Kinetics of the antibody response to seasonal influenza vaccination among the elderly.

Influenza vaccination, which has been targeted to the elderly and those at serious risk of complications, is recommended. The purpose of this study was to determine antibody responses after influenza vaccination among Thai elderly persons living in the community. A total of 591 subjects consisting of 308 vaccinees and 283 non-vaccinees were enrolled in the study. Antibodies to H1N1, H3N2, and B viruses were detected by hemagglutination inhibition (HI) testing. The numbers of subjects who had protective antibody titers ≥40 and geometric mean titers (GMTs) of antibodies against A(H1N1), A(H3N2), and B viruses prior to vaccination were similar for the vaccine and placebo groups. The seroprotection rates and GMTs for influenza virus A(H1N1), A(H3N2), and B strains after influenza vaccination at 1, 5, and 12 mo in the vaccine group were significantly higher than those in the placebo group. The seroprotection rates for the A(H1N1) and A(H3N2) strains, but not the B strain, met Committee for Proprietary Medicinal Products (CPMP) criteria (>60%). GMTs and seroprotection rates against influenza B strain in the vaccinees at all time points were <40% and <60%, respectively, and significant differences between the vaccinees and the placebo controls were observed. The GMTs and seroprotection rates for influenza strains in those with pre-existing antibody titers ≥40 were significantly higher than those in the group with pre-existing antibody titers <40. These findings demonstrated that the elderly living in the community developed adequate antibody responses with sustainable titers throughout the 12-month study period after influenza vaccine immunization. Moreover, the presence of pre-existing antibody at a titer ≥40 prior to vaccination strongly affected the antibody response to influenza vaccination.

Occult hepatitis B virus infection in Thai blood donors.

BACKGROUND: An evaluation by the National Blood Center, the Thai Red Cross Society, of two commercial multiplex nucleic acid tests (NATs; the Chiron PROCLEIX ULTRIO test and the Roche Cobas TaqScreen MPX test) for screening Thai blood donors for hepatitis B virus (HBV), hepatitis C virus, and human immunodeficiency virus Type 1 identified 175 HBV NAT-reactive/hepatitis B surface antigen (HBsAg)-negative donors. The classification of the HBV infection of these donors was confirmed by follow-up testing. STUDY DESIGN AND METHODS: Index samples were tested for HBV serologic markers and HBV viral loads were determined. Donors were followed for up to 13 months and samples were tested with both NAT assays and for all HBV serological markers. RESULTS: Of 175 HBV NAT-yield donors, 72 (41%) were followed. Based on the follow-up results, the majority of donors who were followed had an occult HBV infection (66.7%), followed by donors with a primary, acute infection (26.4%). The majority of donors in this latter group (20.8%) were in the window period. Three donors (4.2%), who were anti-HBs positive, had a reinfection or breakthrough infection. CONCLUSION: The majority of donors detected during routine screening, who were HBsAg negative and NAT reactive, had an occult HBV infection, thus validating the decision to introduce NAT for blood donations in Thailand.

Antibody response to an eight-site intradermal rabies vaccination in patients infected with Human Immunodeficiency Virus.

OBJECTIVE: To investigate the rabies virus neutralizing antibody response in HIV-1-infected patients with CD4+ cell count 200 cells/microL after post-exposure prophylaxis using an eight-site intradermal rabies vaccination regimen. METHODS: In a prospective cohort study, 27 HIV-1 infected patients were recruited, none of which had a history of rabies vaccination. All patients provided informed consent and were separated into two groups according to their CD4+ cell count (patients with CD4+ counts of 200 cells/microL). All patients received Purified Chick Embryo Cell rabies Vaccine (PCECV) using a modified eight-site regimen in which 0.1 mL of vaccine was injected intradermally on each of days 0, 3, 7, 14, and 30 (8-8-8-8-8). CD4+ cell counts, HIV-1 viral load and rabies virus neutralizing antibody (RVNAb) concentrations as determined by the Rapid Fluorescent Focus Inhibition Test (RFFIT) were evaluated on blood samples taken on days 0, 3, 7, 14, 30, 90, 180 and 365 after vaccination. RESULTS: Of the 27 patients included in the study, 18 patients (67%) had CD4+ cell counts of >200 cells/microL and 9 patients (33%) had CD4+ counts of or=0.5 IU/mL). There was no statistically significant difference in RVNAb concentrations between the two groups on days 3, 7, 14, 30, 90, 180 and 365 after vaccination. CONCLUSION: PCECV is immunogenic in HIV-1-infected patients with CD4+ cell counts below 200 cells/microL when administered in a modified eight-site intradermal PEP regimen.

