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E Y Konadu,
F Y Lin,
V A Hó, N T Thuy,
P Van Bay,
T C Thanh,
H B Khiem,
D D Trach,
A B Karpas,
J Li,
D A Bryla,
J B Robbins,
S C Szu
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ABSTRACT: Salmonella enterica serovar Paratyphi A O-specific polysaccharide (O-SP) was activated with 1-cyano-4-dimethylaminopyridinium tetrafluoroborate (CDAP) and bound to tetanus toxoid (TT) with adipic acid dihydrazide as a linker (SPA-TT(1)) or directly (SPA-TT(2)). In mice, these two conjugates elicited high levels of immunoglobulin G (IgG) anti-lipopolysaccharide (LPS) in serum with bactericidal activity (E. Konadu, J. Shiloach, D. A. Bryla, J. B. Robbins, and S. C. Szu, Infect. Immun. 64:2709-2715, 1996). The safety and immunogenicity of the two conjugates were then evaluated sequentially in Vietnamese adults, teenagers, and 2- to 4-year-old children. None of the vaccinees experienced significant side effects, and all had preexisting LPS antibodies. At 4 weeks after injection, there were significant increases of the geometric mean IgG and IgM anti-LPS levels in the adults and teenagers: both conjugates elicited a greater than fourfold rise in the IgG anti-LPS level in serum in >/=80% of the volunteers. SPA-TT(2) elicited slightly higher, though not statistically significantly, levels of IgG anti-LPS than did SPA-TT(1) in these age groups. Accordingly, only SPA-TT(2) was evaluated in the 2- to 4-year-old children. On a random basis, one or two injections were administered 6 weeks apart to the children. No significant side effects were observed, and the levels of preexisting anti-LPS in serum were similar in children of all ages. A significant rise in the IgG anti-LPS titer was elicited by the first injection (P = 0.0001); a second injection did not elicit a booster response. Representative sera from all groups had bactericidal activity that could be adsorbed by S. enterica serovar Paratyphi A LPS.
Infection and Immunity 03/2000; 68(3):1529-34. · 4.16 Impact Factor
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Z Kossaczka,
F Y Lin,
V A Ho, N T Thuy,
P Van Bay,
T C Thanh,
H B Khiem,
D D Trach,
A Karpas,
S Hunt,
D A Bryla,
R Schneerson,
J B Robbins,
S C Szu
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ABSTRACT: The capsular polysaccharide of Salmonella typhi, Vi, is an essential virulence factor and a protective vaccine for people older than 5 years. The safety and immunogenicity of two investigational Vi conjugate vaccines were evaluated in adults, 5- to 14-year-old children, and 2- to 4-year-old children in Vietnam. The conjugates were prepared with Pseudomonas aeruginosa recombinant exoprotein A (rEPA) as the carrier, using either N-succinimidyl-3-(2-pyridyldithio)-propionate (SPDP; Vi-rEPA(1)) or adipic acid dihydrazide (ADH; Vi-rEPA(2)) as linkers. None of the recipients experienced a temperature of >38.5 degrees C or significant local reactions. One injection of Vi-rEPA(2) into adults elicited a geometric mean (GM) increase in anti-Vi immunoglobulin G (IgG) from 9.62 enzyme-linked immunosorbent assay units/ml (EU) to 465 EU at 6 weeks; this level fell to 119 EU after 26 weeks. In the 5- to 14-year-old children, anti-Vi IgG levels at 6 weeks elicited by Vi-rEPA(2), Vi-rEPA(1), and Vi were 169, 22.8, and 18.9 EU, respectively (P = 0.0001 for Vi-rEPA(1) and Vi with respect to Vi-rEPA(2)). At 26 weeks, the anti-Vi IgG levels for recipients of Vi-rEPA(2), Vi-rEPA(1), and Vi were 30.0, 10.8, and 13.4 EU, respectively (P < 0.001 for Vi-rEPA(1) and Vi with respect to Vi-rEPA(2)); all were higher than the preinjection levels (P = 0. 0001). Vi-rEPA(2) also elicited the highest anti-Vi IgM and IgA levels of the three vaccines. In the 2- to 4-year-old children at 6 weeks following the first injection, Vi-rEPA(2) elicited an anti-Vi IgG level of 69.9 EU compared to 28.9 EU for Vi-rEPA(1) (P = 0.0001). Reinjection increased Vi antibody levels from 69.9 to 95.4 EU for Vi-rEPA(2) and from 28.9 to 83.0 EU for Vi-rEPA(1). At 26 weeks, anti-Vi IgG levels remained higher than those at preinjection (30.6 versus 0.18 for Vi-rEPA(2) and 12.8 versus 0.33 for Vi-rEPA(1); P = 0.0001 for both). Vi vaccine is recommended for individuals of 5 years of age or older. In the present study, the GM level of anti-Vi IgG elicited by two injections of Vi-rEPA(2) in the 2- to 4-year-old children was higher than that elicited by Vi in the 5- to 14-year-old children (30.6 versus 13.4; P = 0.0001). The safety and immunogenicity of the Vi-rEPA(2) conjugate warrant further investigation.
