Visceral fat is associated with lower executive functioning in adolescents.

BACKGROUND: Obesity, a major risk factor for cardiometabolic disease, is associated with lower cognitive performance from childhood to senescence, especially on tasks of executive function. In the cardiovascular domain, fat stored viscerally rather than elsewhere in the body carries particularly high risk. It is unknown whether this is also true in case of obesity-cognition relationships. The aim of this study was to assess the cross-sectional relationship between visceral fat (VF) and cognitive performance in a community sample of healthy adolescents. METHODS: In a community-based sample of 983 adolescents (12-18 years old, 480 males), VF was quantified using magnetic resonance imaging, total body fat was measured using a multifrequency bioimpedance, and cognitive performance was assessed using a battery of cognitive tests measuring executive function and memory. RESULTS: We found that larger volumes of VF were associated with lower performance on six measures of executive function (P=0.0001-0.02). We also found that the association of VF with executive function was moderated by sex for a subset of measures, such that relationship was present mainly in female subjects and not in male subjects (sex-by-VF interaction: P=0.001-0.04). These relationships were independent of the quantity of total body fat and a number of potential confounders, including age, puberty stage and household income. CONCLUSIONS: Our results suggest that the adverse association between obesity and executive function may be attributed to fat stored viscerally and not to fat stored elsewhere in the body. They also suggest that female subjects compared with male subjects may be more sensitive to the potentially detrimental effects of VF on cognition.

A peptide enzyme linked immunosorbent assay (ELISA) for the detection of human immunodeficiency virus type-2 (HIV-2) antibodies: an evaluation on polymerase chain reaction (PCR) confirmed samples.

BACKGROUND: HIV-1 and HIV-2 infections differ in prognosis, and may also require different prevention and/or treatment approaches. Thus, estimating the true prevalence of HIV-1 and HIV-2 infections, as well as co-infections, is a critical step in controlling the disease. There are a few commercial ELISA and immunoblot kits, which can differentiate between HIV-1 and HIV-2 infections. However, some of these assays overestimate the prevalence of dual infection. Hence, it is necessary to develop assays capable of discriminating between the two infections. OBJECTIVES: To develop a synthetic HIV-2 env based peptide ELISA for the detection of HIV-2 specific antibodies and evaluate its performance on samples from HIV positive individuals previously tested by HIV-1 and HIV-2 PCR and HIV seronegative individuals. STUDY DESIGN: We studied 45 HIV seronegative and 63 HIV infected individuals, including 30 HIV-1 PCR and immunoblot positives, 19 HIV-2 PCR and immunoblot positives, five HIV-1 and two PCR and dual immunoblot positives, two PCR negative but positive for HIV-2 by immunoblot and seven dual immunoblot positives who were only positive for HIV-1 by PCR. RESULTS: All 24 HIV-2 PCR positive samples tested were positive by the peptide assay. Among 30 HIV-1 PCR and immunoblot positive samples, only one (3.3%) showed an absorbance value above the cut off level. The seven dual positive samples by immunoblot (only positive for HIV-1 by PCR) were negative by the HIV-2 peptide ELISA. There was a 100% concordance between HIV-2 PCR and peptide ELISA. The sensitivity, specificity, and the likelihood ratio for the peptide ELISA were 100,94.9, and 19.5, respectively when compared against the PCR findings. CONCLUSIONS: This ELISA, using a specific immunodominant epitope (11 amino acids) from the transmembrane (gp36) portion of the HIV-2 envelope glycoprotein showed a high concordance with PCR findings. This can be considered as a highly sensitive, specific and economically feasible assay for the discrimination of HIV-1 and HIV-2, and may serve as an alternative to HIV-2 PCR in epidemiological studies.

Molecular confirmation of human immunodeficiency virus (HIV) type 2 in HIV-seropositive subjects in south India.

Nested PCRs for human immunodeficiency virus type 1 (HIV-1) and HIV-2 were compared with immunoblot test results. Twelve of 13 immunoblot-positive HIV-2 samples were positive by PCR. There were five INNO-LIA (Innogenetics, Zwijnaarde, Belgium) and/or HIVBLOT 2.2 (Genelabs, Singapore) samples that tested positive for dual infection. HIV-1 PCR was positive in all samples, while HIV-2 PCR was positive in two and RIBA (Chiron Corporation, San Diego, Calif.) was positive for HIV-2 in three samples. Thus the prevalence of HIV-2 is accurately estimated by the use of immunoblotting, but that of HIV-1 and -2 dual infection may be overestimated.

