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Results for “seroconversion”

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PubMed1992

Failure of acyclovir to enhance the antiviral effect of alpha lymphoblastoid interferon on HBe-seroconversion in chronic hepatitis B. A multi-centre randomized controlled trial.

Serum HBeAg levels and HBe-seroconversion were investigated in patients with chronic HBeAg-positive hepatitis who were randomized to receive either alpha lymphoblastoid interferon (5 megaunits subcutaneously daily for 16 weeks) plus acyclovir (2 g intravenously daily during weeks 1 and 2 and weeks 9 and 10) (n = 49) or no treatment (n = 48). HBeAg levels in serial dilutions of patient serum were assessed quantitatively by radioimmunoassay and compared with the values found for negative control serum. One year after the start of therapy 44 treated patients and 43 control patients were available for follow-up. A complete response (HBe-seroconversion) occurred in 11 treated patients (25%) and six controls (14%) (difference: 11%, 95% CI-5-28%). A partial response (HBeAg less than 50% of initial level) was found significantly more often for treated patients (n = 13, 30%) than for controls (n = 2, 5%) (difference: 25%, 95% CI 10-40%). During acyclovir-interferon combination therapy the decrease in HBeAg level was similar to that achieved during therapy with interferon alone. We conclude that acyclovir does not enhance the effect of interferon on serum HBeAg levels. Since HBeAg levels continue to decline during interferon treatment and rebound thereafter to pretreatment levels, prolongation of therapy may yield a higher response rate.

Acyclovir↗

PubMed1995

Maintenance of high virus load even after seroconversion in newborn cats acutely infected with feline immunodeficiency virus.

The viral loads in adult and newborn cats have been compared following injection with feline CD4+ FeL-039 line cells acutely infected with feline immunodeficiency virus (FIV). The level of virus genome in peripheral blood mononuclear cells (PBMC) increased progressively despite seroconversion in the newborn cats, whereas the virus genome was apparently cleared after seroconversion in the adult cats. Immunohistochemical staining of thymus of the FIV-infected newborn cats showed clusters of viral antigen-positive cells. These results indicate that FIV infection of the newborn cat results in higher virus loads than infection of the adult cat. We discuss these findings in relation to FIV as a model system for studies of the infection of neonates with an immunosuppressive retrovirus.

Acute Disease↗

PubMed1994

Detection of anti-HIV in saliva and urine at the time of seroconversion.

To determine whether there is a delay between the appearance of anti-HIV in serum/plasma and its detection in saliva and urine, salivary and urine specimens were collected from nine individuals who, on the basis of increasing IgG anti-HIV reactivity, Western blot band patterns and presence of strong IgM anti-HIV reactivity in their serum specimens, were believed to have recently become anti-HIV-positive. Serum from 8 of these patients and 3 commercial panels of plasma specimens collected during seroconversion were diluted to mimic the low immunoglobulin concentrations present in saliva and urine and tested in Wellcozyme HIV 1 + 2 GACELISA and four commercial EIAs intended for testing serum specimens. The 9 pairs of saliva and urine specimens were collected between 4 and 43 days (median 24 days) after the first evidence of seroconversion. All were reactive by Wellcozyme HIV 1 + 2 GACELISA and gave optical density/cut off (OD/CO) ratios in the range 3.8 to 9.8 (median 5.2) for dribbled saliva and 2.4 to 10.1 (median 6.3) for urine. Salivary specimens taken with commercial collection devices gave OD/CO ratios in the range 1.6 to 10.6 (median 5.9). In the serum/plasma specimens Wellcozyme HIV 1 + 2 GACELISA detected anti-HIV at higher dilutions than the other assays, often with a 100-fold or more difference. Saliva and urine specimens were all strongly reactive by Wellcozyme HIV 1 + 2 GACELISA. We therefore predict that it would first detect anti-HIV in salivary and urine specimens at about the same time as it becomes detectable in serum/plasma but that other commercial EIAs would not.

Journal Article↗

PubMed2005

Seroconversion of calves following intravenous injection with embryos exposed to bovine viral diarrhea virus (BVDV) in vitro.

