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    • There are limited studies on antibody responses against HIV

    2021-10-19

    There are limited studies on antibody responses against HIV-1 integrase antigen. According to previous studies, almost 5 percent of individuals infected with HIV never raise anti-integrase Tedizolid HCl mg (Rikhtegaran Tehrani et al., 2015; Chang et al., 1985). If this rate is identical in individuals infected with different subtypes, the error can be resolved by factoring it in the calculation of integrase based HIV incidence assay. But, if the rate of non-reactive patients is not similar in different populations, the consequent error cannot be resolved simply and will require the evaluation of anti-integrase response in different populations. In addition to high conservation and immuno-reactivity, the selected antigen in this study has the advantage of delayed response. According to the study of Fiebig et al., emergence of p31 band in western blot during seroconversion needs 88.6 days on average. As responding to linear epitopes needs more time than conformational ones, we used the denatured form of integrase to increase the potential MDRI (Parekh and McDougal, 2005; Parekh et al., 2001c). Also, detection of high avidity anti-integrase antibodies can be helpful for more extended MDRI. In the current study, we developed and evaluated an immunoassay for detection of IgG subclasses against HIV-1 integrase. The results showed that the majority of anti-integrase IgG subclass against integrase is IgG1. There are a lot of studies for evaluation of antibody responses against HIV-1 antigens, the majority of them focusing on anti-envelope antibodies. According to these studies, the most prevalent IgG subclass produced against envelop antigens is IgG1 (Mergener et al., 1987; Ljunggren et al., 1988; Binley et al., 2008; Wilson et al., 2004). On the other hand, profiling the antibody response to various antigens has shown that IgG3 subclass is produced more frequently against Gag proteins (Broliden et al., 1989) and its titer is higher at seroconversion and then reduces gradually (Wilson et al., 2004; Tomaras and Haynes, 2009; Yates et al., 2011). If these findings can be extended to anti-integrase antibodies, low titer of subclasses of IgG2, 3 and 4 in long-term infected individuals is not surprising. According to our results, the specificity of BED-EIA and LAg-Avidity assays is 85.9 and 98.7%, respectively. The low specificity of the BED-EIA in the studied population may be due to the antigen used for this assay, covering only subtypes B, E and D (Parekh et al., 2001b). In contrast, the exploited antigen in LAg-Avidity covers a wider range of HIV subtypes, including A, B, C, D, F, G, H, J, K and recombinants AG, AB, AC, BF, BG, AE and AD (Wei et al., 2010). As more than 95% of circulating recombinant form of HIV in Iran is dedicated to CRF35_AD, and the remainder are the rare cases such as subtype B and CRF01_AE (Jahanbakhsh et al., 2013b), the recombinant antigen in LAg-Avidity covers all circulating subtypes. Still, the peptide antigen in BED-EIA may only cover the rare subtypes in Iran. One of the major drawbacks of serologic assays for HIV incidence estimation is false recent misclassification of individuals with long term HIV infection. To address the issue of false recent misclassification, multi assay algorithms can be applied. This multi assay algorithm may include two serologic assays to increase the sensitivity of the diagnosis and biomarkers like CD4+ T-cell count and viral load to exclude the individuals whose progressed disease may lead to misclassification. Applying two serologic tests targeting the two different HIV antigens will increase the performance of the algorithms. The proposed assay in this article, due to the use of different antigen than other assays, may be a good option for employing this method in diagnostic multi assay algorithms. In this study, we could only evaluate the specificity of LINT-assay with a small panel of sera including 78 HIV positive samples. Appropriate characterization of the assay requires use of large number of ART naïve patients to be able to make a statement about FRR. Further refining the test, evaluation of the sensitivity and mean duration of recent infection require the access to specimen of recent HIV infected individuals with known duration of infection, which is the main shortcoming of our study. On the other hand, FRR among ART patients is not a fixed number; treatment will affect recency misclassification at varying levels depending on timing of initiation and duration of ART (Laeyendecker et al., 2012). Therefore ART related misclassification is an important but separate question which can be dealt with once the assay is characterized with respect to MDRI and FRR, using large numbers of appropriate specimens. We plan on further refining the test and using a multi assay algorithm to improve its predictive value in detecting recent HIV infection.