Catalytic efficiency and vitality of HIV-1 proteases from African viral subtypes

Abstract

The vast majority of HIV-1 infections in Africa are caused by the A and C viral subtypes rather than the B subtype prevalent in the United States and Western Europe. Genomic differences between subtypes give rise to sequence variations in the encoded proteins, including the HIV-1 protease. Because some amino acid polymorphisms occur at sites that have been associated with drug resistance in the B subtype, it is important to assess the effectiveness of protease inhibitors that have been developed against different subtypes. Here we report the enzymatic characterization of HIV-1 proteases with sequences found in drug-naïve Ugandan adults. The A protease used in these studies differs in seven positions (I13V͞E35D͞M36I͞R41K͞R57K͞H69K͞L89M) in relation to the consensus B subtype protease. Another protease containing a subset of these amino acid polymorphisms (M36I͞R41K͞H69K͞L89M), which are found in subtype C and other HIV subtypes, also was studied. Both proteases were found to have similar catalytic constants, kcat, as the B subtype. The C subtype protease displayed lower Km values against two different substrates resulting in a higher (2.4-fold) catalytic efficiency than the B subtype protease. Indinavir, ritonavir, saquinavir, and nelfinavir inhibit the A and C subtype proteases with 2.5-7-fold and 2-4.5-fold weaker Kis than the B subtype. When all factors are taken into consideration it is found that the C subtype protease has the highest vitality (4 -11 higher than the B subtype) whereas the A subtype protease exhibits values ranging between 1.5 and 5. These results point to a higher biochemical fitness of the A and C proteases in the presence of existing inhibitors.

Analysis of HIV-1 CRF_01 A/E Protease Inhibitor Resistance: Structural Determinants for Maintaining Sensitivity and Developing Resistance to Atazanavir

“…Though there is a preference by both proteases for phenylalanine, the differences seen in the Michaelis-Menten constants for all substrates suggest that the natural polymorphisms in AE can influence active site specificity and/or catalytic efficiency. In contrast to the data reported earlier for subtype-C (C) and -A (A) proteases, the AE protease does not show any clear catalytic advantage over B protease (21).…”

Mutation D30N Is Not Preferentially Selected by Human Immunodeficiency Virus Type 1 Subtype C in the Development of Resistance to Nelfinavir

“…Israelis and are unlikely to share adherence patterns suggest an effect of the common baseline mutations rather than of drug taking behavior. (iv) Such an effect of baseline non-subtype-B mutations on efficiency and stability of the enzyme, and hence on resistance development, is supported by biochemical studies in these patients (28,29). Susceptibility assays and RC assays were not designed specifically for subtype C viruses and used a standard subtype-B-based vector.…”

“…Although none of the primary mutations occur as polymorphisms in wild-type HIV-1, several secondary mutations contributing to reduced susceptibility (i.e., M36I and I93L) are found in nearly 100% of subtype C virus from drug-naive patients (5,10). Upon antiretroviral treatment, such differences in baseline polymorphisms among subtypes may result in the evolution of drug resistance along distinct mutational pathways, or in differences in the incidence of these specific pathways (1,4,9,12,16,25,28,29). These genetic differences may be clinically relevant when considering long-term treatment strategies for patients infected with different subtypes.…”

Zero prevalence of primary drug resistance-associated mutations to protease inhibitors in HIV-1 drug-naive patients in and around Aligarh, India

“…Ten (19.2%) patients showed atypical T74A/S mutations that may be responsible for supplementing resistance to ATV, FSV, IDV, NFV, and saquinavir (SQV). The presence of K14R mutant may slightly increase resistance to darunavir (DRV) [27]. T74S mutation alone may reduce NFV susceptibility [28].…”