One-year experience of nucleic acid technology testing for human immunodeficiency virus Type 1, hepatitis C virus, and hepatitis B virus in Thai blood donations.

BACKGROUND: Blood donations collected at the National Blood Center, the Thai Red Cross Society, Bangkok, in 2007 were tested by nucleic acid amplification technology (NAT) using the Chiron TIGRIS/Procleix Ultrio test and the Roche cobas s 201/cobas TaqScreen multiplex (MPX) test. STUDY DESIGN AND METHODS: The sensitivity, specificity, and robustness were determined by testing 486,676 seronegative blood donations. Samples from each day of collection were divided into two sets; the odd-numbered samples were tested individually on the TIGRIS and the even-numbered samples were tested in pools of 6 on the cobas s 201. The status of reactive samples was confirmed by duplicate testing of samples from the plasma bag to calculate the test specificity. Reactive samples were tested on the alternate system and followed up. RESULTS: The analytical sensitivity of both systems met the 95% limits of detection claimed by the respective package inserts. No cross contamination was seen with either system. Test specificity was 99.93 and 99.90% for the Procleix Ultrio and cobas TaqScreen tests, respectively. The NAT yield rates for human immunodeficiency virus Type 1 (HIV-1), hepatitis C virus (HCV), and hepatitis B virus (HBV) were 1:97,000, 1:490,000, and 1:2800, respectively. Several occult HBV donors, the majority of whom were detected by both tests, were also identified. The HIV-1 and HCV window cases were detected with both tests. CONCLUSION: The performances of the systems and tests indicated that both were acceptable for routine NAT by the National Blood Center, the Thai Red Cross Society. However, the Procleix Ultrio test appeared to be less sensitive than the cobas TaqScreen test for HBV.

Serum levels of MIP-1beta and RANTES in HIV-1 subtype CRF01_AE infected patients with different rates of disease progression.

The beta-chemokines have been shown to inhibit HIV replication in vitro. To evaluate the role of serum beta-chemokines in disease progression and their anti-viral role in vivo, we determined serum levels of macrophage inflammatory protein-1beta (MIP-1beta) and regulated upon activation normal T-cell expressed and secreted (RANTES) of twenty HIV-1 subtype CRF01_AE infected patients: nine progressors (PRs, follow-up CD4+ cell count < 200/mm3 and progression to AIDS or death) and eleven slower progressors (SPs, asymptomatic and/or follow-up CD4+ cell counts > 350/mm3 at the end of follow-up) and determined their plasma viral loads. The subjects were followed for at least 36 months. All had initial CD4 values > 350 cells/mm3. In this longitudinal study, serum levels of MIP-1beta and RANTES in specimens obtained either early or later in the course of HIV infection did not differ significantly between progressors and slower progressors (p > 0.05). There were no significant changes in serum MIP-1beta and RANTES levels over time in either patient group (p > 0.05). No significant associations were observed between plasma viral loads and the measured beta-chemokines (r = -0.205, p = 0.21 for MIP-1beta and r = -0.12, p = 0.492 for RANTES). The results suggest these chemokines do not play a major systemic role in control of viremia or protection against the progression of HIV disease.

The prevalence and persistence of human parvovirus B19 infection in thalassemic patients.

