Determinants in V2C2 region of HIV-1 clade C primary envelopes conferred altered neutralization susceptibilities to IgG1b12 and PG9 monoclonal antibodies in a context-dependent manner.

In the present study by examining pseudoviruses expressing patient chimeric envelopes (Envs) made between an IgG1b12 (b12)-sensitive (2-5.J3) and a b12-resistant (4.J22) HIV-1 clade C envelope, we identified determinants in the V2C2 region that governed susceptibility to b12 monoclonal antibody, but not to other CD4 binding site antibodies. Interestingly, when the V2C2 sequence of the 2-5.J3 Env was transferred to other b12-resistant primary clade C Envs, their susceptibility to b12 varied, indicating that this effect was context dependent. In addition, we identified determinants within the V2 region in the b12-resistant envelope that significantly modulated the neutralization of Env-pseudotyped viruses to PG9/PG16 MAbs. The enhanced neutralization susceptibilities of Envs to b12 and PG9 MAbs were correlated with increased exposure of their corresponding epitopes highlighting vulnerabilities in the V2C2 region that altered Env conformation necessary for the efficient accessibility of b12 and PG9 antibodies.

Single step detection of HIV-1 proviral DNA and housekeeping ß-actin gene from dried blood spots by a monoplex polymerase chain reaction.

There is a growing need for developing a simple, rapid, reliable and cost effective method for detection of HIV-1 for early diagnosis of the infection especially in developing countries and in resource limited settings. A method for simultaneous detection of the HIV-1 p17 gene and the house keeping human ß-actin gene from dried blood spots (DBS) by a monoplex polymerase chain reaction (PCR) is described. Genomic DNA was extracted from 40 HIV-1 positive and 40 HIV-1 negative DBS and used as templates to amplify both the HIV-1 p17 and ß-actin genes simultaneously under the same cycling condition by a single round PCR. This method of detection of HIV-1 may provide a simple, rapid and cost effective alternative in resource limited settings; however, it would require testing a larger number of samples before widespread use.

Unique C2V3 sequence in HIV-1 envelope obtained from broadly neutralizing plasma of a slow progressing patient conferred enhanced virus neutralization.

Broadly neutralizing antibodies to HIV-1 usually develops in chronic infections. Here, we examined the basis of enhanced sensitivity of an env clone amplified from cross neutralizing plasma of an antiretroviral naïve chronically infected Indian patient (ID50 >600-fold higher compared to other autologous env clones). The enhanced autologous neutralization of pseudotyped viruses expressing the sensitive envelope (Env) was associated with increased sensitivity to reagents and monoclonal antibodies targeting distinct sites in Env. Chimeric viruses constructed by swapping fragments of sensitive Env into resistant Env backbone revealed that the presence of unique residues within C2V3 region of gp120 governed increased neutralization. The enhanced virus neutralization was also associated with low CD4 dependence as well as increased binding of Env trimers to IgG1b12 and CD4-IgG2 and was independent of gp120 shedding. Our data highlighted vulnerabilities in the Env obtained from cross neutralizing plasma associated with the exposure of discontinuous neutralizing epitopes and enhanced autologous neutralization. Such information may aid in Env-based vaccine immunogen design.