The prevalence of viral hepatitis among the Hmong people of northern Thailand.

Sera from 269 Hmong people (102 males and 167 females, with mean age 35.4 years, range 16-63 years) were examined in order to determine the seroprevalence of hepatitis virus infection. The seroprevalence rates for HAV (hepatitis A virus), HBV (hepatitis B virus), HCV (hepatitis C virus), HDV (hepatitis D virus), HEV (hepatitis E virus), HGV (hepatitis G virus) and TTV (TT virus) infection were 87.8% (n=140), 76.0% (n=150), 2.0% (n=150), 0.7% (n=150), 6.5% (n=139), 5.3% (n=94) and 25.6% (n=121) respectively. The rate for carriers of HBV (HBsAg) was 13.8% (20.5% in males and 9.6% females) with a peak prevalence in the 21-40 year age group. A high rate of HAV seropositivity was found among the younger subjects. The rate of HEV seroprevalence was low. The prevalence of TTV-DNA was high with no difference between the sexes. HGV-RNA prevalence was low and seen primarily in males. This study indicates that the Hmong people are endemically infected with HAV and HBV infection and should be considered for targeted vaccination. The role of TTV and HGV in producing illness and hepatic disease has yet to be determined in this population.

Anti-HIV-1 antibody testing using modified gelatin particle agglutination: a large field study.

Anti-HIV testing using gelatin particle agglutination (GPA) assay was investigated in parallel with ELISAs from routine service at Siriraj Hospital. In the first strategy, 174,032 sera from a patient population with an HIV-1 seroprevalence of 13.72 per cent were assayed using reduced volumes of GPA reagents, giving a cost reduction of 40 per cent. In the second strategy, 90,560 pregnant women and 48,936 emigrant workers with an HIV-1 seroprevalence of 2.2 per cent and 0.3 per cent, respectively, were tested in pools of 4 sera using the manufacturer's recommended volumes, giving a cost saving of 67 per cent. Overall, the sensitivity and specificity were almost identical with standard methods. Thus, parallel use of either modified GPA might be considered appropriate when testing large numbers of samples. However, both modified versions of GPA are not recommended as the first assay for diagnostic or blood bank screening especially in high prevalence of HIV infection.

Analysis of neutralizing and enhancing antibodies to human immunodeficiency virus type 1 primary isolates in plasma of individuals infected with env Genetic subtype B and E viruses in Thailand.

Twenty-seven HIV-1 isolates were obtained from 51 asymptomatic HIV-1-infected pregnant women or intravenous drug users (IDUs) in Bangkok. Using heteroduplex mobility assay (HMA), it was found that the majority of the HIV-1 isolates (9 out of 11) from pregnant women belonged to genetic subtype E, whereas most of the subtype B HIV-1 isolates (15 out of 16) were isolated from IDUs. The HIV-1 isolates were tested for their susceptibility to neutralization or antibody-dependent enhancement with homologous and heterologous plasma of the two different genetic subtypes, B and E. Overall, HIV-1 neutralizing activity could be found in 37.3% of virus/plasma pairs for both subtypes B and E. No significant correlation could be identified between the two genetic subtypes (B and E) and their susceptibility to neutralization. Subtype B plasma demonstrated frequent cross-neutralization of subtype E viruses in 38.5% of virus/plasma pairs, whereas cross-neutralization activity of subtype E specific plasma samples was more limited and could cross-neutralize subtype B viruses only in 15.8% of cases. Some of the viral strains independently of their genetic subtypes were more susceptible to neutralization by plasma specific for both subtype E or subtype B, suggesting that this phenomenon is related to the proper biological properties of a viral strain. Antibody-dependent enhancement of HIV-1 strains could be detected in 12/83 (14.5%) virus-plasma pairs irrespective of genetic subtypes. Similar to neutralization results, the HIV-1 enhancing activity of plasma was mostly isolate-specific. The HIV isolates that were susceptible to neutralization were not enhanced by any plasma. On the other hand, the HIV isolates that were enhanced by plasma were resistant to neutralization in most cases. Such a dissociation between susceptibility to neutralization or enhancement may be indicative of the existence of discrete epitopes determining the two distinct viral properties.

PIP: 27 HIV-1 isolates were obtained from 51 asymptomatic HIV-1-infected pregnant women or IV drug users (IVDUs) in Bangkok. 9 of the 11 isolates from pregnant women were determined through heteroduplex mobility assay (HMA) to be of genetic subtype E, while 15 of the 16 subtype B HIV-1 isolates were from IVDUs. HIV-1 neutralizing activity was found in 37.3% of virus/plasma pairs for both subtypes B and E. No significant correlation was found between the 2 subtypes and their susceptibility to neutralization. Subtype B plasma demonstrated frequent cross-neutralization of subtype E viruses in 38.5% of virus/plasma pairs, while the cross-neutralization activity of subtype E-specific plasma samples was more limited and could cross-neutralize subtype B viruses in only 15.8% of cases. That some of the viral strains independently of their genetic subtypes were more susceptible to neutralization by plasma specific for both subtypes B and E suggests that the phenomenon is related to the proper biological properties of a viral strain. Antibody-dependent enhancement of HIV-1 strains was detected in 12 of 83 (14.5%) virus/plasma pairs irrespective of genetic subtypes. Similar to neutralization results, the HIV-1 enhancing activity of plasma was mostly isolate-specific. The HIV isolates susceptible to neutralization were not enhanced by any plasma. However, the HIV isolates which were enhanced by plasma were resistant to neutralization in most cases.