HIV-1 Strain and Primary Drug Resistance in Canada
Surveillance Report to June 30, 2002

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Appendix 1

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 antiretroviral drug.

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

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

Genotypic resistance: presence of mutations to nucleotides that increase resistance of HIV to one or more antiretroviral 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.

Major mutation: mutation in the viral nucleotide sequence, which, in and of itself, is strongly associated with conferring increased resistance of HIV to an antiretroviral drug.

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

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% (IC 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 resistance: resistance of HIV to antiretroviral 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 resistance: increased resistance of HIV to drugs, seen among individuals already receiving treatment (presumably due to 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.

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* Some definitions are adapted from the HIV and AIDS in Canada Surveillance Report to December 31, 2000,
http://www.phac-aspc.gc.ca/publicat/aids-sida/haic-vsac00/index.html and from the International Consultation on Monitoring the Emergence of Antiretroviral Resistance sponsored by WHO, UNAIDS and ISS (October 2000)
http://www.who.int/csr/resources/publications/drugresist/WHO_CDS_CSR_DRS_2001_11/en/

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