HIV-1 Strain and Primary Drug Resistance in Canada

Surveillance Report to June 30, 2001

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Appendix 1¹

Glossary of terms

Cross-resistance: resistance selected by one drug which, in turn, confers resistance to one or more drugs not included in the current treatment

DNA: deoxyribonucleic acid, the genetic material of a cell

Drug resistance: decreased susceptibility to a drug

Drug resistance mutation: a change in amino acid associated with increased resistance of HIV to an anti-retroviral drug

Gene: a segment of DNA coding for a particular protein or protein sub-unit

Genotype: specific sequence of nucleotides that determines the genes of HIV-1

Genotypic resistance: presence of mutations to nucleotides that increase resistance of HIV to one or more anti-retroviral drugs

Genotypic tests: conducted to determine the presence of mutations in the nucleotide sequence of the viral genome

HIV: Human immunodeficiency virus

Incidence: the number of new occurrences of a disease in a given population during a specified period of time

Multi-drug resistance: increased resistance of HIV to more than one class of drugs

Mutation: genetic change in the viral nucleotide sequence

Nucleotide: a monomeric unit consisting of a sugar, phosphate, and nitrogenous base

PCR: polymerase chain reaction, a molecular technique used to amplify nucleotide sequences

Phenotype: characteristics and growth properties of HIV-1

Phenotypic resistance: when four or more times the amount of drug is required to inhibit viral growth by 50% (inhibitory concentration 50)

Phenotypic tests: used to determine the susceptibility of a virus to drug in a virus culture assay

Prevalence: the number people with the disease in a given population who are alive during a specified period of time

Primary mutation: mutation in the viral nucleotide sequence that, in and of itself, is strongly associated with conferring increased resistance of HIV to an anti-retroviral drug

Primary resistance: increased resistance of HIV to anti-retroviral drugs seen in individuals who have never before received treatment and so, presumably, have been infected with drug-resistant virus

Protease: an enzyme that breaks down proteins to their subunits or component peptides

Recombinant: HIV-1 containing a sequence corresponding to a mixture of more than one subtype in the envelope gene

Reverse transcriptase: an enzyme that is unique to all retroviruses. It reads the genetic information of the retrovirus, which is RNA, and makes a DNA copy.

RNA: ribonucleic acid, a polymer of nucleotides involved in protein synthesis

RT-PCR: PCR using the enzyme reverse transcriptase (RT), a molecular technique used to amplify RNA sequence into DNA

Secondary mutation: mutation in the viral nucleotide sequence, which, in combination with other mutations, confers increased resistance of HIV to a drug

Secondary resistance: increased resistance of HIV to drugs seen in individuals already receiving treatment (presumably a result of treatment failure)

Subtype: also referred to as clade, a group of related HIV variants classified according to degree of genetic similarity

Wild type virus: the most commonly occurring form of HIV-1

1. Some definitions are adapted from the HIV and AIDS in Canada surveillance report  to December 31, 2000 and from the International Consultation on Monitoring the Emergence of Antiretroviral Resistance sponsored by WHO, UNAIDS and ISS (October, 2000).

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