Rapid communication: development of in vitro resistance to macrophage-tropic- and T-cell-line-adapted HIV-1 strains among HIV-positive volunteers treated with highly active antiretroviral therapy.

We have described a peripheral blood mononuclear cell (PBMC) culture system in which control of endogenous virus and resistance to exogenous HIV-1 correlates with low viremia among HIV-1-positive people. Nineteen patients remained consistently resistant or susceptible for more than 5 years of follow-up. On the fifth year, 5 consistently susceptible volunteers with high viral loads began receiving highly active anti-retroviral therapy (HAART). After >6 months on HAART, 5 of 5 became completely or predominantly resistant on four visits over the next 6 months. Among HIV-1-positive donors, we had never observed reversal of PBMC phenotype from consistently susceptible to consistently resistant. Resistance correlated with suppression of plasma viremia and rebound in CD4+ T-cell counts and percentages. When resistant PBMCs were challenged after CD8+ T-cell depletion, 38 of 41 and 40 of 59 cultures became susceptible to HIV-1MN and HIV-1BaL, respectively. After combined CD8+ T-cell depletion and antibody neutralization of beta-chemokines, 16 of 18 cultures became susceptible to HIV-1BaL. Overall, the finding that >90% of these cultures depleted of relevant antiviral effector arms could become infected indicates resistance was not due to residual antiretroviral drug metabolites in vitro. For 2 volunteers who discontinued therapy because of side effects, pretreatment viral load correlated with loss of in vitro resistance and viral rebound. In addition to resistance to laboratory strains of HIV-1, all patients developed resistance to at least one of two CCR5-tropic, clade B primary isolates: HIV-1P15 and HIV-1P27.

CD4-independent, CCR5-dependent simian immunodeficiency virus infection and chemotaxis of human cells.

Most simian immunodeficiency virus (SIV), human immunodeficiency virus type 2 (HIV-2), and HIV-1 infection of host peripheral blood mononuclear cells (PBMCs) is CD4 dependent. In some cases, X4 HIV-1 chemotaxis is CD4 independent, and cross-species transmission might be facilitated by CD4-independent entry, which has been demonstrated for some SIV strains in CD4(-) non-T cells. As expected for CCR5-dependent virus, SIV required CD4 on rhesus and pigtail macaque PBMCs for infection and chemotaxis. However, SIV induced the chemotaxis of human PBMCs in a CD4-independent manner. Furthermore, in contrast to the results of studies using transfected human cell lines, SIV did not require CD4 binding to productively infect primary human PBMCs. CD4-independent lymphocyte and macrophage infection may facilitate cross-species transmission, while reacquisition of CD4 dependence may confer a selective advantage for the virus within new host species.

Resistance to human immunodeficiency virus type 1 in vitro as a surrogate of vaccine-induced protective immunity.

An in vitro assay developed as a correlate of vaccine-induced protection from human immunodeficiency virus (HIV) was validated in populations with relative resistance to HIV-1 as well as in HIV vaccine recipients. Cultures of peripheral blood mononuclear cells (PBMC) were challenged with 10 TCID50 of HIV-1MN or HIV-1BaL, titered in PBMC from normal controls (n=57). PBMC from HIV-1-infected persons with low viremia (n=17), exposed uninfected persons (n=23), and HIV-2-infected Senegalese prostitutes (n=9) were significantly resistant to HIV-1BaL and/or HIV-1MN (P<.001). Among 34 HIV vaccine recipients of live canarypox vector expressing multiple HIV-1 gene products with or without rgp120 booster, PBMC from postvaccination samples were significantly resistant to both strains (P<.001), and cytotoxic T lymphocyte precursor-positive samples were significantly more resistant than were precursor-negative samples (P<.03). This is the first evidence of the induction by vaccination of a validated correlate of protection. This assay should serve as a useful criterion for assessing experimental HIV vaccines before phase III efficacy trials.

Increase in plasma IL-10 levels and rapid loss of CD4+ T cells among HIV-infected individuals in south India.

