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PubMed2003

Seroconversion after measles vaccination at nine and fifteen months of age.

BACKGROUND: Despite high vaccination coverage, single dose measles immunization programs have been unsuccessful in eliminating the disease. Because seroconversion rates are lower in infants vaccinated before 12 months of age, a second dose of measles vaccine is recommended at 15 months. The aim of this study was to determine the seroconversion rates in children after the first and second doses of measles vaccinations at 9 and 15 months of age. METHODS: Study population comprised 116 infants attending the Well Baby Clinic of Istanbul University, Faculty of Medicine. Serum specimens were obtained from children before and 1 month after the first measles (Rouvax, Schwarz strain 1000 TCID(50)) vaccine given at 9 months. A second dose was given to 72 children at 15 months of age as measles-mumps-rubella (Trimovax, Schwarz measles strain, 1000 TCID(50); Urabe Am 9 mumps strain, 5000 TCID(50); Wister RA 27/3 rubella strain, 1000 TCID(50)). Third blood samples were collected 20 months after the second vaccine. RESULTS: Passive antibody positivity rate was 5.2% at the age of 9 months. Seroconversion rate was 77.6% after the first dose and 81.9% after the second dose of measles vaccine. Of 15 children who were seronegative, 13 (86.7%) became seropositive after the immunization at 15 months. Eleven children (19.2%) seroconverted from positive to negative after the second vaccine. CONCLUSION: The two dose schedule seems to increase the seropositivity rate. Our findings also indicate that increasing vaccination coverage and revaccination at 6 years of age are important even with the early two dose schedule.

Antibodies, Viral↗

PubMed2006

Hepatitis C virus eradication followed by HBeAg to anti-HBe seroconversion after pegylated interferon-alpha2b plus ribavirin treatment in a patient with hepatitis B and C coinfection.

In hepatitis B or hepatitis C endemic areas, the number of patients with dual infections is substantial. In such patients, interferon-alpha plus ribavirin can achieve sustained hepatitis C virus (HCV) clearance and hepatitis B e antigen (HBeAg) seroconversion. Pegylated interferon (PegIFN), an established treatment for hepatitis C, is currently increasingly recognized as an efficient therapy for hepatitis B. No case of successful use of PegIFN plus ribavirin has yet been reported, however, in hepatitis B virus (HBV) and HCV coinfection. We report on a 32-year-old man, of Kampuchean origin, with chronic hepatitis B, as documented by the presence of hepatitis B surface antigen with HBeAg, who was coinfected with HCV genotype 1. On therapy with PegIFN-alpha2b plus ribavirin, HCV RNA became undetectable at week 17. At the end of the 48 weeks of treatment, HCV RNA was still undetectable, HBV DNA was reduced and HBeAg remained positive. Twelve weeks after the end of treatment, HBV DNA reduction was followed by HBeAg to anti-HBe seroconversion. Two years after the end of treatment, HCV RNA and HBV DNA were still undetectable, and HBeAg to anti-HBe seroconversion was maintained. We conclude that the combination of PegIFN plus ribavirin may induce suppression of both viral infections.

Adult↗

PubMed2005

A prognostic model for HIV seroconversion among injection drug users as a tool for stratification in clinical trials.

OBJECTIVE: The main goal of this study was to construct a prognostic model for HIV seroconversion among injection drug users (IDUs) using easy-to-measure risk indicators. DESIGN: Cox proportional hazards regression modeling was used for risk stratification in a heterogeneous population of IDUs with regards to HIV risk-taking behaviors. METHODS: Subjects were recruited in a prospective cohort of IDUs followed between September 1992 and October 2001. A total of 1602 men, seronegative at enrollment with at least 1 follow-up visit, were included in the analyses. Only variables that consistently predict HIV seroconversion in several settings were considered. The final model was used to assign a risk score for each participant. RESULTS: Three risk indicators were included in the risk score to predict HIV seroconversion: unstable housing, average cocaine injections per day, and having shared a syringe with a known HIV-positive partner. Kaplan-Meier survival functions were generated and risk score values stratified in 3 groups. HIV incidence rates per 100 person-years were as follows: 0.91 (95% CI, 0.55-1.52) for the low-risk group, 3.10 (95% CI, 2.49-3.84) for the moderate-risk group, and 7.82 (95% CI, 6.30-9.73) for the high-risk group (log-rank P value < 0.0001). CONCLUSION: If validated in other settings, this risk score may improve the prediction of outcome and allow more accurate stratification in clinical trials.