Human parvovirus B19 infection was studied in 60 thalassemic patients in Thailand. Seroprevalence, persistence of parvovirus B19 and their genotypes were identified in blood samples. Prevalence of anti-parvovirus B19 IgG and DNA found in thalassemic patients were 38% and 13%, respectively. Anti-parvovirus B19 IgM could be detected in 4% of these positive anti-parvovirus B19 IgG patients. The seroprevalence and parvovirus B19 DNA in patients with a history of blood transfusion were not significantly higher than those without such a history (44% vs. 34% and 20% vs. 9%, respectively). Phylogenetic analysis of NS1 nucleotide sequences of three parvovirus B19 samples revealed that they were parvovirus B19 genotype 1. They showed low genetic diversity from prototype (Au) strain. We concluded that acute and chronic persistent parvovirus B19 infection were found in the thalassemic Thai patients. Chronic persistence of parvovirus B19 infection might play important clinical role in thalassemic patients because of the high prevalence of parvovirus B19 DNA. Blood transfusion had no significant influence to increase the prevalence of parvovirus B19 infection in thalassemic patients.

Attenuating characteristics of DEN-2 PDK53 in flavivirus-naïve peripheral blood mononuclear cells.

A live-attenuated DEN-2 virus, DEN-2 strain 16681-PDK53, has been found to be attenuated for both humans and mice with an unknown mechanism. To partially answer this question, responses of flavivirus-naïve primary human PBMC to infection with attenuated DEN-2 PDK53 (D2/IC-VV45R) virus and its parental, virulent DEN-2 16681 virus (D2/IC-30P-A) were investigated at the cellular and genetic levels using cDNA array analysis. Both DEN-2 viruses produced similar replication kinetics in flavivirus-naïve PBMC. In contrast, virulent DEN-2 virus caused a higher percentage of apoptotic death. A macro-array analysis showed that the virulent D2/IC-30P-A virus induced changes in the expression of a greater number of genes than did the attenuated D2/IC-VV45R virus, 31 genes versus 19 genes, respectively, by 24 h post-infection. Interestingly, both viruses stimulated cytokines known to be virulence factors for DEN virus infection, such as IL-1beta, IL-6, IL-8, IL-10, MIP-1beta, and MIP-1alpha. The virulent virus additionally up-regulates immune suppression factors and down-regulates immune activator and growth factors. In conclusion, our data demonstrated that D2-PDK53 effected less change in PBMC than D2-16681 in terms of observable cellular effect and expression of cytokine and chemokine related genes.

Trends of HIV seropositivity at Siriraj Hospital: 13 year's observation from 1992-2004.

OBJECTIVE: The aim of the present report was to observe the trend of seroprevalence rates of HIV seropositivity for routine services at Siriraj Hospital for 13 years. MATERIAL AND METHOD: The prevalence rate of HIV seropositivity was analyzed in three groups of subjects: 1) patients who attended the hospital with HIV related diseases; 2) pregnant women at first visit to the antenatal care clinic; 3) emigrating workers who have applied for employment in foreign countries. RESULTS: Of the 13 year-observation, HIV seroprevalence rates in the groups of patients, pregnant women and emigrating workers was 10.6% (95%CI 8.9-12.3%), 2.0% (95%CI 1.8-2.2%) and 0.6% (95%CI 0.4-0.8%), respectively. CONCLUSION: The low prevalence of HIV seropositivity in the group of emigrating workers may be due to self selection, whereas the prevalence in pregnant women, which was rather consistent at about 2.0%, may represent the infection rate in the general population. The seroprevalence rate measured in the group of pregnant women demonstrates that Thailand should increase efforts to confine the spread of HIV infection in the community.

HBsAg diagnostic kits in the detection of hepatitis B virus mutation within "a" determinant.

