Redefining the HIV-infectious window period in the chimpanzee model: evidence to suggest that viral nucleic acid testing can prevent blood-borne transmission

BACKGROUND

Although it is rare, blood-transmitted HIV infection can occur when a donor presents in the window period between HIV-1 exposure and the first appearance of detectable p24 antigen.

STUDY DESIGN AND METHODS

To study this seronegative window period, a chimpanzee (X034) was inoculated with 38 median tissue culture infective doses of HIV-1 IIIB; serum and peripheral blood mononuclear cells were obtained one to two times per week for 12 weeks and then biweekly for 12 weeks. Infectivity was monitored by the detection of serum HIV RNA, cell-associated HIV DNA, p24 antigen, and anti-HIV and by co-culture methods.

RESULTS

No HIV markers were noted until 5 weeks after inoculation, at which time virus was isolated and HIV RNA and DNA were detected in plasma and cells, respectively. Anti-HIV and HIV p24 antigen were not present until 8 weeks after inoculation. Plasma and cells obtained from Chimpanzee X034 3 or 4 weeks after exposure were then sequentially inoculated into a second chimpanzee (X176); no HIV infection was observed in this animal during serial follow-up for 24 weeks after each inoculation. In contrast, when the fifth-week HIV-1 RNA- and DNA-positive sample was inoculated, Chimpanzee X176 was unequivocally infected with HIV-1.

CONCLUSIONS

Nucleic acid testing narrowed the seronegative window by 3 weeks (37%). More important, there was no demonstrable infectivity in either plasma or peripheral blood mononuclear cells obtained before molecular markers were detectable. This suggests that the infectious window may be considerably shorter than the total window as measured from exposure and that nucleic acid testing might not only shorten the seronegative window, but totally prevent transfusion-transmitted HIV infection.

Lack of evidence of hepatitis C infection in 290 blood component recipients, demonstrated by several single-antigen research immunoassays

BACKGROUND

A group of 290 transfusion recipients enrolled in a prospective study of posttransfusion hepatitis was studied to determine the possibility of previously unrecognized hepatitis C virus (HCV) transmission.

STUDY DESIGN AND METHODS

Before and after transfusion, blood specimens that were negative in first-generation enzyme immunoassay (EIA) were tested by current commercial EIAs, several single-antigen research EIAs, and supplemental tests.

RESULTS

Current second- and third-generation EIAs identified five subjects (1.7% of total) who had chronic hepatitis C before transfusion. Twenty additional sera had some reactivity with research EIAs. However, those results were the same before and after transfusion (n = 7), had reverted to partially reactive or nonreactive (n = 8), or could not be confirmed by serologic tests or polymerase chain reaction in follow-up specimens (n = 5).

CONCLUSIONS

Transient or restricted reactivity to HCV antigens measured by more sensitive research EIAs does not seem to correspond to recent HCV transmission by transfusion. Whether such reactivity could reflect remote HCV infection, with the potential for chronic or intermittent viremia, remains to be determined.

Virologic and serologic markers of rapid progression to AIDS after HIV-1 seroconversion

The association between early virologic and immunologic events after human immunodeficiency virus type 1 (HIV-1) infection and progression of HIV-1 infection to acquired immunodeficiency syndrome (AIDS) was studied among 59 homosexual men with documented time of seroconversion. Epidemiologic factors, such as number of lifetime sexual partners, history of sexually transmitted diseases, and other factors, also were studied. All 17 seroconverters in the cohort who developed AIDS within 3 years (rapid progressors = RPs) were compared with 42 men without AIDS for at least 6 years seroconversion (nonrapid progressors = non-RPs). Plasma levels of HIV-1 RNA, p24 antigen, antibodies to HIV-1 structural genes, beta-2 microglobulin, neopterin, and interferon-alpha were measured at four time points: (a) the last seronegative visit, (b) the first seropositive visit, (c) the visit closest to AIDS (or the corresponding visit for the non-RPs) and (d) 6 years after seroconversion (for non-RPs). Up to seroconversion, the RPs had a significantly higher number of lifetime sexual partners than non-RPs (503 versus 171, respectively). At the first seropositive visit, RPs had significantly higher concentrations of plasma HIV-1 RNA (p < 0.01) and prevalence of p24 antigenemia (p < 0.001) and significantly lower levels of antibodies to the HIV-1 gag proteins p17 and p24 (p < 0.01-0.001) compared with non-RPs. These differences increased during follow-up visits. Antibodies to p66 and gp120 were significantly different only at the visit closet to AIDS (p < 0.001), as were beta-2 microglobulin and interferon alpha. These findings suggest that early virologic-immunologic events after HIV-1 infection may determine the rate of progression to AIDS. Anti-gag immune response may prevent rapid progression of HIV-1 disease and should be considered for future vaccine studies.