Adolescent↗

PubMed1995

Low incidence of primary infection with toxoplasma among women in Sheffield: a seroconversion study.

OBJECTIVE: To determine the incidence of primary toxoplasma infection in women of childbearing age. DESIGN: A retrospective study of seroconversion on stored pairs of sera taken for routine antenatal testing. SETTING: The antenatal clinics and general practices of Sheffield between July 1989 and October 1992. SUBJECTS: One thousand six hundred and twenty-one women on whom pairs of sera, separated by more than 500 days, had been received. MAIN OUTCOME MEASURE: Rate of primary infection determined by seroconversion as measured by the presence of antibody in the second serum and its absence in the first. RESULTS: Of 1621 women, 160 (9.9%) were initially seropositive. One seroconversion was detected in 2966 woman years of observation for susceptibles. The projected rate for primary infections was 0.23 (95% CI 0.0059-1.3) per 1000 pregnancies. CONCLUSIONS: The rate is much lower than for earlier estimates of incidence in the UK but agrees with a more recent estimate from Sheffield and suggests a falling incidence.

Disease Susceptibility↗

PubMed1986

Long-term follow-up of 60 patients with chronic hepatitis B. I. Seroconversion in the hepatitis B e-system, frequency of delta infection and histological outcome.

Sixty patients with liver biopsy documented chronic hepatitis B attending Roslagstull Hospital for Infectious Diseases, Stockholm, Sweden, were followed during a mean period of 53 months (range 7-133 months) in order to evaluate the frequency of delta infection and HBeAg seroconversion as well as the histological outcome as assessed by liver biopsy. Spontaneous HBeAg clearance and development of anti-HBe occurred among 17 of 36 initially HBeAg positive patients (47%), corresponding to an annual seroconversion rate of 11%. Biochemical improvement was noted in 7/17 patients (41%) after seroconversion as against in 2/19 patients (10.5%) with HBeAg persistence. Superinfection with the delta agent was seen to be associated with severe liver injury among drug addicts and immigrants with chronic hepatitis B. In the absence of a delta infection, progressive liver disease seemed to be associated with persistence of HBeAg. Although none of the homosexual men studied were delta superinfected, 71% developed chronic active hepatitis (CAH) with or without cirrhosis (CI).

Adolescent↗

PubMed1989

Determination by western blot (immunoblot) of seroconversions to toxic shock syndrome (TSS) toxin 1 and enterotoxin A, B, or C during infection with TSS- and non-TSS-associated Staphylococcus aureus.

