HIV-1 Langerhans' cell tropism associated with heterosexual transmission of HIV.

Heterosexual transmission by vaginal intercourse accounts for most transmission of human immunodeficiency virus-type 1 (HIV-1) in Africa and Asia but is less important in the HIV-1 epidemics of the United States and Western Europe. Epithelial Langerhans' cells (LCs) represent a possible source of initial cell contact for vaginal infection. Fifteen primary isolates of HIV-1 from U.S. homosexuals and 18 HIV-1 isolates from Thailand heterosexuals were evaluated for growth in LCs of U.S. origin. All the viruses from the Thai heterosexuals, which were subtype E, grew more efficiently in the LCs than any of the viruses from the U.S. homosexuals, which are subtype B. These results suggest that LC tropism is associated with the efficiency of heterosexual transmission of HIV.

Was the 1988 HIV epidemic among Bangkok's injecting drug users a common source outbreak?

OBJECTIVE: To describe and understand the genesis of the explosive 1988 HIV epidemic among Thai injecting drug users (IDU) in Bangkok. DESIGN: Two cross-sectional HIV seroprevalence sample surveys (SP-1 and SP-2) of drug users, including IDU at various stages of treatment. SP-1, a 10-week estimate of prevalence, was conducted by the Bangkok Metropolitan Administration (BMA) in their detoxification clinics from 5 January to 7 March 1988. SP-2 estimated prevalence in 1 week, 12-15 September 1988, in the same 18 BMA clinics. Both surveys included an administered questionnaire that gathered demographic and behavioral information. METHODS: Analysis of HIV prevalence by clinic in both SP-1 and SP-2, and the relationships between demographic data, behavioral variables, arrest history and HIV positivity in SP-1. RESULTS: Data from individual clinics in SP-1 show significant increases in HIV prevalence among IDU sampled from early February 1988. Of IDU sampled in five 'early' clinics before 9 February, 2% were positive; in the 13 'late' clinics sampled from 9 February until 7 March, 27% were positive. By September 1988, however, the early and late clinics were no longer heterogeneous for HIV prevalence. For current IDU, HIV-positivity was associated with the sharing of injection equipment in SP-1 [odds ratio (OR), 1.82; 95% confidence limits (CL), 1.31-2.53] and recent jail or prison stay (OR, 2.15; 95% CL, 1.18-3.98). CONCLUSIONS: The behavioral factors associated with the HIV epidemic among Bangkok's IDU are similar to those described elsewhere. The monthly incidence of 5% from February to September 1988 suggests extensive needle or injection equipment sharing networks among IDU in Bangkok. Additionally, the pattern of HIV-positivity by detoxification clinic over time in early 1988, and then in September 1988 is consistent with a relationship to the prison amnesty of early December 1987. Shortly after that date, an undisclosed number of former IDU, a substantial number of whom were still injecting, and may have become HIV-positive while in custody, returned to resume injecting within existing drug-using networks throughout Bangkok and elsewhere in Thailand.

PIP: This study was undertaken to describe and understand the genesis of the 1988 HIV epidemic among Thai IV drug users (IVDU) in Bangkok. Two cross-sectional HIV seroprevalence sample surveys were conducted of drug users at various stages of treatment at Bangkok Metropolitan Administration (BMA) detoxification clinics. The first survey was a 10-week estimate of HIV prevalence over the period of January 5 to March 7, 1988, involving 1649 drug users who volunteered to give samples of their blood. The second stage survey estimated prevalence over the period September 12-15, 1988, in the same 18 BMA clinics. 1811 drug users volunteered their blood for this latter survey assessment. The monthly incidence of 5% during February-September 188 suggests the existence of extensive needle or injection equipment sharing networks among IVDUs in Bangkok. Moreover, the pattern of HIV-positivity by detoxification clinic over time in early 1988 and in September is consistent with a relationship to the prison amnesty of December 1987 in which an undisclosed number of former IVDUs returned to resume injecting drugs in Bangkok and elsewhere in Thailand.

Why do HIV-1 subtypes segregate among persons with different risk behaviors in South Africa and Thailand?

