and AIDSVAX B/E were evaluated in a phase 1/2 trial of human immunodeficiency virus (HIV)- negative Thai adults. Of 133 volunteers enrolled, 122 completed the trial. There were no serious vaccine-related adverse events, nor were there intercurrent HIV infections. Lymphoproliferative responses to glycoprotein 120 E were induced in 63% of the volunteers, and HIV-specific CD8 cytotoxic T lymphocyte responses were induced in 24%. Antibody responses increased in frequency and magnitude in association with the dose level of AIDSVAX B/E. Binding and neutralizing antibodies to the MN strain were induced in 100% and 98%, respectively, of the volunteers receiving 600 µg of AIDSVAX B/E, and such antibodies to E strains were induced in 96% and 71%, respectively, of these volunteers. This vaccine combination was well tolerated and was immunogenic, meeting milestones for advancement to phase 3 evaluation.
    Full-text · Article · Sep 2004 · The Journal of Infectious Diseases
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    ABSTRACT: In 1992 the Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand, collaborated with the Phramongkutklao Army Medical Center to set up the Joint Clinical Research Center (JCRC). The purpose of the Center is to conduct clinical research in support of HIV vaccine development and testing. To date, eight HIV vaccine-related research protocols have been conducted at the JCRC, involving 1,668 volunteers. The JCRC has been, and continues to be, a key site for the transfer of clinical trial expertise to new sites at universities, government clinics and hospitals in Thailand and other countries. Overall rates of follow-up have been excellent, while protocol violations and data clarification errors have been minimal.
    Full-text · Article · Apr 2003 · The Southeast Asian journal of tropical medicine and public health
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    ABSTRACT: Geographic and demographic correlates of risk for HIV-1 seropositivity were studied in 120,216 young men selected by lottery for service in the Royal Thai Army (RTA). The study population consisted of men selected between November 1991 and May 1993. Venous blood was collected at induction, and a brief demographic questionnaire was administered. HIV-1 seropositivity was established by Western blot confirmation of duplicate reactive ELISAs. Geographic variables provided the strongest correlate of risk, clearly distinguishing residents of the upper north, Bangkok, and the central region from the northeast. Overall 12.2% of men from the upper north were HIV- positive. Men who had lived in rural areas were at less risk in most regions of the country, but had equal risk in the upper north. Unmarried men and those with less education were at higher risk throughout the country. These data provide valuable information on the prevalence of HIV infection in one segment of the general population. Continued surveillance of this group will facilitate evaluation of Thailand's response to the epidemic.
    No preview · Article · May 1996 · Journal of Acquired Immune Deficiency Syndromes and Human Retrovirology
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    ABSTRACT: Royal Thai Army (RTA) enlistees were tested for HIV-1 seropositivity prospectively in order to explore their feasibility as a cohort in an HIV-1 preventive vaccine efficacy trial. The 17,615 seronegative enlistees, virtually all 21-year-old men, contributed 10,409 person-years (p-y) of follow-up. Cohorts were enlisted in November 1991 and May 1992 from northern Thailand and Bangkok. The follow-up rate was 50%, with loss to follow-up significantly associated with location of the base, marital status, and educational level. Seroincidence was 0.5/100 p-y for recruits stationed in Bangkok, 1.0/100 p-y in the lower north, and 3.2/100 p-y in the upper north. In a multiple regression model, the young man's birthplace was strongly associated with risk of infection, suggesting that transmission occurred during leave as well as during duty. Incidence rates were significantly lower in those who were married at the time of enlistment and in those with 3$$10 years of education. The seroincidence rates among recruits stationed in the upper north support vaccine trial feasibility, but follow-up rates need to be improved.
