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Results for “seroconversion”

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PubMed2007

Timing of seroconversion and acquisition of positive polymerase chain reaction assay results in calves experimentally infected with bovine leukemia virus.

OBJECTIVE: To determine the interval to provirus and serum antibody detection (via PCR assay and ELISA, respectively) in calves after experimental inoculation with bovine leukemia virus (BLV). ANIMALS: 8 colostrum-deprived, BLV-negative Holstein bull calves (> or = 6 weeks old). PROCEDURES: Via IM injection, each calf received a fresh whole-blood inoculum (day 0) calculated to contain 2 x 10(6) lymphocytes. Blood samples for the ELISA and PCR assay were collected from calves immediately prior to inoculation and weekly thereafter for 7 weeks. Mean and median number of weeks to PCR-detected conversion of BLV status and seroconversion were calculated. Point sensitivity and cumulative sensitivity of the 2 assays were calculated at each sample collection. At each sampling time, the proportion of calves identified as infected by the cumulative weekly ELISA and PCR assay results was compared by use of a Fisher exact test. RESULTS: In 5 calves, conversion of BLV status was detected via PCR assay before seroconversion was identified. However, seroconversion preceded PCR-detected conversion in 2 calves. In 1 calf, both assays yielded positive results at the same test date. These differences were not significant. CONCLUSIONS AND CLINICAL RELEVANCE: In experimentally inoculated BLV-negative calves, conversion of BLV status was detected via PCR assay more quickly than via ELISA; this difference was not significant and probably not clinically important. The PCR assay may be useful as a confirmatory test in animals of exceptional value; tests based on viral identification may become critically important if vaccines against BLV infection are developed and marketed.

Animals↗

PubMed2005

Efficacy of spray-drying to reduce infectivity of pseudorabies and porcine reproductive and respiratory syndrome (PRRS) viruses and seroconversion in pigs fed diets containing spray-dried animal plasma.

Three experiments were conducted to evaluate viral inactivation by the spray-drying process used in the production of spray-dried animal plasma (SDAP). In Exp. 1, bovine plasma was inoculated with pseudorabies virus (PRV) grown in PK 15 cells. Three 4-L batches were spray-dried in the same manner and conditions of industrial SDAP production but with laboratory spray-drying equipment. Presence of infectivity was determined before and after spray-drying by microtiter assay in PK 15 cell cultures. Before spray-drying, all three samples contained 10(5.3) tissue culture infectious dose50 (TCID50)/mL of PRV. After four consecutive passages, no viable virus was detected in samples of spray-dried bovine plasma. In Exp. 2, bovine plasma was inoculated with porcine respiratory and reproductive syndrome (PRRS) virus propagated previously in MARC cell culture to provide approximately 10(6.3) TCID50/mL. Three 4-L batches were spray-dried in the same manner as Exp. 1. Before spray-drying, samples contained TCID50 of 10(4.0), 10(3.5), and 10(3.5)/mL, respectively. After four consecutive passages in MARC cell cultures, no viable virus was detected in spray-dried bovine plasma. In Exp. 3, 36 weaned piglets (28 d of age) were fed a common diet for 14 d and were determined to be negative for PRV, PRRS, and porcine parvovirus titer. Afterwards, pigs were allotted to six pens with six pigs per pen and fed diets containing either 0 or 8% SDAP (as-fed basis) for 63 d. The SDAP used in the feed contained antibody (titer 1:400) against porcine parvovirus. Blood samples were collected from pigs on d 0 and 63 to determine whether feeding SDAP caused seroconversion and development of antibodies against parvovirus, PRRS, or PRV. Inclusion of SDAP in the diet improved growth of pigs without seroconversion. Spray-drying conditions used in this study were effective in eliminating viable pseudorabies and PRRS viruses from bovine plasma. In this study, feeding SDAP that contained functional antibodies did not promote seroconversion in naïve animals.

Abattoirs↗

PubMed1997

Hepatitis C virus seroconversion rate in a hyperendemic area of HCV in Japan: a prospective study.