PIP: Initial research on the genetic variability of human immunodeficiency virus (HIV)-1 has indicated that HIV-1 envelope subtype B is dominant in Western countries where homosexuality and injecting drug use are the major risk factors, while env subtypes A, C, D, and E predominate in Africa and Asia where most transmission is heterosexual. Data from South Africa and Thailand suggest that, due to limited mixing of population subgroups, largely independent HIV epidemics caused by different genotypic subgroups may co-exist in a given geographic area. On the other hand, the possibility that HIV-1 subtypes differ in transmission efficiency by exposure mode also has some support. For example, subtypes E and C appear to be better adapted to penile-vaginal transmission, while subtypes B, E, and C may be transmitted efficiently through blood. Factors such as sexual mixing patterns (e.g., commercial sex work) and the prevalence of sexually transmitted diseases must also be considered when examining HIV-1 subtype transmission differences. The use of new assays that allow for the accurate measurement of viral levels in plasma, semen, and genital secretions should complement epidemiologic estimates of transmission efficiency for various HIV-1 subtypes.^ieng

Determination of HIV-1 subtypes in injecting drug users in Bangkok, Thailand, using peptide-binding enzyme immunoassay and heteroduplex mobility assay: evidence of increasing infection with HIV-1 subtype E.

OBJECTIVES: To evaluate the sensitivity and specificity of peptide-binding enzyme immunoassay (PEIA) and heteroduplex mobility assay (HMA) for the determination of HIV-1 subtypes B and E; to determine the proportions of infections due to subtypes B and E over time; and to generate data on DNA sequences of the C2-V3 region of the env genes. METHODS: HIV-1 subtyping was conducted by PEIA and HMA on blood specimens obtained from 97 injecting drug users (IDU) infected with HIV between 1988 and 1993. Genetic sequencing was performed on 84 specimens. RESULTS: Both laboratory methods were highly sensitive and specific for the determination of HIV-1 subtypes B and E. The two tests were complementary; samples which could not be typed by HMA were correctly typed by PEIA and vice versa. While subtype B accounted for 80.4% (78 out of 97) of infections overall, the proportion of new infections due to subtype E increased from 2.6% (one out of 38) in 1988-1989 to 25.6% (11 out of 43) in 1990-1991, and to 43.8% (seven out of 16) in 1992-1993 (chi 2 for linear trend, P < 0.001). CONCLUSIONS: HMA and PEIA are practical, sensitive and specific laboratory methods for the determination of HIV-1 subtypes in Thailand, and may be useful in other geographic areas to define the molecular epidemiology of the global HIV-1 pandemic. Data suggest that the proportion subtype E infections have increased among Bangkok IDU from 1988 through 1993.

The evolving molecular epidemiology of HIV-1 envelope subtypes in injecting drug users in Bangkok, Thailand: implications for HIV vaccine trials.

OBJECTIVE: To genetically characterize HIV-1 strains in injecting drug users (IDU) in Bangkok, Thailand in 1994, and compare these with strains found earlier in Thai IDU; such information is essential for HIV-1 vaccine development and evaluation. METHODS: Peripheral blood mononuclear cells were collected from 84 IDU attending 14 drug treatment clinics in Bangkok in 1994. DNA was amplified using a nested polymerase chain reaction (PCR) procedure and sequenced directly (without cloning) from the PCR products. The V3 and flanking regions (345 nucleotides) of the env gene were analyzed using a neighbor-joining tree. RESULTS: Only one (1%) strain was a typical subtype B virus, 69 (82%) were genetically distinct subtype B' viruses (Thai B), and 14 (17%) were subtype E strains (Thai A). Persons with recently acquired infection were more likely to have subtype E viruses (P < 0.001) than those in our 1991 survey, who were more likely to have subtype B' viruses. Pairwise intra-subtype differences within subtypes E and B' were 5.3 and 4.3%, respectively, compared with 3.4 and 3.5% among strains collected in 1991 in Thailand. CONCLUSION: The genetic diversity within subtypes B' and E in Thailand and the proportion of new infections due to subtype E viruses among Bangkok IDU are increasing significantly. These data highlight the importance of monitoring the molecular epidemiology of HIV-1 in populations being considered for HIV-1 vaccine trials.

The epidemiology of HIV infection and AIDS in Thailand.