HIV-1 gp120-specific antibody-dependent cell-mediated cytotoxicity correlates with rate of disease progression

The Ab-dependent cell-mediated cytotoxicity (ADCC) activity of anti-gp120 Abs in serum from four groups of HIV-1-positive individuals in the Multicenter AIDS Cohort Study was evaluated at several time points over a 10-yr period. HIV-1-positive individuals who progressed to AIDS within 3 yr of seroconversion (rapid progressors) were compared with seroconverters who did not progress to AIDS within 6 yr (nonrapid progressors) and individuals who were seropositive when they entered the study and did not progress to AIDS within 9-10 yr (nonprogressors). At the visit closest to AIDS, rapid progressors had significantly lower titers of Abs that mediate ADCC against HIV-1 gp120 than those of nonrapid progressors at corresponding visits or those of nonprogressors at any visit. Nonprogressors generally had high titers of ADCC Abs at all visits. Differences between ADCC titers of rapid progressors and nonrapid progressors or nonprogressors remained when longitudinal changes within individuals were compared. Among seroconverters who were nonrapid progressors, those with low or declining ADCC titers lost significantly more CD4+ cells during the study than those whose ADCC titers were stable or increasing, even though both groups had similar serum virion RNA levels. This demonstrates that high titers of Abs that mediate ADCC correlate with a successful host defense against AIDS.

HIV-1 gp120-specific antibody-dependent cell-mediated cytotoxicity correlates with rate of disease progression

The Ab-dependent cell-mediated cytotoxicity (ADCC) activity of anti-gp120 Abs in serum from four groups of HIV-1-positive individuals in the Multicenter AIDS Cohort Study was evaluated at several time points over a 10-yr period. HIV-1-positive individuals who progressed to AIDS within 3 yr of seroconversion (rapid progressors) were compared with seroconverters who did not progress to AIDS within 6 yr (nonrapid progressors) and individuals who were seropositive when they entered the study and did not progress to AIDS within 9-10 yr (nonprogressors). At the visit closest to AIDS, rapid progressors had significantly lower titers of Abs that mediate ADCC against HIV-1 gp120 than those of nonrapid progressors at corresponding visits or those of nonprogressors at any visit. Nonprogressors generally had high titers of ADCC Abs at all visits. Differences between ADCC titers of rapid progressors and nonrapid progressors or nonprogressors remained when longitudinal changes within individuals were compared. Among seroconverters who were nonrapid progressors, those with low or declining ADCC titers lost significantly more CD4+ cells during the study than those whose ADCC titers were stable or increasing, even though both groups had similar serum virion RNA levels. This demonstrates that high titers of Abs that mediate ADCC correlate with a successful host defense against AIDS.