    No preview · Article · Dec 1994 · JAIDS Journal of Acquired Immune Deficiency Syndromes
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    ABSTRACT: Royal Thai Army (RTA) enlistees were tested for HIV-1 seropositivity prospectively in order to explore their feasibility as a cohort in an HIV-1 preventive vaccine efficacy trial. The 17,615 seronegative enlistees, virtually all 21-year-old men, contributed 10,409 person-years (p-y) of follow-up. Cohorts were enlisted in November 1991 and May 1992 from northern Thailand and Bangkok. The follow-up rate was 50%, with loss to follow-up significantly associated with location of the base, marital status, and educational level. Seroincidence was 0.5/100 p-y for recruits stationed in Bangkok, 1.0/100 p-y in the lower north, and 3.2/100 p-y in the upper north. In a multiple regression model, the young man's birthplace was strongly associated with risk of infection, suggesting that transmission occurred during leave as well as during duty. Incidence rates were significantly lower in those who were married at the time of enlistment and in those with > or = 10 years of education. The seroincidence rates among recruits stationed in the upper north support vaccine trial feasibility, but follow-up rates need to be improved.
    No preview · Article · Dec 1994 · Journal of acquired immune deficiency syndromes
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    ABSTRACT: Thai soldiers were vaccinated with a recombinant protein derived from the central repeat region of the circumsporozoite (CS) protein of Plasmodium falciparum conjugated to Toxin A (detoxified) of Pseudomonas aeruginosa (R32Tox-A) to evaluate its safety, immunogenicity and efficacy. In a randomized, double-blind manner, 199 volunteers received either R32Tox-A or a control vaccine at 0, 8 and 16 weeks. Immunization was performed in a malaria non-transmission area, after completion of which volunteers were deployed to an endemic border area and monitored closely to allow early detection and treatment of infection. The vaccine was found to be safe and to elicit antibody responses in all vaccinees. Peak CS antibody (IgG) concentrations in malaria-experienced vaccinees exceeded those in malaria-naive vaccinees (mean 40.6 versus 16.1 μg ml−1; p = 0.005) as well as those induced by previous CS protein-derived vaccines and observed in association with natural infections. A log-rank comparison of time to falciparum malaria revealed no differences between vaccinated and non-vaccinated subjects. Secondary analyses revealed that CS antibody levels were lower in vaccinee malaria cases than in non-cases, 3 and 5 months after the third dose of vaccine (p = 0.06 and p = 0.014, respectively). Because antibody levels had fallen substantially before peak malaria transmission occurred, the question of whether high levels of CS antibody are protective remains to be resolved.
    No preview · Article · Mar 1994 · Vaccine
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    ABSTRACT: Two studies were conduct in Thailand in order to find appropriate falciparum malaria prophylactic drug regimens. The first study was done during June - September 1987 with 363 soldiers who received Fansimef (MSP) 1 tab/week (group 1), 337 soldiers who received MSP 1 tab/2 week (group 2) and 165 soldiers who received chloroquine 300 mg base weekly plus Fansidar 1 tab/week (group 3). At the end of the study there were 9 and 13 falciparum malaria episodes in groups 1 and 2, respectively, with incidence rates of 0.8 and 1.8 cases/100 person-months (P-M). In group 3, the corresponding values were 30 episodes and an incidence of 7.2/100 P-M. For the second study which lasted from October 1987 - January 1988 in the same area, 498 soldiers were given Fansimef 1/2 tab/week (group 4), 499 soldiers were given Lariam 1/2 tab/week (group 5) and 247 soldiers were given chloroquine plus Fansidar (group 6). Thirty malaria episodes were found in group 4, for an incidence of 2.0/100 P-M. In group 5, 23 episodes were found, for an incidence of 1.6/100 P-M. In group 6, 74 episodes occurred, ie an incidence of 12.2/100 P-M. The incidence rates of malaria among Fansimef 1 tab weekly, Fansimef half dose weekly or Lariam half dose weekly were not significantly different but were different from chloroquine plus Fansidar groups. Adverse events in each group were mild.