The performance of currently available hepatitis B surface antigen (HBsAg) commercial kits was analyzed by using a panel of 212 well-characterized plasma donors all over the country and a panel of nine recombinant HBsAg mutants containing single point or combinations of mutations between amino acid residues 124 and 147 of the "a" determinant. HBsAg commercial kits in this study were machine-based immunoassays with a one-step sandwich ELISA method using either an automatic closed system or manual system. The sensitivity of all machine-based assays evaluated with 105 HBsAg plasma panels was 100% (95% CL = 95.6-99.9%), whereas the specificity with 107 HBsAg negative plasma ranged from 99.07% to 100% (95% CL = 94.2-99.9%). The relative performance of these kits to detect the hepatitis B virus (HBV) mutant panel members of the "a" determinant was found to differ. Interestingly, any commercial kits with monoclonal antibody capture and polyclonal antibody detection (mono/poly), but not mono/mono Ab capture and detection, could pick up the common HBsAg Gly145Arg mutant either solely or in combination with other mutations within the "a" determinant. New versions of HBsAg test kits should recognize multiple HBsAg epitopes in order to detect mutant HBsAg, together with providing good analytical sensitivity and specificity, because of the importance of these assays in HBV diagnosis and in protecting the safety of the blood supply.

Increased HIV-DNA load in CCR5-negative lymphocytes without viral phenotypic change.

We have previously described a selective increase in HIV-DNA content in CCR5-negative lymphocytes from late stage HIV-infected patients. Here, we show that this increase occurred even in the absence of viral phenotypic switching from CCR5- to CXCR4-tropic. This leads us to hypothesize that early and late CCR5-tropic viruses might be different in the ability to infect CCR5-low or -negative cells. We compared a set of early CCR5-tropic viruses with low viral DNA content in CCR5-negative cells to a set of late CCR5-tropic viruses with high viral DNA content in CCR5-negative cells. We could not find any significant differences between the two sets of viruses in the aspects of relative infectivity in CCR5-low cells and the level of inhibition by beta-chemokine. This suggested that there may be some changes in cellular phenotype or environment that allows an expansion of susceptible cell population in late stages HIV infection. Understanding these changes may provide a novel approach for HIV therapy.

HIV-1 subtyping using gag/env heteroduplex mobility assay and peptide enzyme-linked immunosorbent assay.

Two HIV-1 subtypes have accounted for virtually all infections in Thailand: subtype B', found mainly in injection drug users (IDUs), and CRF01_AE (initially subtype E), found in over 90% of sexually infected persons and increasingly in IDUs in recent years. During 1997-1998, 227 blood samples were collected from HIV-1 infected individuals consisting of 92 mothers, 35 children and 100 IDUs. The blood samples were subtyped by heteroduplex mobility assay (HMA) and peptide enzyme-linked immunosorbent assay (PEIA). Using gag and env HMA, CRF01_AE and subtype B' accounted for 96-97% and 3-4% of both the mothers and the children, respectively. In the IDU group, 10% of the plasma samples could only be performed by gag HMA and gave the result as CRF01_AE. CRF01_AE and subtype B' using PEIA accounted for 67% and 33% of the IDUs. There was 100% concordance of the results between gag HMA and env HMA. Ninety-five percentages of concordant results were observed between HMA and PEIA. Of the 6/134 (5%) subjects with discordant results, nucleotide sequencing, used as a gold standard, confirmed the HMA result. In this study, HIV-1 was successfully genotyped by HMA and PEIA. However, a comparison of the subtyping results between HMA and PEIA revealed that HMA was slightly more accurate than PEIA.

The efficacy and effectiveness of influenza vaccination among Thai elderly persons living in the community.