Two recent studies demonstrated that a high-affinity isolate of BVDV (SD-1), remained associated with a small percentage of in vivo-derived bovine embryos following artificial exposure to the virus and either washing or trypsin treatment. Further, the embryo-associated virus was infective in an in vitro environment. Therefore, the objective of this study was to determine if the quantity of a high-affinity isolate of BVDV associated with single-washed or trypsin-treated embryos could cause infection in vivo. Twenty zona-pellucida-intact morulae and blastocysts (MB) were collected on day 7 from superovulated cows. After collection, all MB were washed according to International Embryo Transfer Society (IETS) standards, and all but 4 MB (negative controls) were exposed for 2 h to 10(5)-10(6) cell culture infective doses (50% endpoint) per milliliter (CCID(50)/mL) of viral strain SD-1. Following exposure, according to IETS standards, one half of the MB were washed and one half were trypsin treated. All MB were then individually sonicated, and sonicate fluids were injected intravenously into calves on day 0. Blood was drawn to monitor for viremia and(or) seroconversion. Seroconversion of calves injected with sonicate fluids from washed and trypsin-treated embryos occurred 38% and 13% of the time, respectively. Therefore, the quantity of a high-affinity isolate of BVDV associated with single-washed or trypsin-treated embryos was infective in vivo.

Animals↗

PubMedDate not supplied

Fever, human herpesvirus-6 (HHV-6) seroconversion, and acute rejection episodes as a function of the initial seroprevalence for HHV-6 in renal transplant recipients.

Human herpesvirus-6 (HHV-6) is an opportunistic viral pathogen of emerging clinical significance in immunocompromised patients. We performed a seroepidemiological survey to test the relation between seroprevalence among donors and recipients for HHV-6 at three endpoints. Before transplantation sera obtained from cadaveric donors and from potential recipients were tested for IgG antibodies against HHV-6 using an enzyme-linked immunoassay. The group of recipient sera, including samples obtained before as well as 2, 4, 12, and 48 weeks after transplantation, were tested for anti-HHV-6 IgM antibodies using an indirect immunofluorescence assay. The statistical analysis was performed with the Cox proportional hazards models. The HHV-6 seronegative group (n = 11) compared with the HHV-6 seropositive group (n = 109) showed twice the risk of HHV-6 IgM seroconversion (RR = 2.24; P < .04), with a greater risk of fever, namely 3.8, which was on the verge of statistical significance. The opposite trend toward an association with acute rejection episodes was observed among HHV-6 seronegative patients (RR = 1.81). The presence of IgG antibody in the sera of donors to IgG seropositive recipients had no association with the occurrence of IgM seroconversion. In contrast, IgM antibodies to HHV-6 appeared in four of five seronegative patients who received allografts from IgG seropositive donors. These preliminary data suggest that the effects seem to be the consequence of HHV-6 transmission through a renal allograft.

Antibodies, Viral↗

PubMed1997

Duration of time between exposure and seroconversion in healthcare workers with occupationally acquired infection with human immunodeficiency virus.

Through December 1994, 41 healthcare workers with a documented seroconversion to human immunodeficiency virus (HIV) in temporal association to an occupational exposure were reported to the Centers for Disease Control and Prevention (CDC). Each tested positive for HIV antibodies within 12 months of the occupational exposure. Two (5%) of the 41 tested negative for HIV antibodies >6 months following the occupational exposure but were seropositive within 12 months of the injury. Both denied any subsequent exposures to HIV after the initial exposure, and in one case genetic sequencing confirmed the source of the infection. Four of the healthcare workers took postexposure zidovudine prophylaxis; each reported an acute retroviral syndrome within 6 weeks of their exposure, and each of the four seroconverted to HIV within 6 months of the exposure. Our data suggest that zidovudine prophylaxis does not delay the development of HIV antibodies beyond 6 months. Because many of the healthcare workers had follow-up testing at irregular intervals, with long periods between tests, it was not possible to define precisely when seroconversion occurred. However, our findings are compatible with previously published estimates that 95% of infected persons will develop HIV antibodies within 6 months of infection.