    No preview · Article · Jan 1994 · The Southeast Asian journal of tropical medicine and public health
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    ABSTRACT: To determine risk factors for HIV-1 infection in young men in northern Thailand. At enrollment into a prospective study, data were collected from a self-administered questionnaire and serologic testing on a cohort of 1115 young men selected by lottery for conscription. The overall HIV-1 infection rate was 6.9%; however, the rate was 15.3% among the 387 (34.7%) men who had been living in the upper north subregion of Thailand compared with 2.5% for the remaining 728 men (P < 0.001). A history of sex with female prostitutes was reported by 74.7% of men and increased frequency of this type of sex was highly associated with HIV-1 infection and a history of sexually transmitted disease (STD) symptoms (chi 2 for trend, P < 0.001). In stratified and multivariate analyses, however, history of STD symptoms, reported by 42.5% of the cohort, was most strongly associated with HIV-1 infection. Only 42.8% of men who reported sex with prostitutes had used condoms more than half the time. Young men in the general population in northern Thailand are at high risk for HIV-1 infection via sex with female prostitutes; STD are highly associated with HIV-1 infection. Increasing condom use and controlling STD should be immediate goals of HIV control programs.
    No preview · Article · Sep 1993 · AIDS
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    ABSTRACT: Serosurveys conducted prior to 1988 indicated a very low level of HIV-1 infection in Thailand, even among high-risk groups. The Ministry of Health has reported a dramatic increase in HIV-1 infection during the last three years. The geographic and demographic distribution of the epidemic is broad, involving multiple provinces and risk groups. Foci of higher incidence and prevalence have been noted in the urban center of Bangkok and in the northern provinces of Chiang Mai and Chiang Rai. Here we report the results of genetic characterization of 16 HIV-1 isolates from Thailand using a combination of polymerase chain reaction (PCR) typing and DNA sequencing. The complete sequence of gp160 (env) of five isolates, partial env sequence of six additional isolates, and the gag gene of two isolates were determined. Two highly distinct HIV-1 variants were found. One variant resembled those prevalent in North America and Europe; five of the isolates were of this type. The remaining eleven isolates were very similar to one another and represented a variant unlike any previously described. Phylogenetic tree analysis of complete env and gag genes placed the two variants on widely separated branches. Protein sequence comparisons indicate both general and specific features that distinguish the Northern Thailand variant both from the Bangkok variant and from virtually all previously sequenced HIV-1 isolates. A simple PCR test for distinguishing the two variants has been developed for use in epidemiologic surveys.
    No preview · Article · Dec 1992 · AIDS Research and Human Retroviruses
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    ABSTRACT: Serosurveys conducted prior to 1988 indicated a very low level of HIV-1 infection in Thailand, even among high-risk groups. The Ministry of Health has reported a dramatic increase in HIV-1 infection during the last three years. The geographic and demographic distribution of the epidemic is broad, involving multiple provinces and risk groups. Foci of higher incidence and prevalence have been noted in the urban center of Bangkok and in the northern provinces of Chiang Mai and Chiang Rai. Here we report the results of genetic characterization of 16 HIV-1 isolates from Thailand using a combination of polymerase chain reaction (PCR) typing and DNA sequencing. The complete sequence of gp160 (env) of rive isolates, partial env sequence of six additional isolates, and the gag gene of two isolates were determined. Two highly distinct HIV-1 variants were found. One variant resembled those prevalent in North America and Europe; five of the isolates were of this type. The remaining eleven isolates were very similar to one another and represented a variant unlike any previously described. Phylogenetic tree analysis of complete env and gag genes placed the two variants on widely separated branches. Protein sequence comparisons indicate both general and specific features that distinguish the Northern Thailand variant both from the Bangkok variant and from virtually all previously sequenced HIV-1 isolates. A simple PCR test for distinguishing the two variants has been developed for use in epidemiologic surveys.
    No preview · Article · Nov 1992 · AIDS Research and Human Retroviruses