Increased levels of immune activation among HIV patients from developing countries are believed to accelerate and/or enhance the shift to a Th2 cytokine environment, which in turn may result in a more rapid progression to AIDS. In support of this hypothesis, we present data from a cohort of 35 HIV+ individuals in southern India. Among asymptomatic individuals in this cohort, a dramatic increase in plasma interleukin (IL)-10 coincided with rapid decrease in CD4 counts and progression to AIDS. Serum IL-10 levels were significantly higher after 6 months of follow up (P=0.01), while CD4 counts declined at a rate of 280 cells/ul per year, roughly 3 times the rate of decline reported for HIV+ asymptomatic subjects in developed countries. Changes in serum IL-10 levels and CD4 counts fell short of statistically significant correlation (P=0.1). Among AIDS patients in this cohort, the mean period from diagnosis of AIDS to death was <5 months and is in agreement with an earlier report of rapid progression in India.

PIP: This paper presents data on the increase of plasma interleukin-10 (IL-10) levels and rapid loss of CD4+ T cells among HIV-infected individuals in southern India. A cohort of 35 HIV-positive individuals were evaluated and classified into 3 categories based on the US Centers for Disease Control (CDC) clinical classification: 9 asymptomatic, 11 symptomatic with a non-AIDS defining illness, and 15 AIDS cases. Results revealed that asymptomatic individuals experienced rapid declines in CD4 counts (280 cells/mcl/year), which is 3 times lower than the rate of HIV-positive asymptomatic subjects in developed countries. It has been estimated that progression to AIDS would occur within 2 years for the average Indian patient. On the other hand, symptomatic patients were observed to have a stable CD4 count during the 6 months of study, which could be attributable to anti-tuberculosis treatment and trimethoprim-sulfamethoxazole. The shifts in serum IL-10 levels and CD4 counts were lower for a statistically significant correlation (p = 0.1). Several factors were identified that may have caused the differing rates of disease progression, which include infectious agents and malnutrition. Among the patients, the mean period from AIDS diagnosis to death was 5 months, which is similar to reports of rapid progression in India.

Immunization with recombinant canarypox vectors expressing membrane-anchored glycoprotein 120 followed by glycoprotein 160 boosting fails to generate antibodies that neutralize R5 primary isolates of human immunodeficiency virus type 1.

Antibodies generated by candidate HIV-1 vaccines in a phase I clinical trial were assessed for neutralizing activity with a panel of eight well-characterized, genetically diverse clade B primary isolates having an R5 phenotype. The vaccines consisted of one of three different recombinant canarypox vectors expressing membrane-anchored HIV-1(MN)gp120 (ALVAC vCP205, vCP1433, and vCP1452) followed by boosting with a soluble gp160 hybrid consisting of MNgp120 and the majority of gp41 from strain IIIB. Serum samples from a subset of volunteers in each arm of the trial, containing moderate to high titers of neutralizing antibodies to HIV-1 MN, were analyzed. Competition assays with peptides revealed that the majority of neutralizing activity was specific for the MN-V3 loop. Despite MN-specific neutralization titers that sometimes exceeded 1:500, no neutralization of primary isolates was detected and, in some cases, mild infection enhancement was observed. In addition, little or no neutralization of the HIV-1 IIIB heterologous T cell line-adapted strain of virus was detected. These results reinforce the notion that monovalent HIV-1 ENV is a poor immunogen for generating cross-reactive neutralizing antibodies.

T cell-tropic HIV gp120 mediates CD4 and CD8 cell chemotaxis through CXCR4 independent of CD4: implications for HIV pathogenesis.

HIV entry is determined by one or more chemokine receptors. T cell-tropic viruses bind CXCR4, whereas macrophage-tropic viruses use CCR5 and other CCRs. Infection with CXCR4 and CCR5-tropic HIV requires initial binding to CD4, and chemotaxis induced by the CCR5-tropic envelope has been reported to be strictly dependent on CD4 binding. We demonstrate that, in contrast to CD4-dependent gp120 signaling via CCR5, envelope signaling through CXCR4 is CD4 independent, inducing chemotaxis of both CD4 and CD8 T cells. Signaling by virus or soluble envelope through CXCR4 may affect pathogenesis by attracting and activating target and effector cells.

A novel factor produced by placental cells with activity against HIV-1.