Serum antibody responses to toxic shock syndrome (TSS) toxin 1 (TSST-1) and staphylococcal enterotoxins A, B, and C were determined by western blot (immunoblot) analysis of acute- and convalescent-phase paired sera from 18 TSS- and 31 non-TSS-associated Staphylococcus aureus infections. Compared with non-TSS cases, seroconversion to TSST-1 was significantly more frequent among both menstrual (5 of 8 versus 1 of 31; P less than 0.001) and nonmenstrual (3 of 10; P less than 0.05) patients. Seroconversion to staphylococcal enterotoxin A was also more frequent among both menstrual (2 of 8 versus 0 of 31; P less than 0.05) and nonmenstrual (2 of 9; P less than 0.05) TSS patients. In general, patients with TSS associated with TSST-1-positive S. aureus were more likely to seroconvert exclusively to TSST-1 (4 of 12 versus 0 of 6; P = 0.16), whereas those associated with TSST-1-negative S. aureus were more likely to seroconvert exclusively to enterotoxins (3 of 6 versus 0 of 11; P less than 0.05). Concurrent seroconversions to multiple exoproteins were more frequent among both menstrual (3 of 8; P less than 0.05) and nonmenstrual (2 of 9; P less than 0.05) TSS patients compared with persons without TSS (0 of 31). These data suggest but do not prove that enterotoxins (especially staphylococcal enterotoxin A) in addition to TSST-1 may be involved in both menstrual and nonmenstrual TSS. Furthermore, since exposure to multiple exoproteins is more likely to occur during TSS-associated than non-TSS-associated S. aureus infections, the possibility of additive or synergistic effects of these putative toxins in the pathogenesis of TSS should be further explored.

Acute Disease↗

PubMed1987

Prevalent patterns of serotype-specific seroconversion in Mexican children infected with rotavirus.

The level of neutralizing antibodies to rotaviruses belonging to serotypes 1, 3, and 4 was determined in acute- and convalescent-phase sera from 36 Mexican children with rotaviral diarrhea. Most of the infants who seroconverted fell into one of the following three patterns: single seroconversion to serotype 1; seroconversion to serotypes 1 and 4; or seroconversion to all three serotypes tested. The heterotypic neutralizing antibody responses to rotavirus infections are discussed.

Antibodies, Viral↗

PubMed1998

Different hepatitis C virus (HCV) RNA load profiles following seroconversion among injecting drug users without correlation with HCV genotype and serum alanine aminotransferase levels.

Hepatitis C virus (HCV) infection often persists in association with chronic hepatitis. Different factors have been proposed to determine the clinical outcome of HCV infection. The aim of this study was to examine three different factors of HCV infection among injecting drug users. Nineteen untreated HCV seroconverters were tested longitudinally for the presence of HCV RNA by reverse transcriptase (RT) PCR, and results were quantified by the branched-DNA (bDNA) assay. HCV genotypes were determined with the first sample taken after HCV seroconversion. To assess the natural course of infection, serum alanine aminotransferase (ALT) levels were measured at three stages in every individual. The concordance between bDNA and RT-PCR was 98.9%. Three distinct patterns were found, according to the HCV RNA load after seroconversion during a mean follow-up period of 5 years (range, 1 to 8 years). HCV genotype 1a was predominant (52.6%). There was a significant increase in serum ALT levels (mean 55.5 U/liter) in the early phase of HCV infection, compared with basal serum ALT levels before HCV seroconversion and at the end of the follow-up period. Three distinct HCV RNA load profiles were found, without apparent relationship to genotype and serum ALT levels in the first 5 years of HCV infection.

Alanine Transaminase↗

PubMed1997

Autologous and heterologous neutralizing antibody responses following initial seroconversion in human immunodeficiency virus type 1-infected individuals.

In the course of human immunodeficiency virus type 1 (HIV-1) infection, patients develop a strong and persistent immune response characterized by the production of HIV-specific antibodies. The aim of our study was to analyze the appearance of autologous and heterologous neutralizing antibodies in the sera of HIV-infected individuals. For this purpose, primary strains have been isolated from 18 HIV-1-infected subjects prior to seroconversion (in one case) or within 1 to 8 months after seroconversion. Sera, collected at the same time as the virus was isolated and at various times after isolation, have been analyzed for their ability to neutralize the autologous primary strains isolated early after infection, heterologous primary isolates, and cell-line adapted strains. Our neutralization assay, which combines serial dilutions of virus and serial dilutions of sera, is based on the determination of the serum dilution at which a fixed reduction in virus titer (90%) occurs. We have shown that (i) we could not detect autologous neutralizing antibodies in sera collected at the same time as we isolated viruses; (ii) we detected neutralizing antibodies against the autologous strains about 1 year after seroconversion, occasionally after 8 months, but sera were not always available to exclude the presence of neutralizing antibodies at earlier times; (iii) after 1 year, the neutralization response was highly specific to virus present during the early phase of HIV infection; and (iv) heterologous neutralization of primary isolates was detected later (after about 2 years). These results reveal the enormous diversity of neutralization determinants on primary isolates as well as a temporal evolution of the humoral response generating cross-reactive neutralizing antibodies.