Accumulation of activated CD4+ lymphocytes in the lung of individuals infected with HIV accompanied by increased virus production in patients with secondary infections

The lung is continuously exposed to infectious and non-infectious agents causing cell activation. Activated cells in the lung such as antigen-presenting cells which harbour HIV may favour this organ as a site for virus production. To test this hypothesis, cells from blood and bronchoalveolar lavage (BAL) of HIV-infected patients and healthy controls were obtained and the activation of the cells were analysed by measuring the expression of IL-2 receptor, HLA-DR and VLA-1. The HIV-infected individuals were subdivided into 'lung symptomatic' or 'lung asymptomatic' patients, depending on the presence or absence of secondary lung diseases besides HIV. All HIV-infected individuals demonstrated a decreased number of CD4+ lymphocytes in blood; however, normal numbers of these cells were found in BAL. The activation state of CD4+ and CD8+ T lymphocytes in blood and BAL was higher in lymphocytes from HIV-infected patients compared with controls. The activation state was highest in the lung symptomatic group. Lung symptomatic patients and lung asymptomatic patients with extrapulmonary infections had increased levels of free virus in plasma. Four out of four individuals without or with only low amounts of cell-free HIV in plasma belonged to the symptom-free subgroup. These results suggest that microorganisms other than HIV may promote viral replication via antigen-driven accumulation and activation of CD4+ cells in the lung or other organs, and thus may be responsible for the loss of helper T cells and the progression of the disease.

Natural history of HIV-1 cell-free viremia

OBJECTIVE

To characterize the natural history of viremia with human immunodeficiency virus type 1 (HIV-1) and its association with disease progression from infection to acquired immunodeficiency syndrome (AIDS).

DESIGN

Prospective cohort study. Annual specimens were tested for quantitative virion-associated HIV-1 RNA, p24 antigen, and CD4+ lymphocyte levels.

PARTICIPANTS

A total of 42 homosexual men who seroconverted to HIV-1 between 1982 and 1985.

MAIN OUTCOME MEASURES

Trends over time in serum HIV-1 RNA level, correlations between serum HIV-1 RNA and other markers, and prediction of AIDS using these markers.

RESULTS

HIV-1 RNA levels were stable over time, increasing by 10-fold or more in only six (14%) of the 42 subjects during 3 to 11 years of follow-up. Mean HIV-1 RNA levels were 10(3.8) copies/mL if AIDS occurred in less than 4 years, 10(3.07) copies/mL if AIDS developed within 4 through 9 years, and 10(2.27) copies/mL if AIDS did not develop within 6 through 11 years. In both univariate and multivariate models, initial and subsequent HIV-1 RNA levels, p24 antigenemia, and percentage of CD4+ lymphocytes were independently predictive of AIDS.

CONCLUSIONS

The stability of virion-associated HIV-1 RNA levels suggests that an equilibrium between HIV-1 replication rate and efficacy of immunologic response is established shortly after infection and persists throughout the asymptomatic period of the disease. Thus, defective immunologic control of HIV-1 infection may be as important as the viral replication rate for determining AIDS-free survival. Because individual steady-state levels of viremia were established soon after infection, HIV-1 RNA levels may be useful markers for predicting clinical outcome.

Virologic and immunologic characterization of symptomatic and asymptomatic primary HIV-1 infection

To define virologic and immunologic differences in patients with acute symptomatic and asymptomatic primary human immunodeficiency virus type 1 (HIV-1) infection, sequential plasma specimens were obtained longitudinally for 1-2 years postseroconversion from subjects with well-documented time of seroconversion. Thirteen of them had an acute symptomatic primary infection, eight subjects had asymptomatic primary infection and long-term follow-up, and 27 had asymptomatic seroconversion and short-term follow-up. Quantitative plasma HIV-1 RNA levels, CD4+ lymphocyte counts, and levels of antibodies to gp120, p66, p41, p31, p24, and p17 were measured. At the time of seroconversion, there was no significant difference in HIV-1 RNA levels and CD4+ counts between symptomatic (n = 13) and asymptomatic (n = 27) subjects. Subsequently, however, establishment of low levels of plasma HIV-1 RNA was seen significantly more frequently in asymptomatic (n = 8) than in symptomatic (n = 13) primary infection; this correlated with higher levels of some (anti-gp120 and anti-p31) anti-HIV-1 antibodies and a slower decline in CD4+ lymphocyte counts. These results indicate that immunologic control of viremia early after infection may be a critical determinant to subsequent clinical course of HIV-1 infection. They also suggest that persons with acute symptomatic primary infection may generally progress to having acquired immune deficiency syndrome (AIDS) more rapidly than people with low-grade symptoms or asymptomatic primary infection.