HIV Antibodies↗

PubMed1999

Seroprevalence and seroconversion for tick-borne diseases in a high-risk population in the northeast United States.

PURPOSE: To determine the prevalence of serologic reactivity, the 1-year incidence of seroconversion, and the frequency of multiple infections, and their associations with symptoms in a group of volunteers at high risk for tick-borne infections in New York state. METHODS: We performed a seroepidemiologic study of Lyme borreliosis, 2 of the ehrlichioses, Rocky Mountain spotted fever, and babesiosis among 671 participants who lived or worked in a high-risk area (mainly in eastern Long Island, New York) for tick-borne diseases. Sera were collected in the winters of 1994 and 1995. Signs and symptoms of tick-borne disease were monitored monthly by mail and telephone. Lyme borreliosis serologies were done by enzyme-linked immunosorbent assay and Western blot. Rocky Mountain spotted fever serologies were initially screened using Dip-S-Ticks, followed by specific indirect immunofluorescence. Ehrlichiosis serologies were determined by epifluorescent microscopy, as were antibodies to Babesia microti. RESULTS: Of the 671 participants, 88 (13%) had antibodies to > or = 1 tick-borne organisms, including 34 (5% of the total) with antibodies to Borrelia burgdorferi. Twenty-seven participants had evidence of exposure to B. burgdorferi at baseline. Seven participants (1%) seroconverted during the course of the study, 5 of whom were symptomatic for Lyme borreliosis. Antibodies to spotted fever group rickettsiae were seen in 28 participants (4%), 22 of whom were positive at baseline and 6 of whom seroconverted during the observation period. None of the seropositive patients had any symptoms or signs of infection. Twenty-four participants (3%) had serologic evidence of exposure to Ehrlichia (all but one to Ehrlichia equi); 5 (0.7%) seroconverted during the observation period, including 3 subjects who were asymptomatic. Antibodies to B. microti were seen in 7 participants (1%), including one asymptomatic seroconversion during the year of observation. There was evidence of possible dual infection in 5 patients. CONCLUSION: In a high-risk population, there was evidence of exposure to 5 tick-borne pathogens; however, many infections were asymptomatic, and coinfections were rare.

Babesiosis↗

PubMed2003

Exposure to low infective doses of HCV induces cellular immune responses without consistently detectable viremia or seroconversion in chimpanzees.

In hepatitis C virus (HCV) infection, there is accumulating data suggesting the presence of cellular immune responses to HCV in exposed but seemingly uninfected populations. Some studies have suggested cross-reactive antigens rather than prior HCV exposure as the main reason for the immune responses. In this study we address this question by analyzing the immune response of chimpanzees that have been sequentially exposed to increasing doses of HCV virions. The level of viremia, as well as the immune responses to HCV at different times after virus inoculation, were examined. Our data indicate that HCV infective doses as low as 1-10 RNA (+) virions induce detectable cellular immune responses in chimpanzees without consistently detectable viremia or persistent seroconversion. However, increasing the infective doses of HCV to 100 RNA (+) virions overcame the low-inoculum-induced immune response and produced high-level viremia followed by seroconversion.

Animals↗

PubMed1985

Acute AIDS retrovirus infection. Definition of a clinical illness associated with seroconversion.

In the course of a prospective immunoepidemiological study of homosexual men in Sydney, seroconversion to the AIDS-associated retrovirus (ARV) was observed in 12 subjects. Review of the clinical files defined an acute infectious-mononucleosis-like illness in 11 subjects. The illness was of sudden onset, lasted from 3 to 14 days, and was associated with fevers, sweats, malaise, lethargy, anorexia, nausea, myalgia, arthralgia, headaches, sore throat, diarrhoea, generalised lymphadenopathy, a macular erythematous truncal eruption, and thrombocytopenia. In 1 subject an incubation period of 6 days after presumed exposure to ARV was determined and in 3 subjects seroconversion took place 19, 32, and 56 days after onset. Comparison of T-cell subsets before and after the acute illness showed inversion of T4:T8 ratio in 8 subjects, due to increased numbers of circulating T8+ cells. These findings support the notion of an acute clinical, immunological, and serological response to infection with ARV which should be considered in the differential diagnosis of mononucleosis-like syndromes in groups at high risk for the development of AIDS.