We have studied the prevalence, seroconversion rate of anti-hepatitis C virus (HCV), and the transmission of HCV in a cohort of individuals living in a hyperendemic area of HCV in Japan. We investigated 509 subjects, of which 375 could be studied again after 5 years. A remarkable high prevalence of anti-HCV (23.4-24.0%) was observed. Of 287 subjects negative at the first examination in 1990, 4 became positive until the second in 1995 (seroconversion rate: 0.28% per year). Furthermore, we investigated the route of transmission in HCV seroconverted subjects through a detailed interview. All of the HCV seroconverted subjects had past histories of medical treatment. Seroconversion rates of HCV in a hyperendemic area of HCV, were extremely high. Medical treatment was considered to be a causative route of HCV transmission.

Adult↗

PubMed1993

HIV-1 seroconversion in patients with and without genital ulcer disease. A prospective study.

OBJECTIVE: To determine the relative risk for human immunodeficiency virus (HIV-1) seroconversion in patients with and without genital ulcers caused by chancroid, syphilis, and herpes. DESIGN: A prospective cohort study. SETTING: An inner-city, sexually transmitted disease clinic. PATIENTS: Patients seronegative for HIV-1 with and without genital ulcers who were followed for a minimum of 3 months. INTERVENTIONS: Questionnaire to obtain data on demographics, sexual behavior, and illicit drug use; testing for HIV-1 at entry and at a minimum of 3 months after entry; medical examination for the presence or absence of genital ulcer disease. RESULTS: Overall, 758 heterosexual men with no history of injection drug use completed the study; HIV-1 seroconversion occurred in 10 of 344 (2.9%; 95% CI, 1.4% to 5.3%) men with a genital ulcer and in 4 of 414 (1%; CI, 0.2% to 2.5%) without a genital ulcer (relative risk, 3.0; P = 0.05). In a multiple logistic regression analysis, those men with chancroid and a new sexually transmitted disease during follow-up each had about three times the risk for HIV-1 seroconversion (P < or = 0.04). CONCLUSIONS: In this group of heterosexual men, chancroid and repeated acquisition of sexually transmitted diseases appeared to facilitate the sexual transmission of HIV-1.

Adult↗

PubMedDate not supplied

Relationship between age of flock seroconversion to hemorrhagic enteritis virus and appearance of adenoviral inclusions in the spleen and renal tubule epithelia of turkeys.

A retrospective study was conducted to evaluate the temporal relationship between flock seroconversion to hemorrhagic enteritis virus (HEV) and the appearance of adenoviral inclusions in the spleen and renal tubular epithelium. The study was conducted on samples of turkey poults submitted to the Fresno Branch of the California Veterinary Diagnostic Laboratory System during May to December 1988. The study included 78 submissions (four to eight poults per submission) of ages ranging from 6 to 15 weeks. Sera were tested for antibodies to HEV using the agar gel immunodiffusion test. Spleen and kidney samples were examined by light microscopy for the presence of inclusions in the mononuclear phagocytes of the spleen or in the renal tubular epithelium of the kidney. Logistic regression statistical analysis was used to evaluate the association between the age of the bird and the likelihood of the presence of inclusions in the spleen and kidney, as well as the likelihood of seroconversion to HEV. A significant association (P less than 0.05) was found between the presence of splenic inclusion bodies and the age of the bird. The probability of splenic inclusions was higher in younger birds (6 weeks of age), and decreased as the birds became older, approaching zero at 11 weeks of age. The kidney inclusions were significantly associated with age. The probability of detecting the inclusions increased with age, reached a maximum at 10 weeks, and then declined, approaching zero by 14 weeks. However, the probability of seroconversion to HEV increased significantly with age up to 10 weeks and then remained positive throughout the remainder of the study period.

Adenoviridae Infections↗

PubMed1992

[Anti-HBs-F(ab)'2 to the seroconversion of HBsAg carriers].

The exogenous anti-HBs-F(ab)'2 was given to the HBsAg carriers for the study of its effect of seroconversion in vivo. 30 HBsAg carriers, with a duration of 2-15 years (HBeAg positive 18 and anti-HBe positive 12) were studied after intramuscular infection of anti-HBs-F(ab)'2. In the HBeAg group, the cut off value of HBeAg decreased significantly (P < 0.01) in 18 carriers, of which 6 seroconversed to anti-HBe, all the HBe-Ag carriers had a high S/N ratio of anti-HBs-anti-Id (RIA) but after 12-week treatment the ratio decreased significantly (P < 0.01). Six of 18 HBV DNA positive carriers conversed to negative (33%) and 8 of 13 DNA-P positive conversed to negative (61%). 12 anti-HBe positive carriers showed no seroconversion.