Acquired Immunodeficiency Syndrome↗

PubMed1993

Clinical symptoms associated with seroconversion for HIV-1 among misusers of intravenous drugs: comparison with homosexual seroconverters and infected and non-infected intravenous drug misusers.

OBJECTIVE: To study the clinical symptoms associated with seroconversion for HIV-1 among misusers of intravenous drugs. DESIGN: Case-control study in cohorts of drug misusers and homosexual men. SETTING: Outpatient clinic, Municipal Health Service, Amsterdam. SUBJECTS: Misusers of intravenous drugs from our prospective cohort who seroconverted for HIV. Controls were drug users positive for HIV, drug users negative for HIV, and homosexual men who had seroconverted. RESULTS: Five out of 18 (28%) drug users were admitted to hospital with bacterial pneumonia in the four to six months between their last visit at which they were HIV negative and their first visit when they were HIV positive. For comparison none of the 27 homosexual men who seroconverted for HIV, three out of 177 (2%) drug users negative for HIV, and 10 out of 112 (9%) drug users positive for HIV reported bacterial pneumonia. One out of the 18 drug users who seroconverted suffered from oesophageal candidiasis at the time of seroconversion. Other clinical symptoms did not differ between drug users who seroconverted and those who remained negative for HIV, probably due to the high background morbidity among the drug users. CONCLUSIONS: Seroconversion to HIV-1 among intravenous drug misusers is associated with bacterial pneumonia. Those drug users with previously negative test results for HIV who are admitted to hospital for bacterial pneumonia should be tested to detect primary infection with HIV-1.

Bacterial Infections↗

PubMed1996

A case control study of HIV seroconversion in gay men, 1988-1993: what are the current risk factors?

OBJECTIVE: To investigate current risk factors for HIV seroconversion among homo/bisexual men. DESIGN: Matched case control study in a large STD clinic in central London. Data on risk factors were obtained by case note review. METHODS: Fifty-six cases who had at least one negative HIV test followed by a positive test between June 1988 and July 1993, and two homo/bisexual controls (having two or more negative HIV tests) matched to each case on age, total number of HIV tests and test interval period were identified. Univariate and multivariate odds ratio were calculated for acute STD, ano-genital intercourse, condom use and HIV status of sexual partners. RESULTS: Adjusted odds ratios (95% confidence intervals) for HIV seroconversion were 4.1 (1.3-13.3) for having an acute interval STD and 4.6 (1.4-15.4) for having a known HIV infected sexual partner. Compared with men who always used condoms, odds ratios for men who sometimes or never used condoms were 7.9 (2.2-28.9) and 16.2 (3.0-86.0) respectively. Unprotected ano-genital intercourse was commonly reported by both cases and controls, and reported condom use was no greater with a known HIV infected partner than with a partner of unknown HIV status. CONCLUSION: HIV seroconversion among homo/bisexual men attending STD clinics is strongly related to having an acute STD, a known HIV infected partner and not using condoms. Although consistent use of condoms is highly protective, knowing that a partner is HIV infected does not ensure condom use between serodiscordant men. More effective, well-evaluated interventions are needed to reduce sexual risk-taking in this population.

Adolescent↗

PubMed1993

Seroconversion to hepatitis C virus in dialysis patients: a retrospective and prospective study.