Acquired Immunodeficiency Syndrome↗

PubMed1987

Long latency precedes overt seroconversion in sexually transmitted human-immunodeficiency-virus infection.

Signs of latent HIV infection were sought in stored serum samples collected before overt seroconversion, confirmed by enzyme-linked immunosorbent assay (ELISA), from 9 subjects with human-immunodeficiency-virus (HIV) infection, in serum from 25 seronegative sexual partners of HIV-seropositive men and from 23 other seronegative, homosexually active men. Free HIV antigen and/or low-titre antibodies to recombinant structural (core, env) or non-structural (3' orf, sor, tat) proteins were seen 6-14 months before seroconversion in all 9 subjects who seroconverted. Antibodies against core proteins detected by western blot were usually the first sign of latent HIV infection. 5 of the 25 ELISA-negative exposed partners have shown HIV antigenaemia and antibodies against core proteins for 16-34 months. By in-situ hybridisation, HIV-specific RNA was detected in peripheral-blood non-lymphoid mononuclear cells in some of the latently infected partners. All subjects with latent HIV infection had normal numbers of T4 lymphocytes but half of them lost their in-vitro proliferative T-cell response to a recall antigen (purified protein derivative of tuberculin). Early HIV infection, characterised by a low-level and restricted antibody response towards HIV core and regulatory proteins, seems mainly to affect antigen-presenting cells.

Acquired Immunodeficiency Syndrome↗

PubMed1999

'Naïve' and 'memory' CD4+ T-cells and T-cell receptor (TCR) V beta repertoire dynamics are independent of the levels of viremia following HIV seroconversion.

The progression of 'naive' and 'memory' T-cells and the T-cell receptor Vbeta (TCR Vbeta) repertoire dynamics within the peripheral CD4+ T-cell compartment were studied in individuals following HIV seroconversion. Profound TCR Vbeta repertoire perturbations were observed within the CD4+ T-cell pool in treatment-naive patients regardless of their levels of viremia during the first 6-8 months after seroconversion. The ratio of 'naive' to 'memory' CD4+ T-cells as well as the TCR Vbeta repertoire dynamics did not appear to correlate with absolute numbers of CD4 T-cells.

Adolescent↗

PubMed2003

Reconciling HIV incidence results from two assays employed in the serological testing algorithm for recent HIV seroconversion (STARHS).

The Abbott HIVAB and Vironostika HIV-1 Microelisa assays have both been validated for use in the serological testing algorithm for recent HIV seroconversion (STARHS). This ability to identify recently-acquired infection provides valuable insight into the epidemic. The availability of each assay during different periods led to longitudinal studies of annual HIV incidence being based on a mixture of results from each. We investigated whether results from both assays could be reconciled. Using statistical methods, the correlation of the two assays' results and other performance characteristics were examined. Of 378 anti-HIV-1 positive specimens examined by both assays, the Abbott assay flagged 40 as from recent infections, whereas Vironostika flagged 50. The correlation coefficient between screening reactivities in each assay was 0.84, and 0.77 in confirmatory mode. Abbott screening results were significantly higher than its confirmatory results, and some specimens from recent infections may consequently have gone undetected by that assay. This problem was not found with the Vironostika assay. Observational data indicated that the estimated HIV incidence derived from HIVAB results increased as the assay threshold, with its pre-defined seroconversion window, was increased. For Vironostika, the estimated HIV incidence remained stable over a wide range of thresholds. Modelling of the observed relationship between the two assays allowed an estimate of the equivalent threshold in the alternative assay, thus providing a means of reconciling results. Our findings suggest that the Vironostika assay is more reliable than the HIVAB, is easier to use, and is able to allow processing of more specimens per run.