Adolescent↗

PubMed1992

Reported seroconversions to human immunodeficiency virus among workers worldwide--a review.

The authors undertook a review of published articles on reported worldwide seroconversions to the human immunodeficiency virus (HIV) among workers who sustained occupational exposure to HIV. Documented seroconversions are occupational exposures for which the worker is tested and found negative for HIV antibody shortly after the exposure (usually within 30 days). The worker may develop symptoms of a retroviral illness, and seroconversion occurs usually within six months. In all cases the worker is interviewed to determine that there were no other risk factors for infection. Review of the literature identified 16 parenteral exposures (needlesticks or cuts with a sharp object), two mucous membrane exposures, two nonintact skin exposures and one cutaneous exposure to infected blood or body fluids.

Aged↗

PubMed1992

Disease progression and early predictors of AIDS in HIV-seroconverted injecting drug users. The Italian Seroconversion Study.

OBJECTIVE: To evaluate the risk of developing AIDS and to identify early markers of disease progression in injecting drug users (IDU). DESIGN: Prospective study. SETTING: Sixteen centres throughout Italy. PATIENTS, PARTICIPANTS: Four hundred and sixty-eight IDU for whom it was possible to estimate the date of HIV seroconversion. MAIN OUTCOME MEASURES: Progression to AIDS. RESULTS: Twenty-six subjects developed AIDS during a median follow-up period of 42 months. The risk of developing AIDS was 21% within 7 years following seroconversion. Age greater than 25 years at seroconversion was associated with more rapid disease progression. Progression was similar for men and women. Continued drug injection did not accelerate progression to AIDS. Among the laboratory markers studied, CD4+ cell count at the first HIV-positive test was the best predictor of disease progression. Results were confirmed using multivariate analysis. CONCLUSIONS: Our findings indicate the importance of the role played by age in accelerated disease progression, which may be determined by a more rapid decline in CD4+ cell number in older HIV-infected IDU.

Acquired Immunodeficiency Syndrome↗

PubMed2005

[Persistence of hepatitis B virus in children after interferon-alpha therapy despite the seroconversion in HBsAg/anti-HBs system].

OBJECTIVE: The aim of our study was to assess: (1) whether seroconversion to IgG anti-HBs, induced by IFN-alpha therapy in children with chronic active hepatitis B, is maintained 4-10 years after treatment; and (2) whether HBV-DNA is present in circulation despite the synthesis of anti-HBs. METHODS: Serum samples were collected from 38 patients and serological markers of HBV were determined in each of them. HBV-DNA was determined by PCR in anti-HBs positive sera. Serum samples obtained from 19 subjects with a complete spontaneous seroconversion after acute HBV served as controls. RESULTS: Four to 10 years after therapy, anti-HBs were present in ca. 97.4% patients with GMT value of 775 IU/L vs 127 IU/L found in controls. HBsAg was found in 2/38 subjects. In 13 out of 37 patients (35.1%) free and/or bound HBV-DNA was present. CONCLUSIONS: This study showed that seroconversion induced by IFN-alpha may not be a sustained phenomenon. HBV-DNA may persist for a long time after therapy despite the anti-HBs synthesis.

Adolescent↗

PubMed2006

[A case of repeated seroconversion to HBe antibody due to co-infection with Mutant- and wild-type hepatitis B virus clones].

It is reported that co-infection with different hepatitis B virus (HBV) clones in a patient with chronic hepatitis B induces rare serotypes (adywr) or abnormal laboratory data such as negative HBs antigen, in the presence of positive HBV DNA. In this study, we experienced a case of repeated seroconversion to HBe antibody in a patient with chronic hepatitis B. Since seroconversion is considered to be related to genetic mutations, we investigated the HBV genes in this male patient in his 30's. We amplified and cloned parts of the HBV genes by the polymerase chain reaction (PCR), and sequenced the PCR products. As a result, mutated HBV genes were found in the serum of each specified period. By DNA sequencing we confirmed the coexistence of different HBV clones (wild-type clone and pre-S deletion mutant) and that both clones had the same genotype C. These clones took turns to be dominant; when the wild-type clone was dominant, HBe antigen was positive, and when the mutant clone was dominant, HBe antibody was positive. These findings demonstrated that repeated seroconversion of HBe antigen to HBe antibody was induced by co infection with mutant- and wild-type HBV clones. It is interesting that increased aspartate aminotransferase (AST) and alanine aminotransferase (ALT) was noted at the time of the change from positive wild-type HBV clone to positive mutant clone.