Prevalence of human T-cell lymphotropic virus type 1 (HTLV-1) and HTLV-2 infection among Spanish drug users measured by HTLV-1 assay and HTLV-1 and -2 assay. HTLV-1 and HTLV-2 Spanish Study Group

The prevalence of human T-cell lymphotropic virus type 1 (HTLV-1) and HTLV-2 infection in 1992 and 1993 was determined by testing 2,152 specimens from injection drug users living in 11 geographic areas in Spain. Results obtained by an authentic HTLV-1 and -2 test were compared with those obtained by an HTLV-1 assay. HTLV infection was identified in 7 of 11 regions, with an overall prevalence of 2.5% (range, 0.4 to 11.5%). Fourty-four (81%) of 54 subjects were infected with HTLV-2; the viral strains in the remaining 10 subjects could not be serologically typed. Underestimation of HTLV infection because of the low sensitivities of HTLV-1 enzyme immunoassays for HTLV-2 antibody was relatively low (< 20%). Therefore, previous epidemiologic findings generated with HTLV-1 enzyme immunoassays appear to be reasonably accurate. Our results suggest that the rate of HTLV infection may have been increasing recently among Spanish drug users.

Time course of detection of viral and serologic markers preceding human immunodeficiency virus type 1 seroconversion: implications for screening of blood and tissue donors

BACKGROUND

Almost all human immunodeficiency virus (HIV) transmission via blood or tissues that has occurred since anti-HIV screening was implemented in 1985 is traceable to blood given after infection but before antibody seroconversion, a time that is referred to as the window period. In this study, the performance of newer assays designed to detect viral and serologic markers soon after infection is assessed, and the reduction in the window period achieved by these assays is estimated.

STUDY DESIGN AND METHODS

Three cohort studies of persons at high risk for acquiring HIV infection were identified. These studies included well-controlled HIV type 1 (HIV-1) polymerase chain reaction (PCR) analyses of serial preseroconversion specimens from HIV-1-seroconverting homosexual men or intravenous drug users. Of 81 enrollees with anti-HIV-1 seroconversion documented by a viral lysate anti-HIV-1 enzyme immunosorbent assay (EIA) available in 1989, 13 (16%) had PCR-positive preseroconversion specimens. In the present study, sera from these 13 PCR-positive samples were further tested for anti-HIV by 10 contemporary EIAs and 6 supplemental assays, as well as being tested for plasma p24 antigen and HIV-1 RNA. Preseroconversion sera from 38 HIV-1 DNA PCR-negative cohort participants were also tested by selected anti-HIV EIAs and tested for p24 antigen and HIV-1 RNA. On the basis of these laboratory data and the intervals between blood drawing in all 81 men, the reduction in the preseroconversion window period achieved by these new assays was estimated with a mathematical model developed to analyze seroconversion data.

RESULTS

Nine (69%) of the 13 preseroconversion PCR-positive samples had anti-HIV that was detectable by one or more contemporary anti-HIV-1 or anti-HIV type 2 EIA. Supplemental antibody assays were negative on all four EIA-nonreactive preseroconversion samples and negative or indeterminate on a high proportion of the nine EIA-reactive PCR-positive samples. Eight (61%) of the 13 samples were p24 antigen-positive, and 11 (85%) were HIV-1 RNA-positive. The estimated reductions in the window period (relative to the index viral lysate-based anti-HIV EIA) were as follows: contemporary anti-HIV-1/2 EIAs, 20.3 days (95% Cl, 8.0-32.5); p24 antigen and DNA PCR, 26.4 days (95% Cl, 12.6-38.7); and RNA PCR, 31.0 days (95% Cl, 16.7-45.3).

CONCLUSION

Recent improvement in the sensitivity of anti-HIV assays has resulted in significant shortening of the preseroconversion window period. Consequently, the incremental reduction in the window period that could be achieved by implementing direct virus-detection assays has diminished significantly.