The factors controlling the dynamics of HIV-1 transmission from mother to infant are not clearly known. Previous studies have suggested the existence of maternal and placental protective mechanisms that inhibit viral replication in utero. Preliminary studies from our laboratory revealed that supernatant from placental stromal cells protected HIV-1-infected PBMC from virus-induced apoptosis and suppressed virus production. We have attempted to characterize the antiviral activity of this placental factor (PF) and delineate the stages of HIV-1 replication affected. This activity was not due to the presence of any known cytokine reported to have anti-HIV effect. Direct exposure to PF had no suppressive effect on the infectivity of cell-free HIV-1, and envelope-mediated membrane fusion appeared to be unaffected. Western blot analysis of HIV-1 from infected PBMC treated with PF revealed that expression of all viral proteins was reduced proportionately, both intracellularly and in released virions. However, exposure of HIV-1-infected cells to PF resulted in production of virions with 10-100-fold-reduced infectivity. PF-treated virions contained two- to threefold reduced ratios of cyclophilin A:Gag protein as compared with untreated virus. Reduced cyclophilin A content resulting in decreased binding of cyclophilin A to Gag could account, in part, for the observed reduction in infectivity. Our results suggest that placental cells produce an antiviral factor that protects the fetus during gestation and may have therapeutic potential.

Advancing AIDSVAX to phase 3. Safety, immunogenicity, and plans for phase 3.

AIDSVAX (VaxGen, Inc., South San Francisco, CA), a possible vaccine to protect against human immunodeficiency virus type 1 (HIV-1) infection, is being tested for efficacy in phase 3 studies. It has been tested for potential efficacy in chimpanzees, and tested for safety and immunogenicity in human clinical studies. Four candidate vaccines, each with a different envelope protein antigen or combination of antigens, have been produced in alum formulations. In both design and clinical testing, AIDSVAX has an excellent safety profile. Because these highly purified proteins were prepared using recombinant DNA technology, there is no possibility of these vaccines causing HIV infection. Having been administered to over 1200 people, the only side effects attributable to AIDSVAX have been local pain and inflammation at the injection site. After immunization, essentially all recipients developed a robust antibody response, including binding and neutralizing antibodies. The neutralizing antibodies peaked after a 12-month boost. Excellent memory is induced. Two phase 3 trials of two bivalent formulations will evaluate their efficacy. One trial will use a bivalent subtype B formulation. This trial in North America will involve 5000 men who have sex with men and heterosexual women at high risk. The other study will use a bivalent subtype B/subtype E formulation. This trial in Thailand and will involve 2500 intravenous drug users. Both studies will be randomized, double-blinded and placebo controlled. The volunteers will be followed for 3 years. The end points of the studies are infection, as defined by seroconversion to standard diagnostic tests, and viral load, as defined by commercial polymerase chain reaction (PCR) tests.

Targeted transduction of CD34+ cells by transdominant negative Rev-expressing retrovirus yields partial anti-HIV protection of progeny macrophages.

Congenitally acquired HIV infection may be uniquely suited to treatment via genetic engineering of CD34+ hematopoietic stem/progenitor cells. However, current technologies yield only a small percentage of mature cells that carry the inserted genes, and expression is frequently suppressed. Since clinical trials employing these methodologies have been proposed for anti-HIV gene therapy of HIV-infected children, we wished to assess, by in vitro modeling, the expected limits of transduction efficiency, expression, and antiviral activity using currently available methods. We measured retrovirus-mediated transduction in cord blood progenitors and their in vitro-derived progeny macrophages by Mo-MuLV vectors expressing a transdominant negative Rev (RevTD). CFU-GM transduction efficiency ranged from 7 to 85%, with an average of 28%. Semiquantitative DNA PCR demonstrated < or =100 vector sequence copies per 1000 cells in monocyte/macrophage cultures, which were grown without selection to better model in vivo conditions. When challenged with the macrophagetropic HIV-1BaL isolate, cultured macrophages from mock-transduced CFU-GM colonies supported infection in eight of eight experimental cultures, control LXSN-transduced progenitors supported infection in six of eight cultures, while macrophages derived from RevTD-transduced CFU-GM colonies supported infection in four of eight cultures. Although these results support the ability of neo(r) retroviral vectors containing RevTD to inhibit HIV replication, they indicate that further optimization of transduction efficiency and sustained expression will be required for effective anti-HIV protection in vivo.

Actin-dependent receptor colocalization required for human immunodeficiency virus entry into host cells.