Adult↗

PubMed2006

HIV seroconversion illness - latest HIV assays may still be negative.

Human immunodeficiency virus (HIV) seroconversion illness occurs in up to 80% of patients who newly acquire the virus. It is hoped that the new fourth generation HIV assay will have improved sensitivity for diagnosis. This article describes the case of a patient who presented with typical symptoms of HIV seroconversion illness but who had a negative initial test with the new assay. Current management of HIV seroconversion illness is also outlined.

Adult↗

PubMed1990

[Immunogenetic factors influencing HBV carrier state, the seroconversion and the development of chronic liver disease].

In order to investigate the immunogenetic factors associated with hepatitis B virus (HBV) carrier state, the HBe seroconversion and the development of chronic liver disease, HLA typing were performed in 278 asymptomatic HBV carriers (ASC) and 110 patients with chronic B type hepatitis (CH). HLA typing was also performed in 178 vaccinees who had received hepatitis B vaccine. The significantly decreased frequencies of DR1 and DRw13 were found in ASC, CH and non-responders to HB vaccine. This suggests that DR1 and DRw13 may be associated with the elimination of HBV. The frequency of DR4.2 was increased in ASC, but decreased in CH. The seroconversion rate of DR4.2 positive CH as well as ASC was high. Therefore DR4.2 may have relevance to the seroconversion from HBeAg to anti-HBe.

Carrier State↗

PubMed1989

[Seroconversion with trivalent Sabin vaccine in children less than four years of age].

A group of 58 children under 4 years old, were vaccinated with trivalent oral poliovirus vaccine Sabin (OPV), in two sanitary areas of Chiapas, Mexico. The complement of procedures for the maintenance of the cold chain, and the changes in the potency of the vaccine prior and after the vaccination were evaluated. Nurses got a blood sample of 3cc and other one, four weeks after vaccination in order to evaluate the seroconversion rate attributable to Sabin vaccine, which was analyzed through neutralization serologic test. Moreover the investigation team got a sample of feces one day prior to vaccination and other one every week in the following three weeks to vaccination date in order to isolate the poliovirus in the feces of the children. The high pre-vaccination seropositivity suggests that in these areas exist a wide circulation of poliovirus, which probably were vaccine viruses and in less proportion wild viruses. The seroconversion rates were low for the three types of poliovirus, nevertheless 83% of the children had at least one of the three possibilities of seroconversion: unique, double or triple. Children with pre-vaccine seropositive probably had a secondary immune response.

Antibodies, Viral↗

PubMed1989

Patterns of T lymphocyte changes with human immunodeficiency virus infection: from seroconversion to the development of AIDS.

CD4 and CD8 T lymphocytes of three groups of men infected by the human immunodeficiency virus (HIV) were examined twice yearly for 36 months to elucidate the temporal trends in T lymphocytes during infection. The three groups were 37 HIV seroconverters, 304 prevalent HIV seropositives remaining free of the acquired immunodeficiency syndrome (AIDS), and 69 men who developed AIDS during observation. Six months before seroconversion, CD4 levels were similar among HIV seroconverters and 356 seronegative controls. Within 18 months of seroconversion, mean CD4 levels fell to the level of the prevalent seropositives at study entry. From there, the rate of decline slowed. CD8 lymphocyte counts rose dramatically at seroconversion. Among AIDS-free prevalent seropositives, CD4 levels fell steadily over 36 months of observation. By contrast, CD8 cell levels rose slowly. Among men who developed AIDS, mean CD4 levels fell more rapidly again during the 18 months prior to diagnosis. CD8 cell levels remained elevated until 6-12 months before diagnosis, when they began to fall.

Acquired Immunodeficiency Syndrome↗

PubMed1987

Immunologic aberrations, HIV seropositivity and seroconversion rates in patients with hemophilia B.