Detection of p24 antigen with and without immune complex dissociation for longitudinal monitoring of human immunodeficiency virus type 1 infection

Sequential specimens obtained from 87 multicenter AIDS cohort study participants were tested by three p24 antigen tests. They included a polyclonal enzyme immunoassay (EIA), a monoclonal EIA, and a monoclonal EIA after immune complex dissociation (ICD) of specimens. Subjects were grouped into two categories defined by real-time testing with the polyclonal EIA: 39 had become positive for p24 antigen (antigen converters) during follow-up, and 48 had progressed to AIDS without detectable antigenemia. Twenty-four (61%) antigen converters were positive by ICD-monoclonal EIA about 1 year earlier than by monoclonal EIA. In contrast, only 12 (25%) patients who progressed to AIDS without detectable antigenemia became positive by ICD-p24 EIA before developing AIDS. Thus, the main benefit of ICD treatment may be to detect p24 antigenemia approximately 1 year before the regular assay rather than to identify additional antigenemic people. Quantitative plasma RNA levels were also determined in longitudinal samples from 20 antigen converters and 7 men who developed AIDS without antigenemia. Although mean human immunodeficiency virus type 1 RNA levels were higher in antigen-positive than in antigen-negative samples (P = 0.002), more than half (11 of 20) of the antigen converters had no measurable change in human immunodeficiency virus type 1 RNA associated with change to antigen positivity.

Unsuspected primary human immunodeficiency virus type 1 infection in seronegative emergency department patients

To estimate the number of recently infected patients in the window period before human immunodeficiency virus type 1 (HIV-1) seroconversion among patients seeking medical care, randomly selected adults presenting to an inner city emergency department were tested for HIV-1 antibody and p24 antigen. Of 2300 patients enrolled, 180 (7.8%; 95% confidence interval [CI]: 6.7%-8.9%) were Western blot (WB)-positive for HIV-1 antibodies. Of 2120 antibody-negative or WB-indeterminate patients, none of whom were identified on clinical grounds as having primary HIV-1 infection, 6 (0.28%; CI, 0.07%-0.51%) were p24 antigen-positive with serologies consistent with primary HIV-1 infection. Of these 6, 3 were seronegative even with third-generation antibody ELISA. HIV-1 infection in these 6 patients was further confirmed by polymerase chain reaction amplification of virion-associated RNA in serum demonstrating 10(4)-10(5) virions/mL. With 40,000 new HIV-1 infections in the United States annually, approximately 750 persons with undiagnosed primary HIV-1 infections may seek primary health care in any given week in the United States. Testing for viral antibodies alone will fail to detect a large proportion of these persons. Thus, early identification by p24 antigen testing may be important to diagnose and treat symptomatic illness, implement public health and counseling measures, and arrange appropriate medical follow-up.

Detection of human immunodeficiency virus type 1 p24 antigen and plasma RNA: relevance to indeterminate serologic tests

BACKGROUND

Most enzyme immunoassay-reactive specimens producing indeterminate Western blot results belong to individuals who are not infected with human immunodeficiency virus type 1 (HIV-1). However, a small percentage may correspond to early seroconversion or advanced disease, at which stage partial reactivity on Western blot may be observed.

STUDY DESIGN AND METHODS

To determine the utility of HIV-1 p24 antigen and cell-free RNA detection for the resolution of Western blot-indeterminate serologic results, several types of enzyme immunoassay-positive, sero-indeterminate specimens were analyzed. Samples were obtained from infected individuals at the time of seroconversion (n = 20), from patients with AIDS (n = 2), as specimens from clinical samples obtained for diagnostic testing (n = 57), from blood donors producing persistent indeterminate results (n = 47), and from random blood donors (n = 72).