PIP: There were very few AIDS cases reported in Thailand as of 1988, where HIV was introduced relatively late in the course of the AIDS pandemic. Thailand was therefore classified as an epidemiologic pattern III country with regard to the HIV/AIDS pandemic. Also in 1988, however, Thailand experienced a major and rapid increase in HIV prevalence among IV drug users (IVDU). The Thai experience with HIV after the rapid spread first among IVDUs has been successive waves of HIV transmission to female prostitutes, then to their non-IVDU male clients, and then into the non-prostitute wives and girlfriends of these latter men in the general population. Three years after being declared a pattern III country, 300,000 people in Thailand were estimated to be infected out of a population of 55 million. Reasons for this unprecedented rapid spread of HIV infection may eventually come from research on sexual behavior and related diseases given the lack of evidence for human host genetic factors or particularly virulent etiologic agent factors to explain the phenomenon. The reason and dynamics behind the timing and rapidity of the 1988 epidemic among IVDUs for now remains unknown. The authors note that the scenario of HIV transmission observed in Thailand also seems to be unfolding in neighboring countries. HIV infection among female prostitutes and heterosexual men is consistently highest in the northern Thai provinces adjacent to Myanmar and Laos. This paper reviews the epidemiology and prevention of HIV infection and AIDS in Thailand, updating previous reports and commentary, and including previously unpublished or not widely available data.^ieng

Viral load differences in early infection with two HIV-1 subtypes.

OBJECTIVES: Information on early HIV-1 infection has come primarily from studies of persons infected with subtype B in North America and Europe; much less is known about other subtypes. The purpose of the present study was to compare the virologic and immunologic parameters following seroconversion among recently-infected persons infected with either of two different HIV-1 subtypes. METHOD: A prospective cohort study was carried out at methadone treatment clinics administered by the Bangkok Metropolitan Administration, Thailand. A total of 130 HIV-1-infected seroconverters (103 with HIV-1 subtype E and 27 with subtype B) were included in the study. The main outcome measures were serial HIV-1 RNA viral load, natural killer cell percentage, CD4 and CD8 lymphocyte counts since seroconversion. RESULTS: The demographic and behavioral characteristics of persons with either subtype were similar. Median RNA viral levels at the earliest time within 3 months of seroconversion were more than three times higher for persons infected with subtype E than subtype B (63 100 versus 18 050 copies/ml, P = 0.001). However, this difference decreased over time such that viral loads were similar at 12, 18, and 24 months following seroconversion. The CD4 and CD8 lymphocyte counts were similar in infections with either subtype during the entire period up to 24 months post-seroconversion. CONCLUSIONS: Higher viral loads associated with subtype E may result from inter-subtype biological differences; however, the epidemiological dynamics of transmission in Bangkok may have also contributed to this phenomenon.

Continued high HIV-1 incidence in a vaccine trial preparatory cohort of injection drug users in Bangkok, Thailand.

BACKGROUND: A large epidemic of HIV-1 subtype B began among injection drug users (IDUs) in Bangkok in 1988. Despite ongoing prevention efforts, HIV-1 prevalence among IDUs remained at 30-50% through the 1990s. OBJECTIVES: To measure the incidence of HIV-1 infection and related risk factors to guide prevention efforts and to evaluate the feasibility of conducting an HIV vaccine efficacy trial. DESIGN AND METHODS: A prospective cohort study in which IDUs attending methadone treatment programs in Bangkok were screened during 1995-1996 for enrollment into the study. IDUs found to be HIV-seronegative on two occasions were offered enrollment with follow-up visits every 4 months. On each visit participants were evaluated with a questionnaire and serologic testing. RESULTS: A total of 1209 HIV-negative IDUs were enrolled. Through the end of 1998, the overall HIV-1 incidence rate was 5.8 (95% confidence interval, 4.8-6.8) per 100 person-years of follow-up. HIV-1 subtypes E and B accounted for 79 and 21% of infections, respectively. On multivariate analysis, HIV-1 seroconversion was primarily associated with the frequency of heroin injection, the sharing of injection equipment, and incarceration, especially with drug injection. Sexual behavior was not associated with increased risk for HIV-1. Risk factors for infection with HIV-1 subtypes E and B were similar. CONCLUSION: HIV-1 transmission risk remains high among Bangkok IDUs despite methadone treatment and other current prevention strategies. There is an urgent need to address this ongoing epidemic, especially in jails and prisons. This study led to the initiation in 1999 of a phase III HIV-1 vaccine efficacy trial in this population.

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.

Sequence analysis of an HIV type 1 env subtype E isolate from Thailand with discordant V3-loop serotyping.

