Development of Improved Simian/Human Immunodeficiency Viruses of HIV-1 Clades AE, B and C
Gupte, Siddhant Sachin
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CitationGupte, Siddhant Sachin. 2018. Development of Improved Simian/Human Immunodeficiency Viruses of HIV-1 Clades AE, B and C. Master's thesis, Harvard Medical School.
AbstractThe absence of an animal model that recapitulates HIV infection and AIDS progression limits in vivo analysis of therapies and vaccines aimed at targeting the HIV envelope. Thus, Simian/Human Immunodeficiency Viruses (SHIVs), chimeras of a SIV backbone and a HIV envelope, were generated to challenge rhesus macaques. However, current SHIVs fail to cause chronic infections in monkeys due to inefficient binding to rhesus CD4 T cells. Previous studies have demonstrated that position 375 on the HIV envelope lies in the CD4 binding pocket and interacts with the phenylalanine at position 43 of the CD4 T cell. Furthermore, SIV/HIV envelope sequence comparisons revealed that SIV had bulkier and/or more hydrophobic amino acids at position 375 that helped improve binding to rhesus CD4 T cells. Using this rationale, we developed variants of SHIV-SF162P3, SHIV-AE16 and SHIV-325c, and mutated the wild type amino acid at position 375 to methionine, histidine (serine for SHIV-AE16), tryptophan, tyrosine and phenylalanine, to enhance binding to CD4 T cells. For SHIV-SF162P3, SHIV-AE16 and SHIV-325c, the modified variants of each virus were pooled and then used to intravenously challenge groups of four rhesus monkeys. The control groups were challenged with the original laboratory challenge stocks of each virus, which have previously been used in non-human primate acquisition studies. Plasma viral load analysis of all four animals challenged with modified SHIV-SF162P3 revealed high titers even up till week 43, while one of the four animals infected with the original virus showed no detectable viral loads at week 43. However, animals infected with modified SHIV-AE16 had lower viral loads than the control group and were nearly undetectable at week 43. Animals infected with modified SHIV-325c attained peak viral loads at week 2 and generally displayed higher viral loads than the control group through week 4. Single genome amplification revealed that the serine (wild type) variant of SHIV-SF162P3 and the histidine (wild type) and tryptophan variants of SHIV-AE16 were the most infectious in vivo. These modified SHIVs, especially SHIV-SF162P3, will be monitored to determine if they establish a chronic infection in rhesus monkeys, which, if successful, will ultimately improve the preclinical evaluation of vaccines and therapies that target the HIV envelope.
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