RESULTS

HIV-1 p24 antigen was detected in 10 of 20 specimens collected from 9 of 12 individuals who seroconverted and in 2 of 2 AIDS patients. HIV-1 plasma RNA was positive in 22 of 22 samples from those 14 individuals. All of 57 diagnostic specimens and 47 samples obtained from persistently indeterminate donors were negative for HIV-1 p24 antigen and plasma HIV-1 RNA. One of 72 blood donor specimens was positive for HIV-1 plasma RNA and had borderline reactivity for p24 antigen.

CONCLUSION

The detection of plasma RNA appears to be sensitive and specific; negative test results may be used to identify false-positive serologic reactions. The detection of p24 antigen and plasma RNA can also be used to confirm HIV-1 infection in persons with indeterminate serologic results associated with early seroconversion or late-stage disease.

Selectivity of human T lymphotropic virus type-1 (HTLV-1) and HTLV-2 infection among different populations in Brazil

A seroprevalence study for human T lymphotropic virus type-1 (HTLV-1) and HTLV-2 was conducted in Sao Paulo, Brazil among 2,312 individuals that included following groups: 1,148 volunteer blood donors, 37 patients with tropical spastic paraparesis (TSP), 53 with lymphoproliferative disorders, 171 with a history of multiple blood transfusions, 268 human immunodeficiency virus type-1 (HIV-1) seropositive subjects, and 635 Amazonian Indians. Antibodies to HTLV-1/2 were screened by enzyme-linked immunosorbent assay (ELISA) and confirmed by Western blot and/or radioimmunoprecipitation. The differentiation of HTLV-1 and HTLV-2 was achieved using a synthetic recombinant peptide (rgp46) ELISA. We confirmed the presence of HTLV-1 infection in Brazil, both in blood donors (0.4%) and in patients exposed to blood transfusions (2.9%), as well as the occurrence of HTLV-1-associated TSP (11 patients, or 30% of all TSP cases) and adult T cell leukemia/lymphoma (two cases, or 3.5% of all hematologic malignancies). The HIV-1 infected individuals were shown to be coinfected (8.9%) with either HTLV-1 or HTLV-2. All HIV-1 and HTLV-2 coinfected individuals were intravenous drug abusers. In addition, we also demonstrated the presence of HTLV-2 (4.7%), and HTLV-1/2 (0.8%) in tribes of Amazonian Indians who lived in the eastern Amazon basin (southeastern State of Para). The selectivity of these retroviral infections in particular groups is emphasized, as well as the need for HTLV-1/2 screening of all blood donors in Brazil as a public health measure.

Combination therapy with zidovudine and didanosine compared with zidovudine alone in HIV-1 infection

OBJECTIVE

To assess safety, pharmacokinetics, and in-vivo virologic activity of five different combination regimens of zidovudine and didanosine compared with zidovudine alone in patients with human immunodeficiency virus type 1 (HIV-1) infection.

DESIGN

Open-label, partially randomized, dose-ranging study.

SETTING

University-affiliated, medical center clinics.

PATIENTS

A total of 69 patients with HIV-1 infection, CD4+ cell counts fewer than 400 cells/mm3, and fewer than 121 days of previous zidovudine treatment.

INTERVENTIONS

Fifty-five patients received combination therapy with zidovudine and didanosine, and 14 received zidovudine therapy alone (600 mg/d). Daily dosages in milligrams of zidovudine and didanosine, respectively, in the five combination groups were 150 and 90 mg, 300 and 334 mg, 600 and 334 mg, 300 and 500 mg, and 600 and 500 mg.

MEASUREMENTS

CD4+ cell counts, HIV-1 RNA titers in plasma, and toxic effects.

RESULTS

The combination regimens were associated with higher and more sustained increases in CD4+ cells than zidovudine alone, even after adjustment for initial CD4+ counts and previous zidovudine therapy (P < 0.001). The median increase in CD4+ cell counts was 166 cells/mm3 with combination therapy and 77 cells/mm3 with zidovudine alone (P = 0.001) and did not differ statistically among the five combination regimens. Human immunodeficiency virus type 1 RNA titers in plasma decreased in 15 (83%) of 18 combination-therapy recipients compared with 2 of 7 zidovudine-alone recipients (P = 0.017). No pharmacokinetic interactions were seen between zidovudine and didanosine. Toxicity rates were low among all treatment groups. A greater decrease in hemoglobin levels was seen with the regimen using zidovudine alone (-8 g/L) compared with combination regimens using the same zidovudine dose (-1.5 g/L, P = 0.03).