Because there have been reports that factor IX concentrate is less immunosuppressive and therefore factor IX users have less immunologic aberrations, we have studied a group of 22 patients with hemophilia B and six patients with factor VIII deficiency and high titer inhibitors with respect to lymphocyte numbers and function, human immunodeficiency virus (HIV) serology, and factor usage. This group was compared to 111 patients with hemophilia A and a group of 28 healthy male volunteer controls. When the study began in 1983, the majority of patients with hemophilia B and with higher titer factor VIII inhibitors were seronegative, 77% and 83% respectively, as compared to only 30% of patients with hemophilia A. At that time the factor IX users also had milder immune aberrations than the hemophilia A group. However, with time and increasing clotting factor concentrate usage, seroconversion and more striking abnormalities in immune function have occurred in the hemophilia B group. In a subgroup of 16 patients with hemophilia B studied twice, the incidence of seropositivity increased from 31% in 1983 to 69% in 1985. We thus conclude that factor IX concentrate in itself is not less immunosuppressive than factor VIII concentrate. Seroconversion in factor IX concentrate users appears to be lagging behind seroconversion in factor VIII concentrate users, perhaps secondary to the lower cumulative dosage of concentrate that patients with hemophilia B utilize.

Adolescent↗

PubMed1988

Seroconversion to Borrelia burgdorferi in a patient with juvenile arthritis in Ontario, Canada.

A seroconversion to Borrelia burgdorferi, the etiological agent of Lyme disease, was documented in a 5 year old girl from central Ontario. Our patient developed juvenile arthritis in January, 1984 when she was 14 months old. It was relatively well controlled with aspirin. Her arthritis flared in April, 1986 at which time seroconversion to B. burgdorferi was demonstrated by indirect immunofluorescence and by enzyme linked immunosorbent assay. She was treated with phenoxymethyl penicillin and has had no further flare of her arthritis. The possible relationship between her rheumatic disease and her seroconversion to B. burgdorferi is discussed.

Arthritis, Juvenile↗

PubMed1987

Oral poliovirus vaccine in tropical Africa: greater impact on incidence of paralytic disease than expected from coverage surveys and seroconversion rates.

During the first 5 years of a poliomyelitis control programme in Yaounde, Cameroon, a maximum of 35% of children aged 12-23 months were estimated to have received three doses of trivalent oral vaccine. Despite this low immunization coverage and low seroconversion rates, which were determined concurrently, the estimated incidence of paralytic poliomyelitis decreased by 85%.A detailed study of immunized children and of children living in the same households suggests that community spread of the vaccine virus and cross-immunity may have partly been responsible for the dramatic decrease in the incidence of paralytic disease, and that competing non-polio enterovirus infection was not a cause for the low seroconversion rates. These results suggest that immunization coverage and seroconversion rates alone are not sufficient criteria for determining the effectiveness of control programmes that use oral poliovirus vaccine in tropical Africa; surveillance of the incidence of paralytic disease must also be carried out.

Antibody Formation↗

PubMed1994

Preparations for AIDS vaccine trials. Retention, behavior change, and HIV-seroconversion among injecting drug users (IDUs) and sexual partners of IDUs.

The likelihood that subjects in human immunodeficiency virus (HIV) vaccine efficacy trials will alter their behavioral risks for HIV infection over time must be considered in evaluating the feasibility of such trials and in estimating the necessary sample sizes to be enrolled. Potential subjects for future vaccine efficacy trials include injecting drug users (IDUs) and others who may be difficult to retain in studies and who may alter HIV-risk-related behaviors substantially over time. We have investigated behavior change, retention, and HIV seroconversion among 577 New York City resident IDUs and sexual partners of IDUs enlisted between July 1 and December 31, 1992. We attempted to see all subjects every 3 months for interviews, blood donation and HIV testing. We were able to retain 68% of subjects in the study through the third scheduled recall at 7.5-10.5 months after enlistment. HIV seroconversion through March 1, 1994, was 1.33/100 person-years at risk. There was a significant inverse relationship between HIV seroconversion and retention at the 9-month recall after adjusting for age, gender, and the amount of locator information provided by subjects at enlistment. Among subjects seen at each of the scheduled visits at 3, 6, and 9 months after enrollment, modest but statistically significant behavior changes that reduced risk were observed in self-reported drug injection frequency, heroin injection frequency, sexual contact with IDUs, and sharing of needles/syringes. The magnitude of these changes in risk, however, was small and may be transient. The behavior changes observed to date do not appear to be large enough to substantially alter calculations of sample sizes needed in future HIV vaccine efficacy trials.

AIDS Vaccines↗