Table 1

Immunoassay Method	P31 Positive	P66 Positive	P31 Negative	P66 Negative
Indirect	355	351	28	2
Sandwich	355	351	28	2

Table 1: Screening of 385 HIV Seropositive for Antibodies to p31 and p66 with Two Immunoassay Methods

Of 385 HIV-positive sera, 383 (99.4%) were anti-P31 positive. Among these, 355 samples had O.D. >3.0, while 28 had O.D. between cut-off and 3.0, indicating early antibody response or low avidity and for anti-p66 368/385 (96%) were positive antibodies. Seventeen samples were negative in both methods, while three were positive only by sandwich ELISA, suggesting early antibody development. Correlation between P31 and P66 responses supports their use as staging markers.

Table 2

Stage	RNA (+)	p24 Antigen	ELISA Env (+)	WB Env	ELISA Pol	WB Pol	ELISA Pol
		(+)		(+)	[p31(+)/P66(-)]	[p31(+)/P66(-)]	[p31(+)/P66(+)
I	Yes	No	No	No	No	No	No
II	Yes	Yes	No	No	No	No	No
III	Yes	Yes	Yes	Yes	No	No	No
IV	Yes	Yes	Yes	Yes	No	No	No
V	Yes	Yes	Yes	Yes	Yes	No	No
VI-a	Yes	Yes	Yes	Yes	Yes	Yes	No
VI-b	Yes	Yes	Yes	Yes	Yes	Yes	Yes

Table 2: Improved Fiebig Stage Classifications for Sub-Stages of HIV Primary Infection leading to a seven-stage model

Stage I: HIV RNA positive only

Stage II: HIV RNA + p24 antigen positive

Stage III: HIV RNA, p24 antigen, and Env-specific ELISA antibodies positive

Stage IV: HIV RNA, p24 antigen, Env-positive by ELISA and WB

Stage V: HIV RNA, p24 antigen, Env-positive by ELISA and WB, but negative for pol antibodies (P31, P66)

Stage VI-a: WB positive for one pol antigen (typically P31)

Stage VI-b: Full WB reactivity with P31 band present; ELISA positive for both P31 and P66

Tables at a glance

Table 1

Table 2

Figures at a glance

Figure 1

FIGURE 1

Figure 1: Laboratory staging of HIV infection. The first four Fiebig stages are characterised by the subsequent detection of viral RNA, p24 antigen, antibodies and a semi-positive western blot (some, but not all bands are present). (12).