PIP: HIV-1 genetic subtypes B and E are currently circulating in Thailand. Subtype E accounts for more than 90% of heterosexual transmission nationwide, while subtype B is transmitted mainly among IV drug users. This paper reports an HIV-1 Thai E isolate which yielded discordant results in serotyping and genotyping assays. An HIV-1-infected mother enrolled in Bangkok in a perinatal transmission study was identified independently as subtype B by V3 serotype by St. Mary's and HIV/AIDS Collaboration laboratories using different in-house assays. Her plasma was also screened for other HIV-1-specific immune responses, yielding a pattern of antibody reactivity similar to other subtype E sera. The genetic subtype of the isolate was identified by heteroduplex mobility assay (HMA) to further characterize it. Analysis results suggest that the woman was infected with HIV-1 subtype E. The env region encoding C2-V3 was subsequently sequenced to clarify the discordant results between the V3 serotype B and the genetic subtype E.^ieng

Syncytium-inducing and non-syncytium-inducing capacity of human immunodeficiency virus type 1 subtypes other than B: phenotypic and genotypic characteristics. WHO Network for HIV Isolation and Characterization.

Positively charged amino acid substitutions at positions 11 and 25 within the loop of the third variable region (V3) of HIV-1 subtype B envelope have been shown to be associated with the syncytium-inducing (SI) phenotype of the virus. The present study was designed to examine SI and NSI-associated V3 mutations in HIV-1 subtypes other than B. HIV-1 RNA was isolated from 53 virus stocks and 26 homologous plasma samples from 53 recently infected individuals from Brazil, Rwanda, Thailand, and Uganda. The C2-V3 region of the viral envelope was converted to cDNA, amplified, and sequenced. Of 53 primary virus stock samples 49 were biologically phenotyped through measurement of the syncytium-inducing capacity in MT-2 cells (to differentiate between SI and NSI phenotypes). In addition, after passage of primary isolates through PHA stimulated donor PBMC, the replication capacity was determined in U937-2, CEM, MT-2, and Jurkat-tat cell lines (to differentiate rapid/high and slow/low phenotypes). According to the sequence analysis 9 (17.0%) of the viruses belonged to subtype A, 15 (28.3%) to subtype B, 1 (1.9%) to subtype C, 13 (24.5%) to subtype D, and 15 (28.3%) to subtype E. Sequence analysis of virus RNA, obtained from 26 homologous plasma samples, confirmed the homogeneity of sequence populations in plasma compared to primary virus isolates. Of the 49 viruses tested 12 had the SI phenotype, 5 were confirmed to be rapid/high, and 4 appeared to be slow/low pattern 3 replicating. Of 49, 29 had the NSI phenotype, 24 were confirmed to be slow/low pattern 1 or 2, and 3 appeared to be slow/low pattern 3 replicating. Analysis of mutations at V3 loop amino acid positions 11 and 25 revealed that 10/12 (83.3%) of the SI viruses had SI-associated V3 mutations and that 28/29 (96.6%) of the NSI viruses lacked these mutations. V3 loop heterogeneity, length polymorphism, and a high number of positively charged amino acid substitutions were most frequently found among subtype D variants. These results indicate that both the phenotypic distinction between SI and NSI viruses and the association of biological phenotype with V3 mutations is present among HIV-1 subtypes other than B.

AIDSVAX (MN) in Bangkok injecting drug users: a report on safety and immunogenicity, including macrophage-tropic virus neutralization.

A randomized, double-blind, placebo-controlled phase I/II study of AIDSVAX (MN) was conducted among injecting drug users in Bangkok, Thailand. Four doses of vaccine (300 microg of MN-rgp120 in alum) or placebo (alum) were given at study entry and at 1, 6, and 12 months. The objectives of the study were to evaluate (1) the feasibility of conducting vaccine trials in this population; (2) the safety of this candidate AIDS vaccine; and (3) the immunogenicity of this vaccine. Thirty-three volunteers (22 vaccine and 11 placebo recipients) were recruited. None were lost to follow-up during the 18-month study. Mild reactogenicity was noted, which was similar in both vaccine and placebo recipients. The vaccine induced anti-HIV-1 antibody in all vaccine recipients. Maximal titers of binding antibodies of MN-rgp120 and the V3 domain of MN-rgp120 were induced after the third (6 month) dose while maximal neutralizing antibodies followed the fourth (12 month) dose. The vaccine-induced antibodies from several volunteers were capable of neutralizing macrophage-tropic, subtype B viruses (301660 and JRCSF) detected in a PBMC-based assay. Binding and neutralizing antibodies declined about 10-fold in the 6 months after the last boost. Two vaccinees became infected during the trial, both with subtype E viruses. A phase III efficacy trial, using a bivalent gp120 vaccine containing antigens from a subtype B virus (MN) and a subtype E virus (A244), was initiated in March 1999 in injecting drug users in Bangkok.

Genetic characterization of incident HIV type 1 subtype E and B strains from a prospective cohort of injecting drug users in Bangkok, Thailand.