Infection and Immunity 12/1999; 67(11):5806-10. · 4.16 Impact Factor
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ABSTRACT: To determine the HIV/sexually transmitted disease (STD) status of male patients at STD clinics and factors associated with frequent visits to commercial sex workers (CSW) in southern Vietnam.
Cross-sectional survey.
Confidential interviews and physical and laboratory evaluation of 804 male patients at STD clinics in two semi-rural provinces in the Mekong delta.
HIV seroprevalence was 0.5%. The prevalence of urethritis syndrome was 19.3%, gonorrhea 10.2% (Gram-stain positive) and syphilis 2% (reactive rapid plasma reagin test). All the men had visited CSW in the past and 58% had their first sexual experience with a CSW; 73% had visited a CSW in the last 3 years. Married men were equally as likely as single men to have casual partners or to have visited a CSW. The men recruited CSW more from the streets (45%) than from brothels (38%). Factors independently associated with visiting a CSW in the last 3 years included being single [odds ratio (OR), 2.2], age under 20 years (OR, 1.9), having first sexual intercourse with a CSW (OR, 2.1), not having a current girlfriend (OR, 2.1), using alcohol before sex (OR, 2.7) and drug use (OR, 1.8). Only 7% of men used condoms consistently; 70% had never used them. Only 37% had used a condom last time they had intercourse with a CSW.
Prevention programs for men in Vietnam, particularly those who are young or single, need to focus on reducing drug and alcohol consumption and improving condom use with CSWs.
AIDS 05/1999; 13(6):719-25. · 6.24 Impact Factor
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ABSTRACT: To determine the extent of HIV infection among female commercial sex workers (CSW), to identify risk factors, and to provide baseline data for developing and targeting prevention measures.
A total of 968 female CSW were enrolled in a cross-sectional study from August 1995 to October 1996. Information was obtained from confidential face-to-face interview, physical examination, and laboratory testing.
A total of 65.5% of female CSW reported inconsistent condom use. Overall seroprevalence was 5.2%. The highest seroprevalence (9.5%) was detected in An Giang province, a border area adjacent to Cambodia. Out of seven HIV isolates in An Giang province, six were characterized as Thai subtype E and one as subtype B. Multiple logistic regression analysis showed an independent significant association between HIV seroprevalence and the following: age < or = 30 years [odds ratio (OR), 5.1; 95% confidence interval (CI), 1.7-15.2]; high frequency of sex (> 20 times per week; OR, 13.5; 95% CI, 3.6-50.2); inconsistent condom use (OR, 2.8; 95% CI, 1.01-8.0; sign of genital ulcers (OR, 18.1; 95% CI, 1.8-182); venereal warts (OR, 9.0; 95% CI, 2.5-33.0); brothels as sex venue (OR, 7.0; 95% CI, 2.0-24.3); and working at the border area (OR, 5.1; 95% CI, 2.4-11.0). Brothels as work-sites were significantly related to inconsistent condom use and the socioeconomic background of clients. Only 0.5% of CSW reported injecting drug use.
Female CSW at brothels who reported inconsistent condom use and ulcerous sexually transmitted disease, particularly in the border area with Cambodia, had greater risk of HIV infection. Brothels were more frequently used as sex venues in the border area and were more likely to be visited by occasional clients who were difficult to access. Drug use among female CSW in this region was rare. The development of prevention measures should be based on these results.
AIDS 03/1998; 12(4):425-32. · 6.24 Impact Factor
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ABSTRACT: To estimate the seroprevalence of human leptospirosis in the Mekong delta in Viet Nam, an epidemiological survey was conducted in the province of Tien Giang, which is representative of the socioeconomic activities of the region (rice growing and cattle breeding). A cross-sectional study included 35 clusters representing 1400 people randomly selected and aged 15-60 years. Sex, age, occupation, contact with animals, type of water supply, and individual habits were recorded. Leptospiral agglutinins were detected by the microagglutination test, with a battery of 22 live antigens representing the main pathogenic serogroups of Leptospira species and additional local strains. 263 sera (18.8%) gave positive results and 41 (2.9%) had a titre of agglutinins > or = 400, suggesting recent infection. No significant difference was found between females and males. The distribution of seroprevalence was homogeneous throughout the population studied, with the exception of the 15-25 years age group, in which leptospiral antibodies were less frequent. Fifteen serogroups were found, the most prevalent being Bataviae (21.7%), Panama (15.2%), Icterohaemorrhagiae (13.7%) and Australis (8.7%). No significant link between leptospiral seropositivity and professional activities or contacts with animals was found, indicating that leptospirosis in the Mekong delta may be considered as an environmentally linked disease. Leptospirosis is known to be endemic in south-east Asia, and these data demonstrated the high level of circulation of leptospires and the potential importance of leptospiral infections among the rural population in this area.
Transactions of the Royal Society of Tropical Medicine and Hygiene 92(6):625-8. · 2.16 Impact Factor