Human immunodeficiency virus (HIV) envelope binds CD4 and a chemokine receptor in sequence, releasing hydrophobic viral gp41 residues into the target membrane. HIV entry required actin-dependent concentration of coreceptors, which could be disrupted by cytochalasin D (CytoD) without an effect on cell viability or mitosis. Pretreatment of peripheral blood mononuclear cells, but not virus, inhibited entry and infection. Immunofluorescent confocal microscopy of activated cells revealed CD4 and CXCR4 in nonoverlapping patterns. Addition of gp120 caused polarized cocapping of both molecules with subsequent pseudopod formation, while CytoD pretreatment blocked these membrane changes completely.

Evolutionary pattern of human immunodeficiency virus (HIV) replication and distribution in lymph nodes following primary infection: implications for antiviral therapy.

Evolutionary patterns of virus replication and distribution in lymphoid tissue during the early phases of HIV infection have not been delineated. Lymph node (LN) biopsies were excised from patients at different times after the estimated time of primary infection. Within 3 months of the acute viral syndrome, HIV was mostly present in individual virus-expressing cells in LNs; trapping of virions in the follicular dendritic cell (FDC) network was minimal or absent, but was the predominant form of HIV detected in LNs of subjects with chronic infection, either recent (4-20 months after primary infection) or long-term (>2-3 years after primary infection). Plasma viremia was significantly higher in patients during the first 3 months than in those recently infected; however, there were no significant differences in the number of virus-expressing cells per square millimeter of LN tissue in these two groups. Numbers of virus-expressing cells in lymphoid tissue were significantly lower in the subjects with long-term infection than in the other two groups. Therefore, during the transition from primary to chronic HIV infection, the level of HIV replication in lymphoid tissue remains elevated despite the fact that viremia is significantly downregulated. These findings have implications for therapeutic strategies in primary HIV infection and in recent seroconvertors.

Analysis of intercurrent human immunodeficiency virus type 1 infections in phase I and II trials of candidate AIDS vaccines. AIDS Vaccine Evaluation Group, and the Correlates of HIV Immune Protection Group.

Among 2099 uninfected subjects in phase I and II trials of candidate AIDS vaccines, 23 were diagnosed with intercurrent human immunodeficiency virus type 1 (HIV-1) infection. High-risk sexual exposures accounted for 17 infections, and intravenous drug use accounted for 6. Four subjects received placebo, 13 received a complete immunization schedule (> or = 3 injections), and 6 were partially immunized (< or = 2 injections). There was no significant difference between vaccine recipients and control groups in incidence of HIV-1 infection, virus load, CD4 lymphocyte count, or V3 loop amino acid sequence. In summary, 19 vaccinated subjects acquired HIV-1 infection during phase I and II trials, indicating that immunization with the products described is < 100% effective in preventing or rapidly clearing infection. Laboratory analysis suggested that vaccine-induced immune responses did not significantly affect the genotypic or phenotypic characteristics of transmitted virus or the early clinical course of HIV-1 infection.

Chemokine-independent in vitro resistance to human immunodeficiency virus (HIV-1) correlating with low viremia in long-term and recently infected HIV-1-positive persons.

Chemokines have been implicated as protective factors against human immunodeficiency virus (HIV) infection, competing for binding to receptors that also function as coreceptors for HIV. In this study of HIV-positive donors, peripheral blood mononuclear cell (PBMC) culture resistance to endogenous and exogenous HIV correlated with low plasma viremia and high in vitro RANTES production. However, resistant cells were not rendered susceptible by neutralization of C-C chemokines, and addition of C-C chemokines did not consistently suppress endogenous virus or exogenous HIV-1MN. In contrast, CD8 T cell depletion markedly decreased the frequency of resistant cultures without reducing C-C chemokine production. Among newly infected persons, half exhibited phenotype switching from preinfection susceptibility to postinfection resistance, suggesting that genetically predetermined constitutive cytokine production or allelic receptor expression are not generally responsible for in vitro resistance and nonprogression.

Safety profile of phase I and II preventive HIV type 1 envelope vaccination: experience of the NIAID AIDS Vaccine Evaluation Group.