OBJECTIVE: To determine the efficacy and cost-effectiveness of influenza vaccination in the Thai elderly living in an urban community. MATERIAL AND METHOD: The study design was a stratified, randomized, double blind, placebo-controlled trial. A total of 635 participants aged 60 years and older living in an urban community was randomized to receive an influenza vaccine or tetanus toxoid as a placebo injection. All participants were followed up 4-6 weeks in the community for influenza-like illness and treatment received, hospitalization and death for one year. A hemagglutination inhibition (HI) test for influenza virus antibody of all participants was done on the day of vaccination as well as 1 month, 5 months, and 12 months after the vaccination. Main outcome measures were immune response rate and protective titer, influenza-like illness, serological influenza, treatment received for influenza-like illness and their expenses, hospitalization and death during the study period. RESULTS: The immune response rate of vaccinations was 97.1% and protective titer for A (H1N1) and A (H3N2) strains were 96.4 and 98.6%, respectively. The incidence of influenza-like illness was 4.83% in the vaccine group compared with 10.88% in the placebo group. The relative risk reduction was 56% (95% CI = 14 to 77%). The survival analysis also showed that vaccinations significantly reduced the incidence of influenza (p = 0. 009). The number needed to prevent one episode was 17 persons (95% CI = 9 to 71 persons). The adverse reactions of vaccinations were mild and tolerable. However, the number of treatments received for influenza-like illness and their cost were not significantly different between the two groups. None of the subjects had pneumonia nor needed hospitalization during the study period. Seven participants died during the year of follow up, but not from influenza. CONCLUSION: In Thai elderly living in the community, influenza vaccination reduced the incidence of influenza-like illness by half, but not the number of treatments received for influenza-like illness, their cost, and its serious complications. In the year of the study, considering the cost of vaccines and the numbers needed to prevent one episode of infection from the provider's viewpoint, it may not be cost-effective to recommend that all Thai older persons living in the community should receive influenza vaccination annually. Vaccination recommendation for the elderly should be promptly implemented in expectation of a severe epidemic in Thailand.

Binding antibody to neutralizing epitope gp41 in HIV-1 subtype CRF 01_AE infection related to stage of disease.

The responsiveness of gp41 antibody against epitope ELDKWA in HIV-1 infected subjects is of importance in neutralizing viral infectivity and for being related to disease progression. In this study, antibody titers to this neutralizing epitope from HIV-1 infected subjects at asymptomatic and AIDS stages in Thailand were investigated by peptide ELISA. The results showed that the frequency of antibody production against this neutralizing epitope was low (15-35%). Moreover, antibody titers to this epitope in sera from AIDS patients were significantly lower than those in sera from asymptomatic subjects which were collected in the same year (p=0.001). Comparison between the past (1992-1994) and present (2002) sera from asymptomatic infected individuals revealed that the earlier panel contained lower antibody titers than the later panel did (p = 0.05). In addition, random sera for HIV-1 infected subjects who were infected by diverse genetic subtypes, (A through G) including CRF 01_AE, had low titers of antibody to this region as well. It is assumed that antibody production to this epitope is low and related to the stage of HIV-1 infection.

Occurrence and protective level of influenza infections using serology in patients with COPD in vaccination study.

OBJECTIVE: To investigate the prevalence, occurrence and protective level of influenza infections using serology in patients with chronic obstructive pulmonary disease (COPD) during a one-year influenza vaccination study. MATERIAL AND METHOD: A total of 123 patients with COPD were enrolled during the period of 1997 to 1998. There were 61 patients in the vaccine group and 62 patients in the placebo group with a mean age +/- SD of 67.6 +/- 8.0 and 69.1 +/- 7.5, respectively. The vaccine was composed of influenza A/Texas/36/91 (H1N1), A/Nanchang/933/95 (H3N2) and B/Harbin/07/94 strains. Antibodies to influenza viruses were detected by hemagglutination inhibition (HI) test using antigens of vaccine strains. RESULTS: The incidence of influenza proven by serological examination was 22/123 (17.9%) cases. Among 17/62 (27.4%) influenza cases in the placebo group representing natural infections, 3 (17.6%) were diagnosed as A (H1N1), 8 (47.1%) as A (H3N2), 3 (17.6%) as type A, 1 (5.9%) as type B and 2 (11.8%) as untypeable viruses. The 8.2% of influenza cases found in the vaccine group was significantly lower than 27.4% of that in the placebo group (Chi-square test, p = 0.01). The protection rate of influenza vaccination was 71%. Among 23 acute blood samples from 22 influenza cases, the titers ranged from < 10 to 20 corresponding to its type/subtype. In the vaccine group, 5 influenza cases occurred at 7, 7, 10, 11 and 11 months after vaccination. The HI antibodies to influenza A (H1N1), A (H3N2) and B viruses at titers of > or = 10 vs > or = 40 were 50.4% vs 21.9%, 54.5% vs 28.5% and 17.9% vs 4.1%, respectively. CONCLUSION: The findings indicated that from 1997 to 1998, the occurrence of influenza as natural infection was 27.4%. Influenza A (H3N2) was more frequently prevalent than A (H1N1) and B viruses. The influenza vaccination in COPD patients was effective. The protective HI antibody titers were > or = 40. The patients without protective HI antibody to A (H1N1), A (H3N2) and B viruses were 78.1%, 71.5% and 95.9%, respectively. Such patients were considered to be at high-risk for influenza and recommended to have vaccination.