The prevalence and incidence of hepatitis C virus (HCV) infections were studied in 236 dialysis patients and related to clinical data at two hospitals in Stockholm, Sweden. Patients were followed during 12 months and tested by 1st- and 2nd-generation anti-HCV assays. Time of seroconversion to HCV could be determined by retrospective analysis of stored serum samples. A total of 36 (15%) patients were anti-HCV positive. Time of seroconversion could be determined for 23 patients and was in the majority of cases associated with blood transfusions, but late seroconversion (more than 6 months after transfusion) as well as lack of transfusion in some cases implied that HCV might be transmitted through dialysis equipment. Persistence of elevated alanine amino-transferase levels for more than 6 months occurred in 17% of anti-HCV-positive patients. In conclusion, routes of transmission in dialysis units have to be further evaluated since routes other than transfusion may occur and diagnosis may be delayed in this group of patients probably due to a poor immunological response.

Alanine Transaminase↗

PubMed1992

Acute exacerbations of chronic type B hepatitis are accompanied by increased T cell responses to hepatitis B core and e antigens. Implications for hepatitis B e antigen seroconversion.

T cell proliferative responses to hepatitis B virus-encoded envelope antigen (S + preS2 + preS1), recombinant core antigen (HBcAg), and natural hepatitis B e antigen (HBeAg) were examined in 22 HBeAg-positive patients with chronic type B hepatitis and 17 healthy hepatitis B surface antigen (HBsAg) carriers. The results showed that HBeAg-positive patients had (a) higher levels of T cell responses to HBcAg/HBeAg than those of healthy HBsAg carriers (P less than 0.001 and P less than 0.01, respectively); (b) a further increase in these T cell responses during acute exacerbations (P less than 0.05 and P less than 0.05, respectively); (c) subsidence in the T cell responses to HBcAg/HBeAg after recovery from acute exacerbations and HBeAg seroconversion, whereas the responses would persist at high levels if the patients did not enter a clinical remission; and (d) low levels of T cell responses to S + preS2 + preS1 either before or after HBeAg seroconversion. The appearance of increasing T cell responses to HBcAg/HBeAg usually occurred in the early phase of acute exacerbations. These findings imply that HBcAg/HBeAg-specific T cells play an important role in the exacerbations of chronic hepatitis B and in HBeAg seroconversion. HBcAg/HBeAg-specific precursor T cell frequencies were serially studied in selected cases by limiting dilution assay. Elevation (two- to fourfold) of HBcAg/HBeAg-specific precursor T cell frequencies contributed to the increase of HBcAg/HBeAg-specific T cell proliferation during acute exacerbations.

Adult↗

PubMed1987

Seroconversion from HBs-Ag to anti-HBs in a case of liver cirrhosis associated with hepatocellular carcinoma.

This paper reports a case of liver cirrhosis associated with hepatocellular carcinoma (HCC) of a woman who was converted from hepatitis B surface antigen (HBs-Ag) positive to antibody against HBs-Ag (anti-HBs) positive in the serum through an immunoregulatory steroid rebound phenomenon. The histology of the biopsy specimen taken before the seroconversion showed an early stage of liver cirrhosis with moderate infiltration of mononuclear cells. At autopsy about 3 years after the seroconversion, the liver tissue free of the tumor was in an early stage of liver cirrhosis. Fibrosis did not advance as compared with the biopsy specimen. In addition, mononuclear cell infiltration decreased remarkably and piecemeal necrosis disappeared after the seroconversion. The immunohistologic examination of hepatocytes demonstrated that positive stainings for HBs-Ag and for hepatitis B core antigen (HBc-Ag) in the biopsy specimen turned to be negative in the autopsy specimen. These facts indicate that the steroid rebound phenomenon eliminated free hepatitis B virus (HBV) in the hepatocytes in the absence of massive necrosis of hepatocytes. HBV-DNA integration was proved in the genome of HCC by molecular hybridization method.