Algorithms↗

PubMed2003

Transmission and control implications of seroconversion to Maedi-Visna virus in Basque dairy-sheep flocks.

A retrospective analysis of seroconversion to Maedi-Visna virus (MVV) was carried out for 10 infected semi-intensively reared dairy-sheep flocks that were tested annually between 1994 and 1999. Four of the flocks raised replacement lambs artificially with bovine colostrum and milk replacement to avoid lactogenic MVV infection but did not prevent aerosol contact between replacements and other sheep in the flock. Flock culling percentages ranged between 14 and 25% and in eight flocks the number of sheep that seroconverted was similar to or lower than the number of sheep culled--suggesting that incidence could be reduced by culling seropositive sheep without increasing average culling percentages. Random-effects logistic regression indicated that seroconversion was associated positively with increasing contact with infected sheep and with lifetime MV-serological status of the dam (used as a proxy measure of genetic susceptibility), but not with mode of rearing pre-weaning (artificially or with a seropositive or seronegative dam). Our results indicate that when conditions allow efficient horizontal transmission, there is no evidence that lactogenic infection increases the risk of MV infection and that there is an important inheritable component of disease resistance or susceptibility.

Animal Husbandry↗

PubMed1997

Association between risk of seroconversion of sentinel cattle to bluetongue viruses and Culicoides species (Diptera: Ceratopogonidae) in Queensland, Australia.

The association between risk of seroconversion of sentinel cattle to bluetongue viruses and the number of Culicoides brevitarsis Kieffer and C. wadai Kitaoka caught by light traps was investigated using survival analysis. Eight sentinel herds that seroconverted to bluetongue viruses between 1990 and 1994, and for which insect-trapping data were available, were selected for inclusion in the study. These herds were located at six sites along the eastern coast of Queensland, Australia, from approximately latitude 10 degrees South to 25 degrees South. C. brevitarsis was detected at all locations where sentinel herds were maintained, whereas C. wadai was detected at only two locations in northern Queensland where four sentinel herds were maintained during the study period. The mean number of C. brevitarsis and C. wadai caught per month was 230 and 21, respectively. A significant (P = 0.05) positive association was found between the risk of seroconversion of sentinel cattle to bluetongue viruses and the number of C. wadai caught in the same month.

Animals↗

PubMed1986

Diverse virological, histopathological and prognostic implications of seroconversion from hepatitis B e antigen to anti-HBe in chronic hepatitis B virus infection.

The evolutions of serum hepatitis B virus (HBV)-DNA, liver histology and intrahepatic expressions of HBV antigens were longitudinally investigated in 24 serum HBeAg+/HBV-DNA+ chronic hepatitis B patients who subsequently seroconverted to anti-HBe. After HBeAg conversion, serum HBV-DNA still persisted in 10 patients, and liver HBcAg in 7 of them. Of the 24 patients, 3 subgroups with diverse prognoses were identified. Ten patients progressed from chronic active hepatitis to cirrhosis, and in 7 of them HBV-DNA and/or HBcAg persisted. Eight patients with undetectable HBV-DNA and HBcAg recovered. In the remaining 6 patients, chronic liver diseases persisted; in 3 of them, HBV-DNA and in one HBcAg. These findings indicate that continued viral replication is present in a significant number of patients after HBeAg seroconversion in Taiwan, and is responsible for disease progression. In addition to HBcAg and HBV-DNA, the severity of underlying liver histology, when HBeAg seroconversion occurred, was critical for the outcome of the disease. Another remarkable finding was that clusters of ground-glass hepatocytes, well correlated with the marginal expression of HBsAg, were demonstrated in 14 of 16 biopsies with serum anti-HBe+/HBV-DNA-, but found in only 4 of 44 biopsies with positive serum HBV-DNA, indicating a strong association of the expressions of liver histology and hepatocyte HBsAg with the status of viral replication.

Chronic Disease↗

PubMed2003

Modulating gene expression using DNA vaccines with different 3'-UTRs influences antibody titer, seroconversion and cytokine profiles.