Mutation of the "a" determinant of HBsAg with discordant HBsAg diagnostic kits.

Sera from 1003 in- and out-patients were investigated for hepatitis B surface antigen (HBsAg) mutation at Siriraj Hospital, Bangkok, Thailand. Individual samples were screened using two commercial HBsAg kits on automatic machine-based assays set up in parallel. The first kit was a sandwich ELISA kit that used monoclonal capture/monoclonal conjugate and color detection whereas the second was a sandwich MEIA, using monoclonal capture/polyclonal indicator and fluorochrome determination. Six specimens were found discordant by negative EIA and positive MEIA; two specimens of which were detectable of HBV DNA. Three out of four discordant results were confirmed by an anti-HBs neutralization assay. Based on direct sequencing, one HBsAg/anti-HBs sample with multiple mutations in the S gene was found. The mutation included the common glycine to arginine escape mutation at amino acid position 145 of the "a" determinant. The observation should alert the blood bank to the necessity of using screening kits capable of detecting HBV mutant carriers as well as providing verification for the phenomenon of vaccine-escape mutation in Thailand.

Acute respiratory illness in patients with COPD and the effectiveness of influenza vaccination: a randomized controlled study.

STUDY OBJECTIVES: To determine the effectiveness of influenza vaccination on influenza-related acute respiratory illness (ARI) and overall ARI in patients with COPD, and its relationship to the degree of airflow obstruction. DESIGN: Stratified, randomized, double-blind, placebo-controlled trial. SETTING: From June 1997 to November 1998 at a single university hospital. PATIENTS AND INTERVENTIONS: One hundred twenty-five patients with COPD were stratified based on their FEV(1) as having mild, moderate, and severe COPD. Within each group, they were randomized to the vaccine group (62 patients who received purified, trivalent, split-virus vaccine) or the placebo group (63 patients). MEASUREMENTS: The number of episodes and severity of total ARI, classified as outpatient treatment, hospitalization, and requirement of mechanical ventilation; and the number of episodes and severity of influenza-related ARI. RESULTS: The incidence of influenza-related ARI was 28.1 per 100 person-years and 6.8 per 100 person-years in the placebo group and vaccine group, respectively (relative risk [RR], 0.24 [p = 0.005]; vaccine effectiveness, 76%). The incidences were 28.2, 23.8, and 31.2 per 100 person-years in the patients with mild, moderate, and severe COPD, respectively, in the placebo group, and 4.5, 13.2, and 4.6 per 100 person-years in the patients with mild, moderate, and severe COPD, respectively, in the vaccine group (RR, 0.16 [p = 0.06]; vaccine effectiveness, 84%; RR, 0.55 [p = 0.5]; vaccine effectiveness, 45%; and RR, 0.15 [p = 0.04]; vaccine effectiveness, 85%, in the patients with mild, moderate, and severe COPD, respectively). Bivariate analysis revealed that the effectiveness of influenza vaccination was not modified by the severity of COPD, comorbid diseases, age, gender, or current smoking status. There was no difference in the incidence or severity of total ARI between the placebo group and the vaccine group. CONCLUSIONS: Influenza vaccination is highly effective in the prevention of influenza-related ARI regardless of the severity of COPD. Influenza vaccination does not prevent other ARIs unrelated to influenza. The effectiveness of influenza vaccination in the prevention of overall ARI in patients with COPD will depend on how much the proportion of influenza-related ARI contributes to the incidence of total ARI. Influenza vaccination should be recommended to all patients with COPD.