Carcinoma, Hepatocellular↗

PubMed1994

AIDS risk reduction and reduced HIV seroconversion among injection drug users in Bangkok.

Human immunodeficiency virus (HIV) seroconversion was studied in a group of 173 injection drug users in Bangkok, Thailand, who had been previously tested for HIV and were interviewed and retested in the fall of 1989. Ten percent of the group had seroconverted. Two factors protected against HIV seroconversion: having stopped sharing injection equipment in response to the acquired immunodeficiency syndrome (AIDS) and having a regular sexual partner. The association between self-reported deliberate risk reduction and reduced HIV seroconversion among persons continuing to inject illicit drugs indicates that injection drug users can change their behavior in response to AIDS and will accurately report on the behavior change, and that the changes can protect against HIV infection.

Acquired Immunodeficiency Syndrome↗

PubMed1995

Risk factors for HIV-1 seroconversion among injection drug users: a case-control study.

OBJECTIVES: A nested case-control study was conducted in Miami, Fla, to determine risk factors associated with human immunodeficiency virus type 1 (HIV-1) seroconversion among injection drug users. METHODS: The study identified 21 incident cases of HIV-1 infection and 76 unmatched controls from two longitudinal cohorts of injection drug users. One cohort consisted of individuals who originally had been recruited from treatment centers; a second cohort was recruited from the "street." Logistic regression analyses that adjusted for age, gender, and race were performed. RESULTS: The final model determined that the primary independent risk factor that best explained the risk for seroconversion was sharing injection equipment in the year prior to conversion; a marginal risk factor was presence of sexually transmitted disease during this same period. CONCLUSIONS: Both an injection component and a sexual component play a role in seroconversion among injection drug users, although the injection component is much stronger.

Adult↗

PubMed1998

Histories of substance use and risk behavior: precursors to HIV seroconversion in homosexual men.

OBJECTIVES: This study compared history of substance use and episodic use in terms of HIV seroconversion. METHODS: A sample of 337 baseline HIV-negative gay men was followed for 6 years. Bivariate and survival analyses were used to compare 39 converters with nonconverters on substance use behaviors. RESULTS: Seroconverters were consistently more likely to report use of marijuana, nitrite inhalants, amphetamines, and cocaine than nonconverters. Consistent use of nitrite inhalants and amphetamines increases the relative risk of seroconversion, while episodic use does not. Both patterns of cocaine use increase seroconversion risk. CONCLUSIONS: There are three potential mechanisms for an increased risk of conversion due to consistent substance use.

HIV Seropositivity↗

PubMed1987

Short-term prednisolone for inducing seroconversion from hepatitis B e antigen to antibody along with clinical improvement in patients with chronic active hepatitis type B.

Short-term prednisolone therapy was instituted on 27 patients with chronic active hepatitis (CAH) type B, in an attempt to induce seroconversion from hepatitis B e antigen (HBeAg) to the corresponding antibody (anti-HBe). Patients with CAH received a four-week regimen of prednisolone with daily dosage tapering from 40 to 10 mg (total 700 mg). Within one year after the withdrawal of prednisolone, 19 (70%) lost HBeAg and 11 of them (41% of the total) developed anti-HBe, at rates significantly higher than 3 (12%) and 1 (4%) who spontaneously showed respective serological changes among 26 matched controls during one year (p less than 0.001). Within two years after the withdrawal, 21 (78%) lost HBeAg and 19 (70%) developed anti-HBe, in contrast to 6 (23%) and 2 (8%) of controls who showed respective changes during that period (p less than 0.001). Seroconversion to anti-HBe was invariably accompanied by clinical and biochemical improvements along with loss of DNA polymerase from circulation. Elevation in transaminase levels, reflecting the rebound of steroid withdrawal, always heralded and appeared to be required for the seroconversion, but serious aggravation of hepatitis was not encountered in any of the patients.

Adult↗