To determine if modulating the amount of foreign antigen produced by a DNA vaccine can influence the overall intensity and cytokine polarization of the ensuing immune response, three different plasmids, each encoding the hepatitis B (HB) surface antigen, were constructed. In each construct, HBs gene expression was driven by the cytomegalovirus immediate early promoter, but differed in the 3'-untranslated regions (3'-UTR) containing the polyadenylation sequence. These 3'-UTR sequences were derived from either the hepatitis B virus (HBVpA), bovine growth hormone (BGHpA), or rabbit beta-globin (betapA). BALB/c mice were immunized intramuscularly with equimolar amounts of each plasmid and blood was collected bi-weekly. Following immunization, total IgG titers correlated with in vitro antigen production levels (from transfected CHO cells), as evidenced by the following response pattern: HBVpA>BGHpA>>betapA. All groups demonstrated a heavy bias toward a Th1 immune response, as evidenced by high serum IgG2a/IgG1 ratios and the predominance of IFN-gamma over IL-4 secretion from cultured splenocytes. In addition, the HBVpA construct resulted in a seroconversion rate of 100%, in comparison to 40-50% in the BGHpA, and 0% in the betapA group. Surprisingly, splenocytes isolated from mice immunized with the betapA construct secreted the highest levels of IFN-gamma. Taken together, these findings suggest that altering the level of gene expression not only affects the overall titer and seroconversion rates of vaccinated animals, but also may play a role in modulating cytokine profiles.

3' Untranslated Regions↗

PubMed2003

Pregnancy as a risk factor for acute toxoplasmosis seroconversion.

OBJECTIVE: To test the hypothesis that pregnancy is a risk factor for toxoplasmosis seroconversion. MATERIALS AND METHODS: A prospective observational study of women at child-bearing age vulnerable to Toxoplasma gondii. Serological reactions with indirect immunofluorescent antibody and immunoenzyme tests were used. The risk estimate used limits of reliability at 95%, and the results were validated by chi(2) and RR tests. RESULTS: Acute infection among pregnant women was 8.6% (45/522), and pregnancy was confirmed to be a risk factor for seroconversion (P=0.001). Living in close contact with host animals and vehicles of oocyst transmission proved to be a statistical risk for pregnant women to seroconvert, which was aggravated in adolescents. CONCLUSION: Gestation, potentiating susceptibility to this infection, points to the need of primary and secondary prevention for all pregnant women at risk.

Adolescent↗

PubMed1996

Comparison of the sensitivity of four rapid assays for the detection of antibodies to HIV-1/HIV-2 during seroconversion.

OBJECTIVES: To compare the sensitivity of four rapid assays for the detection of antibodies against HIV-1 during early seroconversion. METHODS: Four rapid assays for the detection of antibodies to HIV-1/HIV-2 (SUDS HIV 1 + 2, TestPack HIV-1/HIV-2, HIV-SPOT and CAPILLUS HIV-1/HIV-2) were evaluated on 38 sera derived from 14 HIV-1 seroconverters, formerly tested with Abbott second- and third-generation HIV-1/HIV-2 enzyme immunoassay (EIA) and Diagnostic Biotechnology HIV blot 2.2. EIA-negative sera had also been investigated by HIV-1 antigen testing and polymerase chain reaction (PCR) analysis detecting HIV-1 proviral DNA. RESULTS: On 16 sera which were Abbott second-generation EIA negative, the SUDS assay rated highest with six positive results. Four sera were TestPack positive. No specimens in this group were HIV-SPOT positive or CAPILLUS positive. Of the remaining 22 sera (Abbott second- and third-generation EIA positive), all but two were positive in all tests. CONCLUSIONS: The study revealed differences in the sensitivities of the rapid assays in the early phase of seroconversion. The most sensitive assay, SUDS, was even more sensitive than the Abbott third-generation EIA, while TestPack and the EIA were equally sensitive. Based on these findings, we suggest the inclusion of these assays in the supplemental testing for detection of antibodies to HIV.

HIV Antibodies↗