We obtained specimens from 128 HIV-1 seroconverters identified from 1995 through 1998 in a prospective cohort study of 1,209 HIV-negative injecting drug users (IDUs) in Bangkok, Thailand. Epidemiologic data indicated that parenteral transmission accounted for nearly all infections. HIV-1 DNA from the C2-V4 env region was sequenced, and phylogenetic analyses determined that 102 (79.7%) of the specimens were subtype E and 26 (20.3%) subtype B strains. All subtype B strains clustered with strains often referred to in previous studies as Thai B or B'. The interstrain nucleotide distance (C2-V4) within subtype E strains was low (mean, 6.8%), and pairwise comparisons with a prototype subtype E strain, CM244, showed limited divergence (mean, 5.6%). The subtype B stains showed greater interstrain divergence (mean, 9.2%) and were significantly divergent from the prototype B strain HIV-MN (mean, 13.0%; p < 0.0001). The subtype E strains had significantly lower mean V3 loop charge than did subtype B strains (p = 0.017) and, on the basis of analysis of amino acid sequences, were predicted to be predominantly (91%) non-syncytium-inducing (NSI), chemokine coreceptor CCR5-using (CCR5+) viruses. The subtype B strains had a higher mean V3 loop charge, and a smaller proportion (23%) were predicted to be NSI/CCR5+ viruses. This study demonstrates that most incident HIV1 infections among Bangkok IDUs are due to subtype E viruses, with a narrow spectrum of genetic diversity. The characterization of incident HIV-1 strains from 1995 to 1998 will provide important baseline information for comparison with any breakthrough infections that occur among IDUs in Bangkok who are participating in an HIV-1 vaccine efficacy trial initiated in 1999.

Sendai virus-based production of HIV type 1 subtype B and subtype E envelope glycoprotein 120 antigens and their use for highly sensitive detection of subtype-specific serum antibodies.

We previously described a Sendai virus (SeV)-based expression system for the recombinant gp120 of HIV-1 subtype B (rgp120-B), which has permitted the production of antigenetically and functionally authentic gp120 at a concentration as high as 6 microg/ml of culture supernatant (Yu D et al.: Genes Cells 1997;2:457-466). Here the same procedure was successfully applied to the production of HIV-1 subtype E gp120 (rgp120-E). The remarkable production of the proteins by the SeV expression system enabled us to use crude culture supernatants for serological and functional studies of gp120s. The immunological authenticity of rgp120-E was verified by patient sera and anti-V3 loop monoclonal antibodies specific for HIV-1 subtypes B and E. CD4-binding properties were corroborated by FACS analyses. The rgp120s were then used in an enzyme immunoassay (rgp120-EIA) to detect antibodies in the sera of HIV-1-infected individuals, and the performance was assessed in comparison with a conventional V3 loop peptide EIA (V3-EIA). The initial evaluation of a serum panel (n = 164) consisting of 76 subtype E and 88 subtype B sera revealed that the rgp120-EIA was nearly 1000-fold more sensitive than the V3-EIA and was able to detect subtype-specific antibody with 100% sensitivity and with a complete correlation with the genotypes, whereas the V3-EIA failed to detect 9 and 24% of the same subtype E and B sera, respectively. Furthermore, a study employing a panel of 28 international sera with known genotypes (HIV-1 subtypes A through F) confirmed the remarkable specificity of this method. An EIA reactivity higher than 1.0 was an unambiguous predictor of HIV-1 subtype E and B infections. The data imply the presence of strong subtype-specific epitopes for antibody bindings to these rgp120s.

Genetic similarity of HIV type 1 subtype E in a recent outbreak among injecting drug users in northern Vietnam to strains in Guangxi Province of southern China.

To investigate the molecular epidemiology of a recent HIV-1 outbreak in northern Vietnam and its relation to the epidemic in surrounding areas, we analyzed 17 HIV-positive blood specimens from 3 heterosexuals, 2 sexually transmitted disease patients, and 12 injecting drug users (IDUs), collected in 4 provinces near Hanoi in 1998. These were compared with the specimens from Ho Chi Minh City (n = 10) and An Giang Province (n = 10) in southern Vietnam and with published sequences from neighboring countries. Genetic subtyping based on the env C2/V3 sequences revealed that HIV-1 subtype E predominated throughout Vietnam in all risk populations; the exception was one typical United States-European-type HIV-1 subtype B detected in a patient in Ho Chi Minh City, the first case of HIV infection identified in Vietnam in 1990. The HIV-1 subtype E sequences identified in 9 of the 12 IDUs from northern provinces were closely related phylogenetically to those in IDUs in nearby Guangxi Province of China, and also shared a common amino acid signature downstream of the env V3 loop region. The low interperson nucleotide diversity among IDUs in northern Vietnam supports the view that HIV-1 subtype E was introduced recently among IDUs in northern Vietnam. These data indicate a linkage between HIV-1 circulating among IDUs in northern Vietnam and southern China, and suggest recent transborder introductions as the likely source of HIV-1 subtype E in northern Vietnam.