The NIAID-sponsored AIDS Vaccine Evaluation Group was established in 1988 to perform phase I/II clinical trials with candidate preventive HIV-1 vaccines. This report includes safety data from 1398 HIV-negative, healthy volunteers who were enrolled into 25 phase I and 1 phase H multicentered, randomized, double-blind studies evaluating seven recombinant HIV-1 envelope vaccines, two V3 loop synthetic peptide vaccines, and two live poxvirus-vectored recombinant envelope vaccines. All studies but three were placebo controlled; the placebo was either the adjuvant alone or, in studies of recombinant poxvirus vaccines, it was the vector with no gene insert or a non-HIV gene insert. All candidate vaccines were generally well tolerated. The only adverse effects that were clearly related to vaccination were occasional acute local and systemic reactions that were associated with the adjuvants. Three adjuvants in particular were associated with moderate to severe local reactions: alum plus deoxycholate (ImmunoAg), MTP-PE (Biocine Corp.), and QS21 (Genentech, Inc.). MTP-PE was also associated with self-limited severe systemic reactions. There were no serious adverse laboratory toxicities and no evidence of significant immunosuppressive events after receipt of the candidate vaccines. A few volunteers experienced symptoms that might relate to an underlying immunopathologic mechanism (rash, hemolytic anemia, arthralgia), but their presentations were mild and their incidence was low. Eleven volunteers were diagnosed with malignancies during or after their participation, which was within the 95% confidence interval of the number of cases predicted by the National Cancer Institute SEER (Program for cancer surveillance, epidemiology, and end result reporting) database. In conclusion, the envelope-based recombinant or synthetic candidate HIV-1 vaccines appear to be safe and this work has prepared the way for the testing of increasingly complex candidate HIV-1 vaccines.

Genetic and immunologic characterization of viruses infecting MN-rgp120-vaccinated volunteers.

Proviral sequences were determined and immunologic characterization was carried out for envelope glycoproteins from 7 vaccinees who became infected with human immunodeficiency virus type 1 (HIV-1), through high-risk behavior, while participating in clinical trials of MN-rgp120, a candidate HIV-1 vaccine. All 7 infections resulted from subtype B viruses; however, only 3 of the viruses possessed the MN serotype-defining V3 domain sequence, IGPGRAF, prevalent in 60%-70% of US infections. Six of the 7 viruses differed from MN-rgp120 at a neutralizing epitope in the C4 domain, and all 7 differed from MN-rgp120 at a neutralizing epitope in the V2 domain. Recombinant gp120 was prepared from each breakthrough specimen and tested for binding to a panel of neutralizing monoclonal antibodies. The results suggest that 6 of 7 breakthrough infections may be related to incomplete immunization or to infection with viruses that differed from the vaccine immunogen at important virus-neutralizing epitopes.

Extensive evaluation of a seronegative participant in an HIV-1 vaccine trial as a result of false-positive PCR.

BACKGROUND: In the USA, more than 2000 volunteers have received one or more experimental HIV-1 vaccines in phase I and II clinical trials, and there have been breakthrough HIV-1 infections among participants receiving vaccine and placebo. Serological diagnosis of new HIV-1 infections in vaccine-trial participants will become increasingly complicated as more viral components are used in vaccines. Recognition of this problem has led to a reliance on viral-genome measurement to distinguish vaccine-induced immunity from HIV-1 infection. Currently, quantitative RNA measurement is expensive, prone to contamination, and reliable only in laboratories certified by manufacturers or that have quality-control programmes. METHODS: A high-risk vaccinee presented after an acute febrile episode and was tested for HIV-1 infection by reverse transcriptase (RT) PCR of viral RNA. Further extensive tests were required to clarify the HIV-1 infection and immune status of the vaccinee, including repeat RT-PCR, nested DNA PCR, western blot, lymphoproliferation assay, cytotoxic T-cell lysis, CD8-depleted co-culture, and HIV-1 challenge culture. FINDINGS: Initial testing of plasma by RNA RT-PCR was reported as positive. This result was not confirmed by viral cultures, nested DNA PCR, western blot, or EIA. Additional RNA RT-PCR assays gave positive results from earlier occasions in the vaccine trial. Eventually, testing of all previously reactive samples by RNA RT-PCR was repeated in a quality-controlled laboratory, and confirmed the negative HIV-1 status of the individual. INTERPRETATION: This case report exemplifies the difficulties with use of viral-genome measurement as a screening test to diagnose HIV-1 infection, particularly in individuals who have ever participated in HIV-1 vaccine trials. Monitoring of large numbers of phase III vaccinees by RNA RT-PCR will not be feasible. The design of efficacy trials for new vaccines should be in parallel with development of antibody-based diagnostic tests that are capable of differentiating between immunisation and true HIV-1 infection.