CONCLUSIONS

Combination therapy with zidovudine and didanosine produced larger and more sustained increases in CD4+ cell counts, more frequent decreases in plasma HIV-1 RNA titers, and more stable hematologic status than zidovudine therapy alone. The effects of this combination on the progression of HIV disease merit further study, to provide information about clinical outcome, because this was a relatively small study based on surrogate markers of HIV-1 infection.

Cell-free plasma human immunodeficiency virus type 1 titer assessed by culture and immunocapture-reverse transcription-polymerase chain reaction

The relationship between plasma human immunodeficiency virus type 1 (HIV-1) infectious titer, determined by quantitative fivefold end-point dilution culture, and the detection of genomic HIV-1 RNA by immunocapture-cDNA-polymerase chain reaction was determined. The optimal plasma specimen collection and storage conditions for the use of such virologic markers for clinical trials were also determined. The variabilities in the measurement of infectious HIVLAI titer associated with intra- and interdonor peripheral blood mononuclear cells were 1.2 and 0.86 log10 50% tissue culture infective doses (TCID50)/ml (95% confidence interval range), respectively. Plasma HIV-1 titers did not change significantly after storing whole blood for 6 h either at 4 degrees C or ambient temperature or plasma for a median of 267 days (range, 259 to 482) at -70 degrees C. The detection of genomic HIV-1 RNA encapsulated in viral particles was very consistent, reproducible, and unaffected by either heparin or acid citrate or by multiple freeze-thawing. The HIV-1 RNA titers also appeared to generally correlate with the biologic titer obtained by the microculture assay. The consistency in infectious HIV-1 titer was evaluated by using 27 unfrozen plasma specimens collected from five subjects over 1 to 9 days. The median change in HIV-1 titer relative to baseline was -0.5 log10 TCID50/ml (interquartile range, -1.03 to 0.175 log10). In contrast, no significant change in HIV-1 RNA for the same frozen plasma specimens was noted. As such, immunocapture-cDNA-polymerase chain reaction may be a useful measure of plasma viremia for studying the natural history of HIV disease and assessing response to therapy.

Lack of detection of human immunodeficiency virus type 1 DNA by polymerase chain reaction in the plasma and lymphocytes of seronegative exposed hemophiliacs

Direct detection of human immunodeficiency virus type 1 (HIV-1) DNA in serum or plasma samples has been reported in seronegative as well as seropositive individuals. An alkaline lysis procedure was adapted for polymerase chain reaction (PCR) analysis of plasma specimens. Eighty-five seronegative hemophiliacs, 52 of whom had been exposed to HIV-contaminated blood components, and 19 seronegative at-risk individuals were studied. Each sample was extracted and amplified with SK38/39 gag primers at least three times. Seventy-six samples (72%) were consistently negative for HIV-1 DNA, 24 (22%) were positive only once, and 4 (3%) were positive twice. Genomic DNA from peripheral mononuclear cells was prepared from 12 of 76 negative samples, 18 of 24 samples that were positive once, and 2 of 4 samples that were positive twice and analyzed with both gag and long terminal repeat primers. None (0/32) of these cellular DNAs were positive for HIV-1, which suggests that these seronegative exposed hemophiliacs were not latently infected with HIV-1. In contrast, all (10/10) control cells from seropositive patients were positive with both primer pairs. The detection of HIV-1 DNA in serum or plasma may be prone to a high level of false-positive PCR signals and should be interpreted with caution.