HIV-1 variants in South and South-East Asia.

HIV spread in South and South-East Asia is most alarming, and genetic variability of HIV-1 is an important consideration in vaccine development. In this study, we examined the third variable (V3) region of env gene of HIV-1 variants prevalent in Thailand, Malaysia, India, and the Philippines. By phylogenetic tree analyses, an HIV-1 variant from an injecting drug user (IDU) in Thailand belonged to subtype B, and HIV-1 variants from 2 IDUs in Malaysia were classified into 2 subtypes, B and E. One HIV-1 variant from a male homosexual in the Philippines belonged to subtype B. Out of 8 HIV-1 variants from sexually transmitted disease patients in India, 7 belonged to subtype C, and one to subtype A. Although the total number of individuals examined in this study was limited, 4 HIV-1 subtypes were found in South and South-East Asia and large international movements of HIV-1-infected individuals in this region could induce global dissemination of these HIV-1 variants.

Immunopathology of acute rheumatic fever and rheumatic heart disease. The demonstration of Coxsackie group B viral antigen in the myocardium.

Immunopathologic studies were performed on heart tissue of patients with acute rheumatic fever with carditis and chronic rheumatic heart disease. Coxsackie group B viral antigen was demonstrated in 3 heart specimens of patients clinically compatible with active rheumatic fever. In two of these the pathologic findings were compatible with acute rheumatic carditis. Immunoglobulin was detected in 2 and complement in one of these heart specimens. All of the chronic rheumatic heart specimens and the controls were negative. These findings suggested that Coxsackie group B virus may be etiologically related to the pathogenesis of acute rheumatic fever.

The effect of interferon on Japanese encephalitis virus in vitro.

The studies on the effect of the Recombinant Leukocyte A Interferon (r IFN-alpha A) on 4 local strains of JE virus in Thailand were performed in vitro in our laboratories in Bangkok during August - October 1984. The procedures consisted of the plaque reduction assay and the Rhesus monkey kidney cell line, LLC-MK2 cells. These 4 strains namely Vip, KE-093, KE-094 and KE-095 were isolated from the JE patients in Thailand during 1983-1984. The results revealed that all of the JE virus strains tested were sensitive to the r IFN-alpha A with its minimal effective doses ranging from 30 I.U./ml to 1,500 I.U./ml. The studies on the effects of r IFN-alpha A on JE virus replicating in the cell culture for 0 hour, 1 hour and 6 hours indicated that if the virus had more hours to replicate in the cell culture, higher concentration of the IFN was needed in order to combat the replication of the virus in the cell culture. r IFN-alpha A at higher concentrations showed more efficacy in combating the replication of the JE virus in vitro.

Detection of varicella-zoster antibody by immune adherence hemagglutination test.

The immune adherence hemagglutination (IAHA) is a more sensitive and specific test for evaluation of humoral immunity to varicella-zoster virus (VZV) than a conventional complement fixation (CF) test. The equipment, reagents, procedure used in the IAHA are basically the same as those employed in the CF test. After VZ vaccination, seroconversions detected by IAHA test were significantly greater than those by CF test (P less than 0.01, chi 2 test). Moreover, the IAHA titers were higher about 4 times (G.M. 30.9 vs 8.2) and persisted longer than CF titers. Although the IAHA antigen is not a commercial product, the IAHA is sensitive and suitable assay for VZ antibody determination in routine serological laboratory.

The effect of interferon on flaviviruses in vitro: a preliminary study.

The preliminary results of our study in vitro on the effect of Interferon on Flaviviruses showed that Interferon alpha and Interferon beta were more effective on JE viruses Vip local strain and JaGAr strain, but less on Dengue virus type 2 strain. However, the effect of these 2 interferons on the 2 strains of JE viruses were still variable which need further investigations. The JE virus Vip local strain seemed to be more susceptible to interferon than the Japanese prototype JaGAr strain. Thus, the in vivo trial on JE disease in Thailand is strongly recommended.