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Backgrounds: SARS-COV-2 infection is not always correlated with protection. Antibody seroprevalence in unvaccinated individuals, which is usually measured by N-specific antibodies, is not necessarily correlated with protection, while antibodies against S protein show a better correlation with protection due to its neutralizing epitopes. In this study, we tried to improve our conception of the hidden perspective of SARS-COV-2 in epidemiological reports and investigate anti-S antibody prevalence among anti-N antibody-positive asymptomatic and mildly symptomatic patients.
Materials & Methods: Blood samples were collected from asymptomatic or mildly symptomatic volunteer participants and symptomatic hospitalized patients with negative PCR results from May 30 to June 17, 2020. Detection of SARS-COV-2 antibodies was done using an ELISA kit targeting N or S protein.
Findings: Totally, 716 samples from volunteer participants and 81 samples from symptomatic hospitalized patients with negative PCR results were evaluated. The test performance-adjusted seroprevalence (95% CI) of SARS-COV-2 antibody was 17.3% (8.8-25.8%) for anti-N IgG in volunteers and 25.5% (12.8-39.7%) for anti-N and anti-S IgM in hospitalized patients. Among anti-N IgG positive infected individuals, 49.2% (21.4 and 78.8%) were anti-S antibody positive.
Conclusion: The results showed that SARS-COV-2 infection sometimes occurs in individuals without symptoms or with mild symptoms, but in more than half of them, the produced antibody is not protective. The findings of hospitalized patients showed that the combination of IgM assay with real-time PCR improved the disease diagnosis by more than 25% in cases with negative molecular test results.

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Objective: In this study, a SYBR Green real-time RT-PCR assay for quantification of HIV-1 viral RNA was developed. Materials and Methods: This assay was performed based on amplification of the pol region of HIV-1 and product analysis by an ABI 7500 system. We quantified HIV-1 viral load in 26 seropositive patients by this system and the data were subsequently compared with results obtained with a reference technique represented by COBAS AMPLICOR HIV-1 Monitor test. Results: The results demonstrated that this technique could detecte up to 500 HIV-1 RNA copies/ml of plasma. The linearity of this approach was conserved over a wide range of HIV-1 copy numbers (5×102-5×109). Since no positive signal was observed in seronegative volunteers, the specificity of the test was calculated as 100%. Comparison of the results with those obtained by the reference quantification method, revealed a significant correlation between the results (R2= 0.95). Conclusion: On the basis of the most recent recorded cases for HIV-1 infection and AIDS in Iran, the prevalence of this disease is rising rapidly and the situation has been called to be alarming by national health representatives. Determination of HIV-1 viral load in plasma has been considered as the most effective single prediction tool of clinical outcome. Indeed, the development and stabilization of HIV-1 RNA assays have given physicians a unique tool for monitoring HIV-1 patients treated with antiviral drugs. In this study, we have developed a SYBR-Green Real Time RT-PCR assay for quantitative analysis of HIV-1 in infected patients. Since a synthetic RNA standard was used in this assay, the upper limit of detection was detected to be higher than the standard test (5×10 9 versus 7.5×10 5). This can be important in patients with acute high viral load infections. Reproducibility was assessed by Intra assay and Inter assay analysis. Coefficient of variations Ct, in reproducibility tests for Intra assay and Inter assay variability were less than