Longitudinal study of humoral immune responses in HIV type 1 subtype CRF01_AE (E)-infected Thai patients with different rates of disease progression.

Identification of immune correlates associated with disease progression will provide information for HIV-1 vaccine design in countries such as Thailand, where the prevalent subtypes (B and CRF01_AE [E]) are characterized. In this study, plasma viral load and humoral immune responses were measured in 20 HIV-1 subtype E-infected Thai patients with different rates of disease progression, based on CD4(+) T cell decline and clinical symptoms. Nine progressors (PRs) and 11 slower progressors (SPs) were evaluated. CD4(+) T cell counts were inversely correlated with viral load (p = 0.004) and positively correlated with p24 Ab (p = 0.022). In progressors, p24 Ab showed a significant decrease (p < 0.001) over time. V3 and gp41 Ab did not change significantly in either group. Both CD4-binding site (CD4/gp120BS) and gp120 titers correlated positively with neutralizing antibody (NAb) against both a subtype E cell line-adapted virus (NP03) and a primary isolate (TH023). However, V3 Ab correlated only with NAb against NP03 (p < 0.001). Increased NAb over time was observed more frequently in SPs as compared with PRs, against both the TH023 (p = 0.004) and NPO3 (p = 0.004) viruses. Cross-clade antibody-dependent cellular cytotoxicity was demonstrated in both groups. These data suggest that in HIV-1 subtype E infection, declining p24 Ab titer is a predictive marker of disease progression, as described for subtype B. Furthermore, in subtype E-infected patients, slower progressors retain the immune competence to develop new antibody responses to Env over time; these evolving responses may contribute to prolonged survival during HIV-1 disease progression.

Patterns of anti-HIV IgG3, IgA and p24Ag in perinatally HIV-1 infected infants.

The antibody patterns of HIV-1 IgG3, IgG and IgA and of HIV-1 p24 antigen were investigated in Thai infants born to mothers infected with HIV-1. In the 17 HIV-1 infected infants, anti-HIV antibodies were detected continuously over a period of 15-18 months and a high level of specific IgG3 subclass was observed. Anti-HIV IgA could be detected at 6 months of age whereas p24Ag was detected at 2 months. In 79 uninfected infants, maternal anti-HIV IgG gradually decreased over 9 months whilst specific IgG3 decayed rapidly during the first 6 months. Both p24Ag and anti-HIV IgA were not found in these uninfected infants. Thus, the disappearance of anti-IgG3 subclass antibodies within 6 months can predict whether infants are uninfected whereas the persistence of anti-HIV IgG and IgG3 subclass antibodies, the production of anti-HIV IgA antibody and the presence of p24Ag appear as an adjunct to the diagnosis of HIV vertical transmission. The necessary assays are relatively simple and could be performed individually.

Rapid human immunodeficiency virus diagnostic test during the intrapartum period in pregnant women who did not receive antenatal care.

The main barrier to implementation of antiretroviral drugs in HIV-infected pregnant women is the lack of antenatal care (ANC). From April 1999 to December 2001, the prevalence of pregnant women not receiving ANC and coming for delivery in Siriraj Hospital was 7.3 per cent (2,152/29,484) and the prevalence of HIV infection among this group was 5.7 per cent, substantially higher than that of 27,332 pregnant women receiving ANC in Siriraj Hospital (2.2%). Besides developing interventions to increase use of ANC, the test for diagnosis of HIV infection during the intrapartum period should be rapid, inexpensive, highly sensitive and specific, easy to perform and results should be easy to interpret. The Determine Rapid Test for detection of HIV fulfills these criteria with 100 per cent sensitivity, 99.85 per cent specificity, 97.54 per cent positive predictive value, 100 per cent negative predictive value and 0.14 per cent false positive. To improve prevention of mother-to-child HIV transmission (PMTCT), the authors believe that this uncomplicated rapid HIV testing should be used during the intrapartum period to Thai-pregnant women who did not receive antenatal care and antiretroviral drugs might be offered as soon as possible for those testing HIV-positive and for their baby as chemoprophylaxis.