Early detection of antibody to human immunodeficiency virus type 1 by using an antigen conjugate immunoassay correlates with the presence of immunoglobulin M antibody

Sequential plasma samples obtained from 16 individuals who seroconverted were tested for the presence of antibody to human immunodeficiency virus type 1 (HIV-1) by an antigen conjugate enzyme immunoassay (EIA) and a conventional antibody conjugate assay. In 11 of these individuals, the antigen conjugate assay detected antibody to HIV-1 2 to 11 days (mean, 5.5 days) earlier than the antibody conjugate assay. In 11 individuals, HIV-1 p24 antigen was detected a median of 6.5 days (range, 3 to 14 days) prior to positivity by the antigen conjugate EIA. Using class-specific probes, we determined the profiles of immunoglobulin M (IgM), IgG, and IgA antibodies for each individual and correlated these profiles with the EIA signals from both assays. In general, the appearance of IgM exhibited a peak at about 1 week postseroconversion, which was followed by gradually declining levels. Absorbance levels for IgG antibody, however, rose steadily and reached a plateau after 3 to 5 weeks. The levels of IgA were generally low and variable. In contrast to the progressive increase in EIA absorbance observed by the antibody conjugate assay, the antigen conjugate assay displayed a rapid early rise in absorbance which generally coincided with the transient expression of IgM antibody. The subsequent gradual increase coincided with rising levels of IgG. Because the configuration of the antigen conjugate EIA allows for an increased sensitivity for IgM compared with that for other classes of immunoglobulins, these results suggest that earlier detection of antibody to HIV-1 is due to the detection of IgM antibody during the early phase of seroconversion.

A sensitive viral capture assay for detection of plasma viremia in HIV-infected individuals

Human immunodeficiency virus was detected in the serum/plasma of individuals infected with human immunodeficiency virus (HIV) after capture of virions on microparticles coated with monoclonal antibodies to external and transmembrane proteins of HIV-1. We analyzed serial samples obtained from 6 individuals who seroconverted, 18 asymptomatic, and 12 AIDS patients. HIV-1 RNA was detected in all (29/29) seropositive samples and in 6 seronegative samples immediately preceding seroconversion. In contrast, HIV antigen was detected in 13/29 (45%) of seropositive samples. HIV-1 RNA was also detected in 3 antigen-negative samples from one individual 8-5 months prior to seroconversion and in one sample from another person 2 days before antigen positivity. The intensity of the polymerase chain reaction (PCR) signal paralleled the concentration of HIV antigen. Conversely, seropositive HIV antigen-negative samples gave a weaker PCR signal. HIV-1 RNA was detected in 10/18 (60%) samples from asymptomatic, HIV antigen-negative, individuals and in 11/12 (92%) specimens obtained from AIDS patients. The viral capture method may provide a sensitive, specific, and semiquantitative means of detecting circulating HIV at all stages of infection.

Specific effects of ras oncogene expression on the growth and histogenesis of human epidermal keratinocytes

Little progress has been made in identifying specific regulatory pathways that might be affected in cells by a mutationally activated p21ras when its expression does not lead to complete transformation. We wished to determine whether a normal, diploid human epithelial cell in which activation of ras had occurred could be identified in culture and, furthermore, whether expression of a mutant p21ras in such an otherwise normal cell would result in abnormal histogenic behavior in vivo. Thus, we introduced the v-Ha-ras gene into an early passage culture of normal human epidermal keratinocytes via a defective retrovirus. We examined these genetically engineered cells for changes in growth and differentiation, both in culture and in the epithelium formed when cultures were grafted to the skin of nude mice. We have found that keratinocytes expressing p21v-ras are independent of epidermal growth factor (EGF)--a factor which is normally essential for progressive colony growth, but that they are otherwise indistinguishable in culture from normal cells. v-ras keratinocytes also secrete a factor possessing some specific biological activities of members of the fibroblast growth factor (FGF) family, but which is distinct from acidic and basic FGF. In short-term dermal grafts the v-ras cells form a non-invasive and normally differentiating epidermis. However, the cells express elevated levels of keratin 19, which is a characteristic of fetal epidermis and of premalignant lesions of some stratified squamous epithelia.